全文获取类型
收费全文 | 1487篇 |
免费 | 213篇 |
专业分类
公路运输 | 775篇 |
综合类 | 387篇 |
水路运输 | 107篇 |
铁路运输 | 309篇 |
综合运输 | 122篇 |
出版年
2024年 | 5篇 |
2023年 | 4篇 |
2022年 | 26篇 |
2021年 | 37篇 |
2020年 | 64篇 |
2019年 | 49篇 |
2018年 | 87篇 |
2017年 | 50篇 |
2016年 | 36篇 |
2015年 | 54篇 |
2014年 | 159篇 |
2013年 | 120篇 |
2012年 | 163篇 |
2011年 | 194篇 |
2010年 | 126篇 |
2009年 | 72篇 |
2008年 | 99篇 |
2007年 | 107篇 |
2006年 | 81篇 |
2005年 | 48篇 |
2004年 | 32篇 |
2003年 | 30篇 |
2002年 | 16篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 6篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 3篇 |
1992年 | 2篇 |
1991年 | 6篇 |
1990年 | 2篇 |
1988年 | 2篇 |
排序方式: 共有1700条查询结果,搜索用时 15 毫秒
991.
Wang Z.Zhuang X. 《现代隧道技术》2018,(5):33-44
In the whole process of survey, construction and operation of rock tunnels, hydraulic fracturing is a mechanical mechanism that needs to be focused. In this paper, numerical simulation for fracture damage constitutive model and analytical formula were used to study the hydraulic fracturing of stratified sedimentary rocks. Based on multi-field coupling finite element analysis software, and combining the linear elastic fracture criterion with the damage constitutive model, a seepage-stress-rock damage coupling model is redeveloped, in which micro cracks can be characterized, and applied to study the hydraulic fracturing of rock mass in the saturated seepage process. By introducing dispersed parallel micro cracks for simulating the beddings of sedimentary rocks, the sedimentary rock cylinder model was established to simulate the hydraulic fracturing behaviors under injecting water into apertures and acting of confining pressure, in order to study the fracturing failure modes and seepage distribution patterns. In addition, the quantitative relationship between the critical water pressure for initial cracking and the confining pressure, the pore diameter of specimens was discussed by changing the pore diameter and confining pressure. In order to verify the cracking initiation pressure law obtained by numerical simulation, based on the seepage theory and the basic equation of elastic mechanics, and combined with the tensile failure mode obtained in the simulation, the formula of critical water pressure for cracking initiation in the rock cylinder with uniform linear elastic seepage was derived. The results of analytical solution and numerical calculation show that the cracking initiation pressure obtained by the two methods is in good agreement with the deviation within 3%. The larger the confining pressure, the larger the cracking initiation pressure, with the approximate linear relationship. The smaller the aperture, the larger the cracking initiation pressure, with the approximate negative slope linear relationship in a certain range. At the same time, the cracking initiation pressure by the analytical solution is always slightly greater than that of the numerical solution, which reflects the impact caused by the difference of the basic material hypothesis between the analytical method and the numerical method. When the material property parameters are consistent, the cracking initiation pressure based on the assumption of ideal linear elastomer will be greater than that of the material introduced into the initial damage bedding. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
992.
Falling-off of rock piece at tunnel arch and invert heave are the main potential safety problems affecting normal operation of the railway tunnel. The reasons causing falling-off of rock piece include squeezing by lining trol⁃ ley at construction joint, concrete cutting by cantilever end of water stop at construction joint, construction cold joint at arch, concrete quality deficiency and so on. To eliminate the falling-off of rock piece at tunnel arch caused by rig⁃ id overlap, modification of lining trolley and the flexible overlap technique combining tray with rubber gasket were adopted during the construction of Nuwashan tunnel on China-Laos railway, and the potential quality problem due to rigid overlap at construction joint of tunnel lining were effectively solved. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
993.
In a perspective of modern tunnelling philosophy, some problems on conventional tunnelling in soft rock mass were discussed. The development process of rock mechanical behavior and deformation caused by excava⁃ tion is attributed to the change course from yielding to discrete. Some effective control means were presented as well and the effect of advanced support system was evaluated. As to the deformation controlling technology for squeezing ground, the theory and design principle of yielding support system were introduced. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
994.
995.
软弱围岩公路隧道开挖工程中经常遇到事故,因此研究隧道施工开挖围岩受力及变形特性对工程建设具有积极的指导意义。本文通过MIDAS有限元分析软件,构建了软弱围岩-隧道-岩土体相互耦合作用下的力学模型,研究分析了隧道开挖过程中围岩应力场分布、锚杆轴力、二次衬砌内力、拱顶下沉及隧道净空收敛规律。对进一步研究隧道开挖施工围岩受力特性研究提供了借鉴意义。 相似文献
996.
研究目的:黄土因其结构性工程性质特殊,其中砂质黄土受冻融作用的影响尤为敏感,浅埋砂质黄土隧道施工过程中在冻融循环作用下发生各类病害屡见不鲜.本文以银西高铁惠安堡黄土隧道洞口段现场监测结果为基础,进行冻融条件下砂质黄土的参数试验,配合数值模拟等方法,得到这种不良地质条件下隧道围岩变形规律及稳定性发展状况.
研究结论:(1... 相似文献
997.
短距离硬岩及上软下硬地层盾构法施工技术 总被引:2,自引:1,他引:1
结合广州地铁3号线工程实例,介绍了城市地铁中硬岩和上软下硬地层的盾构法施工技术,对盾构在不同地层的掘进参数和注意事项进行了讨论.只要工程实施前期做好详细的地质勘查工作,摸清工程地质条件,通过有计划地更换刀具,在施工中选择合理的掘进参数,在硬岩和上软下硬地层采用盾构法施工是完全可行的. 相似文献
998.
水平岩层客运专线隧道施工技术 总被引:3,自引:0,他引:3
杨宗华 《国防交通工程与技术》2007,5(1):85-88
客运专线隧道与一般传统隧道相比,断面面积大,施工工艺和施工质量要求高,小坡山隧道是石太客运专线重点控制工程之一,该隧道围岩水平岩层特点明显,若控制不当,开挖后超欠挖现象不可避免,从开挖方法、控制爆破以及支护手段等方面,对其水平岩层Ⅲ级围岩区段施工技术进行了探讨,实际施工情况证明,所提方法可靠、技术可行。 相似文献
999.
1000.
汤屯高速公路A匝道高边坡为变质砂岩组成的顺层边坡,施工开挖到第2级中部时边坡后缘出现一弧形裂缝,变形破坏模式表现为滑移-弯曲变形。鉴于该工程的重要性,根据设计、科研单位的意见,在监测结果指导下,对边坡采用框架预应力锚索进行应急治理,边坡变形基本稳定后再施工抗滑桩。从方案实施效果上看,由于该应急措施的采取使得其后的抗滑桩施工较为顺利,应急处理方案是有效的。监测结果表明,治理措施效果较好,目前边坡已处于稳定状态。 相似文献