全文获取类型
收费全文 | 341篇 |
免费 | 26篇 |
专业分类
林业 | 9篇 |
农学 | 4篇 |
基础科学 | 2篇 |
41篇 | |
综合类 | 62篇 |
农作物 | 8篇 |
水产渔业 | 19篇 |
畜牧兽医 | 205篇 |
园艺 | 6篇 |
植物保护 | 11篇 |
出版年
2023年 | 2篇 |
2020年 | 5篇 |
2019年 | 3篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 14篇 |
2015年 | 6篇 |
2014年 | 10篇 |
2013年 | 9篇 |
2012年 | 10篇 |
2011年 | 23篇 |
2010年 | 10篇 |
2009年 | 11篇 |
2008年 | 18篇 |
2007年 | 16篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 9篇 |
2003年 | 10篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 2篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 6篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1974年 | 5篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1970年 | 3篇 |
1969年 | 3篇 |
1945年 | 3篇 |
1924年 | 2篇 |
1916年 | 1篇 |
1912年 | 1篇 |
排序方式: 共有367条查询结果,搜索用时 15 毫秒
31.
Heat transfer rates in a basaltic magma were measured under typical magma chamber conditions and a numerical model of the experiment was used to estimate magma viscosity. The results are of value for assessing methods of thermal energy extraction from magma bodies in the upper crust as well as for modeling the evolutionary track of these systems. 相似文献
32.
Tomographic images of upper mantle velocity structure beneath an overlapping spreading center (OSC) on the East Pacific Rise indicate that this ridge axis discontinuity is underlain by a continuous region of low P-wave velocities. The anomalous structure can be explained by an approximately 16-kilometer-wide region of high temperatures and melt fractions of a few percent by volume. Our results show that OSCs are not necessarily associated with a discontinuity in melt supply and that both OSC limbs are supplied with melt from a mantle source located beneath the OSC. We conclude that tectonic segmentation of the ridge by OSCs is not the direct result of magmatic segmentation at mantle depths. 相似文献
33.
34.
Walmsley MJ Ooi SK Reynolds LF Smith SH Ruf S Mathiot A Vanes L Williams DA Cancro MP Tybulewicz VL 《Science (New York, N.Y.)》2003,302(5644):459-462
The Rac1 guanosine triphosphatase (GTPase) has been implicated in multiple cellular functions, including actin dynamics, proliferation, apoptosis, adhesion, and migration resulting from signaling by multiple receptors, including the B cell antigen receptor (BCR). We used conditional gene targeting to generate mice with specific Rac1 deficiency in the B cell lineage. In the absence of both Rac1 and the highly related Rac2, B cell development was almost completely blocked. Both GTPases were required to transduce BCR signals leading to proliferation, survival and up-regulation of BAFF-R, a receptor for BAFF, a key survival molecule required for B cell development and maintenance. 相似文献
35.
Koh LP Dunn RR Sodhi NS Colwell RK Proctor HC Smith VS 《Science (New York, N.Y.)》2004,305(5690):1632-1634
To assess the coextinction of species (the loss of a species upon the loss of another), we present a probabilistic model, scaled with empirical data. The model examines the relationship between coextinction levels (proportion of species extinct) of affiliates and their hosts across a wide range of coevolved interspecific systems: pollinating Ficus wasps and Ficus, parasites and their hosts, butterflies and their larval host plants, and ant butterflies and their host ants. Applying a nomographic method based on mean host specificity (number of host species per affiliate species), we estimate that 6300 affiliate species are "coendangered" with host species currently listed as endangered. Current extinction estimates need to be recalibrated by taking species coextinctions into account. 相似文献
36.
37.
38.
J. S. Morris K. J. Dunn J. M. Dobson R. A. S. White 《The Journal of small animal practice》1996,37(1):1-6
A radiological assessment of 35 canine nasal tumours using an objective scoring system was carried out and related to patient survival. The scoring system demonstrated significant increases in disease-free interval and survival for dogs with scores of less than 12 compared to those with scores of 1 2 or above. 相似文献
39.
40.