全文获取类型
| 收费全文 | 1065篇 |
| 免费 | 16篇 |
| 国内免费 | 3篇 |
专业分类
| 林业 | 26篇 |
| 农学 | 14篇 |
| 基础科学 | 9篇 |
| 98篇 | |
| 综合类 | 268篇 |
| 农作物 | 14篇 |
| 水产渔业 | 96篇 |
| 畜牧兽医 | 362篇 |
| 园艺 | 1篇 |
| 植物保护 | 196篇 |
出版年
| 2023年 | 9篇 |
| 2022年 | 21篇 |
| 2021年 | 23篇 |
| 2020年 | 18篇 |
| 2019年 | 9篇 |
| 2017年 | 12篇 |
| 2015年 | 10篇 |
| 2014年 | 9篇 |
| 2013年 | 26篇 |
| 2012年 | 27篇 |
| 2011年 | 24篇 |
| 2010年 | 31篇 |
| 2009年 | 39篇 |
| 2008年 | 30篇 |
| 2007年 | 37篇 |
| 2006年 | 35篇 |
| 2005年 | 18篇 |
| 2004年 | 11篇 |
| 2003年 | 10篇 |
| 2002年 | 12篇 |
| 1998年 | 22篇 |
| 1997年 | 27篇 |
| 1996年 | 32篇 |
| 1995年 | 27篇 |
| 1994年 | 25篇 |
| 1993年 | 32篇 |
| 1992年 | 25篇 |
| 1991年 | 23篇 |
| 1990年 | 17篇 |
| 1989年 | 23篇 |
| 1988年 | 16篇 |
| 1987年 | 29篇 |
| 1986年 | 24篇 |
| 1985年 | 16篇 |
| 1984年 | 10篇 |
| 1983年 | 11篇 |
| 1982年 | 13篇 |
| 1981年 | 21篇 |
| 1980年 | 18篇 |
| 1979年 | 21篇 |
| 1978年 | 10篇 |
| 1977年 | 10篇 |
| 1976年 | 12篇 |
| 1959年 | 10篇 |
| 1958年 | 15篇 |
| 1957年 | 9篇 |
| 1954年 | 8篇 |
| 1947年 | 8篇 |
| 1945年 | 9篇 |
| 1940年 | 9篇 |
排序方式： 共有1084条查询结果，搜索用时 375 毫秒
101.
The level of the plasma prothrombin in the circulating blood is decreased during its passage through the pulmonary capillaries. In 85 per cent. of samples, plasma prothrombin has been found to be less in the blood of the left ventricle than in that from the right ventricle. This difference averaged 10.6 per cent. and ranged from 4 to 19 per cent. In no instance was the level in the right ventricle lower than that in the left. In samples of blood taken from the arterial and venous supply of the head, liver, spleen, intestine, kidney and hind limbs, no significant difference in plasma prothrombin levels was found. A possible explanation of this role of the lung in the loss of plasma prothrombin is thought to be the production of blood platelets in this organ, as demonstrated by Howell and Donahue. Platelets, as they undergo disintegration, initiate the first stage of the clotting process by releasing thromboplastin, which, in the presence of calcium, changes prothrombin to thrombin. 相似文献
102.
The relative rates of racemization for amino acid residues at the NH(2) and COOH ends of 37 different dipeptides were determined. In nine dipeptides containing alanine, leucine, phenylalanine, aspartic acid, and methionine, the amino acid residue racemized faster at the COOH-terminal position than at the NH(2)-terminal position (COOH > NH(2)). The sterically hindered amino acids isoleucine and valine showed NH(2) > COOH. Six proline dipeptides showed NH(2) > COOH. Intramolecular effects have been invoked to explain these surprising results. 相似文献
103.
104.
Cimino G DE Rosa S DE Stefano S Sodano G Villani G 《Science (New York, N.Y.)》1983,219(4589):1237-1238
A biosynthetic experiment with mevalonic acid labeled with carbon-14 showed that the nudibranch Dendrodoris limbata elaborates polygodial, a sesquiterpenoid dialdehyde stored in the mantle, which constitutes its chemical defense against predators. Previously described nudibranchs drew defensive chemicals from their preys. 相似文献
105.
106.
VAN Allen JA 《Science (New York, N.Y.)》1986,232(4754):1075-1076
107.
108.
Hynds RJ Cowley SW Sanderson TR Wenzel KP VAN Rooijen JJ 《Science (New York, N.Y.)》1986,232(4748):361-365
During the encounter with comet Giacobini-Zinner, the energetic particle anisotropy spectrometer on the International Cometary Explorer spacecraft observed large fluxes of energetic ions, believed to result principally from ionization of the cometary atmosphere followed by pickup and acceleration by the ambient flow of the solar wind. These heavy cometary ions were observed from approximately 1 day before closest approach to about 2(1/2) days afterward. Three regimes of differing ion characteristics have been identified. An outer region with a scale of approximately 10(6) kilometers contains variable fluxes of antisolar-streaming pick-up ions in the undisturbed solar wind. In the middle region, of approximately 10(5) kilometers, fluxes have less large-scale variability and broader angular and energy distributions. This region is separated from the outer zone by a sharp transition. The inner region has a scale of approximately 10(4) kilometers and is characterized by reduced fluxes and complex angular distributions. 相似文献
109.
110.