全文获取类型
收费全文 | 6030篇 |
免费 | 8篇 |
国内免费 | 24篇 |
专业分类
航空 | 2670篇 |
航天技术 | 1956篇 |
综合类 | 28篇 |
航天 | 1408篇 |
出版年
2021年 | 47篇 |
2019年 | 33篇 |
2018年 | 213篇 |
2017年 | 168篇 |
2016年 | 136篇 |
2015年 | 52篇 |
2014年 | 151篇 |
2013年 | 180篇 |
2012年 | 178篇 |
2011年 | 283篇 |
2010年 | 240篇 |
2009年 | 336篇 |
2008年 | 359篇 |
2007年 | 240篇 |
2006年 | 129篇 |
2005年 | 179篇 |
2004年 | 169篇 |
2003年 | 176篇 |
2002年 | 127篇 |
2001年 | 184篇 |
2000年 | 84篇 |
1999年 | 113篇 |
1998年 | 134篇 |
1997年 | 86篇 |
1996年 | 100篇 |
1995年 | 149篇 |
1994年 | 131篇 |
1993年 | 81篇 |
1992年 | 100篇 |
1991年 | 40篇 |
1990年 | 47篇 |
1989年 | 106篇 |
1988年 | 36篇 |
1987年 | 43篇 |
1986年 | 43篇 |
1985年 | 176篇 |
1984年 | 120篇 |
1983年 | 98篇 |
1982年 | 97篇 |
1981年 | 177篇 |
1980年 | 55篇 |
1979年 | 39篇 |
1978年 | 37篇 |
1977年 | 42篇 |
1976年 | 31篇 |
1975年 | 43篇 |
1973年 | 29篇 |
1972年 | 31篇 |
1970年 | 29篇 |
1969年 | 31篇 |
排序方式: 共有6062条查询结果,搜索用时 31 毫秒
261.
262.
263.
D. V. Nedel’ko 《Russian Aeronautics (Iz VUZ)》2016,59(3):297-302
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
264.
R.V. Semenyshyn A.N. VeklichI.L. Babich V.F. Boretskij 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
Plasma of the free burning electric arc between Ag–SnO2–ZnO composite electrodes as well as brass electrodes were investigated. The plasma temperature distributions were obtained by Boltzmann plot method involving Cu I, Ag I or Zn I spectral line emissions. The electron density distributions were obtained from the width and from absolute intensity of spectral lines. The laser absorption spectroscopy was used for measurement of copper atom concentration in plasma. Plasma equilibrium composition was calculated using two independent groups of experimental values (temperature and copper atom concentration, temperature and electron density). It was found that plasma of the free burning electric arc between brass electrodes is in local thermodynamical equilibrium. The experimental verification of the spectroscopic data of Zn I spectral lines was carried out. 相似文献
265.
A.K. Sharma O.B. Gurav Anindya Bose H.P. Gaikwad G.A. Chavan Atanu Santra S.S. Kamble R.S. Vhatkar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3131-3138
Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies. 相似文献
266.
A.D. Danilov A.V. Konstantinova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(1):359-370
Long-term changes in the E-layer critical frequency, foE, at three stations of the European region (Juliusruh, Slough and Rome) and also at Moscow and Wakkanai stations are analyzed by the method developed by the authors and described in detail in the previous papers. It is found that Juliusruh and Slough stations demonstrate a well-pronounced change in foE (a trend) during two previous decades. At the same time, the same features of the behavior of the aforementioned trend k(foE) are obtained. The trend is positive and negative in the morning and evening hours, respectively. Similar diurnal behavior of k(foE) is found also for Moscow station but with lower absolute values of the trends. A well-pronounced seasonal behavior of k(foE) is detected at Juliusruh and Slough: the trend is minimal and maximal in the summer period and at the end of fall—beginning of winter, respectively. The maximal amplitude in the morning hours reaches +0.04?MHz per year, whereas the minimal amplitude in evening hours is ?0.06?MHz per year. No systematic changes exceeding by the magnitude 0.01?MHz per year are found for Rome and Wakkanai stations. It is assumed that the observed trends are related to changes (trends) in the meridional wind bringing NO molecules from the auroral oval to lower latitudes. 相似文献
267.
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
268.
E. O. Ariskin A. V. Nikitin V. V. Soldatkin V. M. Soldatkin 《Russian Aeronautics (Iz VUZ)》2015,58(4):454-460
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
269.
We consider the stability of stationary motions of a model of a spacecraft as a system of coaxial bodies with small asymmetry caused by the shift of the axes of dynamic symmetry of bodies relative to the axis of rotation. We determine the stationary motions of the system; their stability is studied with respect to both the projections of angular velocity and the position of the axis of rotation. The sufficient conditions for the stability of these stationary motions are obtained by constructing a Lyapunov function, and the necessary conditions are obtained by analyzing the corresponding linearized equations of perturbed motion. 相似文献
270.