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   1505篇
  免费   172篇
  国内免费   4篇
电工技术   15篇
综合类   2篇
化学工业   440篇
金属工艺   15篇
机械仪表   39篇
建筑科学   58篇
矿业工程   2篇
能源动力   68篇
轻工业   271篇
水利工程   20篇
石油天然气   6篇
无线电   96篇
一般工业技术   213篇
冶金工业   73篇
原子能技术   4篇
自动化技术   359篇
  2024年   7篇
  2023年   25篇
  2022年   58篇
  2021年   105篇
  2020年   62篇
  2019年   78篇
  2018年   87篇
  2017年   87篇
  2016年   108篇
  2015年   64篇
  2014年   88篇
  2013年   138篇
  2012年   107篇
  2011年   142篇
  2010年   73篇
  2009年   71篇
  2008年   74篇
  2007年   62篇
  2006年   54篇
  2005年   34篇
  2004年   25篇
  2003年   20篇
  2002年   30篇
  2001年   8篇
  2000年   7篇
  1999年   11篇
  1998年   14篇
  1997年   10篇
  1996年   12篇
  1995年   3篇
  1994年   2篇
  1993年   4篇
  1990年   1篇
  1988年   2篇
  1987年   2篇
  1985年   3篇
  1981年   2篇
  1978年   1篇
排序方式: 共有1681条查询结果,搜索用时 15 毫秒
131.
132.
hapTEL, an interdisciplinary project funded by two UK research councils from 2007 to 2011, involves a large interdisciplinary team (with undergraduate and post-graduate student participants) which has been developing and evaluating a virtual learning system within an HE healthcare education setting, working on three overlapping strands. Strand 1 involves the technical development and evaluation of the hapTEL workstation which simulates clinical conditions for dental training including haptics (sense of touch). Strand 2 involves examining the traditional undergraduate curriculum and how this could benefit from the use of haptics. Strand 3 is concerned with the educational evaluation of the impact of the work carried out within Strands 1 and 2. Two theoretical frameworks (Entwistle, (1987) and Webb and Cox (2004)) have been used to identify as many factors as possible which could affect the impact of Technology Enhanced Learning (TEL) on the quality of the learning achieved. These frameworks have formed a foundation for measuring the impact of TEL on curriculum change, teachers’ pedagogical practices, students’ learning and on institutional practices. A range of quantitative and qualitative methods were designed, piloted and evaluated in order to measure the impact of TEL on teaching and learning; and to have a rich and robust data set which also addresses the variables in the frameworks. The results from using these frameworks show that institutional and departmental factors should be considered when evaluating the impact of TEL in higher education and that these had a major influence on the design and curriculum integration of the hapTEL systems. We have also shown that by involving the end users from the beginning enabled not only an enhancement of the students’ learning experiences but also a modification to the traditional curriculum itself and the successful integration of TEL within a very traditional undergraduate higher education dental curriculum. The conclusions from this paper confirm earlier reviews of researching TEL that technology integration is extremely complex and the related research requires a comprehensive approach of both quantitative and qualitative methods if one is to take account of the range of variables identified by theoretical frameworks. Finally, repeating the range of empirical investigations for a second year enables researchers to validate the effectiveness of the methods used in the initial year and thereby maximise the reliability and generalisability of the research outcomes.  相似文献   
133.
This work’s aim is to evaluate the importance of landscape in wine quality perception using a novel integrated approach based on two statistical techniques, i.e. choice-based conjoint analysis (Gustafsson et al., 2001) and combination-based permutation tests (Corain and Salmaso, 2004, Pesarin and Salmaso, 2009a). To this end we developed a preference choice experiment which was submitted to a sample of respondents during blind wine tasting meetings. The obtained results allow us to weigh up and emphasise the importance of an attractive landscape to the perception of a finer quality of wine. Indeed, we noticed that associating wine to an image of greater visual impact, i.e. an evocative landscape, induces a significantly higher preference for the tasted wine. Moreover, the integrated application of choice-based conjoint analysis and combination-based permutation tests allows us to identify the specific relationship each market segment has with landscape, price and wine quality.  相似文献   
134.
Statechart Diagrams provide a graphical notation for describing dynamic aspects of system behaviour within the Unified Modelling Language (UML). In this paper we present a translation from a subset of UML Statechart Diagrams - covering essential aspects of both concurrent behaviour, like sequentialisation, parallelism, non-determinism and priority, and state refinement - into PROMELA, the specification language of the SPIN model checker. SPIN is one of the most advanced analysis and verification tools available nowadays. Our translation allows for the automatic verification of UML Statechart Diagrams. The translation is simple, proven correct, and promising in terms of state space representation efficiency. Received September 1999 / Accepted in revised form February 2000  相似文献   
135.
本文针对昆明的发展特征及面临的挑战,引入了一种全覆盖的综合规划方法来从整体上协调空间的各种职能及保护自然潜力.对大昆明区采用基于GIS的区域模型模拟了这些政策和方法的潜在影响力.结果显示,污染减少、土地利用成本和基础设施的建设成本降低,同时城市的竞争力提高.  相似文献   
136.
The main purpose of this work was to study mordenite synthesis using kaolin as a Si and Al source. The influence of crystallization time and seed addition were studied. The obtained zeolites were characterized by: XRD, SEM, nitrogen adsorption and chemical analysis. Kaolin showed to be a promising source of Si and Al for mordenite synthesis. Seed addition led to more highly crystalline phases. Kaolin yielded mordenite whereas ZSM-5 was obtained from calcined kaolin. Longer synthesis times and seed addition favored mordenite formation.  相似文献   
137.
A distillation process for the production of hyperazeotropic ethanol from a dilute wine obtained from the fermentation of biomass has been studied. This process utilizes the coupling of a soft preconcentration stage and of a dehydration stage based on the salting-out effect produced by calcium chloride on the ethanol in an aqueous solution, with the disappearance of the azeotrope. The salt is employed in a close cycle, due to the presence of a regeneration stage, therefore no consumption of calcium chloride is noticed.

The distillation process utilizes one column consisting of two sections operating at different pressures in order to reach an efficient heat recovery.

In this paper, a simplified flow-sheet of the process and the principal operating conditions of the distillation column are illustrated. When compared with other processes, conventional or under development, this one is characterized by the promising reduction of the specific energy requirement.

The operating conditions chosen for the distillation with salt have been experimentally checked using a laboratory column running continuously with calcium chloride as salting-out agent. Moreover, the experiments confirmed the reliability of the mathematical model of the process. Further experiments are in progress with the aim of utilizing a mixture of salts which can be fed from the bottom of the dehydration section back to the fermentor, so that the salt regeneration stage can be reduced.  相似文献   

138.
139.
Cooking Brassica vegetables as a domestic processing method has a great impact on health-promoting bioactive compounds: glucosinolates (GLS), flavonoids, hydroxycinnamic acids, and vitamin C. In Galicia (NorthWestern Spain), one of the most consumed horticultural crops is Brassica rapa, by using the leaves (turnip greens) and the young sprouting shoots (turnip tops) in different culinary preparations. In order to determine the effect of cooking, on turnip greens and turnip tops, bioactive GLS, flavonoids, hydroxycinnamic acids and vitamin C were analysed and simultaneously determined. The level of retention of each individual compound after cooking procedures was evaluated in the edible organs, and also in the cooking water, in order to compare their composition to a fresh uncooked control. Steaming, conventional boiling, and high-pressure cooking, traditional processing methods of this kind of vegetables, were the three domestic processing methods used in this work. Results showed that total GLS and phenolics were significantly affected by the cooking procedure and the loss rate varied among individual compounds. Steaming was the method that better preserved GLS and phenolic compounds. Conventional boiling and high-pressure cooking methods presented similar rate of losses of total GLS content (64%) and total phenolic content (more than 70%). Degradation among glucosinolate classes, aliphatic or indolic, was similar. The total flavonoids lost in turnip greens were 64% and 67% for conventional boiling and high-pressure, respectively. The main losses were caused by leaching into the cooking water. The concentration of vitamin C suffered a drastic loss in the process of sample handling and after cooking. Despite the fact that any cooking procedure affected negatively the nutritional composition of the turnip greens and tops, our results showed high retentions of individual compounds in steaming, and the lowest retentions were obtained in the traditional high-pressure cooking. High retention of health-promoting compounds in the cooking water should be considered for increasing the intake of properties of B. rapa.  相似文献   
140.
The Teleo-Reactive approach designed by N. J. Nilsson offers a high-level programming model for the development of reactive systems such as robotic vehicles. Teleo-Reactive programs are written in a way that allows engineers to define behaviour taking account of goals and changes in the state of the environment. Since Nilsson’s original definition, published in 1994, various researchers have used the Teleo-Reactive paradigm, either applied to a particular domain or extended by adding more capabilities to the original definition. This article provides a systematic literature review of 53 previous Teleo-Reactive-based studies in journals, conference proceedings and the like. The aim of this paper is to identify, appraise, select and synthesize all this high-quality research evidence relating to the use of the Teleo-Reactive paradigm. The literature has been systematically reviewed to offer an overview of the present state of this field of study and identify the principal results that have been obtained thanks to the Teleo-Reactive approach. Finally, this article details the challenges and difficulties that have to be overcome to ensure further advances in the use of this technique.  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