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   18834篇
  免费   37篇
  国内免费   123篇
航空   10181篇
航天技术   5525篇
综合类   241篇
航天   3047篇
  2021年   154篇
  2018年   261篇
  2016年   175篇
  2014年   434篇
  2013年   514篇
  2012年   436篇
  2011年   642篇
  2010年   474篇
  2009年   830篇
  2008年   852篇
  2007年   433篇
  2006年   431篇
  2005年   416篇
  2004年   460篇
  2003年   533篇
  2002年   487篇
  2001年   600篇
  2000年   364篇
  1999年   461篇
  1998年   452篇
  1997年   329篇
  1996年   402篇
  1995年   472篇
  1994年   454篇
  1993年   364篇
  1992年   336篇
  1991年   249篇
  1990年   242篇
  1989年   412篇
  1988年   208篇
  1987年   239篇
  1986年   240篇
  1985年   641篇
  1984年   521篇
  1983年   409篇
  1982年   490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   189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
  1967年   142篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
891.
892.
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   
893.
894.
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   
895.
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   
896.
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   
897.
898.
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 Using published and unpublished information, this report describes the potential role of the Venesat-1 satellite in promoting development in Venezuela and Latin America.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   
899.
Abstract

In this paper we propose a spatial ontology for reasoning about holes, rigid objects and a string, taking a classical puzzle as a motivating example. In this ontology the domain is composed of spatial regions whereby a theory about holes is defined over a mereotopological basis. Within this theory we define a data structure, named chain, that facilitates a clear and efficient representation of the puzzle states and its solution.  相似文献   
900.
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   
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