全文获取类型
收费全文 | 6193篇 |
免费 | 307篇 |
专业分类
公路运输 | 2730篇 |
综合类 | 1198篇 |
水路运输 | 871篇 |
铁路运输 | 1379篇 |
综合运输 | 322篇 |
出版年
2024年 | 23篇 |
2023年 | 44篇 |
2022年 | 235篇 |
2021年 | 378篇 |
2020年 | 314篇 |
2019年 | 184篇 |
2018年 | 136篇 |
2017年 | 192篇 |
2016年 | 205篇 |
2015年 | 236篇 |
2014年 | 429篇 |
2013年 | 286篇 |
2012年 | 687篇 |
2011年 | 490篇 |
2010年 | 327篇 |
2009年 | 320篇 |
2008年 | 372篇 |
2007年 | 412篇 |
2006年 | 365篇 |
2005年 | 224篇 |
2004年 | 173篇 |
2003年 | 118篇 |
2002年 | 78篇 |
2001年 | 73篇 |
2000年 | 29篇 |
1999年 | 13篇 |
1998年 | 19篇 |
1997年 | 38篇 |
1996年 | 42篇 |
1995年 | 24篇 |
1994年 | 11篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1988年 | 1篇 |
排序方式: 共有6500条查询结果,搜索用时 645 毫秒
861.
The objective of this research is to identify the factors differentiating between single heavy vehicle collisions at intersections and midblocks by using a binary logit model. Our results show that single vehicle crashes involving heavy vehicle at intersections are more likely to occur on main roads and highways, whereas crashes at midblocks are more likely to occur on divided two‐way roads, roads with special facilities or features (e.g. bridge) and roads with a higher percentage of heavy vehicle traffic. Intersection crashes are also more likely to involve vehicles that are turning left or right, resulting in angle crashes and vehicle overturn, whereas midblock crashes are more likely to involve vehicles on higher posted speed roads. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
862.
Vinicius F. Dal Poggetto 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(2):191-209
Many researches have been conducted in the area of control applied to vehicle dynamics, aiming at reducing the possibility of the occurrence of the type of accident known as rollover. In this research, based on a common nonlinear model and its linearisation, a method for properly selecting matrices for solving the Riccati equation considering different speeds was proposed. The method showed in which ways speed really influences the choice of controller gains. By developing the dynamic equations for the yaw- and roll-coupled motions and modelling of controllers and state observers, it is possible to compare the efficacy of this control strategy using both linear and nonlinear simulations using Matlab. Significant results were obtained regarding the reduction of the rollover coefficient for a double-lane change manoeuvre at different speeds, thus indicating advantages of using this controller in practical cases. 相似文献
863.
J.A. Mohrfeld-Halterman 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(1):124-136
Presented in this paper is a procedure to develop a high fidelity quasi steady-state aerodynamic model for use in race car vehicle dynamic simulations. Developed to fit quasi steady-state wind tunnel data, the aerodynamic model is regressed against three independent variables: front ground clearance, rear ride height, and yaw angle. An initial dual range model is presented and then further refined to reduce the model complexity while maintaining a high level of predictive accuracy. The model complexity reduction decreases the required amount of wind tunnel data thereby reducing wind tunnel testing time and cost. The quasi steady-state aerodynamic model for the pitch moment degree of freedom is systematically developed in this paper. This same procedure can be extended to the other five aerodynamic degrees of freedom to develop a complete six degree of freedom quasi steady-state aerodynamic model for any vehicle. 相似文献
864.
Jong-Boo Han Hyung-Suk Han Sung-Soo Kim Seok-Jo Yang 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(3):370-385
Normally, Maglev (magnetic levitation) vehicles run on elevated guideways. The elevated guideway must satisfy various load conditions of the vehicle, and has to be designed to ensure ride quality, while ensuring that the levitation stability of the vehicle is not affected by the deflection of the guideway. However, because the elevated guideways of Maglev vehicles in South Korea and other countries fabricated so far have been based on over-conservative design criteria, the size of the structures has increased. Further, from the cost perspective, they are unfavourable when compared with other light rail transits such as monorail, rubber wheel, and steel wheel automatic guided transit. Therefore, a slender guideway that does have an adverse effect on the levitation stability of the vehicle is required through optimisation of design criteria. In this study, to predict the effect of various design parameters of the guideway on the dynamic behaviour of the vehicle, simulations were carried out using a dynamics model similar to the actual vehicle and guideway, and a limiting value of deflection ratio of the slender guideway to ensure levitation control is proposed. A guideway that meets the requirement as per the proposed limit for deflection ratio was designed and fabricated, and through a driving test of the vehicle, the validity of the slender guideway was verified. From the results, it was confirmed that although some increase in airgap and cabin acceleration was observed with the proposed slender guideway when compared with the conventional guideway, there was no notable adverse effect on the levitation stability and ride quality of the vehicle. Therefore, it can be inferred that the results of this study will become the basis for establishing design criteria for slender guideways of Maglev vehicles in future. 相似文献
865.
Abdelkader Merah Kada Hartani Azeddine Draou 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(1):86-101
In recent years, the driver's active assistances have become important features in commercialised vehicles. In this paper, we present one of these features which consists of an advanced driver assistance system for lane keeping. A thorough analysis of its performance and stability with respect to variations in driver behaviour will be given. Firstly, the lateral control model based on visual preview is established and the kinematics model based on visual preview, including speed and other factors, is used to calculate the lateral error and direction error. Secondly, and according to the characteristics of the lateral control, an efficient strategy of intelligent electric vehicle lateral mode is proposed. The integration of the vehicle current lateral error and direction error is chosen as the parameter of the sliding mode switching function to design the sliding surface. The control variables are adjusted according to the fuzzy control rules to ensure that they meet the existence and reaching condition. A new fuzzy logic-based switching strategy with an efficient control law is also proposed to ensure a level of continuous and variable sharing according to the state of the driver and the vehicle positioning on the roadway. The proposed control law acts either at the centre of the lane, as a lane keeping assistance system to reduce the driver's workload for long trips, or as a lane departure avoidance system that intervenes for unintended lane departures. Simulation results are included in this paper to explain this concept. 相似文献
866.
867.
运用弹性系数法预测北京机动车保有量 总被引:1,自引:0,他引:1
综述了机动车保有量的预测方法,包括时间序列回归法、神经网络法、弹性系数法等,分析了不同方法的特点,给出了相关启示。结合北京经济发展趋势,运用弹性系数法对机动车保有量进行了预测。 相似文献
868.
869.
870.