首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1560篇
  免费   392篇
  国内免费   474篇
航空   1153篇
航天技术   466篇
综合类   175篇
航天   632篇
  2024年   17篇
  2023年   51篇
  2022年   64篇
  2021年   74篇
  2020年   98篇
  2019年   101篇
  2018年   122篇
  2017年   90篇
  2016年   104篇
  2015年   120篇
  2014年   121篇
  2013年   86篇
  2012年   159篇
  2011年   166篇
  2010年   130篇
  2009年   114篇
  2008年   101篇
  2007年   105篇
  2006年   102篇
  2005年   57篇
  2004年   67篇
  2003年   46篇
  2002年   45篇
  2001年   46篇
  2000年   33篇
  1999年   22篇
  1998年   32篇
  1997年   27篇
  1996年   16篇
  1995年   18篇
  1994年   21篇
  1993年   11篇
  1992年   14篇
  1991年   6篇
  1990年   11篇
  1989年   13篇
  1988年   8篇
  1987年   3篇
  1986年   5篇
排序方式: 共有2426条查询结果,搜索用时 15 毫秒
991.
考虑量测噪声和地球曲率对配准的影响,提出了一种基于地心坐标系(ECEF)的扩展卡尔曼滤波(EKF)配准与目标艰踪算法.根据坐标系转换关系,给出误差配准计算公式,建立目标的动态方程,用EKF方程进行估计.仿真结果表明:该法能同时有效估计目标运动状态和传感器配准误差,可用于远距离的传感器配准和目标跟踪.  相似文献   
992.
魏丽娜 《飞机设计》2010,30(4):26-30
分析了真实飞机上惯性导航系统的基本原理,加速度计和陀螺仪工作原理及其测量输出参数。结合航空仿真技术发展和全任务飞行模拟器样机的任务需求,在MATLAB/SIMULINK平台上构建捷联惯性导航仿真模型;利用RT-LAB平台构建分布式飞行仿真系统,实现导航外部特性的半实物仿真;建立导航数据库,用于导航计算以确定飞机即时位置以及导航台自动调谐管理。将导航系统仿真模块作为整个系统仿真中的一个节点,实现与模拟机自动驾驶仪系统进行信息交互,从而实现自动导航。  相似文献   
993.
We present an integral-based approach for high-resolution regional recovery of the gravitational field in this article. We derive rigorous remove-compute-restore integral estimators relating the line-of-sight gravitational acceleration to an arbitrary order radial derivative of the gravitational potential. The integral estimators are composed of three terms, i.e., the truncated integration, the low-frequency line-of-sight gravitational acceleration, and the high-frequency truncation error (effect of the distant zones). We test the accuracy of the integral transformations and of the integral estimators in a closed-loop simulation over the Montes Jura region on the nearside of the Moon. In this way, we determine optimal sizes of integration radii and grid discretisation. In addition, we investigate the performance of the regional integral inversion with synthetic and realistic GRAIL observations. We demonstrate that the regional inversion results of the disturbing gravitational potential and its first order radial derivative in the Montes Jura mountain range are less contaminated by high-frequency noise than the global spherical harmonic models.  相似文献   
994.
由于飞机与尾流模型的非线性,为实现自动精确着舰,探究了具有尾流抑制能力的非线性控制器设计方法.基于气流扰动影响的飞机六自由度非线性模型,利用非线性动态逆控制方法对各控制回路进行了设计,为抑制尾流扰动,提出了应用非线性观测器进行补偿的方法.仿真结果表明,具有非线性干扰观测器的控制器可以在4s内使飞机稳定在速度为52.04 m/s,并使航迹角保持在±0.5°变化范围内,最终的着舰侧向偏差为-0.13m.  相似文献   
995.
CAKE (Cosmic Abundances below Knee Energies) was a prototype balloon experiment for the determination of the charge spectra and abundances of the primary cosmic rays (CR) with Z > 10. It was a passive instrument made of layers of CR39® and Lexan®/Makrofol® nuclear track detectors; it had a geometric acceptance of ∼0.7 m2 sr for Fe nuclei. Here, the scanning and analysis strategies, the algorithms used for the off-line filtering and for the tracking in automated mode of the primary cosmic rays are presented, together with the resulting CR charge distribution and their abundances.  相似文献   
996.
Track association of multi-target has been recognized as one of the key technologies in distributed multiple-sensor data fusion system,and its accuracy directly impacts on the performance of the whole tracking system.A multi-sensor data association is proposed based on aftinity propagation(AP)algorithm.The proposed method needs an initial similarity,a distance between any two points,as a parameter,therefore,the similarity matrix is calculated by track position,velocity and azimuth of track data.The approach can automatically obtain the optimal classification of uncertain target based on clustering validity index.Furthermore,the same kind of data are fused based on the variance of measured data and the fusion result can be taken as a new measured data of the target.Finally,the measured data are classified to a certain target based on the nearest neighbor ideas and its characteristics,then filtering and target tracking are conducted.The experimental results show that the proposed method can effectively achieve multi-sensor and multi-target track association.  相似文献   
997.
李夏苗  陈新江  伍国华  贺川  龙运军 《航空学报》2019,40(11):323233-323233
为提高中继卫星系统的应用效能及数传任务的完成率,在中继卫星调度中考虑了断点续传这一应用模式,即对单个数传任务进行合理拆分,使其在多个时间窗口内完成。首先构建面向断点续传的中继卫星单址天线的调度模型,然后提出一种基于冲突风险评估的冲突度量化方法,并设计考虑断点续传的两阶段调度算法。最后开展大量的仿真实验将该算法与贪婪算法、基于最小冲突度的启发式算法和基于任务优先级的启发式算法这3个不考虑断点续传的算法进行对比。实验结果表明,所提出的算法在任务完成率方面分别提高了7.67%、6.34%和8.67%。  相似文献   
998.
Rendezvous and docking (RVD) with a tumbling target is challenging. In this paper, a novel control scheme based on motion planning and pose (position and attitude) tracking is proposed to solve the pose control of a chaser docking with a tumbling target in the phase of close range rendezvous. Firstly, the current desired motion of the chaser is planned according to the motion of the target. In planning the desired motion, the “approach path constraint” is considered to avoid collisions between the chaser and the target, and the “field-of-view constraint” is considered to make sure the vision sensors on the chaser to obtain tight relative pose knowledge of the target with respect to the chaser. Then, the difference between the chaser’s motion and the desired motion is gradually reduced by a pose tracking controller. This controller is based on the non-singular terminal sliding mode (NTSM) method to make the tracking error converge to zero in finite time. Since the chaser nearly moves along the desired motion and the motion is reasonable, (1) it could safely arrive at the docking port of the target with a suitable relative attitude, (2) it will be always suitably oriented to observe the target well, and (3) the magnitude of the needed control inputs are less than that in existing literatures. The numerical results demonstrate the above three advantages of the proposed method.  相似文献   
999.
Space debris, such as defunct satellites and upper stages of rockets, becomes an uncooperative target after losing its attitude control and communication ability. In addition, tumbling motion can occur due to environmental perturbations and residual angular momentum prior to the object’s end-of-mission. To minimize the collision risk during docking and capturing of the tumbling target, a non-contact method based on the eddy current effect is put forward to transmit the control torque to the tumbling target. The main idea is to induce a controllable torque on the conducting surface of the tumbling target using a rotational magnetic field generated by a Halbach rotor. The radial and axial Halbach rotors are used to damp the spinning and nutation motions of the target, respectively. The normal and tangential force are evaluated concerning the relative pose between the chaser and the target. A simplified dynamic model of the nutation damping and despinning processes is developed and the influences of the asymmetrical principal moments of inertia and transverse angular velocity are discussed. The numerical simulation results show that the designed Halbach rotor stabilized the target attitude within an acceptable time. The electromagnetic nutation damping and despinning method provides new solutions for the development of on-orbit capture technology.  相似文献   
1000.
《中国航空学报》2020,33(6):1703-1716
An adaptive optimal trajectory tracking controller is presented for the Solid-Rocket-Powered Vehicle (SRPV) with uncertain nonlinear non-affine dynamics in the framework of adaptive dynamic programming. First, considering that the ascent model of the SRPV is non-affine, a model-free Single Network Adaptive Critic (SNAC) method is developed based on the dynamic neural network and the traditional SNAC method. This developed model-free SNAC method overcomes the limitation of the traditional SNAC method that can only be applied to affine systems. Then, a closed-form adaptive optimal controller is designed for the non-affine dynamics of SRPVs. This controller can adjust its parameters under different flight conditions and converge to the approximate optimal controller through online self-learning. Finally, the convergence to the approximate optimal controller is proved. The theoretical analysis of the uniformly ultimate boundedness of the tracking error is also presented. Simulation results demonstrate the effectiveness of the proposed controller.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号