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   7065篇
  免费   19篇
  国内免费   22篇
航空   3186篇
航天技术   2446篇
综合类   22篇
航天   1452篇
  2021年   76篇
  2019年   47篇
  2018年   166篇
  2017年   107篇
  2016年   113篇
  2015年   52篇
  2014年   180篇
  2013年   232篇
  2012年   223篇
  2011年   342篇
  2010年   235篇
  2009年   342篇
  2008年   379篇
  2007年   233篇
  2006年   163篇
  2005年   197篇
  2004年   186篇
  2003年   220篇
  2002年   147篇
  2001年   222篇
  2000年   133篇
  1999年   166篇
  1998年   194篇
  1997年   111篇
  1996年   173篇
  1995年   203篇
  1994年   189篇
  1993年   121篇
  1992年   150篇
  1991年   48篇
  1990年   50篇
  1989年   142篇
  1988年   60篇
  1987年   60篇
  1986年   65篇
  1985年   188篇
  1984年   151篇
  1983年   108篇
  1982年   117篇
  1981年   215篇
  1980年   51篇
  1979年   46篇
  1978年   50篇
  1977年   42篇
  1975年   50篇
  1974年   39篇
  1972年   35篇
  1971年   35篇
  1970年   37篇
  1967年   33篇
排序方式: 共有7106条查询结果,搜索用时 15 毫秒
61.
The influence of geometry and operating conditions of the centrifugal compressor stage on the radial gas force is determined on the basis of the theoretical method and calculation program using experimental boundary conditions.  相似文献   
62.
The application of the low dissipative high-order accurate scheme for numerical solution of the Euler and Navier-Stokes equations in the two-dimensional statement is considered. The scheme of calculating space derivatives is the seven-point central-difference approximation of the fourth order with the coefficients optimized to reduce the dispersion errors. The optimized six-step Runge-Kutta method is used for evaluating the time derivatives. By means of filtration, spurious pulsations are suppressed and shocks are processed. The results of verifying the calculation scheme realized on the stationary problem of flow around the model turbine blades are presented.  相似文献   
63.
A problem of modeling the incompressible viscous flow between two disks taking into account the rotation of one of them is considered. We study the effect of the disk angular velocity (flow regimes) in the interdisk spacing, finiteness (infiniteness) of disk radiuses, calculation region configuration as well as distances between disks on the flow characteristics, particularly, on the resistance moment coefficient. Numerical simulation is performed with the aid of Maple and ANSYS Fluent software.  相似文献   
64.
A technique for calculating the energy parameters of shock waves at electrical discharge in water is presented for the transition region of discharge channel expansion using as the base the predetermined characteristics of discharge circuit. The technique is based on the solution of energy transport equation that is similar in form to that of radiative transfer. The validity of the presented approach was experimentally verified.  相似文献   
65.
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   
66.
Aerodynamic characteristics of two-dimensional smart flap under the ground effect have been assessed by a numerical simulation. In this process, a pressure-based implicit procedure to solve Navier–Stokes equations on a nonorthogonal mesh with collocated finite volume formulation is used. The boundedness criteria for this procedure are determined from the Normalized Variable Diagram (NVD) scheme. The procedure incorporates the kε eddy–viscosity turbulence model. Cantilever beam with uniformly varying load with roller support at the free end is considered for the configuration of the smart flap. The method is first validated against experimental data. Then, the algorithm is applied for turbulent aerodynamic flows around airfoil with smart and conventional flaps for different attack angle, flap angle and ground clearance where the results of two flaps are compared. The comparisons show that the quality of the solution is considerable.  相似文献   
67.
The results of research in a process of a probe rocket berthing to an asteroid are presented. Control laws were obtained as solutions of three problems, namely berthing considering transient processes in a rocket engine, fastest berthing with regard to fuel consumption and berthing in a scheduled time considering fuel consumption. A program trajectory obtained at solving of the first problem is suitable for mathematical modeling of berthing with the feedback control law and stabilization of angular motion. The solutions of the problems are reduced to simple formulas for controlling parameters calculation in the corresponding structures of control laws. The results can be applied in designing promising space vehicles intended for berthing to other space objects.  相似文献   
68.
69.
Using both analytical and numerical models of the collisionless anisotropic current sheet generated by the impinging flows of transient ions, we have studied the self-consistent solutions taking the plasma trapped in the sheet into account. It is demonstrated that there exists a limited window in the space of system parameters where self-consistent solutions can exist. When the density of the quasi-trapped plasma is sufficiently large, a redistribution of the total current can be a cause of the sheet decay, when the local current of the trapped particles compensate (totally or in part) the main current in the center and at the edges of the sheet, while the total current generated by ions on the trapped trajectories vanishes.  相似文献   
70.
The motion of a variable-mass spacecraft is considered in the powered section of a descending trajectory. Approximate analytical solutions are obtained for the angles of spatial orientation of the spacecraft, which allows one to analyze the nutation motion and to develop recommendations on the spacecraft’s mass configuration, providing the smallest possible deviations of the longitudinal axis and thrust vector from specified directions. The errors of stabilization of the spacecraft’s longitudinal axis are calculated by means of numerical integration of complete models and using the obtained analytical solutions, the results being in good agreement.  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