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   3764篇
  免费   299篇
  国内免费   9篇
电工技术   43篇
综合类   2篇
化学工业   1008篇
金属工艺   60篇
机械仪表   107篇
建筑科学   99篇
矿业工程   6篇
能源动力   190篇
轻工业   531篇
水利工程   34篇
石油天然气   14篇
无线电   263篇
一般工业技术   680篇
冶金工业   108篇
原子能技术   31篇
自动化技术   896篇
  2024年   4篇
  2023年   51篇
  2022年   130篇
  2021年   195篇
  2020年   139篇
  2019年   137篇
  2018年   156篇
  2017年   152篇
  2016年   179篇
  2015年   127篇
  2014年   195篇
  2013年   303篇
  2012年   250篇
  2011年   330篇
  2010年   211篇
  2009年   224篇
  2008年   187篇
  2007年   172篇
  2006年   126篇
  2005年   126篇
  2004年   77篇
  2003年   65篇
  2002年   69篇
  2001年   49篇
  2000年   40篇
  1999年   30篇
  1998年   35篇
  1997年   25篇
  1996年   37篇
  1995年   26篇
  1994年   18篇
  1993年   11篇
  1992年   13篇
  1991年   22篇
  1990年   10篇
  1989年   11篇
  1988年   12篇
  1987年   6篇
  1986年   12篇
  1985年   14篇
  1984年   16篇
  1983年   14篇
  1982年   12篇
  1981年   8篇
  1980年   8篇
  1979年   9篇
  1977年   6篇
  1975年   5篇
  1973年   6篇
  1972年   3篇
排序方式: 共有4072条查询结果,搜索用时 15 毫秒
951.
952.
The objective of this work was to study the effects of the combination of glucose oxidase (Gox), α‐amylase (AM) and xylanase (Xyl) on dough properties and bread quality, applying response surface analysis. Gox improved dough stickiness and bread crumb uniformity, but had a negative effect on specific volume. A positive synergist effect was observed combining Xyl and AM on specific volume and crumb firmness but this synergist effect was negative on crumb uniformity. Using the ‘desirability function’, two optimal formulations for the baking process were obtained. In the first optimisation, the combination of Gox 0.0026, Xyl 0.016 and AM 0.01 g per 100 g of flour will allow to obtain breads with high specific volume and low firmness. Second optimisation (Gox 0.0037, Xyl 0.0089 and AM 0.0105 g per 100 g of flour) will allow to obtain breads with 37% higher specific volume than control and, additionally, with low dough stickiness.  相似文献   
953.
In the last few years Cupressus sempervirens has been identified as the cause of an increasing number of cases of late winter-early spring pollinosis in Mediterranean countries. We conducted a 4-year retrospective study of a large group of subjects with documented allergic respiratory disease in order to determine the prevalence, clinical significance and annual rate of sensitization to C. sempervirens pollen. Anamnestic data and skin prick tests (SPT) with common aeroallergens and C. sempervirens extract were collected from 1397 subjects (712 male and 685 female) resident in Latium, a region in central Italy, with complaints related to upper- or lower-respiratory-tract disorders or conjunctival disease. Two hundred and forty-three subjects (17.4%) showed positive results to C. sempervirens extract; 47 (19.3%) of them were monosensitized. The annual sensitization rate of SPT positivity to C. sempervirens varied from 7.2% in 1995 to 22% in 1998. All the subjects monosensitized to cypress pollen had symptoms from January through April. Our study suggests that sensitivity to C. sempervirens is responsible for respiratory symptoms in an increasing percentage of subjects. Further studies are needed to determine its frequency at the national level.  相似文献   
954.
The microstructural transformation of ferrite into secondary austenite and sigma phase during long term exposure to high-temperatures (650–900 °C) in a 2205 duplex stainless steel has been investigated using the thermoelectric power (TEP) technique, scanning electron microscopy (SEM), Charpy-impact test (CIT), equivalent ferrite and sigma phases content measurements. The possibility of using the TEP coefficient as a nondestructive assessment technique to characterize the aging kinetics of 2205 duplex stainless steel is discussed. Experimental results indicate that TEP coefficient is sensitive to the gradual microstructural transformation of ferrite phase experienced by the 2205 duplex stainless steel during the aging treatments.  相似文献   
955.
956.
In this paper we analyze the graphical methods employed in the stonecutting treatises from that of De l’Orme, published during the sixteenth century, to De La Rue’s Traité de la coupe des pierres, published in 1728. We will deal with the graphical means that made possible an epistemological shift between treatises of the sixteenth century, written for practising stonecutting masons in a period where the subject was covered by a veil of secrecy, which in some specific cases included a very intuitive form of representation, “protoaxonometries”, and eighteenth-century treatises, which show a clear scientific and pedagogical approach to the geometrical problems posed by stonecutting.  相似文献   
957.
This paper describes research into adequately estimating the main variables of a thermochemical gas nitriding process of stainless steel parts for engine components. The paper lays out an experimental strategy for the nitriding process that optimizes a set of variables that have a bearing on the occurrence of nitriding cracks. The results demonstrate that several factors and interactions are relevant in the occurrence of nitriding cracks. The proposed strategy was found to be effective at achieving continuous improvement and stricter control.  相似文献   
958.
959.
The ordered growth of self-assembled SiGe islands by surface thermal diffusion in ultra high vacuum from a lithographically etched Ge stripe on pit-patterned Si(100) surface has been experimentally investigated. The total surface coverage of Ge strongly depends on the distance from the source stripe, as quantitatively verified by Scanning Auger Microscopy. The size distribution of the islands as a function of the Ge coverage has been studied by coupling atomic force microscopy scans with Auger spectro-microscopy data. Our observations are consistent with a physical scenario where island positioning is essentially driven by energetic factors, which predominate with respect to the local kinetics of diffusion, and the growth evolution mainly depends on the local density of Ge atoms.  相似文献   
960.
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