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191.
S. R. Sin S. M. Yang H. S. Yu C. W. Kim H. Y. Kang 《International Journal of Automotive Technology》2008,9(1):81-86
The welding quality of spot weldment is an important factor that significantly affects the strength, stiffness, safety, and
other performance characteristics of vehicles. Therefore, quality control and fatigue life evaluation of spot weldment are
necessary processes. This paper presents a method for determining the fatigue life of multi-lap spot weldment of a high strength
steel sheet. In this method, the fatigue life is estimated using the lethargy coefficient, which is the total defect coefficient
according to rupture stress and time obtained by the quasi static tensile-shear test. The DC potential drop method was used
to check initiation and propagation of cracks in addition to the test. Also, in this study, we modified the lethargy coefficient
by using the welding current. Furthermore, we define a specific lapping constant, which is a characteristic constant of 2
or 3 lap weldments. The fatigue life obtained by the fatigue estimate equation, which contains a specific lapping constant
was compared and verified with an experimental value. Finally we analyzed the relation of lap number, welding current and
fatigue life. This method can save processing time and cost for predicting the life cycle of a structure. 相似文献
192.
J. W. Chung J. H. Kang N. H. Kim W. Kang B. S. Kim 《International Journal of Automotive Technology》2008,9(1):1-8
Currently, due to the severity of world-wide air pollution by substances emitted from vehicles, emission control is being
enforced more strictly, and it is expected that the regulation requirements for emission will become even more severe. A new
concept combustion technology that can reduce the Nitrogen oxides (NOx) and PM in relation to combustion is urgently required.
As a core combustion technology among new combustion technologies for the next generation engine, the homogenous charge compression
ignition (HCCI) is expanding its application range by adopting a multiple combustion mode, a catalyst, direct fuel injection
and partially premixed charge compression ignition combustion using the split injection method. This paper used a split injection
method in order to apply the partially premixed charge compression ignition combustion method without significantly altering
engine specifications of the multiple combustion mode and practicality by referring to the results of studies on the HCCI
engine. Furthermore, the effects of the ratio of the fuel injection amount on split injection are investigated. From the test
results, the adequate combination of the ratio of the fuel injection amount for the split injection method has some benefit
on exhaust and fuel economy performance in a naturally aspirated single cylinder diesel engine. 相似文献
193.
H. J. Kim C. H. Bae S. H. Kim H. Y. Lee K. J. Park M. W. Suh 《International Journal of Automotive Technology》2009,10(1):123-129
Urban transit is a complex system that contains both electrical and mechanical entities; therefore, it is necessary to construct
a maintenance system for ensuring safety during high-speed driving. Expert systems are computer programs that use numerical
or non-numerical domain-specific knowledge to solve problems. This research aims to develop an expert system that diagnoses
the causes of failures quickly and displays measures to correct them. For the development of this expert system, the standardization
of a failure code classification and the creation of a Bill of Materials (BOM) were first performed. Through the analysis
of both failure history and maintenance manuals, a knowledge base has been constructed. Also, for retrieving the procedure
of failure diagnosis and repair linking with the knowledge base, we have built a Rule-Based Reasoning (RRB) engine with a
pattern matching technique and a Case-Based Reasoning (CBR) engine with a similar search method. Finally, this system has
been developed as web based in order to maximize accessibility. 相似文献
194.
C. -H. Lee J. -M. Lee M. -S. Choi C. -K. Kim E. -B. Koh 《International Journal of Automotive Technology》2011,12(2):193-198
Since the invention of automobiles, the need to know the braking performance of vehicles has been acknowledged. However, because
there are numerous design variables as well as nonlinearities in the braking system, it is difficult to predict the performance
accurately. In this paper, a computational program is developed to estimate the braking performance numerically. This synthetic
braking performance program accounts for pedal force, pedal travel and deceleration of braking parts, such as master cylinder,
booster, valve, brake pad, rotor, and hoses. To improve the accuracy of program, a semi-empirical model of a braking system
is introduced by using the empirical test data of pad compression, hose expansion and the friction coefficient between the
pad and rotor. The accuracy of the estimation is evaluated by comparing it to the actual vehicle test results. The developed
program is easy for the brake system engineers to manipulate and it can be used in the development of new vehicles by incorporating
the graphical presentations. 相似文献
195.
S. H. Yoo N. T. Jeong K. S. Kim S. M. Yang J. H. Lee S. H. Choi M. W. Suh 《International Journal of Automotive Technology》2016,17(4):681-687
The use of plastic in vehicle development has increased. In particular, a design trend has resulted in chromiumplated plastics being used in exterior panels. Recently, as the appearance has become more important in design, the plastic radiator grille has become larger, to where it can become the primary member when a front collision happens. The radiator grille should be designed with considerations of the geometric structure, such as delamination, and material characteristics, when plastics are plated with chromium. The enlarged grille has to pass regulations like FMVSS Part 581. Although the material property of plastic has been studied before, what seems to be lacking is study on the crashworthiness of plastic radiator grilles that are plated using chromium. In this paper, in order to evaluate the crashworthiness, tensile test and front collision analysis using finite element method are performed. Tensile test is conducted with 4 types of materials, and then material properties of chromium-plated plastics are obtained. Meanwhile radiator grille’s crashworthiness is evaluated using finite element analysis method. Analysis result is evaluated according to failure criterion. Through this study, method of the assessment of plastic radiator grille’s crashworthiness considered material properties of chromium plated plastics is proposed, and it can be predicted the delamination and the failure point of radiator grille at the design step. 相似文献
196.
The intake or exhaust noise of an internal combustion engine is usually predicted by the linear, time-invariant source model in frequency domain with reasonable precision. However, the actual finite amplitude pulsation involves the nonlinear, time-varying characteristics that are prominent in time-domain. To overcome the discrepancy between two source models, an approximate nonlinear and time-varying frequency domain source model can be employed by appending the nonlinear or time-varying terms to the linear, time-invariant source model. Proper selection of the nonlinear describing terms varying with time is important for the realistic and precise prediction of the radiated sound. For the selection of such terms, flow and motional characteristics in the valve and orifice of a simplified fluid machine comprised of very large reservoir, valve, and duct is considered. Effects of each describing term and the combined terms are investigated by comparing the sound spectrum predicted from nonlinear source model to that from linear source model. In the comparison, the sound spectrum calculated by the method of characteristics is used as a reference. It is found that the source model using only the velocityrelated terms yields the best result among all the models using various combinations of the terms with different characteristics. The best model yields a difference from the linear source model within ±5 dB in overall sound level. Change of acoustic loads results in a difference of 20–27 dB in linear source model from the reference data; however, maximum 10–22 dB deviations are observed in using the various nonlinear source models. It is concluded that more than 4 describing terms should be employed in the nonlinear model to obtain a realistic result of the radiated sound from the intake or exhaust system. 相似文献
197.
Jaegu Kang Sanghyun Chu Jeongwoo Lee Gyujin Kim Kyoungdoug Min 《International Journal of Automotive Technology》2018,19(1):27-35
In this research, the effects of three operating parameters (Diesel injection timing, propane ratio, and exhaust gas recirculation (EGR) rates) in a diesel-propane dual fuel combustion were investigated. The characteristics of dual-fuel combustion were analyzed by engine parameters, such as emission levels (Nitrogen oxides (NOx) and particulate matter (PM)), gross indicated thermal efficiency (GIE) and gross IMEP Coefficient of Variance (CoV). Based on the results, improving operating strategies of the four main operating points were conducted for dual-fuel PCCI combustion with restrictions on the emissions and the maximum pressure rise rate. The NOx emission was restricted to below 0.21 g/kWh in terms of the indicated specific NOx (ISNOx), PM was restricted to under 0.2 FSN, and the maximum pressure rise rate (MPRR) was restricted to 10 bar/deg. Dual-fuel PCI combustion can be available with low NOx, PM emission and the maximum pressure rise rate in relatively low load condition. However, exceeding of PM and MPRR regulation was occurred in high load condition, therefore, design of optimal piston shape for early diesel injection and modification of hardware optimizing for dual-fuel combustion should be taken into consideration. 相似文献
198.
Young Ho Kim Kyung-Il Chang Jong Jin Park Seon Ki Park Sang-Hyun Lee Young-Gyu Kim Kyung Tae Jung Kuh Kim 《Journal of Marine Systems》2009,78(2):249
Reanalyzed products from a MOM3-based East Sea Regional Ocean Model with a 3-dimentional variational data assimilation module (DA-ESROM), have been compared with the observed hydrographic and current datasets in the Ulleung Basin (UB) of the East/Japan Sea (EJS). Satellite-borne sea surface temperature and sea surface height data, and in-situ temperature profiles have been assimilated into the DA-ESROM. The performance of the DA-ESROM appears to be efficient enough to be used in an operational ocean forecast system.Comparing with the results from Mitchell et al. [Mitchell, D. A., Watts, D. R., Wimbush, M., Teague, W.J., Tracey, K. L., Book, J. W., Chang, K.-I., Suk, M.-S., Yoon, J.-H., 2005a. Upper circulation patterns in the Ulleung Basin. Deep-Sea Res. II, 52, 1617-1638.], the DA-ESROM fairly well simulates the high variability of the Ulleung Warm Eddy and Dok Cold Eddy as well as the branching of the Tsushima Warm Current in the UB. The overall root-mean-square error between 100 m temperature field reproduced by the DA-ESROM and the observed 100-dbar temperature field is 2.1 °C, and the spatially averaged grid-to-grid correlation between the two temperature fields is high with a mean value of 0.79 for the inter-comparison period.The DA-ESROM reproduces the development of strong southward North Korean Cold Current (NKCC) in summer consistent with the observational results, which is thought to be an improvement of the previous numerical models in the EJS. The reanalyzed products show that the NKCC is about 35 km wide, and flows southward along the Korean coast from spring to summer with maximum monthly mean volume transport of about 0.8 Sv in August–September. 相似文献
199.
Daewon Seo Seung-Hee Lee Sang-Hyun Kim Jungkeun Oh 《Journal of Marine Science and Technology》2012,17(1):18-29
Rudder cavitation causes serious damage to the rudder and affects the safety and cost-effectiveness of a ship. In recent applications,
a semicircular prismatic bar protruding beyond the concave surface of the horn facing the gap, located along the center-plane
of the rudder, has been used to lessen the gap flow between the horn and the movable portion of the rudder system. Previous
numerical studies with this single bar indicate that it can noticeably reduce rudder cavitation. In the present study, a pair
of bars for blocking the vertical gaps, which are attached symmetrically to the center-plane on opposite convex surfaces of
the movable portion, is suggested for circumventing the difficulties that arise in the practical application of single centre
bars. Placed near the outer edges of the gap, the bars are are easily accessible at the maximum rudder angle to allow simple
installation during routine ship maintenance. An additional blocking disk is inserted on top of the pintle block, blocking
the horizontal gaps. Three-dimensional computations are conducted with these combined devices and the results show that the
devices are remarkably efficacious in reducing rudder gap cavitation. 相似文献
200.
J. Kim 《International Journal of Automotive Technology》2010,11(3):331-337
A methodology is presented for estimating vehicle handling dynamics, which are important to control system design and safety
measures. The methodology, which is based on an extended Kalman filter (EKF), makes it possible to estimate lateral vehicle
states and tire forces on the basis of the results obtained from sinusoidal steering stroke tests that are widely used in
the evaluation of vehicle and tire handling performances. This paper investigates the effect of vehicle-road system models
on the estimation of lateral vehicle dynamics in the EKF. Various vehicle-road system models are considered in this study:
vehicle models (2-DOF, 3-DOF, 4-DOF), tire models (linear, non-linear) and relaxation lengths. Handling tests are performed
with a vehicle equipped with sensors that are widely used by vehicle and tire manufacturers for handling maneuvers. The test
data are then used in the estimation of the EKF and identification of lateral tire model coefficients. The accuracy of the
identified values is validated by comparing the RMS error between experimentally measured states and regenerated states simulated
using the identified coefficients. The results show that the relaxation length of the tire model has a notable impact on the
estimation of lateral vehicle dynamics. 相似文献