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   454563篇
  免费   41095篇
  国内免费   993篇
  2018年   14559篇
  2017年   13240篇
  2016年   11563篇
  2015年   6818篇
  2014年   7698篇
  2013年   10512篇
  2012年   15957篇
  2011年   24561篇
  2010年   19537篇
  2009年   15502篇
  2008年   20286篇
  2007年   22007篇
  2006年   11301篇
  2005年   11215篇
  2004年   11610篇
  2003年   11139篇
  2002年   10758篇
  2001年   18392篇
  2000年   18235篇
  1999年   14227篇
  1998年   5013篇
  1997年   4990篇
  1996年   4632篇
  1995年   4237篇
  1994年   4184篇
  1993年   4225篇
  1992年   11076篇
  1991年   10982篇
  1990年   10397篇
  1989年   10281篇
  1988年   9537篇
  1987年   8903篇
  1986年   8016篇
  1985年   7985篇
  1984年   6570篇
  1983年   5723篇
  1982年   4337篇
  1981年   3951篇
  1980年   3708篇
  1979年   5848篇
  1978年   4676篇
  1977年   4278篇
  1976年   3834篇
  1975年   4193篇
  1974年   4450篇
  1973年   4338篇
  1972年   3957篇
  1971年   3733篇
  1970年   3114篇
  1969年   3019篇
排序方式: 共有10000条查询结果,搜索用时 140 毫秒
991.
992.
Synopsis Experiments were carried out to study the feeding rates of the predator fish Therapon jarbua (Forsk) on mullet juveniles, before and after treatment with DDT. Mullet juveniles treated with a subacute concentration, were refused by the control predators, whereas predators treated with a subacute concentration consumed more mullet juveniles. In the present study crescent perch T. jarbua were exposed to subacute and acute concentrations of DDT, and their behaviour was compared with that of the control predators. There were changes in oriented behaviour and co-ordinated movements, and in feeding, aggression and comfort behaviour of the fish. Inflammation in the gills, and caudal fin serration, were noticed in treated fishes. The findings presented here throw light on fundamental pathways by which pollutants interact with the behaviour of fishes.  相似文献   
993.
Book reviews     
Environmental Biology of Fishes -  相似文献   
994.
995.
996.
Stroma-free haemolysates of red cells from patients with acute or latent anaemia inhibit the NADH oxidase activity of submitochondrial particles from beef heart. The inhibitory activities appeared significantly more frequently in anaemic patients than in normal persons and are likely due to the action of a factor which is identical or similar to the inhibitory protein RF present in rabbit reticulocytes. The possible use of the inhibitor assay for clinical purpose is under discussion.  相似文献   
997.
998.
999.
Organ cultures of newborn rat lungs synthesize and accumulate DNA, RNA, collagen and noncollagenous proteins almost at a linear rate for at least 5 days. During this period the synthesis of collagen consistently exceeds the synthesis of noncollagenous proteins in a pattern similar to neonatal lung growth in vivo. Although some morphological characteristics of lung architecture are distorted after culture, fundamental structural similarities to lungs growing in intact animals are retained. When these cultures are maintained in atmospheres rich in oxygen, increased collagen synthesis is observed, a response similar to that of lungs in intact animals exposed to high oxygen concentrations in vivo. Our studies suggest that lung organ cultures may be a suitable system for investigating the biochemical aspects of lung tissue-environmental interaction. These studies were supported in parts by NIH Grant HL-19668, a contract (68-03-2005) from the U.S. Environmental Protection Agency, and grants from the California Lung Association.  相似文献   
1000.
Reaction of [Pd(1-3-η-allyl)Cl]2 with lithium triazenide (triazenide = p-XC6H4NN-NC6H4X-p; X = Cl, H, CH3) affords dimeric complexes of the type [Pd(1-3-η-allyl)(triazenide)]2. In the solid state the triazenido ligands are bridging two palladium atoms with their terminal nitrogen atoms, as shown by a preliminary X-ray determination of the complex with X = CH3. The allyl groups are stereochemically equivalent. 1H NMR spectra demonstrate the presence of two conformers in solution. The major component has the same configuration found in the solid. The other conformer has stereochemically non equivalent allyl groups. The concentration ratio of the two conformers is independent of the temperature, suggesting the absence of intramolecular processes and of palladium- triazenido bond breaking. This point is discussed also by comparing the (1-3-η-allyl)(triazenide)palladium (II) dimers with the closely related(1-3-η-allyl)(acetate)palladium(II) complexes.  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