首页 | 官方网站   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   231913篇
  免费   3567篇
  国内免费   668篇
工业技术   236148篇
  2021年   2777篇
  2020年   2057篇
  2019年   2578篇
  2018年   4327篇
  2017年   4440篇
  2016年   4690篇
  2015年   2756篇
  2014年   4597篇
  2013年   10071篇
  2012年   6837篇
  2011年   8708篇
  2010年   6938篇
  2009年   7613篇
  2008年   7632篇
  2007年   7378篇
  2006年   6286篇
  2005年   5874篇
  2004年   5481篇
  2003年   5308篇
  2002年   5115篇
  2001年   5129篇
  2000年   4682篇
  1999年   4679篇
  1998年   12067篇
  1997年   8414篇
  1996年   6346篇
  1995年   4703篇
  1994年   4038篇
  1993年   4338篇
  1992年   3185篇
  1991年   3256篇
  1990年   3100篇
  1989年   3032篇
  1988年   3058篇
  1987年   2654篇
  1986年   2715篇
  1985年   3028篇
  1984年   2813篇
  1983年   2640篇
  1982年   2411篇
  1981年   2383篇
  1980年   2456篇
  1979年   2447篇
  1978年   2436篇
  1977年   2611篇
  1976年   3085篇
  1975年   2259篇
  1974年   2100篇
  1973年   2199篇
  1972年   1962篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Based on the phase transformation theories, especially the T0 concept of bainite transformation, alloy optimisation of bainitic steel with carbides has been carried out aiming at the produce of plastic mould with large cross-section. The effect of manganese and silicon on proeutectoid ferrite and bainite transformation is explored by dilatometric analysis, XRD and different microscopy techniques. The results show that after the alloy optimisation, the transformation of proeutectoid ferrite is suppressed and when the cooling rate is lower than 0·1°C?s??1, the new lower bainite transformation appears by decreasing carbon capacity of austenite and promoting carbide precipitation. Industrial production proves that the optimised alloy SDP1 can meet the demand for the plastic mould with the thickness of 1050?mm.  相似文献   
142.
Personal and Ubiquitous Computing - This article presents a study concerning the evaluation of a smart home control system for elderly people with a sample of 10 users in a city in the interior of...  相似文献   
143.
Journal of Computer and Systems Sciences International - The height of a building is a basic characteristic needed for analytical services. It can be used to evaluate the population and functional...  相似文献   
144.
145.
An experimental methodology for inferring brine dissolution rate in monoethylene glycol (MEG) solutions at different temperatures using a webcam combined with a mathematical model is presented. The measurement system is designed to track the RGB (red, green, and blue) colour variations during the dissolution process. A dynamic model augmented with the population balance equation is applied to describe the dissolution process. Moreover, the dissolution rate is consistently related to the temperature and MEG concentration through the driving force based on the Gibbs energy and chemical affinity. The applied low-cost measurement apparatus proved to be a useful resource for tracking the dissolution dynamics in a wide range of undersaturation.  相似文献   
146.
Protection of Metals and Physical Chemistry of Surfaces - The possibility is shown of creating a chart of local corrosion damage in the walls of heat-exchange tubes on the basis of the data of...  相似文献   
147.
Successful fabrication of glass-based hybrid nanocomposites (GHNCs) incorporating Ag, core-shell CdSe/CdS and CdSxSe1?x nanoparticles (NPs) is herein reported. Both metallic (Ag) and semiconductor (CdSe/CdS) NPs were pre-synthesized, suspended in colloids and added into the sol-gel reaction medium which was used to fabricate the GHNCs. During fabrication of the nanocomposites a fraction (20–60%) of core-shell CdSe/CdS NPs was alloyed into CdSxSe1?x (0.20 < x < 0.35) NPs without changing morphology. Modulation of in situ alloying is possible via the relative content of organics added into the sol-gel protocol. Within colloids Ag (core-shell CdSe/CdS) NPs presented average diameter and polydispersity index of 49.5 nm (4.2 nm) and 0.41 (0.21), respectively. On the other hand, the Ag (core-shell CdSe/CdS) NPs’ average diameter and polydispersity index assessed from the GHNCs were respectively 51.5 nm (4.1 nm) and 0.43 (0.25), revealing negligible aggregation of the nanophases within the glass template. The new GHNCs herein introduced presented two independent excitonic transitions associated to homogenously dispersed semiconductor NPs, peaking around 420 nm (core-shell CdSe/CdS) and 650 nm (CdSxSe1?x) and matching the plasmonic resonance (Ag NPs) in the 400–500 nm range. We envisage that the new GHNCs represent very promising candidates for superior light manipulation while illuminated with multiple laser beams in quantum interference-based devices.  相似文献   
148.
149.
150.
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-23

京公网安备 11010802026262号