全文获取类型
收费全文 | 579篇 |
免费 | 78篇 |
国内免费 | 97篇 |
专业分类
航空 | 545篇 |
航天技术 | 65篇 |
综合类 | 64篇 |
航天 | 80篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 34篇 |
2021年 | 31篇 |
2020年 | 36篇 |
2019年 | 35篇 |
2018年 | 37篇 |
2017年 | 44篇 |
2016年 | 41篇 |
2015年 | 29篇 |
2014年 | 45篇 |
2013年 | 31篇 |
2012年 | 40篇 |
2011年 | 38篇 |
2010年 | 24篇 |
2009年 | 37篇 |
2008年 | 31篇 |
2007年 | 34篇 |
2006年 | 24篇 |
2005年 | 24篇 |
2004年 | 17篇 |
2003年 | 18篇 |
2002年 | 13篇 |
2001年 | 9篇 |
2000年 | 11篇 |
1999年 | 10篇 |
1998年 | 11篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1990年 | 3篇 |
1989年 | 3篇 |
1988年 | 1篇 |
排序方式: 共有754条查询结果,搜索用时 15 毫秒
751.
Xingxing JIANG Qiang HUANG Changqing SHEN Qian WANG Kun XU Jie LIU Juanjuan SHI Zhongkui ZHU 《中国航空学报》2022,35(1):348-364
As critical components in modern aerospace productions, rolling element bearings(REBs) generally work under varying speed conditions, which brings great challenges to their operating health monitoring. Some novel time–frequency decomposition(TFD) algorithms are established recently to extract nonlinear features from the non-stationary signals effectively, which are promising for realizing fault diagnosis of REBs under varying speed conditions. However, numerous personal experiences must be incor... 相似文献
752.
753.
《中国航空学报》2022,35(11):235-251
This paper explores an analytical model for Elastic Ring Squeeze Film Damper (ERSFD) with thin-walled ring and turbulent-jet orifices, and uncovers its Oil Film Pressure Performance (OFPP). Firstly, the ring deformation is addressed by using the Fourier series expansion approach and the orifice outflow rate is characterized with the Prandtl boundary layer theory. Secondly, applying finite difference scheme, the influence of elastic ring flexibility, orifice diameter, and attitude angle on the OFPP is analyzed. Finally, Outer chamber pressure was measured experimentally at different rotor speeds. The results indicate that the outer chamber pressure coats an individual load-carrying region and spreads symmetrically pertaining to the attitude angle. Its amplitude drops as the elastic ring flexibility decreases but boosts with the reduction of the orifice diameter. For inner chamber pressure, the orifice diameter effects a similar trend to the outer cavity, but exhibits more stable distribution regarding the attitude angle. Minimizing the elastic ring flexibility causes an increase in amplitude. The model is validated by the test results giving that the outer chamber pressure shifts synchronously and periodically with the variation of the attitude angle, while the pressure amplitude increases slightly at higher rotor speeds. 相似文献
754.
Tapered ring with thin wall and three high ribs(TRTWTHR), showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm), is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin, rocket body and fuel tank because of light weight and high carrying capacity. How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve. In this work, constraining ring rolling(CRR) techn... 相似文献