全文获取类型
收费全文 | 543篇 |
免费 | 64篇 |
专业分类
林业 | 21篇 |
农学 | 5篇 |
基础科学 | 3篇 |
51篇 | |
综合类 | 170篇 |
农作物 | 12篇 |
水产渔业 | 46篇 |
畜牧兽医 | 251篇 |
园艺 | 13篇 |
植物保护 | 35篇 |
出版年
2023年 | 4篇 |
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 10篇 |
2017年 | 12篇 |
2016年 | 4篇 |
2015年 | 13篇 |
2014年 | 13篇 |
2013年 | 12篇 |
2012年 | 63篇 |
2011年 | 66篇 |
2010年 | 25篇 |
2009年 | 17篇 |
2008年 | 44篇 |
2007年 | 46篇 |
2006年 | 53篇 |
2005年 | 46篇 |
2004年 | 29篇 |
2003年 | 35篇 |
2002年 | 40篇 |
2001年 | 6篇 |
2000年 | 6篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 5篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 5篇 |
1992年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1981年 | 1篇 |
排序方式: 共有607条查询结果,搜索用时 46 毫秒
141.
142.
143.
Miller G 《Science (New York, N.Y.)》2006,312(5782):1860-1861
144.
145.
146.
Waite JH Combi MR Ip WH Cravens TE McNutt RL Kasprzak W Yelle R Luhmann J Niemann H Gell D Magee B Fletcher G Lunine J Tseng WL 《Science (New York, N.Y.)》2006,311(5766):1419-1422
The Cassini spacecraft passed within 168.2 kilometers of the surface above the southern hemisphere at 19:55:22 universal time coordinated on 14 July 2005 during its closest approach to Enceladus. Before and after this time, a substantial atmospheric plume and coma were observed, detectable in the Ion and Neutral Mass Spectrometer (INMS) data set out to a distance of over 4000 kilometers from Enceladus. INMS data indicate that the atmospheric plume and coma are dominated by water, with significant amounts of carbon dioxide, an unidentified species with a mass-to-charge ratio of 28 daltons (either carbon monoxide or molecular nitrogen), and methane. Trace quantities (<1%) of acetylene and propane also appear to be present. Ammonia is present at a level that does not exceed 0.5%. The radial and angular distributions of the gas density near the closest approach, as well as other independent evidence, suggest a significant contribution to the plume from a source centered near the south polar cap, as distinct from a separately measured more uniform and possibly global source observed on the outbound leg of the flyby. 相似文献
147.
Miller G 《Science (New York, N.Y.)》2006,311(5763):938-940
148.
Miller G 《Science (New York, N.Y.)》2006,311(5763):935
149.
Simultaneously mitigating near-term climate change and improving human health and food security 总被引:3,自引:0,他引:3
Shindell D Kuylenstierna JC Vignati E van Dingenen R Amann M Klimont Z Anenberg SC Muller N Janssens-Maenhout G Raes F Schwartz J Faluvegi G Pozzoli L Kupiainen K Höglund-Isaksson L Emberson L Streets D Ramanathan V Hicks K Oanh NT Milly G Williams M Demkine V Fowler D 《Science (New York, N.Y.)》2012,335(6065):183-189
Tropospheric ozone and black carbon (BC) contribute to both degraded air quality and global warming. We considered ~400 emission control measures to reduce these pollutants by using current technology and experience. We identified 14 measures targeting methane and BC emissions that reduce projected global mean warming ~0.5°C by 2050. This strategy avoids 0.7 to 4.7 million annual premature deaths from outdoor air pollution and increases annual crop yields by 30 to 135 million metric tons due to ozone reductions in 2030 and beyond. Benefits of methane emissions reductions are valued at $700 to $5000 per metric ton, which is well above typical marginal abatement costs (less than $250). The selected controls target different sources and influence climate on shorter time scales than those of carbon dioxide-reduction measures. Implementing both substantially reduces the risks of crossing the 2°C threshold. 相似文献
150.