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   222篇
  免费   6篇
公路运输   26篇
综合类   58篇
水路运输   32篇
铁路运输   29篇
综合运输   83篇
  2024年   1篇
  2023年   1篇
  2021年   7篇
  2020年   6篇
  2019年   3篇
  2018年   11篇
  2017年   6篇
  2016年   9篇
  2015年   12篇
  2014年   23篇
  2013年   27篇
  2012年   15篇
  2011年   12篇
  2010年   4篇
  2009年   8篇
  2008年   19篇
  2007年   15篇
  2006年   16篇
  2005年   6篇
  2004年   9篇
  2003年   3篇
  2001年   3篇
  2000年   3篇
  1999年   2篇
  1998年   3篇
  1997年   1篇
  1993年   1篇
  1991年   1篇
  1988年   1篇
排序方式: 共有228条查询结果,搜索用时 500 毫秒
61.
The primary aim of the paper is to determine a short‐run cost function for Dublin City Bus Services (DCS), using a translog approach. The results show that there are significant economies of density in the transit operation. The results also indicate that the structure of DCS is characterised by a homothetic production function and that partial elasticities of substitution are non‐unitary.  相似文献   
62.
The introduction of minibuses into the transit fleets of some cities makes it more important than ever to investigate the economic and operating conditions of these vehicles for various transit and paratransit services. A high performance transit system is of great interest, owing to its desirable characteristics. However, it is not feasible to establish and use such a system all over a city. It is therefore necessary to support a high performance transit system with other modes to extend its area of operation (owing to higher demand) and also to connect those areas that are not covered by the high performance system to it. This paper considers the use of minibuses in the design of metro line feeders and to characterize the economic domain in which it is efficient to use them in a feeder network. Based on results from ant colony optimization, the performance measures of minibuses are compared with those of conventional buses to help make decision makers aware of the use and role of these vehicles. The study contradicts the common belief that, since minibuses require similar driver costs to those of conventional buses, it is not economical to use them in a transit fleet; in fact, it is shown that minibuses can displace conventional buses in some situations in a feeder network.  相似文献   
63.
以大型集装箱船为研究目标,通过对普通燃油集装箱船与核动力集装箱船的运行费用进行分析,并对2种船舶全寿期内的运行费用进行比较。结果表明,在全寿期内,核动力集装箱船相比普通燃油集装箱船在油价高于367美元/t时,具有较好的经济性。  相似文献   
64.
Electric vehicles (EV) are often considered a promising technology to decrease external costs of road transport. Therefore, main external cost components are estimated for EV and internal combustion engine vehicles (ICEV). These include costs of accidents, air pollution, climate change, noise, and congestion. All components are estimated over the product lifetime and, where appropriate, differentiated according to fuel type, vehicle size as well as emission location and time. The advantage of this differentiation is, however, compensated by high uncertainties of most cost estimates. Overall, the external costs of EV and ICEV do not differ significantly. Only for climate change, local air pollutants in congested inner-cities, and noise some advantageous effects can be observed for EV. The advantages depend strongly on the national electricity power plant portfolio and potentially also on the charging strategy. Controlled charging might allow for higher emission reductions than uncontrolled charging of EV.  相似文献   
65.
在收集S700K-C型电动转辙机现场转换阻力测试数据的基础上,建立了道岔转换阻力的一般统计分析模型,分析外锁闭道岔转换阻力与转辙机输出力的关系特点,提出道岔维护建议,便于提高道岔工电维护的效率,减少道岔转换故障发生概率。  相似文献   
66.
According to the economic theory, if all the first-best conditions are met, social optimality involves the prices to be set equal to social marginal costs. When it is not possible to set prices equal to social marginal costs, due to the presence of constraints within the transport sector or distortions elsewhere in the economy, the theory suggests corrections to the SMC principle (second-best alternatives). But the implementation of second best alternatives can give rise to serious problems when transferred from theory to practice. This chapter will discuss in particular the problems that might rise when investment cost are included (totally or partially) in the social marginal costs rules, and in particular when private operators are involved.  相似文献   
67.
Cost characteristics of differently sized inland waterway terminals (IWTs) have not received much scientific attention. This observation is remarkable given the importance of costs in transportation decision-making. Classification of differently sized IWTs and their cost structure will lead to more insight into the container cost per terminal. Therefore, the goal of our research was to determine both the characteristics of the cost structure associated with different inland waterway (IWW) container terminal types and the sensitivity of the system to cost/TEU changes in input and operational conditions. We show that terminals with a higher container throughput encounter fewer costs, and can therefore charge a lower price. Assumed delays of 2 h per day on the waterside cause a 4.7–6.6% cost increase per container, mainly caused by extra labor costs. It is also assumed that the changing climate will influence terminal operations and results in extreme water levels (lasting two weeks occurring four times a year) causing a cost increase of 1.0–3.4%. Subsidies can cause cost reductions of 0.3–10.4% depending on the exact form, with the smaller terminals benefiting more because their investment costs are higher relative to operational costs. A subsidy can lower costs by up to 10.4%, but it is questionable whether small and medium terminals will have a lower cost price than the market price, showing that it is important for small and medium terminals to quickly grow in size.  相似文献   
68.
探讨了诚信的涵义及其现代意义,分析了当前高职学生诚信缺失的表现及其产生的原因,提出了高职学生自律意识较差,道德心理还不成熟;诚信道德意识与行为失衡;价值取向的双重标准是导致高职学生诚信缺失的主要原因。  相似文献   
69.
地铁动力照明系统负荷对运营成本的影响   总被引:3,自引:1,他引:2  
通过深圳地铁开通运行的实测数据,反映出目前地铁设计中配电变压器容量普遍偏大的情况,并指出设计负荷计算偏大的若干原因;通过计算,阐述配电变压器偏大对运营成本的影响。  相似文献   
70.
重大件货物刚性系固中的外力计算   总被引:5,自引:0,他引:5  
沈华 《中国航海》2000,(2):28-33
利用特别设计的支架,将重大件货物固定于支架上,并将货物和支架一起固定于船的承载部位,此种系固方法通常称为刚性系固。刚性系固是海上重大件货物(尤指超长、超宽、超重大件货物)运输安全的必要保证。本文应用船舶耐波性理论和方法,建立了作用于货物单元上运动惯性力的计算公式,从而为货物支架的设计和刚性系固系统的强度校核提供了比较精确和可靠的力学依据。  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