全文获取类型
收费全文 | 462篇 |
免费 | 78篇 |
国内免费 | 32篇 |
专业分类
航空 | 183篇 |
航天技术 | 153篇 |
综合类 | 5篇 |
航天 | 231篇 |
出版年
2025年 | 2篇 |
2024年 | 7篇 |
2023年 | 13篇 |
2022年 | 27篇 |
2021年 | 31篇 |
2020年 | 19篇 |
2019年 | 9篇 |
2018年 | 13篇 |
2017年 | 6篇 |
2016年 | 9篇 |
2015年 | 17篇 |
2014年 | 22篇 |
2013年 | 23篇 |
2012年 | 20篇 |
2011年 | 34篇 |
2010年 | 20篇 |
2009年 | 34篇 |
2008年 | 17篇 |
2007年 | 25篇 |
2006年 | 33篇 |
2005年 | 23篇 |
2004年 | 27篇 |
2003年 | 24篇 |
2002年 | 12篇 |
2001年 | 18篇 |
2000年 | 12篇 |
1999年 | 17篇 |
1998年 | 12篇 |
1997年 | 12篇 |
1996年 | 10篇 |
1995年 | 9篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有572条查询结果,搜索用时 0 毫秒
471.
陈昌明 《中国民航飞行学院学报》2011,22(3):50-53
高校后勤社会化改革推行10年以来,目前中小城市高校后勤改革由于位处地理环境的客观条件,面临的社会市场有限,大部分中小城市高校后勤社会化改革在管理体制和运行机制上有待实现突破。本文以位处中小城市的中国民航飞行学院后勤改革实践为例,介绍其改革现状,研究其存在的问题,并提出了今后后勤改革的对策和建议,探索为其他中小城市高校后勤改革提供一种可以借鉴参考的模式。 相似文献
472.
分析了飞行包线向低速大迎角扩展后飞行品质研究面临的几个重要方面,即需要提供直到充分过失速迎角的飞行品质指标,这是设计飞控系统的依据之一:纵,横,航向操纵效能要求,这是配置,裁减操纵面的依据,机动任务集,这对于提出品质指标与操纵效能要求,及早发现飞机缺陷和全面评价飞机系统的战术效能等工作都有重要意义,总结有关的研究思路以及目前的进展,并给出了一些初步结论。 相似文献
473.
Kwangwon Lee Chandeok Park Sang-Young Park Daniel J. Scheeres 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
This study presents a semi-analytic approach for optimal tracking and formation keeping with high precision. For a continuous-thrust propulsion system, optimal formation keeping problems near a general Keplerian orbit are formulated with respect to a reference trajectory which is an explicit function of time. A nonlinear optimal tracking control law is then derived in generic form as a function of the states by employing generating functions in the theory of Hamiltonian systems. The applicability of the overall process is not affected by the complexity of dynamics and the selection of coordinates. As it allows us to design a nonlinear optimal feedback controller in the Earth-centered inertial frame, a variety of nonlinear perturbations can be incorporated easily without complicated coordinate transformations. Numerical experiments demonstrate that the nonlinear tracking control logic achieves superior tracking accuracy and cost reduction by accommodating higher-order nonlinearities. 相似文献
474.
Jae-Ik Park Han-Earl ParkSang-Young Park Kyu-Hong Choi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
A relative navigation and formation control algorithm for satellite formation flying was developed, and a hardware-in-the-loop (HIL) simulation testbed was established and configured to evaluate this algorithm. The algorithm presented is a relative navigation estimation algorithm using double-difference carrier-phase and single-difference code measurements based on the extended Kalman filter (EKF). In addition, a state-dependent Riccati equation (SDRE) technique is utilized as a nonlinear controller for the formation control problem. The state-dependent coefficient (SDC) form is formulated to include nonlinearities in the relative dynamics. To evaluate the relative navigation and control algorithms developed, a closed-loop HIL testbed is configured. To demonstrate the performance of the testbed, a test formation flying scenario comprising formation acquisition and keeping in a low earth orbit (LEO) has been established. The relative navigation results from the closed-loop simulations show that a 3D RMS of 0.07 m can be achieved for position accuracy. The targeted leader–follower formation flying in the along-track separation of 100 m was maintained with a mean position error of approximately 0.2 m and a standard deviation of 0.9 m. The simulation results show that the HIL testbed is capable of successful demonstration of the GPS-based satellite autonomous formation flying mission. 相似文献
475.
相对轨道自主确定方法的改进 总被引:3,自引:1,他引:3
编队飞行卫星相对轨道的确定具有重要意义。本文提出一种完全自主的定轨方案,在利用星间测量信息实现编队飞行卫星自主定轨的基础上,引入太阳敏感器测量信息,利用扩展卡尔曼滤波算法提高环绕星相对轨道确定精度。仿真结果验证了这种导航方案和算法的有效性。 相似文献
476.
F.J.T. Salazar J.J. Masdemont G. Gómez E.E. Macau O.C. Winter 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Assume a constellation of satellites is flying near a given nominal trajectory around L4 or L5 in the Earth–Moon system in such a way that there is some freedom in the selection of the geometry of the constellation. We are interested in avoiding large variations of the mutual distances between spacecraft. In this case, the existence of regions of zero and minimum relative radial acceleration with respect to the nominal trajectory will prevent from the expansion or contraction of the constellation. In the other case, the existence of regions of maximum relative radial acceleration with respect to the nominal trajectory will produce a larger expansion and contraction of the constellation. The goal of this paper is to study these regions in the scenario of the Circular Restricted Three Body Problem by means of a linearization of the equations of motion relative to the periodic orbits around L4 or L5. This study corresponds to a preliminar planar formation flight dynamics about triangular libration points in the Earth–Moon system. Additionally, the cost estimate to maintain the constellation in the regions of zero and minimum relative radial acceleration or keeping a rigid configuration is computed with the use of the residual acceleration concept. At the end, the results are compared with the dynamical behavior of the deviation of the constellation from a periodic orbit. 相似文献
477.
S. R. Habbal 《Space Science Reviews》1994,70(1-2):37-46
The observational characteristics of the small scale magnetic structures are summarized. The temperature structure and temporal variability of the emission from coronal bright points, that pervade the source region of the solar wind in coronal holes and the quiet sun, and from active regions are shown to be remarkably similar. Particular emphasis is given to observations, potentially feasible with SOHO, that could resolve some of the outstanding issues regarding the role of the small scale magnetic structures in the energy balance and properties of the solar wind. 相似文献
478.
结合具体飞行体会,详细阐述了对库珀—哈珀驾驶员评定等级的理解,论述了当试飞员依照该等级进行飞行评价时确定PR值的原则、方法、注意事项和影响因素;就个别参数讨论了MIL—F—8785C中规定的飞行品质等级与PR值之间的一致性问题,给出了当两者不一致时的处理办法,最后简单论述了其在现代飞机设计中的重要性。 相似文献
479.
Qiang FENG Xingshuo HAI Bo SUN Yi REN Zili WANG Dezhen YANG Yaolong HU Ronggen FENG 《中国航空学报》2022,35(1):110-123
This paper develops a novel optimization method oriented to the resilience of multiple Unmanned Aerial Vehicle(multi-UAV) formations to achieve rapid and accurate reconfiguration under random attacks. First, a resilience metric is applied to reflect the effect and rapidity of multi-UAV formation resisting random attacks. Second, an optimization model based on a parameter optimization problem to maximize the system resilience is established. Third, an Adaptive Learning-based Pigeon-Inspired Optim... 相似文献
480.
导弹精度评估的非参数Bootstrap方法 总被引:1,自引:0,他引:1
基于目前导弹试验的实际状况,讨论了小子样情况下精度指标的置信区间估计的非参数Bootstrap方法。介绍了Bootstrap方法的基本概念,综合比较了非参数Bootstrap抽样和参数Bootstrap抽样的特点,对基于传统百分位法的改进区间估计方法进行了简要说明,包括迭代Bootstrap方法、Bootstrap-t方法及纠偏百分位方法;最后,通过大量仿真计算初步分析了各种非参数Bootstrap区间估计方法的性能和适用范围,并给出了若干建议。 相似文献