全文获取类型
收费全文 | 5775篇 |
免费 | 163篇 |
专业分类
公路运输 | 1332篇 |
综合类 | 1709篇 |
水路运输 | 1623篇 |
铁路运输 | 775篇 |
综合运输 | 499篇 |
出版年
2024年 | 9篇 |
2023年 | 18篇 |
2022年 | 84篇 |
2021年 | 124篇 |
2020年 | 97篇 |
2019年 | 48篇 |
2018年 | 383篇 |
2017年 | 352篇 |
2016年 | 305篇 |
2015年 | 136篇 |
2014年 | 150篇 |
2013年 | 231篇 |
2012年 | 320篇 |
2011年 | 516篇 |
2010年 | 537篇 |
2009年 | 381篇 |
2008年 | 462篇 |
2007年 | 482篇 |
2006年 | 343篇 |
2005年 | 304篇 |
2004年 | 133篇 |
2003年 | 139篇 |
2002年 | 77篇 |
2001年 | 84篇 |
2000年 | 60篇 |
1999年 | 25篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 21篇 |
1995年 | 9篇 |
1994年 | 7篇 |
1993年 | 9篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 13篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 3篇 |
1985年 | 1篇 |
1984年 | 4篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有5938条查询结果,搜索用时 78 毫秒
941.
Catherine Morency 《Transportation》2007,34(2):239-253
Ridesharing is quite a popular topic of discussion among transport authority personnel. It is perceived to be a viable alternative
to classical modes of transportation, and receives a great deal of political support from transport planners. However, not
much objective information is available on ridesharing behaviors. We use travel survey data to study the evolution of the
ridesharing market in an urban area. Our study is based on data from four large-scale OD surveys conducted in the Greater
Montreal Area (1987, 1993, 1998 and 2003).
In the latest survey conducted in Montreal, car passengers were asked to identify the driver who gave them the opportunity
to travel in this way. Their answers were classified according to the type of driver; for instance, a member of their household,
a neighbor or a co-worker. We use this information to calibrate a model matching car passengers and car drivers belonging
to the same household. This will be referred to as IHHR (intra-household ridesharing).
Preliminary results reveal that approximately 70% of all trips made by car passengers are the result of IHHR. Furthermore,
around 15% of those trips are questionable, in that they were exclusively generated for another individual’s purposes, consequently
generating an additional trip for the journey back home. Moreover, this percentage increased over time. Objective data regarding
ridesharing and its evolution in an urban area will undoubtedly help decision makers gain a clearer profile of this means
of travel and help to realign attitudes on the issue.
相似文献
Catherine MorencyEmail: |
942.
Becky P. Y. Loo 《Transportation》2007,34(4):471-486
Paratransit refers to urban transport services “somewhere between private passenger transport and conventional public transport in terms of cost and quality of service” [Rimmer (1980), Paratransit: A commentary. Environ. Plan. A 12, 937–944]. Since the 1980s, a new form of paratransit—residents’ coach, which provides exclusive transport services to residents living in private housing estates—has emerged in Hong Kong. What was the background underlying the emergence and subsequent growth of residents’ coach services? Also, what was the role of residents’ coach in the public transport system of Hong Kong? With the completion of more railway extensions, should residents’ coach services be replaced? If so, what are the potential impacts on people’s life? This paper addresses the above research questions through a large-scale questionnaire survey that examined not only people’s modal choice but also their residential choice, socio-economic background and attitudes. The findings suggest that transport policy makers should pay more attention to examine new forms of paratransit and the ways of integrating them into the overall public transport system, both spatially and temporally. It is only through the development of an efficient and multi-modal transport system can the maximum potential of paratransit in filling the transport gap between conventional mass transit and private cars be realized. 相似文献
943.
为了使列车运行仿真计算结果与实测的列车运行数据更接近,确保仿真系统能够切实有效地分析研究铁路运输生产实际,通过对比研究牵引计算方法计算结果与列车运行监控记录装置实测的数据之间的差异,识别出误差产生的主要原因,并分析了计算误差与坡道类型及列车编组之间的影响关系. 通过理论计算与实验测试,提出了基于测试结果对列车坡道阻力计算模型进行修正的方法与模型. 对修正计算模型和原始模型的计算结果与实测数据进行对比分析,结果表明,修正后的计算模型与实测数据更加吻合,平均计算误差从14%降低到5%. 目前,该模型已成功应用到内燃牵引货运列车节能优化操纵指导系统,取得了良好的实用效果. 相似文献
944.
We developed a new structural lightweight concrete by totally or partially replacing coarse and fine aggregates in high performance concrete by expanded polystyrene (EPS) beads. In this work,the sizes of EPS bead were 1.0,2.5 and 6.3 mm. Lightweight EPS concretes with a wide range of concrete densities and compressive strengths were successfully developed. Compressive strength,splitting tensile strength,shrinkage,and water absorption were examined. Additionally,fine silica fume (SF) and polypropylene (PP) f... 相似文献
945.
Mesh motion strategy is one of the key points in many fluid-structure interaction problems. One popular technique used to solve this problem is known as the spring analogy method. In this paper a new mesh update approach based on the spring analogy method is presented for the effective treatment of mesh moving boundary problems. The proposed mesh update technique is developed to avoid the generation of squashed invalid elements and maintain mesh quality by considering each element shape and grid scale to th... 相似文献
946.
冯正平 《上海交通大学学报(英文版)》2010,15(2):194-198
The design approach of H∞ autopilot for autonomous underwater vehicles (AUVs) is proposed. Comprised by the three sub-controllers,i.e. speed,heading and depth controllers,the designed autopilot has advantage over existing H∞ control of AUVs. The overshoot in speed,heading and depth control systems under step commands is restricted by refining the weighting function for robust stability. The dynamic performance of heading and depth control systems is improved by feeding back yaw rate and pitch angle,respecti... 相似文献
947.
Method for workspace calculation of 6R serial manipulator based on surface enveloping and overlaying
Aiming at the workspace calculation problem of multi-joint serial manipulators, a surface enveloping and overlaying (SEO)
method is presented to identify and visualize the manipulator workspace. The SEO method is composed of two stages: the first
stage is to choose reference points of the manipulator and calculate their boundary surfaces using the nth enveloping method; the second stage is to overlay these boundary surfaces to identify the final workspace. The SEO method
is basically a combination of the analytic method and the numerical method. By delineating the graphic representation of the
workspace step by step, the SEO method is easy to analyze the existence and the shape of voids and holes. The basic theory
of the SEO method and formulas for workspace calculation are presented based on a 6R serial manipulator. By showing the workspace
calculation results, the SEO method is proved working correctly. 相似文献
948.
To quantify mechanical effects of plantar fascia and ligaments on the arch structure, a 3D finite element model of the foot
was created to simulate the balanced standing posture. Four cases after individual releases of plantar fascia, spring ligament,
long and short plantar ligaments were simulated respectively to compare their consequences to the predictions of the intact
structure. It was founded that the foot arch didn’t collapse obviously after any individual release of these structures. As
plantar fascia was released, tensions of plantar ligaments were largely increased. Long and short plantar ligaments performed
mutual compensation functions. 相似文献
949.
A fuzzy optimization model of storage space allocation is proposed, and a rolling-planning method is derived. The model takes
the uncertainty of departure time of import containers and arrival time of export containers into account. For each planning
horizon, the problem is decomposed into two levels: the first level minimizes the unbalanced workloads among blocks using
hybrid intelligence algorithm; based on block workloads allocated in the above level, the second level minimizes the number
of blocks to which the same group of import containers are split. Numerical results show that the model reduces workload imbalance,
and speeds up the vessel loading and discharging process. 相似文献
950.
Initial conditions of impact dynamics 总被引:1,自引:0,他引:1
The effects of the initial conditions of impact dynamics equations are investigated numerically and experimentally. The inadequacies
of previous studies on initial conditions are pointed out. Then a coefficient of velocity jump at the moment of impact is
introduced, and the experiments for the mental rods are implemented to validate the appending constraints modeling methods
for impact process. The comparisons between the experimental and simulated results at different coefficients are used to study
the effects of the velocity jump conditions to the numerical simulation. The results indicate that the physical velocity response
of bodies during impact is smooth; the different values of velocity jump only have small effects on numerical oscillation
of velocity response, and they have no effects on the time history of impact force. 相似文献