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   1143篇
  免费   18篇
公路运输   372篇
综合类   40篇
水路运输   384篇
铁路运输   36篇
综合运输   329篇
  2023年   4篇
  2022年   27篇
  2021年   6篇
  2020年   5篇
  2019年   12篇
  2018年   39篇
  2017年   33篇
  2016年   35篇
  2015年   8篇
  2014年   52篇
  2013年   184篇
  2012年   64篇
  2011年   67篇
  2010年   62篇
  2009年   49篇
  2008年   50篇
  2007年   32篇
  2006年   26篇
  2005年   28篇
  2004年   14篇
  2003年   21篇
  2002年   19篇
  2001年   21篇
  2000年   11篇
  1999年   15篇
  1998年   22篇
  1997年   19篇
  1996年   25篇
  1995年   14篇
  1994年   8篇
  1993年   12篇
  1992年   15篇
  1991年   11篇
  1990年   12篇
  1989年   8篇
  1988年   5篇
  1986年   4篇
  1985年   8篇
  1984年   9篇
  1983年   4篇
  1982年   7篇
  1981年   13篇
  1980年   13篇
  1979年   16篇
  1978年   9篇
  1977年   8篇
  1976年   9篇
  1975年   9篇
  1974年   5篇
  1973年   6篇
排序方式: 共有1161条查询结果,搜索用时 15 毫秒
981.
C. A. Nash 《运输评论》2013,33(4):289-300
This paper presents a brief review of rail policy and the performance of the rail system in Australia, and draws some comparisons with the rail systems of Western Europe. Australian railways present a somewhat paradoxical mixture of booming traffic with severe financial problems, poor productivity and — in some cases — outdated equipment. The competitive environment they face varies from state to state both in the freedom accorded to road competition and the degree to which the railways themselves are permitted to take decisions on a commercial basis. Whilst some railways in Australia — notably Westrail — have virtually completed the transition from a government department to a commercial enterprise, others have only just begun.  相似文献   
982.
Coastal ecosystems such as mangroves, salt marshes, and seagrasses provide important ecosystem services, including nursery habitat for fish, shoreline protection, and the recently recognized service of carbon sequestration and storage. When these wetland ecosystems are degraded or destroyed, the carbon can be released to the atmosphere, where it adds to the concentration of greenhouses gases (GHGs) that contribute to climate change. Many federal statutes and policies specifically require that impacts on ecosystem services be considered in policy implementation. Yet, no federal statute, regulation, or policy accounts directly for the carbon held in coastal habitats. There are a number of federal statutes and policies for which coastal carbon ecosystem services could reasonably be added to environmental and ecosystem considerations already implemented. We look at a subset of these statutes and policies to illustrate how coastal carbon ecosystem services and values might affect the implementation and outcomes of such statutes generally. We identify key steps for the inclusion of the ecosystem services of coastal habitats into the implementation of existing federal policies without statutory changes; doing so would increase the degree to which these policies consider the full economic and ecological impacts of policy actions.  相似文献   
983.

The use of third-party logistics services by large US manufacturers continues to grow. Increasingly, those services are used to support international sourcing and sales activities. Use of these services is often triggered by specific events such as a corporate restructuring, a top management change or a benchmarking effort. Nearly two-thirds of users report they experienced significant impediments in implementing third-party agreements. After starting conservatively, the typical user buys a wide variety of logistics services. Users generally report that buying logistics services has had a positive impact on their organizations, particularly with respect to logistics costs and customer service. However, many also report negative impact on employee morale linked to downsizing the logistics workforce. More than two-thirds of users report cancelling at least one-third-party logistics contract. Nevertheless, if given complete responsibility to make the decision, >70% of users would increase their companies' use of such services.  相似文献   
984.
This paper shows how the Operational Research approach can be used in the shipping industry to obtain effective savings. The approach is by way of a recent study to determine an optimal drydock policy in which the principal criterion was to minimize the total cost of operation. Additional areas, indicating the range of studies carried out in the marine field, are also mentioned.  相似文献   
985.
Historically there have been only two groups involved in the conflict that has engulfed the US maritime industry for the past fifty years maritime labour unions and shipping companies. The configuration of these groups at different times in this struggle, has led to distinct periods of conflict in the industry. This paper analyses the basis and continuation of the problem.  相似文献   
986.
Book reviews     
R. S. Farrow, with J. M. Broadus, T. A. Grigalunas, P. Hoagland III, and J. J. Opaluch. 1990. Managing the Outer Continental Shelf Lands: Oceans of Controversy. New York: Taylor & Francis New York, 168 pp., paper.

Richard A. Kenchington. 1990. Managing Marine Environments. New York: Taylor & Francis, 248 pp.  相似文献   
987.

Most airlines across Asia are struggling to cope with an unprecedented economic crisis which they have very little control over, and the survival of some remains in doubt. The continuing uncertainty generated by the crisis has accelerated the process of change in the aviation industry and has highlighted the need for adaptability, and its effects have been deeper and longer lasting than previously anticipated. After a year-long slump in the Asian travel market, airlines are now considering a range of options and rehabilitation programmes including a series of cost-cutting measures. There appears to be a trend towards the extension and consolidation of strategic alliances, structural and operational reorganization, and the application of new technologies. The success of these measures will become apparent over time, but action is necessary to minimize the adverse consequences of the crisis which has dominated the region since 1997.  相似文献   
988.
In this work a methodology is presented for the computation of the intersection of parametric surfaces, namely Non Uniform Rational B-Splines (NURBS), with special attention to some specific requirements for applications to ship hull modeling. The algorithm adopted and the steps of the proposed method are described, namely checking whether the surfaces intersect, preprocessing of linear surfaces with strong discontinuities, computation of starting points, marching along intersection curves, and approximation of the intersections with NURBS curves. Finally, the results of some intersection tests are presented and discussed. The results are validated by comparison with results of commercial codes.  相似文献   
989.
Air pollution from mobile sources is an important environmental problem in larger cities. In 2001, a program was implemented to encourage the use of natural gas in vehicles in the Aburrá Valley in Colombia, with incentives to convert small cars from gasoline and diesel to hybrid engines with natural gas, most notably a cash subsidy. Using a survey administered to both commercial and private car owners we study the determinants of conversion under this fuel conversion program. We thus obtain information about the reasons for adoption of new technologies in vehicles. This allows us to discuss the possible outcomes of this type of policy. Results show that a large part of owners who switched would have done it anyway without the subsidy. Based on the findings, commercial vehicles are most likely to be converted to natural gas vehicles.  相似文献   
990.
An increasing number of legislative efforts have been undertaken to prohibit the use of hand-held wireless devices while driving. As of July 2012, ten states and the District of Columbia enforce laws banning the use of hand-held cell phones while driving. Thirty-nine states and the District of Columbia have banned text messaging while driving. Recent studies of driver behavior suggest that hand-held wireless device usage negatively impacts driver performance. However few studies at the aggregate level address the plausible link between the use of hand-held wireless devices while driving, increased risk of automobile accidents, and government legislative efforts to reduce such risk. This paper analyzes data at the aggregate level and builds a regression model to estimate the long term accident rate reduction due to a hand-held ban. This model differs from previous studies, which consider short term accident rate reduction, by considering time trends in the accident rate due to the ban. Additionally, counties considered in this analysis are placed into groups based on driver density, defined by the number of licensed drivers per centerline mile of roadway, and a separate analysis is performed within these groups. This approach allows one to better quantify the effect of hand-held bans in counties of different driver densities. Results from this paper suggest that bans on hand-held wireless device use while driving reduce the rate of personal injury accidents in counties with high levels of driver density, but may increase accident rates in counties with low driver density levels. These results can inform transportation policymakers interested in reducing automobile-accident-risk attributable to the use of hand-held wireless devices while driving.  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