全文获取类型
收费全文 | 1826篇 |
免费 | 24篇 |
专业分类
公路运输 | 433篇 |
综合类 | 333篇 |
水路运输 | 468篇 |
铁路运输 | 162篇 |
综合运输 | 454篇 |
出版年
2023年 | 14篇 |
2022年 | 44篇 |
2021年 | 30篇 |
2020年 | 17篇 |
2019年 | 22篇 |
2018年 | 60篇 |
2017年 | 38篇 |
2016年 | 72篇 |
2015年 | 32篇 |
2014年 | 53篇 |
2013年 | 206篇 |
2012年 | 99篇 |
2011年 | 132篇 |
2010年 | 109篇 |
2009年 | 127篇 |
2008年 | 97篇 |
2007年 | 102篇 |
2006年 | 91篇 |
2005年 | 82篇 |
2004年 | 28篇 |
2003年 | 16篇 |
2002年 | 17篇 |
2001年 | 25篇 |
2000年 | 33篇 |
1999年 | 13篇 |
1998年 | 24篇 |
1997年 | 15篇 |
1996年 | 18篇 |
1995年 | 38篇 |
1994年 | 8篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 12篇 |
1988年 | 7篇 |
1987年 | 7篇 |
1986年 | 8篇 |
1985年 | 17篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 12篇 |
1980年 | 10篇 |
1979年 | 5篇 |
1978年 | 8篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有1850条查询结果,搜索用时 15 毫秒
131.
132.
Vincent van den Berg Erik T. Verhoef 《Transportation Research Part B: Methodological》2011,45(1):60-78
When analysing the effects of transport policies it is important to adequately control for heterogeneity: previous studies note that ignoring heterogeneity biases the estimated welfare effects of tolling. This paper examines the effects of tolling, in a bottleneck model, with a continuously distributed value of time. With homogeneous users, first-best public tolling has no effect on prices. With heterogeneity it does: low values of time lose, and high values of time gain. The average congestion externality decreases with the heterogeneity in the value of time. Consequently, the welfare gain of first-best tolling also decreases. The more heterogeneous the value of time is, the lower the relative efficiency of a public pay-lane. This finding contrasts with the previous literature. Earlier studies, using static flow congestion, conclude that the relative efficiency increases with this type of heterogeneity. With more heterogeneity in the value of time, the relative efficiency of a private pay-lane is also lower, while that of a public time-invariant toll is higher. Our results suggest that the welfare gains of different tolling schemes are affected differently by heterogeneity. Further, the impact of heterogeneity on the effects of a policy also depends on the type of congestion considered. 相似文献
133.
Terry L. Friesz Taeil Kim Changhyun Kwon Matthew A. Rigdon 《Transportation Research Part B: Methodological》2011,45(1):176-207
In this paper we present a dual-time-scale formulation of dynamic user equilibrium (DUE) with demand evolution. Our formulation belongs to the problem class that Pang and Stewart (2008) refer to as differential variational inequalities. It combines the within-day time scale for which route and departure time choices fluctuate in continuous time with the day-to-day time scale for which demand evolves in discrete time steps. Our formulation is consistent with the often told story that drivers adjust their travel demands at the end of every day based on their congestion experience during one or more previous days. We show that analysis of the within-day assignment model is tremendously simplified by expressing dynamic user equilibrium as a differential variational inequality. We also show there is a class of day-to-day demand growth models that allow the dual-time-scale formulation to be decomposed by time-stepping to yield a sequence of continuous time, single-day, dynamic user equilibrium problems. To solve the single-day DUE problems arising during time-stepping, it is necessary to repeatedly solve a dynamic network loading problem. We observe that the network loading phase of DUE computation generally constitutes a differential algebraic equation (DAE) system, and we show that the DAE system for network loading based on the link delay model (LDM) of Friesz et al. (1993) may be approximated by a system of ordinary differential equations (ODEs). That system of ODEs, as we demonstrate, may be efficiently solved using traditional numerical methods for such problems. To compute an actual dynamic user equilibrium, we introduce a continuous time fixed-point algorithm and prove its convergence for effective path delay operators that allow a limited type of nonmonotone path delay. We show that our DUE algorithm is compatible with network loading based on the LDM and the cell transmission model (CTM) due to Daganzo (1995). We provide a numerical example based on the much studied Sioux Falls network. 相似文献
134.
This paper examines the location choice associated with discretionary activities (in-home vs. out-of-home). These substitution
patterns are important in terms of travel demand as in-home activities do not necessitate travel while out-of-home activities
incur travel. Mixed logit models are estimated using an activity dataset (2003 CHASE data) to analyze the factors associated
with this choice at the individual activity-level. Results suggest that the attributes of an activity significantly contribute
to understanding the likelihood of engaging in out-of-home activities. Activity type interaction terms reveal the varying
influence that socio-demographics, activity attributes and travel have over four different activity types modeled. The results
reveal that the location choice (in-home vs. out-of-home) is sensitive to travel characteristics. As the travel time and cost
increases, an individual is less likely to engage in an activity out-of-home. Compared to passive and social activities, the
location of active activities is more sensitive to changes in travel attributes. 相似文献
135.
136.
以上瑞高速公路怀新段第8合同段青山冲隧道为工程实例,针对左线出口端洞口浅埋偏压情况,为了节约工程投资,实施了反压回填的处治方案,采用数值模拟分析及现场监控量测数据分析了偏压隧道支护结构的受力状态和稳定性,可供类似工程参考. 相似文献
137.
Nguyen Khoi Tran 《Research in Transportation Economics》2011,32(1):39-53
The research aims to study the port selection in liner shipping. The central work is to set up a model to deal with port choice decisions. The model solves three matters: ports on a ship’s route; the order of selected ports and loading/unloading ports for each shipment. Its objective is to minimize total cost including ship cost, port tariff, inland transport cost and inventory cost. The model has been applied in real data, with cargo flows between the USA and Northern Europe. Afterwards, two sensitive analyses are considered. The first assesses the impact of a number of port calls on the total cost which relates closely to the viability of two service patterns: multi ports and hub & spoke. The second analyzes the efficiency of large vessels in the scope of a logistics network. The overriding result of this research is to indicate the influence of logistics factors in the decision of port choice. The research emphasizes the necessity to combine different factors when dealing with this topic, or else a result can be one-sided. 相似文献
138.
139.
140.
物联网被称为继计算机、互联网之后世界信息产业的第三次浪潮。[1]2009年温家宝总理基于物联网技术发展提出"感知中国"理念并将其上升为国家战略,美国总统奥巴马也把IBM基于物联网技术提出的"智慧地球"理念上升为国家战略。由此可见,当前许多国家都把发展新兴产业的突破口聚焦 相似文献