全文获取类型
收费全文 | 740篇 |
免费 | 16篇 |
国内免费 | 7篇 |
专业分类
安全科学 | 27篇 |
废物处理 | 30篇 |
环保管理 | 173篇 |
综合类 | 86篇 |
基础理论 | 171篇 |
污染及防治 | 168篇 |
评价与监测 | 51篇 |
社会与环境 | 51篇 |
灾害及防治 | 6篇 |
出版年
2022年 | 7篇 |
2021年 | 14篇 |
2020年 | 11篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 18篇 |
2015年 | 20篇 |
2014年 | 16篇 |
2013年 | 82篇 |
2012年 | 30篇 |
2011年 | 42篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 41篇 |
2007年 | 48篇 |
2006年 | 35篇 |
2005年 | 18篇 |
2004年 | 19篇 |
2003年 | 38篇 |
2002年 | 24篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 9篇 |
1995年 | 8篇 |
1994年 | 18篇 |
1993年 | 11篇 |
1992年 | 4篇 |
1991年 | 6篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 12篇 |
1982年 | 10篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1971年 | 2篇 |
1964年 | 1篇 |
排序方式: 共有763条查询结果,搜索用时 125 毫秒
461.
Robert M. Hughes Alan T. Herlihy Philip R. Kaufmann 《Journal of the American Water Resources Association》2010,46(4):792-806
Hughes, Robert M., Alan T. Herlihy, and Philip R. Kaufmann, 2010. An Evaluation of Qualitative Indexes of Physical Habitat Applied to Agricultural Streams in Ten U.S. States. Journal of the American Water Resources Association (JAWRA) 46(4): 792-806. DOI: 10.1111/j.1752-1688.2010.00455.x Abstract: Assessment of stream physical habitat condition is important for evaluating stream quality globally. However, the diversity of metrics and methods for assessing physical habitat condition confounds comparisons among practitioners. We surveyed 51 previously sampled stream sites (0.0-6.3 m wide) located in regions of row-crop agriculture in Oregon, California, North Dakota, South Dakota, Nebraska, Iowa, Minnesota, Pennsylvania, Maryland, and West Virginia to evaluate the comparability of four indexes of physical habitat condition relative to each other. We also compared the indexes to previously calculated indexes of fish and macroinvertebrate condition. The physical habitat indexes included the Stream Visual Assessment Protocol Version 2 of the Natural Resources Conservation Service, the qualitative habitat evaluation index of the Ohio Environmental Protection Agency, the rapid bioassessment protocol of the United States Environmental Protection Agency (USEPA), and a qualitative physical habitat index based on USEPA quantitative physical habitat measurements. All four indexes were highly correlated with each other, but low-to-moderately correlated with biotic index scores for fish and macroinvertebrate assemblages. Moderately high correlations occurred between some macroinvertebrate biotic index scores and quantitative metrics. We conclude that additional research is needed to increase the predictive and diagnostic capabilities of qualitative physical habitat indexes. 相似文献
462.
463.
Stream temperature is an important component of salmonid habitat and is often above levels suitable for fish survival in the Lower Klamath River in northern California. The objective of this study was to provide boundary conditions for models that are assessing stream temperature on the main stem for the purpose of developing strategies to manage stream conditions using Total Maximum Daily Loads. For model input, hourly stream temperatures for 36 tributaries were estimated for 1 Jan. 2001 through 31 Oct. 2004. A basin-scale approach incorporating spatially distributed energy balance data was used to estimate the stream temperatures with measured air temperature and relative humidity data and simulated solar radiation, including topographic shading and corrections for cloudiness. Regression models were developed on the basis of available stream temperature data to predict temperatures for unmeasured periods of time and for unmeasured streams. The most significant factor in matching measured minimum and maximum stream temperatures was the seasonality of the estimate. Adding minimum and maximum air temperature to the regression model improved the estimate, and air temperature data over the region are available and easily distributed spatially. The addition of simulated solar radiation and vapor saturation deficit to the regression model significantly improved predictions of maximum stream temperature but was not required to predict minimum stream temperature. The average SE in estimated maximum daily stream temperature for the individual basins was 0.9 +/- 0.6 degrees C at the 95% confidence interval. 相似文献
464.
Mergler D Anderson HA Chan LH Mahaffey KR Murray M Sakamoto M Stern AH;Panel on Health Risks Toxicological Effects of Methylmercury 《Ambio》2007,36(1):3-11
The paper builds on existing literature, highlighting current understanding and identifying unresolved issues about MeHg exposure, health effects, and risk assessment, and concludes with a consensus statement. Methylmercury is a potent toxin, bioaccumulated and concentrated through the aquatic food chain, placing at risk people, throughout the globe and across the socioeconomic spectrum, who consume predatory fish or for whom fish is a dietary mainstay. Methylmercury developmental neurotoxicity has constituted the basis for risk assessments and public health policies. Despite gaps in our knowledge on new bioindicators of exposure, factors that influence MeHg uptake and toxicity, toxicokinetics, neurologic and cardiovascular effects in adult populations, and the nutritional benefits and risks from the large number of marine and freshwater fish and fish-eating species, the panel concluded that to preserve human health, all efforts need to be made to reduce and eliminate sources of exposure. 相似文献
465.
Transport and transformation of sulfur compounds over East Asia during the TRACE-P and ACE-Asia campaigns 总被引:4,自引:0,他引:4
Meigen Zhang Itsushi Uno Yasuhiro Yoshida Yongfu Xu Zifa Wang Hajime Akimoto Timothy Bates Trish Quinn Alan Bandy Byron Blomquist 《Atmospheric environment (Oxford, England : 1994)》2004,38(40):6947
On the basis of the recently estimated emission inventory for East Asia with a resolution of 1×1°, the transport and chemical transformation of sulfur compounds over East Asia during the period of 22 February through 4 May 2001 was investigated by using the Models-3 Community Multi-scale Air Quality (CMAQ) modeling system with meteorological fields calculated by the regional atmospheric modeling system (RAMS). For evaluating the model performance simulated concentrations of sulfur dioxide (SO2) and aerosol sulfate (SO42−) were compared with the observations on the ground level at four remote sites in Japan and on board aircraft and vessel during the transport and chemical evolution over the Pacific and Asian Pacific regional aerosol characterization experiment field campaigns, and it was found that the model reproduces many of the important features in the observations, including horizontal and vertical gradients. The SO2 and SO42− concentrations show pronounced variations in time and space, with SO2 and SO42− behaving differently due to the interplay of chemical conversion, removal and transport processes. Analysis of model results shows that emission was the dominant term in regulating the SO2 spatial distribution, while conversion of SO2 to SO42− in the gas phase and the aqueous phase and wet removal were the primary factors that controlled SO42− amounts. The gas phase and the aqueous phase have the same importance in oxidizing SO2, and about 42% sulfur compounds (25% in SO2) emitted in the model domain was transported out, while about 57% (35% by wet removal processes) was deposited in the domain during the study period. 相似文献
466.
Nicolas Alcala Alan E. Launer Michael F. Westphal Richard Seymour Esther M. Cole Noah A. Rosenberg 《Conservation biology》2019,33(3):685-696
Assessing causes of population decline is critically important to management of threatened species. Stochastic patch occupancy models (SPOMs) are popular tools for examining spatial and temporal dynamics of populations when presence–absence data in multiple habitat patches are available. We developed a Bayesian Markov chain method that extends existing SPOMs by focusing on past environmental changes that may have altered occupancy patterns prior to the beginning of data collection. Using occupancy data from 3 creeks, we applied the method to assess 2 hypothesized causes of population decline—in situ die-off and residual impact of past source population loss—in the California red-legged frog. Despite having no data for the 20–30 years between the hypothetical event leading to population decline and the first data collected, we were able to discriminate among hypotheses, finding evidence that in situ die-off increased in 2 of the creeks. Although the creeks had comparable numbers of occupied segments, owing to different extinction–colonization dynamics, our model predicted an 8-fold difference in persistence probabilities of their populations to 2030. Adding a source population led to a greater predicted persistence probability than did decreasing the in situ die-off, emphasizing that reversing the deleterious impacts of a disturbance may not be the most efficient management strategy. We expect our method will be useful for studying dynamics and evaluating management strategies of many species. 相似文献
467.
Jeffrey Alan Hoffmann 《Environmental Communication: A Journal of Nature and Culture》2018,12(6):807-824
The following study looks at how traditional, organic, cooperative farmers starting a new farming cooperative in the US Southwest communicate about their farming as a set of (sustainable) cultural practices. The study draws on environmental communication theory, the theory of the coordinated management of meaning, and Vandana Shiva’s three-tiered economic model to construct a communication-based framework through which to view farmers’ stories about sustainability. This framework is productive, showing how some Nuevo Mexicano farmers (and others) orient toward farming, sustenance, and human-nature relationships through community, family, heritage, and education. Moreover, in addition to a conceptualization of sustainability as specific practices for nurturing and enduring in environments, communities, and organizations/institutions, sustainability can be understood as embedded ecocultural and historical experience with cross-cultural parallels in land-based communities. This study advances the ethical duty of environmental communication to better understand the ways in which environmental discourse and ecocultural and material realities are imbricated, as well as the call for such discursive study to be grounded in phenomenological experience of the natural world. 相似文献
468.
Elevated levels of P in urban streams can pose significant water quality problems. Sources of P in urban streams, however, are difficult to identify. It is important to recognize both natural and anthropogenic sources of P. We investigated near-stream chemistry and land use factors on stream water P in the urbanizing Johnson Creek watershed in Portland, OR, USA. We sampled stream water and shallow groundwater soluble reactive P (SRP) and total P (TP) and estimated P flux at 13 sites along the main stem of Johnson Creek, with eight sites in urban land use areas and five sites in nonurban land use areas. At each site, we sampled the A and B horizons, measuring soil pH, water-soluble P, acid-soluble P, base-soluble P, total P, Fe, and Al. We found continuous input of P to the stream water via shallow groundwater throughout the Johnson Creek watershed. The shallow groundwater P concentrations were correlated with stream water P within the nonurban area; however, this correlation was not found in the urban area, suggesting that other factors in the urban area masked the relationship between groundwater P and stream water P. Aluminum and Fe concentrations were inversely correlated with shallow groundwater P, suggesting that greater P adsorption to Al and Fe oxides in the nonurban area reduced availability of shallow groundwater P. Using stepwise multiple regression analysis, however, we concluded that while riparian soil chemistry was related to stream water P, land use patterns had a more significant relationship with stream water P concentrations in this urbanizing system. 相似文献
469.
Burkey KO Neufeld HS Souza L Chappelka AH Davison AW 《Environmental pollution (Barking, Essex : 1987)》2006,143(3):427-434
Cutleaf coneflower (Rudbeckia laciniata L.), crown-beard (Verbesina occidentalis Walt.), and tall milkweed (Asclepias exaltata L.) are wildflower species native to Great Smoky Mountains National Park (U.S.A.). Natural populations of each species were analyzed for leaf ascorbic acid (AA) and dehydroascorbic acid (DHA) to assess the role of ascorbate in protecting the plants from ozone stress. Tall milkweed contained greater quantities of AA (7-10 micromol g(-1) fresh weight) than crown-beard (2-4 micromol g(-1) fresh weight) or cutleaf coneflower (0.5-2 micromol g(-1) fresh weight). DHA was elevated in crown-beard and cutleaf coneflower relative to tall milkweed suggesting a diminished capacity for converting DHA into AA. Tall milkweed accumulated AA in the leaf apoplast (30-100 nmol g(-1) fresh weight) with individuals expressing ozone foliar injury symptoms late in the season having less apoplast AA. In contrast, AA was not present in the leaf apoplast of either crown-beard or cutleaf coneflower. Unidentified antioxidant compounds were present in the leaf apoplast of all three species. Overall, distinct differences in antioxidant metabolism were found in the wildflower species that corresponded with differences in ozone sensitivity. 相似文献
470.
Abu-Allaban M Hamasha S Gertler A 《Journal of the Air & Waste Management Association (1995)》2006,56(10):1440-1444
Many areas in Jordan suffer from elevated levels of coarse particulate matter (PM10). One potentially significant source of the observed PM is the resuspension of road dust in the vicinity of limestone quarries. To obtain data to assess the impact from this source, PM10 road dust resuspension factors near Abusiiah, a town to the north east of Amman surrounded by many quarries and brick factories, were measured. Measurements included PM10 mass, particle size distributions, wind speed, and wind direction. The results showed that PM10 concentrations could be as high as 600 microg/m3, and most of the airborne PM is in the coarse fraction. Loading trucks play a major role in resuspending road dust, with an observed PM10 emission rate of >6000 mg/km. 相似文献