全文获取类型
| 收费全文 | 133篇 |
| 免费 | 42篇 |
| 国内免费 | 18篇 |
专业分类
| 测绘学 | 30篇 |
| 大气科学 | 13篇 |
| 地球物理 | 33篇 |
| 地质学 | 51篇 |
| 海洋学 | 45篇 |
| 天文学 | 1篇 |
| 综合类 | 10篇 |
| 自然地理 | 10篇 |
出版年
| 2022年 | 2篇 |
| 2021年 | 4篇 |
| 2020年 | 6篇 |
| 2019年 | 5篇 |
| 2018年 | 5篇 |
| 2017年 | 13篇 |
| 2016年 | 5篇 |
| 2015年 | 13篇 |
| 2014年 | 7篇 |
| 2013年 | 10篇 |
| 2012年 | 10篇 |
| 2011年 | 16篇 |
| 2010年 | 9篇 |
| 2009年 | 8篇 |
| 2008年 | 10篇 |
| 2007年 | 12篇 |
| 2006年 | 12篇 |
| 2005年 | 7篇 |
| 2004年 | 3篇 |
| 2003年 | 6篇 |
| 2002年 | 5篇 |
| 2001年 | 1篇 |
| 2000年 | 4篇 |
| 1999年 | 4篇 |
| 1996年 | 2篇 |
| 1995年 | 3篇 |
| 1994年 | 2篇 |
| 1993年 | 2篇 |
| 1991年 | 1篇 |
| 1990年 | 1篇 |
| 1989年 | 1篇 |
| 1987年 | 4篇 |
排序方式： 共有193条查询结果，搜索用时 499 毫秒
91.
为了改进计算区域离散化问题,本文利用自适应非结构化网格有限单元法求解二维地电结构下大地电磁场满足的加权余量表达式。在有限元求解电磁场的过程中,网格剖分越精细、计算精度越高,计算量也会越大。此外,结构化网格难以适应任意地形以及复杂地质构造。而自适应非结构化网格在电性变化剧烈的区域会自动加密,在电性缓变的区域则生成粗疏的网格,从而优化网格质量与数量。因此,文中引入COMSOL Multiphysics软件,以实现若干地电模型的构建及非结构化自由四边形单元网格化。将网格数据信息导入本文算法,计算大地电磁场响应,并与解析解及数值解对比。结果表明,基于非结构化网格的正演模拟精度高、适应性强,为计算区域网格化提供了新的方法。 相似文献
92.
基于广义垂线坐标变换,构建了非结构网格的三维水动力数学模型。模型采用半隐式有限体积法对控制方程进行数值离散,其中半隐式法用于水位梯度和垂向紊动扩散以及垂向对流项的离散,显式控制体积分法用于水平对流项等的离散。广义垂线坐标系使得模型能够灵活地对垂向网格进行布置,平面非结构网格使得模型能够适应河口海岸复杂的岸线,并可对局部进行网格加密。模型通过具有解析解的风生流和异重流对模型进行检验,应用模型模拟了珠江口的三维潮流过程,计算结果与实测水文数据的比较表明,模型能够较好地模拟珠江河口的盐水楔和三维分层水动力过程。 相似文献
93.
Al-Mg granulites, with cordierite, garnet, sapphirine, orthopyroxene, sillimanite, spinel, phlogopite, K-feldspar, plagioclase and variable quartz from Ihouhaouene (In Ouzzal, Algeria), display a range of decompression textures involving the breakdown of orthopyroxene and sillimanite, and of garnet. The succession of parageneses suggests that the P–T–t evolution corresponds to decompression with cooling from peak conditions of about 950°C and 10 kbar. This decompression path is obtained from the paragenetic analysis in the FMAS system. However, according to current KFMASH grids, this P–T–t evolution should take place outside the stability field of phlogopite+quartz; yet this assemblage is probably stable during most of the P-T evolution, notably during peak metamorphism. This discrepancy is interpreted as the effect of the high content of F in phlogopite which should shift its stability limit towards higher temperature. The consequences of this shift on the phase relationships in the KFeMASH system are investigated and it is concluded that a topological inversion could exist in the F-bearing system. 相似文献
94.
Wells are seldom modeled explicitly in large scale finite difference reservoir simulations. Instead, the well is coupled to the reservoir through the use of a well index, which relates wellbore flow rate and pressure to grid block quantities. The use of an accurate well index is essential for the detailed modeling of nonconventional wells; i.e., wells with an arbitrary trajectory or multiple branches. The determination of a well index for such problems is complicated, particularly when the simulation grid is irregular or unstructured. In this work, a general framework for the calculation of accurate well indices for general nonconventional wells on arbitrary grids is presented and applied. The method entails the use of an accurate semianalytical well model based on Green's functions as a reference single phase flow solution. This result is coupled with a finite difference calculation to provide an accurate well index for each grid block containing a well segment. The method is demonstrated on a number of homogeneous example cases involving deviated, horizontal and multilateral wells oriented skew to the grid. Both Cartesian and globally unstructured multiblock grids are considered. In all these cases, the method is shown to provide results that are considerably more accurate compared to results using standard procedures. The method is also applied to heterogeneous problems involving horizontal wells, where it is shown to be capable of approximating the effects of subgrid heterogeneity in coarse finite difference models. 相似文献
95.
数值模拟研究紊流问题的关键是充分考虑雷诺应力的差异,应用各向异性三维代数应力紊流数学模型(ASM)模拟研究了天然河道的次生流问题。以方形管道为算例与试验的比较表明,所应用的ASM模型精度较高;将ASM与非结构网格有机结合模拟分析河道复杂采砂坑,计算成果与前人结果类比,令人满意。ASM模型为研究河床稳定与变形提供了有力工具。分析表明,采砂坑使原稳定的水流形态发生变化,沿主流方向形成纵向涡旋导致采砂坑上游缘口冲刷,坑内的横向次生流则造成横向侵蚀;紊动特性研究表明采砂坑严重影响河床稳定。 相似文献
96.
97.
变质火山岩、火山碎屑岩的绿片岩相成岩格子可用阳起石—黑云母—方解石—绿泥石—绿帘石—白云母六相三元系和钠长石—阳起石—黑云母—方解石—绿泥石—绿帘石六相三元系成岩格子来表示,石英往往为过剩组分。在只讨论两个强度相同的变量前提下,每个六相三元系的成岩格子都只可能有一对成对的成岩格子,且这对成岩格子的非封闭双变区的分区相同、分区之间的边界斜率相同、相应的单变线的排列顺序也相同,因此,六相三元系的每个成岩格子中的不变点数、单变线数、和双变区数之间的关系可用数学式来表示。 相似文献
98.
99.
Multiple-point simulation, as opposed to simulation one point at a time, operates at the pattern level using a priori structural information. To reduce the dimensionality of the space of patterns we propose a multi-point filtersim algorithm that classifies structural patterns using selected filter statistics. The pattern filter statistics are specific linear combinations of pattern pixel values that represent directional mean, gradient, and curvature properties. Simulation proceeds by sampling from pattern classes selected by conditioning data. 相似文献
100.