全文获取类型
收费全文 | 5209篇 |
免费 | 13篇 |
国内免费 | 10篇 |
专业分类
航空 | 2206篇 |
航天技术 | 1763篇 |
综合类 | 24篇 |
航天 | 1239篇 |
出版年
2021年 | 48篇 |
2019年 | 31篇 |
2018年 | 167篇 |
2017年 | 123篇 |
2016年 | 134篇 |
2015年 | 52篇 |
2014年 | 146篇 |
2013年 | 196篇 |
2012年 | 162篇 |
2011年 | 225篇 |
2010年 | 178篇 |
2009年 | 282篇 |
2008年 | 294篇 |
2007年 | 163篇 |
2006年 | 122篇 |
2005年 | 153篇 |
2004年 | 142篇 |
2003年 | 176篇 |
2002年 | 119篇 |
2001年 | 191篇 |
2000年 | 78篇 |
1999年 | 105篇 |
1998年 | 114篇 |
1997年 | 99篇 |
1996年 | 95篇 |
1995年 | 156篇 |
1994年 | 128篇 |
1993年 | 62篇 |
1992年 | 88篇 |
1991年 | 24篇 |
1990年 | 39篇 |
1989年 | 83篇 |
1988年 | 40篇 |
1987年 | 34篇 |
1986年 | 41篇 |
1985年 | 134篇 |
1984年 | 115篇 |
1983年 | 85篇 |
1982年 | 100篇 |
1981年 | 138篇 |
1980年 | 38篇 |
1979年 | 24篇 |
1978年 | 43篇 |
1977年 | 25篇 |
1976年 | 19篇 |
1975年 | 37篇 |
1974年 | 26篇 |
1973年 | 21篇 |
1972年 | 28篇 |
1971年 | 19篇 |
排序方式: 共有5232条查询结果,搜索用时 15 毫秒
381.
V. M. Soldatkin A. A. Arkhipov V. A. Olaev A. A. Uglov 《Russian Aeronautics (Iz VUZ)》2012,55(2):184-191
We consider the function, the problems being solved and the construction principles for a starting system of warning the critical regimes for a single-rotor helicopter at parking, taxiing and maneuvering on the ground, takeoff and landing as well as at descending and hovering regimes. The structural-functional scheme and the algorithms of system channel warning are presented. 相似文献
382.
383.
A problem of transverse bending of elastic isotropic parallelogram plates under the action of uniformly distributed load is considered. The plate sides are either pivoted or rigidly restrained. To determine the value of maximum plate deflection, it is proposed that an interpolation technique with respect to form factor be used; and as a geometrical argument, an inner-outer conformal radius ratio can be applied instead of the form factor. 相似文献
384.
We consider in detail the intense Pc5 pulsations of the magnetic field, riometric absorption, and electron fluxes occurred
on the recovery phase of the strong magnetic storm on November 21, 2003. The global structure of these disturbances is studied
using the world network of magnetometers and riometers supplemented by the data of particle detectors onboard the LANL geosynchronous satellites. The local spatial structure is investigated according to data of the regional network of Finnish
vertical riometers and of stations of the IMAGE magnetic network. Though a certain similarity is observed in the frequency
composition and time evolution of the variations of magnetic field and riometric absorption, the local spatial structure of
these oscillations turns out to be different. It is suggested that these variations can be manifestations of oscillatory properties
of two weakly connected systems: the magnetospheric MHD waveguide/resonator and the system cyclotron noise + electrons. The
recorded Pc5 oscillations are, presumably, a result of excitation of the magnetospheric waveguide on the morning and evening
flanks of the magnetosphere. At high velocities of the solar wind this waveguide can appear in a metastable state. Not only
jumps in the solar wind density, but injection of electrons into the magnetosphere as well, can serve as a trigger for the
waveguide excitation. 相似文献
385.
Dynamics of planets around other stars that demonstrate a variety of possible characteristics is of interest from the point
of view of realization of new scenarios of evolution which have not been realized in the Solar System. We consider the rotational
evolution of exoplanets under the action of gravitational perturbations and magnetic disturbances using the methods of quality
analysis and theory of bifurcation of multiparametric differential equations that describe evolution of non-resonant rotation
of a dynamically symmetric planet magnetized along its symmetry axis. We analyze 64 phase portraits describing the evolution
of angular momentum vector L for all possible values of planet parameters. The values of parameters are determined for the case when the direct rotation
of a planet is changed for its retrograde rotation. 相似文献
386.
Nikolai M. Gavrilov Andrej V. Koval Alexander I. Pogoreltsev Elena N. Savenkova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Parameterization of dynamical and thermal effects of stationary orographic gravity waves (OGWs) generated by the Earth’s surface topography is incorporated into a numerical model of general circulation of the middle and upper atmosphere. Responses of atmospheric general circulation and characteristics of planetary waves at altitudes from the troposphere up to the thermosphere to the effects of OGWs propagating from the earth surface are studied. Changes in atmospheric circulation and amplitudes of planetary waves due to variations of OGW generation and propagation in different seasons are considered. It is shown that during solstices the main OGW dynamical and heat effects occur in the middle atmosphere of winter hemispheres, where changes in planetary wave amplitudes due to OGWs may reach up to 50%. During equinoxes OGW effects are distributed more homogeneously between northern and southern hemispheres. 相似文献
387.
S. Sundaresan B. Nageswara Rao 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
This paper presents a mathematical model to simulate ionospheric plasma drifts at equatorial low latitude regions by coupling of E- and F-regions. The governing non-linear differential equations (of elliptic and parabolic nature) are solved numerically through finite-difference schemes and obtained neutral winds and electric fields. The temperature and electron density profiles are generated utilizing MSIS-86 atmospheric model. The continuity equation is employed to obtain night-time E-region density profile using measured ionograms at Trivandrum (India). The computed vertical and zonal plasma drifts are comparable with measured Jacamarca plasma drifts with little variations during noon and evening times. The plasma drifts at Trivandrum (8.5° N, 76.5° E, dip 0.5° N) are compared with those of Jicamarca (12° S, 76.9° W, dip 2° N). Neutral wind simulations of present model agree well with those of horizontal wind model (HWM-93). The post-sunset enhancement and its reversal are also discussed. 相似文献
388.
A model of the main support of the aircraft landing gear is presented and its dynamics is studied using the equations for the distributed motion of a wheel equipped with a brake. Stability of the support wheel rolling motion is analyzed and the brake parameter values which may cause stability loss are found. The results of numerical experiments are presented. 相似文献
389.
I. Antonenko G.R. Osinski M. Battler M. Beauchamp L. Cupelli A. Chanou R. Francis M.M. Mader C. Marion E. McCullough A.E. Pickersgill L.J. Preston B. Shankar T. Unrau D. Veillette 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Remote robotic data provides different information than that obtained from immersion in the field. This significantly affects the geological situational awareness experienced by members of a mission control science team. In order to optimize science return from planetary robotic missions, these limitations must be understood and their effects mitigated to fully leverage the field experience of scientists at mission control. 相似文献
390.
In this paper, we consider some typical values of motion parameters in exceptional situations when approaching to the helicopter critical flight regimes and present a technique for constructing the partial and integral informative functions of hazards at current flight regimes. Also described are the possibilities of their use for solving the problems of warning, informative crew support, and synthesizing the control algorithms to remove helicopter from the exceptional situation occurred. 相似文献