全文获取类型
收费全文 | 146篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
航空 | 28篇 |
航天技术 | 102篇 |
综合类 | 1篇 |
航天 | 39篇 |
出版年
2023年 | 5篇 |
2022年 | 5篇 |
2021年 | 5篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 5篇 |
2017年 | 4篇 |
2015年 | 4篇 |
2014年 | 11篇 |
2013年 | 15篇 |
2012年 | 13篇 |
2011年 | 16篇 |
2010年 | 9篇 |
2009年 | 11篇 |
2008年 | 8篇 |
2007年 | 6篇 |
2006年 | 4篇 |
2005年 | 11篇 |
2004年 | 1篇 |
2003年 | 1篇 |
2002年 | 3篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1995年 | 1篇 |
排序方式: 共有170条查询结果,搜索用时 31 毫秒
21.
22.
23.
Kashyapa Naren Athreyas Erry Gunawan Tay Bee Kiat 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(11):3436-3451
Gravity waves are recognized as an integral part of earth’s atmosphere which are mainly responsible for energy and momentum distribution among different layers and regions in the atmosphere. Various sources present in land, ocean, and atmosphere such as mountains, convection, jets and fronts etc. are responsible for gravity waves generation. Thunderstorms (deep convection) are one of the major sources of gravity waves in the tropical region, capable of generating waves with a wide range of frequencies and scales and significantly affecting the existing waves. Previous numerical studies have characterised the wave properties that are generated from thunderstorms, but there are no statistically quantified studies. In this paper, we have modelled the relationship between the latent heat generated inside a thunderstorm and the gravity wave properties at the geo-collocated points. Gravity waves are identified over Singapore radiosonde station (with data available until 30?km altitude with 12?h temporal resolution) in the stratosphere using wavelet studies. Based on the GROGRAT ray tracing methods to identify the thunderstorm locations, and RAMS cloud-resolving models simulations to obtain the latent heating of the thunderstorm, a regression analysis is performed using 200 cases of gravity waves. Furthermore, cloud-top momentum flux analysis is performed for various cases latent heat. This study is expected to provide more quantified and concrete information on the coupling between the thunderstorm and gravity wave which includes the variance in these relationships due to wave frequency spectrum and generation mechanisms. 相似文献
24.
高精度星间微波测距技术 总被引:5,自引:0,他引:5
卫卫跟踪(SST)技术是目前地球重力场测量最有价值和应用前景的方法之一。高精度K波段星间微波测距系统(KBR K Band Ranging System)低低卫卫跟踪(SST-Ⅱ)重力卫星的关键有效载荷,它是一微米量级的测距系统,通过处理高精度的星间距离和距离变化率数据,可以恢复出地球重力场。在研究星间双路微波测距原理的基础上,提出了一种KBR系统的基本结构,详细描述了数据处理过程和KBR系统研究需要突破的关键技术,分析了国内目前的研究水平,给出了我国未来开展KBR系统研究的一些建议。 相似文献
25.
借力飞行是减小星际探测任务发射能量和总的速度增量的有效途径,然而,借力飞行前后,探测器速度矢量转角的变化往往受到借力星体体积、质量等因素的影响,而不能达到理想的要求。若在借力飞行中引入气动辅助变轨,即气动-引力辅助转移(AGA),则这一问题可以得到有效解决。现通过对AGA转移轨道的分析,给出了AGA转移轨道设计的拼接条件,此拼接条件是对AGA转移轨道进行设计和分析的重要准则。同时还以探测Ivar小行星为例,提出了一种将绘制等高线图和圆锥曲线拼接相结合的设计AGA转移轨道的方法,并给出了设计探测Ivar小行星转移轨道的参数。数值计算表明:AGA转移方法不但可以降低远程星际探测任务的发射能量和总的速度增量,而且可以找到更多的探测机会。 相似文献
26.
27.
基于重力梯度杆和磁铁的小卫星三轴姿态控制 总被引:2,自引:0,他引:2
运用卫星低轨道两个主要环境力矩(重力梯度矩和地磁力矩)对圆轨道卫星三轴姿态进行被动控制。利用重力梯度矩实现卫星对地指向:卫星上的永久磁铁获取所需的地磁力矩,稳定偏航姿态。给出卫星的姿态分析,并给出仿真结果。从分析和仿真结果可以看出,此卫星具有结构简单、时刻对地定向、低轨道倾角时卫星姿态稳定精度较高的优点。 相似文献
28.
29.
L. Prange A. Jäggi R. Dach H. Bock G. Beutler L. Mervart 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
The gravity field model AIUB-CHAMP02S, which is based on six years of CHAMP GPS data, is presented here. The gravity field parameters were derived using a two step procedure: In a first step a kinematic trajectory of a low Earth orbiting (LEO) satellite is computed using the GPS data from the on-board receiver. In this step the orbits and clock corrections of the GPS satellites as well as the Earth rotation parameters (ERPs) are introduced as known. In the second step this kinematic orbit is represented by a gravitational force model and orbit parameters. 相似文献
30.
M.N. Kouahla G. Moreels M. Faivre J. Clairemidi J.W. Meriwether G.A. Lehmacher E. Vidal O. Veliz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
A new and original stereo imaging method is introduced to measure the altitude of the OH nightglow layer and provide a 3D perspective map of the altitude of the layer centroid. Near-IR photographs of the OH layer are taken at two sites separated by a 645 km distance. Each photograph is processed in order to provide a satellite view of the layer. When superposed, the two views present a common diamond-shaped area. Pairs of matched points that correspond to a physical emissive point in the common area are identified in calculating a normalized cross-correlation coefficient (NCC). This method is suitable for obtaining 3D representations in the case of low-contrast objects. An observational campaign was conducted in July 2006 in Peru. The images were taken simultaneously at Cerro Cosmos (12°09′08.2″ S, 75°33′49.3″ W, altitude 4630 m) close to Huancayo and Cerro Verde Tellolo (16°33′17.6″ S, 71°39′59.4″ W, altitude 2272 m) close to Arequipa. 3D maps of the layer surface were retrieved and compared with pseudo-relief intensity maps of the same region. The mean altitude of the emission barycenter is located at 86.3 km on July 26. Comparable relief wavy features appear in the 3D and intensity maps. It is shown that the vertical amplitude of the wave system varies as exp (Δz/2H) within the altitude range Δz = 83.5–88.0 km, H being the scale height. The oscillatory kinetic energy at the altitude of the OH layer is comprised between 3 × 10−4 and 5.4 × 10−4 J/m3, which is 2–3 times smaller than the values derived from partial radio wave at 52°N latitude. 相似文献