全文获取类型
收费全文 | 14180篇 |
免费 | 880篇 |
专业分类
公路运输 | 4563篇 |
综合类 | 4049篇 |
水路运输 | 3127篇 |
铁路运输 | 2504篇 |
综合运输 | 817篇 |
出版年
2024年 | 63篇 |
2023年 | 126篇 |
2022年 | 285篇 |
2021年 | 489篇 |
2020年 | 584篇 |
2019年 | 314篇 |
2018年 | 240篇 |
2017年 | 320篇 |
2016年 | 382篇 |
2015年 | 541篇 |
2014年 | 1159篇 |
2013年 | 821篇 |
2012年 | 1340篇 |
2011年 | 1368篇 |
2010年 | 1026篇 |
2009年 | 880篇 |
2008年 | 890篇 |
2007年 | 1172篇 |
2006年 | 977篇 |
2005年 | 603篇 |
2004年 | 389篇 |
2003年 | 266篇 |
2002年 | 164篇 |
2001年 | 142篇 |
2000年 | 90篇 |
1999年 | 55篇 |
1998年 | 42篇 |
1997年 | 49篇 |
1996年 | 46篇 |
1995年 | 35篇 |
1994年 | 38篇 |
1993年 | 28篇 |
1992年 | 24篇 |
1991年 | 25篇 |
1990年 | 28篇 |
1989年 | 15篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 6篇 |
1985年 | 10篇 |
1984年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
论述了非冲积性滩险类型、基本成因、滩险碍航特点、水流特性及其分析方法。通过滩性分析可以确定滩险成滩水位、最凶水位、消滩水位(流量)的成滩出现时期及滩段凶、险的定量概念。结合滩段地貌、地形特点,确定碍航水流具体成因,并据以制定整治原则和方法。 相似文献
912.
针对在实际生产过程中出现的垃圾转运车后门不能举升和下降的故障现象,通过对液压系统原理图的分析和借助适当的检测工具,按照由简单到复杂的原则,逐一排查可能引起故障的原因,使故障得以快速解决,并提供了一种对故障原因进行分析的思路。 相似文献
913.
《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2012,50(1):123-143
ABSTRACTDynamic wheel–rail interaction in railway turnouts is more complicated than on ordinary track. In order to evaluate the derailment behaviour of railway wheelsets in railway turnouts, this paper presents a study of dynamic wheel–rail interaction during a wheel flange climbs on the turnout rails, by applying the elasticity positioning wheelset model. A numerical model is established based on a coupled finite element method and multi-body dynamics, and applied to study the derailment behaviour of a railway wheelset in both the facing and trailing directions in a railway turnout, as well as dynamic wheel–turnout rail interaction during the wheel flange climbing on the turnout rails. The influence of the wheel–rail attack angle and the friction coefficient on the dynamic derailment behaviour is investigated through the proposed model. The results show that the derailment safety for a wheelset passing the railway turnout in facing direction is significantly lower than that for the trailing direction and the ordinary track. The possibility of derailment for the wheelset passing the railway turnout in facing and trailing directions at positive wheel–rail attack angles will increase with an increase in the attack angles, and the possibility of derailment can be reduced by decreasing the friction coefficient. 相似文献
914.
胡俊辉 《铁路工程造价管理》2008,23(3):18-20
目前在时速160km客货共线铁路设计中,通桥(2005)“2101”钢筋混凝土简支T梁逐步得到应用。此文通过对铁路架桥机架设“2101”梁的经济分析,认为如果解决了“2101”梁的架设费用这个较大的问题,它将会有广阔的应用前景。 相似文献
915.
916.
茂名港沙坝泻湖海岸泥沙运动特征分析 总被引:1,自引:0,他引:1
文章根据博贺湾的地形地貌、潮流、风浪、泥沙运动等资料,分析了沿海沙坝泻湖海岸泥沙运动特征,探讨沿海沙坝泻湖地区建设深水大港的可行性。 相似文献
917.
Lam Canh Nguyen 《Maritime Policy and Management》2019,46(1):24-42
This paper aims at defining generic characteristics of dry ports by carrying out an analysis using a large sample of dry ports from around the world. The dataset includes details on 107 inland terminals worldwide. All dry ports in the database have been selected from studies in the extant literature before being shortlisted to fit our research scope. Data collected include terminologies used, actors driving the development, terminal throughput, total area, services provided and the relation with the corresponding seaport(s). Using statistical analysis, the paper examines how dry port parameters are influenced by (1) a different terminal set up, like sea-driven and land-driven development, developed and developing system, dry port functions; (2) specifications of the seaport with which the dry port is connected, i.e. seaport traffic, connectivity, utilization, etc. and (3) the transport leg linking dry ports and seaports. The findings could be applied to the planning and development of inland nodes from the perspectives of different stakeholders. 相似文献
918.
To improve predictive accuracy, new hybrid models are proposed for container throughput forecasting based on wavelet transforms and data characteristic analysis (DCA) within a decomposition-ensemble methodology. Because of the complexity and nonlinearity of the time series of container throughputs at ports, the methodology decomposes the original time series into several components, which are rather simpler sub-sequences. Consequently, difficult forecasting tasks are simplified into a number of relatively easier subtasks. In this way, the proposed hybrid models can improve the accuracy of forecasting significantly. In the methodology, four main steps are involved: data decomposition, component reconstruction based on the DCA, individual prediction for each reconstructed component, and ensemble prediction as the final output. An empirical analysis was conducted for illustration and verification purposes by using time series of container throughputs at three main ports in Bohai Rim, China. The results suggest that the proposed hybrid models are able to forecast better than do other benchmark models. Forecasting may facilitate effective real-time decision making for strategic management and policy drafting. Predictions of container throughput can help port managers make tactical and operational decisions, such as operations planning in ports, the scheduling of port equipment, and route optimization. 相似文献
919.
基于无人船机动灵活、安全性高、可在常规调查平台受限的水域作业的特点,将其引入海洋调查领域,作为一种新型调查平台使用。海洋调查无人船主要用于海洋环境观测和海底探测,目前其发展的关键在于如何降低平台对任务载荷的扰动,保证循线精度,提高通信系统的可靠性。根据水深、水动力和水底地形地貌等条件,将无人船工作环境分为岛礁区、滨海区、浅海区、半深海区和深海区5类;结合作业环境,以无人船的体量和吃水深度为依据,建议将其分为微型平台、小型平台、中型平台、大型平台和超大型平台,并对适配任务载荷作出分析。 相似文献
920.