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111.
An analysis of a two-dimensional unsteady flow of a viscous, incompressible electrically-conducting fluid through a porous medium bounded by two infinite parallel plates under the action of a transverse magnetic field is presented. The lower plate is fixed while the other is oscillating in its own plane. Expressions for the transient velocity, the amplitude, the phase angle, and the skin-friction are derived. The effects of the magnetic parameters, permeability of the porous medium, and the frequency parameter are discussed. 相似文献
112.
Jean Gaudant Jean-Paul Saint-Martin Mostefa Bessedik Bouhameur Mansour Pierre Moissette Jean-Marie Rouchy 《Journal of African Earth Sciences》1997,24(4):511-529
A new locality of Messinian fossil fish has been found in the diatomite outcropping in the surroundings of the former “Ferme Giraud”, in the Murdjadjo Massif (near Oran, Algeria). It has yielded an oligospecific fish fauna, including five species indicative of a littoral marine environment that may have occurred in a gulf bottom. This was probably linked to a brackish lagoon, as indicated by the diatom flora. 相似文献
113.
The diffraction of linear waves by a uniform vertical cylinder with cosine-type radial perturbations
The interaction of linear waves with a uniform, bottom-mounted, surface-piercing cylinder whose diameter exhibits a cosine-type variation is investigated. Two solution methods are presented. One method is based on a perturbation theory, using a perturbation parameter defined in terms of the surface geometry of the cylinder. The analysis includes terms up to the first-order in this parameter, where the zeroth-order solution corresponds to a circular cylinder. The velocity potentials at the zeroth and first orders are expressed as eigenfunction expansions involving unknown coefficients that are subsequently determined through the cylinder boundary conditions. The second method is based on Green's theorem and gives rise to an integral equation for the fluid velocity potential on the cylinder surface. A comparison between the results of these two methods has proved that they are in good agreement for small values of the perturbation parameter. Numerical results are presented that illustrate the influence of the magnitude and frequency of these perturbations on the resulting hydrodynamic force and the wave runup on the cylinder. 相似文献
114.
Estimation of ship motions using closed-form expressions 总被引:1,自引:0,他引:1
A semi-analytical approach is used to derive frequency response functions for the wave-induced motions for monohull ships. The results are given as closed-form expressions and the required input information for the procedure is restricted to the main dimensions: length, breadth, draught, block coefficient and water plane area together with speed and heading. The formulas make it simple to obtain quick estimates of the wave-induced motions and accelerations in the conceptual design phase and to perform a sensitivity study of the variation with main dimensions and operational profile. 相似文献
115.
The coercivity spectrum of low-field high-temperature partial thermoremanent magnetization (PTRM) of a synthetic hematite powder, extremely high at room temperature, decreases very slowly with increasing temperature up to 500°C then decreases rapidly, especially above 600°C. From the AF demagnetization curves at 600 and 650°C it is calculated, following the Néel's theory of single-domain particles that the grains carrying the PTRM have a mean coercive force of 23 ± 5 kOe and a mean grain size of 0.40 ± 0.15 μm, which is not significantly different from the mean grain size of 0.48 ± 0.03 μm from electron micrograph observations. 相似文献
116.
Nemati Fatemeh Grilli Stephan T. Ioualalen Mansour Boschetti Laurie Larroque Christophe Trevisan Jenny 《Natural Hazards》2019,96(2):553-586
Natural Hazards - The French Riviera is a densely populated and touristic coast. It is also one of the most seismically active areas of the Western Mediterranean. This is evidenced by the Mw... 相似文献
117.
Mansour A. Al-Garni 《Acta Geophysica》2010,58(1):143-162
A new approach is proposed in order to interpret spontaneous potential (self-potential) anomalies related to simple geometric-shaped
models such as sphere, horizontal cylinder, and vertical cylinder. This approach is mainly based on using neural network inversion
of SP anomalies, particularly modular algorithm, for estimating the parameters of different simple geometrical bodies. However,
Hilbert transforms are involved to determine the origin location in order to reduce the parameters which minimize the ambiguity
in the inverted models. The inversion has been tested first on synthetic data from different models, using only one well-trained
network. The results of inversion show that the parameter values derived by the inversion are identical to the true values
of parameters. Noise analysis has been also examined, where the results of the inversion produce acceptable results up to
10% of white Gaussian noise. The validity of the neural network inversion is demonstrated through published real field SP
taken from southern Bavarian Woods, Germany. A comparable and acceptable agreement is shown between the results of inversion
derived by the neural network and those from the real field data. 相似文献
118.
Mansour A. Al-Garni 《Arabian Journal of Geosciences》2017,10(15):337
A new approach is proposed to interpret magnetic anomalies caused by isolated thin dike-like causative targets. The approach is essentially based on utilizing artificial neural network (ANN) inversion for estimating the problem parameters. Particularly, the modular neural network (MNN) is used for the inversion process in order to quantitatively interpret the magnetic anomalies. The MNN inversion has been first tested on a synthetic data with and without random white Gaussian noise. The effect of random noise has been clearly investigated where it showed that the approach provided satisfactory results. Furthermore, three field examples have been inverted in order to investigate the applicability of the proposed approach. The results showed good agreement with the techniques that have been stated in the literatures. 相似文献
119.
The changes in the shrinkage and physicochemical properties of untreated and treated organic soil using several chemical additives were investigated. In order to evaluate the effect of each chemical solution on the peaty soil environment different experiments namely; shrinkage limit, unconfined compressive strength (UCS), pH test, and water content were undertaken. The results of the laboratory experiments are further proved and interpreted using the X-ray diffraction, scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy tests. The result unveils the structure of the treated soil significantly changed depending upon the used additive type and concentrations. The rate of shrinkage largely decreased when sodium silicate additives are used. In addition, it was observed that UCS value increased up to 500% and water content reduced up to 50% in comparison with untreated samples, depend on the amount of used non-traditional additives. The SEM micrographs of the sample before and after treatment validate the results obtained and analyzed from experiments. 相似文献
120.