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   17010篇
  免费   184篇
  国内免费   148篇
安全科学   478篇
废物处理   654篇
环保管理   2474篇
综合类   2616篇
基础理论   4626篇
环境理论   4篇
污染及防治   4457篇
评价与监测   1042篇
社会与环境   878篇
灾害及防治   113篇
  2022年   118篇
  2021年   137篇
  2020年   108篇
  2019年   156篇
  2018年   240篇
  2017年   231篇
  2016年   373篇
  2015年   254篇
  2014年   374篇
  2013年   1350篇
  2012年   463篇
  2011年   665篇
  2010年   567篇
  2009年   547篇
  2008年   722篇
  2007年   726篇
  2006年   693篇
  2005年   526篇
  2004年   608篇
  2003年   546篇
  2002年   505篇
  2001年   711篇
  2000年   485篇
  1999年   293篇
  1998年   246篇
  1997年   229篇
  1996年   238篇
  1995年   257篇
  1994年   279篇
  1993年   227篇
  1992年   255篇
  1991年   230篇
  1990年   259篇
  1989年   246篇
  1988年   199篇
  1987年   182篇
  1986年   163篇
  1985年   174篇
  1984年   199篇
  1983年   184篇
  1982年   194篇
  1981年   184篇
  1980年   142篇
  1979年   155篇
  1978年   135篇
  1977年   123篇
  1975年   120篇
  1974年   118篇
  1973年   112篇
  1972年   135篇
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
221.
222.
 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   
223.
 Chemical synapses are highly specialized cell–cell junctions designed for efficient signaling between nerve cells. Distinct cytoskeletal matrices are assembled at either side of the synaptic junction. The presynaptic cytomatrix at the active zone (CAZ) defines and organizes the site of neurotransmitter release from presynaptic nerve terminals. The postsynaptic density (PSD) tethers neurotransmitter receptors and the postsynaptic signal transduction machinery. Recent progress in the identification and characterization of novel CAZ and PSD components has revealed new insights into the molecular organization and assembly mechanisms of the synaptic neurotransmission apparatus. On the presynaptic side, Bassoon and Piccolo, two related giant proteins, are crucially involved in scaffolding the CAZ. On the postsynaptic side, two families of multi-domain adaptor proteins, the MAGuKs (membrane-associated guanylate kinase homologs) and the ProSAP (proline-rich synapse-associated protein, also termed Shank) family members are thought to be major organizing molecules of the PSD.  相似文献   
224.
Wir danken Dr. Kerndorff für die kritische Durchsicht des Manuskripts.  相似文献   
225.
We have determined the activity of alkaline phosphatase in chorionic villous tissue obtained in the first trimester of pregnancy, in order to obtain the normal range of values as a prerequisite for application to the prenatal diagnosis of the rare bone disease hypophosphatasia. The activities found were a combination of intestinal and liver/bone/kidney types; traces of placental type were present in only one sample.  相似文献   
226.
227.
228.
229.
230.
 The Mormon cricket, Anabrus simplex, is one of just a few species of katydids (or bushcrickets, Orthoptera: Tettigoniidae) that, like migratory locusts, appear to have solitary and migratory morphs. Using radio telemetry we studied movements of individuals of two morphs of this flightless species. Individuals within each migratory band had similar rates of movements along similar directional headings whereas solitary individuals moved little and showed little evidence of directionality in movement. Our results also add to other recent radio-telemetry studies showing that flightless insects of 1–2 g in mass can be tracked successfully using these methods. Received: 28 February 2000 / Accepted in revised form: 19 June 2000  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