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   97856篇
  免费   1234篇
  国内免费   1128篇
安全科学   3910篇
废物处理   3714篇
环保管理   14784篇
综合类   21487篇
基础理论   27241篇
环境理论   73篇
污染及防治   17968篇
评价与监测   5950篇
社会与环境   4488篇
灾害及防治   603篇
  2022年   856篇
  2021年   853篇
  2020年   665篇
  2019年   885篇
  2018年   1283篇
  2017年   1332篇
  2016年   2277篇
  2015年   1861篇
  2014年   2600篇
  2013年   9264篇
  2012年   2502篇
  2011年   3067篇
  2010年   3443篇
  2009年   3603篇
  2008年   2710篇
  2007年   2595篇
  2006年   2791篇
  2005年   2702篇
  2004年   2985篇
  2003年   2826篇
  2002年   2365篇
  2001年   2744篇
  2000年   2175篇
  1999年   1624篇
  1998年   1400篇
  1997年   1398篇
  1996年   1526篇
  1995年   1629篇
  1994年   1517篇
  1993年   1358篇
  1992年   1358篇
  1991年   1338篇
  1990年   1288篇
  1989年   1239篇
  1988年   1090篇
  1987年   1019篇
  1986年   1004篇
  1985年   1074篇
  1984年   1176篇
  1983年   1176篇
  1982年   1180篇
  1981年   1106篇
  1980年   948篇
  1979年   949篇
  1978年   840篇
  1977年   732篇
  1976年   649篇
  1974年   634篇
  1973年   668篇
  1972年   661篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
741.
742.
743.
744.
 The “Linh Duong” (Pseudonovibos spiralis), a newly described Vietnamese bovid, has been shown to be related to the Caprinae on the basis of the mitochondrial cytochrome b gene sequencing from horn fragments. To integrate the greatest available biodiversity we performed a new phylogenetic analysis including all genera of Caprinae. Unexpectedly, Pseudonovibos is found to be robustly associated with Rupicapra, and closer to the Alpine than to the Pyrenean chamois. Several clues led us to interpret this result as a carry-over DNA contamination of Pseudonovibos by Rupicapra. Received: 19 July 1999 / Accepted in revised form: 20 October 1999  相似文献   
745.
746.
Fisheries management is the practice of analyzing and selecting options to maintain or alter the structure, dynamics, and interaction of habitat, aquatic biota, and man to achieve human goals and objectives. The theory of fisheries management is: managers or decision makers attempt to maximize renewable `output' from an aquatic resource by choosing from among a set of decision options and applying a set of actions that generate an array of outputs. Outputs may be defined as a tangible catch, a fishing experience, an existence value, or anything else produced or supported by renewable aquatic resources. Overall output is always a mix of tangible and intangible elements. However defined, management goals and objectives are essential components of fisheries management or any other field of renewable natural resource management. Reaching consensus on management goals and objectives has never been a simple task. Beyond the broad and often conflicting goals of an agency, managers must decide who should set specific management objectives — agency personnel, the public, or a combination of the two. Historically, rhetoric aside, fisheries managers in North America nearly always have consulted with professionals in governmental roles to set management objectives. In a strongly pluralistic society, this often resulted in protracted political and legal conflict. Increasingly, there are calls for use of risk assessment to help solve such ecological policy and management problems commonly encountered in fisheries management. The basic concepts of ecological risk assessment may be simple, but the jargon and details are not. Risk assessment (and similar analytical tools) is a concept that has evoked strong reactions whenever it has been used. In spite of the difficulties of defining problems and setting management objectives for complex ecological policy questions, use of risk assessment to help solve ecological problems is widely supported. Ecological risk assessment will be most useful (and objective) in political deliberations when the policy debate revolves around largely technical concerns. To the extent that risk assessment forces policy debate and disagreement toward fundamental differences rather than superficial ones, it will be useful in decision making.  相似文献   
747.
748.
Dedicated to Prof. H. Autrum on the occasion of his 85th birthday.  相似文献   
749.
750.
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