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   3504篇
  免费   73篇
  国内免费   31篇
航空   1386篇
航天技术   1101篇
综合类   50篇
航天   1071篇
  2022年   27篇
  2021年   65篇
  2020年   19篇
  2019年   30篇
  2018年   146篇
  2017年   113篇
  2016年   128篇
  2015年   54篇
  2014年   122篇
  2013年   151篇
  2012年   132篇
  2011年   184篇
  2010年   147篇
  2009年   207篇
  2008年   204篇
  2007年   136篇
  2006年   86篇
  2005年   114篇
  2004年   105篇
  2003年   124篇
  2002年   98篇
  2001年   122篇
  2000年   42篇
  1999年   63篇
  1998年   62篇
  1997年   42篇
  1996年   44篇
  1995年   81篇
  1994年   64篇
  1993年   35篇
  1992年   47篇
  1990年   19篇
  1989年   42篇
  1988年   11篇
  1987年   17篇
  1986年   16篇
  1985年   72篇
  1984年   57篇
  1983年   51篇
  1982年   45篇
  1981年   86篇
  1980年   25篇
  1979年   16篇
  1978年   14篇
  1977年   17篇
  1976年   14篇
  1975年   13篇
  1974年   12篇
  1972年   13篇
  1971年   11篇
排序方式: 共有3608条查询结果,搜索用时 0 毫秒
621.
    
Quasi-static microaccelerations are estimated for a satellite specially designed to perform space experiments in the field of microgravity. Three modes of attitude motion of the spacecraft are considered: passive gravitational orientation, orbital orientation, and semi-passive gravitational orientation. In these modes the lengthwise axis of the satellite is directed along the local vertical, while solar arrays lie in the orbit plane. The second and third modes are maintained using electromechanical executive devices: flywheel engines or gyrodynes. Estimations of residual microaccelerations are performed with the help of mathematical modeling of satellite’s attitude motion under the action of gravitational and aerodynamic moments, as well as the moment produced by the gyro system. It is demonstrated that all modes ensure rather low level of quasi-static microaccelerations on the satellite and provide for a fairly narrow region of variation for the vector of residual microacceleration. The semi-passive gravitational orientation ensures also a limited proper angular momentum of the gyro system.  相似文献   
622.
Cosmic Research - The results of an analysis of the space–time characteristics and dynamics of precipitations of magnetospheric electrons with energies in the range from 0.1 to 0.7 MeV are...  相似文献   
623.
The results of measurements of fluxes and spectra carried out using the RELEC (relativistic electrons) equipment onboard the VERNOV satellite in the second half of 2014 are presented. The VERNOV satellite was launched on July 8, 2014 in a sun-synchronous orbit with an altitude from 640 to 830 km and an inclination of 98.4°. Scientific information from the satellite was first received on July 20, 2014. The comparative analysis of electron fluxes using data from RELEC and using experimental data on the electron detection by satellites Elektro-L (positioned at a geostationary orbit) and Meteor-M no. 2 (positioned at a circular polar orbit at an altitude of about 800 km as the VERNOV satellite) will make it possible to study the spatial distribution pattern of energetic electrons in near-Earth space in more detail.  相似文献   
624.
为研究和探索火箭发动机地面试验推力室脉动压力测量方法和数据分析技术,介绍了火箭发动机试验中脉动压力测量系统的组成和参数的测量方法;分析了引压导管的动态特性及其对脉动压力参数测量的影响;采用齐平安装的方式,按照所述方法建立脉动压力参数测量系统;结合推力室多个振动测点的数据,分别采用快速傅里叶变换(FFT)和小波包分解两种...  相似文献   
625.
We consider in detail the intense Pc5 pulsations of the magnetic field, riometric absorption, and electron fluxes occurred on the recovery phase of the strong magnetic storm on November 21, 2003. The global structure of these disturbances is studied using the world network of magnetometers and riometers supplemented by the data of particle detectors onboard the LANL geosynchronous satellites. The local spatial structure is investigated according to data of the regional network of Finnish vertical riometers and of stations of the IMAGE magnetic network. Though a certain similarity is observed in the frequency composition and time evolution of the variations of magnetic field and riometric absorption, the local spatial structure of these oscillations turns out to be different. It is suggested that these variations can be manifestations of oscillatory properties of two weakly connected systems: the magnetospheric MHD waveguide/resonator and the system cyclotron noise + electrons. The recorded Pc5 oscillations are, presumably, a result of excitation of the magnetospheric waveguide on the morning and evening flanks of the magnetosphere. At high velocities of the solar wind this waveguide can appear in a metastable state. Not only jumps in the solar wind density, but injection of electrons into the magnetosphere as well, can serve as a trigger for the waveguide excitation.  相似文献   
626.
Spatial structure of the magnetosheath of the Earth was studied under the conditions when no sharp (more than 40° during 5 min) changes in the interplanetary magnetic field direction were observed. On the basis of 24 flights of the Interball-1 satellite through the magnetosheath, it is found that three regions differing from each other by parameters of the field and plasma can be observed in the magnetosheath under the above-indicated conditions. These regions also differ from the solar wind region before front of the Earth’s magnetospheric bow shock. Empirical distributions of parameters were studied in each region. Taking into account the influence of the interplanetary magnetic field direction on the processes in the magnetosheath, the cases of quasi-perpendicular and quasi-parallel shock waves were considered separately. The study showed that the distribution of parameters in the selected regions (in the solar wind before front of the bow shock, in the magnetosheath behind the bow shock (post-shock), in the region of the magnetosheath with minimal fluctuations in the field, and in the inner magnetosheath) differ from each other at any interplanetary magnetic field direction.  相似文献   
627.
The influence of zonal and meridional components of the neutral wind under anthropogenic impacts of water molecules on the ionospheres electron concentration distributed along a magnetic field tube is considered. Computer simulation method based on a mathematical model of the F2 region along a field tube is used.Translated from Kosmicheskie Issledovaniya, Vol. 43, No. 1, 2005, pp. 76–80.Original Russian Text Copyright © 2005 by Medvedev, Ishanov, Zenkin.  相似文献   
628.
629.
The influence of various control systems of the orbital motion of a technological spacecraft on the level of microacceleration of its internal environment is simulated. Conclusions are drawn about the effectiveness of control systems with different actuators for realization of certain gravitationally sensitive processes onboard a spacecraft.  相似文献   
630.
Dynamics of planets around other stars that demonstrate a variety of possible characteristics is of interest from the point of view of realization of new scenarios of evolution which have not been realized in the Solar System. We consider the rotational evolution of exoplanets under the action of gravitational perturbations and magnetic disturbances using the methods of quality analysis and theory of bifurcation of multiparametric differential equations that describe evolution of non-resonant rotation of a dynamically symmetric planet magnetized along its symmetry axis. We analyze 64 phase portraits describing the evolution of angular momentum vector L for all possible values of planet parameters. The values of parameters are determined for the case when the direct rotation of a planet is changed for its retrograde rotation.  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