全文获取类型
收费全文 | 163篇 |
免费 | 0篇 |
专业分类
航空 | 87篇 |
航天技术 | 27篇 |
航天 | 49篇 |
出版年
2021年 | 3篇 |
2019年 | 2篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2015年 | 2篇 |
2014年 | 3篇 |
2013年 | 8篇 |
2012年 | 7篇 |
2011年 | 12篇 |
2010年 | 3篇 |
2009年 | 7篇 |
2008年 | 8篇 |
2007年 | 8篇 |
2006年 | 5篇 |
2005年 | 12篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 3篇 |
2000年 | 1篇 |
1999年 | 5篇 |
1997年 | 1篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1989年 | 1篇 |
1987年 | 5篇 |
1986年 | 3篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
1968年 | 5篇 |
1967年 | 6篇 |
1966年 | 7篇 |
排序方式: 共有163条查询结果,搜索用时 31 毫秒
141.
Charles E. Schlemm II Richard D. Starr George C. Ho Kathryn E. Bechtold Sarah A. Hamilton John D. Boldt William V. Boynton Walter Bradley Martin E. Fraeman Robert E. Gold John O. Goldsten John R. Hayes Stephen E. Jaskulek Egidio Rossano Robert A. Rumpf Edward D. Schaefer Kim Strohbehn Richard G. Shelton Raymond E. Thompson Jacob I. Trombka Bruce D. Williams 《Space Science Reviews》2007,131(1-4):393-415
NASA’s MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) mission will further the understanding of
the formation of the planets by examining the least studied of the terrestrial planets, Mercury. During the one-year orbital
phase (beginning in 2011) and three earlier flybys (2008 and 2009), the X-Ray Spectrometer (XRS) onboard the MESSENGER spacecraft
will measure the surface elemental composition. XRS will measure the characteristic X-ray emissions induced on the surface
of Mercury by the incident solar flux. The Kα lines for the elements Mg, Al, Si, S, Ca, Ti, and Fe will be detected. The 12°
field-of-view of the instrument will allow a spatial resolution that ranges from 42 km at periapsis to 3200 km at apoapsis
due to the spacecraft’s highly elliptical orbit. XRS will provide elemental composition measurements covering the majority
of Mercury’s surface, as well as potential high-spatial-resolution measurements of features of interest. This paper summarizes
XRS’s science objectives, technical design, calibration, and mission observation strategy. 相似文献
142.
Mihail P. Petkov Steven M. Jones Gerald E. Voecks Kenneth J. Hurst Olivier Grosjean Delphine Faye Guillaume Rioland Cecily M. Sunday Emma M. Bradford William N. Warner Jerami M. Mennella Ned W. Ferraro Manuel Gallegos David M. Soules Philippe Lognonné W. Bruce Banerdt Jeffrey W. Umland 《Space Science Reviews》2018,214(8):112
We report on the development of a passive sorption pump, capable of maintaining high-vacuum conditions in the InSight seismometer throughout the duration of any extended mission. The adsorber material is a novel zeolite-loaded aerogel (ZLA) composite, which consists of fine zeolite particles homogeneously dispersed throughout a porous silica network. The outgassing species within the SEIS evacuated container were analyzed and the outgassing rate was estimated by different methods. The results were used to optimize the ZLA composition to adsorb the outgassing constituents, dominated by water, while minimizing the SEIS bakeout constraints. The InSight ZLA composite additionally facilitated substantial CO2 adsorption capabilities for risk mitigation against external leaks in Mars atmosphere. To comply with the stringent particle requirements, the ZLA getters were packaged in sealed containers, open to the SEIS interior through \(1~\upmu\mbox{m}\)-size pore filters. Results from experimental validation and verification tests of the packaged getters are presented. The pressure forecast based on these data, corroborated by rudimentary in situ pressure measurements, infer SEIS operational pressures not exceeding \(10^{-5}~\mbox{mbar}\) throughout the mission. 相似文献
143.
Paul Morgan Matthias Grott Brigitte Knapmeyer-Endrun Matt Golombek Pierre Delage Philippe Lognonné Sylvain Piqueux Ingrid Daubar Naomi Murdoch Constantinos Charalambous William T. Pike Nils Müller Axel Hagermann Matt Siegler Roy Lichtenheldt Nick Teanby Sharon Kedar 《Space Science Reviews》2018,214(6):104
This article discusses relevant physical properties of the regolith at the Mars InSight landing site as understood prior to landing of the spacecraft. InSight will land in the northern lowland plains of Mars, close to the equator, where the regolith is estimated to be \(\geq3\mbox{--}5~\mbox{m}\) thick. These investigations of physical properties have relied on data collected from Mars orbital measurements, previously collected lander and rover data, results of studies of data and samples from Apollo lunar missions, laboratory measurements on regolith simulants, and theoretical studies. The investigations include changes in properties with depth and temperature. Mechanical properties investigated include density, grain-size distribution, cohesion, and angle of internal friction. Thermophysical properties include thermal inertia, surface emissivity and albedo, thermal conductivity and diffusivity, and specific heat. Regolith elastic properties not only include parameters that control seismic wave velocities in the immediate vicinity of the Insight lander but also coupling of the lander and other potential noise sources to the InSight broadband seismometer. The related properties include Poisson’s ratio, P- and S-wave velocities, Young’s modulus, and seismic attenuation. Finally, mass diffusivity was investigated to estimate gas movements in the regolith driven by atmospheric pressure changes. Physical properties presented here are all to some degree speculative. However, they form a basis for interpretation of the early data to be returned from the InSight mission. 相似文献
144.
Albert William S. Rensink Ronald A. Beusmans Jack M. 《Spatial Cognition & Computation》1999,1(2):131-144
This study presents two experiments that examine howindividuals learn relative directions betweenlandmarks in a desktop virtual environment. Subjectswere presented snapshot images of different virtualenvironments containing distinguishing landmarks anda road network. Following the presentation of eachvirtual environment, subjects were given a relativedirection test. The relative direction test involvedindicating the direction of hidden landmarks fromdifferent vantage points in the environment. Half ofthese vantage points were presented during thelearning phase, while the other half were novel.Results showed that subjects learned relativedirections between landmarks equally well when sceneswere presented in either a sequential or random order.Furthermore, viewing a configuration of landmarks ina desktop virtual environment from multipleperspectives produced a viewpoint dependentrepresentation in memory. Subjects had significantlygreater response times for new viewing perspectives,as compared to previously viewed scenes. Thisviewpoint dependent representation of the environmentpersisted despite learning under conditions ofspatio-temporal discontinuity and changes to anenvironmental frame of reference. 相似文献
145.
William R. Wilcox Krishna Doddi Manju Nair David J. Larson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1983,3(5):79-83
In an attempt to explain the influence of space processing on the microstructure of MnBiBi, eutectic mixtures were directionally solidified with a sudden change of translation rate. The MnBi fiber spacing was able to adapt to the changing freezing rate as predicted by heat transfer computations. Thus the microstructure adapts more rapidly than the freezing rate could be changed in the present experiments. 相似文献
146.
William P. Bishop 《Space Policy》1986,2(4):322-341
This article reviews the revolution in remote sensing which has taken place over the past 25 years. This revolution could not have occurred without the closest cooperation among government agencies, industry and academia. International cooperation is shown to be essential in carrying out the bold missions planned for the next decade. The article reviews the history of the NASA-NOAA relationship, and the history of international partnerships with emphasis on development of the operational METSAT system. The government-industry partnership is also reviewed, with case studies to examine the evolution of METSAT sensor design, LANDSAT commercialization, and the NOAA Administrator's new initiative to facilitate development of a commercial Ocean Color Instrument. Government interaction with academia, in the form of National Science Foundation programmes and government-university ‘cooperative institutes’, is reviewed. The author concludes by showing how plans for integrating research and operations on Space Station platforms can only succeed through an alliance of all the remote-sensing players. 相似文献
147.
We discuss the rationale for a semi-permanent all-sky X-ray monitor, and investigate a variety of options for its implementation. We conclude that the Space Station offers an excellent opportunity for hosting such a monitor, and that a set of pinhole cameras can be configured to provide an effective and economical monitor system. A baseline of six independent pinhole modules, each of which requires approximately one cubic foot, 30 pounds, 2 watts, and 100 bits per second, can provide full sky coverage with scientifically interesting sensitivities. No other resources or special accommodation (such as detailed alignment registration, time-tagging or on-orbit servicing) would be required. The baseline system can locate bright sources to a few arc min, and can simultaneously measure each of the several hundred sources in the sky brighter than a few thousandths the intensity of the Crab nebula every day for decades. 相似文献
148.
Meteoroids and orbital debris pose a serious damage threat to all spacecraft. The effects of a meteoroid/orbital debris (M/OD) impact depend on a variety of factors, including where the M/OD impact occurs, the size, composition, and speed of the impacting object, and the function of the impacted spacecraft system. These effects can be minimal, can degrade a functional spacecraft component, or can compromise spacecraft functionality, even to the point of mission loss or loss of life. To minimize the damage threat from the meteoroid/orbital debris environment, it is often necessary to install protective shielding around critical spacecraft systems. If a system cannot be shielded, operational constraints may need to be imposed to reduce the damage threat. This paper presents an overview of the research and development activities performed since the late 1950s with an aim of increasing the level of protection afforded satellites and spacecraft operating in the M/OD environment and ultimately mitigating the mechanical and structural effects of an M/OD impact. 相似文献
149.
Tewell J. Robert Tobey William H. 《IEEE transactions on aerospace and electronic systems》1966,(3):346-352
One purpose of the GEMINI program is to study the problem of and establish techniques associated with acquisition, tracking, and photography of terrestrial objects from the orbiting spacecraft. This paper describes a ground-based simulation which was performed to obtain a realistic understanding of this problem and to provide the astronauts with preflight experience. The results presented evaluate the test subjects' performance in terms of tracking-rate errors, position errors, and fuel consumption for various orbital altitudes and target offsets. 相似文献
150.
Cosmogenic argon isotopes are produced in feldspars via nuclear reactions between cosmic rays and Ca and K atoms within the lattice. These cosmogenic isotopes can be used as proxies for K and Ca, much like nuclear reactor-derived 39Ar and 37Ar are used as proxies for K and Ca, respectively, in 40Ar/39Ar geochronology. If Ca and K are uniformly distributed, then the ratio of radiogenic 40Ar (40Ar?) to cosmogenic 38Ar or 36Ar (38Arcos or 36Arcos) is proportional to the difference between the radioisotopic and exposure ages, as well as the K/Ca ratio of the degassing phase. Thus cosmogenic, radiogenic, and trapped Ar isotopes, all of which can be measured remotely and are stable over geologic time, are sufficient to generate an isochron-like diagram from which the isotopic composition of the trapped component may be inferred. Such data also provide a means to assess the extent to which the system has remained closed with respect to 40Ar?, thereby mitigating otherwise unquantifiable uncertainties that complicate the conventional K–Ar dating method. 相似文献