全文获取类型
收费全文 | 86024篇 |
免费 | 1217篇 |
国内免费 | 1065篇 |
专业分类
安全科学 | 3645篇 |
废物处理 | 3124篇 |
环保管理 | 13284篇 |
综合类 | 20894篇 |
基础理论 | 25640篇 |
环境理论 | 71篇 |
污染及防治 | 12503篇 |
评价与监测 | 5177篇 |
社会与环境 | 3470篇 |
灾害及防治 | 498篇 |
出版年
2022年 | 786篇 |
2021年 | 784篇 |
2020年 | 636篇 |
2019年 | 850篇 |
2018年 | 1069篇 |
2017年 | 1104篇 |
2016年 | 2097篇 |
2015年 | 1810篇 |
2014年 | 2556篇 |
2013年 | 9205篇 |
2012年 | 1993篇 |
2011年 | 2086篇 |
2010年 | 3172篇 |
2009年 | 3298篇 |
2008年 | 1618篇 |
2007年 | 1406篇 |
2006年 | 1944篇 |
2005年 | 2025篇 |
2004年 | 2301篇 |
2003年 | 2163篇 |
2002年 | 1702篇 |
2001年 | 1943篇 |
2000年 | 1813篇 |
1999年 | 1421篇 |
1998年 | 1342篇 |
1997年 | 1330篇 |
1996年 | 1452篇 |
1995年 | 1541篇 |
1994年 | 1447篇 |
1993年 | 1298篇 |
1992年 | 1282篇 |
1991年 | 1255篇 |
1990年 | 1208篇 |
1989年 | 1177篇 |
1988年 | 1017篇 |
1987年 | 959篇 |
1986年 | 983篇 |
1985年 | 1050篇 |
1984年 | 1146篇 |
1983年 | 1162篇 |
1982年 | 1167篇 |
1981年 | 1089篇 |
1980年 | 936篇 |
1979年 | 907篇 |
1978年 | 813篇 |
1977年 | 708篇 |
1976年 | 630篇 |
1975年 | 590篇 |
1973年 | 618篇 |
1972年 | 622篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
Effect of periphyton grazing by Hydrobia ulvae on the growth of Zostera noltii on a tidal flat in the Dutch Wadden Sea 总被引:3,自引:0,他引:3
C. J. M. Philippart 《Marine Biology》1995,122(3):431-437
The decrease of the intertidal seagrass Zostera noltii in the Dutch Wadden Sea may have been the result of enhanced periphyton load due to eutrophication. Decrease of this seagrass species coincided with an increase in the mudsnail Hydrobia ulvae. Feeding of this mudsnail on periphyton may have partly counteracted an increase of periphyton biomass. Exclosure experiments on seagrass stands in the Dutch Wadden Sea in 1987 showed that density of periphyton on leaves of Z. noltii decreased significantly with increasing density of grazers. An increased density of mudsnails significantly enhanced the density and biomass of seagrass, in particular of the below ground parts. Since this seagrass species survives winter in temperate climate zones mainly by means of rhizomes, grazing may also influence the seagrass dynamics in the long term. Results of the experiment were in agreement with field observations on coinciding low densities of mudsnails and high densities of fouling of seagrass stands on the tidal flats of western Wadden Sea in the late 1970s. 相似文献
63.
64.
65.
66.
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
67.
68.
69.
70.
David W. Mehlman 《Conservation biology》1994,8(4):1141-1145