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   2402篇
  免费   329篇
  2022年   26篇
  2021年   38篇
  2020年   20篇
  2019年   29篇
  2017年   25篇
  2016年   45篇
  2015年   63篇
  2014年   84篇
  2013年   95篇
  2012年   141篇
  2011年   117篇
  2010年   65篇
  2009年   72篇
  2008年   108篇
  2007年   107篇
  2006年   82篇
  2005年   85篇
  2004年   93篇
  2003年   100篇
  2002年   74篇
  2001年   70篇
  2000年   56篇
  1999年   43篇
  1997年   26篇
  1996年   30篇
  1995年   22篇
  1994年   20篇
  1993年   30篇
  1992年   63篇
  1991年   58篇
  1990年   52篇
  1989年   51篇
  1988年   65篇
  1987年   57篇
  1986年   46篇
  1985年   39篇
  1984年   26篇
  1983年   23篇
  1980年   22篇
  1979年   19篇
  1977年   21篇
  1976年   21篇
  1975年   19篇
  1974年   25篇
  1973年   24篇
  1972年   21篇
  1971年   32篇
  1968年   19篇
  1967年   18篇
  1966年   20篇
排序方式: 共有2731条查询结果,搜索用时 15 毫秒
121.
122.
We recommend routine fluorescein examination whenever a major flap is manipulated. It will depict those flaps which are dead at elevation, and it will allow us to critically evaluate the other factors which might have affected flap viability. The examination is safe when precautionary measures are taken.  相似文献   
123.
(+/-)-N-(n-propyl) amphetamine (I), a secondary amine, was readily metabolized by Cumminghamella echinulata. The products included known C- and N-oxygenated mammalian metabolites as well as N-acetylamphetamine and were identified by gas chromatography and mass spectrometry.  相似文献   
124.
125.
126.
Circumcision is often claimed to be simpler, safer and more cost-effective when performed in the neonatal period as opposed to later in life, with a greater benefit-to-risk ratio. In the first part of this paper, we critically examine the evidence base for these claims, and find that it is not as robust as is commonly assumed. In the second part, we demonstrate that, even if one simply grants these claims for the sake of argument, it still does not follow that neonatal circumcision is ethically permissible absent urgent medical necessity. Based on a careful consideration of the relevant evidence, arguments and counterarguments, we conclude that medically unnecessary penile circumcision—like other medically unnecessary genital procedures, such as ‘cosmetic’ labiaplasty—should not be performed on individuals who are too young (or otherwise unable) to provide meaningful consent to the procedure.  相似文献   
127.
Previous studies by other investigators have established that L-region methyl derivatives of dibenz[a,h]anthracene (DBA) were more carcinogenic than the parent hydrocarbon. The bioalkylation of DBA was investigated by incubating the hydrocarbon with rat liver cytosol fortified with S-adenosyl-L-methionine (SAM) in 0.1 M phosphate buffer (pH 7.4) for 1 h at 37 degrees C in air. The reaction was stopped by the addition of cold acetone and the mixture extracted with ethyl acetate and washed with water. The organic phase was evaporated and the residue dissolved in methylene chloride for analysis by reverse phase high performance liquid chromatography (HPLC) and gas chromatography/mass spectroscopy GC/MS. Products were found that were indistinguishable from 7-methyl-DBA and 7,14-dimethyl-DBA, 7-hydroxymethyl-DBA, 7-hydroxymethyl-14-methyl-DBA, and 7,14-dihydroxymethyl-DBA. The results suggest that unsubstituted carcinogenic hydrocarbons are preprocarcinogens that react with SAM in liver cytosol preparations, to form alkyl substituted procarcinogens, which are more potent than the corresponding preprocarcinogens.  相似文献   
128.
129.
130.
Coral Reefs - A correction to this paper has been published: https://doi.org/10.1007/s00338-021-02121-x  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