首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   7756篇
  免费   451篇
公路运输   1345篇
综合类   2574篇
水路运输   1709篇
铁路运输   2136篇
综合运输   443篇
  2024年   30篇
  2023年   66篇
  2022年   163篇
  2021年   262篇
  2020年   295篇
  2019年   185篇
  2018年   141篇
  2017年   204篇
  2016年   224篇
  2015年   351篇
  2014年   532篇
  2013年   447篇
  2012年   656篇
  2011年   671篇
  2010年   493篇
  2009年   480篇
  2008年   467篇
  2007年   645篇
  2006年   651篇
  2005年   379篇
  2004年   268篇
  2003年   185篇
  2002年   107篇
  2001年   99篇
  2000年   47篇
  1999年   31篇
  1998年   32篇
  1997年   18篇
  1996年   15篇
  1995年   12篇
  1994年   12篇
  1993年   9篇
  1992年   8篇
  1991年   7篇
  1990年   6篇
  1989年   4篇
  1988年   1篇
  1987年   2篇
  1985年   1篇
  1984年   1篇
排序方式: 共有8207条查询结果,搜索用时 31 毫秒
211.
212.
阐述了基于云平台的城市轨道交通能源管理系统架构和建设方式。该系统利用云计算的高效和弹性来部署建设,采用线网-车站二层管理模式,降低了线网和线路服务器等的硬件部署成本和维护成本。通过将能源管理系统内部使用的业务应用转换为基于云平台的能源管理应用软件,能源管理系统可获取云平台提供的共享数据,并将经过业务处理后的数据存储到云平台中,以服务于云平台上其他业务,实现了数据资源的逻辑统一和高效利用。  相似文献   
213.
The degree of centralization of the logistics network is one of the important strategic decisions to take. This issue has often been studied but mainly from a cost minimization focus. This research studies the influence of incorporating the environmental impact in logistics network design models, comparing the results with those obtained considering cost minimization only. A fuzzy biobjective optimization model is used to carry out a number of experiments. By weighting the relative importance of the two objectives, the differences with respect to the base cost minimization solution can be ascertained. Our results show that in general more material is moved through warehouses when the environmental impact is considered and more decentralized facilities are opened.  相似文献   
214.
Lane-based road information plays a critical role in transportation systems, a lane-based intersection map is the most important component in a detailed road map of the transportation infrastructure. Researchers have developed various algorithms to detect the spatial layout of intersections based on sensor data such as high-definition images/videos, laser point cloud data, and GPS traces, which can recognize intersections and road segments; however, most approaches do not automatically generate Lane-based Intersection Maps (LIMs). The objective of our study is to generate LIMs automatically from crowdsourced big trace data using a multi-hierarchy feature extraction strategy. The LIM automatic generation method proposed in this paper consists of the initial recognition of road intersections, intersection layout detection, and lane-based intersection map-generation. The initial recognition process identifies intersection and non-intersection areas using spatial clustering algorithms based on the similarity of angle and distance. The intersection layout is composed of exit and entry points, obtained by combining trajectory integration algorithms and turn rules at road intersections. The LIM generation step is finally derived from the intersection layout detection results and lane-based road information, based on geometric matching algorithms. The effectiveness of our proposed LIM generation method is demonstrated using crowdsourced vehicle traces. Additional comparisons and analysis are also conducted to confirm recognition results. Experiments show that the proposed method saves time and facilitates LIM refinement from crowdsourced traces more efficiently than methods based on other types of sensor data.  相似文献   
215.
为研究信号交叉口非机动车违规过街行为,选取西安市的7个信号交叉口,通过视频拍摄获取资料,应用复杂网络来分析非机动车网络的结构特征和演化规律.建立了交叉口非机动车网络,基于SI模型的基本思想,提出了非机动车违规过街行为的传播模型.并通过python程序进行模拟分析,在不同的网络结构和不同的传播率下,获取了非机动车违规过街的行为趋势.结果表明:随着等待时间的增加,一旦有骑行者闯红灯,更多的骑行者将加入到违规过街的行列;在内向度和外向度方面,电动自行车均高于普通自行车;非机动车违规行为随着传播率及非机动车流量的增加而增加.  相似文献   
216.
铁路货物运输组织是铁路工作的一个核心内容,铁路货物追踪系统的设计与实现能够为货主提供更好、更快的服务,同时加快和保障铁路货运工作的组织。通过对铁路整车货物运输的流程分析,制定货物追踪系统的目标,分析系统功能。通过数据的采集和信息共享平台的建立,提出货物追踪系统的实现途径。  相似文献   
217.
文章针对广西交通科技项目管理系统现状,分析了建设交通科技资源共享平台的必要性,阐述了交通科技资源共享平台建设的关键技术、创新点及主要内容,指出该共享平台的建设可改善和提高交通运输科技项目质量及监管水平。  相似文献   
218.
高职院校公共《计算机基础》课程实践教学研究   总被引:1,自引:0,他引:1  
对高职院校公共《计算机基础》实践教学效果及其存在的问题进行剖析,针对这些问题所采取的应对措施进行了探索和研究。提出加强实践教学改革的方案和具体方法,使高职院校的计算机基础教育能更好地与市场接轨。  相似文献   
219.
Most of existing route guidance strategies achieves user optimal equilibrium by comparing travel time. Measuring travel time, however, might be uneasy on an urban road network. To contend with the issue, the paper mainly considers easily obtained inflow and outflow of a link and road capacity as input, and proposes a route guidance strategy for a single destination road network based on the determination of free-flow or congested conditions on alternative routes. An extended strategy for a complex network and a feedback approximation for avoiding forecast are further explored. Weaknesses of the strategy are also explicitly analyzed. To test the strategy, simulation investigations are conducted on two networks with multiple parallel routes. The results indicate that the strategy is able to provide stable splitting rates and to approximate user optimal equilibrium in different conditions, in particular when traffic demand is high. This strategy has potential to be applied in an urban road network due to its simplicity and easily obtained input data. The strategy is also applicable for single destination if some alternatives and similar routes are available.  相似文献   
220.
On dynamic coastal sites, subject to rapid and sometimes unpredictable shoreline changes, management problems can be aggravated if legally authoritative maps are obsolete. These difficulties are illustrated by two case studies from County Donegal in northwest Ireland. The first case study outlines the problems that arise where statutory functional area boundaries are based on a near century-old map. The second case study deals with the problems of planning development on a site where a customized map only a few years old has been rendered obsolete by rapid coastal erosion. Other problems are caused by the inappropriate use of maps. Suggestions are made to mitigate the effects of outdated maps.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号