全文获取类型
收费全文 | 4862篇 |
免费 | 2055篇 |
专业分类
公路运输 | 317篇 |
综合类 | 1054篇 |
水路运输 | 5297篇 |
铁路运输 | 234篇 |
综合运输 | 15篇 |
出版年
2022年 | 95篇 |
2021年 | 4篇 |
2020年 | 396篇 |
2019年 | 793篇 |
2018年 | 644篇 |
2017年 | 622篇 |
2016年 | 606篇 |
2015年 | 717篇 |
2014年 | 530篇 |
2013年 | 760篇 |
2012年 | 472篇 |
2011年 | 78篇 |
2010年 | 13篇 |
2009年 | 8篇 |
2008年 | 176篇 |
2007年 | 31篇 |
2006年 | 17篇 |
2005年 | 89篇 |
2004年 | 192篇 |
2003年 | 176篇 |
2002年 | 124篇 |
2001年 | 93篇 |
2000年 | 64篇 |
1999年 | 13篇 |
1998年 | 12篇 |
1997年 | 5篇 |
1996年 | 18篇 |
1995年 | 4篇 |
1994年 | 26篇 |
1993年 | 47篇 |
1992年 | 19篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1986年 | 23篇 |
1985年 | 17篇 |
1984年 | 17篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有6917条查询结果,搜索用时 15 毫秒
151.
152.
153.
154.
155.
156.
157.
158.
159.
LI Tie-shan YAN Shu-jia and QIAO Wen-ming . School of Naval Architecture Ocean Civil Engineering Shanghai Jiao Tong University Shanghai China . Navigation College Dalian Maritime University Dalian China . Navigation School Shandong Jiaotong College Weihai China 《船舶与海洋工程学报》2007,6(4)
This paper focuses on the problem of linear track keeping for marine surface vessels. The influence exerted by sea currents on the kinematic equation of ships is considered first. The input-to-state stability(ISS) theory used to verify the system is input-to-state stable. Combining the Nussbaum gain with backstepping techniques,a robust adaptive fuzzy algorithm is presented by employing fuzzy systems as an approximator for unknown nonlinearities in the system. It is proved that the proposed algorithm that guarantees all signals in the closed-loop system are ultimately bounded. Consequently,a ship's linear track-keeping control can be implemented. Simulation results using Dalian Maritime University's ocean-going training ship 'YULONG' are presented to validate the effectiveness of the proposed algorithm. 相似文献
160.
KONG Qiao-ling MA Jie State Key Laboratory of Ocean Engineering Shanghai Jiaotong University Shanghai China 《船舶与海洋工程学报》2007,6(4)
The phase change characteristic of the power source of an underwater glider propelled by the ocean's thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process,but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees,the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change,and the slope of the temperature time history curve remains the same. However,the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size,boundary conditions,and the power source's cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38mm needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems. 相似文献