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Saeid Pourmorad Harami Reza Mousavi Solgi Ali Aleali Mohsen 《Lithology and Mineral Resources》2021,56(1):89-112
Lithology and Mineral Resources - The alluvial-fan sediments play a very important role in mineral reserves and underground water resources, though a comprehensive study on such sediments,... 相似文献
54.
Mohsen Shadmehri 《Monthly notices of the Royal Astronomical Society》2009,397(3):1521-1527
We study the dynamical effects of cosmic rays (CRs) on thermal instability in the linear regime. CRs and the thermal plasma are treated as two different interacting fluids, in which CRs can diffuse along the magnetic field lines. We show that the growth rate of the magnetothermal condensation mode is reduced because of the existence of CRs, and this stabilizing effect depends on the diffusion coefficient and the ratio of CR pressure to gas pressure. Thus, a slower rate of structure formation via thermal instability is predicted when CRs are considered. 相似文献
55.
We study the linear theory of Kelvin–Helmholtz instability in a layer of ions and neutrals with finite thickness. In the short
wavelength limit the thickness of the layer has a negligible effect on the growing modes. However, perturbations with wavelength
comparable to layer’s thickness are significantly affected by the thickness of the layer. We show that the thickness of the
layer has a stabilizing effect on the two dominant growing modes. Transition between the modes not only depends on the magnetic
strength, but also on the thickness of the layer. 相似文献
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An efficient algorithm is presented to compute the Hankel transform. The algorithm yields simultaneously all the required weights for a given order of the Bessel function using the fast Fourier transform. An additional shift is introduced to the filter abscissa besides Koefoed's shift to give a better filter performance. 相似文献
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Mohsen Jalali 《Environmental Geology》2005,47(6):763-772
Hydrochemical investigations were carried out in Bahar area, Hamadan, western Iran, to assess the chemical composition of groundwater. The area falls in a semi-arid type of climate. In this area, groundwater has been exploited over the past century mainly for irrigation and water supply. A total of 135 representative groundwater samples were collected from different wells to monitor the water chemistry of various ions. Chemical analysis of the groundwater shows that the mean concentration of the cations is of the order Ca2+>Mg 2+>Na+>K+, while that for anions is SO42–>HCO3–>Cl–>NO3–. Statistical analyses indicate positive correlation between the following pairs of parameters Cl– and Mg 2+ (r=0.71), Cl– and Na+ (r=0.76), HCO3– and Na+ (r=0.56), SO42– and Mg2+ (r=0.76), SO42– and Na+ (r=0.69). Water presents a large spatial variability of the chemical facies (Ca-HCO3, Ca-SO4, Mg-HCO3, Mg-SO4, Na-HCO3) which is in relation to their interaction with the geological formations of the basin (carbonates, dolomite and various silicates) and evaporation. The hydrochemical types Ca-HCO3 and Ca-SO4 dominate the largest part of the studied area. The dissolution of halite, calcite, dolomite, and gypsum explains part of the contained Na +, Ca2+, Mg2+, Cl–, SO42– and HCO3–, but other processes, such as cation exchange and weathering of aluminosilicates also contribute to the water composition. 相似文献
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The current structure of the central Tunisian Atlas fossilizes the different tectonic events that have succeeded and that have structured this region. The Lower Cretaceous of this sector reflects, through variations of thickness and facies, the importance of the tectonic activity during this period. The tectonic study detailed in this sector has revealed the existence of structures from the kilometric scale down to the metric one related to a compressive regime that has dominated the studied zone at least from the Upper Hauterivian until the Lower Aptian. 相似文献
60.
Mohsen Shadmehri 《Monthly notices of the Royal Astronomical Society》2005,356(4):1429-1434
For the case in which the gas of a magnetized filamentary cloud obeys a polytropic equation of state, gravitational collapse of the cloud is studied using a simplified model. We concentrate on the radial distribution and restrict ourselves to a purely toroidal magnetic field. If the axial motions and poloidal magnetic fields are sufficiently weak, we could reasonably expect our solutions to be a good approximation. We show that while the filament experiences gravitational condensation and the density at the centre increases, the toroidal flux-to-mass ratio remains constant. A series of spatial profiles of density, velocity and magnetic field for several values of the toroidal flux-to-mass ratio and the polytropic index, is obtained numerically and discussed. 相似文献