全文获取类型
收费全文 | 282篇 |
免费 | 4篇 |
专业分类
林业 | 13篇 |
农学 | 12篇 |
36篇 | |
综合类 | 11篇 |
农作物 | 12篇 |
水产渔业 | 29篇 |
畜牧兽医 | 113篇 |
园艺 | 3篇 |
植物保护 | 57篇 |
出版年
2022年 | 3篇 |
2021年 | 4篇 |
2020年 | 1篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 6篇 |
2016年 | 8篇 |
2015年 | 4篇 |
2014年 | 13篇 |
2013年 | 11篇 |
2012年 | 19篇 |
2011年 | 22篇 |
2010年 | 7篇 |
2009年 | 13篇 |
2008年 | 18篇 |
2007年 | 28篇 |
2006年 | 10篇 |
2005年 | 21篇 |
2004年 | 26篇 |
2003年 | 17篇 |
2002年 | 16篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 4篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1975年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有286条查询结果,搜索用时 15 毫秒
281.
282.
Continuous plasma outflows from the edge of a solar active region as a possible source of solar wind
Sakao T Kano R Narukage N Kotoku J Bando T Deluca EE Lundquist LL Tsuneta S Harra LK Katsukawa Y Kubo M Hara H Matsuzaki K Shimojo M Bookbinder JA Golub L Korreck KE Su Y Shibasaki K Shimizu T Nakatani I 《Science (New York, N.Y.)》2007,318(5856):1585-1588
The Sun continuously expels a huge amount of ionized material into interplanetary space as the solar wind. Despite its influence on the heliospheric environment, the origin of the solar wind has yet to be well identified. In this paper, we report Hinode X-ray Telescope observations of a solar active region. At the edge of the active region, located adjacent to a coronal hole, a pattern of continuous outflow of soft-x-ray-emitting plasmas was identified emanating along apparently open magnetic field lines and into the upper corona. Estimates of temperature and density for the outflowing plasmas suggest a mass loss rate that amounts to approximately 1/4 of the total mass loss rate of the solar wind. These outflows may be indicative of one of the solar wind sources at the Sun. 相似文献
283.
284.
Summary Haploid plants (2n=12) were produced by anther culture from the tuber-bearing wild speciesS. verrucosum. 相似文献
285.
Larvicidal and adulticidal activity of alkylphthalide derivatives from rhizome of Cnidium officinale against Drosophila melanogaster 总被引:1,自引:0,他引:1
The insecticidal activity of the chloroform extract of Cnidium officinale rhizomes and its constituents was investigated against larvae and adults of Drosophila melanogaster and compared with that of rotenone. Bioassay-guided isolation of the chloroform extract of C. officinale resulted in the isolation and characterization of four alkylphthalides, cnidilide (1), (Z)-ligustilide (2), (3S)-butylphthalide (3), and neocnidilide (4). The structures of these compounds were established by spectroscopic analysis. The isolated compounds 2, 3, and 4 exhibited LC50 values of 2.54, 4.99, and 9.90 micromol/mL of diet concentration against larvae of D. melanogaster, respectively. Against both sexes (males/females, 1:1) of adults (5-7 days old), compound 3 showed the most potent activity of the compounds isolated with the LD50 value of 5.93 microg/adult, comparable to that of rotenone (LD50 = 3.68 microg/adult). Structure-activity relationships of phthalides isolated suggest that the presence of conjugation with the carbonyl group in the lactone ring appeared to play an important role in the larvicidal activity. Acetylcholinesterase (prepared from the adult heads of D. melanogaster) inhibitory activity was also investigated in vitro to determine the insecticide mode of action for the acute adulticidal activity. 相似文献
286.