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   33593篇
  免费   436篇
  国内免费   301篇
安全科学   1200篇
废物处理   1583篇
环保管理   4961篇
综合类   4902篇
基础理论   8775篇
环境理论   15篇
污染及防治   8105篇
评价与监测   2366篇
社会与环境   2194篇
灾害及防治   229篇
  2023年   174篇
  2022年   301篇
  2021年   363篇
  2020年   240篇
  2019年   292篇
  2018年   541篇
  2017年   567篇
  2016年   853篇
  2015年   629篇
  2014年   979篇
  2013年   2781篇
  2012年   1178篇
  2011年   1570篇
  2010年   1268篇
  2009年   1331篇
  2008年   1609篇
  2007年   1534篇
  2006年   1384篇
  2005年   1227篇
  2004年   1166篇
  2003年   1102篇
  2002年   1047篇
  2001年   1161篇
  2000年   845篇
  1999年   538篇
  1998年   421篇
  1997年   428篇
  1996年   452篇
  1995年   524篇
  1994年   456篇
  1993年   395篇
  1992年   423篇
  1991年   387篇
  1990年   358篇
  1989年   353篇
  1988年   320篇
  1987年   277篇
  1986年   281篇
  1985年   281篇
  1984年   305篇
  1983年   293篇
  1982年   315篇
  1981年   259篇
  1980年   195篇
  1979年   194篇
  1978年   188篇
  1977年   147篇
  1975年   143篇
  1973年   168篇
  1972年   148篇
排序方式: 共有10000条查询结果,搜索用时 328 毫秒
91.
92.
A method for estimating the current state of plant communities based on the ecological amplitudes of constituent species is proposed. An original program, Fitoindikatsiya, has been developed to compute the indices of disturbance and homogeneity of plant communities from species ecological scale values. The current state of pine forests in the part of Novosibirsk oblast east of the Ob River has been analyzed; slightly, moderately, and severely disturbed zones have been distinguished.  相似文献   
93.
94.
95.
96.
97.
98.
99.
In this article the authors assert that successful long-term pollution prevention will require changes in the culture and business practices of an organization such that the term “pollution prevention” eventually becomes obsolete. They envision firms evolving to a point where actions that today are referred to as pollution prevention will simply be part of standard business practices and thoroughly embedded in the firms' culture. Although pollution prevention projects and programs need to be highly visible at the outset to communicate throughout the organization and to demonstrate the benefits that can be gained, companies should adopt a long-term strategy aimed at making fundamental changes in the way they do business, rather than relying solely on piecemeal projects and special plans or programs. Such evolution of the firm will maximize the chances of meeting the dual challenges of business competitiveness and environmental stewardship. This article presents a vision for integrating environmental performance with business objectives and suggests practical steps to begin moving toward that vision.  相似文献   
100.
The effects of food availability, female size, and social interactions on the quality of Pomacentrus amboinensis larvae at hatching were examined using two field-based experiments. In Experiment 1, food availability and female size significantly influenced size, eye diameter and levels of yolk reserves of larvae at hatching. Small females (47 to 52 mm standard length, SL) whose diets were not supplemented, produced the longest larvae (3.0 ± 0.01 mm total length, TL) with the least yolk reserves (50.1 ± 1.04 μm2). Irrespective of female size, those that received additional food produced larvae with the largest yolk-sacs (large females: 87.60 ± 1.53 μm2; small females: 80.14 ± 1.24 μm2). In Experiment 2, interactions with conspecifics had a greater affect on the somatic development of larvae at hatching than food availability. Increased social interactions resulted in larvae that were ⋍3% longer, with 2% greater head depth, than larvae from females that spawned in isolation on the experimental reefs. Fed females produced larvae with ⋍20% more yolk than larvae from females whose diets were not supplemented. All three factors (food availability, female size, and intensity of social interactions) tested within these experiments vary spatially and temporally among reefs. There is the potential, therefore, for larvae at the onset of the planktonic stage to vary in quality, level of development, and probability of survival. Received: 12 August 1996 / Accepted: 26 August 1996  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