全文获取类型
收费全文 | 449篇 |
免费 | 94篇 |
国内免费 | 95篇 |
专业分类
大气科学 | 1篇 |
地球物理 | 157篇 |
地质学 | 395篇 |
海洋学 | 54篇 |
天文学 | 1篇 |
综合类 | 8篇 |
自然地理 | 22篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 19篇 |
2018年 | 16篇 |
2017年 | 17篇 |
2016年 | 19篇 |
2015年 | 23篇 |
2014年 | 23篇 |
2013年 | 29篇 |
2012年 | 28篇 |
2011年 | 34篇 |
2010年 | 31篇 |
2009年 | 29篇 |
2008年 | 34篇 |
2007年 | 40篇 |
2006年 | 28篇 |
2005年 | 30篇 |
2004年 | 38篇 |
2003年 | 24篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 24篇 |
1999年 | 12篇 |
1998年 | 9篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1978年 | 1篇 |
排序方式: 共有638条查询结果,搜索用时 15 毫秒
631.
Different expressions of the effective stress principle can be found in the literature, in particular some are written in finite form and others in incremental form. For the purpose of the paper we take for granted that stress–strain relationships exist or can be obtained for the effective stress coming from both formulations. We investigate the consequences of the choice of particular finite or differential forms when they are introduced in a weak form of the linear momentum balance equation of two- of three-phase porous media for its numerical solution. For partially saturated geomaterials the importance of the capillary pressure–saturation relationship is pointed out. 相似文献
632.
The effect of heterogeneity on solute transport in porous media is examined by means of physical experiments and controlled numerical simulations. The special cases of layered, clogged and aggregated porous media are particularly investigated. The breakthrough curves (BTCs) obtained from some sections of the physical models are extremely distorted with extended concentration tails. These tailings are caused by different trajectories of the tracer through fine (millimeter and centimeter) scale spatial heterogeneities. On the other hand, BTCs in sections of the physical models having no heterogeneous nature, showed classical ‘S’-shape. A computer simulation based on an improved capacitance model was used to match the experimental data. The BTCs can be represented adequately by the model. However, it seems necessary to determine the fitting parameters experimentally in order to relate them to actual physical phenomena. 相似文献
633.
634.
635.
636.
637.
在势能流及微小振幅波理论假设下,采用复合边界元素法(CBEM)数值解析规则波通过单根外壁透水cosine-type型同心圆柱结构物绕射。将cosine-type外壁不透水条件改为透水外,并在内部设有一半径为b的不透水内圆柱共同组成同心圆柱,为了验证CBEM数值模式正确性与可行性,将其退化成圆柱,均得到合理结果。数值计算条件包含波浪正向入射凸端、透水参数及绕射参数,探讨波浪通过单根cosine-type同心圆柱体四周水面波动变化情况,并与双重圆筒同心圆柱作比较。计算结果显示结构物外壁采用透水型式,可以大幅降低cosine-type同心圆柱体四周整个波浪绕射场的水面波动。 相似文献
638.
Compaction bands are localized failure patterns that appear in highly porous rock material under the effect of relatively high confining pressure. Being affected mainly by volumetric compression, these bands appear to be almost perpendicular to the most compressive principal stress of a stress state at the so-called “cap” of the yield surface (YS). In this study, we focus on the mechanism that leads to the onset of compaction bands by using a viscoplasticity model able to describe the post-localization response of these materials. The proposed constitutive framework is based on the overstress theory of Perzyna (1966) and the anisotropic clay plasticity model of Dafalias (1986), which provides not only the necessary “cap” of the YS, but introduces a rotational hardening (RH) mechanism, thus, accounting for the effect of fabric anisotropy. Following the analysis of Veveakis and Regenauer-Lieb (2015), we identify the compaction bands as “static” cnoidal wave formations in the medium that occur at a post-yield regime, and we study the effect of rotational and isotropic hardening on their onset. Moreover, we determine a theoretical range of confining pressures in triaxial compression tests for the compaction bands to develop. Under the assumption of coaxiality between stress and anisotropy tensors, the results show that the isotropic hardening promotes compaction localization, whereas the RH has a slightly negative effect on the onset of compaction localization. 相似文献