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   33421篇
  免费   3005篇
  国内免费   24篇
  36450篇
  2023年   168篇
  2022年   376篇
  2021年   791篇
  2020年   422篇
  2019年   567篇
  2018年   672篇
  2017年   556篇
  2016年   988篇
  2015年   1683篇
  2014年   1765篇
  2013年   2091篇
  2012年   2738篇
  2011年   2755篇
  2010年   1682篇
  2009年   1406篇
  2008年   2093篇
  2007年   2067篇
  2006年   2002篇
  2005年   1734篇
  2004年   1746篇
  2003年   1546篇
  2002年   1502篇
  2001年   350篇
  2000年   275篇
  1999年   346篇
  1998年   328篇
  1997年   240篇
  1996年   220篇
  1995年   200篇
  1994年   167篇
  1993年   171篇
  1992年   168篇
  1991年   192篇
  1990年   141篇
  1989年   130篇
  1988年   116篇
  1987年   107篇
  1986年   115篇
  1985年   116篇
  1984年   117篇
  1983年   111篇
  1982年   131篇
  1981年   130篇
  1980年   100篇
  1979年   91篇
  1978年   79篇
  1976年   65篇
  1975年   76篇
  1974年   63篇
  1973年   73篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
For decades, the bio-duck sound has been recorded in the Southern Ocean, but the animal producing it has remained a mystery. Heard mainly during austral winter in the Southern Ocean, this ubiquitous sound has been recorded in Antarctic waters and contemporaneously off the Australian west coast. Here, we present conclusive evidence that the bio-duck sound is produced by Antarctic minke whales (Balaenoptera bonaerensis). We analysed data from multi-sensor acoustic recording tags that included intense bio-duck sounds as well as singular downsweeps that have previously been attributed to this species. This finding allows the interpretation of a wealth of long-term acoustic recordings for this previously acoustically concealed species, which will improve our understanding of the distribution, abundance and behaviour of Antarctic minke whales. This is critical information for a species that inhabits a difficult to access sea-ice environment that is changing rapidly in some regions and has been the subject of contentious lethal sampling efforts and ongoing international legal action.  相似文献   
4.
R Patterson 《CMAJ》1999,161(7):853
  相似文献   
5.
We undertook a 2-year (2002–2004) mark–recapture study to investigate demographic performance and habitat use of salt marsh harvest mice (Reithrodontomys raviventris halicoetes) in the Suisun Marsh. We examined the effects of different wetland types and microhabitats on 3 demographic variables: density, reproductive potential, and persistence. Our results indicate that microhabitats dominated by mixed vegetation or pickleweed (Salicornia spp.) supported similar salt marsh harvest mouse densities, reproductive potential, and persistence throughout much of the year, whereas few salt marsh harvest mice inhabited upland grass-dominated microhabitats. We found that densities were higher in diked wetlands, whereas post-winter persistence was higher in tidal wetlands, and reproductive potential did not differ statistically between wetland types. Our results emphasize the importance of mixed vegetation for providing adequate salt marsh harvest mouse habitat and suggest that, despite their physiognomic and hydrological differences, both diked and tidal wetlands support salt marsh harvest mouse populations by promoting different demographic attributes. We recommend that habitat management, restoration, and enhancement efforts include areas containing mixed vegetation in addition to pickleweed in both diked and tidal wetlands. © 2011 The Wildlife Society.  相似文献   
6.
Connective tissue growth factor (CTGF/CCN2) is overexpressed in diabetes. Diabetic rats possess myocardial and cardiomyocyte hypertrophy. In a recent report, Wang and colleagues (Am J Physiol Cell Physiol. 2009 Jul 22. [Epub ahead of print]) show that CCN2 directly mediates cardiomyocyte hypertrophy as well as that induced by high glucose and fatty acid. CCN2 acted via the TrkA receptor. These data are the subject of this commentary, and emphasize that CCN2 may be an excellent target for therapy in diabetes.  相似文献   
7.
8.
9.
10.
Andrew C. Harper 《CMAJ》1980,123(5):400-401
  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