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761.
结合2001-2006年巢湖水质监测数据、相关文献资料,分析主要污染物变化趋势和富营养化形成原因,对其水体富营养化状态进行分析.提出防治对策建议。分析结果表明:巢湖水体6年间营养状态在轻度富营养和中度富营养之间。主要营养盐总磷、总氮及高锰酸盐指数6年间均无显著变化,农业面源污染和适宜的气候条件是巢湖水体富营养化形成的主要原因。 相似文献
762.
Stephen M. Born 《Environmental management》1979,3(2):145-153
The widespread recognition of lake degradation as a major environmental concern has led to accelerated efforts to better protect and manage lake resources. Where it is too late for avoidance strategies, lake rehabilitation is receiving increasing attention as a natural resources management option. In recent years, a significant number of lake rehabilitation experiences has been documented throughout the world, and many nations and states have embarked upon major lake rehabilitation programsLake rehabilitation is not a ready-to-go technology at this time and still must be regarded as partly experimental. Nevertheless, there have been a number of notably successful lake rehabilitation experiences. Reducing or halting the influx of undesirable materials is the sine qua non for lake rehabilitation. In most successful experiences to date, this has been accomplished by diversion and/or wastewater treatment. A number of in-lake strategies have also been employed to rehabilitate degraded lakes, often as part of an overall restoration plan. Techniques that appear to be most useful include dredging and nutrient inactivation. Several examples of successful applications are noted.Although efforts to rehabilitate lakes have produced a mixed record, there are encouraging results that suggest the viability of this approach. Lake rehabilitation, however, is no substitute for environmental management strategies that provide for protection of lake ecosystems in the first place. 相似文献
763.
764.
GIS应用于城市重大危险源监控的综述 总被引:1,自引:5,他引:1
系统地总结出GIS在重大危险源监控方面的应用现状,简要介绍了地理信息系统的概念及其在重大危险源监控方面的作用。重点论述利用GIS的基本功能强化重大危险源安全管理;利用WebGIS技术对整个地区的重大危险源进行监控,实现信息共享;利用基于GIS的监控预警技术,降低事故率;利用GIS和GPS结合的方法,减少事故引发的损失;利用GIS决策支持技术,指导监控及应急救援。经过分析论证得出的结论是:研究GIS空间分析、模型分析和基础数据的获取技术是今后努力的方向。提出GIS在重大危险源监控方面的应用的发展趋势,为GIS技术在我国重大危险源监控方面的应用发展提供借鉴。 相似文献
765.
Long-term time-series data sets of two shallow Dutch lakes, Lake Veluwemeer and Lake Wolderwijd were subjected to ordination
and clustering by means of non-supervised artificial neural networks (ANN). Splitting of the data sets into sub-series corresponding
with three different management periods have allowed a comparative analysis of both the short-term seasonal and long-term
phytoplankton dynamics in relation to the restoration measures. The lakes were considered as hyper-eutrophic and have been
managed both with bottom-up and top-down management approaches. Results of the study have demonstrated that non-supervised
ANN allow to elucidate causal relationships of complex ecological processes (1) within the specific genus, Oscillatoria and Scenedesmus and (2) the combination of external nutrient control and in-lake food web manipulation of the two lakes achieved to control
eutrophication. 相似文献
766.
Jing Zhang 《Water, Air, & Soil Pollution: Focus》2007,7(6):583-592
Industrialization and urbanization along the coastal population centers have brought great changes in the land cover and material
fluxes from watersheds to receiving bays and estuaries. We have embarked a multiyear research project on “Watersheds Nutrient
Loss and Eutrophication of Jiaozhou Bay” for the period of 2000 to 2004, funded by the Natural Science Foundation of China
to examine human influence on the marine sector of ecosystem. Jiaozhou Bay, located in the southern part of Shandong Peninsula,
was selected because of the existence of long-term hydrographic and meteorological records since the 1930s and recent observations
on the marine ecological variables. We have made extensive and periodic measurements on the water movement, nutrients, phytoplankton,
and microbe in water column and bottom sediments. Box and 3-dimensional hydrodynamic models were developed and utilized to
understand the evolution of eutrophic status with time. It was found that primary productivity has suffered from silica depletion
followed by phosphate, and the dominance of large phytoplankton has been replaced by small-size communities. These ecosystem
changes were brought by the changes in the relative contribution among major pathways and concentrations, owing to the human
activities in the watershed. Eight articles in this volume reported various aspects of the linkage between watershed human
activities and ecosystem for the Jiaozhou Bay as the initial outcome of this project. 相似文献
767.
Christopher M. B. Lehmann Van C. Bowersox Robert S. Larson Susan M. Larson 《Water, Air, & Soil Pollution: Focus》2007,7(1-3):59-66
Data from the National Atmospheric Deposition Program/National Trends Network (NADP/NTN) indicate significant changes have
occurred in precipitation chemistry and the chemical climate in the United States (US). A Seasonal Kendall Trend (SKT) analysis
shows statistically significant increases in precipitation ammonium concentrations at 64% of 159 continental US NADP/NTN sites
evaluated from Winter 1985 to Fall 2004 (Dec. 1984 – Nov. 2004). Sulfate decreases were widespread, with an SKT analysis indicating
statistically significant decreases at 89% of sites evaluated. Ratios of chemical equivalent concentrations of ammonium to
sulfate in precipitation have risen to the extent that ammonium now exceeds sulfate over more than half of the continental
U.S. on a precipitation-weighted-mean annual basis. These trends in the concentrations of ammonium, sulfate, and other species
have been accompanied by significant decreases in the frequency of acidic precipitation (pH < 5.0) in the last decade. 相似文献
768.
769.
Nicole R. Mytyk Joseph J. Delfino 《Journal of the American Water Resources Association》2004,40(4):913-924
ABSTRACT: Nitrate levels in the Ocklawaha River Basin in north central Florida were reviewed over a 50‐year period. Data were obtained from the literature, U.S. Environmental Protection Agency (USEPA) STOrage and RETrieval (STORET), and U.S. Geological Survey (USGS) databases. The study objective was to determine whether nitrate concentrations are increasing and if so, whether this increase is linked to land use changes. Increasing nitrate levels were seen at 5 of the 14 stations, while other stations showed no trend or a decreasing trend. Median nitrate concentrations in the Ocklawaha River increased from 0.07 mg‐N/L to 0.78 mg‐N/L at sites downstream from the Silver River. Throughout the Rodman Reservoir, median nitrate concentrations decreased from 0.48 mg‐N/L to 0.01 mg‐N/L and increased to 0.04 mg‐N/L after the Kirkpatrick Dam. Flow and concentration relationships were correlated for five stations. At four of the five stations nitrate concentrations decreased in response to increasing flow, likely the result of dilution with nitrate poor water. Changes in land use over a 20‐ year period (1970 to 1990) also were monitored. Sources of nitrate have been linked by isotopic analysis to organic and inorganic fertilizers, which appear to be related to increased urbanization and an increase in lawns that require nutrient fertilization. 相似文献
770.