全文获取类型
收费全文 | 1870篇 |
免费 | 112篇 |
专业分类
公路运输 | 321篇 |
综合类 | 697篇 |
水路运输 | 485篇 |
铁路运输 | 382篇 |
综合运输 | 97篇 |
出版年
2024年 | 12篇 |
2023年 | 33篇 |
2022年 | 51篇 |
2021年 | 46篇 |
2020年 | 63篇 |
2019年 | 63篇 |
2018年 | 56篇 |
2017年 | 89篇 |
2016年 | 75篇 |
2015年 | 96篇 |
2014年 | 57篇 |
2013年 | 85篇 |
2012年 | 136篇 |
2011年 | 64篇 |
2010年 | 55篇 |
2009年 | 110篇 |
2008年 | 152篇 |
2007年 | 150篇 |
2006年 | 164篇 |
2005年 | 100篇 |
2004年 | 76篇 |
2003年 | 58篇 |
2002年 | 29篇 |
2001年 | 36篇 |
2000年 | 29篇 |
1999年 | 13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1982条查询结果,搜索用时 12 毫秒
61.
本文对白升式钻井平台的方案评价指标体系和评价方法进行了研究,提出了一套适用于自升式钻井平台的方案评价指标体系,并采用改进的灰关联分析法进行平台方案的优选,初步分析和计算实例表明,该评价指标体系和评价方法是适用和可靠的.通过对联分析方法进行改进,建立了适用于自升式钻井平台方案选优的灰关联多目标综合评价模型,该模型在灰关联分析的基础上引进层次分析法计算各指标的权重值,既在一定程度上考虑了设计方案各指标间的关联性,反应了事物的客观本质,又能体现船东的主观偏好和设计者的设计需要.同时该方案评价指标体系和评价方法具有拓展性,可应用于其它类型的移动式平台,作为方案选择时的参考依据. 相似文献
62.
iFIX中如何通过GES OPC Server与GE PLC通讯 总被引:1,自引:0,他引:1
介绍了OPC应用的工业控制领域。OPC采用客户机/服务器体系结构,是目前工业控制中广泛采用的一项技术。OPC接口凭借其开放性、可靠性,已经成为一种国际标准。各个自动化厂商的产品可以通过OPC接口实现无缝连接。本文主要阐述iFIX组态软件的OPC连接功能,具体介绍了iFix作为OPC客户端,如何通过GES OPC Server读取GE PLC符号变量,并给出具体实施方案。 相似文献
63.
Yukinobu Nagata Koji Gotoh Masahiro Toyosada 《Journal of Marine Science and Technology》2009,14(1):104-114
Many accidents are caused by fatigue in welded built-up steel structures, and so it is important to estimate the fatigue lives
of such structures quantitatively for safety reasons. By assuming that fatigue cracks cannot grow without an accumulation
of alternating tensile/compressional plastic strain, one of the authors identified an improved effective stress intensity
factor range ΔK
RPG based on the re-tensile plastic zone generating (RPG) load, which represents the driving force for fatigue cracks, and suggested
that ΔK
RPG should be used as the parameter to describe fatigue crack growth behavior. The “FLARP” numerical simulation code in which
ΔK
RPG is implemented as the fatigue crack growth parameter, was developed in order to predict fatigue crack initiation and propagation
behavior. In this paper, it is demonstrated that FLARP gives accurate estimates for fatigue life by comparing the estimated
fatigue crack growth curves and S–N curves with the experimental results for in-plane gusset welded joints, which are used in many welded steel structures. Moreover,
the effect of induced bending moment due to the linear misalignment in the out of plane direction on the fatigue strength
of in-plane gusset welded joints is investigated through numerical simulations. 相似文献
64.
本文通过对C/S和B/S模式物资管理系统在使用中优缺点的分析,提出了采用以C/S模式为主,B/S模式为辅的混合模式对当前单一的C/S模式物资管理系统进行改造的设想。在这种混合模式下,物资管理部门内部采用C/S模式,便于实现复杂的管理功能及可靠的安全机制:对于非物资管理部门的用户,采用B/S模式,便于统一管理与维护。最后,本文还对系统改造的开发环境和技术做了探讨。 相似文献
65.
66.
Joachim F. Wohlwill 《Coastal management》2013,41(3-4):225-248
Abstract The focus of this paper is theoretical, as well as methodological. It reviews previous studies of visual impact and reports research by the author on people's evaluation of the appropriateness of different man‐made facilities in different coastal‐area contexts and other environments. In this study, subjects were asked to react to slides developed through the use of landscape models and experimental facilities to simulate the appearance of a building in the landscape, while systematically varying the visual relatedness between the two. Specific interest centered on the variable of congruity vs. contrast between the appearance of the building and its landscape context, manipulated by co‐varying the attributes of color and size to create a five‐point scale of contrast/obtrusiveness. The hypothesis was that judgments of appropriateness, and to a lesser extent judgments of liking, would vary inversely with level of contrast. The role of two further variables, the functional significance of the building in its setting, and the character of the setting itself, was also investigated. The author reviews methodological issues involved where subjects respond to visual stimuli for purposes of judging change in visual quality. These methodological issues include: stimulus‐selection and problems of simulation, choice of response measures, and choice of respondents, and the treatment of individual differences. The author calls for development of standardized scales and indices such as “perceptually‐relevant environmental quality indicators.” 相似文献
67.
赵河 《内蒙古公路与运输》2007,(3)
结合GTM法技术在河北省张石高速公路中的实践应用,介绍GTM法的设计原理、施工工艺和质量控制体系,尤其是对施工过程质量控制点和沥青路面最大密实度标准的研究分析,有效地降低了工程施工费用,提高了路面的服务寿命。 相似文献
68.
69.
70.