全文获取类型
收费全文 | 1321篇 |
免费 | 219篇 |
国内免费 | 195篇 |
专业分类
航空 | 797篇 |
航天技术 | 432篇 |
综合类 | 124篇 |
航天 | 382篇 |
出版年
2024年 | 5篇 |
2023年 | 18篇 |
2022年 | 51篇 |
2021年 | 48篇 |
2020年 | 69篇 |
2019年 | 62篇 |
2018年 | 80篇 |
2017年 | 77篇 |
2016年 | 78篇 |
2015年 | 79篇 |
2014年 | 70篇 |
2013年 | 68篇 |
2012年 | 108篇 |
2011年 | 113篇 |
2010年 | 78篇 |
2009年 | 73篇 |
2008年 | 73篇 |
2007年 | 82篇 |
2006年 | 81篇 |
2005年 | 60篇 |
2004年 | 44篇 |
2003年 | 42篇 |
2002年 | 31篇 |
2001年 | 33篇 |
2000年 | 46篇 |
1999年 | 24篇 |
1998年 | 24篇 |
1997年 | 23篇 |
1996年 | 16篇 |
1995年 | 18篇 |
1994年 | 10篇 |
1993年 | 13篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 12篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
排序方式: 共有1735条查询结果,搜索用时 997 毫秒
1.
《中国航空学报》2020,33(3):749-770
Angle of Attack (AOA) is a crucial parameter which directly affects the aerodynamic forces of an aircraft. The measurement of AOA is required to ensure a safe flight within its designed flight envelop. This paper intends to summarise a comprehensive survey on the measurement techniques and estimation methods for AOA, specifically in Unmanned Aerial Vehicle (UAV) applications. In the case of UAVs, weight constraint plays a major role as far as sensor suites are concerned. This results in selecting a suitable estimation method to extract AOA using the available data from the autopilot. The most feasible and widely employed AOA measurement technique is by using the Multi-Hole Probes (MHPs). The MHP measures the AOA regarding the pressure variations between the ports. Due to the importance of MHP in AOA measurement, the calibration methods for the MHP are also included in this paper. This paper discusses the AOA measurement using virtual AOA sensors, their importance and the operation. 相似文献
2.
《中国航空学报》2020,33(4):1192-1205
Over the last few decades, the research on the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals is not sufficient. To this end, two kinds of brush-labyrinth seals for the bristle pack element installed upstream of the labyrinth teeth named BSU and installed downstream of the labyrinth teeth called BSD were used to investigate the effect of bristle pack position on the rotordynamic characteristics of the brush-labyrinth seals. Using the numerical model combining the porous medium model and the whirling rotor method, the rotordynamic characteristics of the BSU and BSD at various operating conditions including four kinds of pressure ratios, five kinds of inlet preswirl speeds and four kinds of rotor spinning speeds were conducted. The obtained results show that the effects of operating conditions on rotordynamic coefficients for the different seal configurations are different. The direct stiffness, cross-coupled stiffness and direct damping of the BSU are lower than those of the BSD. The rotordynamic coefficients of the BSU are more insensitive to the operating conditions variation. From the perspective of the seal stability, the BSU is a better brush-labyrinth seal configuration at high pressure ratio, high positive preswirl or high rotor spinning speed conditions. While in the case of low pressure ratio, low positive preswirl or low rotor spinning speed conditions, the BSD is a better choice. 相似文献
3.
4.
5.
6.
对H5飞机经过了计算、论证、试飞,在此基础上提出了一种既安全又能充分发挥飞机飞行性能,同时又使动作程序化的调油方法--规划调油法。用这种调油就可以大大地减少飞行员操纵飞机进的注意力分散,更利于集中精力操纵飞机,以保证飞行的安全。 相似文献
7.
8.
9.
介绍了光敏元件与光传感器技术的发展及在国民经济和军事领域中的重要怍用;分析了国内外光电子产业的市场动态与发展趋势;论述了我国光电子产业面临的机遇和挑战。 相似文献
10.