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41.
Devendraa Siingh R. P. Singh Ashok K. Singh M. N. Kulkarni A. S. Gautam Abhay K. Singh 《Surveys in Geophysics》2011,32(6):659-703
The physics of solar forcing of the climate and long term climate change is summarized, and the role of energetic charged
particles (including cosmic rays) on cloud formation and their effect on climate is examined. It is considered that the cosmic
ray-cloud cover hypothesis is not supported by presently available data and further investigations (during Forbush decreases
and at other times) should be analyzed to further examine the hypothesis. Another player in climate is lightning through the
production of NOx; this greenhouse gas, water vapour in the troposphere (and stratosphere) and carbon dioxide influence the global temperature
through different processes. The enhancement of aerosol concentrations and their distribution in the troposphere also affect
the climate and may result in enhanced lightning activity. Finally, the roles of atmospheric conductivity on the electrical
activity of thunderstorms and lightning discharges in relation to climate are discussed. 相似文献
42.
Abstract Geological field, petrographic, and anisotropy of magnetic susceptibility studies help in understanding the evolutionary history of the Garhwal synform that lies in the western Outer Lesser Himalaya. Orientations of the magnetic susceptibility axes reveal large variations at short distances as a result of superimposed deformation, and predominant stress conditions favorable for normal faulting. Rocks forming the outer limbs of the Garhwal Synform are metamorphosed up to the lower greenschist facies. The metamorphic grade increases to chlorite zone in the inner limb and the core is characterized by chlorite–biotite to garnet zones. The different grades of metamorphism are separated by thrusts and the structure is described as a pop-up klippen. 相似文献
43.
Numerical Modeling of Axisymmetric Flow 总被引:1,自引:0,他引:1
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Field stratigraphy, sedimentology and optically stimulated luminescence (OSL) dating have been used to reconstruct the southwest monsoon variability in the semi‐arid region of southern India during the late Holocene. Facies architecture and OSL dating of the water‐lain sediment suggest prevalence of a weak hydrological regime around 3 ka. Following this, a progressive strengthening of monsoon occurred till 2 ka. After 2 ka and until 1 ka fluvial activity was nearly dormant, indicating weakening of the monsoon. Presence of high‐magnitude flood deposits, overbank sedimentation and pedogenesis during 1–0.6 ka indicate intensification of the southwest monsoon in the basin. The onset of aridity was associated with episodic storm surge events that are manifested in the pond sedimentation and localised aeolian accretion. This phase is bracketed between 0.5 ka and 0.2 ka. A renewed phase of monsoonal activity was observed in the form of floodplain aggradation between 180 and 90 years ago. In the past 70 years no significant change in the monsoon performance has been observed. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Two theoretical models, spherical and cylindrical, of propagation of shockwaves with varying energy in a rotating, magneto-radiative,self-gravitating non-uniform atmosphere have been developed. Subsequently,a comparison between the two models has been drawn with the aid ofvariation of flow variables with distance graphically. Significant is thedifference between two models, when one observes the variations of radialvelocity, pressure, mass, radiation flux, magnetic field and energy withdistance. Also, the respective influences of radiation flux, magneticfield and rotational velocity on the variations of the flow variables havebeen studied. 相似文献
48.
The propagation features of extremely low frequency electromagnetic waves through the multicomponent ionospheric plasma are studied. It is shown that at relatively lower frequencies refractive index for right hand mode is higher than the left-hand mode, which is reversed at higher frequencies. The thermal temperature of plasma particle causes decrease in phase and group velocities of both right and left-hand modes. The crossover frequencies for different plasma models are computed and variation with ion concentration and thermal velocity is studied. Explicit expression for group velocity and travel time has been derived and studied numerically. Finally, we have presented simulation of the ion whistler spectrograms for Hydrogen, Helium and Oxygen ions present in the ionospheric plasma. The results are compared with the experimentally detected hydrogen and helium ion whistlers. The importance of the present study in the exploration of ionospheric plasma is illustrated. 相似文献
49.
Ashok K. Chugh 《国际地质力学数值与分析法杂志》1981,5(3):313-322
Existence of more than one numerical solution to the slope stability equations derived on the basis of force and moment equilibrium requirements of statistics is indicated. These solutions satisfy the boundary conditions at both ends of a potential slide mass. In the particular case considered, the details of the calculated response for the slices for each solution set assist the designer in selecting the more reasonable solution to the problem. 相似文献
50.
X-ray emissions from Young Stellar Objects (YSO) are detected by many X-ray missions that are providing important information about their properties. However, their emission processes are not fully understood. In this research note, we propose a model for the generation of emissions from a YSO on the basis of a simple interaction between the YSO and its surrounding circumstellar accretion disc containing neutral gas and charged dust. It is assumed that the YSO has a weak dipole type magnetic field and its field lines are threaded into the circumstellar disc. Considering the motion of ions and charged dust particles in the presence of neutral gas, we show that the sheared dust-neutral gas velocities can lead to a current along the direction of ambient magnetic field. Magnitude of this current can become large and is capable of generating an electric field along the magnetic field lines. It is shown how the particles can gain energy up to MeV range and above, which can produce high-energy radiations from the YSO. 相似文献