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71.
近岸波浪变形数值模型的比较研究 总被引:2,自引:1,他引:1
外海深水区的波浪传播到近岸浅水区时,受到岛屿、地形与建筑物等影响,发生折射、绕射、反射和破碎等一系列变形。准确计算近岸与港内波浪分布,成为港口与海岸工程研究的重要课题。文章在总结波浪数值模拟发展现状的基础上,对目前常用的基于椭圆型缓坡方程的CGWAVE模型、基于Boussinesq方程的MIKE21-BW模型和基于动谱平衡方程的SWAN模型进行了比较研究。 相似文献
72.
斜拉索断裂对斜拉桥动力性能的影响研究 总被引:1,自引:0,他引:1
斜拉索断裂后必然会对斜拉桥动力性能产生一定的影响,进而影响到桥梁的通载能力。利用有限元方法针对长江某大型斜拉桥进行数值分析建模,考虑了各种非线性影响因素,对模型施加二期恒载后进行计算检验。验证模型合理性后,针对斜拉索不同断裂位置和数量,对斜拉桥进行了动力性能分析。通过分析得出背索和跨中斜拉索断裂对全桥动力性能影响较大和竖向振型受斜拉索断裂影响较大的结论,可为斜拉桥应急抢修技术方案的制定和平时桥梁的健康监测提供理论依据。 相似文献
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When a ship with a wide, immersed transom stern runs on a deep draft, forward-oriented wave breaking often occurs just behind
the transom stern. In such conditions, stern waves can be considered to consist of two main components: the forward-oriented
breaking wave and the remaining following waves. In our previous study, which was the first part of the present study, we
developed a method to treat the forward-oriented breaking wave, and have clarified that it has a scale effect and its resistance
coefficient decreases with an increase in the size of the model ship. On the other hand, the study also indicated that the
height of the remaining following waves increases with an increase in the model ship size. The purpose of this paper is a
more complete understanding of the two different component characteristics of the stern waves. We have developed a method
to estimate the resistance due to the remaining following waves. Using this method, we have reached three main conclusions.
The resistance increases considerably if the remaining following waves change to forward-oriented breaking waves. The resistance
coefficient of the remaining following waves increases only slightly with an increase in model ship size. This stern wave
resistance coefficient is strongly affected by the forward-oriented breaking waves, and therefore decreases with an increase
in model ship size.
Received: January 5, 2001 / Accepted: May 28, 2001 相似文献
75.
为研究长江航道环境敏感区高频破碎锤水下破礁特征,采用理论分析和数值模拟方法,分析高频破碎锤冲击作用下礁石的损伤特性及影响规律。结果表明,冲击钎杆周边岩体以剪切破坏为主,远离钎杆处岩体则以拉破坏为主。凿入深度、破碎深度及破碎宽度随工作压力与冲击频率的增大而增大,随礁石强度的增大而减小,高频破碎锤不宜破碎强度太高的礁石;大于临界冲击频率时,破碎参数改善不显著。工作压力是影响高频破碎锤破礁效果的主控因素,其次是冲击频率,最后是礁石强度。建立了钎杆凿入深度与岩体破碎体积的数学关系,提出了高频破碎锤破礁工效计算方法。研究成果对优化高频破碎锤破礁参数、提高破礁效率具有参考价值。 相似文献
76.
船用直流固态开断装置中所使用的大功率IGBT需要考虑其散热问题,IGBT器件的散热设计中导热硅脂涂覆和IGBT的安装工艺散热效果起着非常关键的作用,直接影响IGBT的长期可靠运行。本文针对导热硅脂涂敷各个环节因素开展对比验证,通过热仿真,提出导热硅脂涂覆和IGBT安装工艺的原则性意见。 相似文献
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79.
The incorporation of new international regulations is a rational way to avoid the use of substandard Asian ship-breaking yards. However, more restrictive regulations and agreements could lead to increase the proliferation of the use of third countries in connection with ship recycling industry. The new Open Registries provides ship-owners with legal loopholes in order to avoid strict national legislations and international rules, thus the “genuine link” disappears and the ship-owner’s responsibilities relax. Ship-breaking industry is a complex interconnected system with many important key actors, such as shipping companies, ship-owners, ship registries, brokers, and ship-breaking yards, all of which are discussed in this paper under the vision of a new global ship recycling policy, and focusing in those cases when a ship changes its flag state registration just before scrapping. This paper analyses the most common flags selected in order to send ships for scrapping. Empirical investigation to determine the relation between States and ship-breaking industry has been carried out using the multivariate statistic technic known as “Simple correspondence analysis”. The results show a relation between ship registry selection and ships that are about to end their lives, re-flagging solely for the purpose of scrapping. If we observe the evolution of the different flag states at the end of the ship’s life, we find incremented use of new open registers or “Mirror Flags”. General abuse of new registries in ship-breaking industry would lead to a ship-breaking industry without rules or transparent procedures, which could violate labour and environmental standards. 相似文献
80.
在近岸浅水波浪分布的研究中,格鲁霍夫斯基给出适用于深水波至破碎波的整个浅水域(相对水深η>2)的波高经验分布公式,但该式在波浪发生破碎后的适用性研究欠缺。基于FLOW-3D软件对深水不规则波传播到斜坡地形上波浪发生破碎进行模拟,验证波高沿程分布与试验值的一致性,并模拟在130斜坡地形条件下波浪从有限水深传播到近岸破碎区的沿程波高分布变化。结果表明,在该坡度相对水深η<2.75情况下,格鲁霍夫斯基经验分布公式出现较大误差,不再适用;破碎区各累积率波高与平均波高的比值随相对水深变小呈递减趋势,经验公式值与之相比,总体上呈现出大波偏大、小波偏小的情况。 相似文献