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   712篇
  免费   87篇
  国内免费   1篇
  2022年   9篇
  2021年   13篇
  2020年   7篇
  2019年   11篇
  2018年   17篇
  2017年   16篇
  2016年   18篇
  2015年   23篇
  2014年   29篇
  2013年   20篇
  2012年   37篇
  2011年   46篇
  2010年   25篇
  2009年   11篇
  2008年   35篇
  2007年   33篇
  2006年   28篇
  2005年   24篇
  2004年   32篇
  2003年   20篇
  2002年   13篇
  2001年   13篇
  2000年   27篇
  1999年   18篇
  1998年   8篇
  1997年   9篇
  1996年   12篇
  1994年   7篇
  1992年   21篇
  1991年   10篇
  1990年   13篇
  1989年   8篇
  1988年   11篇
  1986年   6篇
  1985年   12篇
  1984年   14篇
  1983年   7篇
  1982年   7篇
  1981年   8篇
  1980年   10篇
  1979年   10篇
  1978年   10篇
  1977年   5篇
  1976年   13篇
  1975年   6篇
  1974年   6篇
  1973年   16篇
  1972年   11篇
  1971年   7篇
  1970年   6篇
排序方式: 共有800条查询结果,搜索用时 31 毫秒
61.
62.
Saturnius papernai Overstreet, 1977 is recorded from the stomach of Mugil cephalus L. (Osteichthyes, Mugilidae) in the Black Sea (a new geographical record) off the southern part of the Bulgarian coast. The species is redescribed and figured on the basis of the Black Sea specimens. Some amendments to the generic diagnosis are proposed concerning the presence of a uterine seminal receptacle and a posterior (third) circular flange. It is proposed that the occurrence of S. papernai is a feature of one of the three shoals of M. cephalus in the Black Sea, i.e. the Balkan shoal. In a zoogeographical analysis, S. papernai is regarded as a Mediterranean immigrant, probably a characteristic element of only the South-Western Faunistic Region of the Black Sea. A review of the genus Saturnius Manter, 1969 is presented.  相似文献   
63.
64.
65.
66.
Recent data suggest that insulators organize chromatin architecture in the nucleus. The best studied Drosophila insulator proteins, dCTCF (a homolog of the vertebrate insulator protein CTCF) and Su(Hw), are DNA-binding zinc finger proteins. Different isoforms of the BTB-containing protein Mod(mdg4) interact with Su(Hw) and dCTCF. The CP190 protein is a cofactor for the dCTCF and Su(Hw) insulators. CP190 is required for the functional activity of insulator proteins and is involved in the aggregation of the insulator proteins into specific structures named nuclear speckles. Here, we have shown that the nuclear distribution of CP190 is dependent on the level of EAST protein, an essential component of the interchromatin compartment. EAST interacts with CP190 and Mod(mdg4)-67.2 proteins in vitro and in vivo. Over-expression of EAST in S2 cells leads to an extrusion of the CP190 from the insulator bodies containing Su(Hw), Mod(mdg4)-67.2, and dCTCF. In consistent with the role of the insulator bodies in assembly of protein complexes, EAST over-expression led to a striking decrease of the CP190 binding with the dCTCF and Su(Hw) dependent insulators and promoters. These results suggest that EAST is involved in the regulation of CP190 nuclear localization.  相似文献   
67.
68.
Catalytic cycle intermediates of a representative extradiol dioxygenase, homoprotocatechuate 2,3-dioxygenase (HPCD), have recently been characterized in crystallo by Kovaleva and Lipscomb. The structures of the identified species indicate that the process of inserting oxygen into the catechol ring occurs stepwise, and involves an Fe(II)-alkylperoxo intermediate and its O–O cleavage product: a gem diol species. In general, these findings corroborate the results of our previous computational studies; however, the fact that the gem diol species is stable enough to be observed in the crystal form seems to be at odds with the computational mechanistic data, which suggest that this intermediate should very readily and spontaneously convert to the epoxide species. The key question then becomes what is actually observed in the X-ray experiments. Here we report additional computational studies undertaken with the hope of clarifying this issue. The results obtained for active site models hosting both the native and the alternative (4-sulfonylcatechol) substrate indicate that the stability of the gem diol species is substantially increased if an electron and a proton are added. If this occurs somehow, the lifetime of the intermediate should be sufficient to observe it.  相似文献   
69.
Cell suspension cultures of Lavandula vera (Lamiaceae), Nicotiana tabacum (Solanaceae), and Helianthus annuus (Asteraceae) were cultivated in three different ways: in shake flasks both as free suspensions and in two‐phase systems (in the presence of Amberlite XAD‐4 resin as a second phase), as well as in 3‐L stirred tank reactor, and their volatile metabolic profiles were studied using GC‐MS. A number of compounds, some of them having allelochemical and biological activities, were identified in all the three cell suspension cultures under study. Also the presence of some compounds, unusual for the intact plants, was observed. It was found that the cultivation mode strongly influences the production and the transport (secretion into the culture medium) of the low‐molecular‐mass volatile metabolites. Principal component analyses of 12 common hydrocarbons showed discrimination between the different cultivation modes (shake flasks and two‐phase systems cultivation) by first principal component (PC1) and second principal component (PC2).  相似文献   
70.
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