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81.
K. Kudela M. Minarovjech V. Ruin M. Rybanský V. Kollr 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2005,36(12):2368-2371
The cross correlation of daily values of coronal hole areas at the eastern limb of the Sun constructed from the ground based measurements of the green coronal line and daily mean cosmic ray intensities over long time periods shows asymmetry: at the maximum of their 27 day cycle, cosmic ray intensities are better correlated with coronal hole areas 66 days before than with the current value. This indicates the potential for using coronal emission data as one of the parameters for eventual prediction of the level of cosmic ray flux at neutron monitor energies. 相似文献
82.
83.
In March/April 1984 eleven EXOSAT observations of Her X-1 were performed sampling a full 35 day cycle. Spectral analysis of the ME and GSPC data shows that the iron line emission is present during all phases. During the main-on state we see an iron line at 6.65 ± 0.07 keV with a FWHM of 1–2 keV and an equivalent width of 300 to 400 eV. The high resolution GSPC data indicate that the line profiles have external wings and are not simple Gaussian. We report for the first time on the detection of an iron line during the intermediate-on state with about the same parameters as the main-on state line but an equivalent width a factor of 2 larger. During the off state between main-on and intermediate-on we detected a broad iron line feature at about 6.0 keV with an equivalent width of 2 keV. We discuss the Alfven region and a hot corona at the inner region of the accretion disk as the possible sites of the line production. 相似文献
84.
During the last several years significant progress has been made in understanding MHD turbulence in the Earth’s plasma sheet.
Due to the statistically transitory properties of fluctuations, finite size and boundary effects, however, issues of fundamental
importance remain unresolved. Here we concentrate on such intrinsic features of plasma sheet turbulence as its origin and
dynamical nature. In particular, we investigate bursty bulk flow driven multi-scale transfer of energy towards the dissipation
scale, and provide evidence for the presence of non-linear interactions. We show that, in contrast with previous results,
Alfvénic fluctuations together with 2D eddy interactions may appear as important constituents of turbulence in the plasma
sheet. 相似文献
85.
L10-TiAl金属间化合物Mn,Nb合金化电子结构的计算 总被引:6,自引:0,他引:6
采用第一原理赝势平面波方法计算了L10型TiAl金属间化合物中掺入Mn,Nb后的电子结构和价键结构.通过合金原子形成热得出Mn优先占据Al点阵位置,Nb优先占据Ti点阵位置.Mulliken聚居数分析发现Mn或Nb合金化后,分别降低了(001)和(002)面内的原子间键合强度,掺入Nb还降低了层间的原子间键合强度,而掺入Mn,则使层间原子间键合强度增加.整体上来讲,掺入Mn有利于改善TiAl的室温脆性,而掺入Nb,不利于改善TiAl的室温脆性. 相似文献
86.
87.
Goldsten J. O. McNutt R. L. Gold R. E. Gary S. A. Fiore E. Schneider S. E. Hayes J. R. Trombka J. I. Floyd S. R. Boynton W. V. Bailey S. Brückner J. Squyres S. W. Evans L. G. Clark P. E. Starr R. 《Space Science Reviews》1997,82(1-2):169-216
An X-ray/gamma-ray spectrometer has been developed as part of a rendezvous mission with the near-Earth asteroid, 433 Eros, in an effort to answer fundamental questions about the nature and origin of asteroids and comets. During about 10 months of orbital operations commencing in early 1999, the X-ray/Gamma-ray Spectrometer will develop global maps of the elemental composition of the surface of Eros. The instrument remotely senses characteristic X-ray and gamma-ray emissions to determine composition. Solar excited X-ray fluorescence in the 1 to 10 keV range will be used to measure the surface abundances of Mg, Al, Si, Ca, Ti, and Fe with spatial resolutions down to 2 km. Gamma-ray emissions in the 0.1 to 10 MeV range will be used to measure cosmic-ray excited elements O, Si, Fe, H and naturally radioactive elements K, Th, U to surface depths on the order of 10 cm. The X-ray spectrometer consists of three gas-filled proportional counters with a collimated field of view of 5° and an energy resolution of 850 eV @ 5.9 keV. Two sunward looking X-ray detectors monitor the incident solar flux, one of which is the first flight of a new, miniature solid-state detector which achieves 600 eV resolution @ 5.9 keV. The gamma-ray spectrometer consists of a NaI(Tl) scintillator situated within a Bismuth Germanate (BGO) cup, which provides both active and passive shielding to confine the field of view and eliminate the need for a massive and costly boom. New coincidence techniques enable recovery of single and double escape events in the central detector. The NaI(Tl) and BGO detectors achieve energy resolutions of 8.7% and 14%, respectively @ 0.662 MeV. A data processing unit based on an RTX2010 microprocessor provides the spacecraft interface and produces 256-channel spectra for X-ray detectors and 1024-channel spectra for the raw, coincident, and anti-coincident gamma-ray modes. This paper presents a detailed overview of the X-ray/Gamma-ray Spectrometer and describes the science objectives, measurement objectives, instrument design, and shows some results from early in-flight data. 相似文献
88.
89.
Spectra of the northern polar coronal hole measured with the SUMER spectrometer on SOHO on 25 October 1996 are analyzed. We
present spectra taken at locations on the solar disk where part of the spectrometer slit intersects a polar coronal hole region
and an area of brighter emission from outside of the coronal hole area. By comparing the line intensities between the parts
of the spectrum taken inside the "dark" area of the coronal holes and the brighter regions, we work out the signatures of
the specific coronal hole in the chromosphere, transition region and lower corona. We find that emissions of neutral atom
lines, of which there are many in the spectrum of SUMER, show no difference between the coronal hole and the bright boundary
areas, whereas all ionized species show strong intensity enhancements, including the continuum emissions of carbon and hydrogen.
These enhancements are larger than in normal quiet Sun areas.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
90.
Sabiha Tunçel Güçtekin Selçuk Bilir Salih Karaali Olcay Plevne Serap Ak 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(3):1360-1373
We used the ugr magnitudes of 1437467 F-G type main-sequence stars with metal abundance dex and estimated radial and vertical metallicity gradients for high Galactic-latitude fields, and , of the Milky Way Galaxy. The radial metallicity gradient dex kpc?1 estimated for the stars with kpc is attributed to the thin-disc population. While, the radial gradients evaluated for stars at higher vertical distances are close to zero indicating that the thick disc and halo have not undergone a radial collapse phase at least at high Galactic latitudes. The vertical metallicity gradients estimated for stars with three different Galactic latitudes, and do not show a strong indication for Galactic latitude dependence of our gradients. The thin disc, kpc, with a vertical metallicity gradient dex kpc?1, is dominant only in galactocentric distance interval kpc, while the thick disc ( kpc) could be observed in the intervals and kpc with compatible vertical metallicity gradients, i.e. dex kpc?1 and dex kpc?1. Five vertical metallicity gradients are estimated for the halo ( kpc) in three galactocentric distance intervals, and kpc. The first one corresponding to the interval kpc is equal to dex kpc?1, while the others at larger galactocentric distances are close to zero. We derived synthetic vertical metallicity gradients for 2,230,167 stars and compared them with the observed ones. There is a good agreement between the two sets of vertical metallicity gradients for the thin disc, while they are different for the thick disc. For the halo, the conspicuous difference corresponds to the galactocentric distance interval kpc, while they are compatible at higher galactocentric distance intervals. 相似文献