首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   222篇
  免费   4篇
  国内免费   5篇
电工技术   5篇
综合类   12篇
化学工业   29篇
金属工艺   5篇
机械仪表   4篇
建筑科学   38篇
矿业工程   3篇
能源动力   2篇
轻工业   11篇
水利工程   1篇
石油天然气   4篇
无线电   17篇
一般工业技术   85篇
冶金工业   5篇
原子能技术   1篇
自动化技术   9篇
  2021年   3篇
  2020年   2篇
  2019年   2篇
  2017年   2篇
  2016年   6篇
  2015年   3篇
  2014年   9篇
  2013年   5篇
  2012年   4篇
  2011年   4篇
  2009年   7篇
  2008年   23篇
  2007年   18篇
  2006年   17篇
  2005年   11篇
  2004年   19篇
  2003年   24篇
  2002年   17篇
  2001年   20篇
  2000年   7篇
  1999年   5篇
  1998年   2篇
  1997年   3篇
  1996年   2篇
  1995年   1篇
  1992年   1篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1986年   1篇
  1983年   1篇
  1982年   1篇
  1978年   1篇
  1977年   2篇
  1976年   1篇
  1975年   3篇
  1974年   1篇
排序方式: 共有231条查询结果,搜索用时 46 毫秒
1.
In this paper, we present an aero‐structural model of a tethered swept wing for airborne wind energy generation. The carbon composite wing has neither fuselage nor actuated aerodynamic control surfaces and is controlled entirely from the ground using three separate tethers. The computational model is efficient enough to be used for weight optimisation at the initial design stage. The main load‐bearing wing component is a nontypical “D”‐shaped wing‐box, which is represented as a slender carbon composite shell and further idealised as a stack of two‐dimensional cross section models arranged along an anisotropic one‐dimensional beam model. This reduced 2+1D finite element model is then combined with a nonlinear vortex step method that determines the aerodynamic load. A bridle model is utilised to calculate the individual forces as a function of the aerodynamic load in the bridle lines that connect the main tether to the wing. The entire computational model is used to explore the influence of the bride on the D‐box structure. Considering a reference D‐box design along with a reference aerodynamic load case, the structural response is analysed for typical bridle configurations. Subsequently, an optimisation of the internal geometry and laminate fibre orientations is carried out using the structural computation models, for a fixed aerodynamic and bridle configuration. Aiming at a minimal weight of the wing structure, we find that for the typical load case of the system, an overall weight savings of approximately 20% can be achieved compared with the initial reference design.  相似文献   
2.
智慧旅游未来发展前景广阔,移动终端在智慧旅游发展过程中的重要性日益凸显.文章阐述了移动终端在智慧旅游发展中的重点应用途径,并提出未来移动终端的使用会更加趋向于安全、便捷、高效、易用的趋势与特征.  相似文献   
3.
In 2002, over a million refrigerated road vehicles, 400,000 refrigerated containers and many thousands of other forms of refrigerated transport systems are used to distribute chilled and frozen foods throughout the world. All these transportation systems are expected to maintain the temperature of the food within close limits to ensure its optimum safety and high quality shelf life.Increasingly, modelling is being used to aid the design and optimisation of food refrigeration systems. Much of this effort has concentrated on the modelling of refrigeration processes that change the temperature of the food such as chilling, freezing and thawing. The purpose of a refrigerated transport system is to maintain the temperature of the food and appears to have attracted less attention from modellers. This paper reviews the work that has been carried out specifically on the modelling of food temperature, microbial growth and other parameters in the transportation of food.  相似文献   
4.
Carbon dioxide has been used as a refrigerant in vapour compression systems of many types for over 130 years, but it is only in the last decade that inventive minds and modern techniques have found new ways to exploit the uniquely beneficial properties of this remarkable substance. This paper traces the development of the old carbon dioxide systems, considers the technical, commercial and social reasons for their slow development and subsequent decline and examines the recent renaissance across a surprisingly broad range of applications, from trans-critical car air conditioners to low temperature industrial freezer plants. The paper then concentrates on industrial refrigeration systems, which were the basis of early developments in the period 1865–1885, but which have been somewhat overlooked in the current renaissance. The paper concludes with a review of possible future developments, indicating the areas of research and product development required to maximise the potential of the only non-toxic, non-flammable, non-ozone-depleting, non-global-warming refrigerant available for Rankine cycle vapour compression systems in the 21st century.  相似文献   
5.
热管式余热锅炉的优化设计与实践   总被引:1,自引:0,他引:1  
给出了热管式余热锅炉Yong效率的计算表达式,采用Yong效率为约束的能量平衡方法设计热管式余热锅炉,从而达到优化设计的目的,并且在工程实际应用中取得了较好的效果。  相似文献   
6.
信息技术与高等数学课程整合研究   总被引:2,自引:0,他引:2  
针对高等数学课程改革的趋势,分析了信息技术环境下高等数学课程的特征,论述了信息技术与高等数学课程整合的模式,给出了信息技术与高等数学课程整合的一些途径.  相似文献   
7.
A study, comparing the effect of blowing agent selection on energy consumption and the life cycle climate performance (LCCP) of a typical European refrigerator is discussed. Energy consumption of prototype European-style refrigerators made with a foam formulation with HFC-245fa as the blowing agent was measured and compared with energy consumption of the same model as currently produced (using a foam with a pentane blend for the blowing agent). Results were used in a LCCP study, considering both direct and indirect climate impacts due to blowing agent emissions and energy consumption in manufacturing processes and over the life cycle of the refrigerator. An assumption is made that the refrigerator is built and used in the European market.  相似文献   
8.
Megaprojects are complex projects which impact millions of people, involve public and private stakeholders, and present challenges related to decision making and performance shortfalls. They are relevant cases for studying faulty management thinking as well as performance evolutions and self-organizing dynamics. Our paper builds on the theory of Complex Adaptive Systems (CAS) to understand and model processes of evolution in the Hinkley Point C nuclear power plant megaproject. The results show that CAS properties apply to megaproject changes and provide a theoretical and practical framework for examining and modeling megaproject management dynamics. We designed a research methodology combining content analysis and historical research for its relevance in conducting organizational research in conditions of complexity and non-linearity. This original research design makes it possible to conduct causal analyses of relations between key megaproject events and thus build models of evolution dynamics in stakeholder success expectations, change mechanisms in the implementation of project outputs, and self-organizing patterns.  相似文献   
9.
针对光寻址电位传感器(LAPS,light addressable potentiometric sensor)测量精度易受温度 影响的问题,提出一种基于支持向量机(SVM)的LAPS温度补偿方法。根据在多温度条件下LAP S传感 器对缓冲液pH的实测数据,利用SVM建立LAPS温度补偿模型,通 过核函数把LAPS输出饱和光电流与温度间的非线性关系映射到高维特征空间,在高维空间中 用线性回归实 现该映射的非线性处理,对LAPS的温度特性进行非线性逼近,补偿温度对LAPS输出的影响。 实验结果表 明,在(20±1)、(20±2)和(20±5) ℃温度变化情况下,经过温度补偿后LAPS系统输出 pH的标准偏差 分别为补偿前的1/3、1/4和1/6,均小于0.05pH,LAPS 温度补偿算法可以明显补偿温度影响,提高LAPS的测量精度。  相似文献   
10.
根据水泥熟料煅烧过程操作控制原理研发的"回转窑人工智能专家系统"采用了人工智能模拟技术、实时数据清洗技术、控制数据关联匹配技术。该系统由分解炉出口温度自动控制系统、篦速自动控制系统和氨水用量自动控制系统三个模块组成。该系统投运后,分解炉出口温度控制有效率由之前人工控制的平均60%~70%提高至平均80%~95%;篦下压力和二次风温稳定性提高;氨水消耗量下降显著;窑系统投料量增加10 t/h左右,熟料标准煤耗降低2.85 kg/t,熟料强度均有提高。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号