全文获取类型
收费全文 | 2081篇 |
免费 | 2篇 |
专业分类
公路运输 | 226篇 |
综合类 | 660篇 |
水路运输 | 724篇 |
铁路运输 | 5篇 |
综合运输 | 468篇 |
出版年
2025年 | 1篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 346篇 |
2017年 | 296篇 |
2016年 | 254篇 |
2015年 | 8篇 |
2014年 | 9篇 |
2013年 | 57篇 |
2012年 | 72篇 |
2011年 | 218篇 |
2010年 | 221篇 |
2009年 | 60篇 |
2008年 | 186篇 |
2007年 | 127篇 |
2006年 | 4篇 |
2005年 | 54篇 |
2004年 | 46篇 |
2003年 | 61篇 |
2002年 | 17篇 |
2001年 | 2篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 1篇 |
1991年 | 2篇 |
1990年 | 2篇 |
1985年 | 2篇 |
1973年 | 1篇 |
排序方式: 共有2083条查询结果,搜索用时 0 毫秒
661.
Riccardo Amirante Carlo Coratella Elia Distaso Gianluca Rossini Paolo Tamburrano 《International Journal of Automotive Technology》2017,18(4):729-742
Since the needle displacement exerts a fundamental influence on the operation of Common Rail injection systems, accurate measurements of the control piston position can be crucial for a more thorough analysis of the behaviour of injectors, in particular when multiple injections are employed. Eddy current sensors have traditionally been used in lab activities to measure the control piston position inside injectors; apart from the high cost, the scientific literature clearly shows their inadequacy, which is mainly due to the presence of electromagnetic disturbance: the current pulse, which controls the opening of the injector, generates electromagnetic fields which strongly affect the acquisition of data. Many attempts have recently been made either to solve the interference occurring during such measurements or to propose alternative displacement transducers whose operation is not influenced by electromagnetic interference. In this paper, a new device for measuring the injector opening is proposed: it is an optical transducer characterized both by simple and very cheap construction and by a reliable physical principle for measuring the control piston lift. The reliability of the proposed sensor is assessed by a thorough experimental campaign and by comparing the experimental results with the numerical predictions achieved by a Common Rail injector model. Since the assembly of the optical sensor does not affect the injector operation, it can efficiently be used both for experimental tests and for on-board diagnosis and monitoring of the injector operation. 相似文献
662.
Thomas A. Hamade 《上海交通大学学报(英文版)》2018,23(1):112-121
A novel high-voltage electrostatics corona ions pre-charger apparatus and methods were invented earlier by Hamade related to treat various types of receptors such as but not limited to electret polymer, air filters, particulates, catalytic converters, bioaerosols, fluids, pollutants, virus, and bacteria. It is shown in this article that his work led to the construction of various prototype chargers, customized differently for each type of a receptor. In particular his recent development of biological matter corona charger (BMCC) prototype related to expose, treat, sanitize, and disinfect bioaerosols, virus, bacteria, and contaminated fluids and blood such as human immunodeficiency virus (HIV) - acquired immune deficiency syndrome (AIDS). It is shown in this paper that each previous investigated research contemplated ionized corona charger attendant to a charging process and the corona, imparts and provides enough treatment charges to receptors including the aforementioned receptors. Researchers often relied on adopting prior corona charger methods that do not necessarily and effectively solve the problems associated with them or utilize them for optimum treatment effect. The inventor exhaustively studied the characteristics of corona discharge, and has found that the greatest difficulty in corona discharge has to do with the maintenance of the corona, particularly when the receptor is being charged. This is due to variations in either the dielectric value between the corona electrode and a grounded base or flaws in the design as the receptor passes there between suppressing or hindering corona and its effectiveness. What is needed in-the-art is an apparatus and method to achieve maximum possible charge on a receptor, a charge order of magnitude greater than that used by other investigators. This often requires customizing each apparatus and method and does not just merely use one type of a charger to satisfy all applications. To satisfy this need, we build a low cost prototype BMCC that generates self-sustaining charge corona, eliminates many previous design flaws such as spark over, and make it ready for testing remotely or with apparatus. 相似文献
663.
Mehmet Sinan Yıldırım Metin Mutlu Aydın Ümit Gökkuş 《Maritime Policy and Management》2020,47(6):833-848
ABSTRACT Solving the berth allocation problem (BAP) in ports is not trivial where the berth resources are limited and various sizes of vessels arrive with dramatically dissimilar loads. Especially in real scenarios, arriving vessels are accepted for a berth with the first come first served (FCFS) priority rule. This study proposes a decision support system coupled with a simulation optimization module based on the swarm-based Artificial Bee Colony optimization algorithm for solving the BAP. The proposed methodology was implemented for the Izmir port in Turkey. To investigate the influences of the vessel priorities on the BAP, four different experimental scenarios based on the single (SQM) and multiple queue models (MQM) were coupled with FCFS and proposed hybrid queue priority (HQP) rule. The results indicated that SQM scenarios were superior to MQM scenarios in a manner of minimizing the average vessel waiting times and the implementation of a dynamic berth allocation strategy for the MQM significantly decreases the vessel waiting times. Results of the SQM also imply that utilization of the HQP approach further minimizes the average vessel waiting times and increases the berth utilization and port throughput without yielding excessive waiting times for the larger vessels compared with the FCFS priority rule. 相似文献
664.
Centre for Marine Technology Ocean Engineering Instituto Superior Técnico Universidade de Lisboa - Lisboa Portugal 《船舶与海洋工程学报》2020,(4):509-511
The assessment of the ultimate strength of floating struc-tures is an essential step in their design process and thus it is included as one of the checks in the... 相似文献
665.
梁野 《上海交通大学学报(英文版)》2016,21(1):18-24
In view of the study of finance and economics information, we research on the real-time financial news posted on the authority sites in the world’s major advanced economies. Analyzing the massive financial news of different information sources and language origins, we come up with a basic theory model and its algorithm on financial news, which is capable of intelligent collection, quick access, deduplication, correction and integration with financial news’ backgrounds. Furthermore, we can find out connections between financial news and readers’ interest. So we can achieve a real-time and on-demand financial news feed, as well as provide a theoretical basis and verification of the scientific problems on real-time processing of massive information. Finally, the simulation experiment shows that the multilingual financial news matching technology can give more help to distinguish the similar financial news in different languages than the traditional method. 相似文献
666.
Considering the modeling uncertainties and external disturbance, a kind of sliding mode robust H∞fault-tolerant control method for time delay system with actuator fault is proposed. The upper-bound of the uncertainties is considered as a known constant, while the upper-bound of the actuator fault is unknown. A sufficient condition for the existence of an integral sliding mode dynamics is given in terms of linear matrix inequality(LMI). A novel adaptive law is given to estimate the unknown upper-bound of faults. On this basis, a type of sliding mode robust H∞fault-tolerant control law is designed to guarantee the asymptotic stability and the H_∞ performance index of the system. Finally, the simulation on quad-rotor semi-physical platform demonstrates the reliability and validity of the method. 相似文献
667.
This paper investigates the gap between qualitative and quantitative constraints in spare parts stock control, with specific reference to warship spare parts support projects. A critical literature review of theoretical contributions about qualitative or quantitative factors for warship spare parts warehouse management is firstly provided, which allows to analyze the reasons for this qualitative-quantitative gap by addressing the limitations of spare parts models developed in the literature. Therefore a model including cloud model, marginal analysis and Lagrange multiplier method (CML) for study is proposed in this paper to bridge the gap. The model is used to solve the mix-constraints (both qualitative and quantitative constraints are considered) problem in a logic decision diagram particularly at the different decision nodes of the diagram. Finally, verifying test results show that the algorithm is feasible and its optimal support project meets the needs of engineering practices. 相似文献
668.
Based on the Hamilton principle, dynamic differential equation of the submarine pipeline span, under the interaction of internal
flow and external environmental loads, is established. A constraint-equivalent method is used to deal with the boundary conditions
of pipeline span on the linear elastic seabed. Effects of the internal flow velocity and seabed stiffness on the pipeline’s
lateral deformation and bending stress are studied by the static analysis, while the preliminary relationships between the
internal flow velocity and the foundation stiffness to the natural frequency of pipeline span are investigated by the dynamic
analysis. It is found that the lateral deformation increases with the increment of internal flow velocity, but decreases with
the increment of seabed stiffness. The bending stress at the ends of span increases with the increment of internal fluid velocity
and the seabed stiffness, however the stress at the middle of the span shows the converse tendency. Moreover, increasing the
seabed stiffness or decreasing the internal flow velocity can lead to higher natural frequency. The dynamics response of midpoint
of span at different foundations and internal fluid velocities are also given in this paper. 相似文献
669.
This paper introduces a new means to predict consolidation deformation of soil from its microstructure. Based on a kind of
pore-size distribution density function, a fractal model for soil consolidation is established. Through this model, the relation
between macroscopic deformation and microcosmic pore property of soil is founded. In order to justify this proposed model
for soil consolidation, consolidation experiments of soft clay are performed. Afterward, the microstructure of soft clay unconsolidated
and consolidated under every pressure is studied by a scanning electron microscope (SEM). The results show that the proposed
model for soil consolidation is valid in predicting consolidation deformation. 相似文献
670.
The non-destructive testing (NDT) of debonding in stainless steel composites plate (SSCP) is performed by infrared thermography,
finite element analysis (FEA) software ANSYS is taken as the simulative tool, and 2D simulative model has been set up to investigate
effect of the thickness of coating and/or substrate on the detectibility of debonging in SSCPs. Two parameters, namely the
maximum defect temperature difference and defect appearing index, are defined to evaluate the detectivity of defects, and
their computational methods and formulas are given respectively. The preliminary changing tendency of the maximum defect temperature
difference and defect appearing index with the thickness of coating and/or substrate is found by numerical simulation. 相似文献