全文获取类型
收费全文 | 399篇 |
免费 | 1篇 |
国内免费 | 2篇 |
专业分类
航空 | 154篇 |
航天技术 | 81篇 |
综合类 | 3篇 |
航天 | 164篇 |
出版年
2021年 | 3篇 |
2019年 | 5篇 |
2018年 | 4篇 |
2017年 | 5篇 |
2016年 | 2篇 |
2015年 | 3篇 |
2014年 | 8篇 |
2013年 | 16篇 |
2012年 | 7篇 |
2011年 | 38篇 |
2010年 | 15篇 |
2009年 | 31篇 |
2008年 | 19篇 |
2007年 | 19篇 |
2006年 | 19篇 |
2005年 | 11篇 |
2004年 | 7篇 |
2003年 | 17篇 |
2002年 | 9篇 |
2001年 | 5篇 |
2000年 | 15篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 4篇 |
1990年 | 2篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 4篇 |
1986年 | 12篇 |
1985年 | 16篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 2篇 |
1974年 | 2篇 |
1973年 | 4篇 |
1970年 | 2篇 |
1968年 | 6篇 |
1967年 | 7篇 |
1966年 | 3篇 |
1963年 | 1篇 |
排序方式: 共有402条查询结果,搜索用时 15 毫秒
151.
Hiroshi Matsui John C. Foster Donald L. Carpenter Iannis Dandouras Fabien Darrouzet Johan De Keyser Dennis L. Gallagher Jerry Goldstein Pamela A. Puhl-Quinn Claire Vallat 《Space Science Reviews》2009,145(1-2):107-135
The electric field and magnetic field are basic quantities in the plasmasphere measured since the 1960s. In this review, we first recall conventional wisdom and remaining problems from ground-based whistler measurements. Then we show scientific results from Cluster and Image, which are specifically made possible by newly introduced features on these spacecraft, as follows. 1. In situ electric field measurements using artificial electron beams are successfully used to identify electric fields originating from various sources. 2. Global electric fields are derived from sequences of plasmaspheric images, revealing how the inner magnetospheric electric field responds to the southward interplanetary magnetic fields and storms/substorms. 3. Understanding of sub-auroral polarization stream (SAPS) or sub-auroral ion drifts (SAID) are advanced through analysis of a combination of magnetospheric and ionospheric measurements from Cluster, Image, and DMSP. 4. Data from multiple spacecraft have been used to estimate magnetic gradients for the first time. 相似文献
152.
Makhosonke Berthwell Dubazane John Bosco Habarulema Jean Claude Uwamahoro 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(1):326-336
For the first time, empirical model of daytime vertical drift based on Empirical Orthogonal functions (EOF) decomposition technique is presented. Day-to-day variability of drift inferred from horizontal (H) geomagnetic field data around dip latitude for the period of 2008–2013 is used to both develop and validate the model. Results show that the EOF technique is promising with modelled values and data giving correlation coefficient values of at least 0.90 for geomagnetic conditions of both and within 2008–2013. Independent model validation shows that in situ values from ion velocity meter (IVM) instrument on-board C/NOFS satellite are closer to model estimates than the climatological Scherliess-Fejer (SF) model incorporated within the International Reference Ionosphere (IRI). 相似文献
153.
The objective of the 2009 Mars Science Laboratory (MSL), which is planned to follow the Mars Exploration Rovers and the Phoenix lander to the surface of Mars, is to explore and assess quantitatively a site on Mars as a potential habitat for present or past life. Specific goals include an assessment of the past or present biological potential of the target environment and a characterization of its geology and geochemistry. Included in the 10 investigations of the MSL rover is the Sample Analysis at Mars (SAM) instrument suite, which is designed to obtain trace organic measurements, measure water and other volatiles, and measure several light isotopes with experiment sequences designed for both atmospheric and solid-phase samples. SAM integrates a gas chromatograph, a mass spectrometer, and a tunable laser spectrometer supported by sample manipulation tools both within and external to the suite. The sub-part-per-billion sensitivity of the suite for trace species, particularly organic molecules, along with a mobile platform that will contain many kilograms of organic materials, presents a considerable challenge due to the potential for terrestrial contamination to mask the signal of martian organics. We describe the effort presently underway to understand and mitigate, wherever possible within the resource constraints of the mission, terrestrial contamination in MSL and SAM measurements. 相似文献
154.
J. Isbert J.H. Adams Jr. H.S. Ahn G.L. Bashindzhagyan K.E. Batkov M. Christl A.R. Fazely O. Ganel R.M. Gunashingha T.G. Guzik J. Chang K.C. Kim E.N. Kouznetsov Z.W. Lin M.I. Panasyuk A.D. Panov W.K.H. Schmidt E.S. Seo N.V. Sokolskaya John W. Watts J.P. Wefel J. Wu V.I. Zatsepin 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The Advanced Thin Ionization Calorimeter (ATIC) Balloon Experiment had a successful test flight and a science flight in 2000–01 and 2002–03 and an unsuccessful launch in 2005–06 from McMurdo, Antarctica, returning 16 and 19 days of flight data. ATIC is designed to measure the spectra of cosmic rays (protons to iron). The instrument is composed of a Silicon matrix detector followed by a carbon target interleaved with scintillator tracking layers and a segmented BGO calorimeter composed of 320 individual crystals totaling 18 radiation lengths to determine the particle energy. BGO (Bismuth Germanate) is an inorganic scintillation crystal and its light output depends not only on the energy deposited by particles but also on the temperature of the crystal. The temperature of balloon instruments during flight is not constant due to sun angle variations as well as differences in albedo from the ground. The change in output for a given energy deposit in the crystals in response to temperature variations was determined. 相似文献
155.
156.
As well as providing practical information on Earth-besetting problems, space science and exploration are vital tools for capturing the public imagination and encouraging young people's interest in space. The relatively small scale of some scientific instruments also allows mission participation by developing countries. Citing the work of the UN and various NGOs in promoting study and distribution of space science data, the authors recommend that it be given a higher profile and suggest a number of projects -- the Mars drill study in Egypt, refurbishment of a telescope facility in Sri Lanka -- involving developing countries that should be followed up, as well as listing ongoing successful projects. The UN is urged to continue its annual workshops on space science (apparently under threat) and to ensure its inclusion in the forthcoming UNISPACE III Conference. 相似文献
157.
John Heise 《Space Science Reviews》1985,40(1-2):79-90
Hot white dwarfs are objects that copiously emit in the Extreme Ultraviolet and soft X-ray range. They are the brightest sources seen in the Low Energy Telescope of EXOSAT, with countrates up to 25 cnts/s. in contrast to their optical and UV spectrum the total flux and spectral distribution at soft X-ray energies are highly sensitive to the effective temperature, structure and elemental composition of the dwarf's atmosphere. The imaging soft X-ray experiments onboard EXOSAT cover with large sensitivity the spectral region where the peak of emission of hot white dwarfs is expected to occur.I here review some of the (preliminary) results obtained so far with broadband X-ray photometry on a dozen or so white dwarfs, and some of the high-resolution spectra obtained for three white dwarfs with the grating spectrometers. 相似文献
158.
John P. Bradley 《Space Science Reviews》1991,56(1-2):131-138
Electron transparent thin sections (30–100 nm thick) of interplanetary dust particles and other fine-grained meteoritic materials are produced using an ultramicrotome equipped with a diamond knife. An analytical electron microscope (AEM) is imployed to examine indigenous physical properties (e.g. porosity), mineralogy, and petrography. Large data sets of quantitative point count analyses obtained from thin sections enable direct mineralogical comparison of IDPs and Halley. 相似文献
159.
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)
160.
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