全文获取类型
收费全文 | 3077篇 |
免费 | 10篇 |
专业分类
公路运输 | 651篇 |
综合类 | 702篇 |
水路运输 | 999篇 |
铁路运输 | 51篇 |
综合运输 | 684篇 |
出版年
2024年 | 3篇 |
2023年 | 19篇 |
2022年 | 54篇 |
2021年 | 9篇 |
2020年 | 11篇 |
2019年 | 12篇 |
2018年 | 406篇 |
2017年 | 313篇 |
2016年 | 303篇 |
2015年 | 19篇 |
2014年 | 67篇 |
2013年 | 154篇 |
2012年 | 118篇 |
2011年 | 277篇 |
2010年 | 287篇 |
2009年 | 113篇 |
2008年 | 241篇 |
2007年 | 160篇 |
2006年 | 27篇 |
2005年 | 80篇 |
2004年 | 54篇 |
2003年 | 70篇 |
2002年 | 29篇 |
2001年 | 15篇 |
2000年 | 25篇 |
1999年 | 17篇 |
1998年 | 16篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 22篇 |
1994年 | 9篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 7篇 |
1989年 | 4篇 |
1987年 | 7篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 9篇 |
1980年 | 3篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1973年 | 3篇 |
1972年 | 4篇 |
排序方式: 共有3087条查询结果,搜索用时 0 毫秒
991.
A 2D advection-dispersion model, already described and validated, has been used to provide information about water trajectories, transit times, transfer factors and transfer functions in the Channel and North Sea, south of 57 ° N.It shows that a fast vein of water moves parallel to the coast and reaches the northern limit of the model in one year. Along the coast, a few dozen kilometers from this vein, transit times increase by 2–4 months.Tidal gyres in the Channel recirculate waters and dissolved elements for about 2 yr, and in all it generally takes 3 yr for a specific discharge made at La Hague to completely leave the area under study.The transfer factor was depicted and found to be of the order of 10−5 m.k.s.One utilization of the transfer function could be to predict the future evolution of water content in the months and years following a discharge in these coastal waters. 相似文献
992.
The methodology adopted in the design of small fishing vessels is usually concerned only with the vessel's technical characteristics and the procedures utilized may not include consideration of the relevant fishing environment. This paper describes an approach which incorporates operational, economic and technical considerations in a compressive manner. The efficiency of using multicriteria decision making methods in design is investigated with special reference to small vessels. A model is presented which takes into account various operational and fish resource factors. This allows the inclusion of a number of potentially conflicting requirements and goals within the design process. The resulting analysis identifies the optimum fleet mix for three types of fishing vessels for use in a fishing environment of a developing country. 相似文献
993.
994.
995.
A. Moawad P. Balaprakash A. Rousseau S. Wild 《International Journal of Automotive Technology》2016,17(6):1067-1077
This paper demonstrates a new process that has been specifically designed for the support of the U.S. Department of Transportation’s (DOT’s) Corporate Average Fuel Economy (CAFE) standards. In developing the standards, DOT’s National Highway Traffic Safety Administration made use of the CAFE Compliance and Effects Modeling System (the “Volpe model” or the “CAFE model”), which was developed by DOT’s Volpe National Transportation Systems Center for the 2005–2007 CAFE rulemaking and has been continuously updated since. The model is the primary tool used by the agency to evaluate potential CAFE stringency levels by applying technologies incrementally to each manufacturer’s fleet until the requirements under consideration are met. The Volpe model relies on numerous technology-related and economic inputs, such as market forecasts, technology costs, and effectiveness estimates; these inputs are categorized by vehicle classification, technology synergies, phase-in rates, cost learning curve adjustments, and technology “decision trees”. Part of the model’s function is to estimate CAFE improvements that a given manufacturer could achieve by applying additional technology to specific vehicles in its product line. A significant number of inputs to the Volpe decision-tree model are related to the effectiveness (fuel consumption reduction) of each fuel-saving technology. Argonne National Laboratory has developed a fullvehicle simulation tool named Autonomie, which has become one of the industry’s standard tools for analyzing vehicle energy consumption and technology effectiveness. Full-vehicle simulation tools use physics-based mathematical equations, engineering characteristics (e.g., engine maps, transmission shift points, and hybrid vehicle control strategies), and explicit drive cycles to predict the effectiveness of individual and combined fuel-saving technologies. The Large-Scale Simulation Process accelerates and facilitates the assessment of individual technological impacts on vehicle fuel economy. This paper will show how Argonne efficiently simulates hundreds of thousands of vehicles to model anticipated future vehicle technologies. 相似文献
996.
In this paper, shock sterilization using the motions of microbubbles induced by underwater shock waves is verified experimentally. A bio-experiment is carried out using marine Vibrio sp.. Underwater shock waves are produced by electric discharge in a semi-ellipsoidal discharge reflector. The shock waves are focused to increase the pressure that the generated microbubbles are exposed to. The microbubbles are generated independently. The microbubble generator can produce microbubbles of around 50 μm diameter by means of Kelvin–Helmholz instability and Venturi effect. Propagation behavior of shock waves and generation process of microbubbles are captured by high-speed camera. The experimental results show that the supply of microbubbles increases the potential of shock sterilization. In addition, it is found that shock waves without microbubbles also have the capacity of sterilization, and this means that cavitation bubbles generated behind converging shock waves contribute to inactivating marine bacteria. 相似文献
997.
Samrat Ghosh Marcus Bowles Dev Ranmuthugala Ben Brooks 《WMU Journal of Maritime Affairs》2016,15(2):317-336
With the Standards of Training, Certification and Watchkeeping Convention 1995 (STCW’95) moving seafarer training towards outcome-based education (OBE), emphasis has shifted to assessment practices that will allow seafarer students to demonstrate their ability to perform workplace tasks at standards described in the STCW Code. This paper argues that authentic assessment comprising of performance-based tasks applied in real-world and meaningful contexts can provide a holistic approach to competence assessment for seafarers. But, authentic assessment can capture essential aspects of workplace tasks and result in consistency of student performance in different contexts only if they are valid and reliable. Rubrics as assessment tools are known to increase validity and reliability of assessments; however, it can do so only if different aspects of its own validity and reliability have been addressed. A literature review undertaken for this paper has uncovered an absence of academic investigation and empirical study on the different aspects of validity and reliability of authentic assessment through assessment rubrics. Moreover, there exists an even greater absence of global research on authentic assessment in the area of seafarer training. Through an investigation of authentic assessment, this research has uncovered the importance of using valid and reliable rubrics in order to improve not only the assessment process but also the tools and methods used to support the valid, reliable, and authentic assessment of outcomes achieved in the learning process. Future research aims to offer insights into improving the validity and reliability of rubrics and to empirically investigate how they can be used in authentic assessment within the confines of the STCW Code, in particular, to improve seafarer training practices, student engagement, resulting learning outcomes, and employer and regulator satisfaction with the attainment of the standards stipulated in the STCW Code to produce an evidence of competence. 相似文献
998.
Transportation infrastructure planning process requires cost–benefit analysis in the evaluation of project proposals. Value of time (VOT) facilitates the conversion of travel time savings, which is a significant proportion of benefits in monetary terms. In cases where VOT has not been established, planners resort to crude estimates that often results in erroneous or biased measurements of benefits. This is the case of the Western Visayas region in the Philippines where transportation studies are rare. Secondary cities and its peripheral regions have often been overlooked subjects of transportation studies. In this study, multinomial logit models using revealed preference data were estimated to facilitate the calculation of the VOT. The total cost, square of the total cost, and total time were identified as significant explanatory variables affecting mode choice. The square of the total cost term was introduced in the models in order to account for income effect. Results indicate that VOT estimates for the inter-island passenger transportation between Iloilo and Negros Occidental generally range from 78.15PHP to 179.15PHP (1.91USD to 4.37USD) depending on trip and traveller characteristics. 相似文献
999.
Comprised by a swarm of acoustically linked and cooperative autonomous underwater vehicles (AUVs) with onboard sensors, an underwater mobile sensing network (UMSN) will be a complementary means to fixed observatory networks, e.g. seafloor observatory networks and moored buoy arrays. It has obvious advantages over a single large AUV in higher efficiency due to parallel observation, stronger robustness to vehicle failures and lower cost. Although an UMSN can be viewed as a counterpart of wireless mobile sensing networks for air and terrestrial applications, it is much more challenging due to poor performance of underwater acoustic communication, poor performance of underwater positioning and high degree of uncertainty in vehicle dynamics and underwater environment. In order to verify key technologies involved in an UMSN, e.g. cooperation of multi-AUVs based on acoustic communication, a low cost testbed has been developed for experimental study. The design of both hardware and software is introduced. Also the results of a functional test for verification of the effectiveness of the testbed are presented. 相似文献
1000.
This study focuses on the user-interface of the route guidance system with an electronic map display. The ultimate goal of the study is to aid in designing electronic map displays that can deliver information to the user most efficiently and expeditiously with minimum confusion. To evaluate the efficiency and understandability of a map display, laboratory experiments were designed and conducted in this study. In the experiments the subjects were presented with electronic map displays of different attributes and performed a set of tasks. Their understanding of the information contents was measured based on the outcomes of the tasks, and subjective ratings of the ease of using the maps were obtained. Using the experimental data obtained, a structural equations model system is developed to explain the understandability of a map display in terms of the subject’s attributes and the characteristics of the map display. The experimental procedure and the modeling results are presented in this paper. 相似文献