全文获取类型
收费全文 | 212篇 |
免费 | 11篇 |
国内免费 | 4篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 17篇 |
地球物理 | 66篇 |
地质学 | 108篇 |
海洋学 | 9篇 |
天文学 | 4篇 |
综合类 | 6篇 |
自然地理 | 8篇 |
出版年
2024年 | 2篇 |
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 6篇 |
2020年 | 8篇 |
2019年 | 12篇 |
2018年 | 17篇 |
2017年 | 21篇 |
2016年 | 20篇 |
2015年 | 15篇 |
2014年 | 20篇 |
2013年 | 32篇 |
2012年 | 13篇 |
2011年 | 19篇 |
2010年 | 5篇 |
2009年 | 4篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 2篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 3篇 |
1998年 | 2篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1986年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有227条查询结果,搜索用时 15 毫秒
91.
A new remediation technique is proposed to mitigate large deformations imposed on buried pipeline systems subject to permanent ground deformation. With this technique, low-density gravel(LDG) with high porosity, such as pumice,is used as backfill in the trench containing the pipe near an area susceptible to PGD. This countermeasure decreases soil resistance, soil-pipe interaction forces and strain on the pipe as the pipeline deformation mechanism changes to a more desirable shape. Expanded polys... 相似文献
92.
Secondary circulation induced by flow curvature and Coriolis effects around headlands and islands 总被引:1,自引:1,他引:0
Previous studies have shown that flow curvature in river bends generates a secondary circulation in the plane normal to the mean flow direction. A similar circulation pattern is shown to exist in oceanic situations when flows are subject to curvature, mainly due to interaction with topographic features. However, it is shown that, due to differences between oceanic conditions and river bends, theory and prediction methods based on the assumptions for river bends are invalid for oceanic flows. Via scaling arguments based on the equations of motion, that include both the effects of flow curvature and the Coriolis force, parameters that govern the different flow regimes are identified. The maximum strength of the secondary flow is derived for each flow regime and is verified using a three-dimensional (3-D) numerical model applied to an idealized island. It is also shown that upwelling, due to the generation of secondary flow, occurs off the tips of the headland or island, and its influence can extend far downstream.Responsible Editor: Richard Signell 相似文献
93.
94.
95.
96.
97.
This paper presents a numerical scheme for fluid‐particle coupled discrete element method (DEM), which is based on poro‐elasticity. The motion of the particles is resolved by means of DEM. While within the proposition of Darcian regime, the fluid is assumed as a continuum phase on a Eulerian mesh, and the continuity equation on the fluid mesh for a compressible fluid is solved using the FEM. Analytical solutions of traditional soil mechanics examples, such as the isotropic compression and one‐dimensional upward seepage flow, were used to validate the proposed algorithm quantitatively. The numerical results showed very good agreement with the analytical solutions, which show the correctness of this algorithm. Sensitivity studies on the effect of some influential factors of the coupling scheme such as pore fluid bulk modulus, volumetric strain calculation, and fluid mesh size were performed to display the accuracy, efficiency, and robustness of the numerical algorithm. It is revealed that the pore fluid bulk modulus is a critical parameter that can affect the accuracy of the results. Because of the iterative coupling scheme of these algorithms, high value of fluid bulk modulus can result in instability and consequently reduction in the maximum possible time‐step. Furthermore, the increase of the fluid mesh size reduces the accuracy of the calculated pore pressure. This study enhances our current understanding of the capacity of fluid‐particle coupled DEM to simulate the mechanical behavior of saturated granular materials. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
98.
99.
Majid Mathlouthi Fethi Lebdi 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):513-528
The paper focuses on the development of reservoir operating rules for dry and rainfall events, and their implementation in
the case of the Ghézala dam located in northern Tunisia (characterized by Mediterranean climate). Rainfall events are defined
in terms of depth and duration that are correlated to each other. A depth analysis per event is performed, conditioned on
the event duration. The gamma distribution provides a good fit to depth per event, especially for events lasting at least
6 days. The event duration fits a geometric distribution, whereas the dry events during the rainy season fit a negative binomial
distribution. The climatic cycle length is fitted to a gamma distribution. On this basis, many 50-year synthetic event series
were generated. Every synthetic streamflow sequence obtained from synthetic rainfall sequences as well as the one derived
from the historic rainfall events time series were optimized and optimal decisions were formulated. These decisions were assessed
by means of multiple regression analysis to estimate the relation between the optimal decision to every stage (dry or rainfall
event) and other system variables. Optimal rules, which have a linear form, were derived by predetermined useful storage interval
and depend on storage, inflows and downstream demand at dry or rainfall event t. The range of t is 1–13 days (rainfall event) and 1–57 days (dry event). The rules were satisfactory for every predetermined useful storage
interval. The simulated dam performance generated by the operation rules was compared with the deterministic optimum operation
and the historical operation. Also included is the comparison of the implicit stochastic optimization-based operation policy
per event during the water years 1985–2002.
相似文献
Fethi LebdiEmail: |
100.