全文获取类型
收费全文 | 8939篇 |
免费 | 19篇 |
国内免费 | 26篇 |
专业分类
航空 | 4095篇 |
航天技术 | 3088篇 |
综合类 | 34篇 |
航天 | 1767篇 |
出版年
2021年 | 83篇 |
2019年 | 62篇 |
2018年 | 237篇 |
2017年 | 163篇 |
2016年 | 138篇 |
2015年 | 64篇 |
2014年 | 209篇 |
2013年 | 253篇 |
2012年 | 257篇 |
2011年 | 418篇 |
2010年 | 309篇 |
2009年 | 439篇 |
2008年 | 486篇 |
2007年 | 323篇 |
2006年 | 204篇 |
2005年 | 251篇 |
2004年 | 219篇 |
2003年 | 266篇 |
2002年 | 182篇 |
2001年 | 281篇 |
2000年 | 160篇 |
1999年 | 200篇 |
1998年 | 236篇 |
1997年 | 143篇 |
1996年 | 207篇 |
1995年 | 243篇 |
1994年 | 247篇 |
1993年 | 158篇 |
1992年 | 194篇 |
1991年 | 77篇 |
1990年 | 75篇 |
1989年 | 187篇 |
1988年 | 77篇 |
1987年 | 83篇 |
1986年 | 85篇 |
1985年 | 248篇 |
1984年 | 195篇 |
1983年 | 156篇 |
1982年 | 175篇 |
1981年 | 261篇 |
1980年 | 71篇 |
1979年 | 77篇 |
1978年 | 67篇 |
1977年 | 51篇 |
1975年 | 58篇 |
1974年 | 45篇 |
1973年 | 41篇 |
1972年 | 43篇 |
1971年 | 42篇 |
1970年 | 45篇 |
排序方式: 共有8984条查询结果,搜索用时 301 毫秒
661.
A wireless sensor system for data acquisition and processing during structural and fatigue tests is considered. A prototype of wireless strain-gauge measurement system is used in fatigue tests of a utility helicopter’s main rotor hub. The setup of the test rig and software are described. 相似文献
662.
S. V. Falaleev 《Russian Aeronautics (Iz VUZ)》2017,60(2):229-235
The paper studies different types of dampers for rotor supports of gas turbine engines (GTE). The advantages of hydrodynamic dampers are shown. Hydrodynamic dampers for GTE rotor supports are studied. A new design and technique of calculation are proposed for an adjustable hydrodynamic damper. 相似文献
663.
In the paper, processes of high-energy electron beam interaction with plasma particles in a discharge channel of a stationary plasma thruster are analyzed and the results are presented. 相似文献
664.
Reconfiguration of multiprocessor systems makes it possible to improve their failure-resistance that is especially important for the integrated modular avionics systems. The algorithm considered in this paper allows minimizing the reservation and providing the better safety level and more effective flight completion or even its further execution in the case of failures of airborne equipment. 相似文献
665.
K. Patel Ashutosh K. Singh P. Subrahmanyam A.K. Singh 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
The presence and movement of plasma density fluctuations in the F-region of the ionosphere are studied by monitoring phase and amplitude of radio waves propagating through the region. In this paper, we have used weak scattering theory and assumed the plasma density fluctuations to behave like phase changing diffraction screen. Appropriate relations for scintillation index S4, and phase variance δ? are derived and computed for different parameters of the plasma density irregularities of the ionosphere. SROSS-C2 satellite in situ measurements of plasma density fluctuations, which provide direct information about the structure and morphology of irregularities that are responsible for scintillation of radio waves, were used first time to develop a scintillation model for low latitude. It is observed that the scintillation index S4 and phase variance δ? depends on the strength of the plasma turbulence. Finally, the results obtained from modeling are compared and discussed with the available recent results. 相似文献
666.
A. Hovhannisyan A. Chilingarian 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
Particle detectors of worldwide networks are continuously measuring various secondary particle fluxes incident on Earth surface. At the Aragats Space Environmental Center (ASEC), the data of 12 cosmic ray particle detectors with a total of ∼280 measuring channels (count rates of electrons, muons and neutrons channels) are sent each minute via wireless bridges to a MySQL database. These time series are used for the different tasks of off-line physical analysis and for online forewarning services. Usually long time series contain several types of errors (gaps due to failures of high or low voltage power supply, spurious spikes due to radio interferences, abrupt changes of mean values of several channels or/and slowly trends in mean values due to aging of electronics components, etc.). To avoid erroneous physical inference and false alarms of alerting systems we introduce offline and online filters to “purify” multiple time-series. In the presented paper we classify possible mistakes in time series and introduce median filtering algorithms for online and off-line “purification” of multiple time-series. 相似文献
667.
Pooja Dutt R.K. Sharma 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2011
A study of the evolution of the periodic and the quasi-periodic orbits near the Lagrangian point L2, which is located to the right of the smaller primary on the line joining the primaries and whose distance from the more massive primary is greater than the distance between the primaries, in the framework of restricted three-body problem for the Sun–Jupiter, Earth–Moon (relatively large mass ratio) and Saturn–Titan (relatively small mass ratio) systems is made. Two families of periodic orbits around the smaller primary are identified using the Poincaré surface of section method – family I (initially elliptical, gradually becomes egg-shaped with the increase in the Jacobi constant C and elongated towards the more massive primary) and family II (initially egg-shaped orbits elongated towards L2 and gradually becomes elliptical with the increase in C). The family I in the Sun–Jupiter and Saturn–Titan systems contains two separatrix caused by third-order and fourth-order resonances, while the Earth–Moon system has only one separatrix which is caused by third-order resonances. Also in the Sun–Jupiter and the Saturn–Titan systems, family I merge with family II, around Jacobian constant 3.0393 and 3.0163, respectively, while in the Earth–Moon system, family II evolves separately from two different branches. The two branches merge at C = 3.184515. In the Earth–Moon system, the family II contains a separatrix due to third-order resonances which is absent in the other two systems. 相似文献
668.
S. O. Karpenko N. V. Kupriyanova M. Yu. Ovchinnikov V. I. Penkov A. S. Selivanov O. E. Khromov 《Cosmic Research》2010,48(6):517-525
The results of designing the attitude control system of the first Russian nanosatellite TNS-0 no. 1 providing orientation of its longitudinal axis along the local geomagnetic field induction vector are presented. The system
consists of a permanent magnet and two sets of hysteresis rods. The magnetic and geometric parameters of the magnet and rods
are calculated. The influence of the permanent magnet field on the hysteresis rods and mutual influence of the rods in the
case of compact satellite packaging are analyzed. Examples of calculations of transient processes and steady-state angular
satellite motion are presented. 相似文献
669.
670.
V. M. Soldatkin A. A. Arkhipov V. A. Olaev A. A. Uglov 《Russian Aeronautics (Iz VUZ)》2012,55(2):184-191
We consider the function, the problems being solved and the construction principles for a starting system of warning the critical regimes for a single-rotor helicopter at parking, taxiing and maneuvering on the ground, takeoff and landing as well as at descending and hovering regimes. The structural-functional scheme and the algorithms of system channel warning are presented. 相似文献