全文获取类型
收费全文 | 1679篇 |
免费 | 110篇 |
专业分类
林业 | 98篇 |
农学 | 29篇 |
基础科学 | 11篇 |
255篇 | |
综合类 | 357篇 |
农作物 | 60篇 |
水产渔业 | 105篇 |
畜牧兽医 | 773篇 |
园艺 | 36篇 |
植物保护 | 65篇 |
出版年
2023年 | 16篇 |
2022年 | 23篇 |
2021年 | 41篇 |
2020年 | 49篇 |
2019年 | 51篇 |
2018年 | 37篇 |
2017年 | 35篇 |
2016年 | 47篇 |
2015年 | 24篇 |
2014年 | 43篇 |
2013年 | 65篇 |
2012年 | 103篇 |
2011年 | 121篇 |
2010年 | 68篇 |
2009年 | 50篇 |
2008年 | 115篇 |
2007年 | 90篇 |
2006年 | 95篇 |
2005年 | 72篇 |
2004年 | 56篇 |
2003年 | 72篇 |
2002年 | 70篇 |
2001年 | 17篇 |
2000年 | 13篇 |
1999年 | 14篇 |
1996年 | 13篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 15篇 |
1991年 | 13篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1988年 | 8篇 |
1987年 | 10篇 |
1986年 | 18篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 9篇 |
1979年 | 11篇 |
1978年 | 12篇 |
1977年 | 10篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1973年 | 12篇 |
1972年 | 7篇 |
1971年 | 13篇 |
1969年 | 12篇 |
1968年 | 7篇 |
1967年 | 13篇 |
排序方式: 共有1789条查询结果,搜索用时 625 毫秒
121.
122.
123.
124.
125.
Gas chromatography for detection of viral infections 总被引:2,自引:0,他引:2
Gas chromatograms of sertim extracts of dogs inoculated with canine infectious hepatitis virus showed two metabolites not observed in uninoculated animals. Chromatograms of extracts of tissue cultures of dog kidney, inoculated with viruses causing canine hepatitis, herpes, and distemper, and a parainfluenza virus similar to simian virus-5, each showed two or more different metabolites. Two of the distinguishing products from cultures inoculated with hepatitis virus were chromatographically indistinguishable from those found in serums of the animals. 相似文献
126.
Warwick JW Evans DR Romig JH Alexander JK Desch MD Kaiser ML Aubier M Leblanc Y Lecacheux A Pedersen BM 《Science (New York, N.Y.)》1982,215(4532):582-587
Planetary radio astronomy measurements obtained by Voyager 2 near Saturn have added further evidence that Saturnian kilometric radiation is emitted by a strong dayside source at auroral latitudes in the northern hemisphere and by a weaker source at complementary latitudes in the southern hemisphere. These emissions are variable because of Saturn's rotation and, on longer time scales, probably because of influences of the solar wind and Dione. The electrostatic discharge bursts first discovered by Voyager 1 and attributed to emissions from the B ring were again observed with the same broadband spectral properties and an episodic recurrence period of about 10 hours, but their occurrence frequency was only about 30 percent of that detected by Voyager 1. While crossing the ring plane at a distance of 2.88 Saturn radii, the spacecraft detected an intense noise event extending to above 1 megahertz and lasting about 150 seconds. The event is interpreted to be a consequence of the impact, vaporization, and ionization of charged, micrometer-size G ring particles distributed over a vertical thickness of about 1500 kilometers. 相似文献
127.
128.
Alexander RM 《Science (New York, N.Y.)》2003,301(5640):1678-1679
The largest living rodent is the South American capybara, a creature the size of a sheep that unlike smaller rodents stands on relatively straight legs. However, as Alexander explains in his Perspective, a new fossil find in Venezuela (Sánchez-Villagra et al.) reveals that the capybara would be dwarfed by Phoberomys, a giant rodent the size of a buffalo that lived during the Miocene Epoch. 相似文献
129.
Bouchard LS Burt SR Anwar MS Kovtunov KV Koptyug IV Pines A 《Science (New York, N.Y.)》2008,319(5862):442-445
Catalysis is vital to industrial chemistry, and the optimization of catalytic reactors attracts considerable resources. It has proven challenging to correlate the active regions in heterogeneous catalyst beds with morphology and to monitor multistep reactions within the bed. We demonstrate techniques, using magnetic resonance imaging and para-hydrogen (p-H2) polarization, that allow direct visualization of gas-phase flow and the density of active catalyst in a packed-bed microreactor, as well as control over the dynamics of the polarized state in space and time to facilitate the study of subsequent reactions. These procedures are suitable for characterizing reactors and reactions in microfluidic devices where low sensitivity of conventional magnetic resonance would otherwise be the limiting factor. 相似文献
130.