全文获取类型
收费全文 | 10728篇 |
免费 | 315篇 |
专业分类
公路运输 | 2646篇 |
综合类 | 3085篇 |
水路运输 | 2988篇 |
铁路运输 | 1635篇 |
综合运输 | 689篇 |
出版年
2024年 | 22篇 |
2023年 | 34篇 |
2022年 | 205篇 |
2021年 | 340篇 |
2020年 | 260篇 |
2019年 | 106篇 |
2018年 | 436篇 |
2017年 | 390篇 |
2016年 | 415篇 |
2015年 | 287篇 |
2014年 | 420篇 |
2013年 | 536篇 |
2012年 | 607篇 |
2011年 | 884篇 |
2010年 | 874篇 |
2009年 | 822篇 |
2008年 | 878篇 |
2007年 | 930篇 |
2006年 | 803篇 |
2005年 | 567篇 |
2004年 | 217篇 |
2003年 | 195篇 |
2002年 | 114篇 |
2001年 | 157篇 |
2000年 | 140篇 |
1999年 | 68篇 |
1998年 | 60篇 |
1997年 | 40篇 |
1996年 | 56篇 |
1995年 | 43篇 |
1994年 | 42篇 |
1993年 | 16篇 |
1992年 | 20篇 |
1991年 | 18篇 |
1990年 | 14篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 828 毫秒
941.
Cross‐border passengers from Hong Kong to Shenzhen by the east Kowloon‐Canton Railway (KCR) through the Lo Wu customs exceed nearly 200 thousand on a special day such as a day during the Chinese Spring Festival. Such heavy passenger demand often exceeds the processing and holding capacity of the Lo Wu customs for many hours a day. Thus, passengers must be metered off at all entrance stations along the KCR line through ticket rationing to restrain the number of passengers waiting at Lo Wu within its safe holding capacity. This paper proposes an optimal control strategy and model to deal with this passenger crowding and control problem. Because the maximum passenger checkout rate at Lo Wu is fixed, total passenger waiting time is not affected by the control strategy for given time‐dependent arriving rates at each station. An equity‐based control strategy is thus proposed to equalize the waiting times of passengers arriving at all stations at the same time. This equity is achieved through optimal allocation of the total quota of tickets to all entrance stations for each train service. The total ticket quota for each train service is determined such that the capacity constraint of the passenger queue at Lo Wu is satisfied. The control problem is formulated as a successive linear programming problem and demonstrated for the KCR system with partially simulated data. 相似文献
942.
FU Ming-Yu BIAN Xin-Qian SHI JiCollege of Power Nuclear Engineering Harbin Engineering University Harbin China 《船舶与海洋工程学报》2002,1(1):41-46
All kinds of reasons are analysed in theory and a fault repository combined with local expert experiences is establishedaccording to the structure and the operation characteristic of steam generator in this paper. At the same time, Kohonen algo-rithm is used for fault diagnoses system based on fuzzy neural networks. Fuzzy arithmetic is inducted into neural networks tosolve uncertain diagnosis induced by uncertain knowledge. According to its self-association in the course of default diagnosis. thesystem is provided with non-supervise, self-organizing, self-learning, and has strong cluster ability and fast cluster velocity. 相似文献
943.
RENHui-long ZHANGHai-bin DAIYu-zhi SONGJing-zheng 《船舶与海洋工程学报》2003,2(1):1-10
A three-dimensional method of calculating wave loads of turret moored FPSO (Floating Production Storage and Offloading) tankers is presented. The linearized restoring forces acting on the ship hull by the mooring system are calculated according to the catenary theory, which are expressed as the function of linear stiffness coefficients and the displacements of the upper ends of mooring chains. The hydrodynamic coefficients of the ship are calculated by the three-dimensional potential flow theory of the linear hydrodynamic problem for ships with a low forward speed. The equations of ship motions are established with the effect of the restoring forces from the mooring system included as linear stiffness coefficients. The equations of motions are solved in frequency domain, and the responses of wave-induced motions and loads on the ship can be obtained. A computer program based on this method has been developed, and some calculation examples are illustrated. Analysis results show that the method can give satisfying prediction of wave loads. 相似文献
944.
运用产业组织理论对铁路现状进行分析,从政企分开、放松管制、调整产品结构、实现产品差别化、多元化融通资金以及引进国外先进技术和管理机制、发挥后发优势等方面提出铁路必须引入竞争机制才能有所发展、有所创新,才能能力面对我国入世后的挑战。 相似文献
945.
LI Qing-fen WANG Peng REN Zheng-yi and LONG Ping School of Mechanical & Electrical Engineering Harbin Engineering University Harbin China 《船舶与海洋工程学报》2003,2(2):1-4
In this paper, the effect of plastic constraint on the initiation of ductile tears in four different shipbuilding structural steels has been experimentally studied by measuring the J-integral and crack opening displacement COD at initiation in three-point bend specimens with deep and shallow notches. Experimental results of seven groups of different strength alloy steels show that both Si and Ji values of ductile tear from the shallow crack specimens which have less constraint flow field are significantly higher than those of deeply notched specimens. Slip-line-field analysis shows that, for shallow crack, the hydrostatic stress is lower than that from standard deeply cracked bend specimen, which develops a high level of crack tip constraint, provides a lower bound estimate of toughness, and will ensure an unduly conservative approach when applied to structural defects, especially if initiation values of COD and J-integral are used. 相似文献
946.
947.
航海院校对海员职业适应能力的培养途径 总被引:1,自引:0,他引:1
根据海员职业具有动荡性、风险性、艰苦性、独立性和变化性的特点。以及海员在海上工作生活的环境条件,提出航海院校在航海教育过程中应注重海员职业适应能力的培养,并提出几种培养的途径。 相似文献
948.
LIU Ya-dong LI Ji-de LI ZhenCollege of Shipbuilding Engineering Harbin Engineering University Harbin China 《船舶与海洋工程学报》2002,1(2):6-11
In this paper a 3-D panoramic simulation system of a ship is described which is developed with the MAXSCRTPT language and VC + + as programming tools on the platform of 3 Dsmax. The strip theory method is applied to the motion prediction of the mono-hull. The time history solutions of heave and pitch are obtained in the condition of head sea to provide the primary data on panoramic simulation. The simulation system has following functions: 1) digital simulation; 2 ) panoramic simulation; 3) environmental set-up; 4) render preview and output. 相似文献
949.
Bernhard Berking 《WMU Journal of Maritime Affairs》2003,2(1):61-78
The Universal Automatic Identification System (AIS) provides a huge variety of potential applications and services which exceed
the well known ship-to-ship data exchange. The purpose of this paper is to address the most important AIS services, in particular
the AIS position report and the AIS safety-related and binary messages (“AIS telegrams”). The main issue is the impact of
this new technology on the on-board use of AIS in collision avoidance (and its limitations) as well as the impact on shore-based
services such as Vessel Traffic Service (VTS), port management and the need of an effective AIS network. 相似文献
950.