全文获取类型
收费全文 | 2387篇 |
免费 | 22篇 |
专业分类
公路运输 | 328篇 |
综合类 | 798篇 |
水路运输 | 786篇 |
铁路运输 | 124篇 |
综合运输 | 373篇 |
出版年
2024年 | 1篇 |
2023年 | 1篇 |
2022年 | 7篇 |
2021年 | 17篇 |
2020年 | 20篇 |
2019年 | 2篇 |
2018年 | 339篇 |
2017年 | 293篇 |
2016年 | 254篇 |
2015年 | 17篇 |
2014年 | 20篇 |
2013年 | 25篇 |
2012年 | 83篇 |
2011年 | 238篇 |
2010年 | 255篇 |
2009年 | 100篇 |
2008年 | 211篇 |
2007年 | 179篇 |
2006年 | 64篇 |
2005年 | 91篇 |
2004年 | 46篇 |
2003年 | 62篇 |
2002年 | 36篇 |
2001年 | 10篇 |
2000年 | 14篇 |
1999年 | 2篇 |
1998年 | 6篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1984年 | 2篇 |
排序方式: 共有2409条查询结果,搜索用时 375 毫秒
791.
通过在乐善闸桥改建工程中使用轻集料混凝土的理论和试验分析,验证了轻集料混凝土的技术性能,并通过经济分析验证了在中小型桥梁中应用轻集料混凝土的可行性.进一步推广了轻集料混凝土的使用。 相似文献
792.
Adopting an elastic-viscoplastic, the asymptotic problem of mode I propagating crack-tip field is investigated. Various asymptotic
solutions resulting from the analysis of crack growing programs are presented. The analysis results show that the quasistatically
growing crack solutions are the special case of the dynamic propagating solutions. Therefore these two asymptotic solutions
can be unified. 相似文献
793.
794.
他生于1970年,年仅35岁已是我国航运业小有名气的船长;他才能出众,曾以过硬的技术赢得外国船东的赏识,在30万吨级VLCC上成就了个人船长生涯的第一次;他战绩彪炳,短短5年的船长经历,不仅填补了我国VLCC航海史的空白,而且走出了一条中国海员自己管理、操纵VLCC的先驱者之路;他百尺竿头更进一步,如今转战5688TEU大型集装箱船,继续航海人生的辉煌征程……他,就是中海集团上海船员公司的一名年轻船长——李广红。 相似文献
795.
LI Qing-fen ZHENG Wei SHU Hai-sheng 《船舶与海洋工程学报》2005,4(3):1-4
In part I and II of this series, experimental investigation in both EPFM and LEFM had been discussed. In this part, further theoretical analysis is given. The theoretical development of Two Parameter Fracture Mechanics by Hancock etc, has rationalized our experimental results. This method can be applied to engineering practice, and will allow the advantage of enhanced toughness for specimens with low levels of constraint to be taken into account for defect assessment. 相似文献
796.
为满足变电站提出的高电压、大容量谐波抑制,兼具一定容量无功静补的工程要求,研制出一种新型注入式混合有源滤波器.详细介绍了混合有源滤波器各个组成部分的设计方法及工程应用中的注意事项,并给出了实验室验证结果和工程应用效果.实际工程应用效果表明其具有良好的应用前景. 相似文献
797.
798.
Anouck R. Girard Daniel M. Empey William C. Webster J. Karl Hedrick 《Journal of Marine Science and Technology》2003,7(3):109-118
The concept of a mobile offshore base (MOB) reflects the need to stage and support military and humanitarian operations anywhere
in the world. A MOB is a self-propelled, modular, floating platform that can be assembled into lengths of up to 2 km, as required,
to provide logistic support to US military operations where fixed bases are not available or adequate. It accommodates the
take-off and landing of C17 aircraft, and can be used for storage, as well as to send resources quickly to shore. In most
concepts, the structure is made of three to five modules, which have to perform long-term station-keeping in the presence
of winds, waves, and currents. This is usually referred to as dynamic positioning (DP). In the MOB, the alignment is maintained
through the use of thrusters, connectors, or a combination of both. In this paper, we consider the real-time control of scaled
models of a MOB. The modules are built at the 1 : 150 scale, and are kept aligned by rotating thrusters under a hierarchical
hybrid control scheme. This paper describes a physical testbed developed at the University of California, Berkeley, under
a grant from the US Office of Naval Research, for the purpose of evaluating competing MOB control concepts.
Received: June 4, 2002 / Accepted: October 30, 2002
Acknowledgments. This material is based on work supported by the MOB Program of the US Office of Naval Research under grant N00014-98-1-0744.
The authors would like to thank the Link Foundation for its support. Many thanks go to Stephen Spry for his experimental work.
The photographs are courtesy of Bill Stone, Gerald Stone, and Jay Sullivan of the PATH Publications staff.
Address correspondence to: A.R. Girard (e-mail: anouck@eecs.berkeley.edu) 相似文献
799.
A ship operating in following and/or quartering seas may be susceptible to broaching-to preceded by the surf-riding phenomenon. Therefore, for the safety assessment of fast vessels such as destroyers and patrol craft, the estimation of the surf-riding condition is important. As shown by previous research, there are two boundaries for ship motion in following and quartering seas. These are the surf-riding threshold and wave-blocking threshold. In this study, the theoretical methods to estimate both boundaries are obtained by making use of Melnikov’s method. In order to validate the formulae, free-running model experiments are conducted in the towing tank. Comparisons between the results obtained from calculations and experiments show good agreement. It is concluded that the formulae based on Melnikov’s method could be applicable to the safety assessment of surface ships. 相似文献
800.
Roozbeh Panahi Mehdi Shafieefar Ali Ghasemi 《Journal of Marine Science and Technology》2016,21(1):167-178
This study aims at presenting a new approach in calibrating standard two-peak design spectra for specific regions in absence of wind data. The main principle in these kinds of fitting for a new area is to minimize the least square error between measured and fitted spectra and there has been less attention to double-peak spectra individual characteristic as co-existence of wind-sea and swell parts in one spectrum. Here, separation frequency, approximately dividing such parts, is implemented to virtually extract wind-sea and swell components of a measured spectrum considering their intrinsic overlap near the separation frequency. Then, they have been easily utilized to calibrate two parts of standard double-peak spectrum in a revisory manner. To verify benefits of this new methodology, it has been applied on Ochi-Hubble as well as Torsethaugen spectra regarding field measurements in a coastal region at Gulf of Oman, Chabahar bay. Results obviously show a better adjustment of formula to field spectrum using this simple approach when compared with output of calibration on integrated field spectrum irrespective of its main characteristic such as availability of two-wave systems. 相似文献