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   3471篇
  免费   4篇
  国内免费   6篇
航空   1766篇
航天技术   913篇
综合类   9篇
航天   793篇
  2021年   18篇
  2019年   16篇
  2018年   180篇
  2017年   149篇
  2016年   73篇
  2015年   37篇
  2014年   56篇
  2013年   90篇
  2012年   91篇
  2011年   204篇
  2010年   181篇
  2009年   231篇
  2008年   214篇
  2007年   182篇
  2006年   64篇
  2005年   113篇
  2004年   77篇
  2003年   85篇
  2002年   43篇
  2001年   94篇
  2000年   48篇
  1999年   65篇
  1998年   69篇
  1997年   66篇
  1996年   64篇
  1995年   87篇
  1994年   86篇
  1993年   46篇
  1992年   51篇
  1991年   15篇
  1990年   24篇
  1989年   51篇
  1988年   32篇
  1987年   20篇
  1986年   28篇
  1985年   73篇
  1984年   70篇
  1983年   42篇
  1982年   69篇
  1981年   67篇
  1980年   17篇
  1979年   10篇
  1978年   31篇
  1977年   12篇
  1975年   24篇
  1974年   16篇
  1973年   16篇
  1972年   16篇
  1970年   9篇
  1969年   12篇
排序方式: 共有3481条查询结果,搜索用时 15 毫秒
881.
Alignment charts that make it possible to select a standard size of inert heatexchanger structures with specified output characteristics and a developed scheme of the low-temperature aerosol generator are presented.  相似文献   
882.
An effect of the Coriolis forces on the process of gas expansion in the turbine stage is considered. Expressions for efficiency with regard for the radial flow passage are derived. The calculation results and statistical data on the geometric parameters of diagonal stages are presented.  相似文献   
883.
In the framework of a plane problem of elasticity theory in strength analysis based on the finite element method in the hybrid formulation, we suggest that the approximation of displacements and stresses be used as magnitudes of vector and tensor fields, respectively. The quadrilateral finite element, the displacements and stresses of which are accepted as nodal unknowns is proposed. The mixed Reissner functional is applied to form a finite element deformation matrix.  相似文献   
884.
The unsteady aerodynamic loads (pressure increment and generalized forces) acting on a deformable thin airfoil section are determined for its arbitrary motion in the incompressible flow with transverse gusts. In this case, the exact Küssner solution in series is used for harmonic oscillation of an airfoil, in which the Theodorsen function is approximated by a sum of fractional functions with poles. In the time domain, these functions are replaced by the unknown functions that satisfy the one-type ordinary first order differential equations. The equations obtained are combined with the differential equations of the airfoil motion in the generalized coordinates and are used for analyzing the aeroelastic system stability and calculating its dynamic response to gust loads.  相似文献   
885.
An approach and algorithms are proposed that make it possible to take into account an effect of magnetic interferences introduced by a mobile object, variation of its inclination angles and, hence, to improve precision of the magneto-inertial horizon-compass operation.  相似文献   
886.
The results of modeling the thermal deformations of a space radio telescope’s reflecting surface are presented in the paper. Calculations were performed for the versions of the most unfavorable telescope illumination by the Sun.  相似文献   
887.
The different types of the data recorded in the experiment of the regular balloon monitoring of cosmic rays (carried out since 1957 by Lebedev Physical Institute, Moscow, Russia, in several locations) are described. So called detailed information (the form of each pulse detected by the ground-based receiver) recorded during the last 12 years is discussed in more details. The use of these data both for getting and correcting the standard results of the experiment and for obtaining some additional information on the cosmic rays in the Earth’s atmosphere is considered.  相似文献   
888.
In the past few year several theories have been presented for describing cosmic ray scattering across the mean magnetic field. It is the purpose of the present article to discuss the relation between these different theories in order to improve our understanding of cosmic ray perpendicular scattering and to explore the parameter regimes for which these different theories are valid.  相似文献   
889.
This paper presents the design of a missile autopilot over its flight envelop using quasi-linear parameter-varying polynomial eigenstructure assignment (PEA). The paper describes the extension of PEA to parameter-varying systems using a nonlinear missile model developed by Horton as an example. The autopilot is designed for a single-plane lateral acceleration control and a 5 degree of freedom (DOF) autopilot is also designed. Both lateral acceleration and augmented lateral acceleration outputs are considered. The lateral acceleration autopilot has nonminimum phase characteristics, and it is shown that the quasi-linear parameter-varying PEA approach can handle nonminimum phase systems unlike classic dynamic inversion techniques. Simulation results are presented over fast variations in Mach number and show that the design is robust.  相似文献   
890.
Based on the archive OMNI data for the period 1976–2000 an analysis has been made of 798 geomagnetic storms with D st < −50 nT and their interplanetary sources-large-scale types of the solar wind: CIR (145 magnetic storms), Sheath (96), magnetic clouds MC (62), and Ejecta (161). The remaining 334 magnetic storms have no well-defined sources. For the analysis, we applied the double method of superposed epoch analysis in which the instants of the magnetic storm beginning and minimum of D st index are taken as reference times. The well-known fact that, independent of the interplanetary source type, the magnetic storm begins in 1–2 h after a southward turn of the IMF (B z < 0) and both the end of the main phase of a storm and the beginning of its recovery phase are observed in 1–2 h after disappearance of the southward component of the IMF is confirmed. Also confirmed is the result obtained previously that the most efficient generation of magnetic storms is observed for Sheath before MC. On the average parameters B z and E y slightly vary between the beginning and end of the main phase of storms (minimum of D st and D st * indices), while D st and D st * indices decrease monotonically proportionally to integral of B z and E y over time. Such a behavior of the indices indicates that the used double method of superposed epoch analysis can be successfully applied in order to study dynamics of the parameters on the main phase of magnetic storms having different duration.  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