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   31672篇
  免费   371篇
  国内免费   247篇
安全科学   960篇
废物处理   1144篇
环保管理   4672篇
综合类   4865篇
基础理论   9043篇
环境理论   21篇
污染及防治   8179篇
评价与监测   1872篇
社会与环境   1326篇
灾害及防治   208篇
  2022年   194篇
  2021年   201篇
  2020年   180篇
  2019年   236篇
  2018年   425篇
  2017年   423篇
  2016年   625篇
  2015年   536篇
  2014年   729篇
  2013年   2368篇
  2012年   921篇
  2011年   1373篇
  2010年   1104篇
  2009年   1131篇
  2008年   1351篇
  2007年   1450篇
  2006年   1271篇
  2005年   1063篇
  2004年   1093篇
  2003年   1009篇
  2002年   998篇
  2001年   1287篇
  2000年   895篇
  1999年   587篇
  1998年   459篇
  1997年   470篇
  1996年   476篇
  1995年   525篇
  1994年   470篇
  1993年   426篇
  1992年   434篇
  1991年   399篇
  1990年   403篇
  1989年   430篇
  1988年   371篇
  1987年   322篇
  1986年   310篇
  1985年   323篇
  1984年   316篇
  1983年   346篇
  1982年   342篇
  1981年   297篇
  1980年   260篇
  1979年   284篇
  1978年   240篇
  1977年   204篇
  1976年   209篇
  1975年   198篇
  1974年   179篇
  1972年   205篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
93.
The development of traceability in low-level radioactivity measurements is discussed. The role that the development of large quantities of natural matrix standards can play is also discussed.  相似文献   
94.
Deposition velocities have been determined for corn and soybeans in the first 4–6 weeks of growth in a full-scale study of canopy flow in a wind tunnel. Particles of 1, 5, 10 and 15 μm aerodynamic diameter made of sodium florescein were injected into the Environmental Wind Tunnel Facility at Colorado State University. Deposition velocities were determined as a function of free stream velocity (183, 305 and 610 cm/s) and approach flow turbulence intensity (~1% and 8%). Plants were arranged in realistic field configurations. Hot-wire anemometer studies confirmed that the fluid velocity profiles developed in the wind tunnel were similar to the flow realized in canopies in natural fields. An increase in velocity and turbulence intensity was found to decrease the deposition velocities. A minimum deposition velocity was observed at a particle diameter of 5 μm.  相似文献   
95.
96.
97.
98.
99.
In the UK for the period 1994-99, a broad range of environmental projects were given financial support through the European Agriculture Guidance and Guarantee Fund under the Objective 1 and Objective 5b programmes. This paper is concerned with the ex-post evaluation of these projects set within a Sustainable Development framework. The aim was to identify project types or characteristics that offered the greatest return on investment. A classification of six broad project types was adopted. The evaluation revealed that there were significant differences between individual projects with respect to the type and scale, and temporal and social distribution of the benefits they delivered. In particular, as well as delivering environmental and economic benefits, many projects made a significant contribution to the development of human and social capital. The paper concludes that it is possible to improve the basis for future project selection in order to maximise the returns on environmental investments in the context of sustainable development.  相似文献   
100.
This article does not focus on adaptation or mitigation policy directly but on an allied opportunity that exists for the Pacific Islands via the auspices of the Climate Convention, because the existing very costly energy systems used in the Pacific Island region are fossil-fuel dependent. It is argued here that efforts can be made towards the development of energy systems that are ecologically sustainable because Pacific Island nations are eligible to receive assistance to introduce renewable energy technology and pursue energy conservation via implementation mechanisms of the Climate Convention and, in particular, through transfer of technology and via joint implementation. It is contended that assistance in the form of finance, technology, and human resource development from developed countries and international organizations would provide sustainable benefits in improving the local Pacific Island environments. It is also emphasized that mitigation of greenhouse gas emissions is not the responsibility of the Pacific Islands as they contribute very little on a per capita global scale and a tiny proportion of total global greenhouse gas emissions.  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