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   34429篇
  免费   365篇
  国内免费   267篇
安全科学   1070篇
废物处理   1709篇
环保管理   4356篇
综合类   5012篇
基础理论   9179篇
环境理论   14篇
污染及防治   8711篇
评价与监测   2482篇
社会与环境   2333篇
灾害及防治   195篇
  2023年   175篇
  2022年   389篇
  2021年   471篇
  2020年   257篇
  2019年   316篇
  2018年   619篇
  2017年   638篇
  2016年   980篇
  2015年   633篇
  2014年   1048篇
  2013年   2800篇
  2012年   1357篇
  2011年   1674篇
  2010年   1297篇
  2009年   1282篇
  2008年   1606篇
  2007年   1546篇
  2006年   1368篇
  2005年   1440篇
  2004年   1485篇
  2003年   1348篇
  2002年   1012篇
  2001年   1129篇
  2000年   796篇
  1999年   505篇
  1998年   378篇
  1997年   389篇
  1996年   403篇
  1995年   481篇
  1994年   403篇
  1993年   346篇
  1992年   380篇
  1991年   357篇
  1990年   329篇
  1989年   322篇
  1988年   297篇
  1987年   242篇
  1986年   249篇
  1985年   248篇
  1984年   267篇
  1983年   254篇
  1982年   269篇
  1981年   221篇
  1980年   166篇
  1979年   183篇
  1978年   164篇
  1977年   133篇
  1975年   137篇
  1973年   167篇
  1972年   142篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
51.
Cultural heritage is being addressed by a number of charters and conventions and it is clear that its consideration within decision-making processes is progressively becoming a real challenge, both for developers and public authorities. Against this background, this paper reviews the environmental assessment framework developed by the European Community, as this should increasingly influence decision making about cultural heritage in an urban setting. The legislative framework for access to environmental information is also reviewed because of its relevance to the decision-making process.The Directives on Environmental Impact Assessment and Strategic Environmental Assessment both require a consideration of cultural heritage in decision making. This requirement can go some way to addressing the paradox in the European Community's position whereby the community wishes to conserve and enhance its own cultural identity whilst, at the same time, cultural heritage is usually defined at a local level. The present paper suggests that, given their flexibility, the two European Community directives on environmental assessment constitute a promising opportunity to address this seeming paradox, but that there is a significant gap between legal obligations and the methodological tools to meet them.  相似文献   
52.
53.
54.
55.
56.
57.
This work, carried out within the framework of the PRISMA II project, aims at evaluating the effects of the Po River flow on primary productivity, measured by C with in situ sample incubations. A total of four cruises was carried out in late winter and early summer (1996-1998) along transects from the coast offshore. In both seasons, the highest primary productivity was found in the most oligohaline stations. The effects of the Po River inputs were therefore clearly evident in the westernmost area, both in high productivity values and in the shape of productivity profiles. In late winter, extensive blooms of Skeletonema costatum and Pseudo-nitzschia delicatissima resulted in productivity values that were sometimes higher than in early summer. In early summer 1996, greatly reduced river flow clearly influenced productivity which was much lower than in 1997.  相似文献   
58.
59.
60.
Three monoclonal antibodies (MAbs) against trophoblast (GB17, GB21, and GB25) and flow cytometry were used to sort trophoblast-like cells (TLCs) from peripheral blood of pregnant women. Sorted TLCs were processed for electron microscopy and fetal DNA amplification of the Y-specific sequences from mothers carrying male fetuses. At the ultra-structural level, most of the nucleated cells had the morphology of leucocytes, suggesting maternal contaminants, and we did not find the characteristic features of the free inter-villous trophoblast cells. Nevertheless, polymerase chain reaction (PCR) analysis showed an amplification of Y-specific sequences in two out of three samples of sorted TLCs. These results suggest that besides the maternal leucocytes, sufficient trophoblast nucleated fetal cells can be obtained using cell enrichment by sorting. This sensitive method holds promise for non-invasive prenatal diagnosis of fetal sex and if sufficient Y(positive) nuclei are found, for the diagnosis of selected numerical chromosome abnormalities.  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