全文获取类型
收费全文 | 499篇 |
免费 | 21篇 |
国内免费 | 29篇 |
专业分类
电工技术 | 12篇 |
综合类 | 14篇 |
化学工业 | 40篇 |
金属工艺 | 115篇 |
机械仪表 | 22篇 |
建筑科学 | 19篇 |
矿业工程 | 3篇 |
能源动力 | 16篇 |
轻工业 | 18篇 |
石油天然气 | 18篇 |
武器工业 | 4篇 |
无线电 | 46篇 |
一般工业技术 | 56篇 |
冶金工业 | 51篇 |
原子能技术 | 10篇 |
自动化技术 | 105篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 14篇 |
2021年 | 22篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 10篇 |
2014年 | 24篇 |
2013年 | 26篇 |
2012年 | 31篇 |
2011年 | 33篇 |
2010年 | 39篇 |
2009年 | 32篇 |
2008年 | 32篇 |
2007年 | 52篇 |
2006年 | 27篇 |
2005年 | 22篇 |
2004年 | 19篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 18篇 |
2000年 | 17篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 6篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有549条查询结果,搜索用时 11 毫秒
541.
542.
543.
544.
采用热膨胀法结合显微金相与硬度法,在LINSEIS L78 RITA相变仪上测定了55Si Cr A弹簧钢的临界点温度和连续冷却转变曲线,研究了冷却速度对组织和硬度的影响规律。在此基础上,进行了控轧控冷工业试验。结果表明,当冷速≤2℃/s时,转变产物为少量铁素体、珠光体,珠光体硬度随冷速增大而增大;当冷速≥5℃/s时,转变产物为珠光体、马氏体;当冷速≥20℃/s时,转变产物为马氏体,硬度随冷速增大而增大;现场控轧控冷的试验钢抗拉强度达到1 163 MPa,伸长率为13%,面缩率为49%,综合力学性能良好,满足了用户的使用要求。 相似文献
545.
Hatem M. Bahig 《Computing》2006,78(2):161-172
An addition chain for a natural number n is a sequence 1=a
0<a
1< . . . <a
r
=n of numbers such that for each 0<i≤r, a
i
=a
j
+a
k
for some 0≤k≤j<i. An improvement by a factor of 2 in the generation of all minimal (or one) addition chains is achieved by finding sufficient
conditions for star steps, computing what we will call nonstar lower bound in a minimal addition and omitting the sorting step. 相似文献
546.
547.
548.
New digital technologies help to curtail those that are carbon intensive but are accompanied by CO2 emissions due to their own energy demand. Whether digitalization relates to increased or decreased carbon emissions may depend on the sophistication of an economy's research and development (R&D) output. This study explores the R&D-induced regime transition that governs the relationship between digitalization and CO2 emissions. The study seeks evidence of the environmental Kuznets curve hypothesis and tests it with a panel smooth transition regression (PSTR). Employing this estimator with two R&D output regimes makes it possible to account for year- and country-varying effects of digitalization, human capital, and country income level on CO2 emission. The research covers 55 high- and middle-income economies from 1996 to 2019. The paper finds that the transition process is driven by R&D output level – measured in technology patents per country inhabitants. The findings support the environmental Kuznets curve hypothesis and confirm that CO2 emissions have an inverted U-shaped relationship with digitalization and income level. This nonlinear relationship transitions smoothly in the exogenous R&D output level. The digitalization indicator in the lower R&D regime has a significant point estimate of 0.07; in the higher regime, the estimate is −0.14. The R&D output threshold at which the transition function switches between the two regimes corresponds to a level of 39.9 technology patents per million inhabitants. 相似文献
549.
Many older adults find it difficult to accept new forms of information and communication technology (ICT), despite its advantages such as convenience and efficiency. It is necessary to identify the reasons for low ICT use among older people—even among those with positive attitudes toward ICT—to help older adults cope with social changes and bridge the digital divide. This study explored technology acceptance and related factors among older Korean adults living in rural areas. Based on an existing model (the senior technology acceptance model), a new conceptual framework for technology acceptance was proposed, and the framework was tested using pathway analysis. Semi-structured interviews were conducted in three focus groups (n = 15), and a survey questionnaire was administered to older Korean adults living in a rural area (n = 233) from 17 January 2021 to 18 February 2021. Qualitative data were analyzed using directed content analysis, and quantitative data were analyzed using pathway analysis. Four categories, 11 subcategories, and 18 codes were identified, and a new conceptual framework was proposed based on the qualitative findings. The results of the model revealed significant positive direct paths from external controls (β = 0.45, p < .001), attitudinal beliefs (β = 0.33, p < .001), and cognitive health (β = 0.10, p = .040) to internal abilities. It is necessary to develop and apply a targeted and tailored ICT education program to improve self-efficacy and reduce anxiety regarding technology use among older Korean adults living in rural areas. 相似文献