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101.
Substitute conductors for electromagnetic response estimates 总被引:3,自引:0,他引:3
Ulrich Schmucker 《Pure and Applied Geophysics》1987,125(2-3):341-367
Various concepts exist to define substitute conductors for empirical response estimates at singular frequencies: Chapman's shell-core model, the Cagniard-Tikhonov apparent resistivity, the Niblett-Bostick and Molochnov transformation, thep
* —z
* transformation. They are all interrelated and assign comparable resistivities to the substitute conductor at a given frequency. Applications to synthetic response data of plane and spherical conductors show under which conditions these substitutions come closest to the model and which influence of source dimensions and Earth's sphericity can be expected.p
* —z
* transformed global response data forS andDst variations demonstrate how substitute conductors may serve as useful guides in inverse procedures. 相似文献
102.
INTRODUCTIONAsatypicalintercontinent collisionarea ,Tibetanplateauisapresentlypopularregionnoticedbygeoscientistsallovertheworld ,sinceitisanidealandnaturallabforthestudyofthegeologicalevolutionoftheinnerlandmountain creatingzoneandoftheprocessofthecrust mantledeepdy namicsaswellasoftheinteractionbetweenthesurfaceandthecrustmovement.ThestudyoftheTibetanplateauevolutionisimportantnotonlyinsolvingsometheoreticalproblemsaboutcontinentaldynamicsandglobalchangesingeosciences ;butalsoinexplorin… 相似文献
103.
应用大地电磁测深勘查北京平谷盆地隐伏含水岩溶系统的结构 总被引:1,自引:0,他引:1
将大地电磁测深用于寻找深层地下水,在北京东部平谷盆地实施3条剖面25个测点,在资料分析过程中,对部分测点实施Mohr圆阻抗张量分解技术;在自动反演过程中,引入Rhoplus和Rebocc反演程序。通过对反演解释结果的分析,认为测区第四系地下水含量丰富,断裂构造及含水岩溶发育。对比3条剖面的电性分布特征,推测存在走向NNE的区域性断裂F1,其所经之处控制基岩中含水岩溶的发育;与F1相交的NW向次级断裂带控制了另一深部含水岩溶发育区,不同方向的含水岩溶发育区因断裂构造相通,呈现“网络”式的分布格局。 相似文献
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106.
Sounding of electrical structure of the crust and upper mantle along the eastern border of Qinghai-Tibet Plateau and its tectonic significance 总被引:2,自引:0,他引:2
Sounding and study on electrical structure of the crust and upper mantle within the eastern border region of Qinghai-Tibet Plateau by using the magnetotelluric sounding (simply MT) method permitted us to understand the characteristics of specific electrical structure in the region. The sounding result clearly revealed that: (1) The Xianshuihe fault zone represents a large-scale lithospheric fault and is an important boundary fault of the rhombic Sichuan-Yunnan block. (2) The sounded region is a strong earthquake-prone zone. The different crustal media of blocks on both sides of the fault became an important deep background for the strong seismo-active zone. (3) A large-scale low-resistivity layer is found to exist at a depth more than ten kilometers beneath the northern part of the rhombic Sichuan-Yunnan block. Its electrical resistivity is only several to tens Ω?m. The layer northeastward extends down at an angle of 45°. It is related to an obstacle to the lateral squeeze of Qinghai-Tibet Plateau and eastward flow of mass by the rigid block. It is inferred from the characteristics of electrical property of deep media that the northern part of the recent rhombic Sichuan-Yunnan block is in a thermal state and is one of the recently fairly active blocks. (4) The lithosphere in the sounded region is gradually thickened from the western segment (northern Sichuan-Yunnan block) to east (Yangtze block). 相似文献
107.
108.
On Two-Dimensional Modeling Of Magnetotelluric Field Data 总被引:5,自引:0,他引:5
Yasuo Ogawa 《Surveys in Geophysics》2002,23(2-3):251-273
In this paper, some recent topics on the modeling of magnetotelluric data are introduced. The focus is on the handling of real field data for two-dimensional resistivity modeling. First, the removal of the effects of near surface heterogeneity is reviewed. It covers telluric distortions (phase mixing and static shift) and magnetic distortions using conventional Groom-Bailey type 3D/2D model (three-dimensional local anomaly underlain by regional two-dimensional structure). The extension of a 3D/2D distortion model for multi-site, multi-frequency is a new development. Magnetic distortion seems to be less significant for land observations, but significant for sea floor data, where the regional magnetic field is weak due to seawater. In special cases involving for example, distortion due to topography and bathymetry, explicit removal is possible. There are some schemes proposed for a 3D/3D model (three-dimensional local anomaly underlain by regional three-dimensional structure). Along with the removal of the distortion, it is important to recognize the dimensionality of the dataset prior to modeling. A property using strike estimates for each site is an indicator for dimensionality which is unaffected by local distortion. Mapping the local strike or a rose diagram is an effective visualization of the dimensionality.Two-dimensional inversion is becoming routine. For the fast calculation of derivatives, approximate calculation, reciprocity or conjugate gradient methods are used. In order to incorporate a priori information and to overcome the intrinsic ill-posed nature of the inversion problem, imposing constraints on the model structure is important. A proper tradeoff between the data fit and constraints should be optimized to obtain minimum structures that are required by the field data. However, the choice of constraints is rather subjective and depends on the geological situations. For field data, two-dimensional inversion has limits on modes, area, and period range. Special care must be taken for the structure outside the profile. Two-dimensional inversion incorporating anisotropy is interesting and becoming popular, but the structure may not be unique. Future development in three-dimensional inversion for real datasets should take the above points into consideration. 相似文献
109.
110.