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   50462篇
  免费   4193篇
  国内免费   8篇
  54663篇
  2023年   237篇
  2021年   381篇
  2020年   330篇
  2019年   315篇
  2018年   954篇
  2017年   994篇
  2016年   1092篇
  2015年   1041篇
  2014年   1259篇
  2013年   2103篇
  2012年   3402篇
  2011年   3796篇
  2010年   1989篇
  2009年   1306篇
  2008年   3103篇
  2007年   3177篇
  2006年   2953篇
  2005年   2676篇
  2004年   2550篇
  2003年   2411篇
  2002年   2400篇
  2001年   1658篇
  2000年   1916篇
  1999年   1056篇
  1998年   503篇
  1997年   392篇
  1996年   467篇
  1995年   402篇
  1994年   436篇
  1993年   377篇
  1992年   466篇
  1991年   414篇
  1990年   378篇
  1989年   330篇
  1988年   343篇
  1987年   318篇
  1986年   275篇
  1985年   377篇
  1984年   437篇
  1983年   376篇
  1982年   357篇
  1981年   338篇
  1980年   286篇
  1979年   317篇
  1978年   297篇
  1977年   286篇
  1976年   273篇
  1975年   320篇
  1974年   250篇
  1973年   242篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
Elevated levels of intracellular calcium are a major cause of myocardial dysfunction. To find possible mediators of the deregulated calcium we searched for EF-hand calcium-binding proteins of the S100 family. By PCR technology we identified three members of the S100 protein family (S100 alpha, CACY, and CAPL) in the human heart. We cloned the corresponding cDNAs and examined their expression levels in various human tissues by Northern blot analysis. All three proteins are expressed at high levels in the human heart. Whereas CACY and CAPL mRNAs are expressed ubiquitously, S100 alpha mRNA is restricted to heart, skeletal muscle, and brain. Interestingly, the expression pattern of S100 alpha, CACY, and CAPL in human tissues differs significantly from that in rodent tissues.  相似文献   
3.
4.
5.
6.
In a section of the Liassic southwest of the village of Préjano (Prov. Logroño) Sinemurian Dasyclad algae were found for the first time in the “Bankkalk-Series” of the “Carniolas-Formation” which is not dated up to that time. Six species,Dissocladella lucasi (Cros & Lemoine),Dissocladella iberica nov. sp.,Dissocladella ebroensis nov. sp.,Sestrosphaera liasina Pia,Gyroporella retica (Zanin) andMacroporella nov. sp. aff. sturi Bystricky are described.  相似文献   
7.
S-Protein/vitronectin is a serum glycoprotein that inhibits the lytic activity of the membrane attack complex of complement, i.e., of the complex including the proteins C5b, C6, C7, C8, and C9n. We show that intact S-protein/vitronectin or its cyanogen bromide generated fragments also inhibit the hemolysis mediated by perforin from cytotoxic T-cells at 45 and 11 microM, respectively. The glycosaminoglycan binding site of S-protein/vitronectin is responsible for the inhibition, since a synthetic peptide corresponding to a part of this highly basic domain (amino acid residues 348-360) inhibits complement- as well as perforin-mediated cytolysis. In the case of C9, the synthetic peptide binds to the acidic residues occurring in its N-terminal cysteine-rich domain (residues 101-111). Antibodies raised against this particular segment react 25-fold better with the polymerized form of C9 as compared with its monomeric form, indicating that this site becomes exposed only upon the hydrophilic-amphiphilic transition of C9. Since the cysteine-rich domain of C9 has been shown to be highly conserved in C6, C7, and C8 as well as in perforin, the inhibition of the lytic activities of these molecules by S-protein/vitronectin or by peptides corresponding to its heparin binding site may be explained by a similar mechanism.  相似文献   
8.
9.
10.
Georg Söderbom 《Ethnos》2013,78(1-2):95-100
Current debates over the concept of culture are examined, especially with regard to the relationship of culture to bounded collectivities, human nature, and individuality; present‐day views are seen against the background of back‐and‐forth swings in the history of anthropological thought. Recent theorizing about cultural acquisition is also considered.  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