全文获取类型
收费全文 | 2529篇 |
免费 | 136篇 |
专业分类
公路运输 | 541篇 |
综合类 | 1034篇 |
水路运输 | 392篇 |
铁路运输 | 308篇 |
综合运输 | 390篇 |
出版年
2024年 | 6篇 |
2023年 | 14篇 |
2022年 | 33篇 |
2021年 | 49篇 |
2020年 | 73篇 |
2019年 | 61篇 |
2018年 | 88篇 |
2017年 | 86篇 |
2016年 | 137篇 |
2015年 | 134篇 |
2014年 | 219篇 |
2013年 | 165篇 |
2012年 | 191篇 |
2011年 | 206篇 |
2010年 | 139篇 |
2009年 | 165篇 |
2008年 | 143篇 |
2007年 | 186篇 |
2006年 | 165篇 |
2005年 | 104篇 |
2004年 | 56篇 |
2003年 | 39篇 |
2002年 | 31篇 |
2001年 | 59篇 |
2000年 | 17篇 |
1999年 | 23篇 |
1998年 | 8篇 |
1997年 | 16篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 13篇 |
1993年 | 6篇 |
1992年 | 5篇 |
1991年 | 3篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1986年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有2665条查询结果,搜索用时 93 毫秒
731.
A bayesian dynamic linear model approach for real-time short-term freeway travel time prediction 总被引:1,自引:0,他引:1
Xiang Fei Chung-Cheng Lu Ke Liu 《Transportation Research Part C: Emerging Technologies》2011,19(6):1306-1318
This paper presents a Bayesian inference-based dynamic linear model (DLM) to predict online short-term travel time on a freeway stretch. The proposed method considers the predicted freeway travel time as the sum of the median of historical travel times, time-varying random variations in travel time, and a model evolution error, where the median is employed to recognize the primary travel time pattern while the variation captures unexpected supply (i.e. capacity) reduction and demand fluctuations. Bayesian forecasting is a learning process that revises sequentially the state of a priori knowledge of travel time based on newly available information. The prediction result is a posterior travel time distribution that can be employed to generate a single-value (typically but not necessarily the mean) travel time as well as a confidence interval representing the uncertainty of travel time prediction. To better track travel time fluctuations during non-recurrent congestion due to unforeseen events (e.g., incidents, accidents, or bad weather), the DLM is integrated into an adaptive control framework that can automatically learn and adjust the system evolution noise level. The experiment results based on the real loop detector data of an I-66 segment in Northern Virginia suggest that the proposed method is able to provide accurate and reliable travel time prediction under both recurrent and non-recurrent traffic conditions. 相似文献
732.
Bin Yu William H.K. Lam Mei Lam Tam 《Transportation Research Part C: Emerging Technologies》2011,19(6):1157-1170
Provision of accurate bus arrival information is vital to passengers for reducing their anxieties and waiting times at bus stop. This paper proposes models to predict bus arrival times at the same bus stop but with different routes. In the proposed models, bus running times of multiple routes are used for predicting the bus arrival time of each of these bus routes. Several methods, which include support vector machine (SVM), artificial neural network (ANN), k nearest neighbours algorithm (k-NN) and linear regression (LR), are adopted for the bus arrival time prediction. Observation surveys are conducted to collect bus running and arrival time data for validation of the proposed models. The results show that the proposed models are more accurate than the models based on the bus running times of single route. Moreover, it is found that the SVM model performs the best among the four proposed models for predicting the bus arrival times at bus stop with multiple routes. 相似文献
733.
734.
为研究桥梁在移动车辆荷载作用下的动力特性和承载能力,以某连续梁桥为计算实例,采用大型通用有限元软件ANSYS建立了质量-弹簧的车辆模型和桥梁结构的有限元模型,用时程分析法分析了车辆荷载作用下连续梁桥的动力响应特征,着重探讨了车辆刚度、车辆质量、行车速度等车辆荷载因素对连续梁桥动力响应的影响规律,并提出相应结论。 相似文献
735.
分析了潜艇打击远程目标过程各阶段的时间延迟,采用误差合成的方法建立了反舰导弹捕捉概率简化模型,并据以进行了量化分析,提出了相应建议。 相似文献
736.
通过使用空空导弹雷达导引头箔条干扰仿真软件,采用目标飞机运动模型、箔条干扰特性、导弹运动模型,对箔条诱骗空空导弹雷达导引头的全过程进行作战仿真,分析出箔条干扰弹投放最佳时机。 相似文献
737.
分析了公交站点间车辆运行过程,将行程预测时间划分为交叉口排队等待时间、路段行驶时间和停站时间3个部分,利用交通波理论和延误三角形,分别建立了无公交专用车道和有公交专用车道2种情况下排队等待时间的动态预测模型;根据乘客到站规律和上下车规律,提出了公交车进站停靠时间模型;针对无公交专用车道条件下的时间预测方法进行了实例演算.实验数据表明,基于交通波行程时间预测方法具有较高的精度,可以满足站点间行程时间预报要求. 相似文献
738.
针对车辆保有量日益增加和拥堵情况日趋严重而造成的城市冷链物流时效性不强、客户价值不高、顾客满意度降低等问题,综合考虑客户价值、客户满意度以及成本等因素,提出一种城市冷链物流时变路径优化方法。考虑到冷链配送过程中不同时段的道路拥堵问题,采用分段函数刻画车辆行驶速度,并同时考虑时间窗和车辆载重量等约束,建立了多目标数学模型。使用线性加权法和主要目标法对多目标进行处理,将其转换成单目标数学模型。结合问题NP难特性,设计了单亲遗传算法对小、中、大规模算例进行了求解,结果表明:与未考虑客户价值模型相比,该模型在平均增加3.28%成本的情况下,提高14.96%的客户价值和14.64%的满意度;与未考虑成本模型相比,该模型在减少1.55%的客户价值的前提下,节约17.32%的成本;对比静态路网模型,模型减少0.92%的成本,提高6.27%的客户满意度和16.06%的客户价值。通过对目标函数中成本权重和客户价值权重进行参数分析,表明成本和客户价值之间存在明显的背反关系。 相似文献
739.
Day-to-day variation in the travel times of congested urban transportation networks is a frustrating phenomenon to the users of these networks. These users look pessimistically at the path travel times, and learn to spend additional time to safeguard against serious penalties that await late arrivals at the destinations. These additional expenses are charges similar to the tolls in system equilibrium flow problem, but may not be collected. With this conjecture, the user equilibrium (UE) formulation of congested network flow problem would lack some necessary factors in addressing appropriate path choices. This study, following a previous work proposing pessimistic UE (PUE) flow, aims to show how to measure this additional travel cost for a link, and investigates how different is PUE from UE, and when such differences are pronounced. Data are collected from the peak-hour travel times for the links of paths in the city of Tehran, to estimate the variance of travel times for typical links. Deterministic functions are obtained by calibrating the standard deviation of the daily variations of link travel times, and probabilistic functions by the technique of copula. UE and PUE traffic assignment models are built and applied to three large cities of Mashhad, Shiraz, and Tehran in Iran. The results show that the estimated flows by PUE model replicate the observed flows in screen lines much better than the UE model, particularly for longer trips. Since PUE is computationally equivalent to UE, this improvement is attained virtually at no cost. 相似文献
740.
为研究振动法成型水泥稳定碎石试件取代静压法的可行性,通过无侧限抗压强度试验测试了振动法成型试件的力学性能,分析讨论了相关影响因素,并通过与静压法及实际工程钻芯取样进行对比,分析了水泥稳定碎石振动成型的优势。结果发现,在提高水泥剂量的基础上,较长的振动时间能够提升水泥稳定碎石的抗压强度;同样的养生时间下,较长振动时间下形成的水泥稳定碎石的抗压强度较大;静压成型试件的抗压强度显著低于实际工程,而振动法成型试件的强度与实际工程较为接近。 相似文献