全文获取类型
收费全文 | 321632篇 |
免费 | 37906篇 |
国内免费 | 26691篇 |
专业分类
电工技术 | 29041篇 |
技术理论 | 6篇 |
综合类 | 33675篇 |
化学工业 | 40173篇 |
金属工艺 | 21686篇 |
机械仪表 | 23103篇 |
建筑科学 | 25107篇 |
矿业工程 | 11015篇 |
能源动力 | 8135篇 |
轻工业 | 37852篇 |
水利工程 | 11208篇 |
石油天然气 | 10381篇 |
武器工业 | 4356篇 |
无线电 | 34795篇 |
一般工业技术 | 28283篇 |
冶金工业 | 11283篇 |
原子能技术 | 5364篇 |
自动化技术 | 50766篇 |
出版年
2024年 | 1448篇 |
2023年 | 5254篇 |
2022年 | 12227篇 |
2021年 | 15869篇 |
2020年 | 11578篇 |
2019年 | 8191篇 |
2018年 | 8508篇 |
2017年 | 9659篇 |
2016年 | 8913篇 |
2015年 | 14073篇 |
2014年 | 18070篇 |
2013年 | 21685篇 |
2012年 | 26782篇 |
2011年 | 28151篇 |
2010年 | 26651篇 |
2009年 | 25487篇 |
2008年 | 26003篇 |
2007年 | 25342篇 |
2006年 | 22143篇 |
2005年 | 18045篇 |
2004年 | 13256篇 |
2003年 | 9067篇 |
2002年 | 8371篇 |
2001年 | 7676篇 |
2000年 | 5885篇 |
1999年 | 2571篇 |
1998年 | 938篇 |
1997年 | 745篇 |
1996年 | 602篇 |
1995年 | 449篇 |
1994年 | 341篇 |
1993年 | 333篇 |
1992年 | 314篇 |
1991年 | 231篇 |
1990年 | 187篇 |
1989年 | 194篇 |
1988年 | 132篇 |
1987年 | 103篇 |
1986年 | 101篇 |
1985年 | 65篇 |
1984年 | 57篇 |
1983年 | 62篇 |
1982年 | 43篇 |
1981年 | 55篇 |
1980年 | 109篇 |
1979年 | 62篇 |
1965年 | 15篇 |
1964年 | 10篇 |
1959年 | 58篇 |
1951年 | 59篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
101.
Baizhan Li Chenqiu Du Hong Liu Wei Yu Jie Zheng Meilan Tan Zhenxing Jin Wenjie Li Jing Wu Lu Chen Runming Yao 《Indoor air》2019,29(2):308-319
The extensive research interests in environmental temperature can be linked to human productivity / performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature‐sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects’ SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S‐shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C‐24.59°C, while tended to be stable beyond that. The subjects’ thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature‐invoked risks to human health and well‐being. 相似文献
102.
Neural Processing Letters - The beta processes (BP) is a powerful nonparametric tool in feature learning, which is often used as the prior of Bernoulli process for choosing features from a feature... 相似文献
103.
中国调频频段数字音频广播(CDR)激励器及发射机测试标准已正式发布.CDR采用的是数模同播技术,相关指标测试方法比较复杂,具体测试步骤也较抽象.这里将实际测试积累的一些经验和技巧结合标准内容进行阐述,不但可提高测试效率也能帮助大家比较直观和深入的理解标准内容. 相似文献
104.
105.
介绍了PET熔体长距离输送工艺流程,重点分析易对PET熔体输送带来不利影响的因素,如熔体压力降、停留时间、管道粗糙度、焊缝品质等,并针对熔体输送的不利因素,提出了相应的解决方案,对熔体直纺设计、实践提供必要的参考。 相似文献
106.
以2,6-二甲基苯胺为原料,通过重氮化反应制备2,6-二甲基苯腈,经水蒸汽蒸馏法提纯后,采用75%硫酸酸化,再经酸碱法对产物进行脱色和纯化得产物2,6-二甲基苯甲酸,总收率68.4%。工艺简单、操作安全、适合工业化生产。 相似文献
107.
Zhen Wu Jing Yao Pengfei Zhu Fusheng Yang Xiangyu Meng Sandra Kurko Zaoxiao Zhang 《International Journal of Hydrogen Energy》2021,46(19):11183-11198
Advanced biogas power generation technology has been attracting attentions, which contributes to the waste disposal and the mitigation of greenhouse gas emissions. This work proposes and models a novel biogas-fed hybrid power generation system consisting of solid oxide fuel cell, water gas shift reaction, thermal swing adsorption and proton exchange membrane fuel cell (SOFC-WGS-TSA-PEMFC). The thermodynamic, exergetic, and thermo-economic analyses of this hybrid system for power generation were conducted to comprehensively evaluate its performance. It was found that the novel biogas-fed hybrid system has a gross energy conversion efficiency of 68.63% and exergy efficiency of 65.36%, indicating high efficiency for this kind of hybrid power technology. The market sensitivity analysis showed that the hybrid system also has a low sensitivity to market price fluctuation. Under the current subsidy level for the distributed biogas power plant, the levelized cost of energy can be lowered to 0.02942 $/kWh for a 1 MW scale system. Accordingly, the payback period and annual return on investment can reach 1.4 year and about 20%, respectively. These results reveal that the proposed hybrid system is promising and economically feasible as a distributed power plant, especially for the small power scale (no more than 2 MW). 相似文献
108.
109.
110.