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111.
We calculate the profile and polarization of the Lα line in the solar corona. Coronal temperature variation, solar wind and other non-thermal motions have been taken into account. Because of the relatively low atomic weight of hydrogen the profile of the Lα line is a sensitive indicator of the coronal temperature. The line polarization contains relatively little information except for strong magnetic fields (> 70 G). 相似文献
112.
Jacques M. Beckers 《Solar physics》1996,169(2):431-442
The development of telescope capabilities tends to go in spurts. These are triggered by the availability of new techniques in optics, mechanics and/or instrumentation. So has nighttime telescope technology developed since the construction in the nineteen-forties of the 5-m Hale telescope, first by the introduction in the sixties of high efficiency electronic detectors, followed recently by the production of large 8- to 10-m mirrors and now by the implementation of adaptive optics. In solar astronomy, major steps were the introduction of the coronagraph by Lyot in the nineteen-thirties and the vacuum telescope concept by Dunn in the sixties. In the last thirty years, telescope developments in solar astronomy have relied primarily on improved instrumental capabilities. As in nighttime astronomy, these instruments and their detectors are reaching their limits set by the quantum nature of light and the telescope diffraction. Larger telescopes are needed to increase sensitivity and angular resolution of the observations. In this paper, I will review recent efforts to increase substantially the telescope capabilities themselves. I will emphasize the concept of a large all-wavelength, coronagraphic telescope (CLEAR) which is presently being developed.Dedicated to Cornelis de Jager 相似文献
113.
The chemical analysis by EMPEDS of 140 samples in cores from six Red Sea troughs and basins has led to the discovery in the Nereus Deep of high vanadium concentrations (up to 1.3% V2 O3 ) in several bulk samples, and to the isolation of a major magnetite phase. This vanado-magnetite, remarkable for its high content of vanadium (mean = 1.45% V2 O3 ) and its lack of titanium, is frequently zoned, the V-content decreasing toward the outer zones. Oxides with up to 42% V2 O3 , have also been found. Since the origin of the magnetite is clearly authigenic, its high vanadium and low titanium concentrations are traced back to the differential hydrothermal leaching of Fe—Ti-oxides which occur profusely in basic eruptive rock clasts, actually present in some of the overlying seams. 相似文献
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Jacques Henrard 《Celestial Mechanics and Dynamical Astronomy》1970,1(3-4):437-466
For a conservative Hamiltonian system with two degrees of freedom, in the case where the two frequencies at an equilibrium of the elliptic type are commensurable or close to being so, completely canonical transformations can be formally constructed in explicit terms under the form of Lie transforms to the effect that it renders one angle coordinate ignorable and gives to the transformed Hamiltonian the form of what Garfinkel calls an ideal problem of resonance. For the problem so reduced, the unnormalized residual being omitted, natural families of periodic orbits are analyzed, their emergence from the equilibrium is discussed as well as their characteristic exponents. Special attention is given to the evolution of the system of natural families under a continuous transition through the resonance band. 相似文献
116.
Anton M. Dainty M. Nafi Toksöz Kenneth R. Anderson P. Jacques Pines Y. Nakamura G. Latham 《Earth, Moon, and Planets》1974,9(1-2):11-29
Long, reverberating trains of seismic waves produced by impacts and moonquakes may be interpreted in terms of scattering in a surface layer overlying a non-scattering elastic medium. Model seismic experiments are used to qualitatively demonstrate the correctness of the interpretation. Three types of seismograms are found, near impact, far impact and moonquake. Only near impact and moonquake seismograms contain independent information. Details are given in the paper of the modelling of the scattering processes by the theory of diffusion.Interpretation of moonquake and artificial impact seismograms in two frequency bands from the Apollo 12 site indicates that the scattering layer is 25 km thick, with a Q of 5000. The mean distance between scatterers is approximately 5 km at 25 km depth and approximately 2 km at 14 km depth; the density of scatterers appears to be high near the surface, decreasing with depth. This may indicate that the scatterers are associated with cratering, or are cracks that anneal with depth. Most of the scattered energy is in the form of scattered surface waves.Communication presented at the Lunar Science Institute Conference on Geophysical and Geochemical Exploration of the Moon and Planets, January 10–12, 1973. 相似文献
117.
It is shown in this paper that the only potentials corresponding to central force for which all the bounded orbits are periodic are the potential of the harmonic oscillator and of the two body problem. A discussion is given in the case where a circular orbit exists and when the orbits near the circular orbit are periodic.We calculate in these cases the angle between pericentre and apocentre.Celestial Mechanics 相似文献
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