全文获取类型
收费全文 | 115篇 |
免费 | 10篇 |
专业分类
林业 | 2篇 |
综合类 | 56篇 |
农作物 | 3篇 |
畜牧兽医 | 62篇 |
园艺 | 1篇 |
植物保护 | 1篇 |
出版年
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 15篇 |
2012年 | 3篇 |
2011年 | 2篇 |
2010年 | 3篇 |
2009年 | 2篇 |
2008年 | 1篇 |
2006年 | 1篇 |
2003年 | 1篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 11篇 |
1997年 | 1篇 |
1996年 | 3篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 5篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 5篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1972年 | 2篇 |
1971年 | 3篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1967年 | 2篇 |
1966年 | 2篇 |
1963年 | 4篇 |
1958年 | 1篇 |
1954年 | 2篇 |
1952年 | 1篇 |
1951年 | 2篇 |
1949年 | 2篇 |
1947年 | 2篇 |
1945年 | 2篇 |
1941年 | 2篇 |
1914年 | 1篇 |
排序方式: 共有125条查询结果,搜索用时 15 毫秒
1.
2.
3.
Navarre WW Porwollik S Wang Y McClelland M Rosen H Libby SJ Fang FC 《Science (New York, N.Y.)》2006,313(5784):236-238
Horizontal gene transfer plays a major role in microbial evolution. However, newly acquired sequences can decrease fitness unless integrated into preexisting regulatory networks. We found that the histone-like nucleoid structuring protein (H-NS) selectively silences horizontally acquired genes by targeting sequences with GC content lower than the resident genome. Mutations in hns are lethal in Salmonella unless accompanied by compensatory mutations in other regulatory loci. Thus, H-NS provides a previously unrecognized mechanism of bacterial defense against foreign DNA, enabling the acquisition of DNA from exogenous sources while avoiding detrimental consequences from unregulated expression of newly acquired genes. Characteristic GC/AT ratios of bacterial genomes may facilitate discrimination between a cell's own DNA and foreign DNA. 相似文献
4.
5.
The radiocarbon content of contemporary pre-bomb marine shells from the upwelling environment of the California and the West Mexican coast has been determined. In addition, factors leading to the apparent ages of different magnitude for various marine environments are discussed. 相似文献
6.
Libby RL 《Science (New York, N.Y.)》1941,93(2419):459-460
7.
8.
Libby WF 《Science (New York, N.Y.)》1968,159(3819):1097-1098
The data on Venus obtained by Mariner V and Venera 4 are interpreted as evidence of giant polar ice caps holding the water that must have come out of the volcanoes with the observed carbon dioxide, on the assumption that Earth and Venus are of similar composition and volcanic history. The measurements by Venera 4 of the equatorial surface temperature indicate that the microwave readings were high, so that the polar ice caps may be allowed to exist in the face of the 10-centimeter readings of polar temperature. Life seems to be distinctly possible at the edges of the ice sheets. 相似文献
9.
10.
J Go I Marsh M Gabor V Saunders RL Reece J Frances C Boys LJ Gabor 《Australian veterinary journal》2012,90(12):513-514
Epizootic ulcerative syndrome was diagnosed, and the presence of Aphanomyces invadans confirmed, from an outbreak of clinical disease in wild‐caught bony bream (Nematalosa erebi) from the Darling River near Bourke, in New South Wales, Australia, during 2008. This confirms a significant extension of the agent beyond its historical range. 相似文献