全文获取类型
收费全文 | 17284篇 |
免费 | 1640篇 |
专业分类
公路运输 | 6361篇 |
综合类 | 4455篇 |
水路运输 | 3546篇 |
铁路运输 | 4022篇 |
综合运输 | 540篇 |
出版年
2025年 | 146篇 |
2024年 | 446篇 |
2023年 | 384篇 |
2022年 | 450篇 |
2021年 | 740篇 |
2020年 | 709篇 |
2019年 | 411篇 |
2018年 | 321篇 |
2017年 | 321篇 |
2016年 | 384篇 |
2015年 | 521篇 |
2014年 | 1305篇 |
2013年 | 1117篇 |
2012年 | 1650篇 |
2011年 | 1633篇 |
2010年 | 1139篇 |
2009年 | 1094篇 |
2008年 | 1068篇 |
2007年 | 1390篇 |
2006年 | 1308篇 |
2005年 | 737篇 |
2004年 | 443篇 |
2003年 | 269篇 |
2002年 | 226篇 |
2001年 | 177篇 |
2000年 | 104篇 |
1999年 | 90篇 |
1998年 | 47篇 |
1997年 | 65篇 |
1996年 | 52篇 |
1995年 | 33篇 |
1994年 | 24篇 |
1993年 | 25篇 |
1992年 | 22篇 |
1991年 | 25篇 |
1990年 | 11篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 4篇 |
1984年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
重点围绕城市轨道交通国产MTC-I型列车控制系统(CBTC)独立第三方安全评估与认证工作,阐述了信号安全攸关系统的技术标准规范体系、安全完整度等级、安全认证类型、风险评价原则等概念与定义。基于安全认证、系统生命周期、安全保障架构、项目风险管理、安全审核与评估等具体内容描述了MTC—I型CBTC系统通用产品安全认证实践过程。对建立我国城轨交通行业发展的安全认证体系、实施策略以及风险管控原则等安全认证要素进行了分析与探讨。 相似文献
2.
3.
4.
陆振朋 《铁路通信信号工程技术》2012,9(4):20-21,25
主要介绍计算机联锁图表的作用,分析目前计算机联锁图表存在的一些问题。为适应计算机联锁车站的工程特点,提出对现有计算机联锁图表编制的改进原则和编制方法。 相似文献
5.
该文介绍了公路沥青路面结构设计的方法。路面厚度设计是在结构组合设计的基础上,通过力学和性能分析确定各结构层所需的厚度;同时,利用结构分析也可了解路面结构的应力和位移状况,从而判断结构层组合的合理性,并进行相应的调整。 相似文献
6.
BRAXTON C. DAVIS 《Coastal management》2013,41(4):339-354
Area-based management approaches may be beneficial in integrating sectoral, single-purpose laws and regulations; however, these benefits may not be attained if special area designations are equally sectoral or single-purpose in nature. Over 60 types of special management areas were documented under U.S. coastal programs, and a new classification scheme was developed to allow comparisons and analyses across programs. Results indicate that requirements and incentives for special area designations under the Coastal Zone Management Act did little to standardize or influence area-based management systems associated with state and territory coastal programs. Further, the absence of clear patterns within and between coastal programs with respect to special area policies suggests a limited commitment to this important aspect of coastal management. Continued research is needed to document the effectiveness of the various area-based management approaches presented in this article. 相似文献
7.
Glenn D. Aguilar Hiroyuki Yamamoto Takeo Koyama 《Journal of Marine Science and Technology》1996,1(3):138-148
The development of a parametric hull form design system utilizing combined knowledge-based and objectoriented methodologies,
approaches, and techniques is the major purpose of this research. One objective was the development of a powerful, intuitive,
and parameter-based hull definition system with a related hull definition advisory system that would provide useful and necessary
advice to the user. Object and knowledge modeling activities were conducted during the analysis and design stage to facilitate
the implementation of a hull design program and advisory system. The hull design system includes the generation of a geometric
model from a process of aggregating simple user-selected shapes representing different boundaries. Design involves the capability
to vary simple parameters such as entrance angles, length-breadth ratios, and radii to define local and general surface geometries.
Hydrostatic calculations are included for analysis; results are referred to an advisory system for evaluation and the determination
of the acceptability of parameters and analysis results. The advisory system includes a knowledge bases consisting of hull
form databases, results of the statistical analysis of data, design parameter constraints, and expert knowledge acquired from
designers, reference materials, and technical reports. Use of the design tool with the advisory system results in the rapid
generation of hull forms and associated design evaluations. Flexibility in decision making results from the separation of
the design system from the advisory system. The independence of the two systems allows for a wide range of user experience
with experts using the design tool with minimal reference to the advisory system. On the other hand, the expertise and knowledge
stored in the advisory system is fully available to inexperienced designers and users. 相似文献
8.
9.
本船作为车客渡船具有多用途、多任务的特点,适应性强.该文从型线设计、总体布置、稳性计算等方面,概要介绍了本船的一些设计特点. 相似文献
10.