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   108513篇
  免费   1272篇
  国内免费   1376篇
安全科学   4186篇
废物处理   4171篇
环保管理   16024篇
综合类   22486篇
基础理论   29085篇
环境理论   82篇
污染及防治   22707篇
评价与监测   6527篇
社会与环境   5152篇
灾害及防治   741篇
  2022年   924篇
  2021年   926篇
  2020年   717篇
  2019年   950篇
  2018年   1544篇
  2017年   1558篇
  2016年   2467篇
  2015年   1972篇
  2014年   2700篇
  2013年   9437篇
  2012年   3029篇
  2011年   3989篇
  2010年   3727篇
  2009年   3893篇
  2008年   3647篇
  2007年   3599篇
  2006年   3515篇
  2005年   3225篇
  2004年   3459篇
  2003年   3369篇
  2002年   2894篇
  2001年   3388篇
  2000年   2561篇
  1999年   1774篇
  1998年   1466篇
  1997年   1473篇
  1996年   1611篇
  1995年   1694篇
  1994年   1594篇
  1993年   1421篇
  1992年   1431篇
  1991年   1392篇
  1990年   1358篇
  1989年   1306篇
  1988年   1142篇
  1987年   1071篇
  1986年   1024篇
  1985年   1101篇
  1984年   1201篇
  1983年   1211篇
  1982年   1197篇
  1981年   1123篇
  1980年   975篇
  1979年   981篇
  1978年   859篇
  1977年   745篇
  1976年   677篇
  1974年   673篇
  1973年   692篇
  1972年   708篇
排序方式: 共有10000条查询结果,搜索用时 745 毫秒
291.
292.
   Global change, i.e. the mega-process radically transforming the relationship between nature and human civilization since the end of World War II, is investigated from the point of view of systems analysis. It is argued that this unbridled process should rather be domesticated by planetary control strategies transpiring from a new science called “geocybernetics”. The formal aspects of geocybernetic theory are sketched and illustrated in a tutorial theatre world reflecting the overall environment and development problematic. Within this setting a straightforward operationalization of the sweeping “sustainable development” ideal through a set of concise paradigms can be achieved. Evidence is provided that geocybernetics is actually feasible on the basis of earth system modelling and fuzzy-control techniques.  相似文献   
293.
294.
This paper examines the relationship between survivor reactions to a downsizing and retention subsequent to a downsizing. We hypothesize that survivors who experience the downsizing as distributively, procedurally, and interactionally just and who see top management as trustworthy will feel more attached to the organization because each reduces the threat inherent in downsizing. In addition, we hypothesize that survivors who feel empowered will also feel more attached to the organization because they feel better able to cope with the downsizing. We further hypothesize that those survivors who feel more attached to the organization following the downsizing will be more likely to remain with the organization in the coming year. The theoretical model is tested on a sample of aerospace employees who survived an organizational downsizing. The trustworthiness of management, distributive justice, procedural justice, and three dimensions of empowerment are found to facilitate more organizational attachment. Higher levels of attachment are found, in turn, to facilitate less voluntary turnover in the year following the downsizing. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   
295.
296.
Four microbial isolates, OP2, OP3, OP6, and OP7, of earthworm casts ofPontoscolex corethrurus were found to be acid tolerant actinomycetes and efficient rock phosphate (RP) solubilizers that could grow fast on NH4Cl-enriched or N-free carboxymethyl cellulose or glucose as sole carbon source. CMC (carboxymethyl cellulose) induced production of extracellular cellulase enzyme and the production of reducing sugar in all the isolates. RP solubilizing power was observed to be inversely related to glucose consumption. The most efficient RP solubilizer was found to consume the least glucose. Growth was faster on cellulose than on glucose media. N-free CMC induced greater glucose production than NH4Cl-enriched CMC medium. Both CMC and glucose media were acidified by all the isolates, however, RP solubilizing power decreased with acidification. Solubilization power was greatest with isolate OP7, which also produced the greatest amount of reducing sugar per gram CMC. Both RP solubilizing power and the cellulolytic efficiency varied among isolates. A minimum of 631 μg P/0.1 g RP and a maximum of 951.4 μg P/0.1 g RP was recorded.  相似文献   
297.
298.
299.
300.
Simplicity and efficiency in design and estimation are all important in deciding on sampling strategies. A simple model is given and illustrated for four practical situations to show how a good sampling strategy should be selected.The U.S. Government right to retain a non-exclusive, royalty free licence in and to any copyright is acknowledged.  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