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41.
42.
刘权威 《武汉大学学报(信息科学版)》1990,15(3):36-43
本文重点研究了建立整个形变区域的形变速率曲面和形变加速率曲面,同时也研究了求这两种曲面的方法(基于多元逐步回归分析的间接法和直接法),从而使我们对整个形变区域有一个形变的整体概念,也使我们能方便地得出形变区任何一个已知其平面位置的点在任一观测期内的形变量。 相似文献
43.
Ulysses 是迄今为止第一次沿独特的日球纬度方向考察日球高纬度空间区域的飞船。本文描述了 Ulysses 飞船的部分主要观测结果,并进行了分析,在 Ulysses 飞船穿越太阳南,北极之前,科学家们提出了各种不同的太阳风速度、磁场等参量的纬向变化模型。分析表明,这些模型都不能解释 Ulysses 飞船的观测结果。Ulysses 飞船的观测对经典的太阳风理论提出了挑战,太阳风的加热与加速是一个远没有被解决的问题。观测与分析表明,经典热传导不可能驱动高速流,太阳风的加速伴随着加热的发生,而加热率大小可能与离子的回旋频率有关;太阳风的热源可能不是单一的形式,而且不同形式的热源对太阳的加热贡献大小与日球径向距离有关。本文讨论并分析了几种可能的太阳风加热与加速机制。 相似文献
44.
Corrado Massa 《Astrophysics and Space Science》2006,305(4):377-384
Quantum theory in Robertson – Walker spacetime suggests the existence of a minimal energy ε of the order of 10−45 erg. Reasonable forms for ε give the expansion factor R=R(t)(t= the cosmic time) with no need of gravitational field equations.Einstein's theory should be modified in gravitational fields of strength less than ε c/ħ ∼ 10−8 cm/s2 where c is the speed of light and ħ is the reduced Planck constant. The cosmological term λ is expected to decrease as the universe expands.In the Appendix, ε is derived from a big bang – big crunch Newtonian cosmology. 相似文献
45.
46.
V. A. Dogiel A. V. Gurevich Ya. N. Istomin K. P. Zybin 《Astrophysics and Space Science》2005,297(1-4):201-211
Acceleration of charged particles by neutral gas turbulence in giant molecular clouds is considered. The gamma-ray emission
from these clouds is estimated. It is shown that molecular clouds can be the counterparts of some of unidentified sources. 相似文献
47.
Energetic particles in a turbulent medium can be subject to second-order Fermi acceleration due to scattering on moving plasma waves. This mechanism leads to growing particle momentum dispersion and, at the same time, increases the mean particle energy. In the most frequently met situations both processes can be represented by a single momentum diffusion term in the particle kinetic equation. In the present paper we discuss the conditions allowing the additional term for regular acceleration to arise. For forward-backward asymmetric scattering centres, besides the diffusive term one should explicitly consider the regular acceleration term in momentum space, which can consist of the first-order (∝ V), as well as the second-order (∝ V2) part in the wave velocity V. We derive the condition for the scattering probability in the wave rest frame requied for vanishing the regular acceleration term and provide a simple mechanical example illustrating the theoretical concepts. Finally, we address its possible role in cosmic ray acceleration processes. 相似文献
48.
49.
In-situ particle acceleration in extragalactic radio hot spots: observations meet expectations 总被引:1,自引:0,他引:1
G. Brunetti K.-H. Mack M. A. Prieto S. Varano 《Monthly notices of the Royal Astronomical Society》2003,345(3):L40-L44
We discuss, in terms of particle acceleration, the results from optical VLT observations of hot spots associated with radio galaxies. On the basis of observational and theoretical grounds, the following is shown. (i) Relatively low radio-radio power hot spots are the optimum candidates for being detected at optical waves. This is supported by an unprecedented optical detection rate of 70 per cent out of a sample of low radio power hot spots. (ii) The shape of the synchrotron spectrum of hot spots is mainly determined by the strength of the magnetic field in the region. In particular, the break frequency, related to the age of the oldest electrons in the hot spots, is found to increase with decreasing synchrotron power and magnetic field strength. Both observational results are in agreement with an in-situ particle acceleration scenario. 相似文献
50.
W. Kundt 《Journal of Astrophysics and Astronomy》1984,5(3):277-283
Constraints are derived on the acceleration of charges in shocks to highly relativistic energies. When applied to the extended
extragalactic radio sources and to the cosmic rays, they cast doubt on the mechanism of ‘in-situ acceleration’, both for energy,
entropy and statistical mechanics reasons. 相似文献