全文获取类型
收费全文 | 201篇 |
免费 | 25篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 18篇 |
地球物理 | 37篇 |
地质学 | 111篇 |
海洋学 | 18篇 |
天文学 | 1篇 |
综合类 | 16篇 |
自然地理 | 31篇 |
出版年
2022年 | 4篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 5篇 |
2016年 | 3篇 |
2015年 | 12篇 |
2014年 | 13篇 |
2013年 | 11篇 |
2012年 | 4篇 |
2011年 | 13篇 |
2010年 | 9篇 |
2009年 | 17篇 |
2008年 | 18篇 |
2007年 | 13篇 |
2006年 | 11篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 8篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 8篇 |
1997年 | 3篇 |
1996年 | 5篇 |
1995年 | 4篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 5篇 |
1985年 | 1篇 |
1980年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有243条查询结果,搜索用时 187 毫秒
81.
82.
It is well known that the trial process for seeking the safety factor in the shear strength reduction finite element method (SSRFEM) is quite expensive, particularly for large 3-D slope stability analyses. The search algorithm for the safety factor is crucial to the entire solution process for the shear strength reduction finite element method, but few studies have attempted to exploit it. Among search algorithms, the commonly used bracketing and bisection search has not been fully optimised. Consequently, to improve the search scheme for the safety factor associated with the shear strength reduction finite element method, two strategies are suggested. First, a generalised bisection search algorithm is proposed to reduce the possibility of encountering non-convergence from a statistical point of view. To further improve the efficiency, a new two-grid scheme, characterised by a coarse mesh search and followed by a fine mesh search, is developed. Based on the drained or undrained analyses of the 3-D slope examples, the new search algorithm can markedly outperform the commonly used bisection search algorithms based on a single finite element mesh. 相似文献
83.
84.
85.
86.
The problem of permeable reactive barrier (PRB) capture and release behavior is investigated by means of an approximate analytical approach exploring the invariance of steady-state solutions of the advection–dispersion equation to conformal mapping. PRB configurations considered are doubly-symmetric funnel-and-gate as well as less frequent drain-and-gate systems. The effect of aquifer heterogeneity on contaminant plume spreading is hereby incorporated through an effective transverse macro-dispersion coefficient, which has to be known. Results are normalized and graphically represented in terms of a relative capture efficiency M of contaminant mass or groundwater passing a control plane (transect) at a sufficient distance up-stream of a PRB as to comply with underlying assumptions. Factors of safety FS are given as the ratios of required capture width under advective–dispersive and purely advective transport for achieving equal capture efficiency M. It is found that M also applies to the release behavior down-stream of a PRB, i.e., it describes the spreading and dilution of PRB treated groundwater possibly containing incompletely remediated contamination and/or remediation reaction products. Hypothetical examples are given to demonstrate results. 相似文献
87.
Gosavi Meenal Swami Saran Satyendra Mittal 《Geotechnical and Geological Engineering》2009,27(4):571-583
In this paper, a pseudo-static analysis has been presented to investigate the stability of soil nailed vertical/nearly vertical
excavations. The failure surface is assumed as the arc of log-spiral passing through the toe of the excavation and intersecting
the ground at right angle. The horizontal and vertical seismic forces are taken in terms of horizontal and vertical seismic
coefficients. The internal failure mode of the nailed cut is considered either by pull-out or rupture or excessive bending
whichever is critical. Expression for the factor of safety is derived using moment equilibrium method. Results have been arranged
in tabular form considering ranges of the design parameters usually occur in practice. A typical table for the design of nailed
excavation with driven nails is presented in the paper. Analytical results have been compared with the findings of model tests
and reasonably good agreement has been observed. 相似文献
88.
S. Sreekumar 《Journal of the Geological Society of India》2009,73(6):813-820
The occurrences of slope failures are frequent in Idukki district of Kerala state particularly along the road cuttings and
hill slopes causing disruption in traffic, loss of lives and property. This demands a critical evaluation of stability of
slopes along the hill roads. This paper deals with stability analysis of a typical hard rock profile at Chuzhappu and a lateritic
profile at Kumili along the road connecting Kottayam and Kumili. A large number of factors have been examined and studied;
the orientation of discontinuities has been identified as one of the major inherent factors influencing slope instability
along Chuzhappu hard rock profile. These have been analysed carefully using stereographic/equal area projection technique
in order to determine the vulnerability to slope failure and to understand the type of rock slide that can occur in this profile.
The buoyant force of water acting along the discontinuities after heavy rain storm further aids the down slope movement. As
the laterite slope is mostly homogeneous, Bishops method and Swedish method were adopted for stability analysis of laterite
slope at Kumili. The study also examines the efficacy and applicability of the different methods employed in soil mechanics
to assess the stability of laterite slope.The results obtained by this method are compared by actual field conditions. The
stability assessment indicates that two sectors at Chuzhappu and one sector at Kumili profile are at the geo-technical threshold
of failure, when piezometric head rises during rainstorm. The study indicates that these methods are highly useful in determining
the Factor of Safety in profiles with similar geological setting. 相似文献
89.
By using the modified pseudo-dynamic method for submerged soils this paper explores the seismic stability of seawall for the active condition of earth pressure. Different forces such as seismic active earth pressure, seismic inertia forces of the wall, non-breaking wave pressure, hydrostatic and hydrodynamic pressures are considered in the stability analysis. Limit equilibrium has been used, and expressions for the factor of safety against sliding and overturning mode of failure have been proposed. The proposed methodology overcomes the limitations of existing pseudo-dynamic method for submerged soils. A detailed parametric study has been conducted by varying different parameters and results are presented in the form of design charts for computation of factor of safety against sliding and overturning mode of failures. It was noticed that the influences of soil friction angle, seismic acceleration coefficient, wall inclination and excess pore pressure are significant when compared to the other parameters. The value of factor of safety against the sliding mode of failure is increasing by about 62% when the value of soil frictional angle is increased from 30° to 40°. It was also found that the factor of safety against overturning mode of failure is decreasing by about 22% as the value of excess pore pressure ratio increases from 0 to 0.75. The proposed method with closed-form solutions can be used for the seismic design of seawalls. 相似文献
90.
Shiv Mohan Singh Kumar Avinash Parmanand Sharma Ravindra Uttam Mulik Ajay Kumar Upadhyay Rasik Ravindra 《地学前缘(英文版)》2017,8(6):1339-1347
Cryoconite samples were collected from two different climatic domains i.e., the Sutri Dhaka glacier, western Himalaya India and Svalbard glaciers, the Spitsbergen, Arctic, to understand the elemental source and elemental deposition patterns. The data of geochemical analysis suggest that the Himalayan cryoconite samples accumulate higher concentrations as compared to the cryoconite samples of the Arctic glaciers. The concentration of lithophile elements (Cs, Li, Rb and U) was recorded higher in the cryoconite holes of the Himalayas, especially, in the lower to the higher parts of the glacier, whereas, lower concentrations were recorded in the Arctic samples. Chalcophile elements in the Himalayan cryoconites are enriched in As and Bi while the Arctic cryoconite samples show a higher concentration of Bi, Pb and As. The higher concentrations are responsible for influencing the ecosystem and in human health related issues. Siderophile elements (Co, Fe, Mn and Ni) show high concentrations in the Himalayan samples, whereas, the Arctic samples show minor variations and low elemental concentration in these elements, respectively. In addition, a few elements, such as Ag, Mg, and Ca show higher concentration in the Himalayan glacier samples. Ca also occurs in high concentrations in Arctic glacier samples. R-mode factor analysis of the Himalayas (Arctic) samples indicate that the elements are distributed in four (three) factors, explaining 89% (90%) of the variance in their elemental distribution. The Factor 1 suggests statistically significant positive loadings for most of the lithophile, chalcophile and siderophile elements of the “Himalayan” and the Arctic cryoconite samples. The sample-wise factor score distribution shows a considerable variation in the sampling locations along the glaciers of both the regions. Factors 2 and 3, demonstrate insignificant loading for most of the elements, except statistically significant positive loading in some of the elements of the both, Himalayan and Arctic “cryoconites”. The higher elemental concentration in the cryoconites of the Himalayan region may be an indicator of the natural processes and/or attributed to the rapid industrialization in the Asian countries. 相似文献