全文获取类型
收费全文 | 1190篇 |
免费 | 66篇 |
国内免费 | 2篇 |
专业分类
林业 | 39篇 |
农学 | 49篇 |
基础科学 | 7篇 |
195篇 | |
综合类 | 169篇 |
农作物 | 69篇 |
水产渔业 | 52篇 |
畜牧兽医 | 590篇 |
园艺 | 17篇 |
植物保护 | 71篇 |
出版年
2023年 | 13篇 |
2022年 | 13篇 |
2021年 | 22篇 |
2020年 | 32篇 |
2019年 | 32篇 |
2018年 | 22篇 |
2017年 | 25篇 |
2016年 | 18篇 |
2015年 | 22篇 |
2014年 | 17篇 |
2013年 | 51篇 |
2012年 | 58篇 |
2011年 | 67篇 |
2010年 | 42篇 |
2009年 | 24篇 |
2008年 | 51篇 |
2007年 | 64篇 |
2006年 | 62篇 |
2005年 | 66篇 |
2004年 | 55篇 |
2003年 | 53篇 |
2002年 | 69篇 |
2001年 | 21篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 16篇 |
1997年 | 15篇 |
1996年 | 10篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 13篇 |
1991年 | 20篇 |
1990年 | 15篇 |
1989年 | 6篇 |
1988年 | 13篇 |
1987年 | 10篇 |
1986年 | 14篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1980年 | 5篇 |
1979年 | 11篇 |
1978年 | 8篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1975年 | 9篇 |
1974年 | 9篇 |
1972年 | 6篇 |
1967年 | 6篇 |
1943年 | 5篇 |
排序方式: 共有1258条查询结果,搜索用时 15 毫秒
91.
92.
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
93.
94.
95.
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
96.
97.
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
98.
99.
100.
Surface- and volume-limited chemical reactions on and in atmospheric aerosol particles cause growth while changing organic composition by 13 to 24% per day. Many of these particles contain carbonaceous components from mineral dust and combustion emissions in Africa, Asia, and North America and reveal reaction rates that are three times slower than those typically used in climate models. These slower rates for converting from volatile or hydrophobic to condensed and hygroscopic organic compounds increase carbonaceous particle burdens in climate models by 70%, producing organic aerosol climate forcings of as much as -0.8 watt per square meter cooling and +0.3 watt per square meter warming. 相似文献