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   4792篇
  免费   34篇
  国内免费   16篇
航空   1943篇
航天技术   1624篇
综合类   25篇
航天   1250篇
  2022年   22篇
  2021年   52篇
  2019年   35篇
  2018年   163篇
  2017年   130篇
  2016年   132篇
  2015年   51篇
  2014年   148篇
  2013年   181篇
  2012年   158篇
  2011年   245篇
  2010年   188篇
  2009年   285篇
  2008年   286篇
  2007年   171篇
  2006年   111篇
  2005年   140篇
  2004年   141篇
  2003年   159篇
  2002年   113篇
  2001年   162篇
  2000年   63篇
  1999年   89篇
  1998年   99篇
  1997年   81篇
  1996年   74篇
  1995年   115篇
  1994年   84篇
  1993年   58篇
  1992年   78篇
  1991年   21篇
  1990年   33篇
  1989年   68篇
  1988年   28篇
  1987年   31篇
  1986年   27篇
  1985年   116篇
  1984年   96篇
  1983年   79篇
  1982年   73篇
  1981年   122篇
  1980年   55篇
  1979年   29篇
  1978年   30篇
  1977年   25篇
  1976年   28篇
  1975年   26篇
  1974年   22篇
  1972年   19篇
  1971年   17篇
排序方式: 共有4842条查询结果,搜索用时 687 毫秒
391.
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   
392.
393.
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   
394.
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   
395.
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   
396.
The methodology is proposed and the mathematical model is developed for the purpose of numerical simulation of the power circuit of the gas-hydraulic actuator with displacing power source for the gimbaled nozzle control. It provides the highest power efficiency factor of the actuator as a part of aircraft by means of pulling together the profiles of available and required power.  相似文献   
397.
Built in cooperation with China, at the end of 2008 the Bolivarian Republic of Venezuela launched its first telecommunications satellite which operates in C, Ku and Ka bands. Using published and unpublished information, this report describes the potential role of the Venesat-1 satellite in promoting development in Venezuela and Latin America. The core of Venezuelan space policy has deep social roots and includes several applications in order to provide telecommunications services to people in all areas of the country. Potential roles of the Venezuelan Satellite in local and regional development include: strengthening environmental tele-education and telemedicine programs; improving disaster management through short-term development of broad networks to monitor environmental and meteorological features; coordination of emergency responses and humanitarian assistance using data and satellite communications; poverty reduction; and biodiversity conservation – communication networks could also be used to relay information about detected fires within protected areas faster, and to improve surveillance activities within them with in order to reduce illegal hunting, logging, habitat loss and fragmentation. Because the area covered by the satellite goes beyond Venezuela’s borders, its applications could have enormous relevance for human development at the regional level; they could be fundamental tools for bringing sustainable development into Latin America, by building capacity and increasing awareness among decision makers and lay people.  相似文献   
398.
A problem of transverse bending of elastic isotropic parallelogram plates under the action of uniformly distributed load is considered. The plate sides are either pivoted or rigidly restrained. To determine the value of maximum plate deflection, it is proposed that an interpolation technique with respect to form factor be used; and as a geometrical argument, an inner-outer conformal radius ratio can be applied instead of the form factor.  相似文献   
399.
The paper presents an improved technique and the results of strength analysis for the aircraft structural elements with a structural defect like an arbitrary shape delamination.  相似文献   
400.
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   
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