全文获取类型
收费全文 | 318193篇 |
免费 | 3306篇 |
国内免费 | 1296篇 |
专业分类
电工技术 | 6610篇 |
综合类 | 341篇 |
化学工业 | 44931篇 |
金属工艺 | 17159篇 |
机械仪表 | 12934篇 |
建筑科学 | 7595篇 |
矿业工程 | 1262篇 |
能源动力 | 6924篇 |
轻工业 | 25262篇 |
水利工程 | 2950篇 |
石油天然气 | 2854篇 |
武器工业 | 3篇 |
无线电 | 38087篇 |
一般工业技术 | 64438篇 |
冶金工业 | 55989篇 |
原子能技术 | 4927篇 |
自动化技术 | 30529篇 |
出版年
2021年 | 1564篇 |
2019年 | 1424篇 |
2018年 | 11009篇 |
2017年 | 11603篇 |
2016年 | 7248篇 |
2015年 | 2458篇 |
2014年 | 3248篇 |
2013年 | 10848篇 |
2012年 | 8125篇 |
2011年 | 16343篇 |
2010年 | 14467篇 |
2009年 | 13982篇 |
2008年 | 14195篇 |
2007年 | 16369篇 |
2006年 | 7107篇 |
2005年 | 10245篇 |
2004年 | 8257篇 |
2003年 | 7878篇 |
2002年 | 6874篇 |
2001年 | 6434篇 |
2000年 | 5927篇 |
1999年 | 6435篇 |
1998年 | 16562篇 |
1997年 | 11598篇 |
1996年 | 8960篇 |
1995年 | 6699篇 |
1994年 | 5934篇 |
1993年 | 5750篇 |
1992年 | 4066篇 |
1991年 | 4016篇 |
1990年 | 3582篇 |
1989年 | 3504篇 |
1988年 | 3447篇 |
1987年 | 2907篇 |
1986年 | 2842篇 |
1985年 | 3413篇 |
1984年 | 3050篇 |
1983年 | 2743篇 |
1982年 | 2547篇 |
1981年 | 2568篇 |
1980年 | 2430篇 |
1979年 | 2271篇 |
1978年 | 2235篇 |
1977年 | 2808篇 |
1976年 | 4171篇 |
1975年 | 1899篇 |
1974年 | 1795篇 |
1973年 | 1783篇 |
1972年 | 1460篇 |
1971年 | 1317篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
15.
16.
17.
18.
ABSTRACT The concept of digital game-based learning (DGBL) evolves rapidly together with technological enhancements of virtual reality (VR) and smart phones. However, the mental workload (MWL) that VR-training applications demand and motivational qualities originating from user experience (UX) should be identified in order to create effective and enjoyable training/learning challenges that fit with individual users’ capabilities. This study examined the effects of reality-based interaction (RBI) and VR on measures of student motivation and MWL, in a mental arithmetic game for secondary school pupils. In a randomised controlled trial with sixty school children, a mental arithmetic game was tested with three different interaction and two different presentation methods – VR RBI, VR head-mounted-display tapping and tablet flick-gesture. Results found a significant effect of RBI on MWL but no differences in enjoyment of training were found between VR-experience and tablet training-experience. In fact, adding the gaming-context to the mental arithmetic task created an enjoyable, motivating experience regardless of presentation or interaction-style. 相似文献
19.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
20.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献