全文获取类型
收费全文 | 2587篇 |
免费 | 21篇 |
专业分类
公路运输 | 948篇 |
综合类 | 84篇 |
水路运输 | 796篇 |
铁路运输 | 73篇 |
综合运输 | 707篇 |
出版年
2023年 | 26篇 |
2022年 | 72篇 |
2021年 | 22篇 |
2020年 | 17篇 |
2019年 | 23篇 |
2018年 | 132篇 |
2017年 | 84篇 |
2016年 | 111篇 |
2015年 | 32篇 |
2014年 | 120篇 |
2013年 | 357篇 |
2012年 | 135篇 |
2011年 | 146篇 |
2010年 | 140篇 |
2009年 | 143篇 |
2008年 | 132篇 |
2007年 | 67篇 |
2006年 | 54篇 |
2005年 | 53篇 |
2004年 | 38篇 |
2003年 | 40篇 |
2002年 | 30篇 |
2001年 | 29篇 |
2000年 | 41篇 |
1999年 | 31篇 |
1998年 | 32篇 |
1997年 | 42篇 |
1996年 | 36篇 |
1995年 | 50篇 |
1994年 | 24篇 |
1993年 | 26篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 15篇 |
1989年 | 13篇 |
1988年 | 16篇 |
1987年 | 14篇 |
1986年 | 11篇 |
1985年 | 19篇 |
1984年 | 17篇 |
1983年 | 15篇 |
1982年 | 22篇 |
1981年 | 28篇 |
1980年 | 18篇 |
1979年 | 34篇 |
1978年 | 12篇 |
1977年 | 18篇 |
1976年 | 9篇 |
1975年 | 10篇 |
1973年 | 8篇 |
排序方式: 共有2608条查询结果,搜索用时 415 毫秒
771.
Activity generation models are relatively poorly developed in activity-based travel demand modelling frameworks. This research investigates whether observed distributions of activity attributes (activity frequency, start time and duration) used as inputs in the activity generation component of an activity-based travel demand model have changed over time. This research empirically examines changes in the distributions of activity generation attributes over time in the Greater Montreal area (GMA), Quebec, Canada. It also focuses on how these attributes vary with peoples’ socio-demographic characteristics. This research relies on the 1998, 2003 and 2008 origin–destination (O–D) household travel surveys of the GMA. The comparative analysis at three time points in a 10-year period clearly reveals that distributions of activity attributes are significantly changing over time. Work and school activities show similar trends; frequency “1” has increased and frequency “2+” has decreased over time. The occurrence of shopping activity on weekdays is decreasing over time. Start time and duration distributions for each activity have also changed significantly over time. The research allows preparing activity attributes for the application of an activity-based model, TASHA, such that they reflect temporal changes in travel behaviour of the GMA. 相似文献
772.
Francisco J. Bahamonde-Birke Uwe Kunert Heike Link Juan de Dios Ortúzar 《Transportation》2017,44(3):475-493
We provide an in-depth theoretical discussion about the differences between individual-specific latent constructs (representing attitudes, for example, but also other characteristics such as values or personality traits) and alternative-specific latent constructs (that may represent perceptions) affecting the choice-making process of individuals; we also carry out an empirical exercise to analyze their effects. This discussion is of importance, as the majority of papers considering attitudinal latent variables just take these as attributes affecting directly the utility of a certain alternative, while systematic taste variations are rarely considered and perceptions are mostly ignored. The results of our case study show that perceptions may indeed affect the decision making process and that they are able to capture a significant part of the variability that is normally explained by alternative specific constants. Furthermore, our results indicate that attitudes may be a reason for systematic taste variations, and that a proper categorization of latent variables, in accordance with underlying theory, may outperform the customary assumption of linearity. 相似文献
773.
Most transportation research in the United States uses cross-sectional, “snapshot” data to understand levels of car access. Might this cross-sectional approach mask considerable variation over time and within households? We use a panel dataset, the Panel Study of Income Dynamics (PSID), for the years 1999–2011 to test this question. We find that for most families, being “carless” is a temporary condition. While 13 % of families in the US are carless in any given year, only 5 % of families are carless for all seven waves of data we examine in the PSID. We also find that poor families, immigrants, and people of color (particularly, blacks) are considerably more likely to transition into and out car ownership frequently and are less likely to have a car in any survey year than are non-poor families, the US-born, and whites. 相似文献
774.
Integrated land use and transportation forecasting models are used to assist decision-makers in the policy analysis and infrastructure capital improvement selection process. These models are typically given precise, point-estimate inputs that are mathematically linked, through a series of submodels, to forecasted model outputs. These point-estimate inputs represent an unrealistic level of precision and a growing body of research is focusing on statistical techniques to model uncertainty in model inputs and parameters and tracking the effects of this uncertainty through the various submodels to the model outputs. This paper presents an uncertainty analysis of the Large Zone Economic Module (LZEM) of the Simple, Efficient, Elegant, and Effective Model (SE3M) of land use and transportation. Three case-study implementations of the model are used to obtain a reasonably sound approximation of how uncertainty affects LZEM outputs: Guam, Puerto Rico, and Oahu, Hawaii. These case studies were the subject of an early transferability study with SE3M and were selected based on both their insularity and diverse physical, economic, and demographic geographies. The findings of this research demonstrate that LZEM has a robust framework, with the potential to estimate error both in the positive and negative direction under uncertain input/parameter conditions. 相似文献
775.
Procedures to transform GPS tracks into activity-travel diaries have been increasingly addressed due to their potential benefit to replace traditional methods used in travel surveys. Existing approaches for data annotation however are not sufficiently accurate, which normally involves a prompted recall survey for data validation. Imputation algorithms for transportation mode detection seem to be largely dependent on speed-related features, which may blur the quality of classification results, especially with transportation modes having similar speeds. Therefore, in this paper we propose an enhanced integrated imputation approach by incorporating the critical indicators related to trip patterns, reflecting the effects of uncertain travel environments, including bus stops and speed percentiles. A two-step procedure which embeds a segmentation model and a transportation mode inference model is designed and examined based on purified prompted recall data collected in a large-scale travel survey. Results show the superior performance of the proposed approach, where the overall accuracy at trip level reaches 93.2% and 88.1% for training and surveyed data, respectively. 相似文献
776.
Analytic hierarchy process application in selecting the mode of transport for a logistics company
下载免费PDF全文
![点击此处可从《先进运输杂志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
As a multi‐criteria decision‐making (MCDM) method, the analytic hierarchy process (AHP) has been used considerably to solve hierarchical or network‐based decision problems in socio‐economic fields. Following an in‐depth explanation of the transport function in logistics and an overview of the MCDM methods, the AHP model is employed in the paper for a logistics company in selecting the most suitable way of transportation between two given locations in Turkey. The criteria used in the selection of transportation modes are identified as the cost, speed, safety, accessibility, reliability, environmental friendliness, and flexibility. Several cost parameters (transportation, storage, handling, bosphorus crossover) are incorporated into the decision‐making process. The application is carried out in instructional character. The results of the study indicate that the railway transportation, which is not widely used in Turkey, is also an alternative and suitable means of transportation. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
777.
A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated... 相似文献
778.
779.
I-Huan Lee Yu-Huai Wang James T. Liu Wen-Ssn Chuang Jingping Xu 《Journal of Marine Systems》2009,76(4):397
Data from five separate field experiments during 2000–2006 were used to study the internal tidal flow patterns in the Gaoping (formerly spelled Kaoping) Submarine Canyon. The internal tides are large with maximum interface displacements of about 200 m and maximum velocities of over 100cm/s. They are characterized by a first-mode velocity and density structure with zero crossing at about 100 m depth. In the lower layer, the currents increase with increasing depth. The density interface and the along-channel velocity are approximately 90° out-of-phase, suggesting a predominant standing wave pattern. However, partial reflection is indicated as there is a consistent phase advance between sea level and density interface along the canyon axis. 相似文献
780.
Surface and box-cored sediments were collected along the Gaoping (formerly spelled Kaoping) Estuary–Canyon system and analyzed for As and Hg contents and speciation, 210Pb-based sedimentation rates and various geochemical parameters to elucidate the mechanisms that control natural and anthropogenic inputs of As and Hg from the Gaoping (Kaoping) River (KPR). The contents of As and Hg in surface sediments ranged from 1.84 to 20.7 mg kg− 1 and from 0.07 to 2.15 mg kg− 1, respectively, in the estuary and canyon. The concentrations generally decreased from the lower river toward the mixing boundary and then increased toward the estuarine mouth, followed by a slight variation in the canyon. Both As and Hg concentrations correlated strongly with clay, total organic carbon (TOC), Al, Fe and Mn contents in estuarine sediments but not necessary the same cases for canyon surface sediments. The factor analysis of surface sediments shows that the first two factors, which account for 75.6% of the variance, may represent major roles of carriers (clay, Al and Fe–Mn oxides) and TOC in controlling As and Hg distributions, respectively. Accordingly, the spatial patterns of the enrichments of As (1.9–16.2) and Hg (1.8–30.8) with reference to the crust levels follow the individual element's distribution patterns, likely because of deposition variability following inputs from the river. The contents of mobile As and Hg correlated substantially with the contents of both metals that were extracted with 0.1 M HCl. In addition to the major pool in the residual fraction (65–87%), As was relatively abundant in Fe–Mn oxides/hydroxides, whereas Hg was abundant in the organic/sulfide fraction. The deposition and accumulation rates of As and Hg in the canyon clearly decreased as the depth of water increased. The depth distributions of both metals are likely controlled primarily by TOC and Fe–Mn oxides associated factors followed by a contribution from anthropogenic pollution. The metal pollution appears to have increased substantially around 1970, following the economic boom in Taiwan, suggesting that modern sediments in the Gaoping (Kaoping) Canyon were derived from the Gaoping (Kaoping) River (KPR). 相似文献