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   300篇
  免费   4篇
公路运输   63篇
综合类   4篇
水路运输   110篇
铁路运输   6篇
综合运输   121篇
  2022年   1篇
  2019年   5篇
  2018年   3篇
  2017年   12篇
  2016年   7篇
  2015年   6篇
  2014年   3篇
  2013年   58篇
  2012年   4篇
  2011年   6篇
  2010年   19篇
  2009年   21篇
  2008年   22篇
  2007年   23篇
  2006年   12篇
  2005年   6篇
  2004年   6篇
  2003年   4篇
  2002年   5篇
  2001年   2篇
  2000年   4篇
  1999年   3篇
  1998年   3篇
  1997年   3篇
  1996年   7篇
  1995年   6篇
  1994年   1篇
  1993年   6篇
  1992年   4篇
  1991年   4篇
  1990年   2篇
  1988年   2篇
  1987年   1篇
  1986年   3篇
  1985年   1篇
  1983年   1篇
  1982年   2篇
  1981年   4篇
  1979年   4篇
  1978年   2篇
  1977年   2篇
  1976年   7篇
  1975年   4篇
  1974年   1篇
  1973年   1篇
  1972年   1篇
排序方式: 共有304条查询结果,搜索用时 15 毫秒
231.
Abstract

Most international airlines hedge fuel costs, but the theoretical justification behind this action is weak. The paper explores the nature and extent of airline fuel hedging and asks why airlines hedge. The availability of hedging instruments is first discussed, with the most liquid markets in crude and exchange traded contracts. Aviation fuel contracts are possible, but with counter‐party risk. Most major passenger airlines with sufficient cash and credit now hedge at least part of their future needs. Hedging does protect profits against a sudden upturn in crude prices caused by political and consumer uncertainty leading to slower economic growth. However, if higher oil prices are induced by strong economic growth and oil supply constraints, hedging increases volatility with hedging gains reinforcing improved profits from higher traffic and improved yields. If hedging does not reduce volatility, it may still have an accounting role in moving profits from one time period to another, insure against bankruptcy, and signal the competence of management to investors and other stakeholders.  相似文献   
232.
This paper presents a taxonomy and analysis of the content of published research in port economics, policy and management (port studies). The recent increase of these publications suggests a growing interest in the study of ports. However, the research characteristics and directions of this research field are unidentified. This paper provides a systematic analysis of port studies published during the period 1997–2008. A comprehensive cross-citation and analysis of the themes, approaches and findings of all 395 relevant journal papers identifies the extent to which the research field is maturing, and the leading papers. This paper also presents an extensive analysis of the content, based on the classification of all port studies into seven research themes. For each theme, research topics, widely used research questions, concepts and research methods and the most important research findings are discussed. Finally, we identify emerging research challenges and research questions that still need to be answered.  相似文献   
233.
Abstract

The ongoing process of port reform has led to an increasing number of publicly owned but corporatised port authorities (PAs). The performance effects of corporatisation have been analysed, for example, for the airports industry, often showing positive effects. This paper reviews the literature on port reform and the relationship between port governance structures and performance. It also presents a first case study on the effects of corporatisation of PAs, namely for the Port of Rotterdam Authority, a publicly owned but corporatised port development company. In 2004, this organisation was transformed from a municipal department to an independently operating company. The performance indicators to evaluate the effect of this corporatisation include market share, turnover, operating costs, profits, and investments. These indicators are evaluated for two periods, one prior to the corporatisation (1997–2003) and the other afterwards (2005–11). The comparison of these two periods shows that corporatisation has led to significant improvements of all performance indicators. The findings derived from this case study are relevant for the ongoing discussion on port governance models.  相似文献   
234.
Abstract

This paper analyses the feasibility of incorporating electric or hybrid vehicles in intermodal transport for the transportation of containers in the pre- and post haulage (PPH) operation. In Europe, the intermodal transport market is being strongly supported, as it is seen as one of the keystones of a sustainable mobility system policy. The introduction of environmentally friendly electric/hybrid vehicles for the pre- and post haulage operation would mean a further enhancement leading to a more complete ecological intermodal transport chain. PPH operations are usually no longer than 30 km, and, hence, could possibly be handled by electric or hybrid vehicles.

Hybrid electric vehicles (HEV) combine electric and other drive systems, such as internal combustion engines, gas turbines and fuel cells. Hybrid electric vehicles merge the zero pollution and high efficiency benefits of electric traction with the high fuel energy density benefits of an energy source or thermal engine. The use of electrically driven vehicles for goods distribution has already been successfully proven in international demonstration projects, such as ELCIDIS. Transport of intermodal units (such as ISO containers), however, requires electric/hybrid heavy-duty goods vehicles, which are not readily available on the market, but for which the technology exists.

Different possibilities are assessed as to their technical, financial, organizational and environmental feasibility and suitability. This analysis is based on a typical mission for pre-and post haulage operations, such as type of trips, distance, frequency, urban/suburban, etc.  相似文献   
235.
Currently existing models of parking choice behaviour typically focus on the choice of types of parking spaces. Implicitly these models assume that motorists have a free choice in that spaces are available. The adaptive behaviour which they reveal when faced with congested parking spaces is not explicitly modelled. The aim of this paper is to contribute to the growing literature on parking choice modelling by developing and testing a stated choice model of adaptive behaviour of motorists who are faced with fully occupied parking lots. The findings of the analyses indicate that the model performs satisfactory as indicated by its goodness-of-fit and the fact that all significant parameters were in anticipated directions.  相似文献   
236.
从广域运输管理、进路控制、列车控制和通信系统4个方面,介绍了欧洲铁路通信信号系统的技术现状和发展。  相似文献   
237.
Abolition of the National Dock labour Scheme in July 1989 has intensified competition in Britian's ports and allowed the major port authorities and other port operators to restructure their operations and develop new investment plans. But the result has been to add to excess capacity in the industry and to porduce a 'zero-sum' process of traffic redistribution between Britain's driven largely by customer demands for lower charges.  相似文献   
238.
239.
This paper highlights some of the difficulties involved in the implementation of complex cost structures in the tree-building section of a transport demand model. The conventional tree-building algorithm is briefly described and is seen to be inadequate for the present purpose. A new algorithm is then presented which is able to implement complex cost structures properly. An example is given of the application of this algorithm to the building of tree in a public transport network. The performance of a computer program incorporating the new alrogrithm is evaluated against alternative methods of implementing complex cost structures. Some mention is then made of the vast range of potential uses for the new algorithm in the field of transport modelling and simulation.  相似文献   
240.
For efficient analysis it is important to choose the proper model that fits the problem that needs to be solved. This paper discusses three pragmatic simulation models for longitudinal behaviour of a passenger car tyre (Steady State, Transient and Rigid Ring) that may be used in e.g. an ABS simulation. The characteristics of the simulation models are evaluated using some simple simulations. Simulations with a quarter vehicle model that includes load transfer effects are carried out to determine the deviation in results between the mentioned tyre models for an ABS application. The results show that the Steady State model may only be used below 10 Hz and that the Transient model is valid up to about 30 Hz. The results from the ABS simulation with the Rigid Ring model are most reliable and are clearly different from the Steady State and Transient model, which indicates that ABS simulations should be carried out with the Rigid Ring model. Additionally it is demonstrated that for tyre behaviour on uneven roads the influence of the tyre belt cannot be neglected.  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