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131.
CygX-1 X辐射的功率谱 总被引:1,自引:1,他引:0
运用自回归功率谱研究CygX-1X辐射的频谱特征,结果显示CygX-1转换态和高/软态时变频谱的连续成分,可以统一由有截断的幂律加噪声成分描述,转换态存在小于3Hz的宽峰结构及准周期振荡(QPO)成分(4-12Hz),而高/软态完全可由截断幂律谱描述,不存在显著的QPO.截断频率在各态都相当稳定,在不同态的演化与平流为主的吸积流模型(ADAF)预期的情形一致.本文结果表明,自回归功率港分析是研究X射线双星光变特征的一个有效的方法. 相似文献
132.
D.A. Leahy 《Astronomische Nachrichten》2004,325(3):205-208
Hercules X‐1 is an x‐ray binary with a 1.7 day orbit and which exhibits a regular 35‐day intensity cycle, which comes in two types: 0.2 orbital phase turn‐on and 0.7 phase turn‐on. The cycle is well measured by the RXTE/ASM and is caused by a sequence of occultations by the inner and outer edges of the accretion disk. In addition to the 35‐day x‐ray cycle, the accretion disk shadows the companion star HZ Her to give the regular and well known optical modulation, and gives a modulation of the EUV emission from the system. The x‐ray modulation is most precisely measured and best for determination of the disk shape. Here disk and emission region models are used to derived the disk shape from the 0.2 turn‐on cycles and compared to a previous derivation based on 0.7 turn‐on cycles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
133.
134.
Disk clusters are developed to represent the shape of granular materials more precisely (compared to circular particles) and to minimise excessive rolling. Investigating the behaviour of dynamic disk-based discontinuous deformation analysis (DDA) with disk clusters is very important to evaluate the applicability of disk-based DDA to dynamic problems in geomechanics. In this paper, the accuracy of disk-based DDA under dynamic conditions is studied by a comprehensive sensitivity analysis. The results obtained by disk-based DDA are compared with the analytical solutions of a disk cluster on an incline subjected to gravitational force only, and three different accelerations of increasing complexity with sinusoidal input functions as well as gravitational load. In this research, the effects of time step size and interface friction angles on the results are studied. Overall, most of the error for both velocity and displacement occurs at the beginning of the solution. With increasing friction angle, the initial perturbation of the solution increases in the case of sliding under gravitational force only, and decreases in the case of sliding under dynamic loads. This study shows that disk-based DDA predicts accurately the velocities and displacements derived with respect to the frictional resistance offered by the inclines. 相似文献
135.
We self-consistently obtain shock locations in an accretion flow by using an analytical method. One can obtain the spectral
properties, quasi-periodic oscillation frequencies and the outflow rates when the inflow parameters are known. Since temperature
of the CENBOL decides the spectral states of the black hole, and also the outflow rate, the outflow rate is directly related
to the spectral states. 相似文献
136.
N. R. Sibgatullin 《Astronomy Letters》2002,28(2):83-88
We derive a formula for the nodal precession frequency and the Keplerian period of a particle at an arbitrary orbital inclination (with a minimum latitudinal angle reached at the orbit) in the post-Newtonian approximation in the external field of an oblate rotating neutron star (NS). We also derive formulas for the nodal precession and periastron rotation frequencies of slightly inclined low-eccentricity orbits in the field of a rapidly rotating NS in the form of asymptotic expansions whose first terms are given by the Okazaki-Kato formulas. The NS gravitational field is described by the exact solution of the Einstein equation that includes the NS quadrupole moment induced by rapid rotation. Convenient asymptotic formulas are given for the metric coefficients of the corresponding space-time in the form of Kerr metric perturbations in Boyer-Lindquist coordinates. 相似文献
137.
A morphological analysis study of open clusters’ properties has been achieved for a sample of 160 UBVCCD open star clusters of approximately 128,000 stars near the galactic plane. The data was obtained and reduced from Tadross (2001) using the same reduction procedures, which makes this catalogue the largest homogeneous source of open clusters’ parameters. 相似文献
138.
Disk wind in young binaries with low-mass secondary components: Optical observational manifestations
We consider a model of a young binary with a low-mass secondary component. Mass accretion from the remnants of the protostellar
cloud onto the binary components is assumed to take place in accordance with current models; i.e., it proceeds mainly onto
the low-mass component. The accretion is accompanied by mass outflow (disk wind), whose low-velocity component can be partially
captured by the primary component. As a result, an asymmetric common envelope is formed. Its densest part is involved in the
orbital motion of the secondary and can periodically shield the primary component of the binary from the observer. Assuming
a standard dust-to-gas ratio for the disk wind (1: 100), we calculated the possible photometric effects from such eclipses
and showed that they could be observed even at moderate accretion rates onto the low-mass binary component, ∼10−8–10−9
M
⊙ per year. In this case, the parameters of the minima depend on the model of the disk wind, on the ratio of its characteristic
velocity to the orbital velocity of the secondary, and on its orbital inclination to the line of sight. These results can
form the basis for interpreting a wide range of phenomena observed in young stars, such as the activity cycles in UX Ori stars,
the unusually broad minima in some young eclipsing systems, etc., and for searching for substellar objects and massive protoplanets.
In addition, the peripheral parts of the gas and dust disk around a young binary can fall within the shadow zone produced
by the opaque part of the common envelope. In such cases, a shadow from the common envelope must be observed on the disk;
this shadow must move over the disk following the orbital motion of the low-mass component. Detection and investigation of
such structures in the images of protoplanetary disks may become a method of searching for protoplanets and studying binaries
at early stages of their evolution. 相似文献
139.
140.