全文获取类型
收费全文 | 1438篇 |
免费 | 101篇 |
专业分类
公路运输 | 243篇 |
综合类 | 670篇 |
水路运输 | 230篇 |
铁路运输 | 264篇 |
综合运输 | 132篇 |
出版年
2024年 | 5篇 |
2023年 | 7篇 |
2022年 | 25篇 |
2021年 | 52篇 |
2020年 | 41篇 |
2019年 | 35篇 |
2018年 | 29篇 |
2017年 | 37篇 |
2016年 | 67篇 |
2015年 | 53篇 |
2014年 | 125篇 |
2013年 | 110篇 |
2012年 | 130篇 |
2011年 | 129篇 |
2010年 | 96篇 |
2009年 | 86篇 |
2008年 | 94篇 |
2007年 | 135篇 |
2006年 | 99篇 |
2005年 | 51篇 |
2004年 | 45篇 |
2003年 | 29篇 |
2002年 | 16篇 |
2001年 | 17篇 |
2000年 | 7篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1989年 | 2篇 |
排序方式: 共有1539条查询结果,搜索用时 625 毫秒
631.
为综合分析社会偏好理论视野下的服务链定价策略博弈问题,本文构建了服务提供商和出行即服务(Mobility as a Service, MaaS)平台组成的旅游出行服务链联盟。基于社会偏好理论建立不平等厌恶决策模式、利他决策模式和社会福利综合决策模式下的Stackelberg博弈模型,与分散决策和合作决策两种服务链基本决策模式下的博弈结果进行比较。探究MaaS环境下考虑决策者社会偏好特征的旅游出行服务产品的定价策略及服务链收益,并通过数值分析验证了模型的有效性。结果表明,决策权的分散导致旅游出行服务产品的销售价格和服务链整体最优收益降低。不平等厌恶决策模式下,产品的最优销售价格不受影响,服务链整体利润不变;利他决策模式下,服务链整体最优收益不断上升;社会福利综合决策模式下,各最优决策变量受服务提供商利他偏好的影响更大。关注服务链决策者的不平等厌恶偏好并实施利他行为,可以提高旅游出行服务产品的需求和总体收益,有利于旅游出行服务链的协调运营状态,实现交旅融合发展。 相似文献
632.
633.
634.
Vehicular networks represent a research area of significant importance in improving the safety, efficiency and sustainability of transportation systems. One of the key research problems in vehicular networks is real-time data dissemination, which is crucial to the satisfactory performance of many emergent applications providing real-time information services in vehicular networks. Specifically, the two issues need to be addressed in this problem are maintenance of temporal data freshness and timely dissemination of data. Most existing works only considered periodical data update via backbone wired networks in maintaining temporal data freshness. However, many applications rely on passing vehicles to upload their collected information via wireless network, which imposes new challenges as the uplink data update will have to compete with the downlink data dissemination for the limited wireless bandwidth. With such observations, we propose a temporal information service system, in which vehicles are able to collect up-to-date temporal information and upload them to the roadside units (RSU) along their trajectories. Meanwhile, RSU can disseminate its available data items to vehicles based on their specific requests. Particularly, in this paper, we first quantitatively analyze the freshness of temporal data and propose a mathematical model to evaluate the usefulness of the temporal data. Next, we give the formulation of the proposed real-time and temporal information service (RTIS) problem, and prove the NP-hardness of this problem by constructing a polynomial-time reduction from 0–1 knapsack problem. Subsequently, we establish a probabilistic model to theoretically analyze the tradeoff between timely temporal data update and requested data dissemination sharing a common communication resource, which provides a deeper insight of the proposed RTIS. Further, a heuristic algorithm, namely adaptive update request scheduling (AURS), is designed to enhance the efficacy of RTIS by synthesizing the broadcast effect, the real-time service requirement and the service quality in making scheduling decisions. The computational complexity and scalability analysis of AURS is also discussed. Last but not least, a simulation model is implemented and a comprehensive performance evaluation has been carried out to demonstrate the superiority of ARUS against several state-of-the-art approaches in a variety of application scenarios. 相似文献
635.
The purpose of this paper is to explore themes and challenges in developing environmentally sustainable logistical activities.The approach is explorative with a cross sectional design that takes advantage of ten case studies out of selected logistics service providers (LSPs) operating primarily in the Scandinavian countries.The findings illustrate the major themes by analyzing current and future activities in developing environmentally sustainable logistical activities. In addition, four categories of challenges are identified: customer priorities, managerial complexity, network imbalance, and technological and legislative uncertainties. It is concluded that there is a great need for a holistic perspective where LSPs and product owners together analyze and design future logistical setups.The suggested holistic and integrative model, building on a three-dimensional concurrent engineering framework, provides new opportunities for research. Further research is needed to improve the interrelationship between LSPs and their customers in the development of sustainable logistical solutions.This paper puts forward recommendations for the sustainable development of logistics by combining the results from the case studies with a review of related literature. This will be beneficial for managers and policy makers when they approach sustainable logistical challenges. The emergence and synthesis of themes and challenges are critical for a sustainable society. 相似文献
636.
双车道公路路段通行能力分析与推算方法 总被引:1,自引:0,他引:1
以河北省各种类型双车道二级公路为背景,根据大量现场观测数据,在分析与研究汽车二级专用和一般混合交通二级公路交通流特性的基础上,提出了采用间隙理论计算通行能力的不适应性,代之以实现观测数据的拟合分析来确定其通行能力的计算方法。还根据数值集合场原理,提出了速度自由度的概念,并由此确定与划分道路服务水平,继之提出了计算服务通行能力的数学模型和相应的技术指标。 相似文献
637.
陈仕杰 《现代城市轨道交通》2013,(3):38-40,48
介绍软交换的概念及技术特点,对软交换系统和传统的电路交换系统在业务提供和网络构成方面进行比较,并对城市轨道交通公务电话系统采用软交换技术组网时的网络结构进行探讨。 相似文献
638.
鍛冶智也 《城市轨道交通研究》2016,(11):6-10
东京圈的铁路网由一种缺少竞争的地域分业体制组成。连接开发空间较大的郊区与市中心的近距离铁路,主要是由私营铁路公司来建设的。因此,私营铁路公司在建设铁路的同时,还通过推进地域的开发和促进人口增长的策略来提高人们乘坐铁路列车的机会,并且实行公共交通指向型开发来扩充铁路运输事业。 相似文献
639.
对员工的岗位工作考绩是各单位人力资源管理中的一项重要工作内容,已引起各级领导的重视,岗位考绩办法也有了一定的改进。但由于工作难度大、改革进展不快,目前仍存在着考绩目的单一化、考绩内容扩大化、评判标准模糊化等问题。针对目前员工岗位考绩中存在的问题,提出了改进思路,认为对员工的岗位工作考绩主要是考核其岗位工作情况,不是评价其人格特质,提出对员工的岗位工作考绩应做到考绩内容具体化、考绩项目细化、考绩评分标准量化的办法。 相似文献
640.