全文获取类型
收费全文 | 758254篇 |
免费 | 179571篇 |
国内免费 | 30524篇 |
出版年
2018年 | 8672篇 |
2017年 | 8138篇 |
2016年 | 10836篇 |
2015年 | 14643篇 |
2014年 | 16772篇 |
2013年 | 22295篇 |
2012年 | 25613篇 |
2011年 | 26558篇 |
2010年 | 19900篇 |
2009年 | 22637篇 |
2008年 | 24201篇 |
2007年 | 24935篇 |
2006年 | 22478篇 |
2005年 | 21706篇 |
2004年 | 21830篇 |
2003年 | 20467篇 |
2002年 | 20653篇 |
2001年 | 33177篇 |
2000年 | 31246篇 |
1999年 | 29054篇 |
1998年 | 15720篇 |
1997年 | 15210篇 |
1996年 | 14330篇 |
1995年 | 14281篇 |
1994年 | 13612篇 |
1993年 | 13183篇 |
1992年 | 25451篇 |
1991年 | 24952篇 |
1990年 | 25262篇 |
1989年 | 24222篇 |
1988年 | 22363篇 |
1987年 | 20889篇 |
1986年 | 19499篇 |
1985年 | 19071篇 |
1984年 | 15608篇 |
1983年 | 13455篇 |
1982年 | 11161篇 |
1981年 | 10073篇 |
1980年 | 9586篇 |
1979年 | 14788篇 |
1978年 | 11897篇 |
1977年 | 10996篇 |
1976年 | 10278篇 |
1975年 | 11029篇 |
1974年 | 12141篇 |
1973年 | 11958篇 |
1972年 | 11227篇 |
1971年 | 10437篇 |
1970年 | 9026篇 |
1969年 | 8879篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
V A Berezin E N Zhmarev I A Brodskaia G M Shevchenko L S Zashko 《Biulleten' eksperimental'no? biologii i meditsiny》1985,100(7):68-70
The content of neurospecific proteins S-100, GFA and D2 was measured in malignant cerebral tumors by electrophoresis with the use of monospecific antisera. Concomitant measurement of proteins S-100 and GFA is a more reliable diagnostic criterion as to the tumor histogenesis than study of each protein alone. D2 protein appeared to be the most stable specific marker. 相似文献
53.
All plant cells are provided with the necessary rigidity to withstand the turgor by an exterior cell wall. This wall is composed
of long crystalline cellulose microfibrils embedded in a matrix of other polysaccharides. The cellulose microfibrils are deposited
by mobile membrane bound protein complexes in remarkably ordered lamellar textures. The mechanism by which these ordered textures
arise, however, is still under debate. The geometrical model for cell wall deposition proposed by Emons and Mulder (Proc.
Natl. Acad. Sci. 95, 7215–7219, 1998) provides a detailed approach to the case of cell wall deposition in non-growing cells, where there is no evidence for the
direct influence of other cellular components such as microtubules. The model successfully reproduces even the so-called helicoidal
wall; the most intricate texture observed. However, a number of simplifying assumptions were made in the original calculations.
The present work addresses the issue of the robustness of the model to relaxation of these assumptions, by considering whether
the helicoidal solutions survive when three aspects of the model are varied. These are: (i) the shape of the insertion domain,
(ii) the distribution of lifetimes of individual CSCs, and (iii) fluctuations and overcrowding. Although details of the solutions
do change, we find that in all cases the overall character of the helicoidal solutions is preserved. 相似文献
54.
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
55.
56.
57.
58.
59.
60.