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   38652篇
  免费   340篇
  国内免费   248篇
安全科学   1014篇
废物处理   2169篇
环保管理   5027篇
综合类   5342篇
基础理论   10554篇
环境理论   8篇
污染及防治   9007篇
评价与监测   3058篇
社会与环境   2878篇
灾害及防治   183篇
  2023年   133篇
  2022年   270篇
  2021年   337篇
  2020年   201篇
  2019年   253篇
  2018年   1794篇
  2017年   1720篇
  2016年   1830篇
  2015年   645篇
  2014年   885篇
  2013年   2492篇
  2012年   1451篇
  2011年   2565篇
  2010年   1740篇
  2009年   1664篇
  2008年   2189篇
  2007年   2426篇
  2006年   1216篇
  2005年   1099篇
  2004年   1072篇
  2003年   1049篇
  2002年   1033篇
  2001年   1106篇
  2000年   778篇
  1999年   486篇
  1998年   372篇
  1997年   383篇
  1996年   397篇
  1995年   466篇
  1994年   396篇
  1993年   344篇
  1992年   376篇
  1991年   355篇
  1990年   326篇
  1989年   323篇
  1988年   297篇
  1987年   241篇
  1986年   248篇
  1985年   247篇
  1984年   279篇
  1983年   262篇
  1982年   269篇
  1981年   221篇
  1980年   165篇
  1979年   181篇
  1978年   162篇
  1977年   133篇
  1975年   137篇
  1973年   167篇
  1972年   143篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
51.
In a population of crested tits in Belgium, one out of three breeding males participated in nest-building. Since variation in the amount of nest-building among 11 building males was low, analysis of male nest-building allowed a logistic regression design. The probability of building increased with male condition and for late nests. The effect of male condition decreased with date, and date was the only factor predicting nest-building for repeat broods. The effect of male condition on nest-building suggests that building entails important costs for males. Based on correlative data, we argue that building by males shortens the interval between the start of nest-building and the onset of egg-laying by about 5 days. Since clutch size, incubation and nestling time did not differ between early and late broods, male nest-building apparently affects fledging date. Since early fledgers (early dispersers) are more likely to settle in future winter flocks, building behaviour by crested tit males should be favoured by natural selection. So far, male nest-building in hole-breeding birds might have been overlooked due to the widespread use of artificial nest-boxes in behavioural studies.  相似文献   
52.
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   
53.
54.
55.
56.
57.
58.
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   
59.
60.
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