全文获取类型
收费全文 | 4564篇 |
免费 | 147篇 |
专业分类
公路运输 | 967篇 |
综合类 | 1398篇 |
水路运输 | 1371篇 |
铁路运输 | 522篇 |
综合运输 | 453篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 74篇 |
2021年 | 92篇 |
2020年 | 87篇 |
2019年 | 44篇 |
2018年 | 371篇 |
2017年 | 325篇 |
2016年 | 291篇 |
2015年 | 88篇 |
2014年 | 117篇 |
2013年 | 165篇 |
2012年 | 247篇 |
2011年 | 387篇 |
2010年 | 423篇 |
2009年 | 233篇 |
2008年 | 380篇 |
2007年 | 352篇 |
2006年 | 244篇 |
2005年 | 223篇 |
2004年 | 111篇 |
2003年 | 119篇 |
2002年 | 76篇 |
2001年 | 54篇 |
2000年 | 50篇 |
1999年 | 24篇 |
1998年 | 25篇 |
1997年 | 18篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 6篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 2篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
排序方式: 共有4711条查询结果,搜索用时 15 毫秒
391.
392.
针对当前建筑设计中越来越多地采用幕墙作为体现建筑效果和幕墙工程从设计、施工到验收过程中的许多不规范、不合理、不安全的现状,本文从幕墙结构的设计、外形的设计、构造的要求、材料的选用、构件、结构连接点的施工、制作及验收等6个方面,系统地阐述了常见的通病和贯彻国家以及行业规范标准的执行要点,文章对目前正在进入实施阶段的各类幕墙工程的设计、施工质量控制和如何针对幕墙工程开展质量监理工作具有一定的交流和参考作用. 相似文献
393.
Zbigniew Gronostajski Marek Hawryluk Marcin Kaszuba Paweł Widomski Jacek Ziemba 《International Journal of Automotive Technology》2017,18(4):653-662
This study is focused on tools used in the industrial hot forging process of a front wheel forging (eventually–gear wheel) manufactured for the automotive industry. Four different variants were applied for the tools: 2 die inserts were coated with two different hybrid layers (GN + PVD type), i.e. AlCrTiN and AlCrTiSiN, one insert was only nitrided, and one was pad welded, to improve tool durability. The tool wear was analysed and represented by the material degradation on the working surface, based on the 3D scanning and the material growth of the periodically collected forgings. Additionally, the scanned tools were divided into two areas, in which it was found, based on the reliminary analysis, that various degradation mechanisms are predominant. Microstructural and hardness measurements of the analyzed tools were also performed. Based on the results, it was found that, in the central part of the die insert (area A), thermo-mechanical fatigue and wear occurred, while in the area of the bridge insert (area B), only abrasive wear could be observed. For these areas (A and B), the loss of material was determined separately. In area A for the inserts with hybrid layer GN+AlCrTiSiN and gas nitrided, an intensive increase of wear took place, which was not observed for the pad welded and GN+AlCrTiN layer insert, for which, together with the increase of the forging number, a proportional growth of the loss of material occurred. In area B the weakest results were obtained for the insert with GN+AlCrTiSiN layer, while wear of other die inserts grew similar and proportional. 相似文献
394.
Hydrostatic stresses of copper dual-damascene interconnects are calculated by a commercial finite element software in this
paper. The analytical work is performed to examine the effects of different low-k (k is permittivity) dielectrics, barrier layer and aspect ratio of via on hydrostatic stress distribution in the copper interconnects.
The results of calculation indicate that the hydrostatic stresses are highly non-uniform throughout the copper interconnects
and the highest tensile hydrostatic stress exists on the top interface of lower level interconnect near via. Both the high
coefficient of thermal expansion and the low elastic modulus of the low-k dielectrics and barrier layer can decrease the highest hydrostatic stress on the top interface, which can improve the reliability
of the copper interconnects. 相似文献
395.
在<光明之城>中,雅各·德安科纳到达刺桐港时说到: 这是一个很大的港口,甚至比辛迦兰还大,商船从中国海进入到这里.它的周围高山环绕,那些高山使它成了一个逃避风暴的港口.它所在地的江水又广又宽,滔滔奔流入海,整个江面上充满了一艘艘令人惊奇的货船. 相似文献
396.
基于人工神经网络的故障诊断技术在船舶导航系统中的应用 总被引:1,自引:0,他引:1
应用对向传播神经网络对船舶导航系统的测姿故障进行检测与诊断,得到了较为满意的结果。研究表明,该网络结构简单,学习速度快,适应性广,可以对船舶导航系统的传感器故障进行检测与诊断。 相似文献
397.
Shili Wu Zhenmin Tang Zhaosong Guo 《International Journal of Automotive Technology》2017,18(3):365-375
Mixture faults detection is meaningful for gasoline engines because proper mixture is the basic prerequisite for healthy running of a combustion engine. Among existing methods for faults detection, the data-driven trend analysis technique is widely used due to the simplicity and efficiency in time-domain. The CUSUM (Cumulative Sum Of Errors) algorithm is good at real-time trend extraction, but it’s easy to be costly on the fuel trim signal during the engine in normal working conditions, which will increase battery energy consumption because engine failure is rarely occurs. Hence, the conventional treatment methods of artifacts in the CUSUM algorithm are modified by means of decay function and detection time analysis. The thresholds are tuned according to the characteristics of artifacts instead of residual variability, which leads to better results of trend extraction and less computation. Then, the revised CUSUM algorithm is used for monitoring the mixture abnormal behaviors, and the mixture faults can be detected in real time through analyzing the variation features of fuel trim signal. The lightweight faults detector using the advanced CUSUM algorithm (FD-A-CUSUM) is evaluated on the experimental data collected from a Ford engine. The validation results show that while engine works under normal conditions, the computation of FD-A-CUSUM has decreased by 72.79 % in comparison with the detection method using the original CUSUM algorithm (FD-O-CUSUM), and the false alarm ratio of FD-A-CUSUM is 3.37 %. Futhermore, the detection results of FD-A-CUSUM for two leakage faults have achieved 91.18 % test accuracy. 相似文献
398.
399.
400.
Han-Wool Lee Jin-Rae Cho Weui-Bong Jeong 《International Journal of Automotive Technology》2017,18(5):823-832
For the numerical simulation of tire rolling noise, an important subject is the extraction of normal velocity data of the tire surface that are essential for the acoustic analysis. In the current study, a concept of periodically exciting contact force is introduced to effectively extract the tire normal velocity data. The ground contact pressure within contact patch that is obtained by the static tire contact analysis is periodically applied to the whole tread surface of stationary tire. The periodically exciting contact forces are sequentially applied with a time delay corresponding to the tire rolling speed. The tire vibration is analyzed by the mode superposition in the frequency domain, and the acoustic analysis is performed by commercial BEM code. The proposed method is illustrated through the numerical experiment of 3-D smooth tire model and verified from the comparison with experiment, and furthermore the acoustical responses are investigated to the tire rolling speed. 相似文献