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331.
Car use per person has historically grown year-on-year in Great Britain since the 1950s, with minor exceptions during fuel crises and times of economic recession. The ‘Peak Car’ hypothesis proposes that this historical trend no longer applies. The British National Travel Survey provides evidence of such an aggregate levelling off in car mileage per person since the mid-1990s, but further analysis shows that this is the result of counter trends netting out: in particular, a reduction in per capita male driving mileage being offset by a corresponding increase in female car driving mileage. A major contributory factor to the decline in male car use has been a sharp reduction in average company car mileage per person. This paper investigates this aspect in more detail. Use of company cars fell sharply in Britain from the 1990s up to the 2008 recession. Over the same period, taxation policy towards company cars became more onerous, with increasing levels of taxation on the benefit-in-kind value of the ownership of a company car and on the provision of free fuel for private use. The paper sets out the changes in taxation policy affecting company cars in the UK, and looks at the associated reductions in company car ownership (including free fuel) and patterns of use. It goes on to look in more detail at which groups of the population have kept company cars and in which parts of the country they have been most used, and how these patterns have changed over time. A preliminary investigation is also made of possible substitution effects between company car and personal car driving and between company car use and rail travel. Clearly, the role of the company car is only one of many factors that are contributing to aggregate changes in levels of car use in Great Britain, alongside demographic changes and a wide range of policy initiatives. But, company car use cannot fall below zero, so the effect of declining year-on-year company car mileage suppressing overall car traffic levels cannot continue indefinitely. 相似文献
332.
A study of oil and gas development in the Gulf of Mexico provided a unique opportunity to compare data from sediment profile images (SPI) with that of sediment cores collected at locations in the central Gulf of Mexico from 1034 to 1175 m. Variables measured from SPI included sediment grain-size, sediment texture, apparent depth of oxygen penetration (aDOP) into the sediments, and parameters related to biogenic activity (tubes, burrows, feeding pits or mounds, and subsurface feeding voids). Variables measured from the sediment cores included sedimentation rate, dissolved oxygen profiles, and redox potential (Eh). There was a high degree of concordance between the two data sets based on correlation analysis. For example, the correlation between aDOP and maximum penetration of oxygen into the sediment was 0.69. For deep-sea sediment, SPI provides a means by which general geochemical conditions of near surface sediment can be remotely assessed providing a quick method for mapping surficial geochemistry over large areas. 相似文献
333.
Travel demand model system for the information era 总被引:5,自引:0,他引:5
The emergence of new information technologies and recent advances in existing technologies have provided new dimensions for travel demand decisions. In this paper we propose a comprehensive travel demand modeling framework to identify and model the urban development decisions of firms and developers and the mobility, activity and travel decisions of individuals and households, and to develop a system of models that can be used by decision makers and planners to evaluate the effects of changes in the transportation system and development of information technologies (e.g. various tele-commuting, tele-services and Intelligent Transportation Systems).The implementation of an operational model system based on this framework is envisioned as an incremental process starting with the current best practice of disaggregate travel demand model systems. To this end, we present an activity-based model system as the first stage in the development of an operational model system. 相似文献
334.
335.
Individuals processing the information in a stated choice experiment are typically assumed to evaluate each and every attribute offered within and between alternatives, and to choose their most preferred alternative. However, it has always been thought that some attributes are ignored in this process for many reasons, including a coping strategy to handle ones perception of the complexity of the choice task. Nonetheless, analysts typically proceed to estimate discrete choice models as if all attributes have influenced the outcome to some degree. The cognitive processes used to evaluate trade-offs are complex with boundaries often placed on the task to assist the respondent. These boundaries can include prioritising attributes and ignoring specific attributes. In this paper we investigate the implications of bounding the information processing task by attribute elimination through ignoring one or more attributes. Using a sample of car commuters in Sydney we estimate mixed logit models that assume all attributes are candidate contributors, and models that assume certain attributes are ignored, the latter based on supplementary information provided by respondents. We compare the value of travel time savings under the alternative attribute processing regimes. Assuming that all attributes are not ignored and duly processed, leads to estimates of parameters which produce significantly different willingness to pay (WTP) to that obtained when the exclusion rule is invoked. 相似文献
336.
The daily activity-travel patterns of individuals often include interactions with other household members, which we observe in the form of joint activity participation and shared rides. Explicit representation of joint activity patterns is a widespread deficiency in extant travel forecasting models and remains a relatively under-developed area of travel behavior research. In this paper, we identify several spatially defined tour patterns found in weekday household survey data that describe this form of interpersonal decision-making. Using pairs of household decision makers as our subjects, we develop a structural discrete choice model that predicts the separate, parallel choices of full-day tour patterns by both persons, subject to the higher level constraint imposed by their joint selection of one of several spatial interaction patterns, one of which may be no interaction. We apply this model to the household survey data, drawing inferences from the household and person attributes that prove to be significant predictors of pattern choices, such as commitment to work schedules, auto availability, commuting distance and the presence of children in the household. Parameterization of an importance function in the models shows that in making joint activity-travel decisions significantly greater emphasis is placed on the individual utilities of workers relative to non-workers and on the utilities of women in households with very young children. The model and methods are prototypes for tour-based travel forecasting systems that seek to represent the complex interaction between household members in an integrated model structure. 相似文献
337.
The use of mathematical models in transportation and regional planning is limited by the need to obtain reasonably accurate, complete data sets. In particular complete spatial coverage is required for the usual discrete origin-destination models. Because of the time and cost constraints of obtaining such data, those charged with decision making responsibilities may choose to do without information that could be provided by quantitative models. This paper presents a procedure for estimating origin-constrained flows in situations where complete data collection is difficult or impossible. To this end an abstract model of origin-constrained travel is formulated. The required urban fields are constructed using interpolation and/or approximation techniques applied to available data. The tractability of the general model is demonstrated in the case of estimating the energy consumed in travel to existing or proposed facilities. The ability of the model to function with incomplete data was tested by using it to predict travel to the major retail centers located in the Albany-Schenectady-Troy Metropolitan Area. 相似文献
338.
This paper reivews a programme recently undertaken by the Irish Government aimed at reforming the administration of Irish ports. Arising from that programme, and as a result of legislative changes, eight key ports were vested as commerical harbour companies (prior to this they were administered by large Boards and were very restricted in their ability to perform commercially). The context for the paper is the global trend towards port reformation, and the paper draws particuarly on the effects of the privatization of UK ports. The paper starts with a review of the role of parts, both generally and within the context of Ireland's growing, geographically peripheral, economy. Observations of the UK ports privatization process are next considered. The history, development and recent performance of Irish ports, together with port investment strategies, are critiqued and the background to the recent programme of administrative reform undertaken by the Irish Government concerning the ports is reviewed. Various observations from a number of sources (including 12 interviews by the authors with key actors in the sector) on the reform process are discussed. It is concluded that there is no uniformity of opinion as to the suitability of the chosen model for Irish ports administration and that it is too soon to judge whether it has been a success (the eight ports were commercialized in March 1997). The paper concludes that, given the critical role of ports within the Irish economy, the situation should be periodically reviewed to ascertain the current applicability of the extant port administration model. 相似文献
339.
340.
Inrecent years, a debate has brewed over whether the decentralization of employment has been beneficial from a regional standpoint. In this article, we focus on one aspect of the debate: how the relocation of office workers from a downtown to a suburban location affects commuting patterns and mode choice. From a survey of 320 former downtown San Francisco workers who now work in the suburbs, we found that the average distance traveled remained essentially unchanged and that the average commuting speed increased. The most dramatic change, however, was the switch from public transit to drive-alone commuting. In the aggregate, we estimate that the change in job location was associated with nearly a threefold increase in vehicle miles traveled to work. While from a personal standpoint, employees seemed better off since they got to work faster and more comfortably, from a larger social and environmental perspective, the costs could be significant. More detailed analyses of commuter submarkets revealed that the transportation impacts vary considerably depending on whether the original residence was in the suburbs or central city and whether relocated workers had moved their residences in recent years. In general, those who remained in San Francisco and became reverse commuters were worst off whereas those who moved their residences out of the city were much better off in terms of job access. The article concludes that road pricing would be the best way to force motorists to internalize the external costs of increased drive-alone commuting. Second-best options would be to introduce development impact fees or employer-based trip reduction regulations. 相似文献