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11.
用布希涅斯克定义的弹性半空间内的垂直位移包括两项积分,除了积分号前面系数的差别之外,第一项积分是单层位势而第二项积分为双层位势。若扁壳基础是正高斯曲率的几何曲面,则壳底与半空间表面间的挤压强度就是半空间表面作用的分布垂直荷载。当越过边界时,双层势位的函数值和单层势位的法向导数值发生跳跃。利用这些性质,本文得出布希涅斯克积分的反演公式,从而避开要求解偏微分—积分方程组的巨大数学困难而易于得出解析解。以椭园抛物面扁壳为例说明本文方法的应用。 相似文献
12.
黄河大柳树坝基岩体地震破坏后的密度特征 总被引:2,自引:0,他引:2
本文通过对岩体地震破坏后的弹性波测试,分析其波速的制约因素,采取相应的计算公式讨论了岩体密度的计算方法,并将其与平硐内壁裂隙统计计算出的岩体密度值做了比较,说明应用弹性波速计算岩体密度的精度与科学性。 相似文献
13.
The formal solutions of displacement field to the problem of elastic wave scattering and diffraction due to an infinitely long rigid cylinder embedded in an infinite elastic medium by an impulsive point source have been obtained in the integral form. The integrals for the reflected and the diffracted waves both in the shadow zone and in the illuminated zone are evaluated asymptotically for the early time motion by the Reisdue-Cagniard method and the Saddle-point-Cagniard method.Numerical results of the diffractedP, S andPS waves at a fixed circum-distance from the surface of the rigid cylinder show noticeably that (1) the energy partition for the diffractedS wave is small in comparison with that for the diffractedP wave, (2) the wave form of the diffractedS wave is broader and more diffused than that of the diffractedP wave, (3) the direction of the radial motions of the diffractedP andS waves varies as a function of the observational point, and (4) the energy partition for the diffractedP wave is much smaller than that for the direct or the reflectedP waves.This paper has been presented at the 46th Annual International Meeting of Society of Exploration Geophysicists in Houston, Texas, Oct. 28, 1976. 相似文献
14.
Prediction of surface horizontal displacements, and gravity and tilt changes caused by filling the Three Gorges Reservoir 总被引:11,自引:0,他引:11
Horizontal displacements, and gravity and tilt changes induced by filling the Three Gorges Reservoir are modeled using elastic
loading Green functions. When the water surface reaches its highest level, the effects become maximum on the reservoir banks.
The longitudinal and latitudinal components of the horizontal displacements reach −8.2 and 7.7 mm respectively, gravity is
increased by up to 3.4 mGal, and the prime vertical and meridian components of the tilt changes are −7.8 and −17.5 arcseconds
respectively. Accordingly, the filling of the reservoir will influence values observed from global positioning system (GPS),
gravimetry and tilt measurements in the area. The results given can be used to provide important corrections for extracting
earthquake-related signals from observed data.
Received: 19 January 2001 / Accepted: 3 September 2001 相似文献
15.
The mechanical model for plane strain, time-harmonic seismic wave propagation problems in cracked, multi-layered geological regions with surface topography and non-parallel interfaces was described in the first part of this work. Here, this model is used to investigate the response of such a region to the presence of traveling elastic waves generated by a seismic source. The computational methodology that was developed in the first part is based on a combination of both the regular (displacement-based) and the hypersingular (traction-based) Boundary Integral Equation Method (BIEM). First, the accuracy and convergence characteristics of this hybrid BIEM are studied. Then, a series of problems involving four different configurations of a reference geological deposit with both interface and internal cracks are solved, for a loading that is due to a seismically-induced pressure wave propagating upwards from the underlying rigid half-plane. The purpose of the numerical study is to investigate the influence of various key parameters of the problem, such as frequency and incidence angle of the incoming wave, size of the surface relief, location and size of the buried cracks, interaction effects between cracks and finally the presence of layers, on both the scattered displacement field and the stress concentration field. 相似文献
16.
Analytical expressions are derived for the Poisson's ratios associated with a three-dimensional network of regular, corner-sharing
tetrahedra in which: (1) the tetrahedra are assumed to be rigid and free to rotate relative to each other; (2) the tetrahedra
are assumed to maintain shape and orientation but are free to change size (dilate); (3) tetrahedral rotation and dilation
are assumed to act concurrently. The structure has a primitive unit cell containing four tetrahedra and is analogous to the
molecular structure of α-cristobalite. Strain-dependent variations in Poisson's ratio are also predicted by the models. For
deformation due to tetrahedral rotation the network is found to exhibit negative Poisson's ratios in each of the three principal
directions, with the magnitude of the Poisson's ratio being dependent on the angle of rotation of the tetrahedra. The behaviour
of the Poisson's ratio is isotropic in the transverse plane, but anisotropic elsewhere. In the dilation model negative Poisson's
ratios equal to −1 are observed for uniaxial loading in any of the principal directions, with the value being constant irrespective
of tetrahedral size. The model for concurrent tetrahedral rotation and dilation allows positive as well as negative Poisson's
ratios, with the values determined by the framework geometry and relative strengths of the two mechanisms. The concurrent
model also offers a design route to materials and structures having ultrahigh Young's moduli.
Received: 15 February 2000 / Accepted: 1 October 2000 相似文献
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天山造山带构造环境复杂,活动断裂带和强震分布广泛,且主要分布于阿尔泰山、天山、西昆仑—帕米尔弧形构造带上,尤以天山地区最为集中.迄今为止,天山造山带地区的主要断裂带的活动特征与孕震应力场特征之间的动力学机理尚未有清晰的认识.本文以GPS等实际观测数据为约束,建立有限元数值模型,计算了研究区域地壳形变、应力/应变积累速率、弹性应变能密度以及库仑应力变化率等关键因素.模拟计算结果显示地表速度场与研究区域实际GPS观测值基本一致,且主要断裂带上弹性应变能密度分布与实际地震活动性也基本吻合,验证了数值模型和结果的可靠性.结合最新的观测和数值模拟结果分析发现,研究区的断层和地震活动性主要受控于近南北向的主压应力,与主要观测特征相一致.同时,帕米尔高原北部边界带—塔什库尔干断裂(TKF)、天山造山带南边界的东侧—迈丹断裂(MDF)、兴地断裂(XDF)库仑应力增大明显,在未来强震发生的可能性较高,应予密切关注. 相似文献
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