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441.
An activated antiroll tank system design for ship roll reduction was investigated. Considering the dynamics of the ship motion,
tank flow, and variable-pitch impeller, a control law is derived based on optimal control and estimation theory. Finally,
a series of numerical computations for a 1174 tonne ship without an antiroll tank system, with a passive tank system, and
with the proposed activated antiroll tank system is performed. The results show that the proposed activated tank system has
superior antiroll properties for free rolling, regular, and irregular sea loads to the passive tank system. In addition, this
design has a very low sensitivity to variations in ship and tank dynamics. It shows that the proposed system is reliable and
valid for practical use. 相似文献
442.
RECENTRESEARCHANDDEVELOPMENTOFPOLYMEROPTICALFIBRES*GDPeng(彭刚定)PLChu(朱柏濂)(SchoolofElectricalEngineering,Univ.ofNewSouthWales,K... 相似文献
443.
L. Fortier M. Gilbert D. Ponton R. G. Ingram B. Robineau L. Legendre 《Journal of Marine Systems》1996,7(2-4)
We monitored the feeding success (percent feeding incidence at length and mean feeding ratio at length) of Arctic cod (Boreogadus saida) and sand lance (Ammodytes sp.) larvae in relation to prey density, light, temperature and potential predator density under the ice cover of southeastern Hudson Bay in the spring of 1988, 1989 and 1990. Both prey density and light limited larval fish feeding. The relationship between feeding success and actual food availability (nauplii density X irradiance) was adequately described by an Ivlev function which explained 64 and 76% of the variance in Arctic cod and sand lance feeding success respectively. By affecting both prey density and irradiance, the thickness of the Great Whale River plume (as defined by the depth of the 25 isohaline) was the main determinant of prey availability. Arctic cod and sand lance larvae stopped feeding when the depth of the 25 isohaline exceeded 9 m. Limitation of feeding success attributable to freshwater inputs occurred exclusively in 1988, the only time when the depth of the 25 isohaline exceeded the 9 m threshold. The close dependence of larval fish feeding success on the timing of the freshet and plume dynamics suggests a direct link between climate and survival of Arctic cod and sand lance larvae. The actual impact of climate fluctuations and/or hydro-electric developments on recruitment will depend on the fraction of the larval dispersal area of the two species that is affected by river plumes. 相似文献
444.
The Stationary Motion of a One-Axle Vehicle Along a Circular Curve with Real Rail and Wheel Profiles
P. Arrus A. D. de Pater P. Meyers 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2002,37(1):29-58
In this paper, we present a theory on the stationary motion of a one-axle railway vehicle along a circular curve in the presence of single- or double-point contact. The rail and the wheel profiles may be either stylized or real and as an example we take the profile combination UIC60 1:40 S1002. The mathematical model of the system is based on De Pater's first-order theory [1]. The geometrical contact problem between wheel and rail is solved by using a modified Newton-Raphson procedure. Both the cases with and without friction are considered. When friction is present, the non-linear Kalker creep law [6, 7] is used to describe the physical contact. For various values of the friction coefficient, the cant angle and the curvature of the track, the contact forces are presented as functions of the velocity parameter C v = V 2 / V 2 eq , where V is the velocity of the vehicle and V eq is the equilibrium velocity of the frictionless case. For the case of stylized profiles in which both the wheel treads and the wheel flanges are conical, and the rail cross sections are circular, we have determined the velocity range with single point contact in dependence on the friction coefficient, the conicity of the tread, the curvature of the track and the cant angle. 相似文献
445.
Analysis of Influence of Design Parameters on Steered Wheels Shimmy of Heavy Vehicles 总被引:4,自引:0,他引:4
Miroslav Demi Prof. Miroslav Demid Ph. D. 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1996,26(5):343-379
In choosing the steering system parameters the tendency is towards the minimization of kinematic errors that appear during turning. For that developed procedures exist that take into account also the influence of kinematic of the suspension system on kinematic parameters of vehicle turning. Besides that, maintenance tests have shown, that increased deflections of the suspension system lead to increased wear of tires of steered wheels. In this paper, a method is developed for minimization of steered wheel shimmy and its wear also during the straight-line drive of heavy vehicles. The procedure can also be used in the phase of designing the heavy vehicles. 相似文献
446.
J. Eyre D. Yanakiev I. Kanellakopoulos 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1998,30(5):375-405
Automated vehicles traveling in platoons must exhibit stability both individually and as a group, a property referred to as “string stability”. We propose a new framework for evaluating the longitudinal string stability properties of platoons of automated vehicles. In this framework, the platoon is considered to be a mass-spring-damper system with linear characteristics. The resulting closed-loop representation yields transfer functions and impulse responses that can be analyzed to determine the string stability properties of the platoon. This framework facilitates qualitative comparisons of the effects of various controller characteristics, such as time headway and intervehicle communication, on string stability. 相似文献
447.
448.
Theodore S. Glickman Hanif D. Sherali 《Transportation Research Part B: Methodological》1985,19(2):85-94
A set of models and procedures is described for finding the optimal distribution of empty freight cars owned by the railroads participating in a pooling agreement. A distinction is drawn between a system focus, in which the emphasis is on minimizing total cost, and a company focus, in which the benefits of the agreement to the individual railroads are emphasized. Limited car substitution is accounted for by combining interchange costs with distribution costs, and incorporating interchange possibilities and prohibitions into the network structure. Temporal variations in car supply and demand levels are also taken into account. A large-scale network algorithm is used in conjunction with decomposition to obtain solutions which show for a given time horizon how much equity can be achieved in the balance of savings among the railroads involved and at what cost. Results using actual operating data are reported. 相似文献
449.
William C. Jordan Lawrence D. Burns 《Transportation Research Part B: Methodological》1984,18(6):487-503
Truck backhauling reduces empty truck-miles by having drivers haul loads on trips back to their home terminal. This paper 1) examines the impact on backhauling opportunities of terminal locations and directional imbalances in the flow of freight from the terminals, and 2) develops a method for determining which truckloads should be backhauled. Backhauling is studied for two terminals sending full truckloads to many customers under steady-state conditions. This research develops two backhauling models. The first is a continuous model that makes simplifying assumptions about customer locations and travel distances. It results in formulae showing that 1) savings from backhauling increase at a decreasing rate as the directional flow of freight between two terminals becomes more balanced and 2) backhauling is an important, but often ignored, factor in terminal (e.g. trucking terminal, warehouse, or plant) location and supplier selection decisions. The second model is a more general discrete model that determines which loads should be backhauled to minimize empty truck-miles. 相似文献
450.