全文获取类型
收费全文 | 98篇 |
免费 | 0篇 |
专业分类
理论与方法论 | 2篇 |
现状及发展 | 15篇 |
研究方法 | 15篇 |
综合类 | 61篇 |
自然研究 | 5篇 |
出版年
2021年 | 2篇 |
2018年 | 1篇 |
2013年 | 1篇 |
2012年 | 4篇 |
2011年 | 10篇 |
2010年 | 1篇 |
2008年 | 4篇 |
2007年 | 3篇 |
2006年 | 3篇 |
2005年 | 4篇 |
2004年 | 5篇 |
2003年 | 10篇 |
2002年 | 2篇 |
2001年 | 6篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1996年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 2篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1965年 | 4篇 |
排序方式: 共有98条查询结果,搜索用时 15 毫秒
31.
Switzer WM Salemi M Shanmugam V Gao F Cong ME Kuiken C Bhullar V Beer BE Vallet D Gautier-Hion A Tooze Z Villinger F Holmes EC Heneine W 《Nature》2005,434(7031):376-380
Although parasite-host co-speciation is a long-held hypothesis, convincing evidence for long-term co-speciation remains elusive, largely because of small numbers of hosts and parasites studied and uncertainty over rates of evolutionary change. Co-speciation is especially rare in RNA viruses, in which cross-species transfer is the dominant mode of evolution. Simian foamy viruses (SFVs) are ubiquitous, non-pathogenic retroviruses that infect all primates. Here we test the co-speciation hypothesis in SFVs and their primate hosts by comparing the phylogenies of SFV polymerase and mitochondrial cytochrome oxidase subunit II from African and Asian monkeys and apes. The phylogenetic trees were remarkably congruent in both branching order and divergence times, strongly supporting co-speciation. Molecular clock calibrations revealed an extremely low rate of SFV evolution, 1.7 x 10(-8) substitutions per site per year, making it the slowest-evolving RNA virus documented so far. These results indicate that SFVs might have co-speciated with Old World primates for at least 30 million years, making them the oldest known vertebrate RNA viruses. 相似文献
32.
33.
J.A.Holmes 《科学通报(英文版)》2003,48(14)
This special issue of Chinese Science Bulletin arose from a symposium entitled 揂brupt EnvironmentalChanges in Arid Asia——History and Mechanisms?RACHAD 2001) held at Lanzhou University in October 2001. This international event was attended by over 70 scientists from Australia, China, Germany, India,Mongolia, Russia, the UK and the USA. More than fifty papers were given over a three-day period on all aspects of the mechanisms and history of environmental change in Asia抯 drylands.… 相似文献
34.
35.
Specific degranulation of human polymorphonuclear leukocytes 总被引:26,自引:0,他引:26
36.
A W Holmes F Deinhardt L Wolfe G Froesner D Paterson B Casto M E Conrad 《Nature》1973,243(5407):419-420
37.
38.
39.
The second nesting record for the Great - tailed Grackle ( Quiscalus mexicanus ) in Nevada is reported from the central part of the state approximately 240 km north of the previous record. Since 1912 this species has undergone a dramatic northward extension of its previous range in the United States, presumably as a result of increased agricultural irrigation in areas that were previously desert or short - grass prairie. 相似文献
40.