全文获取类型
收费全文 | 6809篇 |
免费 | 471篇 |
专业分类
公路运输 | 2380篇 |
综合类 | 1940篇 |
水路运输 | 1406篇 |
铁路运输 | 1231篇 |
综合运输 | 323篇 |
出版年
2024年 | 37篇 |
2023年 | 53篇 |
2022年 | 214篇 |
2021年 | 292篇 |
2020年 | 311篇 |
2019年 | 186篇 |
2018年 | 164篇 |
2017年 | 144篇 |
2016年 | 155篇 |
2015年 | 245篇 |
2014年 | 608篇 |
2013年 | 434篇 |
2012年 | 620篇 |
2011年 | 656篇 |
2010年 | 487篇 |
2009年 | 422篇 |
2008年 | 424篇 |
2007年 | 513篇 |
2006年 | 480篇 |
2005年 | 223篇 |
2004年 | 173篇 |
2003年 | 113篇 |
2002年 | 67篇 |
2001年 | 57篇 |
2000年 | 45篇 |
1999年 | 19篇 |
1998年 | 22篇 |
1997年 | 19篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 12篇 |
1993年 | 11篇 |
1992年 | 13篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有7280条查询结果,搜索用时 15 毫秒
961.
为了确保异地征收和银行代征系统的正常运转,有效防范各类计算机网络运行的安全隐患,针对影响计算机网络安全性的因素,经过认真分析研究,提出了确保计算机网络安全运行的策略。 相似文献
962.
963.
The speed control effect of highway tunnel sidewall markings based on color and temporal frequency
下载免费PDF全文
![点击此处可从《先进运输杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The low‐luminance monotonous environment in the middle section of highway tunnels offers few reference points and is prone to cause severe visual illusion. Thus, drivers tend to underestimate their driving speed, which can induce speeding behaviors that result in rear‐end collisions. Therefore, discovering low‐cost methods of traffic engineering that reduce this visual illusion and ensure a steady driving speed is an important challenge for current highway tunnel operations. This study analyzes the effects of sidewall markings in typical highway tunnels, specifically observing how their colors and temporal frequencies affect the driver's speed perception in a low‐luminance condition. A three‐dimensional model of the middle section of highway tunnels was built in a driving simulator. Psychophysical tests of speed perception were carried out by the method of limits. The precision of the simulation model was then checked by comparing the results to field test data. The simulation tests studied the stimulus of subjectively equal speed and reaction time in relation to sidewall markings in different colors (red–white combined, yellow–white combined, and blue–white combined). Furthermore, based on the optimal color, the effects of sidewall marking with different temporal frequencies (0.4, 0.8, 1.2, 2, 4, 8, 12, 16, and 32 Hz) on the speed perception of drivers were also analyzed. The test results reveal that the color and temporal frequency of sidewall marking have a significant impact on the driver's stimulus of subjectively equal speed and reaction time. The subjects have the highest speed overestimation and an easy speed judgment with the red–white combined sidewall marking. Within the temporal frequency range of 4.45–7.01 Hz, the subjects have a certain degree of speed overestimation (less than 20%), and the speed perception is sensitive to the temporal frequency changes. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
964.
Development of a driving cycle for Colombo,Sri Lanka: an economical approach for developing countries
下载免费PDF全文
![点击此处可从《先进运输杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Financial constraints and lack of availability of traffic‐related information significantly hinder the development of driving cycles in developing countries. This paper proposes an economical, practical, accurate methodology for the development of driving cycles, including the development of a driving cycle for Colombo, Sri Lanka. The proposed methodology captures regional traffic and road conditions and selects a model that represents the collected data sample with minimum available traffic‐related information. Existing methods were modified for route selection by dividing routes into links using nodes or physical junctions to minimize the number of trips required for data collection. Speed–time data for respective links were used to reconstruct speed–time profiles of identified origin–destination pairs. The on‐board method was used for data collection, and the Markov chain theory was used to develop a transition probability matrix of state changes. An additional matrix was introduced to the existing method to improve model representativeness to the collected data sample. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
965.
966.
967.
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
968.
Seyed Milad Mousavi-Bideleh Viktor Berbyuk 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(1):58-85
To improve safety and maximum admissible speed on different operational scenarios, multiobjective optimisation of bogie suspension components of a one-car railway vehicle model is considered. The vehicle model has 50 degrees of freedom and is developed in multibody dynamics software SIMPACK. Track shift force, running stability, and risk of derailment are selected as safety objective functions. The improved maximum admissible speeds of the vehicle on curves are determined based on the track plane accelerations up to 1.5?m/s2. To attenuate the number of design parameters for optimisation and improve the computational efficiency, a global sensitivity analysis is accomplished using the multiplicative dimensional reduction method (M-DRM). A multistep optimisation routine based on genetic algorithm (GA) and MATLAB/SIMPACK co-simulation is executed at three levels. The bogie conventional secondary and primary suspension components are chosen as the design parameters in the first two steps, respectively. In the last step semi-active suspension is in focus. The input electrical current to magnetorheological yaw dampers is optimised to guarantee an appropriate safety level. Semi-active controllers are also applied and the respective effects on bogie dynamics are explored. The safety Pareto optimised results are compared with those associated with in-service values. The global sensitivity analysis and multistep approach significantly reduced the number of design parameters and improved the computational efficiency of the optimisation. Furthermore, using the optimised values of design parameters give the possibility to run the vehicle up to 13% faster on curves while a satisfactory safety level is guaranteed. The results obtained can be used in Pareto optimisation and active bogie suspension design problems. 相似文献
969.
针对一款高速汽油机主轴承内部润滑与摩擦磨损问题,考虑到轴承承载不均导致的轴瓦与润滑油非稳态传热,基于弹性流体动力润滑(EHD)和轴承动力学理论方法,通过迭代计算,得出该高速汽油机具有代表性的第三主轴承在最大转速(9500 r/min)时轴承内部精确的温度场与热变形,并以此为轴承新的几何轮廓边界条件分析轴承的实际润滑情况.结果表明,与未考虑轴瓦温度场及热变形相比,轴承润滑状态明显恶化,具体表现为轴承最小油膜厚度减小、最大油膜压力增大,且出现较严重的磨损.最后通过发动机台架试验测得轴承的实际工作情况,并与计算结果进行对比,计算结果与实际摩擦磨损情况吻合,验证了所用方法和所得研究结论的正确性. 相似文献
970.