全文获取类型
收费全文 | 3539篇 |
免费 | 15篇 |
专业分类
公路运输 | 740篇 |
综合类 | 792篇 |
水路运输 | 1154篇 |
铁路运输 | 92篇 |
综合运输 | 776篇 |
出版年
2023年 | 4篇 |
2022年 | 24篇 |
2021年 | 28篇 |
2020年 | 18篇 |
2019年 | 14篇 |
2018年 | 366篇 |
2017年 | 326篇 |
2016年 | 314篇 |
2015年 | 33篇 |
2014年 | 67篇 |
2013年 | 235篇 |
2012年 | 152篇 |
2011年 | 294篇 |
2010年 | 289篇 |
2009年 | 144篇 |
2008年 | 265篇 |
2007年 | 199篇 |
2006年 | 65篇 |
2005年 | 107篇 |
2004年 | 65篇 |
2003年 | 84篇 |
2002年 | 52篇 |
2001年 | 26篇 |
2000年 | 35篇 |
1999年 | 23篇 |
1998年 | 27篇 |
1997年 | 26篇 |
1996年 | 25篇 |
1995年 | 41篇 |
1994年 | 9篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 9篇 |
1989年 | 4篇 |
1988年 | 6篇 |
1987年 | 10篇 |
1986年 | 9篇 |
1985年 | 8篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 7篇 |
1980年 | 12篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 6篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1972年 | 4篇 |
排序方式: 共有3554条查询结果,搜索用时 15 毫秒
101.
李发根 《上海交通大学学报(英文版)》2008,13(6):679-683
We show that the Zhang-Yang-Zhu-Zhang identity-based authenticatable ring signcryption scheme is not secure against chosen plaintext attacks.Furthermore, we propose an improved scheme that remedies the weakness of the Zhang-Yang-Zhu-Zhang scheme.The improved scheme has shorter ciphertext size than the Zhang-Yang-Zhu-Zhang scheme.We then prove that the improved scheme satisfies confidentiality, unforgeability, anonymity and authenticatability. 相似文献
102.
Multi-stand roll forming is a process that has very complicated deformation behaviour and shows significant nonlinearity.In this paper, the sensitivity analysis of parameters for multi-stand roll forming was performed via a new booting finite element method(FEM) model.Compared with the most of simulation, the new model is more consistent with production process and can account for the effects of roll rotating speed.Based on the model, the process of an open section channel formed with 10 passes was simulated and the sensitivity analysis was conducted with orthogonal experiment design combined FEM model.The multi-stand roll forming process can be efficiently analyzed by the new booting model.And sensitivity analysis shows the hardening exponent plays an important role in controlling the quality of the products. 相似文献
103.
The parameter values which actually change with the circumstances, weather and load level etc.produce great effect to the result of state estimation. A new parameter estimation method based on data mining technology was proposed. The clustering method was used to classify the historical data in supervisory control and data acquisition (SCADA) database as several types. The data processing technology was impliedto treat the isolated point, missing data and yawp data in samples for classified groups. The measurement data which belong to each classification were introduced to the linear regression equation in order to gain the regression coefficient and actual parameters by the least square method. A practical system demonstrates the high correctness, reliability and strong practicability of the proposed method. 相似文献
104.
105.
阐述甘泉铁路车站分布和运量发展情况及货运量增加后区间通过能力不足的问题,介绍甘泉铁路行车组织和区间通过能力计算方法,计算各区间的通过能力,结合近期货物运量500万t、700万t、1000万t三种情况,计算需求通过能力,并给出提高通过能力的具体方案,为下一步货运量的增加做准备。 相似文献
106.
107.
108.
使用有限元分析以改善重载运输车轴 总被引:1,自引:0,他引:1
分析了北美铁路货运发生的车轴故障,介绍了使用有限元对F级和K级车轴进行应力分析计算,研究车轴尺寸变化对应力的影响,并提出了改善重载车轴设计的建议. 相似文献
109.
LIU He-ping LUO A-ni MENG Qing-xin 《船舶与海洋工程学报》2007,6(1):58-62
The virtual prototype technology is applied to the design of the hydraulic impingement shovel, which is to increase the reliability of the design. The work principle of hydraulic impingement shovel is expatiated, and its dynamic equations are established. The 3D model of virtual prototype is built by PRO/E. Then the couple between the mechanical body of prototype and the hydraulic system is completed by virtue of ADAMS. Finally, the simulation is made on the virtual prototype. The simulation results show that the design of underwater hydraulic impingement shovel is rational. The virtual prototype technology could lay sound foundation of successful manufacturing of physical prototype for the first time and offer highly effective and feasible means for the design and production of underwater equipments. 相似文献
110.
ZHUANG Yuan LIU Zu-yuan 《船舶与海洋工程学报》2007,6(1):53-57
At present, the method of calculating the turbulent flow width around the bridge pier is not given in the "Standard for Inland River Navigation" (GB50139-2004) in China, and the bridge designer usually increases the bridge span in order to ensure the navigation safety, which increases both of the structural design difficulty and the project investments. Therefore, it is extremely essential to give a research on the turbulent flow width around the bridge pier. Through the experiments of the fixed bed and the mobile bed, the factors influencing the turbulent flow width around the bridge pier have been analyzed, such as the approaching flow speed, the water depth, the angles between the bridge pier and the flow direction, the sizes of bridge pier, the shapes of the bridge pier, and the scouring around the bridge pier, etc. Through applying the dimension analytic method to the measured data, the formula of calculating the turbulent flow width around the bridge pier is then inferred. 相似文献