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   204篇
  免费   21篇
  2023年   1篇
  2022年   3篇
  2021年   8篇
  2020年   4篇
  2019年   6篇
  2018年   4篇
  2017年   8篇
  2016年   11篇
  2015年   19篇
  2014年   15篇
  2013年   16篇
  2012年   22篇
  2011年   18篇
  2010年   10篇
  2009年   13篇
  2008年   16篇
  2007年   4篇
  2006年   15篇
  2005年   14篇
  2004年   5篇
  2003年   2篇
  2002年   4篇
  2001年   1篇
  2000年   2篇
  1999年   1篇
  1997年   1篇
  1996年   1篇
  1989年   1篇
排序方式: 共有225条查询结果,搜索用时 15 毫秒
221.
In the early 1990s, it has been described that LTα and LTβ form LTα2β and LTαβ2 heterotrimers, which bind to TNFR1 and LTβR, respectively. Afterwards, the LTαβ2–LTβR system has been intensively studied while the LTα2β–TNFR1 interaction has been ignored to date, presumably due to the fact that at the time of identification of the LTα2β–TNFR1 interaction one knew already two ligands for TNFR1, namely TNF and LTα. Here, we show that LTα2β interacts not only with TNFR1 but also with TNFR2. We furthermore demonstrate that membrane-bound LTα2β (memLTα2β), despite its asymmetric structure, stimulates TNFR1 and TNFR2 signaling. Not surprising in view of its ability to interact with TNFR2, LTα2β is inhibited by Etanercept, which is approved for the treatment of rheumatoid arthritis and also inhibits TNF and LTα.Subject terms: Cytokines, Signal transduction  相似文献   
222.
223.
224.
1.  Variation in longevity within and between natural populations is widespread, and understanding the relative importance of environmental and genetic factors as well as their interactions in mediating such variation is crucial in longevity research.
2.  In this study lifespan of adult copper butterflies was examined in relation to altitude, temperature (20 and 27 °C), sex and adult feeding.
3.  As expected, longevity increased with decreasing temperature, and sucrose-fed butterflies had longer lifespans compared to water-fed and finally non-fed individuals. The impact of feeding, especially of having access to water or not, was larger at the higher compared to the lower temperature.
4.  Regarding altitudinal patterns, increased lifespan in high-altitude populations was largely restricted to beneficial feeding conditions, while under carbohydrate deprivation low-altitude animals lived longer, suggesting that low-altitude butterflies do better under food stress.
5.  Differences in longevity between sexes were small at 20 °C, while females lived substantially longer than males at the higher temperature. Consequently, females may be less susceptible to high temperature stress than males. Further, males suffered more from food stress than females, suggesting that females are generally more stress resistant than males.
6.  Using a full factorial design, this study demonstrates that variation in longevity is caused by several factors, and additionally by substantial interactive effects. Consequently, patterns of variation in longevity are complex, and one needs to be cautious when neglecting this source of variation, by focussing on individual factors only.  相似文献   
225.
The following study presents a statistical analysis of 595 relevés gathered during a survey of isolated grasslands and dwarf shrub heaths in the region of Halle, eastern Germany. Relevés were classified with UPGMA clustering based on a Bray-Curtis distance matrix; the resulting classification was compared with a previously published phytosociological classification. Most of the 14 target communities were supported by both approaches, but in the case of communities on heavily disturbed sites cluster analysis corresponded to units on higher phytosociological levels (alliances). DCA ordinations clearly revealed that nutrient and moisture availability controlled the community differentiation. Both factors were, however, highly correlated with the distance to the outcrop edge. Thus the outcrop size also influenced differentiation of communities, making larger outcrops richer in xerophytic and endangered species. This appears to be largely due to edge effects since the relationships diminished sharply when we controlled for progressively increasing distances from the edge in partial ordinations. Thus, microtopography of outcrops was the most important factor for community differentiation. It is therefore suggested that future research and conservation management should concentrate on the consequences of nutrient influx and changing land use on larger outcrops.  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