全文获取类型
收费全文 | 827篇 |
免费 | 16篇 |
专业分类
公路运输 | 266篇 |
综合类 | 223篇 |
水路运输 | 171篇 |
铁路运输 | 149篇 |
综合运输 | 34篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 15篇 |
2021年 | 20篇 |
2020年 | 20篇 |
2019年 | 9篇 |
2018年 | 10篇 |
2017年 | 2篇 |
2016年 | 16篇 |
2015年 | 24篇 |
2014年 | 21篇 |
2013年 | 41篇 |
2012年 | 50篇 |
2011年 | 53篇 |
2010年 | 61篇 |
2009年 | 64篇 |
2008年 | 74篇 |
2007年 | 77篇 |
2006年 | 89篇 |
2005年 | 63篇 |
2004年 | 26篇 |
2003年 | 15篇 |
2002年 | 18篇 |
2001年 | 15篇 |
2000年 | 14篇 |
1999年 | 11篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 6篇 |
1994年 | 8篇 |
1993年 | 1篇 |
1991年 | 3篇 |
1989年 | 3篇 |
1984年 | 2篇 |
排序方式: 共有843条查询结果,搜索用时 843 毫秒
21.
柴油机主轴颈与主轴承电化学腐蚀产生原因 总被引:2,自引:0,他引:2
主要分析并介绍了船用主柴油机轴系产生电化学腐蚀的原因和控制措施。 相似文献
22.
23.
24.
More and more multiple-track tunnels and super-large section tunnels have been built, and disman- tling of temporary strut is a weak point of the whole structure during force transfer when the secondary lining is con- structed. It is significant to guarantee structure safety during dismantling of temporary strut. Little systematic re- search on safety in dismantling of temporary strut of the super-large section tunnel with double-layer primary support has been conducted, so the internal force and security of the two-layer primary support of the Xinkaotang tunnel were analyzed by a numerical analysis and site measurement, and it proves the effect of two-layer primary support on the safety during strut dismantling. The research results indicate that: (1) with constant support thickness and one-time longitudinal dismantling length, the safety factor of secondary primary support is larger than that of the first primary support, and the safety factor of the first primary support is larger than that of the single-layer primary support. Change range of safety factor for the first primary support is smaller than that of the single-layer primary support, and the safe factor for the single-layer primary support is smaller than that of the secondary primary support; (2) with the same support pattern, the safety factors increase firstly and then decrease with an increase of the onetime dismantling length. The calculated results of various cases show that the reasonable one-time dismantling length for this project is about 9 m. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
25.
In this paper the numerical simulation analysis of the effect of explosion in the gas pipeline compartment of a utility tunnel on neighboring metro tunnels was conducted using the software AUTODYN. The results show that the TNT equivalent in a fireproof partition with length of 200 m is 41.6 kg when the gas concentration in the gas pipeline compartment reaches 10%; the blast wave has much effect on the crown and arch waist of the round metro tunnel and it’s necessary to take some protective measures in both areas; when the surrounding soil is sand, the utili- ty tunnel is above the round metro tunnel and their alignments are in the same direction, the greater the vertical spacing between the utility tunnel and the metro tunnel, the smaller the effect of the blast wave on the metro tunnel; when the vertical spacing is 7.2 m, the maximum dynamic tensile stress is 1.86 MPa (including the static stress value of 1 MPa in the tunnel segment) and it is slightly smaller than the designed tensile strength of metro tunnel (about 1.89 MPa). The maximum vibration velocity and the maximum displacement meet the structural stability require- ments, so it is suggested the vertical spacing between the utility tunnel and metro tunnel shall not be less than 7.2 m. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
26.
Defects of tunnel lining, such as inadequate thickness, voids, cracks, rock falling and water leakage etc., endanger the safety of railway tunnel operation. Based on the site construction, an analysis of the reasons for lining defects was conducted; technical measures against lining defects were proposed and tests were carried out at site. The results show that these measures are reliable and effective, and the purposes of prevention and treatment are re⁃ alized. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
27.
28.
29.
该文介绍了312国道常州段新武宜运河大桥不对称边跨预应力混凝土连续箱梁施工监控的关键技术,论述了施工监控的目的与意义,阐明了线形控制及应力监测的要求、技术措施等。 相似文献
30.
AMT(Automated dMechanical Transmission,即电控机械式自动变速器)的执行机构广泛采用液压系统,包括蓄能器、电磁阀、管路、选换挡液压缸和离合器操纵液压缸。为了缩短换挡时间,提高换挡品质,对液压系统的流量有一定的要求,尤其是载质量大的车辆,对流量有更高的要求,为了提高液压系统的流量,同时照顾系统的小型轻量化,运用功率键合图方法,首次对AMT液压系统建立了完善的高阶时变非线性状态方程,通过仿真实验,得到了许多有意义的结论,实车应用后,明显提高了换挡速度,从而大大缩短了液压系统的开发周期。 相似文献