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   567408篇
  免费   58779篇
  国内免费   416篇
  626603篇
  2016年   5903篇
  2015年   7615篇
  2014年   9324篇
  2013年   13289篇
  2012年   14886篇
  2011年   15467篇
  2010年   10506篇
  2009年   9772篇
  2008年   13871篇
  2007年   14568篇
  2006年   13737篇
  2005年   13277篇
  2004年   13359篇
  2003年   12850篇
  2002年   12822篇
  2001年   25277篇
  2000年   26010篇
  1999年   20336篇
  1998年   6728篇
  1997年   7010篇
  1996年   6425篇
  1995年   6184篇
  1994年   6028篇
  1993年   6062篇
  1992年   16675篇
  1991年   16492篇
  1990年   16026篇
  1989年   15652篇
  1988年   14698篇
  1987年   13990篇
  1986年   13084篇
  1985年   13356篇
  1984年   10978篇
  1983年   9412篇
  1982年   7130篇
  1981年   6579篇
  1980年   6142篇
  1979年   10615篇
  1978年   8587篇
  1977年   7807篇
  1976年   7347篇
  1975年   8408篇
  1974年   9347篇
  1973年   9241篇
  1972年   8625篇
  1971年   7796篇
  1970年   6743篇
  1969年   6617篇
  1968年   6097篇
  1967年   5271篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
971.
Plasma choline concentrations were measured in humans, rats, and rabbits within the first few hours of life, before any food was ingested. Neonatal animals and humans had markedly elevated plasma choline levels compared to adult animals or humans. Possible mechanisms responsible for this elevation are discussed and possible consequences for brain function, lung function, and growth are presented.  相似文献   
972.
973.
Results are presented from experimental investigations of the angular distributions and energy spectra of fast ions produced in deuterium polyethylene targets under irradiation by picosecond laser pulses with intensities of up to 2 × 1018 W/cm2 in the SOKOL-P facility. The parameters of ion fluxes were measured by time-of-flight spectrometers based on semiconductor detectors.  相似文献   
974.
975.
976.
977.
978.
979.
The quality of milk products is threatened by the formation of biofilms of thermophilicstreptococci on the internal surfaces of plate heat exchangers used in milk processing. Althoughattachment to stainless steel surfaces is one of the first stages in the development of a biofilm, themechanisms involved in attachment have not been reported. The cell surface properties of 12strains of thermophilic streptococci were examined to determine their importance in attachment tostainless steel surfaces. Hydrophobicity, extracellular polysaccharide production and cell surfacecharge varied between the different strains but could not be related to numbers attaching. Treatingthe cells with sodium metaperiodate, lysozyme or trichloroacetic acid to disrupt cell surfacepolysaccharide had no effect on attachment. Treatment with trypsin or sodium dodecyl sulphate toremove cell surface proteins resulted in a 100-fold reduction in the number of bacteria attaching.This result suggests that the surface proteins of the thermophilic streptococci are important intheir attachment to stainless steel.  相似文献   
980.
We have reviewed the evidence in favor of a prostaglandin mediator of the thermal responses in fever and found that PGE injected into the hypothalamus does not always cause fever, that cerebrospinal fluid concentrations of PGE are not reliable reflections of hypothalamic events, and that antipyretic drugs may act in ways other than inhibiting PGE synthesis. Fever is not blocked by prostaglandin antagonists, nor by ablation of PGE-sensitive areas of the brain. There is poor correlation between the effects of pyrogens and of PGE on cerebral neurons. There is evidence that at least one prostanoid other than prostaglandin is a mediator of fever, but the prostanoid has not been identified yet. We conclude that PGE may contribute to the neural responses in fever but is not essential.  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