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991.
Jamshaid Ali Muhammad Ushaq Salman Majeed 《Journal of Marine Science and Technology》2012,17(3):340-348
The strapdown inertial navigation system (SINS) is able to provide continuous estimates of a vehicle??s velocity, position and attitude. As a rule, the SIMS component known as a high accuracy strapdown inertial measurement unit (SIMU) is an exceptionally expensive system. Less expensive SIMUs comprised of low cost sensors suffer from degraded performance, but this can be compensated for, in part, by addition of a velocity data recorder (VDR) to accompany the SINS. In this configuration, the need frequently arises to align the SINS of a submarine to in order to avoid a long run-up of the inertial system before a start command is issued. This in-motion alignment (IMA) can be accomplished by integrating SINS data with some external aiding source, such as the VDR, by using some form of measurement matching method. Accordingly, this paper demonstrates a consistent IMA scheme for a low-cost SIMU using a robust Kalman/ $ H_{\infty } $ filter structure. An error model of the SINS is derived in which the state vector includes attitude, velocity, position and sensor errors. Velocity information from the VDR is used as a measurement to the proposed filter. All significant equations concerning navigation are presented in conjunction with argument. Results show the advantages of the approach and emphasize diverse aspects of the SINS. 相似文献
992.
Electro-hydraulic braking system for autonomous vehicles 总被引:4,自引:0,他引:4
V. Milanés C. González J. E. Naranjo E. Onieva T. De Pedro 《International Journal of Automotive Technology》2010,11(1):89-95
Reducing the number of traffic accidents is a declared target of most governments. Since dependence on driver reaction is the main cause of road accidents, it would be advisable to replace the human factor in some driving-related tasks with automated solutions. To automate a vehicle, it is necessary to control the actuators of a car, i.e., the steering wheel, accelerator, and brake. This paper presents the design and implementation of an electro-hydraulic braking system consisting of a pump and various valves, allowing the control computer to stop the car. It is assembled in conjunction with the original circuit for the sake of robustness and to permit the two systems to halt the car independently. This system was developed for installation in a commercial Citroën C3 Pluriel of the AUTOPIA program. Various tests were carried out to verify its correct operation, and an experiment showing the integration of the system into the longitudinal control of the car is described. 相似文献
993.
In H.264,the computational complexity and memory access of deblocking filter are variable and depend on the video contents. In this paper,a pipelined VLSI architecture of deblocking filter with adaptive dynamic power is proposed. It avoids redundant computations and memory access by precluding the blocks which can be skipped. And the vertical and horizontal edges are simultaneously processed in an advanced scan order to speed up the decoder. As a result,the dynamic power of the proposed architecture can be ... 相似文献
994.
The static softening behavior of aluminum alloy A6082 was investigated by interrupted hot tests conducted on Gleeble-1500
simulator at deformation temperatures from 573 to 773 K and strain rates from 0.1 to 10 s−1, with a pre-strain from 0.3 to 0.7 and variable inter-pass delay times. The offset method was applied to convert the changes
in flow stress between two passes to static softening fraction. The microstructural changes were characterized by the quantitative
metallography of quenched specimens. The results showed both static softening and static recrystallization curves exhibited
a simple sigmoidal shape; the static softening is related to the static recrystallization in a nonlinear manner with 50% static
recrystallized volume fraction corresponding to 80% static softening fraction; an increase in temperature, strain rate or
pre-strain yields a decrease in the time for 50% static recrysallized volume fraction, on which the temperature has the most
remarkable influence; Si and Mn additions accelerate the process of static recrystallization. Finally, the equations of static
recrystallization kinetics of this alloy were developed with a good agreement between the predicted and experimental results. 相似文献
995.
It is very difficult,for the component-type ship mathematical model,to estimate the interaction force coefficients among the hull,propeller and rudder. Some coefficients such as wake fraction and flow straightening coefficient were studied from the model tests in diffierent loading conditions and the normal force of rudder was tested in captive model tests to obtain the coefficients. From these results of the tests,the flow straightening coefficients increase with the increase of trims or drafts. Similarly,... 相似文献
996.
AbstractTo study an entity the entire jack-up performs as a total system with close interdependency and high level of integration of a myriad of subsystems supporting each individual function.All subsystems should be arranged in regular geometric space with clear regional division according to their respective functions.The "building block"such as arrangement makes it feasible to apply modular design method while the integration and conflicts among subsystems offer an arena for game theoretic analysis.All the contradictions between subsystems should be resolved bye the designer.Here we present a game theoretic analysis methodology,which based on the basic principles of game theory,through the establishment of matrix-mode game models to describe and analyze engineering design tasks.By using this method the optimization process in various fields of expertise can be effectively coordinated and controlled,and the parallel design patterns can be achieved to some extent.Taking account of the impact of commercial or technical activities in platform’s life cycle,time line is considered in the early stage of design process which provides more convenience for effcient upgrade and reconfiguration.Some second-hand three-legged jack-up upgrade design process is used as an example to illustrate the utility of the method. 相似文献
997.
Grinding is known as the most complicated material removal process and the method for monitoring the grinding wheel wear has
its own characteristics comparing with the approaches for detecting the wear on regular cutting tools. Research efforts were
made to develop the wheel wear monitoring system due to its significance in grinding process. This paper presents a novel
method for identification of grinding wheel wear signature by combination of wavelet packet decomposition (WPD) based energies.
The distinctive feature of the method is that it takes advantage of the combinational information of the decomposed frequency
components based on the WPD so the extracted features can be customized according to the specific monitored object to get
better diagnosis effects. Experiments are researched on monitoring of grinding wheel wear states under different machining
conditions. The results show that the energy ratio extracted from the measured vibration signals is consistent with the grinding
wheel wear condition evaluated by experiment and the further extracted feature ratio can be used in prediction of wheel wear
condition. 相似文献
998.
Subjective well-being related to satisfaction with daily travel 总被引:1,自引:0,他引:1
Cecilia Jakobsson Bergstad Amelie Gamble Tommy Gärling Olle Hagman Merritt Polk Dick Ettema Margareta Friman Lars E. Olsson 《Transportation》2011,38(1):1-15
Previous research demonstrates an impact on subjective well-being (SWB) of affect associated with routine performance of out-of-home
activities. A primary aim of the present study is to investigate whether satisfaction with daily travel has a positive impact
on SWB, either directly or indirectly through facilitating the performance of out-of-home activities. A secondary aim is to
determine whether emotional-symbolic or instrumental reasons for car use results in higher satisfaction with daily travel
than other travel modes. A survey of a population-based sample of 1,330 Swedish citizens included measures of car access and
use, satisfaction with daily travel, satisfaction with performance of out-of-home routine activities, and affective and cognitive
SWB. The results confirmed that the effect on affective and cognitive SWB of satisfaction with daily travel is both direct
and indirect via satisfaction with performance of activities. Percent weekly car use had a small effect on satisfaction with
daily travel and on affective SWB, although fully mediating the effect of satisfaction with performance of the activities.
This suggests that car use plays a minor role for satisfaction with daily travel and its effect on SWB. This role may be larger
if investigated after a forced reduced car use. 相似文献
999.
Kiron Chatterjee 《Transportation》2011,38(3):487-509
Panel data offers the potential to represent the influence on travel choices of changing circumstances, past history and persistent
individual differences (unobserved heterogeneity). A four-wave panel survey collected data on the travel choices of residents
before and after the introduction of a new bus rapid transit service. The data shows gradual changes to bus use over the four
waves, implying time was required for residents to become aware of the new service and to adapt to it. Ordered response models
are estimated for bus use over the survey period. The results show that the influence of level of service (LOS) is underestimated
if unobserved heterogeneity is not taken into account. The delayed response to the new service is able to be well represented
by including LOS as a lagged variable. Current bus use is found to be conditioned on past bus use, but with additional influence
of lagged LOS and unobserved heterogeneity. It is shown how different model specifications generate different evolution patterns
with the most realistic predictions arising from a model which takes into account lagged responses to change in LOS and unobserved
heterogeneity. The paper demonstrates the feasibility of developing panel data models that can be applied to forecasting the
effect of interventions in the travel environment. Longer panels—encompassing periods of both stability and change—are required
to support future efforts at modelling travel choice dynamics. 相似文献
1000.
A unique set of activity scheduling data is utilized in this paper to provide much needed empirical analysis of the sequence
in which activities are planned in everyday life. This is used to assess the validity of the assumption that activities are
planned in accordance to a fixed hierarchy of activity types: mandatory activities first (work/school), followed by joint maintenance, joint discretionary, allocated maintenance, and
individual discretionary activities. Such an assumption is typical of current generation activity and tour-based travel demand
models. However, the empirical results clearly do not support such assumptions. For instance, fewer than 50% of mandatory
activities were actually planned first in related out-of-home tours; remaining activity types also did not take any particular
precedence in the planning sequence. Given this, a search was made for the more salient attributes of activities (beyond activity
type) that would better predict how they are planned within tours. Several ordered response choice models for different tour
sizes were developed for this purpose, predicting the choice order of the 1st, 2nd, 3rd, etc. planned activity in the tour
as a function of activity type, activity characteristics (duration, frequency, travel time, and involved persons), and individual
characteristics. Activity duration played the most significant role in the models compared to any other single variable, wherein
longer duration activities tended to be planned much earlier in tours. This strongly suggests that the amount of time-use,
rather than the nature of the event as indicated by activity type, is a primary driver of within-tour planning order and offers
potential for a much improved and valid fit. 相似文献