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   3934篇
  免费   3篇
  国内免费   20篇
航空   2060篇
航天技术   1128篇
综合类   14篇
航天   755篇
  2018年   171篇
  2017年   148篇
  2016年   55篇
  2015年   30篇
  2014年   57篇
  2013年   69篇
  2012年   95篇
  2011年   223篇
  2010年   190篇
  2009年   241篇
  2008年   257篇
  2007年   205篇
  2006年   78篇
  2005年   129篇
  2004年   97篇
  2003年   90篇
  2002年   53篇
  2001年   85篇
  2000年   53篇
  1999年   71篇
  1998年   82篇
  1997年   52篇
  1996年   65篇
  1995年   81篇
  1994年   84篇
  1993年   56篇
  1992年   66篇
  1991年   31篇
  1990年   33篇
  1989年   75篇
  1988年   30篇
  1987年   29篇
  1986年   31篇
  1985年   121篇
  1984年   73篇
  1983年   57篇
  1982年   63篇
  1981年   108篇
  1980年   35篇
  1979年   27篇
  1978年   27篇
  1977年   30篇
  1976年   23篇
  1975年   32篇
  1974年   20篇
  1973年   26篇
  1972年   25篇
  1971年   18篇
  1970年   27篇
  1969年   27篇
排序方式: 共有3957条查询结果,搜索用时 15 毫秒
961.
We reveal a functional diagram, design features of a receiver electrode system, a principle of forming primary informative signals, a technique for synthesizing angular characteristics and estimating indicated errors, channel realization and algorithms of forming output signals of an ionmarking aerodynamic angle and airspeed sensor with logometric informative signals and interpolation processing scheme.  相似文献   
962.
Using the results of numerical modeling of nonstationary gas hydrodynamic working processes in the gas conduit variable section channel when removing and cooling hot gases of different purpose technical plants, an engineering technique has been developed to provide the gas conduit operation under limitations on the flow temperature in the outlet plant section. A multiparametric area of permissible gas conduit operation connecting the characteristics of technical plants, gas conduit and water feeding system is presented.  相似文献   
963.
Electric currents permeate space plasmas and often have a significant component along the magnetic field to form magnetic flux ropes. A larger spatial perspective of these structures than from the direct observation along the satellite path is crucial in visualizing their role in plasma dynamics. For magnetic flux ropes that are approximately two-dimensional equilibrium structures on a certain plane, Grad-Shafranov reconstruction technique, developed by Bengt Sonnerup and his colleagues (see Sonnerup et al. in J. Geophys. Res. 111:A09204, 2006), can be used to reveal two-dimensional maps of associated plasma and field parameters. This review gives a brief account of the technique and its application to magnetic flux ropes near the Earth’s magnetopause, in the solar wind, and in the magnetotail. From this brief survey, the ranges of the total field-aligned current and the total magnetic flux content for these magnetic flux ropes are assessed. The total field-aligned current is found to range from ∼0.14 to ∼9.7×104 MA, a range of nearly six orders of magnitude. The total magnetic flux content is found to range from ∼0.25 to ∼2.3×106 MWb, a range of nearly seven orders of magnitude. To the best of our knowledge, this review reports the largest range of both the total field-aligned current and the total magnetic flux content for magnetic flux ropes in space plasmas.  相似文献   
964.
Negative effect of cosmic ray particles is a serious danger for astronauts and onboard equipment. When planning interplanetary flights it becomes one of the main obstacles. The aim of this work is to analyze currently available methods of protecting spacecraft against cosmic rays using magnetic fields and to choose the most effective method. Three variants of protection systems were considered, two of which had been described in scientific literature: with azimuth and axial magnetic filed. The third, more general method (with helical magnetic field) is suggested here for the first time. The first two variants are extreme special cases of the third one. The exact solution is obtained for the problem of motion of a charged relativistic particle in the helical magnetic field, and a criterion of particle reflection is determined. A comparative analysis of reflection characteristics of the chosen systems has been performed, and the conclusion about the optimal configuration of the magnetic protection is drawn.  相似文献   
965.
The investigation of stability and precision of the previously proposed implicit scheme of direct integration for the finite element equations of motion is presented. The scheme parameter values that ensure its unconditional stability in the nonlinear problems are determined and comparison with existing procedures is given.  相似文献   
966.
A mathematical model of motion for a string of liferafts being water dropped is presented under the assumption of a plane system motion. An example of calculations is given.  相似文献   
967.
Using formalism of the queueing theory, we propose two-objective models for optimizing the number of unmanned aerial vehicles (UAV) designed for remote monitoring (reconnaissance) of certain regions. A model that takes into account the UAV failure in performing a flight mission is considered. The numerical method and examples of solving problems stated are presented.  相似文献   
968.
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   
969.
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   
970.
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   
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