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121.
I. V. Gosachinskii 《Astronomy Letters》2005,31(3):179-185
The well-known shell supernova remnant (SNR) HB3 is part of a feature-rich star-forming region together with the nebulae W3, W4, and W5. We study the HI structure around this SNR using five RATAN-600 drift curves obtained at a wavelength of 21 cm with an angular resolution of 2′ in one coordinate over the radial-velocity range ?183 to +60 km s?1 in a wider region of the sky and with a higher sensitivity than in previous works by other authors. The spatial-kinematic distribution of HI features around the SNR clearly shows two concentric expanding shells of gas that surround the SNR and coincide with it in all three coordinates (α, δ, and V). The outer shell has a radius of 133 pc, a thickness of 24 pc, and an expansion velocity of 48 km s?1. The mass of the gas in it is ≈2.3 × 105M⊙. For the inner shell, these parameters are 78 pc, 36 pc, 24 km s? 1, and 0.9 × 105M⊙, respectively. The inner shell is immediately adjacent to the SNR. Assuming that the outer shell was produced by the stellar wind and the inner shell arose from the shock wave of the SNR proper, we estimated the age of the outer shell, ≈1.7 × 106 yr, and the mechanical luminosity of the stellar wind, 1.5 × 1038 erg s?1. The inner shell has an age of ≈106 yr and corresponds to a total supernova explosion energy of ≈1052 erg. 相似文献
122.
High resolution (3 arcsec-4 arcsec) maps of three compact sources in CTB 80, observed with the Very Large Array at 6 and 20
cm wavelengths are presented. The central core consists of a limb-brightened shell (of diameter 30 arcsec) superimposed on
a diffuse emission of size 75 arcsec x 45 arcsec. The compact sources 1949 + 324 and 1952 + 332 located near the tips of the
southwest and northeast ridges are rather remarkable and possibilities for these to be fragments ejected by the SN are examined.
1949 + 324 is fully resolved by the 4 arcsec beam and shows structure with multiple components oriented perpendicular to the
ridge. 1950 + 326 is a background radio source. 相似文献
123.
We have reanalysed a homogeneous catalogue of shell-type supernova remnants and we find that the radio data are consistent
with a birthrate of one in 22±3 yr. Our approach is based on the secular decrease of surface brightness of the historical
remnants whose ages are precisely known. The abovementioned birthrate is significantly higher than most previous estimates
which range from one in 50–150 yr, and is consistent with the supernova rate in our galaxy derived from historical observations,
as well as with recent estimates of the pulsar birthrate. 相似文献
124.
A. J. Lim 《Astrophysics and Space Science》1995,233(1-2):273-280
In shocked media of high preshock ionisation, the lack of thermal contact between atoms in the neutral component of the gas can prevent the formation of a thermal equilibrium independent of the ionic component. The behaviour of the neutral gas in such a shock is dominated by the atomic processes driven by the postshock ionic component.A transport equation for the velocity distribution of the neutral gas is explicitly solved under the physical conditions of a 1D ionic shock transition. The resulting distributions are used to calculate predicted H
line emission from such a system. 相似文献
125.
Ocker C. De Jager 《Astrophysics and Space Science》1995,230(1-2):279-298
A rapidly spinning, slowly accreting magnetic white dwarf (or X-ray pulsar) in hibernation is expected to result in rapid spindown as a result of the stretching and reconnection of magnetic field lines, leading to particle acceleration at the magnetospheric radiusoutside the corotation radius, and the propeller type ejection of magnetized synchrotron-emitting clouds. This may explain the non-thermal (radio and-rays) emission seen from the unique nearby AE Aquarii. Moving to Galactic distances we show how TeV-ray observations of pulsar-driven supernova remnants (with well-measured synchrotron X-ray spectra) allow us to obtain a direct measurement of the average magnetic field strength in the nebula. Finally, GeV to TeV observations of-ray blazars out to redshifts of 2 allow us to probe the intergalactic infrared radiation field, the Hubble constant and possibly the parameter of the Universe. 相似文献
126.
Lynne K. Deutsch Joseph L. Hora Harold M. Butner William F. Hoffmann Giovanni G. Fazio 《Astrophysics and Space Science》1995,231(1-2):89-92
We present CO(1-0) observations toward the soft gamma-ray repeater SGR 1806-20. We discuss the implications on the distance to the X-ray counterpart: AX 1805.7-2025. We also present an upper limit at = 1.3 mm for the thermal emission from dust and high resolution IRAS maps of the region. SGR 1806-20 is very likely associated with the H II complex W31. The G10.0-0.3 supernova remnant (SNR) could be expanding in the very low density region produced by the wind of the bright O9-B2 star recently detected.National Academy of Sciences / National Research Council Resident Research Associate 相似文献
127.
We study the self-similar magnetohydrodynamics (MHD) of a quasi-spherical expanding void (viz. cavity or bubble) surrounding the centre of a self-gravitating gas sphere with a general polytropic equation of state. We show various analytic asymptotic solutions near the void boundary in different parameter regimes and obtain the corresponding void solutions by extensive numerical explorations. We find novel void solutions of zero density on the void boundary. These new void solutions exist only in a general polytropic gas and feature shell-type density profiles. These void solutions, if not encountering the magnetosonic critical curve (MCC), generally approach the asymptotic expansion solution far from the central void with a velocity proportional to radial distance. We identify and examine free-expansion solutions, Einstein–de Sitter expansion solutions, and thermal-expansion solutions in three different parameter regimes. Under certain conditions, void solutions may cross the MCC either smoothly or by MHD shocks, and then merge into asymptotic solutions with finite velocity and density far from the centre. Our general polytropic MHD void solutions provide physical insight for void evolution, and may have astrophysical applications such as massive star collapses and explosions, shell-type supernova remnants and hot bubbles in the interstellar and intergalactic media, and planetary nebulae. 相似文献
128.
Astronomy Letters - Our study of the photometric and spectroscopic observations of SN 1987A based on the hydrodynamic modeling of its bolometric light curve and nonstationary hydrogen kinetics and... 相似文献
129.
We investigate the generation mechanism of long-wavelength Alfvénic disturbances near the front of a collisionless shock that propagates in a partially ionized plasma. The wave generation and dissipation rates are calculated in the linear approximation. The instability is attributable to a current of energetic particles upstream of the shock front. The generation of long-wavelength magnetic fluctuations is most pronounced for strong shocks, but the effect is retained for shocks with a moderate particle acceleration efficiency without any noticeable modification of the shock structure by the pressure of accelerated particles. The mode generation time for supernova remnants in a partially ionized interstellar medium is shown to be shorter than their age. Long-wavelength magnetic disturbances determine the limiting energies of the particles accelerated at a shock by the Fermimechanism. We discuss the application of the mechanism under consideration to explaining the observed properties of the SN 1006 remnant. 相似文献
130.
Kuniaki Masai 《Astrophysics and Space Science》2005,298(1-2):155-162
We discuss radiation properties of plasmas in high-energy astrophysics with a keyword nonequilibrium: non-LTE level populations, nonequilibrium ionization, and non-Maxwellian distribution function, beginning with radiative
transfer. We focus particularly on supernova remnants interacting with the circumstellar/interstellar matter, and also mention
line emission processes in accretion gas onto a neutron star or black hole, and in the X-ray afterglow of γ-ray bursts. 相似文献