全文获取类型
收费全文 | 184篇 |
免费 | 4篇 |
专业分类
公路运输 | 73篇 |
综合类 | 59篇 |
水路运输 | 12篇 |
铁路运输 | 34篇 |
综合运输 | 10篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 2篇 |
2021年 | 4篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 3篇 |
2014年 | 15篇 |
2013年 | 16篇 |
2012年 | 12篇 |
2011年 | 25篇 |
2010年 | 10篇 |
2009年 | 18篇 |
2008年 | 12篇 |
2007年 | 24篇 |
2006年 | 9篇 |
2005年 | 9篇 |
2004年 | 6篇 |
2003年 | 6篇 |
2002年 | 3篇 |
2001年 | 1篇 |
1989年 | 1篇 |
排序方式: 共有188条查询结果,搜索用时 15 毫秒
1.
薄壁箱梁剪滞剪切效应自振特性分析 总被引:1,自引:0,他引:1
在推导考虑剪力滞、剪切变形双重效应的单元刚度矩阵与等效结点荷载矩阵的基础上[1],进一步推导出考虑双重效应的单元质量矩阵,从而形成完整的薄壁箱梁考虑双重效应的矩阵分析体系,可方便地纳入矩阵位移法程序系统,为常见的薄壁连续梁等复杂结构的剪力滞效应分析提供一种计算手段。利用自编程序ZLBOX对薄壁箱型简支梁和悬臂梁考虑剪力滞、剪切变形双重效应时的自振特性进行了分析,所得结果与ANSYS实体单元计算结果符合良好。计算结果表明,剪力滞、剪切变形双重效应使薄壁箱梁的自振频率降低,剪力滞效应占双重效应的85%以上,双重效应对高阶频率的影响比低阶频率的影响大。 相似文献
2.
3.
体外预应力高强混凝土薄壁箱梁试验研究 总被引:1,自引:3,他引:1
进行了体外预应力高强混凝土薄壁箱梁从预应力钢绞线张拉到承载力极限破坏这一全过程的试验研究,研究了体外预应力损失及应力增量、跨中截面应力—应变分布以及跨中挠度和抗裂性能等问题。研究结果表明:体外预应力高强混凝土薄壁箱梁预应力损失实测值与现行规范计算值基本吻合,探讨了其截面受压翼缘有效分布宽度和体外预应力筋应力增量的变化规律,初步揭示了体外预应力高强混凝土薄壁箱梁在混凝土开裂前和受拉非预应力钢筋屈服后混凝土受压翼缘存在不同的剪力滞效应,并提出了相应状态下的受压翼缘有效分布宽度系数。 相似文献
4.
为了分析梁轴线为竖向曲线的多室箱梁在桥墩处的剪力滞效应,基于比拟杆理论,通过用支座反力等效代替桥墩约束,求得了顶板沿桥轴线的轴力、剪力方程,算出了各加劲肋、腹板处加劲杆的换算面积,然后根据剪切变形协调方程,建立了考虑加劲肋影响的剪力滞微分方程组。将所建方程组的计算结果与采用ANSYS APDL软件建立的板壳有限元模型计算结果进行对比后发现:采用所建方程可避免求解2阶微分方程组的困难,易于使用,且能反映局部竖弯梁段的剪力滞效应变化情况,但计算精度随着叠加并积分的剪力流增加而降低;对于靠近计算起始端截面的加劲杆而言,比拟杆法计算应力与模型计算应力差值在10%左右;竖弯梁顶板最大应力处的剪力滞系数为1.4,大于直梁在该处的剪力滞系数1.2,直梁在该处的轴向应力与竖弯梁相比减小了5.9 MPa,可以认为存在竖弯的箱型梁对剪力滞的影响是不利的。 相似文献
5.
When a new public transport service is introduced it would be valuable for public authorities, financing organisations and
transport operators to know how long it will take for people to start to use the service and what factors influence this.
This paper presents results from research analysing the time taken for residents living close to a new guided bus service
to start to use (or adopt) the service. Data was obtained from a sample of residents on whether they used the new service
and the number of weeks after the service was introduced before they first used it. Duration modelling has been used to analyse
how the likelihood of starting to use the new service changes over time (after the introduction of the service) and to examine
what factors influence this. It is found that residents who have not used the new service are increasingly unlikely to use
it as time passes. Those residents gaining greater accessibility benefits from the new service are found to be quicker to
use the service, although the size of this effect is modest compared to that of other between-resident differences. Allowance
for the possibility that there existed a proportion of the sample that would never use the new service was tested using a
split population model (SPD) model. The SPD model indicates that 36% of residents will never use the new service and is informative
in differentiating factors that influence whether Route 20 is used and when it is used.
Kiron Chatterjee has been a Senior Lecturer at the University of the West of England, Bristol, since 2003 and previously was at the University of Southampton. Currently, a main focus of his research is on longitudinal analysis of travel behaviour to improve policy analysis. Kang-Rae Ma received a PhD in Planning from University College London. He worked at the University of the West of England, Bristol, and the Korea Transport Institute before he joined Chung-Ang University as an Assistant Professor. His research interests include modelling of travel behaviour and urban excess commuting. 相似文献
Kang-Rae MaEmail: |
Kiron Chatterjee has been a Senior Lecturer at the University of the West of England, Bristol, since 2003 and previously was at the University of Southampton. Currently, a main focus of his research is on longitudinal analysis of travel behaviour to improve policy analysis. Kang-Rae Ma received a PhD in Planning from University College London. He worked at the University of the West of England, Bristol, and the Korea Transport Institute before he joined Chung-Ang University as an Assistant Professor. His research interests include modelling of travel behaviour and urban excess commuting. 相似文献
6.
7.
针对一票制公共交通IC卡刷卡系统存在的滞后时间问题,提出基于特征子序列修正的时差匹配推算方法。依托GPS车辆到站信息序列和刷卡聚类序列,分析首末站和中途站站间运行时间分布的差异化特征,分别从两序列中提取大时间差和连续小时间差等特征子序列;利用两种子序列间一对一或一对多的对应关系分别进行初步搜索和二次修正,兼顾匹配过程的效率和精度。将推算流程应用于山西省大同市公共汽车系统,结果显示,抽样车辆的刷卡匹配率均达到99%以上,并且针对不同类型的公共汽车线路具有较强的适应性。 相似文献
8.
Grégory Vandenbulcke Claire Dujardin Isabelle Thomas Bas de GeusBart Degraeuwe Romain MeeusenLuc Int Panis 《Transportation Research Part A: Policy and Practice》2011,45(2):118-137
This paper attempts to explain the spatial variation of the use of a bicycle for commuting to work at the level of the 589 municipalities in Belgium. Regression techniques were used and special attention was paid to autocorrelation, heterogeneity and multicollinearity. Spatial lag models were used to correct for the presence of spatial dependence and a disaggregated modelling strategy was adopted for the northern and southern parts of the country. The results show that much of the inter-municipality variation in bicycle use is related to environmental aspects such as the relief, traffic volumes and cycling accidents. Town size, distance travelled and demographic aspects also have some effect. In addition, there are regional differences in the effects of the structural covariates on bicycle use: the impact of variables such as traffic volume and cycling accidents differs substantially between the north and the south of the country. This paper also suggests that high rates of bicycle use in one municipality stimulate cycling in neighbouring municipalities, and hence that a mass effect can be initiated, i.e. more cycle commuting encourages even more commuters in the area to cycle. These findings provide some recommendations for decision-makers wishing to promote a shift from car to bicycle use. 相似文献
9.
10.
基于能量变分原理的薄壁箱梁自振特性分析 总被引:5,自引:0,他引:5
以能量变分原理为基础,综合考虑剪力滞后效应、剪切变形和转动惯量的影响,推导出箱形截面梁的控制微分方程和相应的自然边界条件,据此获得几种常用边界条件(简支、悬臂、连续、两端固支)的固有频率方程,提出一种能对工程中常用矩形薄壁箱梁自振特性进行分析的方法。通过算例将解析解与板壳有限元结果进行了比较,证明了该方法的有效性,所得公式比以往剪滞理论有一定发展,且为箱形梁桥动力特性的进一步研究奠定了理论基础。 相似文献