全文获取类型
收费全文 | 355篇 |
免费 | 1篇 |
国内免费 | 5篇 |
专业分类
航空 | 159篇 |
航天技术 | 65篇 |
综合类 | 1篇 |
航天 | 136篇 |
出版年
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2015年 | 2篇 |
2014年 | 7篇 |
2013年 | 10篇 |
2012年 | 24篇 |
2011年 | 36篇 |
2010年 | 17篇 |
2009年 | 23篇 |
2008年 | 18篇 |
2007年 | 21篇 |
2006年 | 17篇 |
2005年 | 29篇 |
2004年 | 4篇 |
2003年 | 14篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 5篇 |
1998年 | 6篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 7篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 4篇 |
1973年 | 1篇 |
1972年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1968年 | 1篇 |
1967年 | 6篇 |
1966年 | 2篇 |
排序方式: 共有361条查询结果,搜索用时 15 毫秒
131.
Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ~30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ~55% of the surface habitable. 相似文献
132.
在北美,波音747-400运营商到海外进行机体的重维修似乎成为其唯一的选择。根据《航空周刊》5月1日的数据,美国有10家公司运营着125架波音747飞机,其中93架为波音747-400。在这些飞机中,有51架从事客运服务,主要由美联航和达美航空公司运营,其余42架用作货机。北美其他国家不运营波音747。 相似文献
133.
G. Randall Gladstone Steven C. Persyn John S. Eterno Brandon C. Walther David C. Slater Michael W. Davis Maarten H. Versteeg Kristian B. Persson Michael K. Young Gregory J. Dirks Anthony O. Sawka Jessica Tumlinson Henry Sykes John Beshears Cherie L. Rhoad James P. Cravens Gregory S. Winters Robert A. Klar Walter Lockhart Benjamin M. Piepgrass Thomas K. Greathouse Bradley J. Trantham Philip M. Wilcox Matthew W. Jackson Oswald H. W. Siegmund John V. Vallerga Rick Raffanti Adrian Martin J.-C. Gérard Denis C. Grodent Bertrand Bonfond Benoit Marquet François Denis 《Space Science Reviews》2017,213(1-4):447-473
The ultraviolet spectrograph instrument on the Juno mission (Juno-UVS) is a long-slit imaging spectrograph designed to observe and characterize Jupiter’s far-ultraviolet (FUV) auroral emissions. These observations will be coordinated and correlated with those from Juno’s other remote sensing instruments and used to place in situ measurements made by Juno’s particles and fields instruments into a global context, relating the local data with events occurring in more distant regions of Jupiter’s magnetosphere. Juno-UVS is based on a series of imaging FUV spectrographs currently in flight—the two Alice instruments on the Rosetta and New Horizons missions, and the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter mission. However, Juno-UVS has several important modifications, including (1) a scan mirror (for targeting specific auroral features), (2) extensive shielding (for mitigation of electronics and data quality degradation by energetic particles), and (3) a cross delay line microchannel plate detector (for both faster photon counting and improved spatial resolution). This paper describes the science objectives, design, and initial performance of the Juno-UVS. 相似文献
134.
Waller David Loomis Jack M. Golledge Reginald G. Beall Andrew C. 《Spatial Cognition & Computation》2000,2(4):333-354
Although the process of establishing a memoryof a location is necessary for navigation,relatively little is known about theinformation that humans use when forming placememories. We examined the relative importanceof distance and angular information aboutlandmarks in place learning. Participantsrepeatedly learned a target location inrelation to three distinct landmarks in animmersive computer-generated (virtual)environment. Later, during testing, theyattempted to return to that location. Theconfigurations of landmarks used during testingwere altered from those participants learned inorder to separate the effects of metricdistance information and information aboutinter-landmark angles. In general,participants showed greater reliance ondistance information than angular information. This reliance was affected by nonmetricrelationships present during learning, as wellas by the degree to which the learnedenvironment contained right or straightangles. 相似文献
135.
136.
Committee on Space Policy H.Guyford Stever Laurence J. Adams Consultant Retired President William A. Anders Senior Executive Vice President Arden L. Bement Jr Vice President Joseph V. Charyk Chairman of the Board Retired Chairman CEO Richard N. Cooper Robert S. Cooper President Edward E. David Jr President John M. Logsdon Director Jeremiah P. Ostriker Director Samuel C. Phillips Retired General Elmer B. Staats Edward C. Stone Jr Vice President 《Space Policy》1989,5(3)
137.
Spherical detonations have been initiated by solid explosive (Tetryl) charges in well-mixed stoicheiometric air mixtures with each of the hydrocarbons, ethane, propane, n-butane, isobutane and ethylene at atmospheric pressure. Prior to initiation, the gases were contained in plastic bags; total gas volume and available path length were up to 1.6 m3 and 2 m, respectively. The detonations were shown to be self-sustained by continuous measurement of detonation velocity using X-band microwave interferometry. Measured detonation velocities were in all cases close to calculated C-J values.In a few experiments close to the limits of detonability, velocity and blast pressure/time records indicated that the propagating wave system is sometimes irregular. The irregularity that occurs just after initiation is characterised by a reaction front velocity very much lower than the constant detonation velocity, but subsequently attaining the latter by an acceleration process. These observations indicate the existence of a dissociated phase in which shock and reaction fronts may no longer be coupled.Because similar experimental conditions were used throughout, it was possible to establish the relative susceptibilities of the various fuel gases to detonation. Comparison is made with the Zeldovich criterion and a detonation kernel theory of Lee. 相似文献
138.
David L 《Aerospace America》1996,34(3):28-33
A brief review of the status of space life sciences research is provided with an emphasis on the contributions this research has made to life here on Earth. Physiological effects of weightlessness are discussed along with methods of prevention or treatment. Several technologies are described which have resulted in advances in improved health care and in other industries. In addition, the impact of space life sciences research on women's health issues and on future space travel are discussed. 相似文献
139.
David L 《Aerospace America》1996,34(5):26-30
The distant shores of Mars were reached by numerous U.S. and Russian spacecraft throughout the 1960s to mid 1970s. Nearly 20 years have passed since those successful missions which orbited and landed on the Martian surface. Two Soviet probes headed for the planet in July, 1988, but later failed. In August 1993, the U.S. Mars Observer suddenly went silent just three days before it was to enter orbit around the planet and was never heard from again. In late 1996, there will be renewed activity on the launch pads with three probes departing for the red planet: 1) The U.S. Mars Global Surveyor will be launched in November on a Delta II rocket and will orbit the planet for global mapping purposes; 2) Russia's Mars '96 mission, scheduled to fly in November on a Proton launcher, consists of an orbiter, two small stations which will land on the Martian surface, and two penetrators that will plow into the terrain; and finally, 3) a U.S. Discovery-class spacecraft, the Mars Pathfinder, has a December launch date atop a Delta II booster. The mission features a lander and a microrover that will travel short distances over Martian territory. These missions usher in a new phase of Mars exploration, setting the stage for an unprecedented volley of spacecraft that will orbit around, land on, drive across, and perhaps fly at low altitudes over the planet. 相似文献
140.
Gordon Chin Scott Brylow Marc Foote James Garvin Justin Kasper John Keller Maxim Litvak Igor Mitrofanov David Paige Keith Raney Mark Robinson Anton Sanin David Smith Harlan Spence Paul Spudis S. Alan Stern Maria Zuber 《Space Science Reviews》2007,129(4):391-419
NASA’s Lunar Precursor Robotic Program (LPRP), formulated in response to the President’s Vision for Space Exploration, will
execute a series of robotic missions that will pave the way for eventual permanent human presence on the Moon. The Lunar Reconnaissance
Orbiter (LRO) is first in this series of LPRP missions, and plans to launch in October of 2008 for at least one year of operation.
LRO will employ six individual instruments to produce accurate maps and high-resolution images of future landing sites, to
assess potential lunar resources, and to characterize the radiation environment. LRO will also test the feasibility of one
advanced technology demonstration package. The LRO payload includes: Lunar Orbiter Laser Altimeter (LOLA) which will determine
the global topography of the lunar surface at high resolution, measure landing site slopes, surface roughness, and search
for possible polar surface ice in shadowed regions, Lunar Reconnaissance Orbiter Camera (LROC) which will acquire targeted
narrow angle images of the lunar surface capable of resolving meter-scale features to support landing site selection, as well
as wide-angle images to characterize polar illumination conditions and to identify potential resources, Lunar Exploration
Neutron Detector (LEND) which will map the flux of neutrons from the lunar surface to search for evidence of water ice, and
will provide space radiation environment measurements that may be useful for future human exploration, Diviner Lunar Radiometer
Experiment (DLRE) which will chart the temperature of the entire lunar surface at approximately 300 meter horizontal resolution
to identify cold-traps and potential ice deposits, Lyman-Alpha Mapping Project (LAMP) which will map the entire lunar surface
in the far ultraviolet. LAMP will search for surface ice and frost in the polar regions and provide images of permanently
shadowed regions illuminated only by starlight. Cosmic Ray Telescope for the Effects of Radiation (CRaTER), which will investigate
the effect of galactic cosmic rays on tissue-equivalent plastics as a constraint on models of biological response to background
space radiation. The technology demonstration is an advanced radar (mini-RF) that will demonstrate X- and S-band radar imaging
and interferometry using light weight synthetic aperture radar. This paper will give an introduction to each of these instruments
and an overview of their objectives. 相似文献