全文获取类型
收费全文 | 7916篇 |
免费 | 105篇 |
专业分类
公路运输 | 1703篇 |
综合类 | 587篇 |
水路运输 | 2539篇 |
铁路运输 | 771篇 |
综合运输 | 2421篇 |
出版年
2023年 | 43篇 |
2022年 | 113篇 |
2021年 | 56篇 |
2019年 | 81篇 |
2018年 | 194篇 |
2017年 | 114篇 |
2016年 | 140篇 |
2015年 | 91篇 |
2014年 | 241篇 |
2013年 | 1223篇 |
2012年 | 323篇 |
2011年 | 390篇 |
2010年 | 236篇 |
2009年 | 372篇 |
2008年 | 302篇 |
2007年 | 270篇 |
2006年 | 232篇 |
2005年 | 271篇 |
2004年 | 293篇 |
2003年 | 183篇 |
2002年 | 148篇 |
2001年 | 132篇 |
2000年 | 140篇 |
1999年 | 99篇 |
1998年 | 129篇 |
1997年 | 112篇 |
1996年 | 139篇 |
1995年 | 149篇 |
1994年 | 85篇 |
1993年 | 189篇 |
1992年 | 160篇 |
1991年 | 77篇 |
1990年 | 83篇 |
1989年 | 57篇 |
1988年 | 74篇 |
1987年 | 66篇 |
1986年 | 59篇 |
1985年 | 78篇 |
1984年 | 73篇 |
1983年 | 73篇 |
1982年 | 73篇 |
1981年 | 95篇 |
1980年 | 68篇 |
1979年 | 91篇 |
1978年 | 56篇 |
1977年 | 69篇 |
1976年 | 53篇 |
1975年 | 65篇 |
1974年 | 50篇 |
1973年 | 45篇 |
排序方式: 共有8021条查询结果,搜索用时 22 毫秒
751.
752.
Central to the development of transport energy plans are predictions of automobile use. Together with a knowledge of the fuel efficiency of the vehicle fleet, usage acts interdependently to determine the amount of fuel consumed. In this paper we develop an econometric model system at the household level which treats vehicle use, fuel cost, and vehicle fuel efficiency as functionally interdependent. The data is drawn from Wave 1 of a4‐wave panel of Sydney households. The empirical evidence provides new insights into the influences on vehicle use and sets the context for continuing research efforts. 相似文献
753.
754.
Abstract A territorial sea comprising 6.7 million acres of offshore lands extending three geographic miles into the Atlantic Ocean three marine leagues (nine geographic miles) into the Gulf of Mexico makes Florida the second largest “oceanowning”; state in the contiguous United States. Florida's history, climate, economic development, and worldwide reputation have evolved from the state's relationship with the sea. The state is now becoming aware that aggressive management of its ocean resources is necessary to preserve the future of that relationship. The purpose of this article is to present some of Florida's recent legal and policy initiatives that have been directed toward better understanding and management of ocean resources and uses. 相似文献
755.
Theo E. Notteboom 《Maritime Policy and Management》2013,40(3):257-269
The first part of this paper brings into discussion some recent changes in the dynamics of the European container handling business, in particular as a result of vertical and horizontal integration strategies of container terminal operators. The industry structure has become sufficiently consolidated to raise a fundamental question about whether market forces are sufficient to prevent the abuse of market power. In this context, reference is made to the theory of contestable markets. The second part of the paper looks more closely to the issue of contestability by means of an exploratory and qualitative study of elements that could prevent other players entering or exiting the European container handling market. As such, a first indication is given of the degree of contestability in the container handling industry. 相似文献
756.
Abstract The estimation of annual average daily traffic (AADT) is an important parameter collected and maintained by all US departments of transportation. There have been many past research studies that have focused on ways to improve the estimation of AADT. This paper builds upon previous research and compares eight methods, both traditional and cluster-based methodologies, for aggregating monthly adjustment factors for heavy-duty vehicles (US Department of Transportation Federal Highway Administration (FHWA) vehicle classes 4–13). In addition to the direct comparison between the methodologies, the results from the analysis of variance show at the 95% confidence level that the four cluster-based methods produce statistically lower variance and coefficient of variation over the more traditional approaches. In addition to these findings – which are consistent with previous total volume studies – further analysis is performed to compare total heavy-duty monthly adjustment factors, both directions of traffic, with direction-based monthly adjustment factors. The final results show that the variance as well as the coefficient of variation improve on average by 25% when directional aggregate monthly adjustment factors are used instead of total direction. 相似文献
757.
Safety modeling for two‐way left‐turn lanes and a procedure to identify two‐way left‐turn lane segments with safety concerns 下载免费PDF全文
In the past, two‐way left‐turn lane (TWLTL) median treatments have been frequently used in Florida to inexpensively improve traffic and safety performances. In order to identify factors that may have significant impacts on safety operations in TWLTL sections and to identify TWLTL locations that present existing and future safety concerns, a research project was carried out and results are summarized in the paper. In the research, a three‐year crash history database with crashes and section characteristics from a total of 1688 TWLTL sections all over Florida was developed and used. A negative binomial regression model was developed to determine the statistical relationship between the number of crashes per mile per year and several variables such as traffic volume, access density, posted speed, and number of lanes. In regard to the methodology, in order to identify locations with safety concerns, several steps are needed: development of real crash data distribution, determination of statistical distribution models that better represent the actual crash data, determination of percentile values for the average number of crashes, estimation of crash rates for sections with the same characteristics, estimation of critical values for the variables corresponding to the percentile values for average number of crashes, calculation of tables of critical average annual daily traffic values, and generation of a list of TWLTL locations with critical safety concerns. Results presented in the paper have been used in real applications. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
758.
Richard E. Allsop 《先进运输杂志》2001,35(2):97-103
Implications of the difference between planned and market‐determined public transport services for the modelling of the transport system and its use are examined. In the former case, the task for government seeking to optimise performance of the transport system has a standard bi‐level form, but in the latter case, the lower‐level problem in the bi‐level formulation is to determine mutually consistent solutions to a pair of optimisation problems. The relevance of the mutually consistent solution in this context is contrasted with its sometimes misleading role in the context of optimisation of urban traffic signal control. 相似文献
759.
An altimeter data assimilation scheme has been tested in the OCCAM (Ocean Circulation and Climate Advanced Modelling) global 1/4°, 36-level model using a twin experiment format. The Cooper and Haines displacement scheme is used. The method works well in most regions and depths. Currents and densities in the top 1000 m generally improve by over 50–70% after 5 months of sea level assimilation every 15 days. Below 1000 m, an error reduction of up to 50% is achieved. The errors remain low during a further 60-day run without assimilation. Diagnostics for the North Atlantic, the Tropical Pacific and the Antarctic Circumpolar Current are shown alongside the global averages.The main problems encountered were in weakly stratified regions of the Antarctic and Arctic seas. A scale selective filter is developed to avoid assimilating scales much larger than the local deformation radius, and this avoids the adverse assimilation effects in the southern oceans. A companion paper uses this scheme to assimilate TOPEX and ERS-1 altimeter maps. 相似文献
760.
The structure of the French rail network is highly centralized. It complies with the strategy of use of the incumbent operator, SNCF: the long-term trend has been rather towards the concentration of traffic on a limited number of well-equipped routes. The experience of freight market liberalization shows that seven newcomers have entered the market. They haul approximately 16% of the total volume in 2010. But they have neither the same vision of the network, nor the same use of it. They run point-to-point long-distance trains, so they try to travel via lines that are as direct as possible, thereby saving several kilometres and avoiding problematic bottlenecks. Their strategies are counteracted by the current state of the infrastructures when they try to avoid the main radial lines: limited capacity, speed and axle load restrictions, etc. Upgrading works are now in progress, under the direction of RFF, the network manager. They add perturbations to the existing restriction of use, without any satisfying alternative train path. This paper tries to emphasize the strategic divergences between operators confronted with a time-consuming (or insufficiently anticipated) network. 相似文献