全文获取类型
收费全文 | 8883篇 |
免费 | 3487篇 |
国内免费 | 1篇 |
专业分类
林业 | 298篇 |
农学 | 481篇 |
基础科学 | 7篇 |
1766篇 | |
综合类 | 293篇 |
农作物 | 232篇 |
水产渔业 | 2625篇 |
畜牧兽医 | 5210篇 |
园艺 | 56篇 |
植物保护 | 1403篇 |
出版年
2023年 | 21篇 |
2022年 | 28篇 |
2021年 | 171篇 |
2020年 | 519篇 |
2019年 | 1089篇 |
2018年 | 942篇 |
2017年 | 983篇 |
2016年 | 986篇 |
2015年 | 852篇 |
2014年 | 868篇 |
2013年 | 1082篇 |
2012年 | 594篇 |
2011年 | 686篇 |
2010年 | 679篇 |
2009年 | 315篇 |
2008年 | 389篇 |
2007年 | 234篇 |
2006年 | 265篇 |
2005年 | 257篇 |
2004年 | 258篇 |
2003年 | 243篇 |
2002年 | 230篇 |
2001年 | 101篇 |
2000年 | 122篇 |
1999年 | 29篇 |
1998年 | 22篇 |
1997年 | 29篇 |
1996年 | 27篇 |
1995年 | 19篇 |
1994年 | 27篇 |
1993年 | 21篇 |
1992年 | 14篇 |
1991年 | 16篇 |
1990年 | 10篇 |
1989年 | 10篇 |
1987年 | 10篇 |
1986年 | 12篇 |
1985年 | 12篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 12篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1975年 | 8篇 |
1973年 | 8篇 |
1970年 | 10篇 |
1969年 | 12篇 |
1966年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
781.
Russell CA Jones TC Barr IG Cox NJ Garten RJ Gregory V Gust ID Hampson AW Hay AJ Hurt AC de Jong JC Kelso A Klimov AI Kageyama T Komadina N Lapedes AS Lin YP Mosterin A Obuchi M Odagiri T Osterhaus AD Rimmelzwaan GF Shaw MW Skepner E Stohr K Tashiro M Fouchier RA Smith DJ 《Science (New York, N.Y.)》2008,320(5874):340-346
Antigenic and genetic analysis of the hemagglutinin of approximately 13,000 human influenza A (H3N2) viruses from six continents during 2002-2007 revealed that there was continuous circulation in east and Southeast Asia (E-SE Asia) via a region-wide network of temporally overlapping epidemics and that epidemics in the temperate regions were seeded from this network each year. Seed strains generally first reached Oceania, North America, and Europe, and later South America. This evidence suggests that once A (H3N2) viruses leave E-SE Asia, they are unlikely to contribute to long-term viral evolution. If the trends observed during this period are an accurate representation of overall patterns of spread, then the antigenic characteristics of A (H3N2) viruses outside E-SE Asia may be forecast each year based on surveillance within E-SE Asia, with consequent improvements to vaccine strain selection. 相似文献
782.
Long-range correlations in the diffuse seismic coda 总被引:9,自引:0,他引:9
The late seismic coda may contain coherent information about the elastic response of Earth. We computed the correlations of the seismic codas of 101 distant earthquakes recorded at stations that were tens of kilometers apart. By stacking cross-correlation functions of codas, we found a low-frequency coherent part in the diffuse field. The extracted pulses have the polarization characteristics and group velocities expected for Rayleigh and Love waves. The set of cross-correlations has the symmetries of the surface-wave part of the Green tensor. This seismological example shows that diffuse waves produced by distant sources are sufficient to retrieve direct waves between two perfectly located points of observation. Because it relies on general properties of diffuse waves, this result has potential applications in other fields. 相似文献
783.
Making the transition from postdoc to independent investigator is tough. Scientists who received prestigious fellowships or grants relate their experiences-and offer some advice. 相似文献
784.
Curran MA van Ommen TD Morgan VI Phillips KL Palmer AS 《Science (New York, N.Y.)》2003,302(5648):1203-1206
The instrumental record of Antarctic sea ice in recent decades does not reveal a clear signature of warming despite observational evidence from coastal Antarctica. Here we report a significant correlation (P < 0.002) between methanesulphonic acid (MSA) concentrations from a Law Dome ice core and 22 years of satellite-derived sea ice extent (SIE) for the 80 degrees E to 140 degrees E sector. Applying this instrumental calibration to longer term MSA data (1841 to 1995 A.D.) suggests that there has been a 20% decline in SIE since about 1950. The decline is not uniform, showing large cyclical variations, with periods of about 11 years, that confuse trend detection over the relatively short satellite era. 相似文献
785.
786.
787.
Beckman M 《Science (New York, N.Y.)》2002,297(5587):1626-1627
788.
789.
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
790.