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   19137篇
  免费   40篇
  国内免费   125篇
航空   10223篇
航天技术   5696篇
综合类   251篇
航天   3132篇
  2021年   155篇
  2018年   267篇
  2017年   151篇
  2016年   175篇
  2014年   435篇
  2013年   516篇
  2012年   440篇
  2011年   647篇
  2010年   478篇
  2009年   836篇
  2008年   860篇
  2007年   446篇
  2006年   435篇
  2005年   428篇
  2004年   467篇
  2003年   558篇
  2002年   499篇
  2001年   620篇
  2000年   374篇
  1999年   466篇
  1998年   474篇
  1997年   338篇
  1996年   416篇
  1995年   486篇
  1994年   480篇
  1993年   364篇
  1992年   356篇
  1991年   252篇
  1990年   243篇
  1989年   417篇
  1988年   212篇
  1987年   248篇
  1986年   246篇
  1985年   643篇
  1984年   523篇
  1983年   417篇
  1982年   493篇
  1981年   620篇
  1980年   246篇
  1979年   189篇
  1978年   189篇
  1977年   146篇
  1976年   156篇
  1975年   190篇
  1974年   181篇
  1973年   161篇
  1972年   188篇
  1971年   148篇
  1970年   143篇
  1969年   147篇
排序方式: 共有10000条查询结果,搜索用时 199 毫秒
911.
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   
912.
Space graspers are complex systems, composed by robotic arms placed on an orbiting platform. In order to fulfil the manoeuvres’ requirements, it is necessary to properly model all the forces acting on the space robot. A fully nonlinear model is used to describe the dynamics, based on a multibody approach. The model includes the orbital motion, the gravity gradient, the aerodynamic effects, as well as the flexibility of the links. The present paper aims to design, thanks to nonlinear optimization algorithms, a class of manoeuvres that, given the same target to be grasped, are characterized by different mission objectives. The grasping mission can be performed with the objective to minimize the power consumption. Collision avoidance constraints can be also added when the target is equipped with solar panels or other appendices. In some cases, large elastic displacements should be expected, possibly leading to an inaccurate positioning of the end-effector. Therefore, different design strategies can require that the manoeuvre is accomplished with minimum vibrations’ amplitude at the end-effector. Performance of the different strategies is analyzed in terms of control effort, trajectory errors, and flexible response of the manipulator.  相似文献   
913.
914.
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   
915.
916.
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   
917.
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   
918.
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   
919.
920.
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   
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