全文获取类型
收费全文 | 211篇 |
免费 | 8篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 21篇 |
废物处理 | 10篇 |
环保管理 | 46篇 |
综合类 | 23篇 |
基础理论 | 65篇 |
污染及防治 | 43篇 |
评价与监测 | 13篇 |
社会与环境 | 2篇 |
灾害及防治 | 2篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 10篇 |
2019年 | 1篇 |
2017年 | 4篇 |
2016年 | 5篇 |
2015年 | 4篇 |
2014年 | 3篇 |
2013年 | 19篇 |
2012年 | 8篇 |
2011年 | 11篇 |
2010年 | 10篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 16篇 |
2006年 | 8篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 7篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 5篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1990年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 5篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有225条查询结果,搜索用时 15 毫秒
191.
Graph theory as a proxy for spatially explicit population models in conservation planning. 总被引:9,自引:0,他引:9
Spatially explicit population models (SEPMs) are often considered the best way to predict and manage species distributions in spatially heterogeneous landscapes. However, they are computationally intensive and require extensive knowledge of species' biology and behavior, limiting their application in many cases. An alternative to SEPMs is graph theory, which has minimal data requirements and efficient algorithms. Although only recently introduced to landscape ecology, graph theory is well suited to ecological applications concerned with connectivity or movement. This paper compares the performance of graph theory to a SEPM in selecting important habitat patches for Wood Thrush (Hylocichla mustelina) conservation. We use both models to identify habitat patches that act as population sources and persistent patches and also use graph theory to identify patches that act as stepping stones for dispersal. Correlations of patch rankings were very high between the two models. In addition, graph theory offers the ability to identify patches that are very important to habitat connectivity and thus long-term population persistence across the landscape. We show that graph theory makes very similar predictions in most cases and in other cases offers insight not available from the SEPM, and we conclude that graph theory is a suitable and possibly preferable alternative to SEPMs for species conservation in heterogeneous landscapes. 相似文献
192.
We studied the effects of grazing by two species of sea urchins on two species of kelp (Macrocystis pyrifera and Pterygophora californica) in the San Onofre kelp bed in southern California from 1978 through 1981. Both red sea urchins, Strongylocentrotus franciscanus, and white sea urchins, Lytechinus anamesus, were abundant and lived in aggregations. The purple sea urchin (S. purpuratus) was rare at the study site and was not studied. The aggregations of red urchins were either relatively small and stationary (for over 3 yr) or relatively large and motile (advancing at about 2 m mo–1). Both stationary and moving aggregations were observed at the same time, and within 100 m of one another. Stationary aggregations of red urchins probably subsisted mainly on drift kelp and had no effect on kelp recruitment or on adult kelp abundance. In contrast, red sea urchins in large, motile aggregations or fronts ate almost all the macroalgae in their path. The condition of their gonalds indicated that red urchins in fronts were starved relative to red urchins in the small, stationary aggregations. Large, motile aggregations developed after 2 yr of declining kelp abundance (probably due largely to storms). We propose that a scarcity of drift algae for food results in a change in the behavior pattern of the red urchins and thus leads to the formation of large, motile aggregations. The aggregations of white urchins, which occurred along the offshore margin of the kelp bed, were large, but relatively stationary. The white urchins rarely ate adult kelps, but grazed extensively on early developmental stages of kelps and evidently prevented seaward expansion of the bed. The spatial distribution of both types of red urchin aggregations appeared to be unrelated to predation pressure from fishes or lobsters.Please address all requests for reprints to the senior author at his present address. 相似文献
193.
随着人类环境意识的增强,绿化意识正向人类生活的各个领域渗透:政治经济的绿化-绿色和平组织的成立,农业生产的绿化-生态农业的兴起,工业的绿化-清洁生产的召唤,人类生活的绿化-绿色食品的发展,思维方式的绿化-绿色消费热潮方兴未艾。同时绿化意识的人类发出回归大自然、保持生态平衡的呼唤。 相似文献
194.
McFarland MJ Palmer GR Kordich MM Pollet DA Jensen JA Lindsay MH 《Journal of the Air & Waste Management Association (1995)》2005,55(8):1111-1121
The U.S. Department of Defense approved activities conducted at the Utah Test and Training Range (UTTR) include both operational readiness test firing of intercontinental ballistic missile motors as well as the destruction of obsolete or otherwise unusable intercontinental ballistic missile motors through open burn/open detonation (OB/ OD). Within the Utah Division of Air Quality, these activities have been identified as having the potential to generate unacceptable noise levels, as well as significant amounts of hazardous air pollutants. Hill Air Force Base, UT, has completed a series of field tests at the UTTR in which sound-monitoring surveillance of OB/OD activities was conducted to validate the Sound Intensity Prediction System (SIPS) model. Using results generated by the SIPS model to support the decision to detonate, the UTTR successfully disposed of missile motors having an aggregate net explosive weight (NEW) of 56,500 lbs without generating adverse noise levels within populated areas. These results suggest that, under appropriate conditions, missile motors of even larger NEW may be detonated without exceeding regulatory noise limits. In conjunction with collecting noise monitoring data, air quality data was collected to support the development of air emission factors for both static missile motor firings and OB/OD activities. Through the installation of 15 ground-based air samplers, the generation of combustion fixed gases, hazardous air pollutants, and chlorides were monitored during the 56,500-lb NEW detonation event. Comparison of field measurements to predictions generated from the U.S. Navy's energetic combustion pollutant formation model, POLU4WN, indicated that, as the detonation fireball expanded from ground zero, organic compounds as well as carbon monoxide continued to oxidize as the hot gases reacted with ambient air. Hazardous air pollutant analysis of air samplers confirmed the presence of chloromethane, benzene, toluene, 1,2-propadiene, and 2-methyl-l-propene, whereas the absence of hydrogen chloride gas suggested that free chlorine is not generated during the combustion process. 相似文献
195.
Nine tower datasets over grassland, brush rangeland, snow covered plain, the ocean, three different pine forests, an aspen
forest and an urban site, are used to document the scale-dependence of the cross-wind velocity variance in the stable boundary
layer. The turbulence velocity variance scales with the surface momentum flux, as reported in previous studies. Such scaling
removes the stability dependence of the variance at a given site, and also removes most of the differences between sites.
The scaling is more effective with use of a record-dependent averaging time for defining the turbulent fluctuations. The variable
averaging time is the timescale associated with the gap region in the heat flux multiresolution cospectra.
On scales larger than turbulence and less than a few hours (mesoscale), variations in the cross-wind velocity variance at
a given site are not related to local variables such as the friction velocity. Possible exceptions include suppression of
turbulence and mesoscale motions in well-defined drainage flows and enhancement of turbulence and mesoscale motions in stronger
winds downstream of a ridge. Larger mesoscale variance is associated with complex terrain and forested sites compared to the
more homogeneous sites in flat terrain with short or no vegetation. These differences between sites are related to the absence
of a gap region in the velocity spectra at the complex terrain and forested sites. The observed probability distribution functions
of the total variance and the mesoscale variance are documented for different averaging times, stability classes and site
characteristics. 相似文献
196.
Brian Miller Christen Wemmer Dean Biggins Richard Reading 《Environmental management》1990,14(6):763-769
Prairie dogs (Cynomys spp.) have been poisoned throughout this century because of grazing competition with livestock. Recent evidence showed these
early claims were exaggerated, but animal control was already entrenched in government policy. As a result, ongoing government
subsidized poisoning has reduced prairie dogs to about 2% of their former distribution. The reduction of prairie dogs diminished
species diversity in the arid grasslands of North America, including the potential extinction of the black-footed ferret (Mustela nigripes). Cost-benefit analysis revealed that poisoning costs more than any grazing benefits accrued. This analysis did not consider
the long-term costs of reversing ecosystem degradation, the intangible value of biological diversity as a public benefit,
or the depletion of biotic resources as a loss of actual or potential wealth. The government presently finances the poisoning
policy and the preservation of endangered species like the black-footed ferret, two apparently conflicting programs. We, therefore,
propose an integrated management plan that considers both interests. We propose that federal monies allocated to the poisoning
program be converted into a rebate for ranchers who manage livestock while preserving the prairie dog community. This would
redirect funds and personnel already allocated to prairie dog eradication to an incentive for ranchers who manage for livestock
and wildlife. Livestock interests and grassland biotic diversity would both benefit. 相似文献
197.
Characterization and spatial distribution of heavy metals in sediment from Cedar and Ortega rivers subbasin 总被引:1,自引:0,他引:1
Ouyang Y Higman J Thompson J O'Toole T Campbell D 《Journal of contaminant hydrology》2002,54(1-2):19-35
The Cedar and Ortega rivers subbasin is a complex environment where both natural and anthropogenic processes influence the characteristics and distributions of sediments and contaminants, which in turn is of importance for maintenance, dredging and pollution control. This study investigated the characteristics and spatial distribution of heavy metals, including lead (Pb), copper (Cu), zinc (Zn) and cadmium (Cd), from sediments in the subbasin using field measurements and three-dimensional kriging estimates. Sediment samples collected from three sampling depth intervals (i.e., 0-0.10, 0.11-0.56 and 0.57-1.88 m) in 58 locations showed that concentrations of Pb ranged from 4.47 to 420.00 mg/kg dry weight, Cu from 2.30 to 107.00 mg/kg dry weight, Zn from 9.75 to 2,050.00 mg/kg dry weight and Cd from 0.07 to 3.83 mg/kg dry weight. Kriging estimates showed that Pb, Cu and Cd concentrations decreased significantly from the sediment depth of 0.10 to 1.5 m, whereas Zn concentrations were still enriched at 1.5 m. It further revealed that the Cedar River area was a potential source area since it was more contaminated than the rest of the subbasin. Comparison of aluminum (Al)-normalized metal concentrations indicated that most of the metals within the top two intervals (0-0.56 m) had concentrations exceeding the background levels by factors of 2-10. A three-dimensional view of the metal contamination plumes showed that all of the heavy metals, with concentrations exceeding the threshold effect level (TEL) that could pose a threat to the health of aquatic organisms, were primarily located above the sediment depth of 1.5 m. 相似文献
198.
Water, Air, &; Soil Pollution: Focus - 相似文献
199.
Alan G. McElligott Martin P. Gammell Hilda C. Harty Dean R. Paini Desmond T. Murphy James T. Walsh Thomas J. Hayden 《Behavioral ecology and sociobiology》2001,49(4):266-272
Sexual size dimorphism may evolve as a result of both natural and sexual selection. In polygynous mammals, the main factor resulting in the evolution of large body size in males is the advantage conferred during competition for mates. In this study, we examined whether sexual selection acts on body size in mature fallow bucks (Dama dama) by examining how the following traits are inter-related: age, body (skeletal) size, body mass, prerut dominance rank, rut dominance rank and mating success. This is the first study to examine how all these factors are together related to the mating success of a large sexually dimorphic and polygynous mammal. We found that male mating success was directly related to body size, but not to body mass. However body mass was related to prerut dominance rank which was in turn strongly related to rut dominance rank, and thus there was an indirect relationship between mating success and body mass. Rut dominance rank was the variable most strongly related to mating success. Mating success among mature males was unrelated to age. We conclude that larger mature fallow bucks have advantages over other males when competing for matings, and sexual selection therefore continues to act on sexual size dimorphism in this species. Heavier fallow bucks also have advantages, but these are mediated through the dominance ranks attained by males before the rut. 相似文献
200.
Estimation of daily intake of potentially toxic elements from urban street dust and the role of oral bioaccessibility testing 总被引:2,自引:0,他引:2
The pseudo-total and oral bioaccessible concentration of six potentially toxic elements (PTEs) in urban street dust was investigated. Typical pseudo-total concentrations across the sampling sites ranged from 4.4 to 8.6 mg kg−1 for As, 0.2-3.6 mg kg−1 for Cd, 25-217 mg kg−1 for Cu, 14-46 mg kg−1 for Ni, 70-4261 mg kg−1 for Pb, and, 111-652 mg kg−1 for Zn. This data compared favourably with other urban street dust samples collected and analysed in a variety of cities globally; the exception was the high level of Pb determined in a specific sample in this study. The oral bioaccessibility of PTEs in street dust is also assessed using in vitro gastrointestinal extraction (Unified Bioaccessibility Method, UBM). Based on a worst case scenario the oral bioaccessibility data estimated that Cd and Zn had the highest % bioaccessible fractions (median >45%) while the other PTEs i.e. As, Cu, Ni and Pb had lower % bioaccessible fractions (median <35%). The pseudo-total and bioaccessible concentrations of PTEs in the samples has been compared to estimated tolerable daily intake values based on unintentional soil/dust consumption. Cadmium, Cu and Ni are well within the oral tolerable daily intake rates. With respect to As and Pb, only the latter exceeds the TDIoral if we model ingestion rate based on atmospheric ‘dustiness’ rather than the US EPA (2008) unintentional soil/dust consumption rate of 100 mg d−1. We consider it unlikely that even a child with pica tendencies would ingest as much as 100 mg soil/dust during a daily visit to the city centre, and in particular to the sites with elevated Pb concentrations observed in this study. 相似文献