全文获取类型
收费全文 | 723篇 |
免费 | 48篇 |
专业分类
林业 | 17篇 |
农学 | 24篇 |
基础科学 | 4篇 |
65篇 | |
综合类 | 135篇 |
农作物 | 24篇 |
水产渔业 | 39篇 |
畜牧兽医 | 428篇 |
园艺 | 6篇 |
植物保护 | 29篇 |
出版年
2023年 | 6篇 |
2021年 | 8篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 11篇 |
2017年 | 5篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 9篇 |
2013年 | 29篇 |
2012年 | 14篇 |
2011年 | 23篇 |
2010年 | 25篇 |
2009年 | 22篇 |
2008年 | 18篇 |
2007年 | 34篇 |
2006年 | 35篇 |
2005年 | 35篇 |
2004年 | 22篇 |
2003年 | 26篇 |
2002年 | 28篇 |
2001年 | 23篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 16篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1995年 | 10篇 |
1993年 | 6篇 |
1992年 | 21篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 5篇 |
1983年 | 5篇 |
1980年 | 5篇 |
1979年 | 9篇 |
1977年 | 9篇 |
1976年 | 6篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 10篇 |
1970年 | 4篇 |
1969年 | 5篇 |
1914年 | 4篇 |
1902年 | 4篇 |
排序方式: 共有771条查询结果,搜索用时 15 毫秒
51.
Self-incompatibility: a self-recognition system in plants 总被引:18,自引:0,他引:18
V Haring J E Gray B A McClure M A Anderson A E Clarke 《Science (New York, N.Y.)》1990,250(4983):937-941
Self-incompatibility (SI), a genetically controlled mechanism to prevent inbreeding in plants, offers a relatively simple model system for studying the interactions between plant cells or between a plant cell and the secreted product or products of another cell. Examples of two major types of SI, gametophytic and sporophytic, have been studied by cloning cDNAs corresponding to glycoproteins of the female tissues that segregate with particular variants encoded by the putative S locus. These secreted glycoproteins are envisaged to interact with the currently undescribed pollen component to cause arrest of pollen tube growth. 相似文献
52.
A method for dating geological samples which uses fission product xenon in a manner similar to the use of radiogenic argon in the 40Ar-39Ar technique has been developed. The results of stepwise heating experiments for a zircon from the Ahaggar region in the Sahara are compared to the geochronology determined by the rubidiumstrontium, uranium-thorium-lead, and potassium-argon dating methods. 相似文献
53.
54.
55.
56.
57.
58.
59.
60.
High-resolution spectra of nearby stars show absorption lines due to material in the local interstellar cloud. This cloud is deduced to be moving at 26 kilometers per second with respect to the sun, and in the same direction as the "interstellar wind" flowing through the solar system. Measurements by the Ulysses spacecraft show that neutral helium is drifting through the solar system at the same velocity, but neutral hydrogen appears to be moving at only 20 kilometers per second, a result confirmed by new measurements of the hydrogen emission line taken by the High-Resolution Spectrograph on the Hubble Space Telescope. These results indicate that neutral hydrogen atoms from the local interstellar cloud are preferentially decelerated at the heliospheric interface, most likely by charge-exchange with interstellar protons, while neutral helium is unaffected by the plasma. The magnitude of the observed deceleration implies an interstellar plasma density of 0.06 to 0.10 per cubic centimeter, which in turn implies that the heliospheric shock should be less than 100 astronomical units from the sun. 相似文献