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   767篇
  免费   51篇
公路运输   60篇
综合类   336篇
水路运输   106篇
铁路运输   128篇
综合运输   188篇
  2024年   1篇
  2023年   3篇
  2022年   14篇
  2021年   20篇
  2020年   13篇
  2019年   16篇
  2018年   29篇
  2017年   38篇
  2016年   46篇
  2015年   49篇
  2014年   49篇
  2013年   100篇
  2012年   39篇
  2011年   46篇
  2010年   44篇
  2009年   51篇
  2008年   66篇
  2007年   43篇
  2006年   48篇
  2005年   30篇
  2004年   19篇
  2003年   10篇
  2002年   7篇
  2001年   8篇
  2000年   5篇
  1999年   5篇
  1997年   4篇
  1996年   4篇
  1994年   2篇
  1993年   4篇
  1992年   1篇
  1991年   1篇
  1989年   3篇
排序方式: 共有818条查询结果,搜索用时 31 毫秒
51.
刘冬云 《港口科技》2010,(11):30-32
阐述了我国企业年金税收政策。分析了目前企业年金税收政策存在问题。指出了现行政策对我国年金发展存在的影响,以期促进我国企业年金的发展。  相似文献   
52.
Wind power resources on the eastern U.S. continental shelf are estimated to be over 400 GW, several times the electricity used by U.S. eastern coastal states. The first U.S. developer proposes to build 130 large (40 story tall) wind turbines in Nantucket Sound, just outside Massachusetts state waters. These would provide 420 MW at market prices, enough electricity for most of Cape Cod. The project is opposed by a vigorous and well-financed coalition. Polling shows local public opinion on the project almost equally divided. This article draws on semistructured interviews with residents of Cape Cod to analyze values, beliefs, and logic of supporters and opponents. For example, one value found to lead to opposition is that the ocean is a special place that should be kept natural and free of human intrusion. One line of argument found to lead to support is: The war in Iraq is problematic, this war is “really” over petroleum, Cape Cod generates electricity from oil, therefore, the wind project would improve U.S. security. Based on analysis of the values and reasoning behind our interview data, we identify four issues that are relevant but not currently part of the debate.  相似文献   
53.
Downs (1962) and Thomson (1977) suggested that highway capacity expansion may produce counterproductive effects on the two-mode (auto and transit) transport system (Downs–Thomson Paradox). This paper investigates the occurrence of this paradox when transit authority can have different economic objectives (profit-maximizing or breakeven) and operating schemes (frequency, fare, or both frequency and fare). For various combinations of economic objectives and operating schemes, the interaction between highway expansion and transit service is explored, as well as its impact on travelers’ mode choices and travel utilities. Further, for each combination, the conditions for occurrence of the Downs–Thomson Paradox are established. We show that the paradox never occurs when transit authority is profit-maximizing, but it is inevitable when the transit authority is running to maximize travelers’ utility while maintaining breakeven. This is because the former transit authority tends to enhance transit service (e.g., raise frequency or reduce fare) when facing an expanded highway; and on the contrary, the latter tends to compromise transit service (e.g., reduce frequency or raise fare). Both analytical and numerical examples are provided to verify the theoretical results.  相似文献   
54.
Meligrana  John F. 《Transportation》1999,26(4):359-398
This paper discusses the evolving institutional structure and governance of transportation planning, policy development and transit delivery within one major North American city-region, the Greater Vancouver area. Various methods of transportation governance are explored from complete independence to full regional integration. The move away from a direct provincial role in transportation management to a greater regional transit authority is discussed and critiqued. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
55.
总结和回顾了上海轨道交通票价体制的发展历程,分析了现行的票价体制及其存在的问题,指出了上海轨道交通票价体制改革的必要性和依据.在此基础上,综合考虑乘客、企业和政府三者利益,提出上海票价体制改革的原则和策略,为上海轨道交通票价体制改革提供参考.  相似文献   
56.
Disruptions and random supplies have been important sources of uncertainty that should be considered in the design and control of supply chains. There have been many real world examples in which a single catastrophic event has simultaneously degraded the capabilities of several suppliers leading to considerable erosion of profits and goodwill for a company. However, the literature on analytical models that account for the dependence nature of disruptions and its impact on supply chain performance is sparse.In this paper, we consider an m-manufacturer, 1-retailer, newsvendor inventory system with stochastically dependent manufacturing capacities, caused by random disruptions that may simultaneously inflict damages to the capacities of the manufacturers. We develop the structural/analytical properties of key performance measures and optimal inventory policies for the multi-source and assembly inventory systems. We show that stochastic dependence in disruptions can have opposite effects on system performance in the multi-source and assembly systems. While risk diversification is preferred in the multi-source system, risk concentration is preferred in the assembly system. Our results also suggest that, if the retailer ignores the effect of dependent disruptions, then in the multi-source structure, it would underestimate the cost, overestimate the fill rate, and order more units than the optimum; however, in the assembly structure, the opposite would happen. We perform a comprehensive numerical study to validate our analytical results and generate useful managerial and operational insights for effective risk management of supply chains in the presence of dependent supply uncertainty.  相似文献   
57.
This paper reviews trends in cycling levels, safety, and policies in Canada and the USA over the past two decades. We analyze aggregate data for the two countries as well as city-specific case study data for nine large cities (Chicago, Minneapolis, Montréal, New York, Portland, San Francisco, Toronto, Vancouver, and Washington). Cycling levels have increased in both the USA and Canada, while cyclist fatalities have fallen. There is much spatial variation and socioeconomic inequality in cycling rates. The bike share of work commuters is more than twice as high in Canada as in the USA, and is higher in the western parts of both countries. Cycling is concentrated in central cities, especially near universities and in gentrified neighborhoods near the city center. Almost all the growth in cycling in the USA has been among men between 25-64 years old, while cycling rates have remained steady among women and fallen sharply for children. Cycling rates have risen much faster in the nine case study cities than in their countries as a whole, at least doubling in all the cities since 1990. They have implemented a wide range of infrastructure and programs to promote cycling and increase cycling safety: expanded and improved bike lanes and paths, traffic calming, parking, bike-transit integration, bike sharing, training programs, and promotional events. We describe the specific accomplishments of the nine case study cities, focusing on each city’s innovations and lessons for other cities trying to increase cycling. Portland’s comprehensive package of cycling policies has succeeded in raising cycling levels 6-fold and provides an example that other North American cities can follow.  相似文献   
58.
交通需求管理是大城市交通政策的重要组成部分,提出了基于实施难易影响因素的交通需求管理措施分类,总结了深圳从20世纪90年代中期开始相继实施的一系列相对较易实施的交通需求管理措施情况,分析展望需进一步考虑的交通需求管理措施。针对交通拥挤收费这一较难及重大的需求管理措施,回顾了深圳探索性研究拥挤收费方案,包括交通拥挤收费总体调控目标、收费区域范围、收费模式与时段、收费系统技术选型等,分析了实施面临的困难,并提出了实施突破与替代的建议。  相似文献   
59.
Road traffic accident fatalities lead to important private and social costs in the metropolitan areas of most low and middle income countries. An important share of these fatalities is due to injuries to the head and the neck. Helmets can provide efficient protection, but many drivers do not use them. We focus on helmet use behavior among motorbike users in Delhi. We use a detailed data set collected for the purpose of the study. To guide our empirical analysis, we rely on a model in which drivers decide on self-protection and self-insurance. The empirical findings suggest that risk-averse drivers are more likely to wear a helmet and that this has no systematic effect on speed. Helmet use also increases with education. Drivers who show a higher awareness of road risks seem to be both more likely to wear a helmet and to speed less. Controlling for risk awareness, we observe that drivers tend to compensate between speed and helmet use. The results can provide a basis for awareness-raising policies. They also show that improvements to the road infrastructure risk leading to risk-compensating behavior.  相似文献   
60.
Despite considerable interest in the role of social interactions and social context on transportation, there have been very few attempts to explore specific cases of social interaction influencing transportation systems. This paper explores the social practice of slugging, an informal system of carpooling in the Washington, DC area. Slugging emerged in response to the establishment of Virginia’s High Occupancy Vehicle (HOV) lanes in the early 1970s, as single drivers picked up riders alongside the road (slugs) in order to meet the requirements for driving in the less congested HOV lanes. Drawing on the work of sociologist Anthony Giddens, as well as the sociological insights of Georg Simmel and Stanley Milgram, we suggest that the practice of slugging highlights the processes of institutionalization and structuration. This paper details how the region’s mass transportation policies and urban culture have combined to result in an institutionalized practice with particular norms and logics of behavior. We conclude that looking at specific cases where social context has affected transportation, like slugging, could provide useful insights on the impact of social context on transportation policies and systems.  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