全文获取类型
收费全文 | 1080篇 |
免费 | 24篇 |
专业分类
公路运输 | 317篇 |
综合类 | 288篇 |
水路运输 | 287篇 |
铁路运输 | 176篇 |
综合运输 | 36篇 |
出版年
2024年 | 3篇 |
2023年 | 6篇 |
2022年 | 28篇 |
2021年 | 46篇 |
2020年 | 26篇 |
2019年 | 17篇 |
2018年 | 13篇 |
2017年 | 16篇 |
2016年 | 18篇 |
2015年 | 32篇 |
2014年 | 42篇 |
2013年 | 53篇 |
2012年 | 66篇 |
2011年 | 78篇 |
2010年 | 82篇 |
2009年 | 77篇 |
2008年 | 88篇 |
2007年 | 92篇 |
2006年 | 83篇 |
2005年 | 60篇 |
2004年 | 43篇 |
2003年 | 26篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 15篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 5篇 |
1994年 | 1篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有1104条查询结果,搜索用时 847 毫秒
41.
42.
Byung Hwa Park Nam Po Kim Jung Seok Kim Kang Yong Lee 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2006,44(12):887-901
This paper addresses the use of finite-element (FE) analysis to calculate the fatigue strength of a bogie frame, for the development of tilting trains in Korea. A multi-body dynamic analysis was performed to extract the load condition by tilting on curves. Using the results of the multi-body dynamic analysis and the load scenario setout in the UIC standard, FE analysis was performed to obtain the stress distribution and to calculate the fatigue strength. An attempt was made to minimize the weight of the bogie frame using a back-propagation artificial neural network (ANN). The results of this study reveal that the stresses at some nodes are near the fatigue limit in the Goodman diagram and by using back-propagation ANN, the weight of the bogie frame could be reduced by 4.7%. 相似文献
43.
针对目前铁道部有关加强行车安全的文件与设计概算编制规定不协调的问题,笔者提出了自己的看法. 相似文献
44.
SONG Zhi-ming KANG Feng-ju TANG Kai and CHU Yan-jun Marine College Northuxstern Polytechnical University Xi'''' an China 《船舶与海洋工程学报》2003,2(2):40-45
Realistic simulation of underwater scene is always difficult because of the special and complex vision effects in underwater space. Seabed is an important part of underwater environment. This paper describes the methods for seabed scene simulation based on OpenGL. It includes construction of fluetuant terrain based on the random sinusoidal algorithm, simulation of seabed flicker effect by means of circular texture mapping and generation of turbidity effect by using fog techniques. For the application based on the leading high level 3D development environment-Vega, underwater scene simulation is still a difficulty since there is no module for it. Based on the analysis of Vega software and the research on seabed scene simulation methods, a Vega extending module named “Underwater Space” was created through developing module class and extending lynx interface. The module class was designed through developing DLL written in C . The Lynx was extended through developing keyword configure file, GUI configure file and lynx plug-in DLL. The problem that Vega can‘t simulate underwater space, is elementarily resolved. The results show that this module is efficient, easy using, and the seabed scene images am vivid. 相似文献
45.
针对异形屋面结构中经常采用的不规则形状折梁设计,施工过程中充分利用AutoCAD三维立体图的方式,完成不规则折梁钢筋的翻样,化解翻样难度,提高翻样效率,保证翻样精度,同时阐述了如何解决施工过程中遇到的安装问题。 相似文献
46.
47.
Development of hot stamped center pillar using form die with channel type indirect blank holder 总被引:1,自引:0,他引:1
H. S. Choi B. M. Kim K. J. Nam S. Y. Ha S. H. Cha C. G. Kang 《International Journal of Automotive Technology》2011,12(6):887-894
The hot stamping process has been used in the automotive industry to reduce the weight of the body-in-white and to increase
passenger safety via improved crashworthiness. However, defects such as fracture and wrinkle occur when hot stamping is performed
using a conventional drawing or forming method. In this study, a channel-type indirect blank holder (CIBH) is proposed to
develop a high-strength center pillar in form-type hot stamping, so that the aforementioned drawbacks are overcome. This type
of blank holder plays an important role in reducing severe wrinkling at the flange; such wrinkling leads to folding after
the completion of form-type hot-stamping. First, we investigated the effect of the channel shape on the indirect blank holding
force by using a simplified two-dimensional plane-strain stamping process. Second, we selected the slope angle and corner
radius of the channel as the main shape parameters by finite element analysis and artificial neural network (ANN). It is known
that fracture at the hot formed wall and wrinkle at the flange are significantly affected by the slope angle of the channel,
and the appropriate value for eliminating fracture and wrinkle is determined to be 99°. By performing hot stamping using a
form die with the selected channel, we can manufacture a high-strength center pillar without wrinkle and fracture. 相似文献
48.
某些作用在舰船结构上的瞬态动载荷,由于受到客观条件限制(比如空间狭小),不方便直接通过压力传感器获得其大小,而该载荷对于船体结构设计又关系重大,如何取得外载荷曲线便成了十分关键的问题。针对实船某承受特殊冲击载荷的基座结构,通过测量其结构动应变,利用材料应变-应力关系曲线得出了冲击载荷的时间历程曲线,最后用有限元法对该冲击载荷测量曲线进行验证。结果表明,当结构应变率小于3mm/mm/s时,可采用静态材料应变-应力关系曲线对结构冲击载荷进行测量计算,从而为此类结构外载荷测量方法提供参考。 相似文献
49.
近年来,我国经济转型进程不断加快,各大企业也面临产品升级的压力,轻量化便是商用卡车产品升级的趋势之一,可对汽车安全、高效运输以及节能减排等方面具有促进作用。本文对商用卡车轻量化的发展贡献与需求分析进行讨论,并在此基础上,提出商用卡车轻量化的发展趋势,以期对轻量化设计起到借鉴作用。 相似文献
50.
When using limited funds on bicycle facilities, it would be helpful to know the extent to which a new facility will be used. If a bicycle lane is added to a street, how many bicyclists will no longer use the adjacent sidewalk? If a separate bicycle path is constructed, how many bicyclists will move from the street or sidewalk? This study seeks to identify factors that explain a bicyclist’s choice between available facility choices—off-street (sidewalk and bicycle path) or on-street (bicycle lane and roadway). This paper investigates these issues through a survey of bicyclists headed to Purdue University in West Lafayette, IN, USA. The first data collected to address these questions were “site-based”. Bicyclists were interviewed on campus at the end of their trips and asked which part of the cross-sections along their routes they had used—on-street or off-street. The characteristics of a particular cross-section of street right-of-way were then compared against the characteristics of each bicyclist and his/her observed choice of street, sidewalk, lane, or path. Later, “route-based” serial data were also added. The study developed a mixed logit model to analyze the bicyclists’ facility preferences and capture the unobserved heterogeneity across the population. Effective sidewalk width, traffic signals, segment length, road functional class, street pavement condition, and one-way street configuration were found to be statistically significant. A bicycle path is found to be more attractive than a bicycle lane. Predictions from the model can indicate where investments in particular bicycle facilities would have the most desirable response from bicyclists. 相似文献