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   96943篇
  免费   1254篇
  国内免费   1312篇
安全科学   3855篇
废物处理   3721篇
环保管理   14537篇
综合类   21766篇
基础理论   27208篇
环境理论   76篇
污染及防治   17564篇
评价与监测   5930篇
社会与环境   4273篇
灾害及防治   579篇
  2022年   918篇
  2021年   920篇
  2020年   707篇
  2019年   923篇
  2018年   1365篇
  2017年   1334篇
  2016年   2367篇
  2015年   1912篇
  2014年   2701篇
  2013年   9433篇
  2012年   2574篇
  2011年   3021篇
  2010年   3468篇
  2009年   3592篇
  2008年   2605篇
  2007年   2499篇
  2006年   2701篇
  2005年   2580篇
  2004年   2823篇
  2003年   2734篇
  2002年   2217篇
  2001年   2636篇
  2000年   2197篇
  1999年   1601篇
  1998年   1390篇
  1997年   1386篇
  1996年   1520篇
  1995年   1611篇
  1994年   1499篇
  1993年   1351篇
  1992年   1349篇
  1991年   1305篇
  1990年   1271篇
  1989年   1225篇
  1988年   1052篇
  1987年   1001篇
  1986年   994篇
  1985年   1075篇
  1984年   1161篇
  1983年   1175篇
  1982年   1174篇
  1981年   1095篇
  1980年   953篇
  1979年   922篇
  1978年   826篇
  1977年   712篇
  1976年   638篇
  1975年   607篇
  1973年   630篇
  1972年   643篇
排序方式: 共有10000条查询结果,搜索用时 890 毫秒
271.
272.
   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   
273.
274.
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   
275.
276.
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   
277.
278.
279.
280.
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