全文获取类型
收费全文 | 814篇 |
免费 | 32篇 |
国内免费 | 12篇 |
专业分类
航空 | 387篇 |
航天技术 | 165篇 |
综合类 | 48篇 |
航天 | 258篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 9篇 |
2021年 | 3篇 |
2020年 | 4篇 |
2019年 | 6篇 |
2018年 | 15篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 3篇 |
2014年 | 38篇 |
2013年 | 10篇 |
2012年 | 26篇 |
2011年 | 29篇 |
2010年 | 26篇 |
2009年 | 18篇 |
2008年 | 40篇 |
2007年 | 43篇 |
2006年 | 35篇 |
2005年 | 37篇 |
2004年 | 23篇 |
2003年 | 23篇 |
2002年 | 25篇 |
2001年 | 30篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 30篇 |
1997年 | 27篇 |
1996年 | 26篇 |
1995年 | 48篇 |
1994年 | 43篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 14篇 |
1987年 | 16篇 |
1986年 | 10篇 |
1985年 | 15篇 |
1984年 | 17篇 |
1983年 | 19篇 |
1982年 | 31篇 |
1981年 | 19篇 |
1980年 | 21篇 |
1979年 | 5篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1975年 | 2篇 |
排序方式: 共有858条查询结果,搜索用时 265 毫秒
741.
<正>6月6日至8日,为期三天的2014上海浪琴环球马术冠军赛在上海中华艺术宫举行。总价值上亿欧元的60匹名马是如何从欧洲空运至上海的?这其中又攻克了哪些重重障碍呢?一.有史以来中国大陆举办的级别最高的马术赛事6月6日至8日,为期三天的2014上海浪琴环球马术冠军赛在上海中华艺术宫举行。该赛事是国际马术联合会管理下的最高五星级别马术障碍赛事,是中国大陆有史以来举办的级别最高、国际影响力最大、观赏性最强的马术赛事,26万多人次观众现场观看了比赛,1.3亿全球观众通过电视转播收 相似文献
742.
743.
2005年,民用航空维修市场的总值达到388亿美元. 根据TeamSAI和BACK航空解决方案的预测,受劳动力成本触底反弹和发动机大修业务上升等因素的影响,未来5年全球民用航空维修市场的综合年度增长率(CAGR)为4.7%,到2011年民航维修市场总值达到488亿美元.之后的5年,即2012~2016年,全球民用航空维修市场的CAGR为4.4%,到2016年,总值将达到606亿美元. 相似文献
744.
Achieving accurate navigation information by integrating multiple sensors is key to the safe operation of land vehicles in global navigation satellite system(GNSS)-denied environment. However,current multi-sensor fusion methods are based on stovepipe architecture,which is optimized with custom fusion strategy for specific sensors. Seeking to develop adaptable navigation that allows rapid integration of any combination of sensors to obtain robust and high-precision navigation solutions in GNSS-denied environment,we propose a generic plug-and-play fusion strategy to estimate land vehicle states. The proposed strategy can handle different sensors in a plug-and-play manner as sensors are abstracted and represented by generic models,which allows rapid reconfiguration whenever a sensor signal is additional or lost during operation. Relative estimations are fused with absolute sensors based on improved factor graph,which includes sensors' error parameters in the non-linear optimization process to conduct sensor online calibration. We evaluate the performance of our approach using a land vehicle equipped with a global positioning system(GPS) receiver as well as inertial measurement unit(IMU),camera,wireless sensor and odometer. GPS is not integrated into the system but treated as ground truth. Results are compared with the most common filtering-based fusion algorithm. It shows that our strategy can process low-quality input sources in a plug-and-play and robust manner and its performance outperforms filtering-based method in GNSS-denied environment. 相似文献
745.
本文描述了用于大型单元数字化阵列雷达(EDAR)的多层自适应波束形成方法。各阵列单元的距离相关增益自适应(RDGA)提供了有效的杂波对消。机载截击(AI)雷达的模拟试验验证了这种方法的效率,并说明了它相对于阵列中随机相位误差和幅度误差的稳定性。 相似文献
746.
SEYEDABADI M E FALANGA M AZAM M BARESI N FL RON R JANTARACHOTE V JUAREZ ORTIZ V A JULCA YAYA J J LANGER M MANUTHASNA S MARTINOD N MUGHAL M R NOMAN M PARK J PIMNOO A PRAKS J REYNERI L SANNA A I MAN T SOME J ULAMBAYAR T YU Xiaozhou DONG Xiaolong BALDIS L 《空间科学学报》2020,40(4):443-461
As the role of missions and experiments carried out in outer space becomes more and more essential in our understanding of many earthly problems, such as resource management, environmental problems, and disaster management, as well as space science questions, thanks to their lower cost and faster development process CubeSats can benefit humanity and therefore, young scientists and engineers have been motivated to research and develop new CubeSat missions. Not very long after their inception, CubeSats have evolved to become accepted platforms for scientific and commercial applications. The last couple of years showed that they are a feasible tool for conducting scientific experiments, not only in the Earth orbit but also in the interplanetary space. For many countries, a CubeSat mission could prompt the community and young teams around the world to build the national capacity to launch and operate national space missions. This paper presents an overview of the key scientific and engineering gateways opened up to the younger scientific community by the advent and adaptation of new technology into CubeSat missions. The role of cooperation and the opportunities for capacity-building and education are also explored. Thus, the present article also aims to provide useful recommendations to scientists, early-career researchers, engineers, students, and anyone who intends to explore the potential and opportunities offered by CubeSats and CubeSats-based missions. 相似文献
747.
With the approaching of the Chinese Space Station (CSS) era, the focus of space medicine applications and related research has shifted to addressing the astronauts' health support in long-duration spaceflights, including nutrition, countermeasure against the physiological effects of weightlessness, medical monitoring and support, psychology status, etc., and accordingly the human experiments to simulate long-duration weightlessness have been carried out. Increasingly, basic research has been put forward in the key areas, such as space bone loss, cardiovascular dysfunction and the molecular mechanisms underlying radiobiological effects. Moreover, specific novel research fields, such as hypometabolism technology, were explored. The research projects in the field of space medicine experiment, as an important aspect of the Chinese Space Station's application, have been officially approved and launched. 相似文献
748.
749.
维修成本是航空公司运营成本的一部分。迫于经济压力,航空公司和维修企业采取了多种措施,降低不必要的维修开支,以达到节省成本、增加收益的目的。 相似文献
750.
本文描述了计算机正确实现 MIL—STD—1750A 结构规范的理由和重要性。文中叙述了简要的检验史。描述了现有的测试方法,包括测试过程,结果分析及试验报告。最后讨论了将来的检验测试方法。 STD—1553数据总线。多指令系统结构的扩增问题导致多硬件和软件系统,从而导致软件费用高使用 MIL—STD—1750A ISA,我们可以降低软件成本。缩短软件研制时间,并促使工业使用新技术,使用ATP 作为检验测试工具,确保结构与 MIL—STD—1750A的兼容性,使上述优点成为可能。当检验过程在1983年第3季度使用时。将通过使用 VSW 使之增强。刘茴译刘花校 相似文献