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   210篇
  免费   41篇
  2021年   3篇
  2018年   4篇
  2016年   5篇
  2015年   4篇
  2014年   7篇
  2013年   7篇
  2012年   15篇
  2011年   14篇
  2010年   3篇
  2009年   8篇
  2008年   11篇
  2007年   11篇
  2006年   5篇
  2005年   8篇
  2004年   2篇
  2003年   7篇
  2002年   8篇
  2001年   2篇
  2000年   6篇
  1999年   5篇
  1998年   2篇
  1997年   2篇
  1996年   2篇
  1993年   2篇
  1992年   2篇
  1991年   3篇
  1990年   5篇
  1989年   2篇
  1988年   6篇
  1987年   3篇
  1986年   4篇
  1985年   5篇
  1984年   6篇
  1983年   2篇
  1982年   3篇
  1981年   2篇
  1980年   2篇
  1978年   4篇
  1977年   4篇
  1976年   6篇
  1975年   2篇
  1974年   2篇
  1973年   4篇
  1972年   6篇
  1971年   4篇
  1968年   6篇
  1967年   6篇
  1966年   4篇
  1965年   3篇
  1964年   2篇
排序方式: 共有251条查询结果,搜索用时 15 毫秒
41.
42.
43.
The energy expenditure of the tūī (Prosthemadera novaeseelandiae), a meliphagid endemic to New Zealand, was measured and compared with 20 species of honeyeaters (family Meliphagidae) to determine whether its expenditure is influenced either by life in a moist, temperate climate or an island residence. Body mass in the honeyeaters accounted for 91.5% of the variation in basal rate. The combination of body mass, climate and the maximal limit to an altitudinal distribution explained 98.6% of the variation in basal rate with tropical, low-altitude species having the highest mass-independent rate. The basal rates of meliphagids in tropical highlands are similar to those in temperate lowlands, which may reflect similar food supplies. The tūī mass-independent expenditure appears to reflect an active lifestyle in a temperate climate with no evidence that an island residence influenced its rate, whereas sedentary birds on New Zealand have responded to island life with a depressed basal rate. An effective analysis of the variation in energy expenditure requires the inclusion of the ecological and behavioural characteristics that distinguish species.  相似文献   
44.
45.
The design, synthesis, and biological activity of a series of cycloalkene acid-based niacin receptor agonists are described. This led to the discovery that tetrahydro anthranilic acid is an excellent surrogate for anthranilic acid. Several compounds were identified that were potent against the niacin receptor, had enhanced cytochrome P450 selectivity against subtypes CYP2C8 and CYP2C9, and improved oral exposure in mice.  相似文献   
46.
Platensimycin (1) displays antibacterial activity due to its inhibition of the elongation condensing enzyme (FabF), a novel mode of action that could potentially lead to a breakthrough in developing a new generation of antibiotics. The medicinal chemistry efforts were focused on the modification of the enone moiety of platensimycin and several analogs showed significant activity against FabF and possess antibacterial activity.  相似文献   
47.
Spirocyclic secondary amine-derived trisubstituted ureas were identified as highly potent, bioavailable and selective soluble epoxide hydrolase (sEH) inhibitors. Despite good oral exposure and excellent ex vivo target engagement in blood, one such compound, rac-1a, failed to lower blood pressure acutely in spontaneously hypertensive rats (SHRs). This study posed the question as to whether sEH inhibition provides a robust mechanism leading to a significant antihypertensive effect.  相似文献   
48.
49.
We present a mathematical method for acceleration workspace analysis of cooperating multi-finger robot systems using a model of point-contact with friction. A new unified formulation from dynamic equations of cooperating multi-finger robots is derived considering the force and acceleration relationships between the fingers and the object to be handled. From the dynamic equation, maximum translational and rotational acceleration bounds of an object are calculated under given constraints of contact conditions, configurations of fingers, and bounds on the torques of joint actuators for each finger. Here, the rotational acceleration bounds can be applied as an important manipulability index when the multi-finger robot grasps an object. To verify the proposed method, we used a set of case studies with a simple multi-finger mechanism system. The achievable acceleration boundary in task space can be obtained successfully with the proposed method and the acceleration boundary depends on the configurations of fingers.  相似文献   
50.
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