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   89608篇
  免费   1268篇
  国内免费   1269篇
安全科学   3665篇
废物处理   3314篇
环保管理   13646篇
综合类   21429篇
基础理论   26229篇
环境理论   74篇
污染及防治   14057篇
评价与监测   5437篇
社会与环境   3777篇
灾害及防治   517篇
  2022年   894篇
  2021年   891篇
  2020年   687篇
  2019年   899篇
  2018年   1235篇
  2017年   1231篇
  2016年   2248篇
  2015年   1895篇
  2014年   2678篇
  2013年   9422篇
  2012年   2205篇
  2011年   2396篇
  2010年   3313篇
  2009年   3431篇
  2008年   1904篇
  2007年   1732篇
  2006年   2146篇
  2005年   2188篇
  2004年   2438篇
  2003年   2278篇
  2002年   1810篇
  2001年   2058篇
  2000年   1862篇
  1999年   1450篇
  1998年   1358篇
  1997年   1346篇
  1996年   1473篇
  1995年   1568篇
  1994年   1453篇
  1993年   1313篇
  1992年   1292篇
  1991年   1267篇
  1990年   1217篇
  1989年   1189篇
  1988年   1019篇
  1987年   972篇
  1986年   984篇
  1985年   1057篇
  1984年   1151篇
  1983年   1159篇
  1982年   1172篇
  1981年   1093篇
  1980年   936篇
  1979年   909篇
  1978年   815篇
  1977年   711篇
  1976年   638篇
  1975年   593篇
  1973年   619篇
  1972年   622篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
701.
702.
703.
704.
 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   
705.
706.
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   
707.
708.
Dedicated to Prof. H. Autrum on the occasion of his 85th birthday.  相似文献   
709.
710.
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