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41.
42.
This paper aims to gain more insight into the implications of information provision to drivers on the performance of road transport networks with recurrent congestion. For this purpose, a simulation program consisting of three components has been written. The first component is the traffic simulation model, the second component is the information provision mechanism, and the third component monitors the behavioural decision-making process of the drivers, which is modelled using a utility-based satisficing principle. Three types of information provision mechanisms will be considered: information based upon own-experience, after-trip information and real-time en route information. The findings in this paper, obtained in a hypothetical context, underline the important relationship betweenoverreaction, thelevel of market penetration and thequality of the information. High quality information allows a high level of market penetration, while low quality information, even when provided at low levels of market penetration, induces overreaction. Furthermore, real-time en route information is in particular beneficial during the process leading to a steady state; it reduces the variance in travel time considerably. The paper concludes with a discussion on the market potential of motorist information systems when commercially marketed. 相似文献
43.
J. A. Sparenberg 《Journal of Marine Science and Technology》1997,2(2):53-61
The axial force induced on a duct (duct thrust) which surrounds a propulsor is, by means of an energy conservation argument,
expressed in terms of the thrust and power of the propulsor and the kinetic energy losses per unit of time of the propulsor
and the duct. Emphasis is put on the linear theory of an axisymmetric ducted actuator disk, where it is shown that the work
done by the duct thrust is equal to the extra work done by the actuator disk when it is surrounded by the duct. This simplified
model gives more insight into the interaction between the propeller and the duct and on the limits of linearization. 相似文献
44.
45.
Effect of capacity concentration on highway corridor performance 总被引:1,自引:0,他引:1
Randolph W. Hall 《Transportation Research Part A: Policy and Practice》1997,31(6):475-491
This paper investigates, through use of analytical models, the effects of capacity concentration on highway corridor performance. It concludes that when highways operate at a fixed total capacity, decreasing the highway spacing can increase the average travel time because highways will become more congested. When highways operate below capacity, decreasing the spacing is usually beneficial as it tends to reduce trip length when accessing highways, and allows a greater percentage of travel to be completed on highways instead of arterials. 相似文献
46.
47.
All developments on air pollution by ships are fairly recent. Annex VI of the international Marpol-convention, regulating
the emissions of CFCs, Halons, Volatile Organic Compounds (VOCs) from cargoes, emissions from incinerators and exhaust gas
emissions from engines (NOx and SOx) entered into force in May 2005. The International Maritime Organization is currently discussing an upgrade of the air pollution
issues covered by Annex VI and some that are not in Annex VI, such as greenhouse gas emissions. CO2 is the most important greenhouse gas emitted by ship. Fuel consumption by the world merchant fleet is expected to grow to
between 250–300 million tons per year with corresponding CO2 emissions of 800–960 million tons per year. In Western Europe land based measures have reduced sulphur emissions substantially,
leaving shipping as an important remaining source of these emissions. Average sulphur content of heavy fuel oils is 3%, with
a limit of 4.5% imposed by Annex VI. Both the Baltic- and the North Sea have the status of SOx emission control area, limiting sulphur content to 1.5%. 相似文献
48.
The nature of the global economy is one of dynamic change. Shipping is a service industry with its demand related to changes in international trade levels and patterns. As a consequence shipping is subject to sometimes unpredictable swings in demand so that the operator is required to make strategic planning decisions while navigating through boom or bust environments. While boom economies generate rising freight rates which are welcomed and encourage investment, ship operators may also have to face falling freight demand and declining freight rates that may have significant impact on profitability, often falling to uneconomic levels for extended periods. In such a period of uncertainty and declining profitability management will make operational decisions to reduce costs. However, shipping lines operate in a market environment so any decisions made to rationalize the trade may have significant long-term competitive implications. For example, traditional micro economic theory might suggest that the prudent strategy to adopt would be to close down the operation and reopen when the market conditions improve. In a world of certainty or when costs of taking this action are zero, this would be a valid strategy. However, because of fear of competitors taking up a line's market share if the shipping company exits, even temporarily, this strategy cannot be valued simply in terms of shut-down and start-up costs. A further consideration is the fact that standard capital budgeting techniques, such as Net Present Value (NPV), cannot incorporate the flexibility to respond to new information and strategic responses explicitly into their investment analysis. This paper will demonstrate the use of Real Option Analysis (ROA) to provide guidelines for decisions about closing operations in adverse market conditions. 相似文献
49.
50.
Barbara E. Baarsma Jan G. Lambooy 《Transportation Research Part D: Transport and Environment》2005,10(6):459-475
Externalities are uncompensated influences that are not expressed in a market but that affect the production possibilities or the welfare level of third parties. An example is the noise pollution in airport areas. Although air transport is an important source of economic growth and employment in many countries, the social and environmental problems connected with this sector are rising rapidly. Consequently, airports are becoming a matter of concern to many politicians. On what kind of values should they base their decisions as to further growth or consolidation of the current situation? In this paper we discuss two approaches, one based on mainstream, neo-classical, economics, and one based on institutional approaches, more in particular new institutional economics, which can be seen as a development complementary to the mainstream. 相似文献