全文获取类型
收费全文 | 1719篇 |
免费 | 208篇 |
国内免费 | 165篇 |
专业分类
航空 | 300篇 |
航天技术 | 899篇 |
综合类 | 22篇 |
航天 | 871篇 |
出版年
2023年 | 31篇 |
2022年 | 38篇 |
2021年 | 70篇 |
2020年 | 59篇 |
2019年 | 47篇 |
2018年 | 73篇 |
2017年 | 19篇 |
2016年 | 37篇 |
2015年 | 61篇 |
2014年 | 186篇 |
2013年 | 108篇 |
2012年 | 77篇 |
2011年 | 165篇 |
2010年 | 119篇 |
2009年 | 117篇 |
2008年 | 105篇 |
2007年 | 81篇 |
2006年 | 74篇 |
2005年 | 96篇 |
2004年 | 57篇 |
2003年 | 35篇 |
2002年 | 53篇 |
2001年 | 45篇 |
2000年 | 66篇 |
1999年 | 65篇 |
1998年 | 33篇 |
1997年 | 23篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 7篇 |
1993年 | 15篇 |
1992年 | 9篇 |
1991年 | 15篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 22篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1984年 | 2篇 |
排序方式: 共有2092条查询结果,搜索用时 343 毫秒
801.
空间科学实验地面支持系统平台 总被引:1,自引:0,他引:1
相对于其他空间任务, 空间科学实验具有用户分散、实验进程控制 (遥科学实验)要求实时或准实时、多种类型空间科学数据处理要求等特点. 针对空间科学实验的特点和对地面支持系统的要求, 结合实践八号卫星(SJ-8)、探测双星(TC-1, TC-2) 和神舟系列飞船(SZ) 的空间科学实验地面支持系统的任务完成情况, 以及未来空间科学实验任务的需求, 提出了地面支持系统平台的构架设想. 该系统平台支持空间科学实验的状态监视与控制, 支持遥科学实验, 能够支持空间科学实验数据标准产品的定制处理, 满足空间科学实验多任务的要求, 具有通用性和可扩展性. 相似文献
802.
803.
神舟七号微小卫星伴随飞行技术试验 总被引:2,自引:0,他引:2
神舟七号 (SZ-7) 载人航天任务中释放的一颗微小伴随卫星 (BX-1), 首次开展了卫星在轨释放、对飞船观测和对轨道舱接近及绕飞等技术试验. 该卫星首次进行了GaInP2/GaAs/Ge 中国产太阳电池阵、锂离子蓄电池、微型液氨推进模块、小型化姿态跟踪控制模块、双焦距一体化可见光相机及小型化USB 测控应答机等技术验证. 本文介绍了SZ-7 微小卫星的设计方案, 讨论了形成稳定伴随飞行的轨道设计等技术, 并根据卫星在轨运行情况对试验任务进行了评价. 相似文献
804.
805.
G. Souvatzoglou H. Mavromichalaki C. Sarlanis G. Mariatos A. Belov E. Eroshenko V. Yanke 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Within the last years, a real-time system to monitor high energy cosmic rays for space weather use has been operated at Athens cosmic ray station. Neutron monitors and satellite high resolution data in real time are used, making it possible to observe cosmic rays in dual energy range observations. In large solar energetic particle (SEP) events, ground level enhancement (GLE) can provide the earliest alert for the onset of the SEP event. This system watches for count rate increases recorded in real time by 23 neutron monitors, which triggers an alarm if a ground level enhancement (GLE) of cosmic ray intensity is detected. 相似文献
806.
807.
S.G. Pavlov E.K. Jessberger H.-W. Hübers S. Schröder I. Rauschenbach S. Florek J. Neumann H. Henkel S. Klinkner 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Jupiter’s icy moon Europa is one of most promising places in our Solar System where possible extraterrestrial life forms could exist either in the past or even presently. The Europa Lander mission, an exciting part of the international Europa Jupiter System Mission (EJSM/Laplace), considers in situ planetary exploration of the moon. The distance of Europa from the Earth and the Sun asks for autonomous analytical tools that maximize the scientific return at minimal resources, demanding new experimental concepts. We propose a novel instrument, based on the atomic spectroscopy of laser generated plasmas for the elemental analysis of Europa’s surface materials as far as it is in reach of the lander for example by a robotic arm or a mole, or just onboard the lander. The technique of laser-induced plasma spectrometry provides quantitative elemental analysis of all major and many trace elements. It is a fast technique, i.e. an analysis can be performed in a few seconds, which can be applied to many different types of material such as ice, dust or rocks and it does not require any sample preparation. The sensitivity is in the range of tens of ppm and high lateral resolution, down to 50 μm, is feasible. In addition, it provides the potential of depth profiling, up to 2 mm in rock material and up to a few cm in more transparent icy matrices. Key components of the instrument are presently developed in Germany for planetary in situ missions. This development program is accompanied by an in-depth methodical investigation of this technique under planetary environmental conditions. 相似文献
808.
Ch. Katsavrias P. Preka-Papadema X. Moussas Th. Apostolou A. Theodoropoulou Th. Papadima 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
The effects of the energetic phenomena of the Sun, flares and coronal mass ejections (CMEs) on the Earth’s ionosphere–magnetosphere, through the solar wind, are the sources of the geomagnetic disturbances and storms collectively known as Space Weather. The research on the influence of Space Weather on biological and physiological systems is open. In this work we study the Space Weather impact on Acute Coronary Syndromes (ACS) distinguishing between ST-segment elevation acute coronary syndromes (STE–ACS) and non-ST-segment elevation acute coronary syndromes (NSTE–ACS) cases. We compare detailed patient records from the 2nd Cardiologic Department of the General Hospital of Nicaea (Piraeus, Greece) with characteristics of geomagnetic storms (DST), solar wind speed and statistics of flares and CMEs which cover the entire solar cycle 23 (1997–2007). Our results indicate a relationship of ACS to helio-geomagnetic activity as the maximum of the ACS cases follows closely the maximum of the solar cycle. Furthermore, within very active periods, the ratio NSTE–ACS to STE–ACS, which is almost constant during periods of low to medium activity, changes favouring the NSTE–ACS. Most of the ACS cases exhibit a high degree of association with the recovery phase of the geomagnetic storms; a smaller, yet significant, part was found associated with periods of fast solar wind without a storm. 相似文献
809.
810.