全文获取类型
收费全文 | 22244篇 |
免费 | 313篇 |
专业分类
公路运输 | 5699篇 |
综合类 | 4195篇 |
水路运输 | 6129篇 |
铁路运输 | 3766篇 |
综合运输 | 2768篇 |
出版年
2023年 | 69篇 |
2022年 | 315篇 |
2021年 | 463篇 |
2020年 | 374篇 |
2019年 | 182篇 |
2018年 | 285篇 |
2017年 | 246篇 |
2016年 | 329篇 |
2015年 | 434篇 |
2014年 | 835篇 |
2013年 | 1976篇 |
2012年 | 1192篇 |
2011年 | 1468篇 |
2010年 | 1312篇 |
2009年 | 1584篇 |
2008年 | 1457篇 |
2007年 | 1824篇 |
2006年 | 1624篇 |
2005年 | 1180篇 |
2004年 | 552篇 |
2003年 | 431篇 |
2002年 | 360篇 |
2001年 | 420篇 |
2000年 | 394篇 |
1999年 | 244篇 |
1998年 | 265篇 |
1997年 | 222篇 |
1996年 | 231篇 |
1995年 | 218篇 |
1994年 | 161篇 |
1993年 | 242篇 |
1992年 | 193篇 |
1991年 | 114篇 |
1990年 | 115篇 |
1989年 | 86篇 |
1988年 | 87篇 |
1987年 | 77篇 |
1986年 | 72篇 |
1985年 | 80篇 |
1984年 | 79篇 |
1983年 | 73篇 |
1982年 | 73篇 |
1981年 | 95篇 |
1980年 | 68篇 |
1979年 | 91篇 |
1978年 | 56篇 |
1977年 | 69篇 |
1976年 | 53篇 |
1975年 | 65篇 |
1974年 | 50篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
ABSTRACTThe need for improved public transport (PT) ticketing in ever-growing deregulated PT markets has made well-designed integrated ticketing systems a priority area of intervention for PT service providers around the world. Yet, very little practical evidence of its impacts are reported in Sweden and in the world at large. The focus of this study was the impacts of the Movingo integrated ticketing scheme in terms of PT patronage, user satisfaction and the perceived quality of the ticketing set-up. Three travel surveys were conducted along the Stockholm-Uppsala route. Methods including logistic regression and correlated t-tests were used to analyse the samples. The findings suggest that the scheme made rail commuting more attractive resulting in an overall increase of about 24% in ticket sales with 3% – 15% car commuters reporting that they patronised PT services after the project. The scheme also resulted in increased rail commuter satisfaction. The overall perceived quality of the ticketing set-up did not however improve due to interoperability challenges. Service providers’ uncertainty about equitable distribution of revenue among the participating service providers, interoperability challenges and the lack of interest among most of the participating service providers to sell Movingo tickets are some issues to be addressed. 相似文献
2.
ABSTRACTThe economic history of the U.S. illustrates how the role of many cities has been changed by being seaports or located on navigable rivers or lakes. Based on the widening of the Panama Canal in 2016, the West Coast ports that include the west coast seaports of California, Oregon, and Washington were expected to become less important, while the freight shares of the East Coast and Gulf ports would increase. By how much it has been not easy to measure or predict so far, but this study attempted to define some of the key parameters in the measurement. As well as several relevant background topics, both the demand- and supply-side versions of the National Interstate Economic Model, have been applied for the measurement of economic impacts. U.S. port authorities and policy makers at the local and national levels who respond and develop plans for coping with the new realities of the Panama Canal are able to understand the extent to which changes in shippers’ and land-mode transporters’ behaviors would undermine the logistics and the costs of their activities. Therefore, this study is important for a diverse spectrum of port development strategies in the U.S. to respond to the Canal expansion. 相似文献
3.
The time-series of remote-sensed surface chlorophyll concentration measured by SeaWiFS radiometer from September 1997 to December 2001 and the relevant hydrological and meteorological factors (remote-sensed sea surface temperature, atmospheric precipitation, air temperature and wind stress) in Santa Monica Bay and adjacent waters off southern California were analyzed using wavelet and cross-correlation statistical methods. All parameters exhibited evident seasonal patterns of variation. Wavelet analysis revealed salient long-term variations most evident in air temperature during El Niño 1997–1998 and in wind stress during La Niña 1998–1999. Short-period (<100 days) variations of remote-sensed chlorophyll biomass were mostly typical to spring seasons. Chlorophyll biomass was significantly correlated with air temperature and wind stress: an increase of chlorophyll biomass followed with 5–6-day time lag an increase of wind stress accompanied by a simultaneous decrease of air temperature. The mechanism of these variations was an intensification of phytoplankton growth resulting from the mixing of water column by wind stress and entrainment of nutrients into the euphotic layer. 相似文献
4.
1 数字化集装箱码头(e-CTerminal)的提出近年来,随着我国经济形势的好转和加入WTO,港口企业生产经营环境发生很大变化,面临的市场形势是机遇与挑战并存。机遇是指:(1)国民经济形势持续好转,带来了进出口货量的增加,港口吞吐量增大,效益转好; 相似文献
5.
结合某桥梁施工数据,以AutoCAD为图形平台,开发出一套具有初步GIS分析查询功能的桥梁工程施工信息系统(Engineering Geographic Information System,EGIS),并就其系统功能、技术路线、关键技术进行了详细阐述。 相似文献
6.
7.
Although counteracting environmental programmes and policies have been strengthened, large oil spills still occur at irregular intervals. The total oil spill costs and their compensations have attracted much interest from various parties, such as local stakeholders, and state and federal governments. This paper addresses five major cost categories whose aggregations are expected to cover the overall direct and indirect costs after the release of an oil spill. Among them, research costs should not be neglected, since they tend to be high if public attention has been drawn to the case. Through an examination of the relationship between the total oil spill costs and their admissible claims, we found that:
- admissible claims do not cover the overall costs of the oil spill, and
- admissible claims cannot be compensated in full in the case of large spills.
8.
结合铁路远动系统已建区段运行实际及积累的经验,探讨监控系统安全性、保护装置信息采集、远动信息分流、规约转换等铁路信号电源监控装置远动系统设计、建设和运行中需注意的几个问题。并结合存在的问题提出了具体的分析及建议。 相似文献
9.
城市轨道交通项目投资额巨大、建设周期长、政府财政负担重等问题是每个发展轨道交通的城市都要面临的难题。如何改善城市轨道交通投融资环境.减少该领域潜在的风险,已经成为相关政府和企业深思的课题。作者将以北京地铁4号线特许经营为例.浅析城市轨道交通特许经营的有关法律法规并就其完善提出几点建议。 相似文献
10.
1前言
津浦上行线K960+000至K860+000综合大修施工堪称上海铁路局历史上前所未有的浩大工程,全局原四个大修段首次联合施工,共有30台大型养路机械参与作业,要在一个封锁点内同时完成换枕、清筛、换轨的工作,保证在50天内完成.因此,每天的施工进度必须要完成2 km以上,难度相当大.为了确保联合施工的安全可靠、质量达标,各兄弟单位之间加强沟通,通力协作,圆满地完成了大会战施工各项既定的任务. 相似文献