全文获取类型
收费全文 | 8188篇 |
免费 | 664篇 |
专业分类
公路运输 | 2335篇 |
综合类 | 2494篇 |
水路运输 | 2291篇 |
铁路运输 | 1513篇 |
综合运输 | 219篇 |
出版年
2024年 | 38篇 |
2023年 | 97篇 |
2022年 | 364篇 |
2021年 | 500篇 |
2020年 | 335篇 |
2019年 | 187篇 |
2018年 | 190篇 |
2017年 | 170篇 |
2016年 | 167篇 |
2015年 | 288篇 |
2014年 | 418篇 |
2013年 | 510篇 |
2012年 | 603篇 |
2011年 | 647篇 |
2010年 | 637篇 |
2009年 | 628篇 |
2008年 | 599篇 |
2007年 | 626篇 |
2006年 | 620篇 |
2005年 | 552篇 |
2004年 | 204篇 |
2003年 | 118篇 |
2002年 | 70篇 |
2001年 | 109篇 |
2000年 | 120篇 |
1999年 | 19篇 |
1998年 | 8篇 |
1997年 | 6篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 6篇 |
1993年 | 1篇 |
1992年 | 2篇 |
1991年 | 2篇 |
排序方式: 共有8852条查询结果,搜索用时 0 毫秒
831.
832.
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
833.
Acoustic vector sensor consists of pressure and particle velocity sensors,which measure the three-dimensional acoustic particle velocity,as well as the pressure at one location at the same time.By preserving the amplitude and phase information of the pressure and particle velocity,they possess a number of advantages over traditional scalar sensors.Signal-to-noise ratio (SNR) gain (which is often called array gain) is one of such advantages and is always interested by all of us.But it is not unchangeable if the spatial correlation of the noise field varies.Much more important,it is difficult to be given if the noise becomes complex.In this paper,spatial correlation of the vector field of isotropic volume-noise and surface-generated noise has been introduced briefly.Based on the results,the combined SNR output of a vector linear array is investigated and the maximum gain is given in the specified noise.Computer simulation shows that the output of one array in the same noise is not the same in different gestures.And then we find the best gesture through SNR calculation and obtain the biggest gain,which has important meaning to guide how to deploy an array in practice.We also should use the array with respect to the characteristics of the real ambient noise,especially in anisotropic noise field. 相似文献
834.
针对岷江彭山江口—乐山段原规划梯级方案间距近、电站动能经济指标差、开发难度大的问题,以全面实现岷江航道达标升级为目标,结合规划建设条件的变化情况,全面分析优化方案在通航、发电效益、环境影响等方面存在的问题和效果,得出了将岷江彭山江口—乐山段梯级开发由8级优化为6级的优化方案。优化方案为《岷江成都至乐山段航运发展规划》编制提供技术支撑,显著提升了航运效益、发电效益和水环境效益,极大提高了开发方案的可实施性,为岷江高等级航道的建设奠定了坚实的理论基础和规划指引。 相似文献
835.
大跨径预应力混凝土连续刚构桥的现状和发展趋势 总被引:54,自引:0,他引:54
阐述了连续刚构桥是大跨径梁桥发展的必然趋势,以及要解决的防止过大温度应力及防止船撞的措施;收集和分析了国内外大跨径连续刚构桥的数据和资料,论述了上部构造轻型化和取消落地支架合拢边跨等趋势。 相似文献
836.
837.
838.
839.
840.