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951.
滚转通道是飞行器控制的重要通道,且在试验中滚转单元受天平其它元干扰较大。为了准确测量滚转力矩,特别开发了带五分量抑制机构的高精度滚转测量技术。该技术设计原理是通过带机械深沟球轴承的抑制机构对除滚转力矩外的五个分量进行抑制。该技术一方面具有较高的滚转力矩测量灵敏度,另一方面能够有效抑制除滚转力矩外的其它五个分量,从而得到准确滚转力矩信号。 相似文献
952.
953.
D. Mori A.V. Koustov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
In this study SuperDARN Cross Polar Cap Potentials (CPCPs), collected over the year 2000, are investigated with a goal to statistically assess its relationship with various parameters of the solar wind and Interplanetary Magnetic Field (IMF). We show that SuperDARN CPCPs tend to cluster around discrete values, prescribed by the statistical model, unless the amount of points on each convection map is above ∼300. By selecting CPCP data obtained with radar coverage of >300 points, we investigate the CPCP relationship with IMF Bz and By, IMF clock angle, solar wind speed and dynamic pressure, Alfven velocity, Alfven–Mach number, and interplanetary electric field. Some reported tendencies, such as dependence upon IMF Bz, were found to be consistent with measurements by other instruments. We demonstrate that SuperDARN CPCPs show consistency with several theories/empirical models (predicting the CPCP) in terms of a linear trend but, on average, the slopes of the dependencies are at least two times smaller. We also determine the coupling function, out of those published in literature, best correlating with SuperDARN CPCPs. 相似文献
954.
Energisation of O+ and O+
2 Ions at Mars: An Analysis of a 3-D Quasi-Neutral Hybrid Model Simulation
E. Kallio A. Fedorov S. Barabash P. Janhunen H. Koskinen W. Schmidt R. Lundin H. Gunell M. Holmström Y. Futaana M. Yamauchi A. Grigoriev J. D. Winningham R. Frahm J. R. Sharber 《Space Science Reviews》2006,126(1-4):39-62
We have studied the loss of O+ and O+
2 ions at Mars with a numerical model. In our quasi-neutral hybrid model ions (H+, He++, O+, O+
2) are treated as particles while electrons form a massless charge-neutralising fluid. The employed model version does not
include the Martian magnetic field resulting from the crustal magnetic anomalies. In this study we focus the Martian nightside
where the ASPERA instrument on the Phobos-2 spacecraft and recently the ASPERA-3 instruments on the Mars Express spacecraft
have measured the proprieties of escaping atomic and molecular ions, in particular O+ and O+
2 ions. We study the ion velocity distribution and how the escaping planetary ions are distributed in the tail. We also create
similar types of energy-spectrograms from the simulation as were obtained from ASPERA-3 ion measurements. We found that the
properties of the simulated escaping planetary ions have many qualitative and quantitative similarities with the observations
made by ASPERA instruments. The general agreement with the observations suggest that acceleration of the planetary ions by
the convective electric field associated with the flowing plasma is the key acceleration mechanism for the escaping ions observed
at Mars. 相似文献
955.
电弧风洞是进行防热材料和防热结构考核与研究的必要设备,也是高超声速地面试验能力的重要组成部分,但电弧加热器的电极烧蚀会导致较为严重的流场污染,影响试验准确性。利用可调谐二极管激光吸收光谱技术(TDLAS),通过对20 MW级片式电弧加热器内部流场中Cu原子809.25 nm跃迁谱线进行实时测量,研究了电弧风洞流场中Cu污染情况和电极烧蚀情况。在获得Cu原子该谱线低能态数密度基础上,估算了运行功率分别在7.3、8.7、10.0和11.7 MW时流场中Cu组分(原子态和离子态)总数密度平均为10.6×1013、11.2×1013、11.7×1013和16.4×1013 cm-3,同时得到平均电极烧蚀率约为1.65×10-5 g/C。试验还发现,TDLAS信号在高温流场建立阶段起伏变化明显,并且在功率跃变时也会出现突然增强而后迅速回落的现象,表明电弧抖动会使电极烧蚀严重加剧。 相似文献
956.
A. W. Hood 《Space Science Reviews》1999,87(1-2):79-92
Theories and observations of energy input, heating and acceleration mechanisms in the low corona were presented and discussed.
The main topics of discussion were large-scale solar wind simulations, theoretical heating mechanisms, observational constraints,
confronting theory with observations and observational issues.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
957.
FLUTTER SUPPRESSION USING DISTRIBUTED PIEZOELECTRIC ACTUATORS 总被引:1,自引:1,他引:0
The Flutter suppression using distributed piezoelectric actuators has been analyzed and tested. In constructing the finite element equation, effects of piezoelectric matrices are investigated. LQG method is used in designing the control law. In reducing the order of the control law, both balance realization and LK methods are used. For the rational approximation of the unsteady aerodynamic forces LS method is improved. In determining the piezoelectric constants d31 a new dynamic response method is developed. Laser vibrameter is used to pick up the model response and in ground resonance test the model is excited by piezoelectric actuators. Reasonable agreement of the wind tunnel flutter suppression test with calculated results is obtained. 相似文献
958.
H. Shimazu K. Kitamura T. Tanaka S. Fujita M.S. Nakamura T. Obara 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008,42(9):1504-1509
We have developed a real-time global MHD (magnetohydrodynamics) simulation of the solar wind interaction with the earth’s magnetosphere. By adopting the real-time solar wind parameters and interplanetary magnetic field (IMF) observed routinely by the ACE (Advanced Composition Explorer) spacecraft, responses of the magnetosphere are calculated with MHD code. The simulation is carried out routinely on the super computer system at National Institute of Information and Communications Technology (NICT), Japan. The visualized images of the magnetic field lines around the earth, pressure distribution on the meridian plane, and the conductivity of the polar ionosphere, can be referred to on the web site (http://www2.nict.go.jp/y/y223/simulation/realtime/).The results show that various magnetospheric activities are almost reproduced qualitatively. They also give us information how geomagnetic disturbances develop in the magnetosphere in relation with the ionosphere. From the viewpoint of space weather, the real-time simulation helps us to understand the whole image in the current condition of the magnetosphere. To evaluate the simulation results, we compare the AE indices derived from the simulation and observations. The simulation and observation agree well for quiet days and isolated substorm cases in general. 相似文献
959.
960.
Ovidiu Maris Georgeta Maris 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,35(12):2129-2140
The high-speed plasma streams in the solar wind are investigated during the solar cycles nos. 20–22 (1964–1996), separately on the two types of streams according to their solar origin: the HSPS produced by coronal holes (co-rotating) and the flare-generated, in keeping with the classification made in different catalogues. The analysis is performed taking into account the following high-speed stream parameters: the durations (in days), the maximum velocities, the velocity gradients and, the importance of the streams. The time variation of these parameters and the high-speed plasma streams occurrence rate show an 11-year periodicity with some differences between the solar cycles considered. A detailed analysis of the high-speed stream 11-year cycles is made by comparison with the “standard” cycles of the sunspot relative number (Wolf number). The different behaviour of the high-speed stream parameters between even and odd solar cycles could be due to the 22-year solar magnetic cycle. The increased activity of the high-speed plasma streams on the descendant phases of the cycles, regardless of their solar sources, proves the existence of some special local conditions of the solar plasma and the magnetic field on a large scale that allow the ejection of the high energy plasma streams. This fact has led us to the analysis the stream parameters during the different phases of the solar cycles (minimum, ascendant, maximum and, descendant) as well as during the polar magnetic field reversal intervals. The differences between the phases considered are pointed out. The solar cycles 20 and 22 reveal very similar dynamics of the flare-generated and also co-rotating stream parameters during the maximum, descendant and reversal intervals. This fact could be due to their position in a Hale Cycle (the first component of the 22-year solar magnetic cycle). The 21st solar cycle dominance of all co-rotating stream parameters against the 20th and 22nd solar cycle ones, during almost all phases, could be due to the same structure of a Hale Cycle – solar cycle 21 is the second component in a 22-year SC. During the reversal intervals, all high-speed stream parameters have comparable values with the ones of the maximum phases of the cycles even if this interval contains a small part of the descendant branch (solar cycles 20 and 22). 相似文献