全文获取类型
收费全文 | 2098篇 |
免费 | 202篇 |
专业分类
公路运输 | 632篇 |
综合类 | 719篇 |
水路运输 | 459篇 |
铁路运输 | 366篇 |
综合运输 | 124篇 |
出版年
2024年 | 13篇 |
2023年 | 28篇 |
2022年 | 74篇 |
2021年 | 102篇 |
2020年 | 89篇 |
2019年 | 64篇 |
2018年 | 63篇 |
2017年 | 41篇 |
2016年 | 57篇 |
2015年 | 79篇 |
2014年 | 210篇 |
2013年 | 142篇 |
2012年 | 178篇 |
2011年 | 202篇 |
2010年 | 152篇 |
2009年 | 138篇 |
2008年 | 119篇 |
2007年 | 174篇 |
2006年 | 162篇 |
2005年 | 68篇 |
2004年 | 40篇 |
2003年 | 24篇 |
2002年 | 14篇 |
2001年 | 18篇 |
2000年 | 14篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有2300条查询结果,搜索用时 31 毫秒
991.
This paper addresses a highly researched area, the reshuffling problem in ports, using a new paradigm-modified containership service order in light of credit risk assessment. Container stacking and reshuffling operations can cause ship delays and additional risk. In deep-sea terminals, outbound containers are tightly stacked according to the retrieval sequence. Due to lack of space, terminals stack containers in multiple tiers. This means any delay in the arrival of a ship can impose extra handlings and reshuffling of containers delaying future cargo handling. This paper addresses the reshuffling problem with a concept similar to the credit scoring and rating of creditworthiness used in the banking industry. By utilizing this comparison to the banking credit risk concept, a heuristic estimation model is proposed that illustrates the side effects of unscheduled modifications in containership service order. Further, the mega-ship trend amplifies the reshuffling debate. Probability of delay, reshuffles given delay, and call size at delay are introduced as the three-point risk metrics of the model. Numerical simulations illustrate the functionality to develop terminal stacking strategies as well as emphasize the mega-ship phenomenon and its side effects on terminals (i.e. yard operation deadlock). 相似文献
992.
993.
Liquefied natural gas (LNG) has emerged as a possible alternative fuel for freight railroads in the United States, due to the availability of cheap domestic natural gas and continued pursuit of environmental and energy sustainability. A safety concern regarding the deployment of LNG-powered trains is the risk of breaching the LNG tender car (a special type of hazardous materials car that stores fuel for adjacent locomotives) in a train accident. When a train is derailed, an LNG tender car might be derailed or damaged, causing a release and possible fire. This paper describes the first study that focuses on modeling the probability of an LNG tender car release incident due to a freight train derailment on a mainline. The model accounts for a number of factors such as FRA track class, method of operation, annual traffic density level, train length, the point of derailment, accident speed, the position(s) of the LNG tender(s) in a train, and LNG tender car design. The model can be applied to any specified route or network with LNG-fueled trains. The implementation of the model can be undertaken by the railroad industry to develop proactive risk management solutions when using LNG as an alternative railroad fuel. 相似文献
994.
Weaving segments are potential recurrent bottlenecks which affect the efficiency and safety of expressways during peak hours. Meanwhile, they are one of the most complicated segments, since on- and off-ramp traffic merges, diverges and weaves in the limited space. One effective way to improve the safety of weaving segments is to study crash likelihood using real-time crash data with the objective of, identifying hazardous conditions and reducing the risk of crashes by Intelligent Transportation Systems (ITS) traffic control. This study presents a multilevel Bayesian logistic regression model for crashes at expressway weaving segments using crash, geometric, Microwave Vehicle Detection System (MVDS) and weather data. The results show that the mainline speed at the beginning of the weaving segments, the speed difference between the beginning and the end of weaving segment, logarithm of volume have significant impacts on the crash risk of the following 5–10 min for weaving segments. The configuration is also an important factor. Weaving segment, in which there is no need for on- or off-ramp traffic to change lane, is with high crash risk because it has more traffic interactions and higher speed differences between weaving and non-weaving traffic. Meanwhile, maximum length, which measures the distance at which weaving turbulence no longer has impact, is found to be positively related to the crash risk at the 95% confidence interval. In addition to traffic and geometric factors, wet pavement surface condition significantly increases the crash ratio by 77%. The proposed model along with ITS, e.g., ramp metering, Dynamic Message Sign (DMS), and high friction surface treatment can be used to enhance the safety of weaving segments in real-time. 相似文献
995.
996.
997.
企业只有重视合同的重要性,做好合同管理,才能有效降低工程风险,维护企业的利益,增加利润.结合实践经验,提出应通过合同管理提高企业的核心竞争力,在建设项目中推行项目法人负责制、招标投标制、建设监理制改革,坚持从中国国情出发管理项目.以强化合同管理为突破口、以法治理念为基础的合同管理是项目管理的灵魂. 相似文献
998.
999.
研究目的:本文主要针对郴宁公路万华岩右幅隧道(在建)浅埋段受地表水泥厂石灰石长胶带输送廊道交叉跨越施工影响,研究分析在初期支护条件下隧道掌子面发生早期坍塌的原因,后期状况下通过钢架支护试验类比和支撑近似分析两种方法得到冒顶最终发生的原因;从经济技术和风险方面对后期隧道加固方案进行探讨;最后针对隐藏风险,提出合理避险,减少损失。研究结论:对于上下近临(接)施工,必须遵照有关建设程序报批;同期施工双方在本文情况下,应遵循先下后上、先重后轻的施工顺序;对初期支护状态下的濒临冒顶的全~强风化围岩、大跨浅埋隧道应优先采用地表注浆方案,以确保人员安全和方案最终实施。 相似文献
1000.