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   3404篇
  免费   68篇
  国内免费   57篇
电工技术   38篇
综合类   85篇
化学工业   289篇
金属工艺   202篇
机械仪表   806篇
建筑科学   82篇
矿业工程   48篇
能源动力   69篇
轻工业   290篇
水利工程   4篇
石油天然气   57篇
武器工业   19篇
无线电   142篇
一般工业技术   335篇
冶金工业   69篇
原子能技术   9篇
自动化技术   985篇
  2024年   1篇
  2023年   14篇
  2022年   32篇
  2021年   55篇
  2020年   56篇
  2019年   46篇
  2018年   35篇
  2017年   53篇
  2016年   59篇
  2015年   71篇
  2014年   149篇
  2013年   220篇
  2012年   171篇
  2011年   190篇
  2010年   130篇
  2009年   163篇
  2008年   146篇
  2007年   231篇
  2006年   230篇
  2005年   238篇
  2004年   201篇
  2003年   177篇
  2002年   159篇
  2001年   110篇
  2000年   116篇
  1999年   121篇
  1998年   101篇
  1997年   58篇
  1996年   54篇
  1995年   40篇
  1994年   22篇
  1993年   21篇
  1992年   14篇
  1991年   6篇
  1990年   5篇
  1989年   4篇
  1988年   5篇
  1987年   4篇
  1986年   6篇
  1985年   3篇
  1984年   8篇
  1983年   1篇
  1982年   2篇
  1980年   1篇
排序方式: 共有3529条查询结果,搜索用时 15 毫秒
61.
We introduce a general discrete time dynamic framework to value pilot project investments that reduce idiosyncratic uncertainty with respect to the final cost of a project. The model generalizes different settings introduced previously in the literature by incorporating both market and technical uncertainty and differentiating between the commercial phase and the pilot phase of a project. In our model, the pilot phase requires NN stages of investment for completion. With this distinction we are able to frame the problem as a compound perpetual Bermudan option. We work in an incomplete markets setting where market uncertainty is spanned by tradable assets and technical uncertainty is idiosyncratic to the firm. The value of the option to invest as well as the optimal exercise policy are solved by an approximate dynamic programming algorithm that relies on the independence of the state variables increments. We prove the convergence of our algorithm and derive a theoretical bound on how the errors compound as the number of stages of the pilot phase is increased. We implement the algorithm for a simplified version of the model where revenues are fixed, providing an economic interpretation of the effects of the main parameters driving the model. In particular, we explore how the value of the investment opportunity and the optimal investment threshold are affected by changes in market volatility, technical volatility, the learning coefficient, the drift rate of costs and the time to completion of a pilot stage.  相似文献   
62.
This paper reports results of research into the definition of requirements for new consumer products––specifically, electro-mechanical products. The research dealt with the derivation of design requirements that are demonstrably aligned with stakeholder needs. The paper describes a comprehensive process that can enable product development teams to deal with statements of product requirements, as originally collected through market research activities, in a systematic and traceable manner from the early, fuzzy front end, stages of the design process. The process described has been based on principles of systems engineering. A case study from its application and evaluation drawn from the power sector is described in this paper. The case study demonstrates how the process can significantly improve product quality planning practices through revision of captured product requirements, analysis of stakeholder requirements and derivation of design requirements. The paper discusses benefits and issues from the use of the process by product development teams, and identifies areas for further research. Finally, the conclusions drawn from the reported research are presented.
Vassilis AgouridasEmail:
  相似文献   
63.
Product development is an important but also dynamic, lengthy and risky phase in the life of a new product. The optimisation of the product development phase through extensive knowledge of the involved procedures is believed to reduce the risks and improve the final product quality. Artificial intelligence and expert systems have been used successfully in optimising the development phase of some new products as it will be demonstrated by the first sections of this publication. This paper presents the first module of an expert system, a neural network architecture that could predict the reliability performance of a vehicle at later stages of its life by using only information from a first inspection after the vehicle’s prototype production. The paper demonstrates how a tool like neural networks can be designed and optimised for use in reliability performance predictions. Also, this paper presents an optimisation methodology that enabled the neural network to deal with the limited amount of available training data, common during new product development, and to finally achieve acceptable prediction performance with small error. A case example is presented to demonstrate the methodology.  相似文献   
64.
Custom software development and maintenance is one of the key expenses associated with developing automated systems for mass customization. This paper presents a method for reducing the risk associated with this expense by developing a flexible environment for determining and executing dynamic workflow paths. Strategies for developing an autonomous agent-based framework and for identifying and creating web services for specific process tasks are presented. The proposed methods are outlined in two different case studies to illustrate the approach for both a generic process with complex workflow paths and a more specific sequential engineering process.  相似文献   
65.
The identification of part families and machine groups that form the cells is a major step in the development of a cellular manufacturing system and, consequently, a large number of concepts, theories and algorithms have been proposed. One common assumption for most of these cell formation algorithms is that the product mix remains stable over a period of time. In today’s world, the market demand is being shaped by consumers resulting in a highly volatile market. This has given rise to a new class of products characterized by low volume and high variety. To incorporate product mix changes into an existing cellular manufacturing system many important issues have to be tackled. In this paper, a methodology to incorporate new parts and machines into an existing cellular manufacturing system has been presented. The objective is to fit the new parts and machines into an existing cellular manufacturing system thereby increasing machine utilization and reducing investment in new equipment.  相似文献   
66.
基于PDM的FRACAS平台研究   总被引:1,自引:0,他引:1       下载免费PDF全文
协同产品研制模式对故障报告、分析和纠正措施系统(FRACAS)提出了异构信息管理、分布式闭环控制和多级安全管理的新需求。该文构建基于产品数据管理(PDM)的FRACAS平台体系结构,论述该系统的实现方法,包括基于PDM的系统开发技术以及配置技术,并建立了原型系统。  相似文献   
67.
Standardisation initiatives (ISO and IEC) try to answer the problem of managing heterogeneous information, scattered within organizations, by formalising the knowledge related to products technical data. While the product is the centred object from which, along its lifecycle, all enterprise systems, either inside a single enterprise or between cooperating networked enterprises, have a specific view, we may consider it as active as far as it participates to the decisions making by providing knowledge about itself. This paper proposes a novel approach, postulating that the product, represented by its technical data, may be considered as interoperable per se with the many applications involved in manufacturing enterprises as far as it embeds knowledge about itself, as it stores all its technical data, provided that these are embedded on a common model. The matter of this approach is to formalise of all technical data and concepts contributing to the definition of a Product Ontology, embedded into the product itself and making it interoperable with applications, minimising loss of semantics.  相似文献   
68.
A recent focus is on creating engaging user experiences with digital products and services such as voicemail. This study aims to design towards increased levels of engagement in voicemail browsing by using the ‘Richness, Control and Engagement’ (RC & E) framework. This framework explains the levels of engagement in terms of the levels of richness and control that are shaped by the features of a product and the user’s expertise. A product was developed that utilized gestures and sound to access digital voicemail contents. An experiment was conducted in which 28 participants interacted with the product while varying (1) the number of features of the user interface, (2) the amount of voicemail content and (3) the type of task. Results showed that the levels of engagement could be predicted according to the levels of richness and control experienced when a task-term was added to the framework. Implications of the refined RC & E framework for interaction design practice are discussed.  相似文献   
69.
With the rapid popularity of multi-camera networks, one human action is usually captured by multiple cameras located at different angles simultaneously. Multi-camera videos contain the distinct perspectives of one action, therefore multiple views can overcome the impacts of illumination and occlusion. In this paper, we propose a novel multi-camera video clustering model, named Shareability-Exclusivity Representation on Product Grassmann Manifolds (PGM-SER), to address two key issues in traditional multi-view clustering methods (MVC): (1) Most MVC methods directly construct a shared similarity matrix by fusing multi-view data or their corresponding similarity matrices, which ignores the exclusive information in each view; (2) Most MVC methods are designed for multi-view vectorial data, which cannot handle the nonlinear manifold structure hidden in multi-camera videos. The proposed PGM-SER firstly adopts Product Grassmann Manifolds to represent multi-camera videos, then simultaneously learn their shared and exclusive information in global structures to achieve multi-camera video clustering. We provide an effective optimization algorithm to solve PGM-SER and present the corresponding convergence analysis. Finally, PGM-SER is tested on three multi-camera human action video datasets and obtain satisfied experimental results.  相似文献   
70.
产品细节形态设计探究   总被引:1,自引:1,他引:0  
王尧  杨随先  许安航  王瑞雪 《包装工程》2017,38(24):216-222
目的探究产品细节形态设计中的设计原则和方法。方法结合现有产品的调研汇总、基本模型的建立分析以及问卷调查的结果,对影响产品外观细节形态的两个基本要素——圆角和分割线的属性对产品视觉美感的影响进行研究,并给出相关实例验证。结论分析了产品细节形态中圆角和分割线两个视觉元素对产品视觉感受的影响,提出了在产品细节形态设计中合理设计圆角和分割线的原则和方法,给出了从圆角和分割线两个方面提升整体产品视觉美感的优化方案。  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