全文获取类型
收费全文 | 1386篇 |
免费 | 19篇 |
专业分类
公路运输 | 543篇 |
综合类 | 49篇 |
水路运输 | 357篇 |
铁路运输 | 46篇 |
综合运输 | 410篇 |
出版年
2023年 | 14篇 |
2022年 | 37篇 |
2021年 | 15篇 |
2020年 | 8篇 |
2019年 | 14篇 |
2018年 | 29篇 |
2017年 | 36篇 |
2016年 | 67篇 |
2015年 | 20篇 |
2014年 | 76篇 |
2013年 | 185篇 |
2012年 | 86篇 |
2011年 | 81篇 |
2010年 | 74篇 |
2009年 | 83篇 |
2008年 | 62篇 |
2007年 | 24篇 |
2006年 | 28篇 |
2005年 | 32篇 |
2004年 | 22篇 |
2003年 | 28篇 |
2002年 | 28篇 |
2001年 | 21篇 |
2000年 | 24篇 |
1999年 | 21篇 |
1998年 | 14篇 |
1997年 | 20篇 |
1996年 | 18篇 |
1995年 | 24篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 9篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 17篇 |
1982年 | 10篇 |
1981年 | 12篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1977年 | 11篇 |
1976年 | 11篇 |
1975年 | 19篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 4篇 |
排序方式: 共有1405条查询结果,搜索用时 15 毫秒
991.
A. H. Vanags 《Maritime Policy and Management》1993,20(4):319-324
Conventional wisdom has it that, because of locational and other advantages, transit trade and transport, especially maritime transport, could be expected to play a major role in the development process of the Baltic States which was expected to follow their renewed independence in 1991. This paper secks to evaluate this proposition. The first section of the paper provides a brief account of the present state of the shipping and port sectors in the three Baltic republics and offers some speculation about likely future developments. The following section considers whether there is any historical basis for the presumption in favour of transit trade. The paper concludes with a somewhat speculative discussion of whether the Baltic States might be expected to possess any long run comparative advantage in maritime transport. It is suggested that in this respect a distinction should be made between ports and shipping and that in a more prosperous future, shipping, in particular, might be expected to decline in importance. 相似文献
992.
This paper summarises work done to assess the market potential and likely financial performance of a planned high-speed rail link connecting Sydney, Canberra and Melbourne, under a variety of scenarios concerning the services offered and the possible market responses of the competing transport modes in the corridor. In the Australian context, such a link has the characteristics of an essentially new transport mode since existing rail services are extremely poorly developed. The expectation was that generated demand could be a substantial part of the overall ridership. A programme of market research was commissioned by the private consortium considering the project, designed to support forecasting models capable of predicting both diverted and generated travel on the new service. A major survey of current travellers was conducted in 1988, followed by an extensive collection of stated preference evidence about the factors affecting the travel decisions of both existing travellers and those who had not recently made any journeys in the corridor. The paper focuses mainly on the design and organisation of the surveys, on the analysis approach, and on the methods used to generate forecasts for simulated populations and scenarios. 相似文献
993.
994.
Little is known about the sources of public support for transit systems even though the perceptions of transit users and potential users have been extensively documented. Research reported here examines dimensions of public support for the first U.S. downtown people mover during three critical phases in the system's life: construction, shakedown, and operations. The method employed was a community sample survey with home interviews. Data analysis showed that the public—who were virtually all nonusers—were largely favorable toward the system during the construction phase. During the shakedown phase, when system reliability was extremely low, many attitudes toward the system became less favorable, especially perceptions of performance and direct community impacts. Later, reliability improved, and attitudes which had become less favorable tended to grow more favorable once again. It is suggested that a system's performance can influence many aspects of public support for a transit system, even among nonusers. This pattern has implications for system planners who must depend on public good will for continuing support of transit systems. In particular, extensive pretesting of new systems should occur before the fare gates are opened to patrons. 相似文献
995.
996.
George H. K. Wang 《Transportation Research Part B: Methodological》1981,15(6):391-405
This paper examines the characteristics of rail freight traffic cycles from 1950 to 1976. Both the NBER's statistical indicator approach and time series approach are used to identify the leading indicators of rail freight traffic cycles from a set of leading economic indicators published by the Department of Commerce. The concepts and empirical results obtained by these two procedures are compared and contrasted. The interesting findings are: (1) the composite index of 12 leading indicators performs very well as a qualitative and quantitative predictor and (2) the empirical results obtained by the NBER approach are, in general, consistent with those obtained by the time series approach. 相似文献
997.
This paper presents eight empirical models of monthly ridership for seven U.S. Transit Authorities. Within the framework of these models, the impacts upon monthly ridership from changes in the real fare and gasoline prices are examined. Important findings are: (1) the elasticities of monthly transit ridership with respect to the real fare are negative and inelastic, ranging from 0.042 to 0.62; and (2) the elasticities of monthly transit ridership with respect to the real gasoline price are positive and inelastic, ranging from 0.08 to 0.80. Such results have important policy implications for decisions based on the relationships of price, revenue, and ridership; and for assessing the impacts of changing gasoline prices upon urban modal choice. 相似文献
998.
Michael S. Smith Göran Kauermann 《Transportation Research Part B: Methodological》2011,45(10):1846-1862
Cycling is attracting renewed attention as a mode of transport in western urban environments, yet the determinants of usage are poorly understood. In this paper we investigate some of these using intraday bicycle volumes collected via induction loops located at ten bike paths in the city of Melbourne, Australia, between December 2005 and June 2008. The data are hourly counts at each location, with temporal and spatial disaggregation allowing for the impact of meteorology to be measured accurately for the first time. Moreover, during this period petrol prices varied dramatically and the data also provide a unique opportunity to assess the cross-price elasticity of demand for cycling. Over-dispersed Poisson regression models are used to model volumes at each location and at each hour of the day. Seasonality and the impact of weather conditions are modelled as semiparametric and estimated using recently developed multivariate penalized spline methodology. Unlike previous studies that use aggregate data, the empirical results show a substantial meteorological and seasonal component to usage. They also suggest there was substitution into cycling as a mode of transport in response to increases in petrol prices, particularly during peak commuting periods and by commuters originating in wealthy and inner city neighbourhoods. Last, we extend the approach to a multivariate longitudinal count data model using a Gaussian copula estimated by Bayesian data augmentation. We find first order serial dependence in the hourly volumes and a ‘return trip’ effect in daily bicycle commutes. 相似文献
999.
Internal vibration of the valve spring is a critical factor in determining the dynamic characteristics of high-speed valve
train systems. Because precise prediction of the spring surge amplitude is a difficult problem, especially for nonlinear variable-pitch
springs, the development stage requires a process of trial and error. In the present study, a new method that considers the
variable natural frequency and variable damping ratio is proposed to predict the spring surge amplitude. First, the change
in the natural frequency and damping ratio caused by compression is predicted from the initially given pitch curve at the
free height. Second, the spring surge amplitude is estimated by solving the wave equation with nonlinear variable coefficients.
The surge amplitudes of typical valve springs are also measured using a motoring test rig and are compared with theoretical
results predicted by the spring drawing and cam profile data. 相似文献
1000.
Increasing bicycle use for utilitarian trips is a common city objective for health and environmental improvement and congestion reduction, but cyclists react heterogeneously to interventions and infrastructure. Understanding cyclist types helps in comprehending and planning for this diverse population. This study uses data from 2004 surveyed Montreal cyclists to generate a multidimensional cyclist typology based on seven factors derived from 35 variables, mostly proven determinants of the intensity of bicycle usage. The analysis revealed four distinct cyclist types: dedicated cyclists, path-using cyclists, fairweather utilitarians, and leisure cyclists. The cycling frequencies of each group respond differently to potential interventions and vary within commuting rate ranges with apparent minima and maxima. Building a network adapted to different cyclist types and emphasizing its convenience, flexibility and speed, could be an effective strategy to increase cycling mode share and frequency among the various groups. Findings from this study can be of benefit to transportation engineers, planners and policy makers as they help in better understanding the impacts of various interventions on the different groups of cyclists. 相似文献