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   957篇
  免费   20篇
公路运输   234篇
综合类   46篇
水路运输   284篇
铁路运输   23篇
综合运输   390篇
  2023年   4篇
  2022年   9篇
  2021年   14篇
  2020年   9篇
  2019年   10篇
  2018年   32篇
  2017年   23篇
  2016年   45篇
  2015年   6篇
  2014年   35篇
  2013年   175篇
  2012年   41篇
  2011年   47篇
  2010年   55篇
  2009年   55篇
  2008年   45篇
  2007年   35篇
  2006年   25篇
  2005年   26篇
  2004年   13篇
  2003年   20篇
  2002年   9篇
  2001年   13篇
  2000年   16篇
  1999年   5篇
  1998年   12篇
  1997年   12篇
  1996年   12篇
  1995年   21篇
  1994年   8篇
  1993年   8篇
  1992年   7篇
  1991年   5篇
  1990年   10篇
  1989年   11篇
  1988年   4篇
  1987年   7篇
  1986年   4篇
  1985年   13篇
  1984年   6篇
  1983年   8篇
  1982年   8篇
  1981年   7篇
  1980年   8篇
  1979年   6篇
  1978年   4篇
  1977年   8篇
  1975年   8篇
  1974年   4篇
  1972年   4篇
排序方式: 共有977条查询结果,搜索用时 140 毫秒
861.
A key attribute of competitive tendering for the periodic selection of operators of subsidised public transport services is to secure the provision of specified services at efficient cost levels. This has proved particularly effective where services were previously provided by an inefficient monopoly operator. The arguments for the adoption of competitive tendering in preference to negotiation with the incumbent operator may be less clear-cut in other cases.Consideration is given to both theoretical and practical insights into the relative merits of competitive tendering and negotiation approaches in such situations. The limited literature on the topic is reviewed and insights and lessons identified. Influencing issues include prior conditions, the nature of the supplier market, features of contracts, negotiating and competitive tendering strategies and practice, accountability and transparency, and long-term market implications. The evidence suggests that ‘one size does not fit all’, and the choice will depend on specific circumstances.The relative merits of the two approaches for renewal of bus contracts are considered with regard to Adelaide, for contracts which have previously been awarded through competitive tendering. The paper draws out the main factors that could influence the authority’s choice between the options, and discusses the relevance of the findings to other situations.  相似文献   
862.
IntroductionThefiwtee1emenmethod(FEM)playsanextrmelyimPortantroleintheanalysesofengineeringproblems.ForalongtimethismethodhasmainlybeenaPPliedinthelinearfieldandshownitsgreatpower.HoweveealOtofnonlinearengineeringPrOblemsWhichcanneitherbesimPlyreducedtolinearonesnorrCPresentedbylinearlyanalogywhichshallchnsethePfacticalconditionsrelativelymuch,havechallengedfiniteelementmethod(FEM).RecentymuchProgresshasbeenmadebothinthemathematicalandmechanicaltheoryandthecomPulertechnologysothatevent…  相似文献   
863.
Computer simulations of a driven vehicle are performed to assess and quantify the automobile stability. The analytical methodology is based on PoincarS maps and Floquet theory, which are commonly used to investigate the stability of periodic systems. The approach accommodates the study of the complex dynamics of vehicle locomotion under various configurations of the system. The proposed method does not require any knowledge regarding the inner structure of the vehicle model. Kinematic data is simply collected at the specific instants to conduct the analysis. It is found that this method has the potential for real time warning and control of vehicle instabilities.  相似文献   
864.
By means of a mathematical model the effects of lateral front fork flexibility on the vibrational modes of single-track vehicles have been studied. The analysis performed by Sharp has been used as a starting point. The results have been compared with Roe's empirical findings. The results of the analysis have been translated into practical advice for a more optimal front fork construction.  相似文献   
865.
This paper looks at how the Shippers' Council could operate to make shipping cost-effective and to play its role as a servant of trade a servant of the shippers. It looks at the key problems that confront the shipper requiring intervention by a Shippers' Council and surveys how the organization of the Shippers' Council effectively handles problems. The final sections draw conclusions which could contribute to increasing the efficiency of Shippers' Councils, as well as improving the understanding of the Councils as managers of the demand side of shipping.  相似文献   
866.
This paper sets out the developments in world shipbuilding policy that have occurred in the past decade. It reviews and outlines the situation that existed in the late 1990s, when an Organization for Economic Co-operation and Development (OECD) agreement on the elimination of shipyard operating subsidies was tantalisingly close. After the Introduction, the second section provides a brief review of the development of the industry over the past three decades, setting the context for developments since 1997. The third section discusses the complaint of the European Union (EU) to the World Trade Organization (WTO) concerning the Republic of Korea's support for its shipbuilding sector, and its counterclaim over the EU's temporary defence mechanism (TDM). It is argued that the core of the EU's case at the WTO was flawed, and that the reintroduction of an operating subsidy via the TDM was a mistake. The only prospect for regularizing competition in this area lies in the negotiation of the OECD agreement that was completed, but not ratified, in 1994. Given the souring of relations between two of the main players in this area, the prospects for such a settlement seem remote. The fourth section uses Olson's theory of groups to argue that the European Commission's actions were driven primarily by industry pressure groups, and failed to consider the potential views of other European stakeholders, in particular the taxpayers. Given the failure of the EU's action at the WTO, the future direction of European shipbuilding policy will have to focus on strategies for internal development and improved industrial competitiveness.  相似文献   
867.
铁路运输拥有系统上的优势,尤其是能源和生态优势,但是,为了能获得社会的更好评价和吸引更多客运量和货运量,重要的就是要在机车车辆制造时保证不断采用新技术方案,以便提高旅客舒适度,降低噪声和振动,保证整个铁路系统电磁兼容性和功能的可靠性.  相似文献   
868.
This paper extends the existing literature on optimal cargo-handling rates by considering: (i) under what circumstances the optimal rate will actually be provided, and (ii) how the optimal rate is affected if there are pre-booked time slots at the berth, containerized cargoes, or deterrent effects of long queues.  相似文献   
869.
There are several important structural design parameters in the analysis of a mat type structure for a jackup mobile offshore drilling unit. These consist of dimensions for the mat, soil foundation types, and structural loads. Methods for determining the proper dimension of the mat structure, modeling the structure and its loading cases, modeling the soil conditions and a method for identifying critical load cases for each element and load case is presented. By using a database approach for the finite element output for all of the various loading cases, a rational approach is presented which solves the problem of sorting and analyzing all of the elements and load cases, ensuring that all are included and none of the critical cases are missed.  相似文献   
870.
This paper discusses the use in logistics management of the freight network equilibrium model, developed in Harker and Friesz (1985a, b), called the Generalized Spatial Price Equilibrium Model, or GSPEM. After this discussion, computational techniques for solving this model are presented. The application of GSPEM to the analysis of the U.S. coal economy is then presented and future extensions of this line of research are discussed.  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