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   30996篇
  免费   361篇
  国内免费   240篇
安全科学   944篇
废物处理   1141篇
环保管理   4404篇
综合类   4839篇
基础理论   8892篇
环境理论   24篇
污染及防治   8002篇
评价与监测   1832篇
社会与环境   1297篇
灾害及防治   222篇
  2022年   196篇
  2021年   198篇
  2020年   177篇
  2019年   234篇
  2018年   432篇
  2017年   426篇
  2016年   609篇
  2015年   538篇
  2014年   726篇
  2013年   2245篇
  2012年   900篇
  2011年   1368篇
  2010年   1104篇
  2009年   1103篇
  2008年   1336篇
  2007年   1422篇
  2006年   1273篇
  2005年   1064篇
  2004年   1063篇
  2003年   1000篇
  2002年   986篇
  2001年   1272篇
  2000年   883篇
  1999年   570篇
  1998年   450篇
  1997年   448篇
  1996年   460篇
  1995年   495篇
  1994年   452篇
  1993年   409篇
  1992年   432篇
  1991年   385篇
  1990年   383篇
  1989年   415篇
  1988年   356篇
  1987年   313篇
  1986年   285篇
  1985年   310篇
  1984年   295篇
  1983年   327篇
  1982年   328篇
  1981年   275篇
  1980年   248篇
  1979年   277篇
  1978年   229篇
  1977年   195篇
  1976年   200篇
  1975年   193篇
  1974年   174篇
  1972年   198篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
671.
This paper demonstrates empirically the gain from adopting more general equilibrium approaches in projecting the effects on domestic output and international trade of environmental controls. The suggested models include a partial equilibrium case where all industries are treated independently, an intermediate case incorporating effects in supplying industries, and general equilibrium formulations based on alternative macroeconomic conditions. U. S. data is used to evaluate these models. Under both pollutor pays and subsidy financing schemes, moving from the simplest case to the intermediate model results in quite different industry projections. Including macroeconomic factors appears particularly important in the classical setting.  相似文献   
672.
Involuntary eye movements in salamanders   总被引:1,自引:0,他引:1  
  相似文献   
673.
Taylor AJ 《Disasters》1983,7(1):37-40
This paper defines the various levels within government, the voluntary agencies and the community which might benefit from training and makes suggestions as to where the emphasis should be placed. It points out that training programmes should be designed to meet the expressed needs of a particular group of trainees as well as be related to the current or potential disaster situation.  相似文献   
674.
675.
676.
677.
678.
679.
A fish‐consumption advisory is currently in effect in a seven‐mile stretch of the Grasse River in Massena, New York, due to elevated levels of PCBs in fish tissue. One remedial approach that is being evaluated to reduce the PCB levels in fish from the river is in situ capping. An in‐river pilot study was conducted in the summer of 2001 to assess the feasibility of capping PCB‐containing sediments of the river. The study consisted of the construction of a subaqueous cap in a seven‐acre portion of the river using various combinations of capping materials and placement techniques. Optimal results were achieved with a 1:1 sand/topsoil mix released from a clamshell bucket either just above or several feet below the water surface. A longer‐term monitoring program of the capped area commenced in 2002. Results of this monitoring indicated: 1) the in‐place cap has remained intact since installation; 2) no evidence of PCB migration into and through the cap; 3) groundwater advection through the cap is not an important PCB transport mechanism; and 4) macroinvertebrate colonization of the in‐place cap is continuing. Additional follow‐up monitoring in the spring of 2003 indicated that a significant portion of the cap and, in some cases, the underlying sediments had been disturbed in the period following the conclusion of the 2002 monitoring work. An analysis of river conditions in the spring of 2003 indicated that a significant ice jam had formed in the river directly over the capping pilot study area, and that the resulting increase in river velocities and turbulence in the area resulted in the movement of both cap materials and the underlying sediments. The pilot cap was not designed to address ice jam–related forces on the cap, as the occurrence of ice jams in this section of the river had not been known prior to the observations conducted in the spring of 2003. These findings will preclude implementation of the longer‐term monitoring program that had been envisioned for the pilot study. The data collected immediately after cap construction in 2001 and through the first year of monitoring in 2002 serve as the basis for the conclusions presented in this article. It should be recognized that, based on the observation made in the spring of 2003, some of these conclusions are no longer valid for the pilot study area.The occurrence of ice jams in the lower Grasse River and their importance on sediments and PCBs within the system are currently under investigation. © 2003 Wiley Periodicals, Inc.  相似文献   
680.
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   
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