全文获取类型
收费全文 | 9652篇 |
免费 | 23篇 |
国内免费 | 26篇 |
专业分类
航空 | 4496篇 |
航天技术 | 3260篇 |
综合类 | 32篇 |
航天 | 1913篇 |
出版年
2021年 | 96篇 |
2019年 | 58篇 |
2018年 | 248篇 |
2017年 | 172篇 |
2016年 | 147篇 |
2015年 | 71篇 |
2014年 | 237篇 |
2013年 | 277篇 |
2012年 | 289篇 |
2011年 | 461篇 |
2010年 | 327篇 |
2009年 | 488篇 |
2008年 | 524篇 |
2007年 | 323篇 |
2006年 | 224篇 |
2005年 | 276篇 |
2004年 | 238篇 |
2003年 | 298篇 |
2002年 | 194篇 |
2001年 | 306篇 |
2000年 | 170篇 |
1999年 | 205篇 |
1998年 | 256篇 |
1997年 | 163篇 |
1996年 | 220篇 |
1995年 | 270篇 |
1994年 | 259篇 |
1993年 | 166篇 |
1992年 | 207篇 |
1991年 | 88篇 |
1990年 | 75篇 |
1989年 | 195篇 |
1988年 | 88篇 |
1987年 | 84篇 |
1986年 | 91篇 |
1985年 | 241篇 |
1984年 | 189篇 |
1983年 | 166篇 |
1982年 | 179篇 |
1981年 | 282篇 |
1980年 | 80篇 |
1979年 | 73篇 |
1978年 | 70篇 |
1977年 | 55篇 |
1975年 | 66篇 |
1974年 | 53篇 |
1973年 | 54篇 |
1972年 | 57篇 |
1971年 | 52篇 |
1970年 | 52篇 |
排序方式: 共有9701条查询结果,搜索用时 375 毫秒
701.
G. L. Gdalevich N. I. Izhovkina V. D. Ozerov N. Bankov S. Chapkanov L. Todorieva 《Cosmic Research》2006,44(5):419-424
The results of the satellite low-latitude and mid-latitude measurements of the disturbed plasma concentration, electron temperature, and quasi-stable electric field at heights of ~900 km after sunset are discussed. It is shown that the sharp fronts of changes in the electron temperature and plasma density observed in the experiment onboard the Intercosmos-Bulgaria-1300 satellite in the low-latitude (and equatorial) outer ionosphere can be related to damping of the oscillations of plasma electrons at local decreases of the plasma density (plasma “pits”) and formation of the vortex plasma structures at density and temperature gradients, which promotes conservation of ionosphere irregularities and makes the fronts of concentration variations steeper. Nonmonotonic variations in the plasma conductivity for the ionosphere currents in unstable plasma can be a cause of observed nonmonotonic disturbances of the vertical component of the “constant” electric field. 相似文献
702.
客户驱动的动态的全球市场及地理上分布的合作伙伴给开发敏捷制造模式下的质量保证信息系统(QAIS)带来了新的挑战,本文先对敏捷制造模式下的QAIS进行了需求分析,提出了新的分布式QAIS的实现框架,利用当前迅速发展的信息技术,建立了QAIS的开发环境并对有关关键技术进行了初步研究,最后开发完成了一个基于Web的QAIS原型系统. 相似文献
703.
In the paper, the problem of designing interplanetary trajectories with several swing-bys and deep-space maneuvers is solved using the method of virtual trajectories developed by the authors. The algorithms for the calculation of both heliocentric and planetocentric trajectory arcs are presented, including the case of resonant trajectories. The results of applying the method of virtual trajectories to the problem of designing an interplanetary transfer to Jupiter are given and compared with the baseline trajectories for the Juno, Europa Clipper, and Laplace missions. 相似文献
704.
The simplest version of the method of detecting the single molecular scattering field based on the polarization measurements of the twilight sky background by all-sky cameras has been considered. The method can be used during transitive twilight (with solar zenith angles of 94°–98°), when effective single scattering occurs in the upper stratosphere and lower mesosphere. The long-term measurements conducted using this method in the Moscow region and Apatity make it possible to determine the temperature of these atmospheric layers and estimate the contribution and properties of multiple scattering during the transitive twilight. 相似文献
705.
In this paper, we analyze the illumination conditions, the thermal regime, and the possibility of deposits of volatile compounds existing in the vicinity region (NSR S5 region) near the southern pole of the Moon. It has been found that there are no permanently shadowed zones near the Scott crater and the NSR S5 region, though the temperature conditions allow the of compounds such as CH3OH, SO2, NH3, CO2, H2S, C2H4, and water to remain stable relative to evaporation for a long time (≥1 Gyr). It has been also shown that compounds like CO and CH4 cannot stably exist in these regions. 相似文献
706.
The results of numerical solution of the wave equations for the oblique incidence of whistling electromagnetic waves upon the night ionosphere from above have been obtained and analyzed. In the studied region of altitudes, within the wavelength scale, charged particle concentration varies drastically, and damping caused by collisions between the charged and neutral particles decreases considerably. Below, the sharp lower boundary of the ionosphere, the refractive index of the whistler wave approaches unity, and plasma turbulence transform into atmospheric electromagnetic waves. The dependences of the whistler reflection factor are found in terms of energy and horizontal magnetic component of the electromagnetic wave near the Earth’s surface on the frequency and the wave vector transverse component for the plain-layered medium model at two values of latitude. Strong dependences have been found on the wave angle of incidence and frequency. At rather small angles of incidence, the wave disturbances reach the Earth’s surface, and the module of reflection coefficient logarithm is in the range of 0.4–1. At large angles of incidence, the reflection coefficient module varies over a wide range depending on specific conditions. The obtained results explain the absence of oscillation modes of plasma magnetosphere maser in the night magnetosphere. 相似文献
707.
A.?I.?EfimovEmail author L.?A.?Lukanina I.?V.?Chashei S.?F.?Kolomiets M.?K.?Bird M.?P?tzold 《Cosmic Research》2018,56(1):1-10
In 2013 and 2015, investigations of the internal solar wind were carried out using the method of two-frequency radio sounding by signals from the Mars Express European spacecraft. The values of the S- and X-bands’ frequency and the differential frequency were registered with a sampling rate of 1s at the American and European networks of ground-based tracking stations. The spatial distribution of the frequency fluctuation’s level has been studied. It has been shown that the intensity of frequency fluctuation considerably decreases at high heliolatitudes. In some radio sounding sessions, quasiperiodic oscillations of sub-mHz band have been observed in the temporal spectra of frequency fluctuations; they are supposed to be associated with the density inhomogeneities, the sizes of which are close to the turbulence outer scale. 相似文献
708.
709.
The problem of control of the on-board microgravity environment in order to extend the service life of the long-term space station has been discussed. Software developed for the ISS and the results of identifying dynamic models and external impacts based on telemetry data have been presented. Proposals for controlling the onboard microgravity environment for future long-term space stations have been formulated. 相似文献
710.