首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   40521篇
  免费   310篇
  国内免费   232篇
安全科学   815篇
废物处理   1808篇
环保管理   5310篇
综合类   8915篇
基础理论   10043篇
环境理论   16篇
污染及防治   9026篇
评价与监测   2512篇
社会与环境   2449篇
灾害及防治   169篇
  2018年   1867篇
  2017年   1752篇
  2016年   1685篇
  2015年   520篇
  2014年   573篇
  2013年   2180篇
  2012年   1213篇
  2011年   2386篇
  2010年   1617篇
  2009年   1611篇
  2008年   2005篇
  2007年   2463篇
  2006年   1066篇
  2005年   959篇
  2004年   908篇
  2003年   977篇
  2002年   947篇
  2001年   1050篇
  2000年   727篇
  1999年   500篇
  1998年   396篇
  1997年   359篇
  1996年   389篇
  1995年   421篇
  1994年   445篇
  1993年   381篇
  1992年   404篇
  1991年   382篇
  1990年   423篇
  1989年   403篇
  1988年   330篇
  1987年   329篇
  1986年   309篇
  1985年   323篇
  1984年   347篇
  1983年   336篇
  1982年   335篇
  1981年   349篇
  1980年   304篇
  1979年   310篇
  1978年   266篇
  1977年   240篇
  1976年   249篇
  1974年   267篇
  1973年   243篇
  1972年   234篇
  1968年   233篇
  1967年   267篇
  1966年   226篇
  1965年   218篇
排序方式: 共有10000条查询结果,搜索用时 578 毫秒
51.
52.
53.
The effect of industrial air pollution on natural small mammal populations has been studied in the northern taiga subzone of the boreal forest zone. The results of long-term monitoring have been used to demonstrate the possibility of predicting changes in the main population and community characteristics of the animal species studied as dependent on the degree of anthropogenic impact.  相似文献   
54.
55.
56.
57.
Summary. Varroa reproduction is closely synchronized to the development of its host. In this study we present a new bioassay for field and laboratory tests to evaluate host factors triggering Varroa oogenesis. Female mites deprived of feeding activated oogenesis when perceiving larval volatiles. In laboratory assays the living L5-larva and pentane extracts of the larval cuticle had a clear activating effect. Wax and larval food did not elicit Varroa oogenesis. The activating components apparently are in the polar fraction of the cuticular volatiles. The consequences of this regulative mechanism for the host parasite relationship and prospects for further research are discussed.  相似文献   
58.
59.
Sustainable development of the earth's limited water and land resources is of paramount importance because of rising world population and existing conflicting demands for these resources. Enormous capital investment has been made in developing these resources, but now there is irrefutable evidence that such developments have led to major resource degradation. This includes problems of salinisation and damages to ecosystems. The countries predominantly affected by human induced salinisation are located in arid and semi-arid regions of the world and include Australia, China, Egypt, India, Pakistan, USSR, and USA. This paper describes the processes of salinisation, its impacts and the use of quantitative methods in salinity investigation and management. Australia is used as a case study of typical salinity problems and as a demonstration of the fruitful application of quantitative methods. The paper concludes that quantitative methods such as surface water and groundwater models are powerful design, management and predictive tools in salinity investigation. However, application of some models, such as those for unsaturated flow and transport and groundwater solute transport, are not widespread due to uncertainties in describing the complexity of the processes and the lack of hydrodispersive data.  相似文献   
60.
The past two decades have witnessed an increase in the exploration for, and development of, mineral resources at Arctic latitudes. Such effort has resulted in the commencement of production at a number of different localities in close proximity to the ocean. Since proximity to a source of transportation for the conveyance of concentrates to the market is a primary requirement governing the economic decisions for the mine to proceed, it is logical that ore deposits near a coastline are primary targets for development.

Closely tied to coastal mining developments is the need to dispose of tailings and waste rock in the most economical manner. Prior to the advent of heightened public awareness and environmental concern, and the enactment of pollution legislation, disposal practices were largely based upon convenience. Currently, however, proposed disposal and operating practices receive closer scrutiny, with a view to providing adequate protection for aquatic resources and habitat. This paper summarizes some of the features of three Arctic mines, wastes from which enter the marine environment, and compares the disposal practices used at each to measures of environmental change as indicated by metal concentrations in various media.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号