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   103325篇
  免费   2090篇
  国内免费   6471篇
安全科学   4900篇
废物处理   4114篇
环保管理   14919篇
综合类   30230篇
基础理论   28248篇
环境理论   73篇
污染及防治   18177篇
评价与监测   5966篇
社会与环境   4057篇
灾害及防治   1202篇
  2023年   653篇
  2022年   1538篇
  2021年   1481篇
  2020年   1208篇
  2019年   1339篇
  2018年   1680篇
  2017年   1826篇
  2016年   2754篇
  2015年   2680篇
  2014年   3831篇
  2013年   10779篇
  2012年   3442篇
  2011年   3620篇
  2010年   4352篇
  2009年   4457篇
  2008年   3028篇
  2007年   2611篇
  2006年   3088篇
  2005年   2764篇
  2004年   2878篇
  2003年   2746篇
  2002年   2291篇
  2001年   2429篇
  2000年   2333篇
  1999年   1814篇
  1998年   1652篇
  1997年   1660篇
  1996年   1734篇
  1995年   1776篇
  1994年   1627篇
  1993年   1458篇
  1992年   1426篇
  1991年   1342篇
  1990年   1297篇
  1989年   1216篇
  1988年   1044篇
  1987年   988篇
  1986年   1003篇
  1985年   1068篇
  1984年   1155篇
  1983年   1170篇
  1982年   1180篇
  1981年   1102篇
  1980年   936篇
  1979年   914篇
  1978年   817篇
  1977年   710篇
  1976年   636篇
  1973年   627篇
  1972年   626篇
排序方式: 共有10000条查询结果,搜索用时 265 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