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   8149篇
  免费   13篇
  国内免费   17篇
航空   4001篇
航天技术   2702篇
综合类   194篇
航天   1282篇
  2021年   67篇
  2018年   152篇
  2017年   95篇
  2016年   98篇
  2014年   174篇
  2013年   203篇
  2012年   221篇
  2011年   306篇
  2010年   196篇
  2009年   353篇
  2008年   397篇
  2007年   208篇
  2006年   170篇
  2005年   202篇
  2004年   195篇
  2003年   250篇
  2002年   244篇
  2001年   317篇
  2000年   145篇
  1999年   192篇
  1998年   238篇
  1997年   166篇
  1996年   192篇
  1995年   252篇
  1994年   240篇
  1993年   140篇
  1992年   185篇
  1991年   92篇
  1990年   84篇
  1989年   191篇
  1988年   83篇
  1987年   93篇
  1986年   80篇
  1985年   220篇
  1984年   185篇
  1983年   159篇
  1982年   181篇
  1981年   240篇
  1980年   89篇
  1979年   72篇
  1978年   79篇
  1977年   52篇
  1976年   60篇
  1975年   65篇
  1974年   61篇
  1973年   46篇
  1972年   67篇
  1971年   64篇
  1970年   44篇
  1969年   48篇
排序方式: 共有8179条查询结果,搜索用时 407 毫秒
391.
An algorithm of analyzing the design parameters for a thin-walled wing from composite material based on the efficient distribution of structural material between load-carrying elements is described. We consider the problems of convergence acceleration for the iteration design analysis. Also presented are the examples of determining the design parameters for a superlight aircraft wing and the rational parameters of the filler in the form of a three-dimensional rod structure.  相似文献   
392.
We considered the influence of temperature on the nitric oxide emission under combustion of the near-stoichiometric mixtures with and without water feed. We revealed the advantage of the method of fuel-water-air mixture combustion over that of the leaned mixture combustion.  相似文献   
393.
We consider the peculiarities of application for the cabin indicating systems of secondary information display, formulate and systematize the compositional and technical requirements for display systems and their elements. The tendencies and lines in the development of head-up displays for avionics and autobasing complexes were determined. The technique of calculating optics of such display systems with the use of electronic distortion compensation is presented.  相似文献   
394.
The paper describes a device and a technique of forming the information processing algorithms used in the integrated acoustic monitoring system for jet fuel tanks, intended for monitoring the level, density and mass of liquid products.  相似文献   
395.
The decay phase of the sunspot cycle 23 exhibited two unusual features. First, it lasted too long. Second, the interplanetary magnetic field intensity at earth orbit reached the lowest value since in situ measurements in space began in October 1963. These physical anomalies significantly altered the early forecasts for the sunspot activity parameters for cycle 24, made by several colleagues. We note that there was a significant change in the solar behavior during cycle 22. We discuss the observed trends and their effect on our empirical solar activity forecast technique, leading to our prediction for cycle 24 parameters; cycle 24 will be only half as active as cycle 23, reaching its peak in May 2013. We speculate on the possible implications of this outcome on future earth climate change and the ensuing socio-economic consequences.  相似文献   
396.
The paper adduces the relators for algebraic operations on graphs using the numeric codes of the graphs. The special algebra of codes has been devised with consideration of the principles of graph transformation. This paper demonstrates the relevance of numeric coding of graphs for solving the problems of enumeration, systematization, and compact representation of the information about the structural and functional characteristics of the systems of flow distribution and conversion of rocket and space technology and for conducting the modeling transformations of given systems in the course of the structural and functional studies as well.  相似文献   
397.
Numerous discoveries of asteroids unknown earlier led to a multiple increase in the number of information on small bodies of the Solar System. Huge volumes of information accumulated and obtained at observations of objects approaching the Earth’s orbit require storing and prompt processing, presenting more and more possibilities for studying distributions of small bodies of the Solar System and ways of their evolution. That is why development of information systems which will contain large volumes of data on small bodies of the Solar System and facilities for processing these data is actual and promising direction of activity.  相似文献   
398.
The Relativistic Proton Spectrometer (RPS) on the Radiation Belt Storm Probes spacecraft is a particle spectrometer designed to measure the flux, angular distribution, and energy spectrum of protons from ~60 MeV to ~2000 MeV. RPS will investigate decades-old questions about the inner Van Allen belt proton environment: a nearby region of space that is relatively unexplored because of the hazards of spacecraft operation there and the difficulties in obtaining accurate proton measurements in an intense penetrating background. RPS is designed to provide the accuracy needed to answer questions about the sources and losses of the inner belt protons and to obtain the measurements required for the next-generation models of trapped protons in the magnetosphere. In addition to detailed information for individual protons, RPS features count rates at a 1-second timescale, internal radiation dosimetry, and information about electrostatic discharge events on the RBSP spacecraft that together will provide new information about space environmental hazards in the Earth’s magnetosphere.  相似文献   
399.
This paper summarizes the modeling, simulation, and testing work related to the development of technology to investigate the potential that shape memory actuation has to provide mechanically simple and affordable solutions for delivering assets to a surface and for sample capture and possible return to Earth. We investigate the structural dynamics and controllability aspects of an adaptive beam carrying an end-effector which, by changing material equilibrium phases, is able to actively decouple the end-effector dynamics from the spacecraft dynamics during the surface contact phase. Asset delivery and sample capture and return are at the heart of several emerging potential missions to small bodies, such as asteroids and comets, and to the surface of large bodies, such as Titan.  相似文献   
400.
This paper presents a composite model of a flight simulator. This simulator is intended for carrying out investigative tests of flight dynamics imitation models of a hingeless rotor helicopter. A schematic diagram, composition and operation channels of the flight simulator software are presented. A possibility of applying the control lag is estimated.  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