全文获取类型
收费全文 | 2461篇 |
免费 | 28篇 |
国内免费 | 12篇 |
专业分类
航空 | 979篇 |
航天技术 | 907篇 |
综合类 | 12篇 |
航天 | 603篇 |
出版年
2022年 | 13篇 |
2021年 | 27篇 |
2019年 | 24篇 |
2018年 | 73篇 |
2017年 | 61篇 |
2016年 | 49篇 |
2015年 | 20篇 |
2014年 | 78篇 |
2013年 | 91篇 |
2012年 | 71篇 |
2011年 | 137篇 |
2010年 | 102篇 |
2009年 | 145篇 |
2008年 | 148篇 |
2007年 | 77篇 |
2006年 | 63篇 |
2005年 | 76篇 |
2004年 | 78篇 |
2003年 | 81篇 |
2002年 | 56篇 |
2001年 | 75篇 |
2000年 | 39篇 |
1999年 | 47篇 |
1998年 | 52篇 |
1997年 | 49篇 |
1996年 | 41篇 |
1995年 | 56篇 |
1994年 | 34篇 |
1993年 | 38篇 |
1992年 | 50篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 41篇 |
1988年 | 19篇 |
1987年 | 16篇 |
1986年 | 13篇 |
1985年 | 60篇 |
1984年 | 51篇 |
1983年 | 41篇 |
1982年 | 41篇 |
1981年 | 56篇 |
1980年 | 34篇 |
1979年 | 16篇 |
1978年 | 17篇 |
1977年 | 9篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1974年 | 12篇 |
1971年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有2501条查询结果,搜索用时 740 毫秒
271.
Chikovani V.V. Yatsenko Yu.A. Barabashov A.S. Marusyk P.I. Umakhanov E.O. Taturin V.N. 《Aerospace and Electronic Systems Magazine, IEEE》2009,24(5):40-43
Metallic resonator Q-factor is very sensitive to the resonator's material, its thermal and chemical treatment, design, and environment; i.e., pressure and temperature. In order to obtain higher accuracy for CVG it is necessary to use resonator evacuation. Resonator mass plays a very important role in sensitivity to angle rate, in stability of vibration, in response to environmental condition changes, and also to external vibration and shock resistance. tnnalabs Holding Inc. uses a cylindrical resonator with increased rim thickness of up to 2 mmn and more. This concerns resonator material and design parameters selection, material thermal treatment to increase resonator Q-factor, and improved control algorithms in order to increase metallic CVG accuracy. As a result, CVG bias instability of 0.025 degth and random walk of 0.008 degvh for the resonator diameter 43 mmn, and 0.2 deg/h for the resonator diameter 25 mm were obtained. Future opportunities for Innalabs CVG is also discussed herein. Test results are presented for CVG43 and CVG25. Three-axis CVG unit under control of one DSP "Sharc" and IMU parameters are forecasted. 相似文献
272.
P. P. Pavlov R. S. Litvinenko M. N. Mubarakhin I. O. Yushin V. M. Nigmatullin 《Russian Aeronautics (Iz VUZ)》2008,51(2):198-204
A technique for selecting a rational variant of a multifunctional aircraft system using the analytic hierarchy process is proposed and a solution of a practical problem is presented. 相似文献
273.
T.P. Dachev B. Tomov Yu. Matviichuk Pl. Dimitrov N. Bankov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
The paper presents observation of relativistic electrons. Data are collected by the Radiation Risk Radiometer-Dosimeters (R3D) B2/B3 modifications during the flights of Foton M2/M3 satellites in 2005 and 2007 as well as by the R3DE instrument at the European Technology Exposure Facility (EuTEF) on the Columbus External Payload Adaptor at the International Space Station (ISS) in the period February 20 – April 28, 2008. On the Foton M2/M3 satellites relativistic electrons are observed more frequently than on the ISS because of higher (62.8°) inclination of the orbit. At both Foton satellites the usual duration of the observations are a few minutes long. On the ISS the duration usually is about 1 min or less. The places of observations of high doses due to relativistic electrons are distributed mainly at latitudes above 50° geographic latitude in both hemispheres on Foton M2/M3 satellites. A very high maximum is found in the southern hemisphere at longitudinal range 0°–60°E. At the ISS the maximums are observed between 45° and 52° geographic latitude in both hemispheres mainly at longitudes equatorward from the magnetic poles. The measured absolute maximums of dose rates generated by relativistic electrons are found to be as follows: 304 μGy h−1 behind 1.75 g cm−2 shielding at Foton M2, 2314 μGy h−1 behind 0.71 g cm−2 shielding at Foton M3 and 19,195 μGy h−1 (Flux is 8363 cm−2 s−1) behind les than 0.4 g cm−2 shielding at ISS. 相似文献
274.
Wilmot N. Hess 《Space Science Reviews》1962,1(2):278-312
A survey is given of the high energy particle populations in the inner radiation belt. The experiments which have given information about particles are discussed and the best experimental information about particle fluxes and spectra presented. Calculations are given which deal with the particles and indicate what particle sources and loss processes are most important. The role of neutrons in making the inner belt is considered in detail and the need for particle acceleration and/or other sources is shown. 相似文献
275.
276.
R. N. DeWitt 《Space Science Reviews》1967,7(2-3):211-227
277.
D. S. Ivanov N. A. Ivlev S. O. Karpenko M. Yu. Ovchinnikov D. S. Roldugin S. S. Tkachev 《Cosmic Research》2014,52(3):205-215
The attitude control system of the Chibis-M microsatellite is described. Results of flight experiments on damping the initial angular velocity (made using magnetorquers) are considered, as well as stabilization in the orbital referece frame, and orientation of solar arrays toward the Sun using reaction wheels. The operation of algorithms of satellite attitude determination on sunlit and shadow segments of the orbit is also under study. The general logic of operation of the attitude control system in automatic mode is presented and discussed. 相似文献
278.
L.M. Mukhin D.F. Nenarokov N.V. Porschnev V.B. Bondarev B.G. Gelman G. Israel F. Raulin J. Runavot R. Thomas 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1987,7(12):329-335
SIGMA - 3 gas chromatograph on board VEGA 1 and 2 landing probes has been operated successfully in the 60 - 50 km altitude range, providing several in - situ chemical analysis of the gas and the aerosols of Venus cloud layers. Post flight calibration required to derive atmospheric abundancies from gas chromatograms were carried out using the SIGMA - 3 spare model. A Venus atmospheric aerosol simulation chamber was used in which sulfuric acid droplets were generated. Preliminary results of these calibration experiments indicate that the concentration of sulfuric acid in the upper part of the clouds ( 60 to 55 km) is about 1 mg/m3 and suggest that an additional constituant must be present in noticeable amount in the aerosols. From these experiments the mixing ratio upper limits of SO2 is 100 ppmV and of H2S and COS is few 10 ppmV. 相似文献
279.
S. Suresh S. N. Omkar V. Mani T. N. Guru Prakash 《Aerospace Science and Technology》2003,7(8):2114-602
In this paper, identification of dynamic stall effect of rotor blade is considered. Recurrent Neural Networks have the ability to identify the nonlinear dynamical systems from training data. This paper describes the use of recurrent neural networks for predicting the coefficient of lift (CZ) at high angle of attack. In our approach, the coefficient of lift (CZ) obtained from the experimental results (wind tunnel data) at different mean angle of attack θmean is used to train the recurrent neural network. Then the recurrent neural network prediction is compared with experimental ONERA OA212 airfoil data. The time and space complexity required to predict CZ in the proposed method is less and it is easy to incorporate in any commercially available rotor code. 相似文献
280.
I M Shirobokova N S Pechurkin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2003,31(7):1737-1741
A mathematical model was used to investigate the effect of cannibalism intensity on the net primary production and the dynamics of trophic links in an aquatic ecosystem characterized by cannibalism at the upper trophic level. A mathematical model of an aquatic ecosystem has been constructed, with the following principal trophic links: limiting nutrient concentration, producers (phytoplankton), nonpredatory and predatory zooplankton. The model takes into account the age structure of the predator and includes two age groups (the young and adults). The adult predators are cannibals feeding on both nonpredatory zooplankton and their own young, which consume phytoplankton. It has been found that when cannibalism intensity increases above a certain level, the concentrations of both adults and the young of the predators decrease. At the same time, the concentrations of the nonpredatory zooplankton and of nutrients increase, while the biomass of producers decreases. When the cannibalism intensity is low, the net primary production of the system increases to a certain level correlated with the increase in cannibalism intensity and drops sharply when the level of consumption of young is high. There is an optimal intensity of cannibalism, at which the productivity in the photosynthesis link is maximal. 相似文献