全文获取类型
收费全文 | 883篇 |
免费 | 8篇 |
专业分类
公路运输 | 308篇 |
综合类 | 36篇 |
水路运输 | 289篇 |
铁路运输 | 33篇 |
综合运输 | 225篇 |
出版年
2023年 | 10篇 |
2022年 | 20篇 |
2021年 | 9篇 |
2020年 | 8篇 |
2019年 | 7篇 |
2018年 | 34篇 |
2017年 | 14篇 |
2016年 | 30篇 |
2015年 | 7篇 |
2014年 | 30篇 |
2013年 | 131篇 |
2012年 | 33篇 |
2011年 | 47篇 |
2010年 | 35篇 |
2009年 | 46篇 |
2008年 | 47篇 |
2007年 | 21篇 |
2006年 | 10篇 |
2005年 | 17篇 |
2004年 | 18篇 |
2003年 | 5篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 14篇 |
1999年 | 10篇 |
1998年 | 23篇 |
1997年 | 14篇 |
1996年 | 19篇 |
1995年 | 16篇 |
1994年 | 5篇 |
1993年 | 7篇 |
1992年 | 12篇 |
1991年 | 8篇 |
1990年 | 11篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 8篇 |
1984年 | 9篇 |
1983年 | 12篇 |
1982年 | 7篇 |
1981年 | 12篇 |
1980年 | 8篇 |
1979年 | 15篇 |
1977年 | 15篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1974年 | 8篇 |
1973年 | 5篇 |
排序方式: 共有891条查询结果,搜索用时 15 毫秒
201.
This study reports on scientist/crew relations aboard research vessels at sea. It is a case study in a case study in a long-range project dealing with the relations of natural scientists in the U.S.A. to various segments of the lay population. An earlier paper dealt with the interaction of scientists and Government policy makers during the science-advisory process [1]. In that study we found that the frustration was reciprocal; scientists and policy makers were equally vocal on what was wrong with ‘ the other groups’. The present research, by comparison, focuses on scientists and members of ‘the working class’. Here we find the frustration rather one-sided, reflecting the differences in status and power of the two groups. On a research vessel, science and scientists control the lives and careers of the mariners. In the science-advising committee, members of both government and science meet as social equals. In this paper elements of conflict between scientists and crew on a research vessel are described. It is suggested that conflict between these two groups is the inevitable result of extending the ‘intellectual’/‘worker’ class conflict of our society to a closed space at sea. The controlling mechanism of the conflict may be called ‘subcultural privacy’, a mechanism worked out by mariners to cope with the disrupting effects of a constant stream of strangers into their sea-going home. The mechanism takes the form of institutionalized ‘bitching’ and systematic physical separation of scientists and crew during critical periods of the day. It is suggested that attempts to create greater crew/scientist harmony by forcing by greater interaction (and thus a breakdown of subcultural privacy) will be counter productive. 相似文献
202.
E. D. Brown 《Maritime Policy and Management》2013,40(6):325-350
It is highly probable that one of the results of the Third United Nations Conference on the Law of the Sea will be the recognition of a new jurisdictional zone—the exclusive economic zone (EEZ). This 200-mile zone will be used for a variety of potentially conflicting purposes by both the coastal state and non-coastal states and it is therefore important to ensure that the new convention emerging from the conference should establish criteria and make provision for machinery for the resolution of the international conflicts between different users which will undoubtedly arise. This paper contains a critical analysis of the latest draft articles under consideration at the Conference and considers the criteria by reference to which disputes might be resolved. 相似文献
203.
The U.S. Army Corps of Engineers administers the only nationwide regulatory program that controls development activities in U.S. waters and wetlands. This article examines the statutory authorities, jurisdictional limitations, and evolution of the current Corps regulations, which express a strong policy to protect wetlands, estuaries, and tidal waters from unnecessary dredging, filling, or other alteration. The article explains the organization and procedures of the U.S. Army Corps of Engineers and examines in detail several precedential permit cases which have developed and implemented the Corps “wetlands policy.”; The article also evaluates current and potential policies underlying the regulatory efforts of the Corps of Engineers. 相似文献
204.
This article examines the suitability and potential advances of decision-theoretic models from finance regarding investment decisions in shoreline stabilization projects. A set of scenarios represents the dynamics of the decision-state facing the planner and identifies factors that should be incorporated into the decision-making process. It is shown that decision models from finance can account for the risk and uncertainty inherent in shoreline stabilization projects, potentially suggest improvements and refinements to presently used cost-benefit analysis procedures, and offer new tools that can aid in decisions concerning provision of shoreline stabilization. The outcomes of these scenarios justify better planning and control of existing and future building, and that of poststorm policies. Lastly, these models allow us to explore the range of our understanding of coastal processes and interactions with shoreline stabilization projects and can identify new and useful data needed in coastal management and hazard management decisions. 相似文献
205.
F. Gao D. F. Dang S. S. Huang S. E. Li 《International Journal of Automotive Technology》2017,18(1):157-164
Platoon driving has potential to significantly benefit road traffic. This study presents a decoupled robust control strategy for a vehicular platoon with identical feedback controller and rigid information topology. The node dynamics of vehicle with a lower-level controller is assumed to be covered by a multiplicative uncertainty model. The vehicular platoon control system is skillfully decomposed into an uncertain part and a diagonal system by applying linear transformation and eigenvalue decomposition on information flow graph. Then the requirements of robust stability and distance tracking error are equivalent to the H-infinity norm of decoupled sub-systems. Comparative simulations with a non-robust controller and different communication topologies are conducted to demonstrate the robust stability and distance tracking performances of the proposed method. 相似文献
206.
Stephen D. Clark 《Transportation Research Part C: Emerging Technologies》2009,17(4):381-393
This paper applies the relatively new knowledge discovery technique of Rough set analysis to identify the factors that influence the level of car ownership in a household. The study uses the detailed Great Britain National Travel Survey data set which contains information on both household and individual travel behaviour. The knowledge extraction is done using the theory of Rough sets and is presented in the form of easily understood if-then statements or rules which reveal how each attribute influences car ownership behaviour. These rules can then be used to predict household car ownership from information held about previously unseen households and the classification performance of the rules can be assessed. The performance of this classification task is shown to be on a par with other reported studies in this area. 相似文献
207.
Jason C. Lau W.T. Hung David D. Yuen C.S. Cheung 《Transportation Research Part D: Transport and Environment》2009,14(5):353-359
Carbon monoxide is a major contributor to air pollution in urban cities, particularly at the roadside. Hourly, monthly and seasonal mean carbon monoxide concentration data are collected from a roadside air monitoring station in Hong Kong over 7-years. The station is a few metres from a major intersection surrounded by tall buildings. In particular, hourly patterns of concentrations on different days of the week are investigated. The data show that hourly carbon monoxide concentrations resemble the traffic pattern of the area and tend to be lower in the summer. Using a seasonal autoregressive integrated moving average models shows that the daily traffic cycle strongly influences concentrations. Further, it is found that urban roadside carbon monoxide monitoring data exhibits a long-memory process, suggesting that a model incorporating long memory and seasonality effects is needed simulate urban roadside air quality. 相似文献
208.
D. B. Agusdinata J. W. G. M. van der Pas W. E. Walker V. A. W. J. Marchau 《先进运输杂志》2009,43(4):413-454
Road safety is a policy priority due to the high casualties and costs associated with road accidents. Since speed is a major cause of road accidents, in‐vehicle speed limiters or Intelligent Speed Adaptation (ISA), seems a promising solution. ISA implementation, however, is hindered by large uncertainties, for example about the impacts of ISA, the way users might respond to ISA, and the relationship between speed and accidents. Traditional Multi‐Criteria Analysis (MCA) has limitations in handling these uncertainties. We present an MCA approach based on exploratory modeling, which uses computational experiments to explore the multiple outcomes of ISA policies (safety, emissions, throughput, and cost) across a range of future demand scenarios, functional relationships for performance criteria, and user responses to ISA. As an illustration, by testing the impacts of different ISA penetration levels on two driver groups, we show that when compliance with ISA is expected to be low, a policy aimed only at novice drivers outperforms other ISA policies on safety improvement. 相似文献
209.
This paper is about distance and time as factors of competitiveness of intermodal transport. It reviews the relevance of the factors, evaluates time models in practice, compares network distances and times in alternative bundling networks with geometrically varied layouts, and points out how these networks perform in terms of vehicle scale, frequency and door-to-door time. The analysis focuses on intermodal transport in Europe, especially intermodal rail transport, but is in search for generic conclusions. The paper does not incorporate the distance and time results in cost models, and draws conclusions for transport innovation, wherever this is possible without cost modelling. For instance, the feature vehicle scale, an important factor of transport costs, is analysed and discussed.Distance and time are important factors of competitiveness of intermodal transport. They generate (direct) vehicle costs and – via transport quality – indirect costs to the customers. Clearly direct costs/prices are the most important performance of the intermodal transport system. The relevance of quality performances is less clarified. Customers emphasise the importance of a good match between the transport and the logistic system. In this framework (time) reliability is valued high. Often transport time, arrival and departure times, and frequency have a lower priority. But such conclusions can hardy be generalised. The range of valuations reflects the heterogeneity of situations. Some lack of clarity is obviously due to overlapping definitions of different performance types.The following parts of the paper are about two central fields of network design, which have a large impact on transport costs and quality, namely the design of vehicle roundtrips (and acceleration of transport speed) and the choice of bundling type: do vehicles provide direct services or run in what we call complex bundling networks? An example is the hub-and-spoke network. The objective of complex bundling is to increase vehicle scale and/or transport frequency even if network volumes are restricted. Complex bundling requires intermediate nodes for the exchange of load units. Examples of complex bundling networks are the hub-and-spoke network or the line network.Roundtrip and bundling design are interrelated policy fields: an acceleration of the roundtrip speed, often desirable from the cost point of view, can often only be carried out customer friendly, if the transport frequency is increased. But often the flow size is not sufficient for a higher frequency. Then a change of bundling model can be an outcome.Complex bundling networks are known to have longer average distances and times, the latter also due to the presence of additional intermediate exchange nodes. However, this disadvantage is – inside the limits of maximal vehicle sizes – overruled by the advantage of a restricted number of network links. Therefore generally, complex bundling networks have shorter total vehicle distances and times. This expression of economies of scale implies lower vehicle costs per load unit.The last part of the paper presents door-to-door times of load units of complex bundling networks and compares them with unimodal road transport. The times of complex bundling networks are larger than that of networks with direct connections, but nevertheless competitive with unimodal road transport, except for short distances. 相似文献
210.
Harvey J. Miller John D. Storm 《Transportation Research Part C: Emerging Technologies》1996,4(6):373-389
Travel demand analyses are useful for transportation planning and policy development in a study area. However, travel demand modeling faces two obstacles. First, standard practice solves the four travel components (trip generation, trip distribution, modal split and network assignment) in a sequential manner. This can result in inconsistencies and non-convergence. Second, the data required are often complex and difficult to manage. Recent advances in formal methods for network equilibrium-based travel demand modeling and computational platforms for spatial data handling can overcome these obstacles. In this paper we report on the development of a prototype geographic information system (GIS) design to support network equilibrium-based travel demand models. The GIS design has several key features, including: (i) realistic representation of the multimodal transportation network, (ii) increased likelihood of database integrity after updates, (iii) effective user interfaces, and (iv) efficient implementation of network equilibrium solution algorithms. 相似文献