全文获取类型
收费全文 | 1846篇 |
免费 | 108篇 |
专业分类
公路运输 | 332篇 |
综合类 | 695篇 |
水路运输 | 456篇 |
铁路运输 | 372篇 |
综合运输 | 99篇 |
出版年
2024年 | 12篇 |
2023年 | 26篇 |
2022年 | 47篇 |
2021年 | 43篇 |
2020年 | 56篇 |
2019年 | 56篇 |
2018年 | 41篇 |
2017年 | 84篇 |
2016年 | 66篇 |
2015年 | 91篇 |
2014年 | 61篇 |
2013年 | 87篇 |
2012年 | 139篇 |
2011年 | 75篇 |
2010年 | 65篇 |
2009年 | 119篇 |
2008年 | 161篇 |
2007年 | 146篇 |
2006年 | 169篇 |
2005年 | 95篇 |
2004年 | 78篇 |
2003年 | 56篇 |
2002年 | 29篇 |
2001年 | 32篇 |
2000年 | 25篇 |
1999年 | 11篇 |
1998年 | 17篇 |
1997年 | 20篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 10篇 |
1993年 | 7篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 2篇 |
排序方式: 共有1954条查询结果,搜索用时 281 毫秒
991.
随着隧道运营时间的增加,隧道的结构安全问题日益突出,合理评价运营盾构隧道结构安全对保障隧道安全运营和科学养护具有重要意义。针对这一问题,根据隧道结构特点确定盾构隧道结构安全评价指标,通过理论分析确定评价指标的分级标准;确立运营盾构隧道结构安全评价指标体系;以模糊综合评价法、层次分析法为基础,综合考虑指标之间相关性和不可逆特性,建立修正的模糊综合评价法;利用该方法并结合现场检测数据,对实际隧道结构安全进行评价。修正后的模糊综合评价法,不仅能体现单一因素指标对评价结果影响的敏感性而且使综合评价结果更合理,能更科学地指导盾构隧道结构养护工作。 相似文献
992.
993.
张大刚 《船舶与海洋工程学报》2012,11(3):341-350
Transportation of tension leg platform(TLP) structures for a long distance has always been associated with the use of a heavy semi-transport vessel.The requirements of this type of vessel are always special,and their availability is limited.To prepare for the future development of South China Sea deepwater projects,the China Offshore Oil Engineering Corporation has recently built a heavy lift transport vessel-Hai Yang Shi You 278.This semi-submersible vessel has a displacement capacity of 50k DWT,and a breath of 42 meters.Understanding the vessel’s applicability and preparing it for use in future deepwater projects are becoming imminent needs.This paper reviews the current critical issues associated with TLP transportation and performs detailed analysis of the designed TLP during load-out and transportation.The newly built COOEC transportation vessel HYSY 278 was applied to dry transport of the TLP structure from the COOEC fabrication yard in Qingdao to an oil field in South China Sea.The entire process included the load-out of the TLP structure from the landsite of the fabrication yard,the offloading and float-on of the platform from the vessel,the dry transport of the TLP over a long distance,and the final offloading of the platform.Both hydrodynamic and structure analysis were performed to evaluate the behavior of the transport vessel and TLP structure.Special attention was paid to critical areas associated with the use of this new vessel,along with any potential limitations.The results demonstrate that HYSY 278 can effectively be used for transporting the structure with proper arrangement and well-prepared operation.The procedure and details were presented on the basis of the study results.Special attention was also given to discussion on future use based on the results from the analysis. 相似文献
994.
995.
We formulate a game-theoretic model of a concession agreement between a government and a private party, a concessionaire, who has to engage a set of service providers as part of the operating responsibilities. We use the model to examine the importance of a government's tax policy to induce private investments in transportation infrastructure. Our analysis brings to fore insights that are useful in the design of partnership agreements, such as the importance of early and binding government commitments to ensure stable partnerships, and thus, successful projects. Our analysis shows that these strong commitments are even more critical in situations where the success of the partnership requires participation of additional, self-interested parties, such as specialized service providers. Finally, we consider variations of the model where government preferences are explicitly captured, and where the returns from the fixed cost portion of the concessionaire's investment are exempt from taxes. We show that both variations can lead to outcomes where the concessionaire's tax burden is shifted to the service providers. This flexibility can be critical in the design of partnership agreements for (high-risk or highly specialized transportation) projects where additional incentives may be needed to induce private party participation. 相似文献
996.
997.
电容式水分仪是一种利用介电常数原理测量物质含水量的检测仪。该水分仪以MSP430F169单片机为控制核心,以单片式电容传感器为敏感元件,主要用于地暖供热管道渗漏和建筑物渗漏的检测。本文详细分析了单片式电容传感器的结构、测量原理及电容值计算、水分仪检测系统的硬件设计、软件设计及抗干扰设计。实践表明,该仪表具有较高的准确性及应用推广价值。 相似文献
998.
999.
现今集装箱堆场作业设备装卸工艺呈现多样化趋势,主流作业设备以RTG、ERTG、RMG为主。大连港的集装箱码头对以上三种装卸工艺均有应用,对此三种设备的优缺点、能耗数据等方面进行分析、对比,提出合理建议。 相似文献
1000.