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   770925篇
  免费   87733篇
  国内免费   881篇
  859539篇
  2018年   6874篇
  2017年   6778篇
  2016年   9396篇
  2015年   13132篇
  2014年   15255篇
  2013年   21613篇
  2012年   24910篇
  2011年   25453篇
  2010年   16979篇
  2009年   15636篇
  2008年   22715篇
  2007年   23219篇
  2006年   22029篇
  2005年   20996篇
  2004年   20943篇
  2003年   19899篇
  2002年   19352篇
  2001年   32992篇
  2000年   33176篇
  1999年   26767篇
  1998年   9966篇
  1997年   10141篇
  1996年   9772篇
  1995年   9066篇
  1994年   8984篇
  1993年   8876篇
  1992年   22524篇
  1991年   22081篇
  1990年   21701篇
  1989年   21296篇
  1988年   19596篇
  1987年   18604篇
  1986年   17533篇
  1985年   17456篇
  1984年   14335篇
  1983年   12487篇
  1982年   9521篇
  1981年   8549篇
  1980年   8102篇
  1979年   13694篇
  1978年   10852篇
  1977年   9754篇
  1976年   9286篇
  1975年   10373篇
  1974年   11098篇
  1973年   10904篇
  1972年   9823篇
  1971年   8909篇
  1970年   7680篇
  1969年   7350篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
We have identified a C-insertion polymorphism in the 5'UTR of the first exon of the human tumor necrosis factor alpha (TNFA) gene. TNFA is a cytokine that plays an important role in the inflammatory response.  相似文献   
993.
The RAD6 gene of Saccharomyces cerevisiae, which encodes a ubiquitin-conjugating enzyme, is required for DNA repair, DNA damage-induced mutagenesis and sporulation. To evaluate the biological relevance of the thioester adduct between RAD6 protein and ubiquitin, formed as an obligatory, transient intermediate during ubiquitin conjugation to substrates, we altered cysteine 88 in RAD6 to serine. Esterification with ubiquitin occurs at serine 88 in the mutant protein, but conjugation of ubiquitin to the test substrate histone H2A is inactivated. Phenotypically, strains harboring the rad6 Ser88 allele are indistinguishable from rad6 deletion (rad6 delta) mutant cells. These findings argue against ligation of ubiquitin at cysteine 88 acting as a functional switch of a cryptic biochemical activity in RAD6.  相似文献   
994.
Serum proteins [molecular weight (MW) > 10,000] are essential for increased insulin-stimulated glucose transport after in vitro muscle contractions. We investigated the role of the kallikrein-kininogen system, including bradykinin, which is derived from kallikrein (MW > 10,000)-catalyzed degradation of serum protein kininogen (MW > 10,000), on this contraction effect. In vitro electrical stimulation of rat epitrochlearis muscles was performed in 1) rat serum +/- kallikrein inhibitors; 2) human plasma (normal or kallikrein-deficient); 3) rat serum +/- bradykinin receptor-2 inhibitors; or 4) serum-free buffer +/- bradykinin. 3-O-methylglucose transport (3-MGT) was measured 3.5 h later. Serum +/- kallikrein inhibitors tended (P = 0.08) to diminish postcontraction insulin-stimulated 3-MGT. Contractions in normal plasma enhanced insulin-stimulated 3-MGT vs. controls, but contractions in kallikrein-deficient plasma did not. Supplementing rat serum with bradykinin receptor antagonist HOE-140 during contraction did not alter insulin-stimulated 3-MGT. Muscles stimulated to contract in serum-free buffer plus bradykinin did not have enhanced insulin-stimulated 3-MGT. Bradykinin was insufficient for postcontraction-enhanced insulin sensitivity. However, results with kallikrein inhibitors and kallikrein-deficient plasma suggest kallikrein plays a role in this improved insulin action.  相似文献   
995.
996.
997.
Immersion staining of coarse fish in the Thames   总被引:1,自引:0,他引:1  
Thirty-one vital dyes were screened for marking bleak, roach and gudgeon by total body immersion in aqueous solutions of the dye. Only six dyes stained without killing, and of these Nile blue, neutral red and Bismarck brown were used successfully in the field. This approach to estimation of population size was abandoned because (1) the toxicity of the dyes varied at different times of year, (2) the numbers needed for release were impractically high and (3) fingerlings showed extremely high mortality on handling.  相似文献   
998.
999.
A study was made of the dose-time relationship during chromatin degradation in white blood cells of non-irradiated and irradiated rats. There was a linear increase in the release of PDN from leukocytes 1,2 and 3 days after irradiation (1-3 Gy) followed by the deceleration of the chromatin degradation at doses exceeding 3 Gy.  相似文献   
1000.
Dealing with patients'' sex-related complaints is uncomfortable for many physicians. It can become more comfortable if the physician learns to apply his or her clinical knowledge of sexuality in combination with specific interpersonal interviewing skills. The level of comfort can be increased if the physician accepts his or her professional limitations in providing therapy and knows what other sources of care are available.  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