全文获取类型
| 收费全文 | 363篇 |
| 免费 | 29篇 |
专业分类
| 公路运输 | 42篇 |
| 综合类 | 158篇 |
| 水路运输 | 78篇 |
| 铁路运输 | 62篇 |
| 综合运输 | 52篇 |
出版年
| 2025年 | 1篇 |
| 2024年 | 4篇 |
| 2023年 | 2篇 |
| 2022年 | 9篇 |
| 2021年 | 11篇 |
| 2020年 | 10篇 |
| 2019年 | 9篇 |
| 2018年 | 10篇 |
| 2017年 | 18篇 |
| 2016年 | 17篇 |
| 2015年 | 22篇 |
| 2014年 | 16篇 |
| 2013年 | 37篇 |
| 2012年 | 34篇 |
| 2011年 | 24篇 |
| 2010年 | 17篇 |
| 2009年 | 18篇 |
| 2008年 | 18篇 |
| 2007年 | 24篇 |
| 2006年 | 33篇 |
| 2005年 | 19篇 |
| 2004年 | 13篇 |
| 2003年 | 5篇 |
| 2002年 | 6篇 |
| 2001年 | 9篇 |
| 2000年 | 3篇 |
| 1998年 | 1篇 |
| 1995年 | 1篇 |
| 1994年 | 1篇 |
排序方式： 共有392条查询结果，搜索用时 0 毫秒
211.
庄东晓 《广州航海高等专科学校学报》2009,17(2):8-10
以广东省水域发生的三起重特大水上交通事故为例,对现有水上安全监督管理体制及传统的监督管理措施进行更深层次的思考,认为引入和实行“引导型政府职能模式”,是目前建立我国水上安全监督管理长效的运行机制的关键． 相似文献
212.
针对航运的周期性特征,研究了处于航运上行期的多航线多船型配船与租船的联合优化问题,以及处于航运下行期的多航线多船型配船与运力闲置的联合优化问题,分别构建了混合整数规划模型,基于模型特点开发了相应的模拟退火算法,通过小规模问题实验确定了模型与算法参数,并通过与Lingo最优解的对比,显示了模型及算法的有效性;同时,现实规模问题的算例分析进一步验证了算法的实用性. 相似文献
213.
214.
借助对列车优先级、节点、替代弧和替代对等参数的定义,以列车追踪运行间隔时间、列车连发间隔时间和列车间越行地点等为约束条件,以替代图中最长路径最短为优化目标,建立基于替代图的列车运行调整计划编制及优化模型.采用本地搜索算法对模型求解,经过原始计划生成和初级优化,得到有瑕疵(冲突)的但资源利用率较高的初始调整计划.当初始调整计划未满足需求或计划在实施过程中受到扰动需要修正时,采用分层多级优化分枝定界算法,对初始调整计划对应的替代图进行进一步的优化,得到优化的列车运行调整计划.由于替代图与列车运行调整计划的对应关系,用这2种算法对替代图分阶段求解和优化,可以得到满足不同需求的调整计划.通过对模拟环境的仿真,验证了模型和优化方法的完整性和可行性. 相似文献
215.
216.
Lonworks现场总线技术和基于TCP/IP的局域网(LAN)技术是目前用于构建桥梁健康监测系统的数据通信系统最为主流的2种技术.对这2项技术的原理进行了分析,并探讨了其在桥梁健康监测系统中的应用. 相似文献
217.
Coastal areas are under increasing pressure driven by demands for coastal space, primarily though population growth, in migration and the need for space for socioeconomic activities. The pressures and associated changes to the coastal environment need to be managed to ensure long-term sustainability. South Africa has enacted an Integrated Coastal Management Act (ICM Act) to facilitate dedicated management of its coastal environment. The implementation has been met with a number of challenges, primarily relating to financial and human capacity constraints, particularly at the local government level. Given that the ICM Act devolves powers to local government, it is imperative that implementation challenges be addressed. This paper focuses on KwaZulu-Natal, one of four South African coastal regions, which is a renowned tourist destination and home to 11.1 million people (Statistics South Africa 2015). This paper considers the state of coastal management, as well as implementation challenges being experienced at a local governance level, and highlights ways to address these. Data were acquired through questionnaire surveys and semistructured interviews. The Drivers-Pressures-State-Impact-Response (DPSIR) framework was used to identify relevant ICM issues and concerns and develop potential actions for improving the implementation of coastal management activities and the ICM Act. In the assessment of the ICM governance and implementation to date, a key concern identified was a general lack of coastal management knowledge among officials. It was specifically identified that knowledgeable management and capacity-building required championing from the provincial government in order to more efficiently and effectively implement the objectives of the ICM Act through an improved understanding of the coastal environment, its functioning and management. 相似文献
218.
首先介绍了舰艇编队辅助决策系统的功能和组成结构;然后对其多目标威胁判断分系统的功能进行分析,并提供相应的实现方法;最后着重讨论了决策分系统的目标分配和火力分配,同时提供了一套目标分配和火力分配的模型及其算法。 相似文献
219.
Knowledge of thermal history is the basic condition for studying the structure - properties of welded joints. The determinant of thermal history is the thermal cycle, whose in-situ measurements are still a big challenge. Water as the welding environment complicates this issue even more. The article presents a method to determine an equation for calculating t8/5 cooling times for underwater gas metal arc welding of unalloyed steels using the local dry cavity method. The work uses the contact method of temperature measurements with the use of thermocouples to obtain the temperature changes of the points of welded joints covered by the thermal field. On this basis, the values of the t8/5 cooling times were determined. A regression analysis of the Response Surface Method was used to determine the equation, which resulted in a second-order model with interactions. Statistically significant factors were determined (thickness of welded elements and heat input value) and the model veracity was confirmed as the assumptions of normality and homogeneity of variance (homoscedasticity) of the residuals were met. The t8/5 cooling time values depend on the thickness of the welded elements and heat input value in a nonlinear way. In terms of the test conditions, the cooling times ranged from 3.0 to 7.7 s. The equation allowed for the calculation of t8/5 cooling times during underwater welding of unalloyed steels using the local dry cavity method based on the variability of the experimental conditions with satisfactory accuracy. 相似文献
220.
ABSTRACT As maintenance and operation costs increase with usage over time, equipment is replaced when the value of new equipment is more attractive. Some methods have been developed to solve this problem. In the public transport sector, such problems are frequently analyzed by fleet managers and determined by bus age restriction regulations. We propose an Integer Programming model that integrates both budgetary and environmental constraints (CO2 emissions) which, as far as we know, have not previously been studied in conjunction. The study aims to determine the optimal replacement plan for a fleet of diesel buses of different size, age, maintenance costs and emissions rates, with new (less polluting) diesel buses over a time horizon of 50 years. The results indicate that it is possible to reduce emissions with a low annual budget using an optimal replacement policy. 相似文献