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   6518篇
  免费   7篇
  国内免费   18篇
航空   3486篇
航天技术   1925篇
综合类   23篇
航天   1109篇
  2018年   200篇
  2017年   157篇
  2016年   64篇
  2015年   39篇
  2014年   83篇
  2013年   134篇
  2012年   149篇
  2011年   293篇
  2010年   240篇
  2009年   308篇
  2008年   339篇
  2007年   274篇
  2006年   143篇
  2005年   197篇
  2004年   130篇
  2003年   172篇
  2002年   103篇
  2001年   181篇
  2000年   110篇
  1999年   140篇
  1998年   164篇
  1997年   123篇
  1996年   171篇
  1995年   215篇
  1994年   183篇
  1993年   124篇
  1992年   128篇
  1991年   76篇
  1990年   62篇
  1989年   139篇
  1988年   62篇
  1987年   66篇
  1986年   60篇
  1985年   196篇
  1984年   152篇
  1983年   129篇
  1982年   134篇
  1981年   176篇
  1980年   58篇
  1979年   42篇
  1978年   50篇
  1977年   53篇
  1976年   38篇
  1975年   58篇
  1974年   38篇
  1973年   42篇
  1972年   51篇
  1971年   42篇
  1970年   44篇
  1969年   37篇
排序方式: 共有6543条查询结果,搜索用时 15 毫秒
311.
312.
Space Science Reviews - Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in...  相似文献   
313.
A method of determining the maximum permissible values for diagnostic signs, being an integral part of health and usage monitoring systems (HUMS) of the helicopter transmission units, has been developed based on a probabilistic approach.  相似文献   
314.
Based on an integrated approach, we solve the optimization problem for energy content and weight-dimensional characteristics of the electric servo drive by synthesis of structure and analysis of characteristics for different power supplies. The generalized power supply model, developed for different power supply of drive control systems, is given.  相似文献   
315.
The problem and features of measuring the speed and the direction angle of the wind vector relative to the longitudinal helicopter axis during parking, starting and takeoff-landing modes by onboard means are considered. The construction principles, information processing algorithms and advantages of onboard system for measuring the wind vector parameters based on ion-beacon and aerometric measuring channels, are disclosed.  相似文献   
316.
317.
A methodology of creating a loading imitation model of a single-rotor helicopter with artificial neural network algorithms is considered. Stages of creation, the structure, and an algorithm of searching for an optimal neural networks configuration of loading imitation model are presented.  相似文献   
318.
A weak but statistically reliable dependence of the diurnal activity of oscillations in the ionospheric Alfvén resonator on orientation of the interplanetary magnetic field ahead of the magnetospheric front has been detected based on observations of ULF oscillations at Sayan solar observatory Mondy of the Institute of Solar–Terrestrial Physics. The interpretation of the result has been proposed. The essence is that the electromagnetic fluctuations penetrate into the magnetosphere from the interplanetary environment and influence the ionospheric resonator. The formulation of the problem and the method of solving it are part of the broad program of the experimental and theoretical study of the influence of the interplanetary magnetic field on the oscillation regime of ULF oscillations of the magnetosphere.  相似文献   
319.
By using a Doppler Weather Radar (DWR) at Shriharikota (13.66°N & 80.23°E), an Artificial Neural Network (ANN) based technique is proposed to improve the accuracy of rain intensity estimation. Three spectral moments of a Doppler spectra are utilized as an input data to an ANN. Rain intensity, as measured by the tipping bucket rain gauges around the DWR station, are considered as a target values for the given inputs. Rain intensity as estimated by the developed ANN model is validated by the rain gauges measurements. With the help of a developed technique, reasonable improvement in the estimation of rain intensity is observed. By using the developed technique, root mean square error and bias are reduced in the range of 34–18% and 17–3% respectively, compared to ZR approach.  相似文献   
320.
The requirements for skid landing gear static strength ensuring are examined based on the comparative analysis of the Airworthiness Standards requirements. Probabilistic principle of determining the safety factor of the skid landing gear is presented. The analysis of the experimental data on bench and flight tests is performed for calculating the actual value of this 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