全文获取类型
收费全文 | 231913篇 |
免费 | 3567篇 |
国内免费 | 668篇 |
学科分类
工业技术 | 236148篇 |
出版年
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.
Tsuchiya Letícia Diniz Braga Lucas Fiorini de Faria Oliveira Otávio de Bettio Raphael Winckler Greghi Juliana Galvani Freire André Pimenta 《Personal and Ubiquitous Computing》2021,25(2):281-295
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.
Trekin A. N. Ignatiev V. Yu. Yakubovskii P. Ya. 《Journal of Computer and Systems Sciences International》2020,59(5):755-767
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.
Ricardo Cambraia Parreira Diana Paola Gmez‐Mendoza Itamar Couto Guedes de Jesus Rafael Pereira Lemos Anderson Kennedy Santos Cristiana Perdigo Rezende Henrique Csar Pereira Figueiredo Mauro Cunha Xavier Pinto Frank Kjeldsen Silvia Guatimosim Rodrigo Ribeiro Resende Thiago Verano‐Braga 《Proteomics. Clinical applications》2020,14(4)
145.
Caio Felippe Curitiba Marcellos Camila M. Senna Figueiredo Frederico W. Tavares Maurício Bezerra de Souza Jr. Paulo Laranjeira da Cunha Lage João Francisco Cajaiba da Silva Argimiro R. Secchi Amaro G. Barreto Jr. 《加拿大化工杂志》2020,98(11):2435-2450
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.
Golovin V. A. Pechnikov N. V. Shchelkov V. A. Tsivadze A. Yu. 《Protection of Metals and Physical Chemistry of Surfaces》2018,54(6):1221-1232
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.
L.C. Souza A.C.A. Silva N.O. Dantas P.C. Morais S.W. da Silva 《Ceramics International》2018,44(1):208-215
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.