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   6424篇
  免费   632篇
  国内免费   4篇
  2021年   69篇
  2020年   42篇
  2019年   68篇
  2018年   68篇
  2017年   79篇
  2016年   112篇
  2015年   179篇
  2014年   219篇
  2013年   267篇
  2012年   347篇
  2011年   323篇
  2010年   212篇
  2009年   161篇
  2008年   263篇
  2007年   309篇
  2006年   297篇
  2005年   255篇
  2004年   256篇
  2003年   220篇
  2002年   234篇
  2001年   156篇
  2000年   149篇
  1999年   133篇
  1998年   98篇
  1997年   76篇
  1996年   81篇
  1995年   55篇
  1994年   65篇
  1993年   61篇
  1992年   97篇
  1991年   100篇
  1990年   76篇
  1989年   87篇
  1988年   88篇
  1987年   83篇
  1986年   75篇
  1985年   79篇
  1984年   62篇
  1983年   49篇
  1982年   50篇
  1981年   45篇
  1979年   66篇
  1978年   46篇
  1977年   67篇
  1976年   59篇
  1975年   49篇
  1974年   55篇
  1973年   59篇
  1972年   55篇
  1970年   47篇
排序方式: 共有7060条查询结果,搜索用时 15 毫秒
1.
The review focuses on the multiple separating regimes that offers the free flow electrophoresis technique: free flow zone electrophoresis, isoelectric focusing, isotachophoresis, free flow step electrophoresis. Also, the feasibility to apply either interval or continuous flow electrophoresis is evaluated. The free flow zone electrophoresis regime is generally selected for the separation of cells, organelles and membranes while the other regimes find their largest fields of applications in the purification of proteins and peptides. The latter regimes present the highest resolution efficiency. Therefore, a large part of this review is devoted to the applicabilities of these different regimes to the purification of organelles and membrane vesicles at the preparative scale. Recent developments, both in instrumentation and procedures, are described. The major achievements in plant membrane fractionation obtained with free flow electrophoresis are outlined. The related procedures are both analytical and preparative: they separate tonoplast and plasma membrane simultaneously from the same homogenate, they discriminate for one type of membrane vesicles of opposite orientation, and process large quantities of membrane material by reason of the continuous flow mode. Recent advances using electromigration techniques that permit confirmation of the dynamic state of membranes, characterisation of complex membrane-dependent functions and discovery of new membrane-localised activities are presented.  相似文献   
2.
3.
Summary The rôle of several structural and functional factors and of concentration on the cross-reactions of 28 human plasma proteins with their homologues in animal blood was investigated. The Immunological Evolution Group (IEG) system was employed for this purpose as described earlier (Bauer, 1970 a). No interaction of structural factors was detected, while an influence of serum level of the different proteins could not be ruled out with certainty.At least in the case of the 4 immunoglobulins and the 3 complement factors, included in the IEG-system, protein function and evolution show some degree of correlation, indicating the influence of function on molecular evolution in the case of these plasma proteins.  相似文献   
4.
5.
Behaviour traits of cattle have been reported to affect important production traits, such as meat quality and milk performance as well as reproduction and health. Genetic predisposition is, together with environmental stimuli, undoubtedly involved in the development of behaviour phenotypes. Underlying molecular mechanisms affecting behaviour in general and behaviour and productions traits in particular still have to be studied in detail. Therefore, we performed a genome‐wide association study in an F2 Charolais × German Holstein cross‐breed population to identify genetic variants that affect behaviour‐related traits assessed in an open‐field and novel‐object test and analysed their putative impact on milk performance. Of 37 201 tested single nucleotide polymorphism (SNPs), four showed a genome‐wide and 37 a chromosome‐wide significant association with behaviour traits assessed in both tests. Nine of the SNPs that were associated with behaviour traits likewise showed a nominal significant association with milk performance traits. On chromosomes 14 and 29, six SNPs were identified to be associated with exploratory behaviour and inactivity during the novel‐object test as well as with milk yield traits. Least squares means for behaviour and milk performance traits for these SNPs revealed that genotypes associated with higher inactivity and less exploratory behaviour promote higher milk yields. Whether these results are due to molecular mechanisms simultaneously affecting behaviour and milk performance or due to a behaviour predisposition, which causes indirect effects on milk performance by influencing individual reactivity, needs further investigation.  相似文献   
6.
Media, and particularly TV media, have a great impact on the general public. In recent years, spatial patterns of information and the relevance of intangible geographies have become increasingly important. Gatekeeping plays a critical role in the selection of information that is transformed into media. Therefore, gatekeeping, through national media, also co-forms the generation of mental maps. In this paper, correspondence analysis (a statistical method) combined with cloud lines (a new visual analytics technique) is used to analyze how individual major regional events in one of the post-communist countries, the Czech Republic, penetrate into the media on a national scale. Although national news should minimize distortions about regions, this assumption has not been verified by our research. Impressions presented by the media of selected regions that were markedly influenced by one or several events in those regions demonstrate that gatekeepers, especially news reporters, functioned as a filter by selecting only a few specific, and in many cases, unusual events for dissemination.  相似文献   
7.
8.
9.
10.
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