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751.
Mark D. Aspinwall 《Maritime Policy and Management》2013,40(4):313-314
This article discusses the regulatory and operational issues which have recently confronted a number of U.S. ports as a result of their dredging programmers. It describes the environmental concerns which have led community groups to raise legal objections to the traditional practice of ocean dumping of dredged material, the federal/state regulatory framework within which these objections have been considered and recent legislative changes to that framework. The paper describes in some detail the specific case of the Port of New York and New Jersey, which has experienced severe delays in its dredging programme since 1992 (and a resulting loss of business) as well mounting costs for dredged material disposal. The paper concludes that, complicated as the technical problems involving dredged material disposal may be, it is the political and economic issues involved which are likely to be decisive in the eventual outcomes for affected ports. 相似文献
752.
D.W. Parvin jun. 《Maritime Policy and Management》2013,40(3):155-161
This paper provides general background information relating to the physical characteristics and operations of the Suez Canal. In connection with the future development of the Canal, the research programme currently being undertaken by a British consortium is outlined, with particular reference to the traffic system presently operating. 相似文献
753.
Jennifer A. Pazour Russell D. Meller Letitia M. Pohl 《Transportation Research Part A: Policy and Practice》2010,44(3):119-135
High-speed rail is often touted as a means to reduce congestion on the United States’ highways by removing passenger car traffic. But highway congestion can also be reduced by reducing the amount of freight traffic. So, given the advances in high-speed rail, the potential exists for developing a national high-speed network for freight distribution. To design such a network considering highway traffic and transit times, we present an uncapacitated network design model with a post-processing step for the capacity constraint. To illustrate how our modeling approach could be used by policy makers to evaluate the impacts of a high-speed rail network, we apply our models with preliminary data on high-speed rail operating parameters for freight applications and from current data on shipments from a major truckload carrier and the US Census Bureau. 相似文献
754.
Identification and assessment of aquatic resources for power plant sites on Maryland's Eastern shore
Anne D. Marble 《Coastal management》2013,41(1):49-70
Abstract A power plant siting procedure which accounts for the protection and preservation of aquatic resources, defined as sensitive life forms and life stages of economically valuable species of finfish and shellfish, is presented as it was executed on Maryland's Eastern Shore. Negative effects of power plant development and operation are generated principally by the cooling water intake and discharge system. The site‐selection procedure is thus presented as a two‐faceted process, termed regional screening, requiring the separate but simultaneous identification of land‐based sites and cooling systems. Criteria included in regional screening for cooling systems reflected life‐sustaining processes essential to the maintenance of aquatic resources. Major sources of effects of power plants on aquatic resources and siting principles as they affect aquatic resources are defined. Information‐gathering techniques included extensive interviews with key research scientists, state personnel, and numerous Chesapeake Bay watermen. 相似文献
755.
756.
Abstract In 1967, a new road facilitated access to a number of small, impoverished, rural communities in a marshy region along Mexico's Pacific coast. One of these—the only one situated on the Pacific shore—began to be visited by an increasing stream of tourists. This article discusses the severe sociocultural problems which the initial phase of tourism development caused in Teacapán, and argues that these are part of a syndrome which is manifest in similar situations worldwide. By anticipating this syndrome before tourism development gets underway, planners and managers of coastal tourism development in Third World nations would be better prepared to mitigate most of its severe effects. 相似文献
757.
从2009年中国取代美国成为世界上最大的汽车市场以来,汽车制造商已然进入了一场激烈的扩张竞赛。在过去两年里,数万亿元人民币涌入汽车制造行业。汽车制造商开始疯狂地扩大产能。按照这种扩张速度,中国的汽车年产能到201 3年将增至31 00万辆,达到2009年产能的两倍。而在中国开展业务的国际汽车制造商则显得保守一些。过去四年里,在占据全国乘用车一半产量的情况下, 相似文献
758.
Brian D. Taylor Douglas Miller Hiroyuki Iseki Camille Fink 《Transportation Research Part A: Policy and Practice》2009,43(1):60-77
Public subsidy of transit services has increased dramatically in recent years, with little effect on overall ridership. Quite obviously, a clear understanding of the factors influencing transit ridership is central to decisions on investments in and the pricing and deployment of transit services. Yet the literature about the causes of transit use is quite spotty; most previous aggregate analyses of transit ridership have examined just one or a few systems, have not included many of the external, control variables thought to influence transit use, and have not addressed the simultaneous relationship between transit service supply and consumption. This study addresses each of these shortcomings by (1) conducting a cross-sectional analysis of transit use in 265 US urbanized areas, (2) testing dozens of variables measuring regional geography, metropolitan economy, population characteristics, auto/highway system characteristics, and transit system characteristics, and (3) constructing two-stage simultaneous equation regression models to account for simultaneity between transit service supply and consumption. We find that most of the variation in transit ridership among urbanized areas – in both absolute and relative terms – can be explained by factors outside of the control of public transit systems: (1) regional geography (specifically, area of urbanization, population, population density, and regional location in the US), (2) metropolitan economy (specifically, personal/household income), (3) population characteristics (specifically, the percent college students, recent immigrants, and Democratic voters in the population), and (4) auto/highway system characteristics (specifically, the percent carless households and non-transit/non-SOV trips, including commuting via carpools, walking, biking, etc.). While these external factors clearly go a long way toward determining the overall level of transit use in an urbanized area, we find that transit policies do make a significant difference. The observed range in both fares and service frequency in our sample could account for at least a doubling (or halving) of transit use in a given urbanized area. Controlling for the fact that public transit use is strongly correlated with urbanized area size, about 26% of the observed variance in per capita transit patronage across US urbanized areas is explained in the models presented here by service frequency and fare levels. The observed influence of these two factors is consistent with both the literature and intuition: frequent service draws passengers, and high fares drive them away. 相似文献
759.
Increase in particle number emissions from motor vehicles due to interruption of steady traffic flow
E.R. Jayaratne L. Wang D. Heuff L. Morawska L. Ferreira 《Transportation Research Part D: Transport and Environment》2009,14(7):521-526
We assess the increase in particle number emissions from motor vehicles driving at steady speed when forced to stop and accelerate from rest. Considering the example of a signalized pedestrian crossing on a two-way single-lane urban road, we use a complex line source method to calculate the total emissions produced by a specific number and mix of light petrol cars and diesel passenger buses and show that the total emissions during a red light is significantly higher than during the time when the light remains green. Replacing two cars with one bus increased the emissions by over an order of magnitude. 相似文献
760.
The new freedoms in design that electric powertrains offer lead to a wide variety of configurations to consider when developing an electric vehicle (EV) from scratch. Furthermore, the strong relation of the battery size with vehicle weight, range and performances leads to a set of interrelated dependencies that can result in many design loops to fulfil the vehicle targets, market constraints and regulations simultaneously. The paper presents a pre-design tool to assist the electric vehicle development process by representing the different constraints and the possible feasible solutions in a single plot with the need of a small amount of inputs accesible to assess at pre-design phase. As a result, the tool depicts a set of feasible vehicle configurations that could fulfil the targets easing the interaction and loops among different expertise areas. To better assist selection, it also provides a sensitivity analysis of the performances to selected inputs and the user can introduce a cost function depending on vehicle weight and battery size. The tool is based on the vehicle longitudinal dynamics equations and equations that model the market and regulations constraints. It is aimed at providing an overview of the main specifications for component selection avoiding detailed vehicle modelling in the early pre-design phase at which the vehicle characteristics and even powertrain architecture are unknown. Finally, the tool results quality is evaluated by further developing one of its solutions for passenger car in four different vehicle configurations with the simulation software vemSim and AVL Cruise. The results of the simulations are compared to the solution of the pre-design tool to evaluate the level of fidelity and the deviations in the final result that can appear depending on the final architecture, components characteristics and control strategy. 相似文献