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   18479篇
  免费   920篇
  国内免费   27篇
  19426篇
  2024年   31篇
  2023年   164篇
  2022年   376篇
  2021年   704篇
  2020年   414篇
  2019年   442篇
  2018年   644篇
  2017年   603篇
  2016年   784篇
  2015年   886篇
  2014年   1128篇
  2013年   1548篇
  2012年   1630篇
  2011年   1434篇
  2010年   831篇
  2009年   729篇
  2008年   840篇
  2007年   813篇
  2006年   682篇
  2005年   617篇
  2004年   500篇
  2003年   414篇
  2002年   372篇
  2001年   309篇
  2000年   279篇
  1999年   254篇
  1998年   100篇
  1997年   76篇
  1996年   82篇
  1995年   77篇
  1994年   57篇
  1993年   56篇
  1992年   152篇
  1991年   143篇
  1990年   113篇
  1989年   85篇
  1988年   126篇
  1987年   97篇
  1986年   80篇
  1985年   81篇
  1984年   81篇
  1983年   46篇
  1982年   40篇
  1981年   47篇
  1980年   43篇
  1979年   56篇
  1978年   35篇
  1977年   43篇
  1976年   31篇
  1974年   29篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Proleptonchoides southindiae n. gen., n. sp. (Dorylaimida: Leptonchidae), is described from soil around false tobacco (Lobelia excelsa) and cardamom (Elettaria cardamomurn) in South India. P. southindiae is prodelphic, has a short constricted esophageal bulb and flanged odontophore, and is phylogenetically close to Proleptonchus.  相似文献   
52.
The synergistic effect of UV irradiation and heat-shock during the last 3 hr of G2 phase of the cell cycle in the plasmodia of P. polycephalum, in terms of mitotic delay and inhibition of protein synthesis, has been evaluated. The mitotic delay due to both perturbers coordinately increased closer to mitosis. Maximum mitotic delay was obtained in plasmodia heat-shocked after UV irradiation, indicating the presence in this system of either a heat-labile mitogenic substance which is comparatively less susceptible to UV or a substance which is made more susceptible to hyperthermia by UV. A protective role for heat-shock applied before irradiation has been observed in that, radiation-induced mitotic delay is significantly reduced in this combination. There was severe inhibition of translation in all the perturbed classes. Organelle level effects which are independent of major protein synthetic activities or different levels of heat-shock protein production could be the reason for the lack of correlation between percentage inhibition of general protein synthesis and the extent of mitotic delay with respect to the two double-perturbed systems.  相似文献   
53.
M A Kumar  V L Davidson 《Biochemistry》1990,29(22):5299-5304
Two soluble periplasmic redox proteins from Paracoccus denitrificans, the quinoprotein methylamine dehydrogenase and the copper protein amicyanin, form a weakly associated complex that is critical to their physiological function in electron transport [Gray, K. A., Davidson, V. L., & Knaff, D. B. (1988) J. Biol. Chem. 263, 13987-13990]. The specific interactions between methylamine dehydrogenase and amicyanin have been studied by using the water-soluble cross-linking agent 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC). Treatment of methylamine dehydrogenase alone with EDC caused no intermolecular cross-linking but did cause intramolecular cross-linking of this alpha 2 beta 2 oligomeric enzyme. The primary product that was formed contained one large and one small subunit. Methylamine dehydrogenase and amicyanin were covalently cross-linked in the presence of EDC to form at least two distinct species, which were identified by nondenaturing polyacrylamide gel electrophoresis (PAGE). The formation of these cross-linked species was dependent on ionic strength, and the ionic strength dependence was much greater at pH 6.5 than at pH 7.5. The effects of pH and ionic strength were different for the different cross-linked products. SDS-PAGE and Western blot analysis of these cross-linked species indicated that the primary site of interaction for amicyanin was the large subunit of methylamine dehydrogenase and that this association could be stabilized by hydrophobic interactions. In light of these results a scheme is proposed for the interaction of amicyanin with methylamine dehydrogenase that is consistent with previous data on the physical, kinetic, and redox properties of this complex.  相似文献   
54.
55.
56.
The present study was carried out to determine the detailed histological and cytological features of the excurrent ducts of the male reproductive system in the rhesus monkey. The excurrent ducts show a regional difference in their histological features. The use of some of these features as histological markers and their possible functional significance are discussed. The epithelial cells in the different components of the excurrent duct system possess cytological features which suggest their involvement in absorption and the secretion of different products into the lumen.  相似文献   
57.
58.
59.
60.
The molecular mechanisms of toxicity associated with cytoplasmic accumulation of TAR DNA binding protein-43(TDP-43),a pathological feature of many neurodegenera...  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