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   3937篇
  免费   22篇
  国内免费   50篇
系统科学   63篇
丛书文集   30篇
教育与普及   4篇
理论与方法论   54篇
现状及发展   1732篇
研究方法   243篇
综合类   1828篇
自然研究   55篇
  2018年   30篇
  2017年   35篇
  2016年   24篇
  2015年   25篇
  2014年   24篇
  2013年   46篇
  2012年   103篇
  2011年   130篇
  2010年   36篇
  2008年   86篇
  2007年   89篇
  2006年   114篇
  2005年   122篇
  2004年   127篇
  2003年   127篇
  2002年   156篇
  2001年   203篇
  2000年   155篇
  1999年   121篇
  1994年   263篇
  1992年   61篇
  1991年   28篇
  1990年   52篇
  1989年   47篇
  1988年   55篇
  1987年   55篇
  1986年   52篇
  1985年   65篇
  1984年   51篇
  1983年   35篇
  1982年   33篇
  1981年   34篇
  1980年   51篇
  1979年   95篇
  1978年   57篇
  1977年   71篇
  1976年   57篇
  1975年   65篇
  1974年   70篇
  1973年   73篇
  1972年   84篇
  1971年   86篇
  1970年   71篇
  1969年   67篇
  1968年   68篇
  1967年   75篇
  1966年   61篇
  1965年   47篇
  1958年   25篇
  1957年   24篇
排序方式: 共有4009条查询结果,搜索用时 0 毫秒
101.
Inflammation influences iron balance in the whole organism. A common clinical manifestation of these changes is anemia of chronic disease (ACD; also called anemia of inflammation). Inflammation reduces duodenal iron absorption and increases macrophage iron retention, resulting in low serum iron concentrations (hyposideremia). Despite the protection hyposideremia provides against proliferating microorganisms, this 'iron withholding' reduces the iron available to maturing red blood cells and eventually contributes to the development of anemia. Hepcidin antimicrobial peptide (Hamp) is a hepatic defensin-like peptide hormone that inhibits duodenal iron absorption and macrophage iron release. Hamp is part of the type II acute phase response and is thought to have a crucial regulatory role in sequestering iron in the context of ACD. Mice with deficiencies in the hemochromatosis gene product, Hfe, mounted a general inflammatory response after injection of lipopolysaccharide but lacked appropriate Hamp expression and did not develop hyposideremia. These data suggest a previously unidentified role for Hfe in innate immunity and ACD.  相似文献   
102.
CHARGE syndrome is a common cause of congenital anomalies affecting several tissues in a nonrandom fashion. We report a 2.3-Mb de novo overlapping microdeletion on chromosome 8q12 identified by array comparative genomic hybridization in two individuals with CHARGE syndrome. Sequence analysis of genes located in this region detected mutations in the gene CHD7 in 10 of 17 individuals with CHARGE syndrome without microdeletions, accounting for the disease in most affected individuals.  相似文献   
103.
104.
Riassunto È stato dimostrato che la transulfurazione che consegue alla incubazione dei solfinati con zolfo ed un composto tiolico è dovuta in parte alla produzione di un polisolfuro organico, formato dal tiolo e zolfo, ed in parte al polisolfuro inorganico, formato dalla decomposizione di quello organico. L'entità della transulfurazione prodotta direttamente dal polisolfuro organico varia con il tipo di polisolfuro e dipende dalla sua stabilità nelle condizioni usate.  相似文献   
105.
Riassunto Si descrivono gli effetti teratogeni indotti nella coda del girino delBufo arenarum in uno stadio premetamorfosico, come conseguenza dell'impianto di cristalli di idrocarburi cancerigeni. Tanto il MC come il BP o il DMBA producono alette sopranumerarie che ripetono le strutture istologiche delle alette normali; ed inoltre il DMBA induce la formazione di una seconda notocorda parallela alla normale.

Career investigator of Argentine CNICT.

Fellow of Argentine CNICT.  相似文献   
106.
Summary Pyruvate carboxylation was stimulated by 2 gastric secretagogues, histamine and dibutyryl cyclic AMP, and by butyrate. Thiocyanate, an inhibitor of acid secretion, produced a slight decrease. Avidin significantly reduced acid secretion and this effect was overcome by biotin and oxalacetate. The results suggest that carboxylation of pyruvate is one of the reactions controlling oxidative metabolism and acid secretion in toad gastric mucosa.This investigation was supported by Consejo de Desarrollo Científico y Humanístico de la Universidad del Zulia, and by CONICIT Grant S1-0455.  相似文献   
107.
Levamisole added to cultured calvarial bones inhibited spontaneous bone resorption, as indicated by reduced release of calcium and inorganic phosphate to the medium. In addition, levamisole reduced lactate production and release of lysosomal enzymes.  相似文献   
108.
109.
110.
Zusammenfassung In den einzelnen Abschnitten des menschlichen Nephrons und in Nierenhomogenaten wurden quantitativ die Glucose-6-phosphat-dehydrogenase-und die Isozitronens?uredehydrogenase-Aktivit?t gemessen.

This investigation was made possible by a grant from the Swiss National Foundation for the Development of Scientific Research. The technical assistance of MissD. Keller is gratefully acknowledged.  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