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   41440篇
  免费   444篇
  国内免费   347篇
安全科学   1252篇
废物处理   1915篇
环保管理   5403篇
综合类   7324篇
基础理论   10425篇
环境理论   14篇
污染及防治   10160篇
评价与监测   2858篇
社会与环境   2662篇
灾害及防治   218篇
  2022年   348篇
  2021年   404篇
  2020年   240篇
  2019年   323篇
  2018年   599篇
  2017年   607篇
  2016年   956篇
  2015年   705篇
  2014年   1090篇
  2013年   3246篇
  2012年   1302篇
  2011年   1776篇
  2010年   1439篇
  2009年   1531篇
  2008年   1822篇
  2007年   1807篇
  2006年   1623篇
  2005年   1406篇
  2004年   1409篇
  2003年   1351篇
  2002年   1262篇
  2001年   1526篇
  2000年   1034篇
  1999年   687篇
  1998年   491篇
  1997年   534篇
  1996年   571篇
  1995年   610篇
  1994年   566篇
  1993年   499篇
  1992年   510篇
  1991年   509篇
  1990年   471篇
  1989年   454篇
  1988年   416篇
  1987年   362篇
  1986年   363篇
  1985年   362篇
  1984年   394篇
  1983年   389篇
  1982年   398篇
  1981年   343篇
  1980年   279篇
  1979年   285篇
  1978年   268篇
  1977年   232篇
  1975年   228篇
  1974年   224篇
  1973年   244篇
  1972年   216篇
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
521.
522.
523.
524.
 There are numerous reports of invertebrates that are visual mimics of ants, but no formal reports of mimicry of an ant, by an ant. Two endemic Australian ants, Myrmecia fulvipes and Camponotus bendigensis are remarkably similar in colour and size; both are generally black but have red legs and golden gasters. The density and hue of the pubescence of each ant's gaster are relatively uncommon in ants, but are very rare when combined with the black forebody and red legs. The ants are similarly sized but are smaller than other species closely related to M. fulvipes. The range of C. bendigensis lies entirely within that of M. fulvipes, and both species excavate ground nests in open woodland. Finally, workers of both species are crepuscular and forage solitarily. These data suggest that the relatively benign formicine C. bendigensis is a Batesian mimic of the formidable myrmeciine M. fulvipes. Received: 9 August 1999 / Accepted in revised form: 22 December 1999  相似文献   
525.
Pesticide use in agriculture can cause undesirable effects on humans and the natural environment. One of the objectives of integrated agriculture is the elimination or reduction of possible sources of environmental pollution such as pesticides. To achieve this objective, farmers need a method to assist them in estimating the environmental impact of pesticide use. This paper addresses a two-part question: what factors should be taken into consideration to assess pesticide environmental impact, and how can impact be quantified? As the environmental impact of a pesticide depends on its dispersion in the environment and on its toxicological properties, the literature on these topics is reviewed to address the first part of the question. To address the second part of the question, six recent approaches to assess the impact of pesticides on the environment are compared regarding choice, transformation and aggregation of input parameters. The use of simulation models to assess environmental impact is discussed.  相似文献   
526.
527.
 The ubiquity of circadian rhythms suggests that they have an intrinsic adaptive value (Ouyang et al. 1998; Ronneberg and Foster 1997). Some experiments have shown that organisms have enhanced longevity, development time or growth rates when maintained in environments whose periodicity closely matches their endogenous period (Aschoff et al. 1971; Highkin and Hanson 1954; Hillman 1956; Pittendrigh and Minis 1972; Went 1960). So far there has been no experimental evidence to show that circadian rhythms per se (i.e. periodicity itself, as opposed to phasing properties of a rhythm) confer a fitness advantage. We show that the circadian eclosion rhythm persists in a population of the fruitfly Drosophila melanogaster maintained in constant conditions of light, temperature, and humidity for over 600 generations. The results suggest that even in the absence of any environmental cycle there exists some intrinsic fitness value of circadian rhythms. Received: 2 November 1998 / Accepted in revised form: 22 April 1999  相似文献   
528.
529.
530.
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