首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   396篇
  免费   26篇
公路运输   208篇
综合类   62篇
水路运输   17篇
铁路运输   111篇
综合运输   24篇
  2024年   2篇
  2023年   4篇
  2022年   16篇
  2021年   23篇
  2020年   25篇
  2019年   17篇
  2018年   8篇
  2017年   11篇
  2016年   9篇
  2015年   17篇
  2014年   19篇
  2013年   14篇
  2012年   74篇
  2011年   33篇
  2010年   23篇
  2009年   15篇
  2008年   11篇
  2007年   36篇
  2006年   26篇
  2005年   12篇
  2004年   7篇
  2003年   6篇
  2002年   1篇
  2001年   2篇
  2000年   4篇
  1998年   1篇
  1995年   2篇
  1993年   2篇
  1991年   2篇
排序方式: 共有422条查询结果,搜索用时 15 毫秒
101.
为了定量地研究大型枢纽机场的地面交通组织系统,首先阐明了单独研究机场可达性的意义,提出了使用通达成本来描述机场可达性的新的方法,从而用化为货币形式的成本来衡量可达性。主要从快捷性,经济性和舒适性三方面来计算成本。为了量化抽象的舒适性,提出了通过“旅行者的疲劳恢复时间”来间接转化的方法。最后按照人群,地区的划分计算总通达成本加权平均。在数据的处理上,提出了使用Logit模型对两个重要参数进行标定和校正。最后,给出了几个简化算例,重点对上海浦东国际机场进行了可达性评价,然后简要地将其与其他两个国际机场进行了横向比较。结果表明:舒适性是一项不可忽略的可达性衡量指标。我国机场的可达性较国外有待提高。  相似文献   
102.
简支梁桥上拱度对高速行车舒适性影响研究   总被引:1,自引:0,他引:1  
中小跨径的PC简支梁桥过度上拱现象经常出现对行车舒适性产生了不利的影响.基于1/4汽车模型,采用常量力移动荷载模型模拟桥梁振动,以及半正弦曲线模拟桥梁上拱后所形成的桥面纵坡曲线,分别建立了由桥梁振动和桥梁上拱引起的车辆振动响应方程,分析比较了以上2种情况对车辆振动的影响.得出桥梁振动相对于上拱度对车辆振动的影响很小的结论.  相似文献   
103.
In order to improve the level of bus service, a field study was undertaken to develop a combined bus comfort model. This paper provides a comprehensive review of the different ways to predict the bus comfort, in addition to the variable experimental techniques used. It was found some environment parameters like noise, vibration, thermal comfort and the acceleration would affect the passengers’ experience. In this model, both the measurement of objective physical parameters and subjective questionnaire survey were conducted to gather the practical environment date, as well as to distribute questionnaires on board city buses during the same trips. By comparing the subjective views of bus passengers to objective physical parameters, a combined bus comfort model was established. This model helps to calculate the concrete value of passengers’ perceived bus comfort. An effective approach integrated the comfort model, measuring instrument and the driver monitor could greatly improve the bus service quality.  相似文献   
104.
This paper discusses the use of inerters to improve the stability and performance of a full-train system. First, we construct a 28 degree-of-freedom train model in AutoSim, and obtain a linearised model for analysis in Matlab. Then, the benefits of inerters are investigated by the critical speed, settling time and passenger comfort. In addition, we apply a new mechatronic network for further performance improvement, and synthesise the optimal electrical circuit for experimental verification. From the results, inerters are shown to be effective in improving the stability and performance of train systems.  相似文献   
105.
Active suspensions for railway vehicles have been a topic of research for a number of decades and while their applications in service operation are limited, it seems clear that they will in due course see widespread adoption. Railway suspension design is a problem of compromise on the non-trivial trade-off of ride quality versus track following (guidance), and the skyhook damping control approach has been paramount in illustrating the potential benefits. Since skyhook damping control, various advanced control studies appeared contributing to redefine the boundaries of the aforementioned trade-off. Yet there is no study on the impact of fractional order (FO) methods in the context of skyhook railway active suspensions and in particular related to skyhook damping control. This is the area to which this paper strongly contributes. We present findings from a current project on FO controllers for railway vehicles active suspensions, in particular work on the effect of FO methods in basic skyhook damping control schemes, i.e. pure and intuitively based skyhook. First, we present a brief review of conventional skyhook damping control and then proceed to a rigorous investigation of the impact of FO on the ride quality/track following trade-off. The relevant benefits from FO methods are appraised and new insights highlighted.  相似文献   
106.
Vibration accelerations were measured on a compact wheel loader during 11 operations with two drivers and with/without the activated boom suspension system (BSS). Two standards, ISO 2631-1 (1985) and ISO 2631-1 (1997), were used to assess the effect of wheel loader vibration on comfort. The assessment results of ISO 2631-1 (1985) showed that vibration in the frequency range from 4 to 20 Hz in the vertical direction and in the frequency range from 1.6 to 3.15 Hz in the vertical and driving directions plays an important role in comfort assessment. The overall total values of vibration measured on the wheel loader in all operations exceeded the ‘uncomfortable’ boundary specified in ISO 2631-1 (1997). The speed had a larger influence on the vibration intensity than the bucket load, the BSS or the driver biodynamic response during driving. During driving and V-cycle, the difference of vibration intensity with two drivers in the z-direction is larger than that in the x- and y-direction.  相似文献   
107.
以某大客车为研究对象,分别拟合前后悬架空气弹簧刚度,在Matlab中建立八自由度整车模型,并进行平顺性仿真与实验,将其仿真结果与试验结果进行比较,结果显示,所建立的动力学模型及仿真结果是正确的。  相似文献   
108.
旅客列车空调硬座车厢内热舒适性研究   总被引:1,自引:1,他引:0  
空调车内气流组织研究是车厢内环境控制的基础,合理的气流组织可有效地改善乘客的热舒适性。采用k-ε湍流模型,对载客车厢内三维空气流场和温度场进行了数值计算,在此基础上利用PMV(Predicted Mean Vote)指标分析了车厢内人体热舒适性。计算结果表明:在现有的条缝送风条件下,除车厢中部和两端外,车厢内气流分布比较均匀;由于回风口位于车厢两端,车厢中部和端部PMV分布不同,端部人体热舒适感较好,中部较差;座位区由于人员集中和受太阳照射的影响,温度较高,PMV值偏大;过道区温度适中,人体热舒适感较好。研究结果对空调车内气流组织优化设计和改善人体热舒适环境有一定参考价值。  相似文献   
109.
SW-220K型转向架参数优化试验研究   总被引:1,自引:0,他引:1  
对配装SW—220K型转向架的25T型客车进行了振动试验;分析了车辆的主要振型;分别进行了采用不同空气弹簧、二系阻尼系数值时的试验,根据垂向、横向平稳性指标测试结果,得出了采用原型空气弹簧结构并增大二系垂向阻尼系数值能够改善车辆运行性能的结论。  相似文献   
110.
Carbody tilting is today a mature and inexpensive technology that permits higher train speeds in horizontal curves, thus shortening travel time. However, tilting trains run a greater risk of causing motion sickness than non-tilting ones. It is likely that the difference in motions between the two train types contributes to the observed difference in risk of motion sickness. Decreasing the risk of motion sickness has until now been equal to increasing the discomfort related to quasi-static lateral acceleration. But, there is a difference in time perception between discomfort caused by quasi-static quantities and motion sickness, which opens up for new solutions. One proposed strategy is to let the local track conditions influence the tilt and give each curve its own optimised tilt angle. This is made possible by new tilt algorithms, storing track data and using a positioning system to select the appropriate data. The present paper reports from on-track tests involving more than 100 test subjects onboard a tilting train. A technical approach is taken evaluating the effectiveness of the new tilt algorithms and the different requirements on quasi-static lateral acceleration and lateral jerk in relative terms. The evaluation verifies that the rms values important for motion sickness can be influenced without changing the requirements on quasi-static lateral acceleration and lateral jerk. The evaluation shows that reduced quantities of motions assumed to have a relation to motion sickness also lead to a reduction in experienced motion sickness. However, a limitation of applicability is found as the lowest risk of motion sickness was not recorded for the test case with motions closest to those of a non-tilting train. An optimal level of tilt, different from no tilt at all, is obtained. This non-linear relation has been observed by other researchers in laboratory tests.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号