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   304篇
  免费   50篇
  国内免费   10篇
  364篇
  2021年   5篇
  2020年   3篇
  2018年   3篇
  2017年   3篇
  2016年   5篇
  2015年   8篇
  2014年   13篇
  2013年   13篇
  2012年   19篇
  2011年   13篇
  2010年   10篇
  2009年   8篇
  2008年   13篇
  2007年   8篇
  2006年   14篇
  2005年   10篇
  2004年   18篇
  2003年   22篇
  2002年   9篇
  2000年   4篇
  1999年   8篇
  1998年   4篇
  1997年   3篇
  1996年   4篇
  1994年   4篇
  1991年   6篇
  1990年   4篇
  1989年   9篇
  1988年   4篇
  1986年   7篇
  1985年   7篇
  1984年   11篇
  1983年   5篇
  1982年   4篇
  1981年   3篇
  1980年   8篇
  1977年   6篇
  1976年   4篇
  1975年   2篇
  1974年   4篇
  1973年   6篇
  1972年   3篇
  1971年   4篇
  1970年   4篇
  1969年   4篇
  1968年   3篇
  1967年   8篇
  1966年   3篇
  1965年   2篇
  1961年   2篇
排序方式: 共有364条查询结果,搜索用时 0 毫秒
361.
362.
363.
We used a simple life table approach to examine the age-specific patterns of harvest mortality in eight Norwegian moose populations during the last 15 years and tried to determine if the observed patterns were caused by hunter selectivity. The general opinion among local managers is that hunters prefer to shoot female moose not in company with calves to keep a high number of reproductive females in the population (and because of the emotional stress involved in leaving the calf/calves without a mother), and relatively large males because of the higher return with respect to meat and trophy. In support of the former view, we found the harvest mortality of adult females to be higher among pre-prime (1–3 years old) than prime-aged age classes (4–7 years old). This is probably because prime-aged females are more fecund and, therefore, more likely to be in company with one or two calves during the hunting season. As the season progressed, however, the selection pressure on barren females decreased, probably due to more productive females becoming ‘legal’ prey as their calf/calves were harvested. In males, we did not find any evidence of strong age-specific hunter selectivity, despite strong age-dependent variation in body mass and antler size. We suggest that this was due to the current strongly female-biased sex ratio in most Norwegian moose populations, which leaves the hunters with few opportunities to be selective within a relatively short and intensive hunting season. The management implications of these findings and to what extent the results are likely to affect the future evolution of life histories in Norwegian moose populations are discussed.Electronic Supplementary Material Supplementary material is available for this article at and accessible for authorised users.  相似文献   
364.
Light-induced damage to photosystem I (PSI) was studied during low-light illumination of barley (Hordeum vulgare L.) at chilling temperatures. A 4-h illumination period induced a significant inactivation of PSI electron transport activity. Flash-induced P700 absorption decay measurements revealed progressive damage to (a) the iron-sulfur clusters FA and FB, (b) the iron-sulfur clusters FA, FB, and FX, and (c) the phylloquinone A1 and the chlorophyll A0 or P700 of the PSI electron acceptor chain. Light-induced PSI damage was also evidenced by partial degradation of the PSI-A and PSI-B proteins and was correlated with the appearance of smaller proteins. Aggravated photodamage was observed upon illumination of barley leaves infiltrated with KCN, which inhibits Cu,Zn-superoxide dismutase and ascorbate peroxidase. This indicates that the photodamage of PSI in barley observed during low-light illumination at chilling temperatures arises because the defense against active oxygen species by active oxygen-scavenging enzymes is insufficient at these specific conditions. The data obtained demonstrate that photoinhibition of PSI at chilling temperatures is an important phenomenon in a cold-tolerant plant species.  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