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   2484篇
  免费   13篇
公路运输   702篇
综合类   86篇
水路运输   820篇
铁路运输   77篇
综合运输   812篇
  2022年   24篇
  2021年   20篇
  2020年   23篇
  2019年   19篇
  2018年   59篇
  2017年   67篇
  2016年   103篇
  2015年   34篇
  2014年   66篇
  2013年   394篇
  2012年   128篇
  2011年   135篇
  2010年   112篇
  2009年   117篇
  2008年   112篇
  2007年   86篇
  2006年   55篇
  2005年   56篇
  2004年   42篇
  2003年   42篇
  2002年   38篇
  2001年   43篇
  2000年   44篇
  1999年   36篇
  1998年   57篇
  1997年   41篇
  1996年   42篇
  1995年   55篇
  1994年   22篇
  1993年   32篇
  1992年   27篇
  1991年   24篇
  1990年   17篇
  1989年   17篇
  1988年   22篇
  1987年   23篇
  1986年   23篇
  1985年   19篇
  1984年   19篇
  1983年   15篇
  1982年   16篇
  1981年   18篇
  1980年   24篇
  1979年   26篇
  1978年   16篇
  1977年   16篇
  1976年   12篇
  1975年   22篇
  1974年   16篇
  1973年   10篇
排序方式: 共有2497条查询结果,搜索用时 31 毫秒
481.
This article presents the results of a three-year effort at applying information technology to the problem of collaborative natural resource management in San Diego Bay. As such, it represents an approach to integrated coastal zone management (ICZM). This effort resulted from a collaboration between the San Diego Supercomputer Center at the University of California, San Diego and the San Diego Bay Interagency Water Quality Panel for the purpose of (1) developing an environmental data repository to facilitate the acquisition and sharing of data and (2) the development of a visual model of the bay in support of the development of a comprehensive, coordinated management plan for San Diego Bay. It was determined from this study that information technology is an important and key component to ICZM but that sociopolitical factors may override the benefits of decision-support systems and should be considered at the outset of any project of this kind.  相似文献   
482.
Findings are reported of the VALCOAST project that had as one of its research objectives to ascertain: (a) stakeholder willingness to participate and cooperate in coastal management (CM), given local and national CM practices; and (b) stakeholder assessment of the "accessibility" and "friendliness" of current CM processes. The project involved case studies and stakeholder interviews in Belgium, Greece, Spain, and the UK. Major findings include: (1) most stakeholders are willing to cooperate in three out of the four case areas, but not to the same extent; (2) the participating "officials" in the case studies are expecting the stakeholders to be less willing to cooperate than the latter indicate; (3) stakeholders in all case studies do not expect to be heard by those responsible for CM, find it difficult to learn about the relevant institutional arrangements, and consider the communication of the objectives and anticipated impacts of CM policies to be inadequate. It is concluded that the strong evidence of stakeholders' potential willingness to cooperate in local initiatives is very encouraging for a devolved, regional approach to European Union coastal management policies, provided that this potential is capitalized upon in such policy processes.  相似文献   
483.
This paper presents findings of a freight transport study carried out for Mumbai city (India). Based on the case study of lunch box delivery system organized by the Mumbai dabbawalas, demonstrated that an informal sector was capable of developing an urban logistics system that was precise, reliable and affordable to the middle class society in Mumbai. These facts suggest an approach based on adapting logistics solutions harmoniously to the urban landscape, public policy, infrastructure and skill sets of the company’s employees in order to be attractive to the end customer, offering a good match between supply and demand i.e., consumer and producer satisfaction. At the same time logistics solutions should evolve continuously in order to be attractive to the core customer base and should be customer driven. These basic management principles can be applied in the management of other urban logistics companies in the world over.  相似文献   
484.
Recent transport sector liberalisation, as well as global economic crisis, is favouring the implementation of transport infrastructure projects through Public–Private Partnerships (PPP). However, there is a debate as to whether PPP schemes are a better option than conventional procurement. To this end, an evaluation framework is proposed, to assess which of these two alternative schemes for transport projects financing is preferable for the public. The proposed framework is complimentary to the Value for Money (VfM) approach and is based on a Multi Criteria Analysis (MCA). The first step is the estimation of the Public Sector Comparator (PSC) for the case of conventional procurement, dealing with construction, maintenance and operation costs revenues, as well as any costs associated with risks undertaken by the public. As for the PPP case, it includes any payments by the public sector and related risks costs. The MCA is then applied only if the PPP is found preferable for the public sector. The latter considers additional impacts, including among others the social attributes of a particular scheme, job creation, environmental impacts and safety and security aspects. The proposed framework was applied to a pilot Bus Rapid Transit (BRT) corridor infrastructure project in the city of Indore, India, in order to demonstrate its validity. The framework and its application could provide useful guidance when considering PPP for a transport project, since it demonstrates in a transparent way the society's attitude towards this project, something that is critical to its acceptance.  相似文献   
485.
Lack of a clear understanding regarding the economic impacts of non-motorized modes is a major reason why they are excluded from the transportation development agenda of cities in India. Keeping this aspect in mind the present study has been divided in to two parts. The first part tries to understand the non-motorized traffic evolution in India. It focuses on the declination of non-motorized modes, necessity to revamp it, the favorable conditions to promote them in India and the relative problems associated with it. It is found here that there is a necessity for defining the role of non-motorized modes in India for the viable implementation of infrastructure and policies related with it.  相似文献   
486.
Predominance of containerised mode of transport for export of general cargo has influenced the mode choices on the inland segment. Prior to containerisation the general cargo for export moved to ports invariably on road in break bulk form. Growth of containerisation led to development of inland terminals enabling an exporter to obtain export clearance at the inland points. This process facilitated an exporter to move cargo either in break bulk or in containerised form, and as inland terminals facilitated aggregation an exporter could move cargo either by road or rail. Thus containerisation increased the inland transport options for an exporter from one to three. The paper develops discrete choice models in the Indian context for inland movement of containerised export cargo. Primary data was collected from 124 export firms through a structured questionnaire. This data is supplemented with data from transport firms and terminal operators. Using the above data, a nested logit model with rail container and road truck in one branch was found to predict the mode choice behaviour best. Amongst the transport attributes, total cost and total transit time were found to be influencing the mode choices significantly. The study however did not find the effect of reliability and loss and damage significant. In addition, the model also predicts that non transport attributes - like the percentage of letters of credit that materialise with inland way bills and the value of export benefits that materialise after export - are important in the mode choice decision.  相似文献   
487.
This paper compares recent experiences in contract negotiation and subsequent commitment in public air services with the bus industry. The heart of the paper is a survey of European and Australian regional airlines, which we mirror with revealed experiences of bus operators. We aim to identify a number of elements in the contracting regimes that have exposed ambiguity and significant gaps in what the principal (e.g., transport department) expected, and what the agent (airline or bus operator) believed they were obliged to deliver. Ultimately airline and bus services are similar in that public authorities procure transport services that are desirable for the society but would be unprofitable without government involvement. In both sectors (theoretically fairly similar) public transport contracts are used, and those usually include obligations and performance measurements. In terms of similarities, one of the surveyed contract details that had a perceived high clarity in both industries was “payment procedures” and amongst those with rather poor clarity was also in both industries “incentives to improve performance and grow patronage”. We also show differences between regional air services and bus operations with regard to performance measurement and pre-specified obligations. Because of the strong safety culture around air services we find that regulation and trusting partnerships are even more important to aviation than to the bus sector. Because of the high level of trust but also because of simpler and more complete contracts in aviation, there is much less (re-)negotiation going on compared to the bus operations.  相似文献   
488.
The burgeoning commitment to contracting the delivery of bus services through competitive tendering or negotiated performance-based contracts has been accompanied by as many contract payments schemes as there are contracts. We are now well placed to design a simplified performance-linked payment (SPLP) model that can be used as a reference point to ensure value for money, given the accumulation of experiences throughout the world which have revealed substantive common elements in contracts. Whether the payment to the operator is framed as a payment per passenger or as a payment per service kilometre, the SPLP identifies efficient subsidy outcomes that are linked to a proxy indicator of net social benefit per dollar of subsidy. We illustrate how the SPLP model can be applied to obtain the gross (subsidy) cost per passenger (or per passenger km) from measures of gross cost efficiency and network effectiveness. This model can then be used as part of a benchmarking activity to identify reference value of money prospects in respect of passengers per $ subsidy outlay by adjusting for influences not under the control of the service provider. A single framework to identify contract payments to operators, and to assess (i.e., benchmark) operator performance on critical KPIs, is provided by internalising critical key performance indicators (KPIs) in the design of the SPLP. The proposed SPLP model is sufficiently general to be independent of the procurement method (competitive tendered or negotiated, for example) and of the treatment of revenue allocation (net or gross based contracts), with the additional advantage of being able to assess value for money for government.  相似文献   
489.
A quadratic eigenvalue problem (QEP) was posed in order to study the dynamics of flexible cylinders in cross-flow, simulating slender offshore structures such as risers, catenaries or tendons. The Euler–Bernoulli equation was used to model the structure assuming a fluid loading model, and yielding a quadratic eigenvalue problem that included a form of damping dependent not only on the structural damping itself, but also on the free stream velocity and the fluid force coefficients. We solved the QEP using the finite element method. We also derived a simplified analytical solution in this work for comparison with the QEP, however this solution does not consider changes in tension along the length of the cylinder as the QEP does. In our study, the QEP solutions were first validated against the simplified analytical solution, and also against a well-known experimental dataset obtained in 2003, in which a flexible circular cylinder model was used to model the dynamics of a riser undergoing multi-mode vortex-induced vibrations.  相似文献   
490.
A speed sea trial was performed in the Amundsen Sea in February and March of 2012. The Korean ice breaking research vessel “Araon” was used to check speed performance on the big floes. Two of ice trial cases were carried out. We describe the time history of location, the engine power, and the revolutions per minute during the ice trial, and the trajectory of the ship. Additionally, the measured ice properties are considered and discussed. The ice trial results were analyzed according to variation in ice thicknesses, ice strength, propulsion power, and the speed level of the ship. Our analysis results are compared to model test results and ice trial results. A correction to the target ice thickness was used to compare the power and speed relation in the same ice thickness because it is easy to know the relative speed performance of the ship. The Hamburgische Schiffbau-Versuchs Anstalt method was applied for the correction. The speed of Araon in big floes was higher than the speed in level ice. The speed after the correction at 10 MW of power and 103 cm of ice thickness was 5.4 knots based on analysis results.  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