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   156421篇
  免费   5636篇
  国内免费   850篇
  2023年   329篇
  2022年   355篇
  2021年   1359篇
  2020年   974篇
  2019年   1075篇
  2018年   12939篇
  2017年   11578篇
  2016年   9264篇
  2015年   3551篇
  2014年   3289篇
  2013年   4069篇
  2012年   8524篇
  2011年   16601篇
  2010年   14203篇
  2009年   10359篇
  2008年   12514篇
  2007年   13967篇
  2006年   2946篇
  2005年   3375篇
  2004年   3748篇
  2003年   3387篇
  2002年   2767篇
  2001年   1874篇
  2000年   1690篇
  1999年   1386篇
  1998年   704篇
  1997年   646篇
  1996年   637篇
  1995年   503篇
  1994年   523篇
  1993年   506篇
  1992年   1006篇
  1991年   902篇
  1990年   805篇
  1989年   788篇
  1988年   802篇
  1987年   714篇
  1986年   658篇
  1985年   641篇
  1984年   601篇
  1983年   469篇
  1982年   353篇
  1981年   346篇
  1980年   326篇
  1979年   448篇
  1978年   366篇
  1975年   308篇
  1974年   308篇
  1972年   465篇
  1971年   468篇
排序方式: 共有10000条查询结果,搜索用时 421 毫秒
81.
82.

Background  

Radial chromosome positioning in interphase nuclei is nonrandom and can alter according to developmental, differentiation, proliferation, or disease status. However, it is not yet clear when and how chromosome repositioning is elicited.  相似文献   
83.

Background  

In heterogeneous environments, sex-biased dispersal could lead to environmental adaptive parental effects, with offspring selected to perform in the same way as the parent dispersing least, because this parent is more likely to be locally adapted. We investigate this hypothesis by simulating varying levels of sex-biased dispersal in a patchy environment. The relative advantage of a strategy involving pure maternal (or paternal) inheritance is then compared with a strategy involving classical biparental inheritance in plants and in animals.  相似文献   
84.
TNF inhibitors are currently considered both effective and cost-effective in patients with active rheumatoid arthritis (RA), particularly in patients who have not responded fully to methotrexate. There is substantial doubt about the cost-effectiveness of TNF inhibitors as initial treatment for active RA. New data from the National Data Bank for Rheumatic Diseases now question the current consensus in methotrexate failures. The data suggest that in routine clinical practice TNF inhibitors provide only modest incremental benefits over best conventional therapy. If confirmed, these observational studies suggest that the economic argument underpinning the widespread use of TNF inhibitors in established RA is unsustainable.  相似文献   
85.

Background  

DNA Microarrays have become the standard method for large scale analyses of gene expression and epigenomics. The increasing complexity and inherent noisiness of the generated data makes visual data exploration ever more important. Fast deployment of new methods as well as a combination of predefined, easy to apply methods with programmer's access to the data are important requirements for any analysis framework. Mayday is an open source platform with emphasis on visual data exploration and analysis. Many built-in methods for clustering, machine learning and classification are provided for dissecting complex datasets. Plugins can easily be written to extend Mayday's functionality in a large number of ways. As Java program, Mayday is platform-independent and can be used as Java WebStart application without any installation. Mayday can import data from several file formats, database connectivity is included for efficient data organization. Numerous interactive visualization tools, including box plots, profile plots, principal component plots and a heatmap are available, can be enhanced with metadata and exported as publication quality vector files.  相似文献   
86.
To obtain insight into the role of lipids in the translocation of extramitochondrially synthesized proteins, we studied the ability of apocytochrome c to pass lipid bilayers. With polyacrylamide gel electrophoresis, the digestion of externally added apocytochrome c by trypsin, enclosed in lipid vesicles, was followed. The experiments demonstrate that apocytochrome c is able to pass a lipid barrier and this process shows both a lipid- and protein specificity. The most probable molecular mechanisms involved in this phenomenon are discussed.  相似文献   
87.
88.
The anti-DNP response to DNP-BGG is substantially suppressed in guinea pigs sensitized to DNCB. The degree of antibody suppression varies with the mode of skin sensitization and with the degree of conjugation of the challenging immunogen. Suppression of the anti-HSA response was also induced by the prior injection of CFA.  相似文献   
89.
90.
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