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   11575篇
  免费   92篇
  国内免费   276篇
安全科学   218篇
废物处理   546篇
环保管理   1276篇
综合类   1764篇
基础理论   3572篇
污染及防治   2576篇
评价与监测   804篇
社会与环境   1138篇
灾害及防治   49篇
  2023年   61篇
  2022年   135篇
  2021年   111篇
  2020年   69篇
  2019年   103篇
  2018年   259篇
  2017年   272篇
  2016年   415篇
  2015年   210篇
  2014年   274篇
  2013年   729篇
  2012年   703篇
  2011年   584篇
  2010年   346篇
  2009年   381篇
  2008年   451篇
  2007年   468篇
  2006年   378篇
  2005年   860篇
  2004年   1020篇
  2003年   852篇
  2002年   313篇
  2001年   376篇
  2000年   234篇
  1999年   147篇
  1998年   90篇
  1997年   92篇
  1996年   111篇
  1995年   137篇
  1994年   100篇
  1993年   87篇
  1992年   95篇
  1991年   98篇
  1990年   83篇
  1989年   77篇
  1988年   69篇
  1987年   75篇
  1986年   52篇
  1985年   63篇
  1984年   64篇
  1983年   59篇
  1982年   58篇
  1981年   64篇
  1980年   47篇
  1979年   47篇
  1977年   38篇
  1976年   36篇
  1974年   36篇
  1973年   44篇
  1972年   55篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
 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   
124.
125.
126.
127.
128.
Mitigation and adaptation synergy in forest sector   总被引:1,自引:1,他引:1  
Mitigation and adaptation are the two main strategies to address climate change. Mitigation and adaptation have been considered separately in the global negotiations as well as literature. There is a realization on the need to explore and promote synergy between mitigation and adaptation while addressing climate change. In this paper, an attempt is made to explore the synergy between mitigation and adaptation by considering forest sector, which on the one hand is projected to be adversely impacted under the projected climate change scenarios and on the other provide opportunities to mitigate climate change. Thus, the potential and need for incorporating adaptation strategies and practices in mitigation projects is presented with a few examples. Firstly, there is a need to ensure that mitigation programs or projects do not increase the vulnerability of forest ecosystems and plantations. Secondly, several adaptation practices could be incorporated into mitigation projects to reduce vulnerability. Further, many of the mitigation projects indeed reduce vulnerability and promote adaptation, for example; forest and biodiversity conservation, protected area management and sustainable forestry. Also, many adaptation options such as urban forestry, soil and water conservation and drought resistant varieties also contribute to mitigation of climate change. Thus, there is need for research and field demonstration of synergy between mitigation and adaptation, so that the cost of addressing climate change impacts can be reduced and co-benefits increased.  相似文献   
129.
活性氮和世界:200年的变化   总被引:101,自引:0,他引:101  
本文通过将19世纪后期和20世纪后期的氮流动情况进行对比,分析了食物和能源生产对全球氮循环的影响.我们虽然对人类产生的活性氮的数量及其释放到环境所产生的主要影响有了充分的认识,但是,我们对于环境库中氮的累积速度缺乏了解,由于积累在环境中的氮具有阶式效应,因此,对其在环境中的积累尚有不明之处.未来活性氮的产生、分布状况及其形成速度增加的可能性(尤其是在亚洲)存在巨大的区域性差异,因而需要制定"总活性氮措施",以优化食物和能源生产,保护环境系统.  相似文献   
130.
The integrity of social insect colonies is maintained by members recognising and responding to the chemical cues present on the cuticle of any intruder. Nevertheless, myrmecophiles use chemical mimicry to gain access to these nests, and their mimetic signals may be acquired through biosynthesis or through contact with the hosts or their nest material. The cuticular hydrocarbon profile of the myrmecophilous salticid spider Cosmophasis bitaeniata closely resembles that of its host ant Oecophylla smaragdina. Here, we show that the chemical resemblance of the spider does not arise through physical contact with the adult ants, but instead the spider acquires the cuticular hydrocarbons by eating the ant larvae. More significantly, we show that the variation in the cuticular hydrocarbon profiles of the spider depends upon the colony of origin of the ant larvae prey, rather than the parentage of the spider.  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