全文获取类型
收费全文 | 345篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
安全科学 | 8篇 |
废物处理 | 19篇 |
环保管理 | 97篇 |
综合类 | 16篇 |
基础理论 | 100篇 |
污染及防治 | 70篇 |
评价与监测 | 29篇 |
社会与环境 | 15篇 |
灾害及防治 | 2篇 |
出版年
2023年 | 3篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 6篇 |
2018年 | 9篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 13篇 |
2014年 | 11篇 |
2013年 | 24篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 12篇 |
2009年 | 18篇 |
2008年 | 20篇 |
2007年 | 28篇 |
2006年 | 12篇 |
2005年 | 14篇 |
2004年 | 13篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 10篇 |
2000年 | 4篇 |
1999年 | 5篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1988年 | 2篇 |
1987年 | 4篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1975年 | 2篇 |
1974年 | 3篇 |
1972年 | 3篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1968年 | 1篇 |
1967年 | 2篇 |
1957年 | 1篇 |
排序方式: 共有356条查询结果,搜索用时 31 毫秒
271.
The evolution of empty nuptial gifts in a dance fly, Empis snoddyi (Diptera: Empididae): bigger isn't always better 总被引:2,自引:0,他引:2
Jennifer A. Sadowski Allen J. Moore Edmund D. Brodie III 《Behavioral ecology and sociobiology》1999,45(3-4):161-166
Adaptive female choice is thought to have led to the evolution of nutritionally valuable nuptial gifts in many insect species.
However, in several dance fly species, males offer and females accept “empty gifts” with no nutritional value. In the species
studied here, Empis snoddyi Steyskal, males produce empty balloons comprised of hundreds of silk bubbles and form mating swarms that females approach
to investigate males. Males within the swarm engage in agonistic interactions. The empty balloon has been hypothesized to
be an indicator of male condition such that males with larger balloons are predicted to have higher mating success and be
more successful in male-male interactions than males with smaller balloons. We examined the role of male body size and balloon
size in the context of intersexual and intrasexual selection. We found that neither male body size nor balloon size affected
the outcome of pairwise male-male interactions. Using multiple-regression techniques, we found significant linear selection
for increasing male body size and decreasing balloon size associated with mating success, a surprising result given a positive
relationship between male body size and balloon size. A visualization of selection showed the highest peak of male mating
success for larger males with intermediate-size balloons. These results can be explained by a trade-off between long-range
attraction of females using large balloons and close-range attraction of females via improved flying efficiency associated
with smaller balloons. Both male body size and balloon size are important components in determining male mating success; however,
the empty balloon does not appear to play a typical role as a sexually selected ornament.
Received: 29 December 1997 / Accepted after revision: 7 October 1998 相似文献
272.
Controls on vegetation structure in Southwestern ponderosa pine forests, 1941 and 2004 总被引:2,自引:0,他引:2
Long-term studies can broaden our ecological understanding and are particularly important when examining contingent effects that involve changes to dominance by long-lived species. Such a change occurred during the last century in Southwestern (USA) ponderosa pine (Pinus ponderosa) forests. We used five livestock grazing exclosures established in 1912 to quantify vegetation structure in 1941 and 2004. Our objectives were to (1) assess the effects of historical livestock grazing on overstory structure and age distribution, (2) assess the effects of recent livestock grazing and overstory on understory vegetation, and (3) quantify and explain changes in understory vegetation between 1941 and 2004. In 1941, canopy cover of tree regeneration was significantly higher inside exclosures. In 2004, total tree canopy cover was twice as high, density was three times higher, trees were smaller, and total basal area was 40% higher inside exclosures. Understory species density, herbaceous plant density, and herbaceous cover were negatively correlated with overstory vegetation in both years. Most understory variables did not differ between grazing treatments in 1941 but were lower inside exclosures in 2004. Differences between grazing treatments disappeared once overstory effects were accounted for, indicating that they were due to the differential overstory response to historical livestock grazing practices. Between 1941 and 2004, species density declined by 34%, herbaceous plant density by 37%, shrub cover by 69%, total herbaceous cover by 59%, graminoid cover by 39%, and forb cover by 82%. However, these variables did not differ between grazing treatments or years once overstory effects were accounted for, indicating that the declines were driven by the increased dominance of the overstory during this period. Our results demonstrate that historical livestock grazing practices are an aspect of land-use history that can affect ecosystem development. Grazing history must be considered when extrapolating results from one site to another. In addition, the understory vegetation was more strongly controlled by the ponderosa pine overstory than by recent livestock grazing or by temporal dynamics, indicating that overstory effects must be accounted for when examining understory responses in this ecosystem. 相似文献
273.
Aerosol Particle Processing and Removal by Fogs: Observations in Chemically Heterogeneous Central California Radiation Fogs 总被引:4,自引:0,他引:4
Collett Jeffrey L. Sherman D. Eli Moore Katharine F. Hannigan Michael P. Lee Taehyoung 《Water, Air, & Soil Pollution: Focus》2001,1(5-6):303-312
Fog composition and deposition fluxes of fog waterand fog solutes were measured in six radiation fogevents in San Joaquin Valley, California duringwinter 1998/1999. Measurements made at 2 hrintervals with 0.30 m2 and 0.06 m2 Teflondeposition plates yielded excellent reproducibility(relative standard deviations of 3.8–6.0%) forwater, nitrate, sulfate and ammonium. Water fluxesmeasured at 5 min intervals with a recordingbalance agreed well with the deposition platemeasurements before 8:00 AM. After 8:00 AMevaporation proved problematic. The averagedeposition velocity from the study for fog nitrate(3.8 cm s-1) was less than those for fogsulfate (5.1 cm s-1) and ammonium (6.7 cms-1). All three species generally exhibitedsmaller deposition velocities than fog water. Thespecies dependent trend in deposition velocitieswas consistent with preferential enrichment ofthese species in small fog drops (nitrate > sulfate> ammonium). 相似文献
274.
Dredging impact on an urbanized Florida bayou: effects on benthos and algal-periphyton. 总被引:8,自引:0,他引:8
M A Lewis D E Weber R S Stanley J C Moore 《Environmental pollution (Barking, Essex : 1987)》2001,115(2):161-171
Environmental effects of dredging events have been uncommonly reported for shallow, residential estuaries characteristic of the Gulf of Mexico region. The objective of this study was to determine the impact of hydraulic dredging on an urbanized estuary. Physicochemical quality, benthic community composition, whole sediment toxicity, periphytic algal community composition and trace metal tissue quality were determined prior to and after dredging. The effects on surface water pH, dissolved oxygen, and temperature were negligible but photosynthetically active radiation was decreased at several stations. Dredging significantly reduced benthic diversity and density (P < 0.05). However, the sediments were not acutely toxic to the epibenthic, Americamysis bahia (formerly Mysidopsis bahia); survival averaged 93% (post-dredging) and to 98% (pre-dredging). There were several post-dredging taxonomic structural changes in the diatom-dominated, periphyton community but differences in mean density and three diversity indices were not significant. Trace metal concentration in periphyton after dredging were reduced from an average of 4-65% and significantly for mercury, zinc and chromium in several areas. It was concluded that the environmental impact of small-scale dredging events in urbanized near-coastal areas, based on the selected parameters, are likely to be localized and of short-term environmental consequence. The choice of the target biota, response parameters and chemical analysis are important considerations in the environmental impact assessment of these periodic episodic events. 相似文献
275.
The anions chloride, sulfate and nitrate in nearly 500 pairs of ice core samples from the same depth were determined in a 121 m long ice core from Svalbard. The analyses were performed separately using an ion chromatograph with Dionex AS9 and AS15 columns with Na(2)CO(3) and NaOH eluents. Results showed a small (5-6 microg l(-1)) but statistically significant difference in mean concentrations for chloride and sulfate but not for nitrate. 2% of the data indicate real differences in concentrations across the ice core. Despite these differences ion information in ice core layers are comparable for ice core paleoclimate and environmental studies even though analyses are made using two different procedures. 相似文献
276.
Richard B. Moore Kenneth Belitz Joseph Ayotte Terri L. Arnold Laura Hayes Jennifer B. Sharpe Jeffrey J. Starn 《Journal of the American Water Resources Association》2023,59(1):127-145
Two radioactive elements, uranium (U) and radon (Rn), which are of potential concern in New Hampshire (NH) groundwater, are investigated. Exceedance probability maps are tools to highlight locations where the concentrations of undesirable substances in the groundwater may be elevated. Two forms of statistical analysis are used to create exceedance probability maps for U and Rn in NH groundwater. The first, Boosted Regression Tree (BRT), was selected for estimating U exceedance values. It computes exceedance values directly using the Bernoulli distribution function. The second method of statistical analysis used for Rn to determine exceedance probabilities is ordinary least squares (OLS) regression. In the process of determining exceedance probabilities for U and Rn, the utility of a new dataset is investigated. That new predictor dataset is the Multi-Order Hydrologic Position (MOHP) dataset. MOHP raster datasets have been produced nationally for the conterminous United States at a 30-m resolution. The concept behind MOHP is that, for any given point on the earth's surface, there is the potential for a longer groundwater flow path as one goes deeper beneath the land surface. MOHP predictors were tested in both models. Three MOHP predictors were found useful in the BRT model and two in the OLS model. MOHP data were found useful as predictors along with other site characteristics in predicting U and Rn exceedance probabilities in New Hampshire groundwater. 相似文献
277.
Macroalgal fields are a feature of the shallow tropical benthos, yet their importance for coral reef fish population dynamics remains poorly understood. The abundance of fish recruits was recorded using underwater visual census at six macroalgal and 11 coral reef sites in the Montebello and Barrow Islands. Surveys identified 6,935 individual recruit fish from 105 species, 54 genera and 20 families. Of these, 1,401 recruits from 48 species, 31 genera and 14 families were observed in macroalgal sites. Sixteen of the 105 recruit species (15.2 %) were observed exclusively at macroalgal sites. Forty-two (87.5 %) of these species have been observed as adults on adjacent coral reefs. Species composition of fish recruits differed significantly between the two habitats. Corallivore, small omnivore and zooplanktivore recruits had significantly higher numbers in the coral sites, while the results clearly demonstrate that juveniles, within the genera Lethrinus and Choerodon, as well as large algal croppers, are predominantly found at macroalgal (74–100 %) rather than coral-dominated sites. High-canopy macroalgae cover was positively correlated with abundance of these taxa, particularly Lethrinids (r 2 = 0.40). This study is the first to highlight the important attributes of tropical macroalgal fields and suggests that they have a similar role to seagrass meadows as essential juvenile habitat, thus warranting greater attention in conservation planning and ecological studies. 相似文献
278.
Colin S. Brent Clint A. Penick Beth Trobaugh Dani Moore Jürgen Liebig 《Chemoecology》2016,26(5):195-203
Establishment and maintenance of the reproductive division of labor within social insect colonies relies on clear communication between nestmates. Fertile members convey their status to prevent others from becoming reproductively active. Recent findings in some basal termites indicate that cuticular hydrocarbon profiles may indicate reproductive state, but there is little evidence to show a direct link between reproductive status and hydrocarbon production—a prerequisite for an “honest” fertility signal. Here, we report that the putative signaling mechanism is influenced by juvenile hormone (JH), a primary regulator of gonadal development and activity in insects. Topical application of a JH-analog (pyriproxyfen) to reproductively inactive alates of the basal dampwood termite Zootermopsis nevadensis induced both females and males to express significantly more of a reproductive-specific hydrocarbon (6,9,17-tritriacontatriene). However, the JH-analog did not significantly enhance gonadal development or activity in treated termites beyond what is usually observed in maturing alates released from the inhibitory stimuli of their natal nest. These results suggest that a rise in JH following disinhibition drives the expression of reproductive-specific hydrocarbons, but that an individual’s hydrocarbon profile is not directly linked to its gonadal state. Rather than directly driving the expression of reproductive-specific hydrocarbons, the gonads may act indirectly through their influence on circulating JH. 相似文献
279.
Characterizing dry weather conditions in urban Municipal Separate Storm Sewer Systems (MS4s), and then prioritizing and addressing problems due to urban pollutants, is a daunting challenge. The size and complexity of most MS4s and the ephemeral nature of many dry weather problems hamper efforts to identify and eliminate pollutant sources, and to track trends in condition. As a result, assessing overall program progress has proven difficult. We describe a hybrid dry weather urban monitoring design from southern California that combines probabilistic and targeted sampling to rigorously identify and prioritize problems and track program progress. Data from probabilistic sites define the urban background and establish tolerance intervals, which identify sites that persistently exceed the overall urban background. Targeted sites focus on locations where nearby activities and/or past history suggest that pollutant levels will be elevated. Embedding targeted monitoring within a probabilistic design enables data from targeted sites to be interpreted in a more meaningful regional context. Data from all sites are also used to construct site- and pollutant-specific control charts. These charts quickly identify instances where a site's behavior significantly changes, compared to its past behavior, suggesting an active source in the upstream drainage area. The hybrid design, and the use of formal statistical tools (tolerance intervals and control charts), permit the program to systematically prioritize problematic sites, compare conditions to the regional urban background, and track trends over time. In addition, the program's design allows several measures of program progress to be defined and thus consistently followed over time. Such hybrid designs can provide substantial advantages compared to more traditional monitoring approaches. 相似文献
280.
DeLorenzo ME Thompson B Cooper E Moore J Fulton MH 《Environmental monitoring and assessment》2012,184(1):343-359
Stormwater ponds are commonly used in residential and commercial areas to control flooding. The accumulation of urban contaminants
in stormwater ponds can lead to water-quality problems including nutrient enrichment, chemical contamination, and bacterial
contamination. This study presents 5 years of monitoring data assessing water quality of a residential subdivision pond and
adjacent tidal creek in coastal South Carolina, USA. The stormwater pond is eutrophic, as described by elevated concentrations
of chlorophyll and phosphorus, and experiences periodic cyanobacterial blooms. A maximum monthly average chlorophyll concentration
of 318.75 μg/L was measured in the stormwater pond and 227.63 μg/L in the tidal creek. Fecal coliform bacteria (FCB) levels
were measured in both the pond and the tidal creek that exceeded health and safety standards for safe recreational use. A
maximum monthly average FCB level of 1,247 CFU/100 mL was measured in the stormwater pond and 12,850 CFU/100 mL in the tidal
creek. In addition, the presence of antibiotic resistant bacteria and pathogenic bacteria were detected. Low concentrations
of herbicides (atrazine and 2,4-D), a fungicide (chlorothalonil), and insecticides (pyrethroids and imidacloprid) were measured. Seasonal trends were identified,
with the winter months having the lowest concentrations of chlorophyll and FCB. Statistical differences between the stormwater
pond and the tidal creek were also noted within seasons. The tidal creek had higher FCB levels than the stormwater pond in
the spring and summer, whereas the stormwater pond had higher chlorophyll levels than the tidal creek in the summer and fall
seasons. Chlorophyll and FCB levels in the stormwater pond were significantly correlated with monthly average temperature
and total rainfall. Pesticide concentrations were also significantly correlated with temperature and rainfall. Pesticide concentrations
in the stormwater pond were significantly correlated with pesticide concentrations in the adjacent tidal creek. Chlorophyll
and FCB levels in the tidal creek, however, were not significantly correlated with levels in the pond. While stormwater ponds
are beneficial in controlling flooding, they may pose environmental and human health risks due to biological and chemical
contamination. Management to reduce residential runoff may improve water quality in coastal stormwater ponds and their adjacent
estuarine ecosystems. 相似文献