全文获取类型
收费全文 | 21495篇 |
免费 | 2067篇 |
国内免费 | 20篇 |
出版年
2021年 | 278篇 |
2020年 | 144篇 |
2019年 | 217篇 |
2018年 | 266篇 |
2017年 | 215篇 |
2016年 | 398篇 |
2015年 | 710篇 |
2014年 | 795篇 |
2013年 | 979篇 |
2012年 | 1281篇 |
2011年 | 1344篇 |
2010年 | 801篇 |
2009年 | 693篇 |
2008年 | 1028篇 |
2007年 | 1155篇 |
2006年 | 1061篇 |
2005年 | 1040篇 |
2004年 | 1028篇 |
2003年 | 1006篇 |
2002年 | 966篇 |
2001年 | 275篇 |
2000年 | 208篇 |
1999年 | 264篇 |
1998年 | 288篇 |
1997年 | 213篇 |
1996年 | 191篇 |
1995年 | 215篇 |
1994年 | 199篇 |
1993年 | 189篇 |
1992年 | 219篇 |
1991年 | 179篇 |
1990年 | 181篇 |
1989年 | 189篇 |
1988年 | 175篇 |
1987年 | 176篇 |
1986年 | 173篇 |
1985年 | 197篇 |
1984年 | 200篇 |
1983年 | 170篇 |
1982年 | 237篇 |
1981年 | 246篇 |
1980年 | 235篇 |
1979年 | 161篇 |
1978年 | 184篇 |
1977年 | 154篇 |
1976年 | 181篇 |
1975年 | 141篇 |
1974年 | 150篇 |
1973年 | 171篇 |
1970年 | 105篇 |
排序方式: 共有10000条查询结果,搜索用时 429 毫秒
1.
2.
Protein Kinase PKR Mediates the Apoptosis Induction and Growth Restriction Phenotypes of C Protein-Deficient Measles Virus 总被引:1,自引:0,他引:1 下载免费PDF全文
Ann M. Toth Patricia Devaux Roberto Cattaneo Charles E. Samuel 《Journal of virology》2009,83(2):961-968
The measles virus (MV) accessory proteins V and C play important roles in MV replication and pathogenesis. Infection with recombinant MV lacking either V or C causes more cell death than infection with the parental vaccine-equivalent virus (MVvac), and C-deficient virus grows poorly relative to the parental virus. Here, we show that a major effector of the C phenotype is the RNA-dependent protein kinase PKR. Using human HeLa cells stably deficient in PKR as a result of RNA interference-mediated knockdown (PKRkd cells), we demonstrated that a reduction in PKR partially rescued the growth defect of C knockout (Cko) virus but had no effect on the growth of either wild-type (WT) or V knockout (Vko) virus. Increased growth of the Cko virus in PKRkd cells correlated with increased viral protein expression, while defective growth and decreased protein expression in PKR-sufficient cells correlated with increased phosphorylation of PKR and the α subunit of eukaryotic initiation factor 2. Furthermore, infection with WT, Vko, or especially Cko virus caused significantly less apoptosis in PKRkd cells than in PKR-sufficient cells. Although apoptosis induced by Cko virus infection in PKR-sufficient cells was blocked by a caspase antagonist, the growth of Cko virus was not restored to the WT level by treatment with this pharmacologic inhibitor. Taken together, these results indicate that PKR plays an important antiviral role during MV infection but that the virus growth restriction by PKR is not dependent upon the induction of apoptosis. Furthermore, the results establish that a principal function of the MV C protein is to antagonize the proapoptotic and antiviral activities of PKR. 相似文献
3.
4.
5.
Howard Marsh 《BMJ (Clinical research ed.)》1888,2(1450):805-807
6.
7.
8.
9.
Myelography using pantopaque in greater than usual amount with a variation in technique, which is described, is believed to provide increased accuracy in differential diagnosis and precise localization of lesions in the lumbar spine. The need for multiple space exploration is eliminated and more detailed information concerning the size and shape of lesions is provided as compared to that secured by the use of 3 or 6 cc. of opaque medium and fluoroscopic examination alone. In 53 cases in which lumbar myelography was performed and the diagnosis verified or disproved at operation, there was a 5 per cent diagnostic error in 41 instances in which the method outlined was used, as compared with 17 per cent error in 12 cases in which only 3 or 6 cc. of radiopaque material and fluoroscopy alone were used. The accuracy of the procedure would appear to warrant its use in the evaluation of patients suspected of having abnormalities of the lumbar discs associated with nerve root compression. 相似文献
10.