全文获取类型
收费全文 | 3142篇 |
免费 | 775篇 |
国内免费 | 569篇 |
专业分类
航空 | 2462篇 |
航天技术 | 674篇 |
综合类 | 371篇 |
航天 | 979篇 |
出版年
2024年 | 16篇 |
2023年 | 45篇 |
2022年 | 136篇 |
2021年 | 151篇 |
2020年 | 153篇 |
2019年 | 128篇 |
2018年 | 138篇 |
2017年 | 181篇 |
2016年 | 127篇 |
2015年 | 187篇 |
2014年 | 220篇 |
2013年 | 207篇 |
2012年 | 244篇 |
2011年 | 220篇 |
2010年 | 264篇 |
2009年 | 251篇 |
2008年 | 240篇 |
2007年 | 239篇 |
2006年 | 210篇 |
2005年 | 161篇 |
2004年 | 117篇 |
2003年 | 140篇 |
2002年 | 120篇 |
2001年 | 77篇 |
2000年 | 97篇 |
1999年 | 73篇 |
1998年 | 63篇 |
1997年 | 48篇 |
1996年 | 43篇 |
1995年 | 33篇 |
1994年 | 30篇 |
1993年 | 28篇 |
1992年 | 26篇 |
1991年 | 21篇 |
1990年 | 15篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1965年 | 1篇 |
排序方式: 共有4486条查询结果,搜索用时 15 毫秒
1.
2.
Fault mode probability factor based fault-tolerant control for dissimilar redundant actuation system
This paper presents a Fault Mode Probability Factor (FMPF) based Fault-Tolerant Control (FTC) strategy for multiple faults of Dissimilar Redundant Actuation System (DRAS) composed of Hydraulic Actuator (HA) and Electro-Hydrostatic Actuator (EHA). The long-term service and severe working conditions can result in multiple gradual faults which can ultimately degrade the system performance, resulting in the system model drift into the fault state characterized with parameter uncertainty. The paper proposes to address this problem by using the historical statistics of the multiple gradual faults and the proposed FMPF to amend the system model with parameter uncertainty. To balance the system model precision and computation time, a Moving Window (MW) method is used to determine the applied historical statistics. The FMPF based FTC strategy is developed for the amended system model where the system estimation and Linear Quadratic Regulator (LQR) are updated at the end of system sampling period. The simulations of DRAS system subjected to multiple faults have been performed and the results indicate the effectiveness of the proposed approach. 相似文献
5.
Magnetic field was introduced in laser melting deposition to reduce the pores in workpieces.Finite 3-D model of the coil-deposition layer-substrate was established.Simulation results show that the electromagnetic force in deposition layer mainly concentrates in the projection area of the coil.Axial electromagnetic force shows repulsion in one cycle.The experimental results indicate that the magnetic field is beneficial for grain refinement,microhardness increasement and decline of quantities and average sizes of pores. 相似文献
6.
7.
葛军 《航空精密制造技术》2001,37(4):45-46
着重阐述了中华世纪坛在实际工作中为解决噪音问题所采用的测试方法,寻求一种解决长时间、多数据测试分析的途径。 相似文献
8.
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
9.
导弹在大攻角再入飞行过程中,偏航通道和滚动通道存在着气动交连耦合,当耦合影响较大时,采用传统的把耦合项当作随机干扰的办法来处理,容易造成系统失稳。因此采用基于H∞混合灵敏度解耦控制的方法对通道间进行解耦,对于H∞混合灵敏度加权函数,通过遗传算法优化获得,并推导了H∞混合灵敏度标准型的建立过程和遗传算法优化加权函数的步骤。应用该方法,对导弹大攻角飞行过程中通道间的解耦控制进行设计。仿真表明,对参数不确定性的耦合系统,该方法具有良好的解耦性和鲁棒稳定性。 相似文献