首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9544篇
  免费   58篇
  国内免费   47篇
航空   4462篇
航天技术   3164篇
综合类   91篇
航天   1932篇
  2021年   99篇
  2019年   54篇
  2018年   229篇
  2017年   187篇
  2016年   135篇
  2015年   80篇
  2014年   220篇
  2013年   280篇
  2012年   275篇
  2011年   455篇
  2010年   342篇
  2009年   465篇
  2008年   509篇
  2007年   341篇
  2006年   234篇
  2005年   282篇
  2004年   233篇
  2003年   275篇
  2002年   205篇
  2001年   289篇
  2000年   191篇
  1999年   224篇
  1998年   250篇
  1997年   177篇
  1996年   216篇
  1995年   266篇
  1994年   263篇
  1993年   161篇
  1992年   199篇
  1991年   82篇
  1990年   77篇
  1989年   188篇
  1988年   85篇
  1987年   79篇
  1986年   81篇
  1985年   247篇
  1984年   191篇
  1983年   155篇
  1982年   154篇
  1981年   272篇
  1980年   70篇
  1979年   65篇
  1978年   75篇
  1977年   59篇
  1976年   48篇
  1975年   78篇
  1974年   55篇
  1972年   64篇
  1971年   59篇
  1970年   50篇
排序方式: 共有9649条查询结果,搜索用时 609 毫秒
771.
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   
772.
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   
773.
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   
774.
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   
775.
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   
776.
777.
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   
778.
The problem of determining the “potential” number of integration steps by explicit difference schemes is solved within the framework of the prediction model for chemically non-equilibrium processes.  相似文献   
779.
The Juno Waves Investigation   总被引:1,自引:0,他引:1  
Jupiter is the source of the strongest planetary radio emissions in the solar system. Variations in these emissions are symptomatic of the dynamics of Jupiter’s magnetosphere and some have been directly associated with Jupiter’s auroras. The strongest radio emissions are associated with Io’s interaction with Jupiter’s magnetic field. In addition, plasma waves are thought to play important roles in the acceleration of energetic particles in the magnetosphere, some of which impact Jupiter’s upper atmosphere generating the auroras. Since the exploration of Jupiter’s polar magnetosphere is a major objective of the Juno mission, it is appropriate that a radio and plasma wave investigation is included in Juno’s payload. This paper describes the Waves instrument and the science it is to pursue as part of the Juno mission.  相似文献   
780.
The paper discusses a method of designing the neural controller for two-channel control of a technical object by an example of the roll and yaw control depending on deviations, velocities and accelerations of their variation.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号