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   658576篇
  免费   79877篇
  国内免费   340篇
  738793篇
  2018年   5482篇
  2016年   7159篇
  2015年   9870篇
  2014年   11633篇
  2013年   16565篇
  2012年   18562篇
  2011年   19023篇
  2010年   12761篇
  2009年   12075篇
  2008年   16950篇
  2007年   17504篇
  2006年   16603篇
  2005年   16008篇
  2004年   15593篇
  2003年   15373篇
  2002年   14935篇
  2001年   33215篇
  2000年   33610篇
  1999年   26216篇
  1998年   8563篇
  1997年   9301篇
  1996年   8737篇
  1995年   8138篇
  1994年   7977篇
  1993年   8148篇
  1992年   21621篇
  1991年   21406篇
  1990年   20457篇
  1989年   20175篇
  1988年   18615篇
  1987年   17665篇
  1986年   16406篇
  1985年   16305篇
  1984年   13260篇
  1983年   11540篇
  1982年   8629篇
  1981年   7663篇
  1980年   7376篇
  1979年   12510篇
  1978年   9893篇
  1977年   8962篇
  1976年   8224篇
  1975年   9248篇
  1974年   9593篇
  1973年   9492篇
  1972年   8528篇
  1971年   7870篇
  1970年   6726篇
  1969年   6552篇
  1968年   5819篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
151.
152.
153.
Histone deacetylase from calf thymus   总被引:4,自引:0,他引:4  
  相似文献   
154.
A new gas-liquid chromatographic method was developed for the determination of diethylether in whole blood. Ether was quantitated by peak area ratio analysis with n-propanol as the internal standard using a flame ionization detector. Blood ether concentrations were determined in cats undergoing inhalational anesthesia by ether in oxygen. In normal spontaneously breathing cats, anesthesia began at ether concentrations of about 0.6 g/l, and respiratory arrest occurred at 2.4 g/l and above. Mean arterial blood pressure was well maintained throughout the entire anesthetic range. In spinal artificially respired animals, mean arterial blood pressure correlated inversely with blood ether concentration. The data suggest that decline in blood pressure may be a useful sign of ether toxicity in spinal cats.  相似文献   
155.
Intraperitoneal stimulation of adoptively sensitized rats with bacterial antigen promotes the localization of lymphoblasts at the site of antigen deposition. Lymphoblast extravasation activity (LEA) is generated only when specifically immune donor lymphocytes and the recipients of these cells share at least on Ag-B haplotype. However, if the specificity criteria for its formation are satisfied, LEA promotes the local development of lymphoblasts of all available specificities and irrespective of their Ag-B genotype. Allogeneic lymphoblasts do not participate actively in the delayed inflammatory reaction even when they are passively recruited into exudates. The results suggest that LEA is a T cell-derived mediator that amplifies the delayed type hypersensitivity reaction by directing recently activated lymphocytes into lesions.  相似文献   
156.
157.
158.
159.
Ffh is a component of a bacterial ribonucleoprotein complex homologous to the signal recognition particle (SRP) of eukaryotes. It comprises three domains that mediate both binding to the hydrophobic signal sequence of the nascent polypeptide and the GTP-dependent interaction of Ffh with a structurally homologous GTPase of the SRP receptor. The X-ray structures of the two-domain 'NG' GTPase of Ffh in complex with Mg2+GDP and GDP have been determined at 2.0 A resolution. The structures explain the low nucleotide affinity of Ffh and locate two regions of structural mobility at opposite sides of the nucleotide-binding site. One of these regions includes highly conserved sequence motifs that presumably contribute to the structural trigger signaling the GTP-bound state. The other includes the highly conserved interface between the N and G domains, and supports the hypothesis that the N domain regulates or signals the nucleotide occupancy of the G domain.  相似文献   
160.
An indwelling nasal suction tampon is described that effectively controls both intraoperative and postoperative nasal hemorrhage. The significant benefits of this device are better intraoperative control for the surgeon and less complicated postoperative recovery. I do not have any financial involvement in this device, but I would like other nasal surgeons to benefit from its particular advantages. The device is available under the trade name Instant and may be obtained from Innovations by Westmed, 3351 E. Hemisphere Loop, Tucson, Ariz. 85706; (602) 294-7987.  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