全文获取类型
收费全文 | 2309篇 |
免费 | 143篇 |
国内免费 | 90篇 |
专业分类
测绘学 | 96篇 |
大气科学 | 122篇 |
地球物理 | 592篇 |
地质学 | 1156篇 |
海洋学 | 106篇 |
天文学 | 298篇 |
综合类 | 29篇 |
自然地理 | 143篇 |
出版年
2024年 | 6篇 |
2023年 | 14篇 |
2022年 | 60篇 |
2021年 | 71篇 |
2020年 | 74篇 |
2019年 | 88篇 |
2018年 | 177篇 |
2017年 | 150篇 |
2016年 | 212篇 |
2015年 | 107篇 |
2014年 | 221篇 |
2013年 | 249篇 |
2012年 | 112篇 |
2011年 | 139篇 |
2010年 | 98篇 |
2009年 | 104篇 |
2008年 | 83篇 |
2007年 | 51篇 |
2006年 | 69篇 |
2005年 | 41篇 |
2004年 | 27篇 |
2003年 | 30篇 |
2002年 | 32篇 |
2001年 | 25篇 |
2000年 | 20篇 |
1999年 | 13篇 |
1998年 | 21篇 |
1997年 | 17篇 |
1996年 | 9篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1992年 | 16篇 |
1991年 | 5篇 |
1990年 | 11篇 |
1989年 | 14篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 6篇 |
1983年 | 8篇 |
1982年 | 14篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 11篇 |
1974年 | 5篇 |
1973年 | 8篇 |
1972年 | 5篇 |
排序方式: 共有2542条查询结果,搜索用时 625 毫秒
71.
72.
73.
74.
75.
Volcanism along the northwest boundary of the Arabian Plate found in the Gaziantep Basin, southeast Turkey, is of Miocene age and is of alkaline and calc-alkaline basic composition. The rare earth element data for both compositional series indicates spinel–peridotite source areas. The rare earth and trace elements of the alkaline lavas originate from a highly primitive and slightly contaminated asthenospheric mantle; those of the calc-alkaline lavas originate from a highly heterogeneous, asthenospheric, and lithospheric mantle source. Partial melting and magmatic differentiation processes played a role in the formation of the petrological features of these volcanics. These rocks form two groups on the basis of their ~(87) Sr/~(86) Sr and ~(143) Nd/~(144) Nd isotopic compositions in addition to their classifications based on their chemical compositions(alkaline and calc-alkaline). These isotopic differences indicate a dissimilar parental magma. Therefore, high Nd isotope samples imply a previously formed and highly primitive mantle whereas low Nd isotope samples may indicate comparable partial melting of an enriched heterogeneous shallow mantle. Other isotopic changes that do not conform to the chemical features of these lavas are partly related to the various tectonic events of the region, such as the Dead Sea Fault System and the Bitlis Suture Zone. 相似文献
76.
Shahid Manzoor Michael G. Edwards Ali H. Dogru Tareq M. Al-Shaalan 《Computational Geosciences》2018,22(1):195-230
Grid generation for reservoir simulation must honor classical key constraints and be boundary aligned such that control-volume boundaries are aligned with geological features such as layers, shale barriers, fractures, faults, pinch-outs, and multilateral wells. An unstructured grid generation procedure is proposed that automates control-volume and/or control point boundary alignment and yields a PEBI-mesh both with respect to primal and dual (essentially PEBI) cells. In order to honor geological features in the primal configuration, we introduce the idea of protection circles, and to generate a dual-cell feature based grid, we construct halos around key geological features. The grids generated are employed to study comparative performance of cell-centred versus cell-vertex control-volume distributed multi-point flux approximation (CVD-MPFA) finite-volume formulations using equivalent degrees of freedom. The formulation of CVD-MPFA schemes in cell-centred and cell-vertex modes is analogous and requires switching control volume from primal to dual or vice versa together with appropriate data structures and boundary conditions. The relative benefits of both types of approximation, i.e., cell-centred versus vertex-centred, are made clear in terms of flow resolution and degrees of freedom required. 相似文献
77.
Katerina Georgiou John Harte Ali Mesbah William J. Riley 《Computational Geosciences》2018,22(3):851-865
We present a numerical method for solving a class of systems of partial differential equations (PDEs) that arises in modeling environmental processes undergoing advection and biogeochemical reactions. The salient feature of these PDEs is that all partial derivatives appear in linear expressions. As a result, the system can be viewed as a set of ordinary differential equations (ODEs), albeit each one along a different characteristic. The method then consists of alternating between equations and integrating each one step-wise along its own characteristic, thus creating a customized grid on which solutions are computed. Since the solutions of such PDEs are generally smoother along their characteristics, the method offers the potential of using larger time steps while maintaining accuracy and reducing numerical dispersion. The advantages in efficiency and accuracy of the proposed method are demonstrated in two illustrative examples that simulate depth-resolved reactive transport and soil carbon cycling. 相似文献
78.
Farid Asam Khalid Perveiz Ali Muhammad Y. Iqbal Muhammad Asim Jadoon Khan Zaib 《International Journal of Earth Sciences》2018,107(5):1557-1578
International Journal of Earth Sciences - Regional seismic reflection profiles, deep exploratory wells, and outcrop data have been used to study the structure and stratigraphic architecture of the... 相似文献
79.
H. Hajinezhad Ali R. Soheili Mohammad R. Rasaei F. Toutounian 《Computational Geosciences》2018,22(6):1433-1444
In this paper, the numerical methods for solving the problem of steam injection in the heavy oil reservoirs are presented. We consider a 3-dimensional model of 3-phase flow, oil, water, and steam, with the effect of 3-phase relative permeability. Interphase mass transfer of water and steam is considered; oil is assumed nonvolatile. We apply the simultaneous solution approach to solve the corresponding nonlinear discretized partial differential equation in the fully implicit form. The convergence of finite difference scheme is proved by the Rosinger theorem. The heuristic Jacobian-Free-Newton-Krylov (HJFNK) method is proposed for solving the system of algebraic equations. The result of this proposed numerical method is well compared with some experimental results. Our numerical results show that the first iteration of the full approximation scheme (FAS) provides a good initial guess for the Newton method. Therefore, we propose a new hybrid-FAS-HJFNK method while there is no steam in the reservoir. The numerical results show that the hybrid-FAS-HJFNK method converges faster than the HJFNK method. 相似文献
80.
International Journal of Earth Sciences - This study reports on spectacular deformation structures, including arrays of striated thrusts, discovered by excavation work in Holocene deposits in... 相似文献