全文获取类型
收费全文 | 5288篇 |
免费 | 11篇 |
国内免费 | 14篇 |
专业分类
航空 | 2343篇 |
航天技术 | 1756篇 |
综合类 | 22篇 |
航天 | 1192篇 |
出版年
2021年 | 42篇 |
2019年 | 33篇 |
2018年 | 209篇 |
2017年 | 160篇 |
2016年 | 103篇 |
2015年 | 47篇 |
2014年 | 120篇 |
2013年 | 135篇 |
2012年 | 147篇 |
2011年 | 269篇 |
2010年 | 217篇 |
2009年 | 301篇 |
2008年 | 353篇 |
2007年 | 234篇 |
2006年 | 117篇 |
2005年 | 156篇 |
2004年 | 139篇 |
2003年 | 161篇 |
2002年 | 109篇 |
2001年 | 165篇 |
2000年 | 84篇 |
1999年 | 94篇 |
1998年 | 110篇 |
1997年 | 82篇 |
1996年 | 103篇 |
1995年 | 120篇 |
1994年 | 118篇 |
1993年 | 70篇 |
1992年 | 100篇 |
1991年 | 44篇 |
1990年 | 41篇 |
1989年 | 99篇 |
1988年 | 36篇 |
1987年 | 44篇 |
1986年 | 45篇 |
1985年 | 151篇 |
1984年 | 95篇 |
1983年 | 83篇 |
1982年 | 101篇 |
1981年 | 138篇 |
1980年 | 43篇 |
1979年 | 44篇 |
1978年 | 32篇 |
1977年 | 30篇 |
1976年 | 21篇 |
1975年 | 24篇 |
1974年 | 28篇 |
1973年 | 23篇 |
1972年 | 16篇 |
1970年 | 15篇 |
排序方式: 共有5313条查询结果,搜索用时 171 毫秒
991.
E. L. Akim R. N. Arkhangelsky Yu. K. Zaiko S. M. Lavrenov A. L. Poroshin E. G. Ruzsky V. A. Stepaniants A. G. Tuchin D. A. Tuchin V. P. Fedotov V. S. Yaroshevsky 《Cosmic Research》2009,47(4):299-309
Basic concepts and algorithms laid as foundations of the scheme of landing on the Martian moon Phobos (developed for the Phobos-Grunt project) are presented. The conditions ensuring the landing are discussed. Algorithms of onboard navigation and control are described. The equations of spacecraft motion with respect to Phobos are considered, as well as their use for correction of the spacecraft motion. The algorithm of estimation of the spacecraft’s state vector using measurements with a laser altimeter and Doppler meter of velocity and distance is presented. A system for modeling the landing with a firmware complex including a prototype of the onboard computer is described. 相似文献
992.
O. M. Belotserkovskii I. V. Mingalev V. S. Mingalev O. V. Mingalev A. M. Oparin V. M. Chechetkin 《Cosmic Research》2009,47(6):466-479
The paper is devoted to studying the mechanisms of formation of cyclones in the Earth’s atmosphere with the help of numerical
modeling using the complete system of gas-dynamic equations. The results of modeling have shown that cyclones can appear in
horizontal stratified shear flows of warm and wet air masses with horizontal direction of gradients of the wind velocity components
as a result of small disturbances of pressure which can be produced by Rossby waves. 相似文献
993.
The results of reconstruction of uncontrolled attitude motion of the Foton M-2 satellite using measurements with the accelerometer TAS-3 are presented. The attitude motion of this satellite has been previously
determined by the measurement data of the Earth’s magnetic field and the angular velocity. The TAS-3 data for this purpose
are used for the first time. These data contain a well-pronounced additional component which made impossible their direct
employment for the reconstruction of the attitude motion and whose origin was unknown several years ago. Later it has become
known that the additional component is caused by the influence of the Earth’s magnetic field. The disclosure of this fact
allowed us to take into account a necessary correction in processing of TAS-3 data and to use them for the reconstruction
of the attitude motion of Foton M-2. Here, a modified method of processing TAS-3 data is described, as well as results of its testing and employing. The testing
consisted in the direct comparison of the motion reconstructed by the new method with the motion constructed by the magnetic
measurements. The new method allowed us to find the actual motion of Foton M-2 in the period June 9, 2005–June 14, 2005, when no magnetic measurements were carried out. 相似文献
994.
We study the influence of additive and parametric slowly varying harmonic (at the Chandler frequency and doubled frequency) and stochastic Gaussian broadband perturbations on mathematical expectations, variances, and covariations of oscillations of the Earth’s pole. The influence of perturbations on both regular and irregular stochastic oscillations is considered in detail. Results of numerical experiments are presented. The developed models and software are included into information resources on the fundamental problem “Statistical dynamics of the Earth’s rotation” of Russian Academy of Sciences. 相似文献
995.
996.
Corey S. Jamieson Agnes H.H. Chang Ralf I. Kaiser 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
Mixtures of molecular nitrogen and methane have been identified in numerous outer Solar Systemices including the icy surfaces of Pluto and Triton. We have simulated the interaction of ionizing radiation in the Solar System by carrying out a radiolysis experiment on a methane – molecular nitrogen ice mixture with energetic electrons. We have identified the hydrogen cyanide molecule as the most prominent carbon–nitrogen-bearing reaction product formed. Upon warming the irradiated sample, we followed for the first time the kinetics and temporal evolution of the underlying acid–base chemistry which resulted in the formation of the cyanide ion from hydrogen cyanide. On the surfaces of Triton and Pluto and on comets in Oort’s cloud this sort of complex chemistry is likely to occur. In particular, hydrogen cyanide can be produced in low temperature environments (Oort cloud comets) and may be converted into cyanide ions once the comets reach the warmer regions of the Solar System. 相似文献
997.
A correlative analysis has been made between cosmic ray intensity and solar activity (sunspot numbers) during high amplitude days for the period 1991–1995. The high amplitude days with the time of maximum in the corotational/azimuthal direction do not indicate any significant correlation with solar activity. The diurnal amplitude significantly remains constant and high (0.5%) during the entire period. Our observations suggest that the direction of the anisotropy of high amplitude anisotropic wave train events contribute significantly to the short-term behavior of the cosmic ray diurnal anisotropy. The correlation coefficient is found to remain positive during solar activity maximum for all the high amplitude anisotropic wave train events. 相似文献
998.
Energetic solar proton events within the energy interval 1–48 MeV at the stage of their decay are considered over the period of 1974–2001. The dependence of the characteristic decay time on the proton energy in the assumed power-law representation τ(E) =E ?n is analyzed for the events with an exponential decay form. The dependence of n on the heliolongitude of the flare (the particles source on the Sun) is studied. 相似文献
999.
Yu. P. Ulybyshev 《Cosmic Research》2008,46(2):133-145
Approximate numerical methods of optimization of spacecraft rendezvous trajectories are presented that make use of interior point algorithms for problems of linear programming of high dimensionality (tens to hundreds of thousands of variables). The basis of the methods is discretization of a trajectory into small segments in which maneuvers are allowed to be executed; for all segments sets of pseudo-impulses are introduced that determine the possible directions of the spacecraft thrust vector. The terminal conditions are presented in the form of a linear matrix equation. A matrix inequality for the sums of characteristic velocities of pseudo-impulses on each segment is used to make a transformation to the linear programming form. Spacecraft rendezvous trajectories are considered in the neighborhood of circular orbits with the use of multi-mode propulsion systems (including those with low thrust) and existence of boundary conditions at interior points and constraints on the time of operation of the propulsion system at separate segments of the trajectory. 相似文献
1000.
The relationship between proton aurora and geomagnetic pulsations Pc1, which are an indicator of development of ion-cyclotron instability in the equatorial magnetosphere, are studied on the basis of the observations of proton aurora from the IMAGE satellite, observations of particle fluxes onboard the low-orbiting NOAA satellites, and geomagnetic pulsation observations at the Lovozero observatory. A conclusion is drawn that the subauroral spots in the proton emission projected into the magnetosphere near the plasmapause are two-dimensional images at the ionospheric “screen” of the region of intense scattering of energetic protons into the loss cone at the development of an ion-cyclotron instability. 相似文献