全文获取类型
收费全文 | 13301篇 |
免费 | 350篇 |
专业分类
公路运输 | 3216篇 |
综合类 | 3654篇 |
水路运输 | 3565篇 |
铁路运输 | 2521篇 |
综合运输 | 695篇 |
出版年
2025年 | 2篇 |
2024年 | 28篇 |
2023年 | 41篇 |
2022年 | 181篇 |
2021年 | 340篇 |
2020年 | 280篇 |
2019年 | 107篇 |
2018年 | 419篇 |
2017年 | 362篇 |
2016年 | 392篇 |
2015年 | 282篇 |
2014年 | 457篇 |
2013年 | 545篇 |
2012年 | 812篇 |
2011年 | 1089篇 |
2010年 | 1098篇 |
2009年 | 929篇 |
2008年 | 1090篇 |
2007年 | 1301篇 |
2006年 | 1209篇 |
2005年 | 823篇 |
2004年 | 279篇 |
2003年 | 225篇 |
2002年 | 176篇 |
2001年 | 215篇 |
2000年 | 229篇 |
1999年 | 127篇 |
1998年 | 103篇 |
1997年 | 83篇 |
1996年 | 100篇 |
1995年 | 63篇 |
1994年 | 64篇 |
1993年 | 39篇 |
1992年 | 41篇 |
1991年 | 32篇 |
1990年 | 31篇 |
1989年 | 20篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 4篇 |
1984年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
溃坝问题的数值仿真和实验 总被引:1,自引:0,他引:1
In this paper, two novel numerical computation methods are introduced which have been recently developed at Research Institute for Applied Mechanics ( RIAM ), Kyushu University, for strongly nonlinear wave-body interaction problems, such as ship motions in rough seas and resulting green-water impact on deck. The first method is the CIP-based Cartesian grid method, in which the free surface flow is treated as a multi-phase flow which is solved using a Cartesian grid. The second method is the MPS method, which is a so-called particle method and hence no grid is used. The features and calculation procedures of these numerical methods are described. One validation computation against a newly conducted experiment on a dam break problem, which is also described in this paper, is presented. 相似文献
993.
In the present paper, a new trimaran Pure Car Carrier (PCC) is proposed and a feasibility study on the ship is carried out. In this study, first, the effective horse power (EHP)/car of the PCC running in still water is predicted. By comparing the predicted EHP/car with that of a conventional mono-hull PCC, it is found that the trimaran PCC is superior to the conventional mono-hull PCC at rather higher speed. As ship speed increases, the reduction of the resistance of the trimaran is bigger. It is also found that at common service speed of PCCs, the EHP/car of a small PCC is lower than that of a conventional PCC. Secondly, the optimal L/B of a main-hull of the trimaran PCC in still water is determined. The optimal L/B of the main-hull varies with ship speed and size because the wave resistance decreases but the frictional resistance increases as L/B of the hull increases. As ship size increases, the optimal L/B of the main-hull of the trimaran PCC decreases. 相似文献
994.
Ships which have large structures above water surface, such as pure car carriers (PCCs) and container vessels, have large speed reduction by wind pressure. In the present study, the running speed of a large PCC with two or more sails for using wind power is simulated. The simulated results demonstrate that the ship can keep a constant service speed even in winds of 20m/s except head and bow winds. This sail system can shorten annual average navigation time by about 4 hours per voyage. 相似文献
995.
深水SPAR平台截断技术研究 总被引:1,自引:0,他引:1
To solve the dimensional limitations of physical models in tests, an equivalent water depth truncated design for a classical SPAR working in 913 m water was investigated. The water depth was reduced to 736m and then to 552m. As this was done, the mooring line lengths, EA value, and mass per meter were adjusted. Truncation rules and formulas for parameters and truncation factors were proposed. SPAR static characteristics were made to be consistent with those at full water depth. Then further time-domain coupled analysis was carried out for the SPAR when the mooring system experienced waves. The mooring lines were simulated by quasi-static method. Global responses and mooring line forces were found to agree well with test results for a prototype at that water depth. The truncation method proved to be robust and reliable. 相似文献
996.
实际海浪环境大尺度模型试验遥控遥测系统 总被引:1,自引:0,他引:1
Physical testing of large-scale ship models at sea is a new experimental method. It is a cheap and reliable way to research the environment adaptability of a ship in complex and extreme wave conditions. It is necessary to have a stable experimental system for the test. Since the experimental area is large, a remote control system and a telemetry system are essential, and were designed by the authors. An experiment was conducted on the Songhuajiang River to test the systems. The relationship between the model’s speed and its electromotor’s revolutions was also measured during the model test. The results showed that the two systems make it possible to carry out large-scale model tests at sea. 相似文献
997.
Sandwich plate systems (SPS) are advanced materials that have begun to receive extensive attention in naval architecture and ocean engineering. At present, according to the rules of classification societies, a mixture of shell and solid elements are required to simulate an SPS. Based on the principle of stiffness decomposition, a new numerical simulation method for shell elements was proposed. In accordance with the principle of stiffness decomposition, the total stiffness can be decomposed into the bending stiffness and shear stiffness. Displacement and stress response related to bending stiffness was calculated with the laminated shell element. Displacement and stress response due to shear was calculated by use of a computational code write by FORTRAN language. Then the total displacement and stress response for the SPS was obtained by adding together these two parts of total displacement and stress. Finally, a rectangular SPS plate and a double-bottom structure were used for a simulation. The results show that the deflection simulated by the elements proposed in the paper is larger than the same simulated by solid elements and the analytical solution according to Hoff theory and approximate to the same simulated by the mixture of shell-solid elements, and the stress simulated by the elements proposed in the paper is approximate to the other simulating methods. So compared with calculations based on a mixture of shell and solid elements, the numerical simulation method given in the paper is more efficient and easier to do. 相似文献
998.
999.
1000.