全文获取类型
收费全文 | 2479篇 |
免费 | 15篇 |
专业分类
公路运输 | 701篇 |
综合类 | 90篇 |
水路运输 | 814篇 |
铁路运输 | 77篇 |
综合运输 | 812篇 |
出版年
2022年 | 24篇 |
2021年 | 20篇 |
2020年 | 23篇 |
2019年 | 20篇 |
2018年 | 59篇 |
2017年 | 64篇 |
2016年 | 104篇 |
2015年 | 34篇 |
2014年 | 67篇 |
2013年 | 391篇 |
2012年 | 130篇 |
2011年 | 134篇 |
2010年 | 110篇 |
2009年 | 118篇 |
2008年 | 112篇 |
2007年 | 86篇 |
2006年 | 55篇 |
2005年 | 56篇 |
2004年 | 41篇 |
2003年 | 42篇 |
2002年 | 38篇 |
2001年 | 43篇 |
2000年 | 44篇 |
1999年 | 36篇 |
1998年 | 57篇 |
1997年 | 41篇 |
1996年 | 42篇 |
1995年 | 55篇 |
1994年 | 23篇 |
1993年 | 32篇 |
1992年 | 27篇 |
1991年 | 24篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 22篇 |
1987年 | 23篇 |
1986年 | 23篇 |
1985年 | 19篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 16篇 |
1981年 | 18篇 |
1980年 | 24篇 |
1979年 | 26篇 |
1978年 | 16篇 |
1977年 | 16篇 |
1976年 | 12篇 |
1975年 | 22篇 |
1974年 | 16篇 |
1973年 | 10篇 |
排序方式: 共有2494条查询结果,搜索用时 15 毫秒
81.
M.J. Smith 《Transportation Research Part B: Methodological》1982,16(1):1-3
We consider the traffic equilibrium problem when the travel demand is inelastic and stationary in time. Junction interactions, which abound in urban road networks, are permitted. We prove that the set of equilibria (solutions to the assignment problem) is convex when certain monotonicity and continuity conditions are statisfied at each junction. 相似文献
82.
The paper considers traffic assignment, with traffic controls, in an increasingly dynamic way. First, a natural way of introducing the responsive policy, Po, into steady state traffic assignment is presented. Then it is shown that natural stability results follow within a dynamical version of this static equilibrium model (still with a constant demand). We are able to obtain similar stability results when queues are explicitly allowed for, provided demand is constant. Finally we allow demand to vary with time; we consider the dynamic assignment problem with signal-settings now fixed. Here we assume that vehicles are very short and that deterministic queueing theory applies, and show that the time-dependent queueing delay at the bottleneck at the end of a link is a monotone function of the time-dependent input profile to the bottleneck. We have been unable to obtain results when dynamic demand and responsive signal control are combined. 相似文献
83.
HE Tseng J. Asgari D. Hrovat P. van der Jagt A. Cherry S. Neads 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(3):199-216
In the pursuit of an objective rating on vehicle stability performance, it is always desirable to reduce disturbances and inconsistencies during experimental evaluations, especially the ones introduced by human drivers. This paper presents the development of a steering robot designed for closed-loop steering tasks during evasive manoeuvres. It describes the controller structure and discusses experimental results, in addition to simulation/vehicle model verifications and theoretical control analysis. 相似文献
84.
Fuzzy-logic applied to yaw moment control for vehicle stability 总被引:6,自引:0,他引:6
B. L. Boada M. J. L. Boada V. Dí az 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2005,43(10):753-770
In this paper, we propose a new yaw moment control based on fuzzy logic to improve vehicle handling and stability. The advantages of fuzzy methods are their simplicity and their good performance in controlling non-linear systems. The developed controller generates the suitable yaw moment which is obtained from the difference of the brake forces between the front wheels so that the vehicle follows the target values of the yaw rate and the sideslip angle. The simulation results show the effectiveness of the proposed control method when the vehicle is subjected to different cornering steering manoeuvres such as change line and J-turn under different driving conditions (dry road and snow-covered). 相似文献
85.
Travel time reliability, an essential factor in traveler route and departure time decisions, serves as an important quality of service measure for dynamic transportation systems. This article investigates a fundamental problem of quantifying travel time variability from its root sources: stochastic capacity and demand variations that follow commonly used log-normal distributions. A volume-to-capacity ratio-based travel time function and a point queue model are used to demonstrate how day-to-day travel time variability can be explained from the underlying demand and capacity variations. One important finding is that closed-form solutions can be derived to formulate travel time variations as a function of random demand/capacity distributions, but there are certain cases in which a closed-form expression does not exist and numerical approximation methods are required. This article also uses probabilistic capacity reduction information to estimate time-dependent travel time variability distributions under conditions of non-recurring traffic congestion. The proposed models provide theoretically rigorous and practically useful tools for understanding the causes of travel time unreliability and evaluating the system-wide benefit of reducing demand and capacity variability. 相似文献
86.
In the present work, different ventilated disc brake rotor configurations were analysed to enhance the heat transfer rate and obtain the uniform temperature distribution in the rotor. CFD code used in this work was validated at using experimental results obtained by conducting experiments on a test rig. The experimental analysis was performed to calculate the mass flow rate and heat dissipation through the rotor. Further, different types of rotor configurations viz. straight radial vane (SRV), tapered radial vane (TRV), alternate long and short vane (ALSV), variable diameter circular pillars (VDCP) were considered for the analysis. A rotor segment of 20° was considered for the numerical analysis due to its rotational symmetry. CFD results were in good agreement with the experiments. The maximum deviation of the numerical results were about 12 % from the experimental results. It is found from the analysis that among the different types of rotor configurations; variable diameter circular pillars (VDCP) rotor gives better rate of heat dissipation with more uniform temperature distribution in the flow passages. Hence for modern high speed vehicles VDCP rotor may be more appropriate. 相似文献
87.
探讨了压路机在压实施工中,压实质量的动态控制问题。结合课题实践,构思出了压实质量动态适时控制系统的工作框图。 相似文献
88.
B. Blanco A. Alonso L. Kari N. Gil-Negrete J. G. Giménez 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2018,56(4):529-552
The finite length nature of rail-pad supports is characterised by a Timoshenko beam element formulation over an elastic foundation, giving rise to the distributed support element. The new element is integrated into a vertical track model, which is solved in frequency and time domain. The developed formulation is obtained by solving the governing equations of a Timoshenko beam for this particular case. The interaction between sleeper and rail via the elastic connection is considered in an analytical, compact and efficient way. The modelling technique results in realistic amplitudes of the ‘pinned–pinned’ vibration mode and, additionally, it leads to a smooth evolution of the contact force temporal response and to reduced amplitudes of the rail vertical oscillation, as compared to the results from concentrated support models. Simulations are performed for both parametric and sinusoidal roughness excitation. The model of support proposed here is compared with a previous finite length model developed by other authors, coming to the conclusion that the proposed model gives accurate results at a reduced computational cost. 相似文献
89.
硬岩隧道掘进机的性能很大程度上取决于其切削刀具的磨损情况。刀具的磨损会降低掘进速度,进而导致掘进时间延长、项目成本增加。通常在隧道项目的规划阶段使用预测模型来进行磨损预测,而常规的磨损试验对磨损系统的考虑还不够准确,并没有考虑到刀具/土体的相互作用、周围介质(水、膨润土)以及掘进过程中的荷载等因素。针对该问题,专门设计了一个水平放置的磨损试验设备。本文介绍了该试验方法,研究并讨论了磨损系统相关因素对磨损率的影响。结果表明,该设备可模拟真实的掘进过程,很好地解决了上述问题,达到了高效、准确预测磨损的效果。 相似文献
90.