全文获取类型
收费全文 | 6443篇 |
免费 | 17篇 |
国内免费 | 15篇 |
专业分类
航空 | 3015篇 |
航天技术 | 2382篇 |
综合类 | 27篇 |
航天 | 1051篇 |
出版年
2021年 | 60篇 |
2019年 | 42篇 |
2018年 | 138篇 |
2017年 | 82篇 |
2016年 | 93篇 |
2015年 | 47篇 |
2014年 | 162篇 |
2013年 | 184篇 |
2012年 | 185篇 |
2011年 | 241篇 |
2010年 | 170篇 |
2009年 | 291篇 |
2008年 | 389篇 |
2007年 | 183篇 |
2006年 | 153篇 |
2005年 | 187篇 |
2004年 | 156篇 |
2003年 | 221篇 |
2002年 | 132篇 |
2001年 | 219篇 |
2000年 | 113篇 |
1999年 | 141篇 |
1998年 | 176篇 |
1997年 | 123篇 |
1996年 | 141篇 |
1995年 | 183篇 |
1994年 | 191篇 |
1993年 | 104篇 |
1992年 | 152篇 |
1991年 | 84篇 |
1990年 | 64篇 |
1989年 | 140篇 |
1988年 | 62篇 |
1987年 | 67篇 |
1986年 | 61篇 |
1985年 | 173篇 |
1984年 | 145篇 |
1983年 | 127篇 |
1982年 | 146篇 |
1981年 | 188篇 |
1980年 | 65篇 |
1979年 | 68篇 |
1978年 | 54篇 |
1977年 | 34篇 |
1976年 | 39篇 |
1975年 | 31篇 |
1974年 | 34篇 |
1973年 | 35篇 |
1972年 | 37篇 |
1970年 | 32篇 |
排序方式: 共有6475条查询结果,搜索用时 31 毫秒
21.
Servidia P.A. Sanchez Pena R.S. 《IEEE transactions on aerospace and electronic systems》2005,41(2):584-598
The attitude stabilization of a spacecraft using thrusters is considered from a practical point of view, i.e., when actuator constraints, uncertainties and failures, measurement noise, fuel consumption, and inertia matrix uncertainty are considered. A variable structure controller based on sliding modes is obtained first, which guarantees global exponential stability under actuator constraints, uncertainties, and failures. The design is based on a continuous average-proportional torque selection function and a set of feasible sliding surfaces, which may be adapted to improve performance. Exponential convergence towards ultimate bounds is guaranteed when all other practical issues arise. 相似文献
22.
Burns T.J. Rogers S.K. Oxley M.E. Ruck D.W. 《IEEE transactions on aerospace and electronic systems》1996,32(2):628-649
The wavelet filters of the conventional 3D multiresolution analysis possess homogeneous spatial and temporal frequency characteristics which limits one's ability to match filter frequency characteristics to signal frequency behavior. Also, the conventional 3D multiresolution analysis employs an oct-tree decomposition structure which restricts the analysis of signal details to identical resolutions in space and time. This paper presents a 3D wavelet multiresolution analysis constructed from nonhomogeneous spatial and temporal filters, and an orthogonal sub-band coding scheme that decouples the spatial and temporal decomposition processes 相似文献
23.
T. K. Sirazetdinov 《Russian Aeronautics (Iz VUZ)》2007,50(1):30-36
A brief review of studies on simulation and control of a porous cooling process taking into account material transpiration is given. An approximated solution for an equation of the one-dimensional problem of fast ablation is also presented. 相似文献
24.
S. K. Solanki M. Fligge 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2002,29(12):L169-1940
The contribution to total solar irradiance variations by the magnetic field at the solar surface is estimated. Detailed models of the irradiance changes on the basis of magnetograms show that magnetic features at the solar surface account for over 90% of the irradiance variations on a solar rotation time scale and at least 70% on a solar cycle time scale. If the correction to the VIRGO record proposed by Fröhlich & Finsterle (2001) is accepted, then magnetic features at the solar surface are responsible for over 90% of the solar cycle irradiance variations as well. 相似文献
25.
Ahmad F. Frazer G.J. Kassam S.A. Amin M.G. 《IEEE transactions on aerospace and electronic systems》2004,40(1):206-220
A coarray-based near-field, wideband synthetic aperture beamformer using stepped-frequency signal synthesis and post-data acquisition processing is presented. While coarray techniques offer significant reduction in the number of array elements for a given angular resolution, the hybrid subarray-stepped frequency realization of wideband systems simplifies implementations and offers flexibility in beamforming. Proof of concept is provided using real data collected in an anechoic chamber for several pulse shapes and array weightings. 相似文献
26.
Fiber optic fence sensor developments 总被引:1,自引:0,他引:1
Many detection technologies have been employed for perimeter detection, to sensitize a barrier. These outdoor perimeter fence detection sensors must reliably detect intruders attempting to cut or climb the barrier, while ignoring the effects of environmental noise, including nearby activity. In recent conference proceedings, the new IntelliFIBER/spl trade/ fiber optic based product was introduced and compared with previous technologies. IntelliFIBER is designed to provide the advantages of a nonconductive "dielectric" cable sensor, e.g., resistance to electromagnetic interference and the ability to provide longer cable zones. It utilizes the proven processor of the Intelli-FLEX/spl trade/ triboelectric cable fence sensor, which provides relay or bidirectional networked serial communications and is compatible with its calibration module. IntelliFIBER also capitalizes on the Intelli-FLEX's adaptive detection algorithms that were developed through extensive field-testing, to provide exceptional immunity to environmental alarms while still detecting the skilled intruder. 相似文献
27.
Lenz R. Schuler K. Younis M. Wiesbeck W. 《Aerospace and Electronic Systems Magazine, IEEE》2006,21(5):30-33
In April 2006, the TerraSAR-X satellite was launched. This paper describes the development of a novel and highly integrated, digitally-controlled active SAR system calibrator (DARC). It consists of both an active transponder path for absolute radiometric calibration and a calibrated receiver chain for antenna pattern evaluation of the satellite antenna. A total of 16 active transponder and receiver systems and 17 receiver-only systems will be fabricated for a calibration campaign in 2006. 相似文献
28.
I. S. Akhmed’yanov 《Russian Aeronautics (Iz VUZ)》2009,52(4):383-389
The application of the quadrature method [1] to analyzing the shells of revolution under symmetrical loading relative to the
zero meridian is considered. The method can be treated as a generalization of the method presented in [2] to solve the Volterra
integral equation of the second kind. 相似文献
29.
A Bayesian network (BN) is a compact representation for probabilistic models and inference. They have been used successfully for many military and civilian applications. It is well known that, in general, the inference algorithms to compute the exact a posterior probability of a target node given observed evidence are either computationally infeasible for dense networks or impossible for general hybrid networks. In those cases, one either computes the approximate results using stochastic simulation methods or approximates the model using discretization or a Gaussian mixture model before applying an exact inference algorithm. This paper combines the concept of simulation and model approximation to propose an efficient algorithm for those cases. The main contribution here is a unified treatment of arbitrary (nonlinear non-Gaussian) hybrid (discrete and continuous) BN inference having both computation and accuracy scalability. The key idea is to precompile the high-dimensional hybrid distribution using a hypercube representation and apply it for both static and dynamic BN inference. Since the inference process essentially becomes a combination of table look-up and some simple operations, the method is shown to be extremely efficient. It can also he scaled to achieve any desirable accuracy given sufficient preprocessing time and memory for the cases where exact inference is not possible 相似文献
30.
Garenaux K. Merlet T. Alouini M. Lopez J. Vodjdani N. Boula-Picard R. Fourdin C. Chazelas J. 《Aerospace and Electronic Systems Magazine, IEEE》2007,22(2):3-8
Radar systems require transmission of very high purity signals. Photonics is now mature enough to achieve analog transmission with very low noise, strong immunity, and wide-bandwidth even in harsh environments. We present our recent developments of optimized optical links dedicated to radar and multifunction systems 相似文献