全文获取类型
收费全文 | 1044篇 |
免费 | 147篇 |
国内免费 | 278篇 |
专业分类
航空 | 694篇 |
航天技术 | 326篇 |
综合类 | 179篇 |
航天 | 270篇 |
出版年
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 15篇 |
2020年 | 24篇 |
2019年 | 11篇 |
2018年 | 16篇 |
2017年 | 13篇 |
2016年 | 19篇 |
2015年 | 38篇 |
2014年 | 57篇 |
2013年 | 68篇 |
2012年 | 55篇 |
2011年 | 64篇 |
2010年 | 75篇 |
2009年 | 86篇 |
2008年 | 82篇 |
2007年 | 64篇 |
2006年 | 56篇 |
2005年 | 41篇 |
2004年 | 24篇 |
2003年 | 31篇 |
2002年 | 25篇 |
2001年 | 37篇 |
2000年 | 54篇 |
1999年 | 58篇 |
1998年 | 72篇 |
1997年 | 47篇 |
1996年 | 58篇 |
1995年 | 33篇 |
1994年 | 37篇 |
1993年 | 38篇 |
1992年 | 34篇 |
1991年 | 37篇 |
1990年 | 24篇 |
1989年 | 19篇 |
1988年 | 17篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有1469条查询结果,搜索用时 15 毫秒
2.
人才是实现民族振兴、赢得国际竞争优势的战略资源,雄安新区建设发展离不开人才的重要支撑。本文以雄安新区人才队伍建设为研究对象,剖析这一研究的意义和现状,探究雄安新区人才队伍建设存在的问题,最后提出解决这一问题的建议。 相似文献
3.
X.B. Zhao W.Z. Shao L.B. Zhao Y. Gao Y.Y. Hu X.Z. Yuan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(10):3072-3086
The main objective of our work was to investigate the impact of rain on wave observations from C-band (~5.3 GHz) synthetic aperture radar (SAR) in tropical cyclones. In this study, 10 Sentinel-1 SAR images were available from the Satellite Hurricane Observation Campaign, which were taken under cyclonic conditions during the 2016 hurricane season. The third-generation wave model, known as Simulating WAves Nearshore (SWAN) (version 41.31), was used to simulate the wave fields corresponding to these Sentinel-1 SAR images. In addition, rainfall data from the Tropical Rainfall Measuring Mission satellite passing over the spatial coverage of the Sentinel-1 SAR images were collected. The simulated results were validated against significant wave heights (SWHs) from the Jason-2 altimeter and European Centre for Medium-Range Weather Forecasts data, revealing a root mean square error (RMSE) of ~0.5 m with a 0.25 scatter index. Winds retrieved from the VH-polarized Sentinel-1 SAR images using the Sentinel-1 Extra Wide-swath Mode Wind Speed Retrieval Model after Noise Removal were taken as prior information for wave retrieval. It was discovered that rain did indeed affect the SAR wave retrieval, as evidenced by the 3.21-m RMSE of SWHs between the SAR images and the SWAN model, which was obtained for the ~1000 match-ups with raindrops. The raindrops dampened the wave retrieval when the rain rate was < ~5 mm/hr; however, they enhanced wave retrieval for higher rain rates. It was also found that the portion of the rain-induced ring wave with a wave number > 0.05 rad/m (~125 m wavelength) was clearly observed in the SAR-derived wave spectra. 相似文献
6.
8.
10.