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461.
The parameter values which actually change with the circumstances, weather and load level etc.produce great effect to the result of state estimation. A new parameter estimation method based on data mining technology was proposed. The clustering method was used to classify the historical data in supervisory control and data acquisition (SCADA) database as several types. The data processing technology was impliedto treat the isolated point, missing data and yawp data in samples for classified groups. The measurement data which belong to each classification were introduced to the linear regression equation in order to gain the regression coefficient and actual parameters by the least square method. A practical system demonstrates the high correctness, reliability and strong practicability of the proposed method. 相似文献
462.
李发根 《上海交通大学学报(英文版)》2008,13(6):679-683
We show that the Zhang-Yang-Zhu-Zhang identity-based authenticatable ring signcryption scheme is not secure against chosen plaintext attacks.Furthermore, we propose an improved scheme that remedies the weakness of the Zhang-Yang-Zhu-Zhang scheme.The improved scheme has shorter ciphertext size than the Zhang-Yang-Zhu-Zhang scheme.We then prove that the improved scheme satisfies confidentiality, unforgeability, anonymity and authenticatability. 相似文献
463.
Seokjoo Kwon Minkyung Kang Youngho Seo Sungwook Park 《International Journal of Automotive Technology》2018,19(2):253-261
In this study, the influence on fuel economy testing of gasoline-powered vehicles is evaluated for various test conditions (e.g., laboratory temperature, soaking time, cooling fan, battery charge state, and driving mode tracking). It showed a difference in fuel economy results of approximately 3 % between low (88 %) and high (99 %) battery state of charge conditions because the alternator saving function has a positive effect on fuel economy. Fuel economy testing with laboratory temperature changes gave a slight reduction at 21 °C and slight increase at 29 °C. The cooling fan changes had an almost negligible effect on fuel consumption. The largest fuel economy result varied by 5.2 % in the soft, standard, and rough driving conditions. 相似文献
464.
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
465.
SONG Zhi-ming KANG Feng-ju TANG Kai and CHU Yan-jun Marine College Northuxstern Polytechnical University Xi'''' an China 《船舶与海洋工程学报》2003,2(2):40-45
Realistic simulation of underwater scene is always difficult because of the special and complex vision effects in underwater space. Seabed is an important part of underwater environment. This paper describes the methods for seabed scene simulation based on OpenGL. It includes construction of fluetuant terrain based on the random sinusoidal algorithm, simulation of seabed flicker effect by means of circular texture mapping and generation of turbidity effect by using fog techniques. For the application based on the leading high level 3D development environment-Vega, underwater scene simulation is still a difficulty since there is no module for it. Based on the analysis of Vega software and the research on seabed scene simulation methods, a Vega extending module named “Underwater Space” was created through developing module class and extending lynx interface. The module class was designed through developing DLL written in C . The Lynx was extended through developing keyword configure file, GUI configure file and lynx plug-in DLL. The problem that Vega can‘t simulate underwater space, is elementarily resolved. The results show that this module is efficient, easy using, and the seabed scene images am vivid. 相似文献
466.
Jeom Kee Paik Jae Myung Lee Young II Park Joon Sung Hwang Chang Wook Kim 《Marine Structures》2003,16(8):567-600
Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. In aging ships, corrosion and fatigue cracks are the two most important factors affecting structural safety and integrity. This paper uses a set of the time-dependent corrosion wastage models for 23 different member locations/categories of bulk carriers previously developed by the authors, based on the available corrosion measurements for existing large bulk carrier structures. Differences due to the location and corrosion severity of every member type are taken into account. The nominal design corrosion values for the primary members are suggested based on the annualized corrosion rates obtained in the present study. The effect of time-variant corrosion wastage on the ultimate hull girder strength as well as the section moduli is studied. The criteria for repair and maintenance of heavily corroded structural members so as to keep the ultimate longitudinal strength at an acceptable level are discussed. Important insights and conclusions developed are summarized. 相似文献
467.
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
468.
流场中任意厚度阻尼复合圆柱壳的声辐射(英文) 总被引:1,自引:1,他引:1
The insertion loss of acoustic radiation of damped cylindrical shell described by 3-D elasticity Navier equations under radial harmonic applied load in fluid is presented. The classical integral transform technique, potential theory and Lamè resolution are used to derive the solutions of Navier equations. The higher precision inversion computation is introduced to solve the linear equations. Comparing with acoustic radiation of one-layer cylindrical shell, the influence of thickness, mass density, dilatational wave loss factor and Young's modulus of damping material and circumferential mode number of the cylindrical shell on the insertion loss is concluded. The theoretical model in the paper can be used to deal with the arbitrary thickness and any frequency of the coated layer in dynamic problem. The conclusions may be of theoretical reference to the application of damping material to noise and vibration control of submarines and underwater pipes. 相似文献
469.
WAN De-Cheng 《船舶与海洋工程学报》2007,6(2):51-58
In this paper, an efficient multigrid fictitious boundary method (MFBM) coupled with the FEM solver package FEATFLOW was used for the detailed simulation of incompressible viscous flows around one or more moving NACA0012 airfoils. The calculations were carried on a fixed multigrid finite element mesh on which fluid equations were satisfied everywhere, and the airfoils were allowed to move freely through the mesh. The MFBM was employed to treat interactions between the fluid and the airfoils. The motion of the airfoils was modeled by Newton-Euler equations. Numerical results of experiments verify that this method provides an efficient way to simulate incompressible viscous flows around moving airfoils. 相似文献
470.
Junbo Jia 《Journal of Marine Science and Technology》2007,12(1):43-57
To reduce the area on deck occupied by each car and the labour and time required for lashing and unlashing cars, it has been
proposed by the author that in some conditions, cars on decks could be transported without lashing. To evaluate cargo securing
based on this “lashing-free” concept, computational code was developed to calculate the vehicle–deck interactions for various
ship motions. The code was structured by incorporating a vehicle model into a piece of ship motion calculation code. A series
of time-domain simulations were conducted to evaluate vehicle securing. It was found that for a target ship consisting of
a 6000-unit Ro-Ro vessel, vehicle securing is mainly influenced by the ship's rolling motions and is highly dependent on the
wave height and loading conditions. It was suggested from the analysis that vehicles could be secured without being lashed
in a large area of the ship in specific weather conditions and on some routes with less adverse sea states. However, it is
still suggested that conventional lashing holes should be constructed on the deck because in severe sea states the cars will
still need to be lashed. The limitations of the current investigations are also presented.
The relevant research work was carried out at the Division of Ship Design and Engineering, Department of Shipping and Marine
Technology, Chalmers University of Technology. 相似文献