全文获取类型
收费全文 | 11572篇 |
免费 | 9697篇 |
国内免费 | 1900篇 |
专业分类
航空 | 18893篇 |
航天技术 | 1347篇 |
综合类 | 420篇 |
航天 | 2509篇 |
出版年
2024年 | 119篇 |
2023年 | 275篇 |
2022年 | 461篇 |
2021年 | 520篇 |
2020年 | 598篇 |
2019年 | 1269篇 |
2018年 | 1429篇 |
2017年 | 1379篇 |
2016年 | 1376篇 |
2015年 | 1337篇 |
2014年 | 1153篇 |
2013年 | 1189篇 |
2012年 | 1184篇 |
2011年 | 1107篇 |
2010年 | 1140篇 |
2009年 | 1123篇 |
2008年 | 998篇 |
2007年 | 817篇 |
2006年 | 688篇 |
2005年 | 493篇 |
2004年 | 451篇 |
2003年 | 360篇 |
2002年 | 391篇 |
2001年 | 329篇 |
2000年 | 282篇 |
1999年 | 300篇 |
1998年 | 234篇 |
1997年 | 206篇 |
1996年 | 157篇 |
1995年 | 135篇 |
1994年 | 139篇 |
1993年 | 194篇 |
1992年 | 137篇 |
1991年 | 313篇 |
1990年 | 262篇 |
1989年 | 294篇 |
1988年 | 207篇 |
1987年 | 82篇 |
1986年 | 32篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1972年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 312 毫秒
21.
22.
The Ariane transfer vehicle (ATV), an Ariane 5 borne, unmanned propulsion vehicle, is designed to transport the logistics needed to resupply the International Space Station (ISS) and the man tended free flyer (MTFF) step 2 with pressurized and unpressurized cargo and to dispose the waste. The ATV is an expendable vehicle and is disposed of by a safe atmospheric burn up. In accordance with the AR5 schedule it should be operational in 1996 for missions toward ISS and beyond the year 2000 for MTFF 2 missions. The main constituents of the proposed ATV are the modified AR5 third stage L5, an upgraded VEB steering the launcher as well as the ATV and the P/L-adaptor providing mechanical and umbilical links to the payload. The mechanical part of the RVD-kit will be placed on the payload-module, the main RVD sensors are located on the adaptor and the needed computer intelligence will be integrated on the VEB. To minimize the development, and recurring costs, the ATV concept fully complies to the idea of maximum use of existing hardware and software, mainly from the AR5, Hermes and Columbus programs thus minimizing development and recurring costs. The ATV is compatible to ISS, MTFF and OMV and is able to transport logistic modules compatible with NSTS and U.S.-expendable launchers. 相似文献
23.
24.
25.
26.
The primary objective of the Laser Interferometer Space Antenna (LISA) mission is to detect and observe gravitational waves from massive black holes and galactic binaries in the frequency range 10−4 to 10−1 Hz. This low-frequency range is inaccessible to ground-based interferometers because of the unshieldable background of local gravitational noise and because ground-based interferometers are limited in length to a few km. LISA is an ESA cornerstone mission and recently had a system study (Ref. 1) carried out by a consortium led by Astrium, which confirmed the basic configuration for the payload with only minor changes, and provided detailed concepts for the spacecraft and mission design. The study confirmed the need for a drag-free technology demonstration mission to develop the inertial sensors for LISA, before embarking on the build of the flight sensors. With a technology demonstration flight in 2005, it would be possible to carry out LISA as a joint ESA-NASA mission with a launch by 2010 subject to the funding programmatics. The baseline for LISA is three disc-like spacecraft each of which consist of a science module which carries the laser interferometer payload (two in each science module) and a propulsion module containing an ion drive and the hydrazine thrusters of the AOCS. The propulsion module is used for the transfer from earth escape trajectory provided by the Delta II launch to the operational orbit. Once there the propulsion module is jettisoned to reduce disturbances on the payload. Detailed analysis of thermal and gravitational disturbances, a model of the drag-free control and of the interferometer operation confirm that the strain sensitivity of the interferometer will be achieved. 相似文献
27.
28.
29.
30.