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   247篇
  免费   23篇
  国内免费   2篇
  2022年   2篇
  2021年   3篇
  2020年   2篇
  2016年   2篇
  2015年   9篇
  2014年   9篇
  2013年   2篇
  2012年   12篇
  2011年   8篇
  2010年   10篇
  2009年   6篇
  2008年   7篇
  2007年   5篇
  2006年   4篇
  2005年   6篇
  2004年   8篇
  2003年   3篇
  2002年   4篇
  2001年   5篇
  2000年   6篇
  1999年   10篇
  1998年   4篇
  1997年   2篇
  1996年   4篇
  1995年   3篇
  1994年   3篇
  1992年   2篇
  1991年   3篇
  1990年   4篇
  1989年   4篇
  1988年   3篇
  1982年   1篇
  1977年   3篇
  1969年   1篇
  1888年   5篇
  1887年   12篇
  1886年   12篇
  1885年   13篇
  1884年   12篇
  1883年   12篇
  1882年   12篇
  1881年   12篇
  1880年   2篇
  1878年   1篇
  1877年   1篇
  1874年   3篇
  1873年   1篇
  1871年   4篇
  1870年   2篇
  1869年   2篇
排序方式: 共有272条查询结果,搜索用时 31 毫秒
201.
202.
In this study we identified two heterocyclic compounds (5 and 6) as potent and specific inhibitors of CK1δ (IC(50)?=?0.040 and 0.042?μM, respectively). Whereas compound 5 exhibited fivefold higher affinity towards CK1δ than to CK1ε (IC(50) CK1ε?=?0.199?μM), compound 6 also inhibited CK1ε (IC(50)?=?0.0326?μM) in the same range as CK1δ. Selected compound 5 was screened over 442 kinases identifying 5 as a highly potent and selective inhibitor of CK1δ. X-ray analysis of 5 bound to CK1δ demonstrated its binding mode. In addition, characterization of 5 and 6 in a cell biological approach revealed the ability of both compounds to inhibit proliferation of tumor cell lines in a dose and cell line specific manner. In summary, our optimizations lead to the development of new highly selective CK1δ and ε specific inhibitors with biological activity.  相似文献   
203.
204.

Background

As predicted by theory, traits associated with reproduction often evolve at a comparatively high speed. This is especially the case for courtship behaviour which plays a central role in reproductive isolation. On the other hand, courtship behavioural traits often involve morphological and behavioural adaptations in both sexes; this suggests that their evolution might be under severe constraints, for instance irreversibility of character loss. Here, we use a recently proposed method to retrieve data on a peculiar courtship behavioural trait, i.e. antennal coiling, for 56 species of diplazontine parasitoid wasps. On the basis of a well-resolved phylogeny, we reconstruct the evolutionary history of antennal coiling and associated morphological modifications to study the mode of evolution of this complex character system.

Results

Our study reveals a large variation in shape, location and ultra-structure of male-specific modifications on the antennae. As for antennal coiling, we find either single-coiling, double-coiling or the absence of coiling; each state is present in multiple genera. Using a model comparison approach, we show that the possession of antennal modifications is highly correlated with antennal coiling behaviour. Ancestral state reconstruction shows that both antennal modifications and antennal coiling are highly congruent with the molecular phylogeny, implying low levels of homoplasy and a comparatively low speed of evolution. Antennal coiling is lost on two independent occasions, and never reacquired. A zero rate of regaining antennal coiling is supported by maximum parsimony, maximum likelihood and Bayesian approaches.

Conclusions

Our study provides the first comparative evidence for a tight correlation between male-specific antennal modifications and the use of the antennae during courtship. Antennal coiling in Diplazontinae evolved at a comparatively low rate, and was never reacquired in any of the studied taxa. This suggests that the loss of antennal coiling is irreversible on the timescale examined here, and therefore that evolutionary constraints have greatly influenced the evolution of antennal courtship in this group of parasitoid wasps. Further studies are needed to ascertain whether the loss of antennal coiling is irreversible on larger timescales, and whether evolutionary constraints have influenced courtship behavioural traits in a similar way in other groups.
  相似文献   
205.
外加5 mmol/L Ca~(2 )可以使菠菜PSⅡ颗粒的放氧活性增高。PSⅡ颗粒经EGTA透析、低pH值、光照、2 mol/L NaCl等处理后,放氧活性下降,同时,这些颗粒的钙含量也相应降低。但当外加 5 mmol/L Ca~(2 )时,可使这些颗粒全部或部分地恢复放氧活性。PSⅡ颗粒中存在的钙对放氧起着重要作用;钙在PSⅡ颗粒中的结合位点不止一个,其结合状态有紧密和松散之别。  相似文献   
206.
Potassium Channels,Proliferation and G1 Progression   总被引:24,自引:0,他引:24  
  相似文献   
207.
Flora des Etna     
Ohne Zusammenfassung  相似文献   
208.
Flora des Etna     
Ohne Zusammenfassung  相似文献   
209.
Flora des Etna     
Ohne Zusammenfassung  相似文献   
210.
Flora des Etna     
Ohne Zusammenfassung  相似文献   
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