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151.
152.
In this technical note, the phenomena of non-linear water-wave propagation above a seabed with variable depth is re-examined. The conventional Korteweg-de Vries (KdV) equation is re-derived for the general case of variable water depth. In the new form of KdV equation, the seabed bottom function is included. Two different bottom profiles are considered in this study; case 1: and case 2: . The effects of three bottom profile parameters, c, λ and ε on the wave profile are examined. Numerical results indicate that both ε and λ affect the wave profile significantly in case 1, while ε significantly affects the wave profile in case 2. 相似文献
153.
154.
杭州某污水处理厂双线圆形管道拟采用顶管隧道施工方案,分别用plaxis软件进行有限元分析和经验法计算得到顶管隧道穿越钱江二桥铁路桥梁引起的地面变形、桩基变形、桩基承载力影响大小数据。结果证明顶管穿越铁路桥,对桥梁影响较小。 相似文献
155.
In this paper an adaptive algorithm for Smoothed Particle Hydrodynamics (SPH) for the Shallow Water Equations (SWEs) is presented. The area of a particle is inversely proportional to depth giving poor resolution in small depths without particle refinement. This is a particular limitation for flooding problems of interest here. Higher resolution is created by splitting the particles, while particle coalescing (or merging) improves efficiency by reducing the number of the particles when acceptable. The new particle coalescing procedure merges two particles together if their area becomes less than a predefined threshold value. Both particle splitting and coalescing procedures conserve mass and momentum and the smoothing length of new particles is calculated by minimizing the density error of the SPH summation. The new dynamic particle refinement procedure is assessed by testing the numerical scheme against analytical, experimental and benchmark test cases. The analytical cases show that with particle splitting and coalescing typical convergence rates remain faster than linear. For the practical test case, in comparison to using particle splitting alone, the particle coalescing procedure leads to a significant reduction of computational time, by a factor of 15. This makes the computational time of the same order as mesh-based methods with the advantage of not having to specify a mesh over a flood domain of unknown extent a priori. 相似文献
156.
多光谱浅海水深提取方法研究 总被引:4,自引:0,他引:4
利用我国南海某岛礁的TM数据和实测水深资料,试验性地研究了一种在不同底质反射条件下多光谱定量提取水深信息的方法,计算了浅海岛礁水深,取得了较好的应用效果和较高的测深精度. 相似文献
157.
通过对三峡地区小台网地震观测和资料研究,认识到该区弹性波地动位移振幅随震中距增加而衰减的变化偏大,地震数字记录的S波波谱分析表明其拐角频率高达21.9Hz,功率谱极大区在0.5~26Hz间,该地区的地震烈度、震中烈度和等震线长轴长度分布具有一定的离散性。上述现象属于极浅源地震波的近场地表效应。研究这些效应特点,可为国家经济建设提供防震、抗震依据 相似文献
158.
郯庐断裂带莱州湾段的构造特征 总被引:5,自引:1,他引:5
本文利用海上浅层地震勘探剖面分析了郯庐断裂带莱州湾段的上更新统、全新统和活动构造的某些特征。晚更新世末期发生的构造运动使上更新统产生断裂与褶皱,沿郯庐断裂带东主干断裂发育了狭长的背斜构造,在西主干断裂两侧次级横向(东西向)断裂十分发育,这些横向断裂是一些高角度的张性正断层。 相似文献
159.
Gravity observations from superconducting gravimeters are used to observe loading effects from shallow-water tides on the Japanese east and west coasts. Non-linear third-diurnal and higher-frequency shallow-water tides are identified in the tide-gauge observations from these coastal areas. The most energetic constituents in the tide gauge observations are also seen in the gravity observations due to their loading effects on the deformation of the Earth. Even though the shallow-water tides at the Japanese east coast have an amplitude of only a few millimetres, they are still able to generate a loading signal at gravity sites located several hundred kilometres inland. In particular, the S3, S4 and S5 solar tides occur in both gravity and tide gauge observations. It is indicated that in other shelf regions with large shallow water tides, the shallow water loading signals account for a significant signal, which should be taken into account.Acknowledgement The authors would like to thank the Hydrographic and Oceanographic Department (Japan Coast Guard), Japan Meteorological Agency and Hokkaido Development Agency for access to the tide-gauge data. Also, the Global Geodynamic Project Information System and Data Center (GGP-ISDC) is acknowledged for providing the gravity data. 相似文献
160.
We try to find how often, and in what regions large earthquakes (M≥7.0) occur within the shallow portion (20-60 km depth) of a subducting slab. Searching for events in published individual studies and the Harvard University centroid moment tensor catalogue, we find twenty such events in E. Hokkaido, Kyushu-SW, Japan, S. Mariana, Manila, Sumatra, Vanuatu, N. Chile, C. Peru, El Salvador, Mexico, N. Cascadia and Alaska. Slab stresses revealed from the mechanism solutions of these large intraslab events and nearby smaller events are almost always down-dip tensional. Except for E. Hokkaido, Manila, and Sumatra, the upper plate shows horizontal stress gradient in the arc-perpendicular direction. We infer that shear tractions are operating at the base of the upper plate in this direction to produce the observed gradient and compression in the outer fore-arc, balancing the down-dip tensional stress of the slab. This tectonic situation in the subduction zone might be realized as part of the convection system with some conditions, as shown by previous numerical simulations. 相似文献