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   55433篇
  免费   4418篇
  国内免费   9篇
  2023年   262篇
  2021年   512篇
  2020年   425篇
  2019年   404篇
  2018年   1091篇
  2017年   1083篇
  2016年   1287篇
  2015年   1325篇
  2014年   1569篇
  2013年   2475篇
  2012年   3841篇
  2011年   4257篇
  2010年   2264篇
  2009年   1544篇
  2008年   3382篇
  2007年   3451篇
  2006年   3254篇
  2005年   2886篇
  2004年   2746篇
  2003年   2506篇
  2002年   2540篇
  2001年   1693篇
  2000年   1941篇
  1999年   1066篇
  1998年   547篇
  1997年   389篇
  1996年   483篇
  1995年   417篇
  1994年   449篇
  1993年   401篇
  1992年   478篇
  1991年   433篇
  1990年   390篇
  1989年   343篇
  1988年   354篇
  1987年   343篇
  1986年   296篇
  1985年   402篇
  1984年   454篇
  1983年   410篇
  1982年   376篇
  1981年   362篇
  1980年   297篇
  1979年   326篇
  1978年   306篇
  1977年   312篇
  1976年   278篇
  1975年   328篇
  1974年   254篇
  1973年   247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