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   4182篇
  免费   247篇
  2024年   5篇
  2023年   35篇
  2022年   57篇
  2021年   118篇
  2020年   82篇
  2019年   99篇
  2018年   140篇
  2017年   124篇
  2016年   198篇
  2015年   245篇
  2014年   287篇
  2013年   316篇
  2012年   335篇
  2011年   334篇
  2010年   207篇
  2009年   183篇
  2008年   221篇
  2007年   208篇
  2006年   215篇
  2005年   155篇
  2004年   158篇
  2003年   124篇
  2002年   107篇
  2001年   58篇
  2000年   74篇
  1999年   53篇
  1998年   22篇
  1997年   23篇
  1996年   13篇
  1995年   17篇
  1994年   13篇
  1993年   15篇
  1992年   14篇
  1991年   16篇
  1990年   18篇
  1989年   18篇
  1988年   11篇
  1987年   10篇
  1986年   6篇
  1985年   6篇
  1984年   7篇
  1983年   9篇
  1982年   5篇
  1981年   5篇
  1979年   9篇
  1978年   5篇
  1977年   5篇
  1974年   7篇
  1973年   12篇
  1970年   5篇
排序方式: 共有4429条查询结果,搜索用时 14 毫秒
1.
International Journal of Primatology - The selection of sleeping sites and sleeping trees in nonhuman primates is related to social and ecological factors. We investigate the role of body...  相似文献   
2.
3.
7-MethyljugIone, 8,8′-dihydroxy-4,4′-dimethoxy-6,6′-dimethyl-2,2′-binaphthyl-1,1′-quinone, 2-methylnaphthazarin, mamegakinone and euclein have been isolated from Euclea pseudebenus. Euclein is the 3,6′-dimer of 7-methyljuglone.  相似文献   
4.
5.
6.
Jorge Lobo’s disease (JLD) is a chronic infection that affects the skin and subcutaneous tissues. Its etiologic agent is the fungus Lacazia loboi. Lesions are classified as localized, multifocal, or disseminated, depending on their location. Early diagnosis and the surgical removal of lesions are the best therapeutic options currently available for JLD. The few studies that evaluate the immunological response of JLD patients show a predominance of Th2 response, as well as a high frequency of TGF-β and IL-10 positive cells in the lesions; however, the overall immunological status of the lesions in terms of their T cell phenotype has yet to be determined. Therefore, the objective of this study was to evaluate the pattern of Th1, Th2, Th17 and regulatory T cell (Treg) markers mRNA in JLD patients by means of real-time PCR. Biopsies of JLD lesions (N = 102) were classified according to their clinical and histopathological features and then analyzed using real-time PCR in order to determine the expression levels of TGF-β1, FoxP3, CTLA4, IKZF2, IL-10, T-bet, IFN-γ, GATA3, IL-4, IL-5, IL-13, IL-33, RORC, IL-17A, IL-17F, and IL-22 and to compare these levels to those of healthy control skin (N = 12). The results showed an increased expression of FoxP3, CTLA4, TGF-β1, IL-10, T-bet, IL-17F, and IL-17A in lesions, while GATA3 and IL-4 levels were found to be lower in diseased skin than in the control group. When the clinical forms were compared, TGF-β1 was found to be highly expressed in patients with a single localized lesion while IL-5 and IL-17A levels were higher in patients with multiple/disseminated lesions. These results demonstrate the occurrence of mixed T helper responses and suggest the dominance of regulatory T cell activity, which could inhibit Th-dependent protective responses to intracellular fungi such as L. loboi. Therefore, Tregs may play a key role in JLD pathogenesis.  相似文献   
7.
Levans produced by four Zymomonas mobilis strains showed antitumour activity against sarcoma 180 and Ehrlich carcinoma in Swiss albino mice. Levans from two strains (ZAP and CP4) had the highest effects. NMR analysis showed that the polymers were composed only of fructose units. The results suggested that the antineoplasic effect is associated to the polysaccharide molecular weight and that a particular molecular weight range may be responsible for this effect.  相似文献   
8.
Summary The ability of early proximal tubule cells of theNecturus kidney to regulate volume was evaluated using light microscopy, video analysis and conventional microelectrodes.Necturus proximal tubule cells regulate volume in both hyperand hyposmotic solutions. Volume regulation in hyperosmotic fluids is HCO 3 dependent and is associated with a decrease in the relative K+ conductance of the basolateral cell membrane and a decrease in the resistance ratio,R a /R bl . Volume regulation in hyposmotic solutions is also dependent upon the presence of HCO 3 but is also inhibited by 2mm Ba2+ in the basolateral solution. Hyposmotic regulation is accompanied by an increase in the relative K+ conductance of the basolateral cell membrane and an increase inR a /R bl . Neither hypo- nor hyposmotic regulation have any affect on the depolarization of the basolateral cell membrane potential induced by HCO 3 removal. We conclude that volume regulation in the early proximal tubule of the kidney involves both HCO 3 -dependent transport systems and the basolateral K+ conductance.  相似文献   
9.
A study of the morphology of the salivary glands of the colubrid snake Oxyrhopus trigeminus showed the following: The acini of supralabial, infralabial, and premaxillary glands are formed by mucous and mucoserous cells; the tubules of Duvernoy's gland are formed by seromucous cells; and mucous cells produce neutral and acid mucosubstances, mucoserous cells secrete neutral and acid mucosubstances and protein, and seromucous cells have neutral mucosubstance and protein secretions.  相似文献   
10.
The analysis of gut contents ofAmphichaeta leydigii, found for the first time in Italy in sandy shores of Lake Vico (Central Italy), proved grazing of the species on diatoms (Centrales and Pennales). Detritus and organic particles, abundant in the substratum, were observed only in small amounts.  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