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   29874篇
  免费   315篇
  国内免费   200篇
安全科学   797篇
废物处理   1241篇
环保管理   4087篇
综合类   5056篇
基础理论   8266篇
环境理论   17篇
污染及防治   7530篇
评价与监测   1835篇
社会与环境   1351篇
灾害及防治   209篇
  2022年   206篇
  2021年   216篇
  2019年   205篇
  2018年   369篇
  2017年   366篇
  2016年   582篇
  2015年   457篇
  2014年   670篇
  2013年   2297篇
  2012年   861篇
  2011年   1207篇
  2010年   991篇
  2009年   1049篇
  2008年   1225篇
  2007年   1263篇
  2006年   1125篇
  2005年   985篇
  2004年   915篇
  2003年   913篇
  2002年   877篇
  2001年   1120篇
  2000年   839篇
  1999年   491篇
  1998年   365篇
  1997年   401篇
  1996年   415篇
  1995年   487篇
  1994年   438篇
  1993年   406篇
  1992年   380篇
  1991年   417篇
  1990年   410篇
  1989年   385篇
  1988年   339篇
  1987年   330篇
  1986年   307篇
  1985年   273篇
  1984年   337篇
  1983年   299篇
  1982年   356篇
  1981年   303篇
  1980年   257篇
  1979年   280篇
  1978年   245篇
  1977年   217篇
  1976年   188篇
  1975年   204篇
  1974年   205篇
  1973年   217篇
  1972年   198篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Results of a recent intercomparison on the determination of trace elements in simulated air filter samples are reported. A large scatter of results is obtained for some elements and systematic differences between laboratories are observed. The performance of different methods, in particular neutron activation analysis and atomic absorption spectrophotometry, used by the various laboratories is discussed (air filter analysis; intercomparison; trace elements; control charts).  相似文献   
104.
105.
Dimock  R. V.  Groves  K. H. 《Marine Biology》1975,33(4):301-308
Marine Biology - The combined effects of temperature and salinity on the rate of oxygen consuption by the estuarine crab Panopeus herbstii Milne-Edwards (Crustacea: Decapoda: Xanthidae) were...  相似文献   
106.
There is a growing recognition that knowledge of indigenous communities, based on accumulated observations and experience over time, is significant for sustainable environmental management in collaboration with modern scientific knowledge. A number of innovative policy initiatives are currently being implemented in New Zealand to enable indigenous Maori tribes and sub-tribes to rehabilitate and manage their local fisheries in accordance with customary values and practices. These policies are an important milestone from an historical perspective as they are meant to recognise and empower the role of Maori as Treaty partners. The fisheries management regime in New Zealand now provides for Maori representation at the local level within a co-management framework that enables local Maori communities to exercise their customary rights. These institutional arrangements have been crafted to facilitate Maori input, based on customary values and practices, to complement modern Western management practices for sustainable harvesting of marine resources. Nevertheless, the degree to which these initiatives constitute an adequate response to Maori Treaty aspirations is debatable. A major constraint in this respect is that the government is compelled to recognise the needs of other, economically and politically more dominant, non-Maori user-groups in allocating and managing access to fishery resources and the marine environment.  相似文献   
107.
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   
108.
The creation of a cloned sheep from mammary tissue has raisedmajor social concern, and much talk about major ethical issuesoccasioned by this technology. It is necessary to separategenuine from spurious ethical issues here, a task made failureto initiate ethical discussion and explanation of new technologyas well as by fear reactions in society. As in geneticengineering of animals, issues about cloning fall into threecategories – suggestions that the technology is inherently wrong,risk emerging from the technology and harm to the creatureengendered. The issues regarding the cloning of humans can beanalyzed using the same categories.  相似文献   
109.
ABSTRACT: Evidence is presented that snowmelt runoff from an urban watershed can produce density current intrusions (underflows) in a lake. Several episodes of density current intrusions are documented. Water temperatures and salinities measured near the bottom of a 10 m deep Minneapolis lake during the late winter warming periods in 1989, 1990, 1991, and 1995 show significant rapid changes which are correlated with observed higher air temperatures and snowmelt runoff. The snowmelt runoff entering this particular lake (Ryan Lake) has increased electrical conductivity, salinity, and density. The source of the salinity is the salt spread on urban streets in the winter. Heating of littoral waters in spring may also contribute to the occurrence of the sinking flows, but is clearly not the only cause.  相似文献   
110.
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