全文获取类型
收费全文 | 1069篇 |
免费 | 18篇 |
专业分类
公路运输 | 363篇 |
综合类 | 40篇 |
水路运输 | 347篇 |
铁路运输 | 33篇 |
综合运输 | 304篇 |
出版年
2023年 | 4篇 |
2022年 | 27篇 |
2021年 | 6篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 38篇 |
2017年 | 33篇 |
2016年 | 33篇 |
2015年 | 7篇 |
2014年 | 51篇 |
2013年 | 167篇 |
2012年 | 62篇 |
2011年 | 65篇 |
2010年 | 59篇 |
2009年 | 49篇 |
2008年 | 50篇 |
2007年 | 31篇 |
2006年 | 26篇 |
2005年 | 27篇 |
2004年 | 11篇 |
2003年 | 21篇 |
2002年 | 19篇 |
2001年 | 19篇 |
2000年 | 10篇 |
1999年 | 14篇 |
1998年 | 20篇 |
1997年 | 19篇 |
1996年 | 24篇 |
1995年 | 13篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 11篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 7篇 |
1982年 | 6篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 9篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1973年 | 5篇 |
1972年 | 3篇 |
排序方式: 共有1087条查询结果,搜索用时 15 毫秒
941.
This paper used a specialist software package to produce a detailed model of the River Mersey estuary, which can be subjected to a range of simulated tidal conditions. The aim of this research was to use the validated model to identify the optimal location for the positioning of a tidal turbine. Progress was made identifying a new optimal site for power generation using velocity data produced from simulations conducted using the MIKE 3 software. This process resulted in the identification of site 8, which sits mid-river between the Morpeth Dock and the Albert Dock, being identified as the favoured location for tidal power generation in the River Mersey. Further analysis of the site found that a 17.2-m diameter single rota multidirectional turbine with a 428-kW-rated capacity could produce 1.12 GWh annually. 相似文献
942.
Studies on campus parking indicate more severe problems and a wider range of characteristics than commercial parking because of limited parking places, special conditions, specific policies and enclosed space on university campuses. Heterogeneous characteristics are usually ignored in analyses of campus parking behavior. In this paper, a mixed logit model is applied to analyze parking choice behavior on a campus using data collected from a stated-preference survey of Tongji University, Shanghai, China. The heterogeneity of individuals with various sociodemographic characteristics is evaluated by interaction terms and random parameters. Comparison between the proposed approach and the conditional logit model shows that the results of the mixed logit model are more interpretable because they are not limited by the independence from irrelevant alternatives assumption. Key factors that have considerable effects on campus parking choices are identified and analyzed. Important regularities are also concluded from elasticity analyses. Finally, the campus is divided into two areas according to the walking distance to a new parking lot, and the modeling results show that area-specific policies should be established because the two areas have quite distinct parking choice features. 相似文献
943.
Based on an analysis of monitoring data of surface settlement in the construction of a shield running tunnel of Beijing metro, an improved hyperbolic model was proposed to fit the ground subsidence law, and the characteris⁃ tic factor M S was used to evaluate the stratum under the condition of shield construction. The relationship between stratum parameters and surface settlement was studied, with the results indicate that the surface settlement caused by shield construction complies with hyperbolic distribution and it is basically stable at 30 days, the larger the value of M S is, the better the conditions of the stratum is and the smaller the settlement is; a certain correlation exists be⁃ tween the parameters of improved hyperbolic model and the characteristic value M S . © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
944.
Wang L.He J.Fan C. 《现代隧道技术》2018,(3):200-204
This paper presents the technology measures, equipment selection and required grout properties and re-lated techniques for the grouting base-station arrangement of the drag reduction system of the Fuchun River pipe jacking project, which is characterized by a combined stratum, a longitudinal curve with a large falling head, a large gradient and high water pressure. Drag reduction by grouting can effectively reduce the friction coefficient in pipe jacking construction, decrease the time and frequency of the relay station, improve construction efficiency, and re-duce the grout loss along the stratum fissure while guaranteeing grouting pressure of the terminal, is favorable for sta-ble annular bentonite grouting between the stratum fissure and the segment. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
945.
沥青混合料的粘弹性流动导致沥青路面产生永久变形(车辙)。对于粘弹性体系,永久变形与材料的弹性参数无关,但可通过采用粘性参数的线弹性模型预估出来。为了确定沥青混合料在较大环境变化条件下的粘性,该文引入了一个新的基于常规试验数据的简单理论方法,并将根据此方法得到的车辙预估深度与法国新近的一个足尺试验数据进行对比,结果表明此线性车辙模型的适用性较好。 相似文献
946.
There are many ways of describing a solid,porous or fluid region of the computational domain when solving the Navier-Stokes equations(NSE)for flow motions.Amongst these the porous cell method is one of the most flexible approaches.In this method,a parameter is defined as a ratio of the volume open to water and air in a calculation cell to its cell volume.In the calculation,the same numerical procedure is applied to every cell and no explicit boundary conditions are needed at solid boundaries.The method is used to simulate flow through porous media,around solid bodies and over a moving seabed.The results compare well with experimental data and other numerical results.In our future work the porous cell method will be applied to more complex fluid-solid interaction situations. 相似文献
947.
Thromboembolicdiseasesareamajorcauseofmorbidityandmortality.Thepathogenicmechanismsofthediseasesre-mainunclear.Fourfactors,in... 相似文献
948.
Dan B. Marghitu David G. Beale S.C. Sinha 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1997,28(1):41-55
Computer simulations of a driven vehicle are performed to assess and quantify the automobile stability. The analytical methodology is based on PoincarS maps and Floquet theory, which are commonly used to investigate the stability of periodic systems. The approach accommodates the study of the complex dynamics of vehicle locomotion under various configurations of the system. The proposed method does not require any knowledge regarding the inner structure of the vehicle model. Kinematic data is simply collected at the specific instants to conduct the analysis. It is found that this method has the potential for real time warning and control of vehicle instabilities. 相似文献
949.
STUDYOFEFFECTOFSURFACE┐OPTICALPHONONONBIPOLARONINQUANTUM┐WELLWIREC.MLe(李泽民)GuShiwei*(顾世洧)C.CLam(林长净)(Dept.ofPhysicsandMateria... 相似文献
950.