全文获取类型
收费全文 | 194篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
航空 | 76篇 |
航天技术 | 36篇 |
综合类 | 2篇 |
航天 | 81篇 |
出版年
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 5篇 |
2017年 | 2篇 |
2015年 | 1篇 |
2014年 | 9篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 15篇 |
2010年 | 9篇 |
2009年 | 16篇 |
2008年 | 6篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 6篇 |
2002年 | 4篇 |
2001年 | 3篇 |
2000年 | 4篇 |
1999年 | 7篇 |
1998年 | 3篇 |
1996年 | 3篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1968年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有195条查询结果,搜索用时 15 毫秒
191.
Alternate control laws based on an application of the linear regulator problem are developed for possible use in the operation of the Shuttle-Tethered-Subsatellite system. Control is assumed to be provided only by modulating the tension level in the tether as a function of the difference between actual and commanded tether line length, length rate, in (orbital) plane swing angle and swing angle rate. Necessary and sufficient conditions for stability of the (linear) system motion in the vicinity of its nominal local vertical orientation are developed. By proper selection of the state and control penalty matrices it is possible to obtain faster responses with no increase in maximum power levels for use in station keeping when compared with alternate control strategies. The weighting matrices are adjusted in a piecewise adaptive manner to provide control law gains in order to achieve a smooth deployment history. Successful retrievel is dependent mainly on the initial conditions and the rate at which the commanded length is reduced. 相似文献
192.
Peter S. Conti 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1982,2(9):59-66
Stellar winds are found in hot and luminous stars of all types. We see evidence of these winds in P Cygni profiles of resonance lines in the UV spectral regions, and obtain density information from them, and from optical emission lines and from free-free radiation in the infrared and radio continua from the ionized plasma. Data recently acquired from the IUE satellite are now sufficient to enable us to outline the broad parameters of these winds. It is found that for the hottest stars, those of 0-type, the mass loss rate ? is proportional to Lα. A proportionality between ? and L is predicted by the theory of radiatively driven winds; the value for α is also anticipated by the details of the theory. The dispersion of individual stellar values may be due to observational uncertainty alone, but it may also suggest that other physical parameters affect the stellar winds. The kinetic energy input of the stellar winds to the interstellar medium is considerable and may, in aggregate, be of the same order as the contribution of supernovae. 相似文献
193.
Tarter JC Backus PR Mancinelli RL Aurnou JM Backman DE Basri GS Boss AP Clarke A Deming D Doyle LR Feigelson ED Freund F Grinspoon DH Haberle RM Hauck SA Heath MJ Henry TJ Hollingsworth JL Joshi MM Kilston S Liu MC Meikle E Reid IN Rothschild LJ Scalo J Segura A Tang CM Tiedje JM Turnbull MC Walkowicz LM Weber AL Young RE 《Astrobiology》2007,7(1):30-65
Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute. 相似文献
194.
Our study of solar cycle irradiance variability in the UV between 200 and 400 nm requires a detailed knowledge of the composition of the solar spectrum in this wavelength range. We compute the synthetic spectrum from 250 to 300 nm and compare it with ATLAS3 and SOLSTICE observations. Synthetic solar spectra for solar minimum and maximum conditions show large variations in broad, strong UV lines. Strong lines of FeI between 260 nm and 264 nm show increases between 0.4× and 3×in their max/min ratio. Our ``broad lines' database shows 167 lines with similar properties between 200 nm and 400 nm. Our results raise issues of the importance of such large variability in narrow bands and the difficulty of detection in measurements with spectral resolutions of 1 nm. 相似文献
195.
Xuexi Tie Guy Brasseur Peter Hess Martin Riese 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1999,24(12):1631-1636
Differences between the dynamical characteristics of the northern hemisphere (NH) and southern hemisphere (SH) stratosphere (e.g., the temperature, the strength of polar vortex, and the mean meridional circulation) produce hemispherically asymmetrical distributions of chemical species. In this paper, we use global models to briefly discuss various effects on chemical species caused by this asymmetrical distribution, especially on stratospheric ozone. The role of hemispheric asymmetries in chlorine and bromine loadings on mid- and high latitude ozone depletion is particularly discussed. 相似文献