全文获取类型
收费全文 | 2058篇 |
免费 | 380篇 |
国内免费 | 450篇 |
专业分类
测绘学 | 93篇 |
大气科学 | 133篇 |
地球物理 | 886篇 |
地质学 | 1167篇 |
海洋学 | 252篇 |
天文学 | 86篇 |
综合类 | 86篇 |
自然地理 | 185篇 |
出版年
2024年 | 7篇 |
2023年 | 31篇 |
2022年 | 39篇 |
2021年 | 56篇 |
2020年 | 68篇 |
2019年 | 80篇 |
2018年 | 68篇 |
2017年 | 86篇 |
2016年 | 103篇 |
2015年 | 101篇 |
2014年 | 117篇 |
2013年 | 122篇 |
2012年 | 112篇 |
2011年 | 118篇 |
2010年 | 96篇 |
2009年 | 120篇 |
2008年 | 130篇 |
2007年 | 141篇 |
2006年 | 133篇 |
2005年 | 120篇 |
2004年 | 112篇 |
2003年 | 96篇 |
2002年 | 91篇 |
2001年 | 57篇 |
2000年 | 92篇 |
1999年 | 101篇 |
1998年 | 65篇 |
1997年 | 56篇 |
1996年 | 67篇 |
1995年 | 54篇 |
1994年 | 36篇 |
1993年 | 45篇 |
1992年 | 23篇 |
1991年 | 20篇 |
1990年 | 23篇 |
1989年 | 18篇 |
1988年 | 13篇 |
1987年 | 14篇 |
1986年 | 12篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1977年 | 17篇 |
1974年 | 1篇 |
1954年 | 3篇 |
排序方式: 共有2888条查询结果,搜索用时 453 毫秒
891.
《Geomechanics and Geoengineering》2013,8(2):65-75
A simplified method to analyse diffuse and localized bifurcations of sand under drained and undrained conditions is presented in this paper. This method utilizes results from bifurcation analysis and critical state plasticity theory to detect the onset of pure and dilatant shear band formation, static liquefaction and drained shear failures systematically. To capture the soil collapse observed in experiments, the instability state line concept originated by Chu, Lo and Lee in 1993 is adopted. Emphasis is given to examine how the presence of pore-fluid may facilitate or delay instability after yielding occurs. The predictions of instabilities are compared with experimental data from triaxial compression tests on Toyoura and Changi sands. 相似文献
892.
893.
《Geomechanics and Geoengineering》2013,8(1):61-74
A simple unified critical state constitutive model for bonded geomaterials is presented in this paper. The model, which is called CASM-n, is an enhancement of an existing unified critical state model for reconstituted geomaterials (CASM). Characteristic behaviours of a bonded geomaterial such as the pre-yield higher strength and stiffness and the cohesive–frictional shearing mode in the post-yield region are taken into account and included in the reference model. The salient feature of the proposed model is the incorporation of cohesive component into the stress–dilatancy relationship. Consideration of the contribution of cohesion to plastic flow allows the modelling of delayed dilatancy and softening–contraction behaviour, which are two interesting phenomena observed in bonded geomaterials. 相似文献
894.
Eurocode 7, the new European standard for geotechnical design, is based on the limit state design method, with partial factors and characteristic parameter values. An objective of the Eurocodes is that the chosen partial factors should achieve reliability levels for a structure close to a prescribed target value. The target ultimate limit state reliability index for a medium risk structure for 50 years is 3.8. This paper examines the reliability of an inclined-eccentrically and vertically loaded square foundation designed using all three Design Approaches in Eurocode 7 with the recommended partial factor values given in EN1997-1. The reliabilities obtained using the three Design Approaches are compared with the target reliability value and the reliabilities of traditional designs using overall factors of safety. The paper provides evidence that Eurocode 7 gives more consistent reliabilities for a greater range of parameter values than the traditional allowable stress method and demonstrates the importance of selecting appropriate characteristic values. 相似文献
895.
896.
滇东—黔西地区煤层气构造特征 总被引:6,自引:3,他引:6
煤层气在成煤过程中生成,并主要以煤层为储层的非常规天然气,通常甲烷组分占绝大部分,故亦称为煤层甲烷。甲烷以分子吸附状态,赋存于煤基质的巨大内表面上。滇东-黔西地区煤层气资源丰富,开发煤层气资源,为该区的经济腾飞将起到极大的推动作用。煤层气的勘探开发,须要研究形成煤层气的聚煤盆地的地质构造。地壳地质和深部构造是一个统一的整体。通过该区重力、磁力异常、TM遥感影像、古今地应力场研究,滇东-黔西地区,莫 相似文献
897.
板内应力场研究新成果的总结:JGR世界应力图项目专辑简介 总被引:5,自引:0,他引:5
JGR杂志97卷B8期是世界应力图项目的专辑。该专辑总结了1986年至1990年期间国际合作研究世界板内应力场的新成果,本文对这些成果作了简要介绍。 相似文献
898.
Determining the ultimate capacity of suction caissons in response to combined vertical, horizontal, and moment loading is essential for their design as foundations for offshore wind turbines. However, the method implemented for stability analysis is quite limited. Numerical limit analysis has an advantage over traditional limit equilibrium methods and nonlinear finite element methods in this case because upper and lower bounds can be achieved to ensure that the exact ultimate capacity of the caisson falls within the appropriate range. This article presents theories related to numerical limit analysis. Simulations are conducted for centrifuge model tests, the findings of which reveal the ability of numerical limit analysis to deal with the inclined pullout capacity of suction caissons. Finally, this article proposes an estimation of the ultimate capacity of a 3.5 MW offshore wind turbine foundation on normally consolidated clay based on the typical environmental parameters of Bothkennar, Scotland. Undrained failure envelopes and safety factors are obtained for suction caissons with different embedment ratios. Failure mechanisms, plastic zones, clay stress distributions, and the influence of the skin friction coefficients of caissons are discussed in detail. 相似文献
899.
900.