全文获取类型
收费全文 | 907篇 |
免费 | 47篇 |
国内免费 | 2篇 |
专业分类
林业 | 37篇 |
农学 | 40篇 |
基础科学 | 6篇 |
153篇 | |
综合类 | 112篇 |
农作物 | 52篇 |
水产渔业 | 34篇 |
畜牧兽医 | 444篇 |
园艺 | 16篇 |
植物保护 | 62篇 |
出版年
2023年 | 5篇 |
2021年 | 18篇 |
2020年 | 23篇 |
2019年 | 21篇 |
2018年 | 16篇 |
2017年 | 19篇 |
2016年 | 15篇 |
2015年 | 11篇 |
2014年 | 13篇 |
2013年 | 38篇 |
2012年 | 37篇 |
2011年 | 49篇 |
2010年 | 43篇 |
2009年 | 22篇 |
2008年 | 38篇 |
2007年 | 44篇 |
2006年 | 42篇 |
2005年 | 46篇 |
2004年 | 35篇 |
2003年 | 41篇 |
2002年 | 54篇 |
2001年 | 19篇 |
2000年 | 19篇 |
1999年 | 21篇 |
1998年 | 11篇 |
1997年 | 12篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1992年 | 12篇 |
1991年 | 16篇 |
1990年 | 13篇 |
1989年 | 7篇 |
1988年 | 12篇 |
1987年 | 7篇 |
1986年 | 11篇 |
1985年 | 11篇 |
1984年 | 7篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 8篇 |
1973年 | 4篇 |
1972年 | 5篇 |
1969年 | 4篇 |
1967年 | 4篇 |
1943年 | 5篇 |
排序方式: 共有956条查询结果,搜索用时 15 毫秒
61.
Chapman HN 《Science (New York, N.Y.)》2008,321(5887):352-353
62.
Shocks in ion sputtering sharpen steep surface features 总被引:1,自引:0,他引:1
Chen HH Urquidez OA Ichim S Rodriquez LH Brenner MP Aziz MJ 《Science (New York, N.Y.)》2005,310(5746):294-297
We report a regime of ion beam sputtering that occurs for sufficiently steep slopes. High slopes propagate over large distances without dissipating the steepest features. Both the propagation velocity and the dynamically selected slope are universal, independent of the details of the initial shape of the surface. The resulting behavior can be understood as the propagation of a shock front that self-selects a stable slope, as has been previously observed in thin-film fluid flows. Experiments confirm predictions of the theory. An important implication of the propagative behavior at high surface slopes is that a pattern can be fabricated at a large length scale and, through uniform ion irradiation, reduced to a smaller length scale while preserving, or even sharpening, the sharpest features. 相似文献
63.
64.
Modern laser technology has revolutionized the sensitivity and precision of spectroscopy by providing coherent light in a spectrum spanning the infrared, visible, and ultraviolet wavelength regimes. However, the generation of shorter-wavelength coherent pulses in the x-ray region has proven much more challenging. The recent emergence of high harmonic generation techniques opens the door to this possibility. Here we review the new science that is enabled by an ability to manipulate and control electrons on attosecond time scales, ranging from new tabletop sources of coherent x-rays to an ability to follow complex electron dynamics in molecules and materials. We also explore the implications of these advances for the future of molecular structural characterization schemes that currently rely so heavily on scattering from incoherent x-ray sources. 相似文献
65.
66.
A record of foraminiferal shell weight across glacial-interglacial Termination I shows a response related to seawater carbonate ion concentration and allows reconstruction of a record of carbon dioxide in surface seawater that matches the atmospheric record. The results support suggestions that higher atmospheric carbon dioxide directly affects marine calcification, an effect that may be of global importance to past and future changes in atmospheric CO2. The process provides negative feedback to the influence of marine calcification on atmospheric carbon dioxide and is of practical importance to the application of paleoceanographic proxies. 相似文献
67.
68.
Atlas R Campbell P Cozzarelli NR Curfman G Enquist L Fink G Flanagin A Fletcher J George E Hammes G Heyman D Inglesby T Kaplan S Kennedy D Krug J Levinson R Marcus E Metzger H Morse SS O'Brien A Onderdonk A Poste G Renault B Rich R Rosengard A Salzburg S Scanlan M Shenk T Tabor H Varmus H Wimmer E Yamamoto K;Journal Editors Authors Group 《Science (New York, N.Y.)》2003,299(5610):1149
69.
70.