全文获取类型
收费全文 | 628篇 |
免费 | 3篇 |
专业分类
公路运输 | 228篇 |
综合类 | 21篇 |
水路运输 | 206篇 |
铁路运输 | 23篇 |
综合运输 | 153篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 4篇 |
2020年 | 5篇 |
2019年 | 9篇 |
2018年 | 18篇 |
2017年 | 12篇 |
2016年 | 23篇 |
2015年 | 9篇 |
2014年 | 27篇 |
2013年 | 89篇 |
2012年 | 29篇 |
2011年 | 34篇 |
2010年 | 36篇 |
2009年 | 31篇 |
2008年 | 26篇 |
2007年 | 13篇 |
2006年 | 12篇 |
2005年 | 10篇 |
2004年 | 10篇 |
2003年 | 7篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 11篇 |
1999年 | 4篇 |
1998年 | 13篇 |
1997年 | 7篇 |
1996年 | 15篇 |
1995年 | 8篇 |
1993年 | 4篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 10篇 |
1987年 | 5篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 11篇 |
1980年 | 3篇 |
1979年 | 14篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 8篇 |
排序方式: 共有631条查询结果,搜索用时 15 毫秒
511.
The brake and steering systems in vehicles are the most effective actuators that directly affect the vehicle dynamics. In general, the brake system affects the longitudinal dynamics and the steering system affects the lateral dynamics; however, their effects are coupled when the vehicle is braking on a non-homogenous surface, such as a split-mu road. The yaw moment compensation of the steering control on a split-mu road is one of the basic functions of integrated or coordinated chassis control systems and has been demonstrated by several chassis suppliers. However, the disturbance yaw moment is generally compensated for using the yaw rate feedback or using wheel brake pressure measurement. Access to the wheel brake pressure through physical sensors is not cost effective; therefore, we modeled the hydraulic brake system to avoid using physical sensors and to estimate the brake pressure. The steering angle controller was designed to mitigate the non-symmetric braking force effect and to stabilize the yaw rate dynamics of the vehicle. An H-infinity design synthesis was used to take the system model and the estimation errors into account, and the designed controller was evaluated using vehicle tests. 相似文献
512.
J. -H. Choi S. -H. Choi D. Park C. -H. Park B. -O. Rhee D. -H. Choi 《International Journal of Automotive Technology》2012,13(2):273-277
The quality of an injection molded part is largely affected by the mold cooling. Consequently, this makes it necessary to
optimize the mold cooling circuit when designing the part but prior to designing the mold. Various approaches of optimizing
the mold cooling circuit have been proposed previously. In this work, optimization of the mold cooling circuit was automated
by a commercial process integration and design optimization tool called Process Integration, Automation and Optimization (PIAnO),
which is often used for large automotive parts such as bumpers and instrument panels. The cooling channels and baffle tubes
were located on the offset profile equidistant from the part surface. The locations of the cooling channels and the baffle
tubes were automatically generated and input into the mold cooling computer-aided engineering program, Autodesk Moldflow Insight
2010. The objective function was the deviation of the mold surface temperature from a given design temperature. Design variables
in the optimization were the depths, distances and diameters of the cooling channels and the baffle tubes. For a more practical
analysis, the pressure drop and temperature drop were considered the limited values. Optimization was performed using the
progressive quadratic response surface method. The optimization resulted in a more uniform temperature distribution when compared
to the initial design, and utilizing the proposed optimization method, a satisfactory solution could be made at a lower cost. 相似文献
513.
The objective of this paper is to ease the planning of new toll projects by providing estimates of operating costs, and to
help us make better informed decisions about the design of toll collection systems. To do so we use panel data for Norwegian
toll companies to estimate average cost functions. The main results can be summarised as follows. We provide evidence of very
important unexploited economies of scale. The estimated cost curves are very steep for traffic levels below the sample mean,
and become almost entirely flat over a wide range above the sample mean. A higher share of vehicles using on board units will
significantly reduce average costs. Competitive tendering will significantly reduce average operating costs by as much as
25%. Our results also suggest that increased number of lanes, higher debt and passenger charging will increase average operating
costs whereas average operating costs are lower for toll cordons compared with other projects.
相似文献
Morten WeldeEmail: |
514.
Batley Richard Bates John Bliemer Michiel Börjesson Maria Bourdon Jeremy Cabral Manuel Ojeda Chintakayala Phani Kumar Choudhury Charisma Daly Andrew Dekker Thijs Drivyla Efie Fowkes Tony Hess Stephane Heywood Chris Johnson Daniel Laird James Mackie Peter Parkin John Sanders Stefan Sheldon Rob Wardman Mark Worsley Tom 《Transportation》2019,46(3):583-621
Transportation - This paper provides an overview of the study ‘Provision of market research for value of time savings and reliability’ undertaken by the Arup/ITS Leeds/Accent consortium... 相似文献
515.
W.M. Zhai C.B. Cai S.Z. Guo 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1996,26(1):61-79
A new dynamic model of vehicle/track interaction is presented. The model considers the vehicle and the track as a whole system and couples the vertical interaction with the lateral interaction. The vehicle subsystem is modeled as a multi-body system with 37 degrees of freedom, which runs on the track with a constant velocity. The track substructure is modeled as a discretely supported system of elastic beams representing the rails, sleepers and ballasts. The normal contact forces between wheels and rails are described by Hertzian nonlinear elastic contact theory and the tangential wheel/ rail forces are decided by the creep theory. Numerical results are compared with those of conventional dynamic models of railway vehicles. Applications of the coupling model to the investigation of safety limits against derailment due to the track twist and the combined alignment and cross-level irregularities are reported at the end of the paper. 相似文献
516.
主动底盘系统的发展趋向(上) 总被引:4,自引:1,他引:4
本文论述“主动底盘系统”范畴内两个最现实的问题:悬架咸振及四轮转向。关于悬架减振,首先探讨传统悬架的规律,然持阐述主动和半主动悬架系统对悬架可能作出的改进。对所滑“悬空阻尼”系统,着重怍了介绍。四轮转向方面首先论述了比例四轮转向、质心侧偏角补偿和可调节的四轮转向等几种基本型式的理论基础。接着介绍了现有的四轮转向系统。 相似文献
517.
主动底盘系统的发展趋向(下) 总被引:2,自引:0,他引:2
本文论述“主动底盘系统”范畴内两个最现实的问题:悬架减振及四轮转向。关于悬架减振,首先探讨传统悬架的规律,然后阐述主动和半主动悬架系统对悬架可能作出的改进。对所谓“悬空阻尼”系统,着重作了介绍。四轮转向方面首先论述了比例四轮转向、质心侧偏角补偿和可调节的四轮转向等几种基本型式的理论基础。接着介绍了现有的四轮转向系统。 相似文献
518.
刘光溪:入世谈判过程本身具有重大意义 入世谈判的过程对于中国经济的发展、中国经济体制改革的深化是一个巨大的教育过程.这次谈判不光是经济和贸易的交锋,还是两种文化、两种理念的碰撞,对中华民族价值取向、理性思维将产生深远的影响. 相似文献
519.
偏压隧道衬砌结构可靠度分析 总被引:2,自引:1,他引:2
提出了基于有限单元法求解偏压隧道衬砌结构可靠度的方法,开发了实用计算机程序,并给出实际算例。 相似文献
520.
Victoria Williams Robert B. Noland Ralf Toumi 《Transportation Research Part D: Transport and Environment》2002,7(6)
Two of the ways in which air travel affects climate are the emission of carbon dioxide and the creation of high-altitude contrails. One possible impact reduction strategy is to significantly reduce the formation of contrails. This could be achieved by limiting the cruise altitude of aircraft. If implemented, this could severely constrain air space capacity, especially in parts of Europe. In addition, carbon emissions would likely be higher due to less efficient aircraft operation at lower cruise altitudes. This paper describes an analysis of these trade-offs using an air space simulation model as applied to European airspace. The model simulates the flight paths and altitudes of each aircraft and is here used to calculate emissions of carbon dioxide and changes in the journey time. For a one-day Western European traffic sample, calculations suggest annual mean CO2 emissions would increase by only 4% if cruise altitudes were restricted to prevent contrail formation. The change in journey time depended on aircraft type and route, but average changes were less than 1 min. Our analysis demonstrates that altitude restrictions on commercial aircraft could be an effective means of reducing climate change impacts, though it will be necessary to mitigate the increased controller workload conflicts that this will generate. 相似文献