全文获取类型
收费全文 | 295篇 |
免费 | 17篇 |
国内免费 | 11篇 |
专业分类
航空 | 112篇 |
航天技术 | 43篇 |
综合类 | 13篇 |
航天 | 155篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 2篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 4篇 |
2016年 | 4篇 |
2015年 | 1篇 |
2014年 | 5篇 |
2013年 | 1篇 |
2012年 | 9篇 |
2011年 | 10篇 |
2010年 | 4篇 |
2009年 | 2篇 |
2008年 | 10篇 |
2007年 | 8篇 |
2006年 | 11篇 |
2005年 | 13篇 |
2004年 | 2篇 |
2003年 | 6篇 |
2002年 | 7篇 |
2001年 | 7篇 |
2000年 | 8篇 |
1999年 | 1篇 |
1998年 | 13篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 27篇 |
1994年 | 13篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 13篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有323条查询结果,搜索用时 15 毫秒
271.
Recent progresses in 2018-2019 from space experiments onboard SJ-10 recoverable satellite and on parabolic flight were summarized, mainly focusing on cell mechano-biological coupling under microgravity. In the meantime, technical pre-research and experimental system design for the biomechanics research platform on China Space Station was carried out and updated. 相似文献
272.
作为恐怖袭击的后果之一,美国的民航业几乎财政瘫 痪。虽然联邦政府的一揽子援助措施会对其有所帮助,但至少有一或两家骨干航空公司可能破产。 不少于五家的航空公司被列入了“最危险(航空公司)”的名单,它们是AirTran航空公司、美国西部航空公司、大陆航空公司、西北航空公司和合众国航空公司。这是依据它们的现金储备以及贷款能力来估算的。 其他因素还有赖于联邦政府援助华盛顿计划所批准的(资金)数量以及什么时候才可供使用,在未来的几周之内,会出现一个航空公司破产的高潮。另外一方面,那些占美国整个航空运输运力8… 相似文献
273.
274.
275.
276.
277.
遥操作机器人神经网络Smith预估控制(英文) 总被引:4,自引:0,他引:4
针对遥操作机器人通讯通道中存在的时延 ,提出了一种神经网络 Smith预估控制方法。控制系统适合于时延不变但未知的情况。控制系统包括主控制器和从系统两部分。从系统采用动态神经网络辨识机器人的动态模型 ,神经网络权重在线学习 ,用神经网络的输出对非线性系统进行局部非线性补偿 ,将非线性系统线性化。主系统针对线性化的从系统 ,采用 Smith预估控制解决时延问题并保证系统的性能品质。通过李雅普诺夫稳定理论保证了时延控制系统的稳定性。对两关节机器人的仿真结果说明了该方法的有效性。 相似文献
278.
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
279.
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
280.
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