全文获取类型
收费全文 | 2105篇 |
免费 | 419篇 |
国内免费 | 383篇 |
专业分类
航空 | 1357篇 |
航天技术 | 453篇 |
综合类 | 358篇 |
航天 | 739篇 |
出版年
2024年 | 5篇 |
2023年 | 23篇 |
2022年 | 61篇 |
2021年 | 70篇 |
2020年 | 76篇 |
2019年 | 49篇 |
2018年 | 75篇 |
2017年 | 51篇 |
2016年 | 46篇 |
2015年 | 93篇 |
2014年 | 125篇 |
2013年 | 115篇 |
2012年 | 132篇 |
2011年 | 137篇 |
2010年 | 160篇 |
2009年 | 137篇 |
2008年 | 147篇 |
2007年 | 148篇 |
2006年 | 118篇 |
2005年 | 121篇 |
2004年 | 91篇 |
2003年 | 112篇 |
2002年 | 122篇 |
2001年 | 102篇 |
2000年 | 70篇 |
1999年 | 86篇 |
1998年 | 66篇 |
1997年 | 38篇 |
1996年 | 42篇 |
1995年 | 32篇 |
1994年 | 46篇 |
1993年 | 28篇 |
1992年 | 33篇 |
1991年 | 31篇 |
1990年 | 29篇 |
1989年 | 33篇 |
1988年 | 21篇 |
1987年 | 19篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 2篇 |
排序方式: 共有2907条查询结果,搜索用时 31 毫秒
1.
Yu Jiang Hexi Baoyin Hengnian Li 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(5):1371-1385
We investigate the orbital stability close to the unique L4-point Jupiter binary Trojan asteroid 624 Hektor. The gravitational potential of 624 Hektor is calculated using the polyhedron model with observational data of 2038 faces and 1021 vertexes. Previous studies have presented three different density values for 624 Hektor. The equilibrium points in the gravitational potential of 624 Hektor with different density values have been studied in detail. There are five equilibrium points in the gravitational potential of 624 Hektor no matter the density value. The positions, Jacobian, eigenvalues, topological cases, stability, as well as the Hessian matrix of the equilibrium points are investigated. For the three different density values the number, topological cases, and the stability of the equilibrium points with different density values are the same. However, the positions of the equilibrium points vary with the density value of the asteroid 624 Hektor. The outer equilibrium points move away from the asteroid’s mass center when the density increases, and the inner equilibrium point moves close to the asteroid’s mass center when the density increases. There exist unstable periodic orbits near the surface of 624 Hektor. We calculated an orbit near the primary’s equatorial plane of this binary Trojan asteroid; the results indicate that the orbit remains stable after 28.8375?d. 相似文献
2.
3.
4.
Performance evaluation for MAP state estimate fusion 总被引:1,自引:0,他引:1
Chang K.C. Zhi Tian Mori S. 《IEEE transactions on aerospace and electronic systems》2004,40(2):706-714
This paper presents a quantitative performance evaluation method for the maximum a posteriori (MAP) state estimate fusion algorithm. Under ideal conditions where data association is assumed to be perfect, it has been shown that the MAP or best linear unbiased estimate (BLUE) fusion formula provides the best linear minimum mean squared estimate (LMMSE) given local estimates under the linear Gaussian assumption for a static system. However, for a dynamic system where fusion is recursively performed by the fusion center on local estimates generated from local measurements, it is not obvious how the MAP algorithm will perform. In the past, several performance evaluation methods have been proposed for various fusion algorithms, including simple convex combination, cross-covariance combination, information matrix, and MAP fusion. However, not much has been done to quantify the steady state behavior of these fusion methods for a dynamic system. The goal of this work is to present analytical fusion performance results for MAP state estimate fusion without extensive Monte Carlo simulations, using an approach developed for steady state performance evaluation for track fusion. Two different communication strategies are considered: fusion with and without feedback to the sensors. Analytic curves for the steady state performance of the fusion algorithm for various communication patterns are presented under different operating conditions. 相似文献
5.
Changlong Jiang Jianping Xiong Xugang Zhang Huibo Jia Duanyi Xu 《Aerospace and Electronic Systems Magazine, IEEE》2003,18(11):31-34
Most sustained data recording systems in many real-time fields are based on tape equipments. We have developed an innovative sustained data recording system based on disk array which consists of Array Controller Module (ACM), String Controller Module (SCM) and Main Controller Module (MCM). This system has a better performance and higher reliability than the traditional tape recorder and can be used conveniently in many areas of data recording, storing, playback, and remote backup. This novel recording system has been used in radar data recorder for spacecraft orbit tracking and satellite remote sensing data recording successfully. 相似文献
6.
7.
介绍了一种在CAD/CAPP集成系统中工序图自动生成的较通用的方法,提出了两种不同实现途径。并以实例表明在Pro/Engineer系统中得到了成功应用。 相似文献
8.
9.
10.
项目教学法在《微机系统实现与维护》课程教学中的应用探索 总被引:1,自引:0,他引:1
项目教学法突破传统的教学模式,在参与项目完成的过程中学生能更好、更快地掌握所学知识,学习的积极性和主动性大大提高。本文将项目教学法的学习模式引入到高职高专的《微机系统实现与维护》课程教学中,对如何把理论与实践有机地结合,如何提高学生的技能水平作了一定的探索。 相似文献