全文获取类型
收费全文 | 141393篇 |
免费 | 17206篇 |
国内免费 | 11181篇 |
专业分类
电工技术 | 12366篇 |
技术理论 | 3篇 |
综合类 | 14589篇 |
化学工业 | 18452篇 |
金属工艺 | 9561篇 |
机械仪表 | 9768篇 |
建筑科学 | 11050篇 |
矿业工程 | 6014篇 |
能源动力 | 3896篇 |
轻工业 | 15641篇 |
水利工程 | 4113篇 |
石油天然气 | 5704篇 |
武器工业 | 2173篇 |
无线电 | 15190篇 |
一般工业技术 | 12587篇 |
冶金工业 | 5585篇 |
原子能技术 | 2070篇 |
自动化技术 | 21018篇 |
出版年
2024年 | 971篇 |
2023年 | 2960篇 |
2022年 | 6290篇 |
2021年 | 7978篇 |
2020年 | 5665篇 |
2019年 | 4200篇 |
2018年 | 4357篇 |
2017年 | 4928篇 |
2016年 | 4276篇 |
2015年 | 6848篇 |
2014年 | 8159篇 |
2013年 | 9289篇 |
2012年 | 11721篇 |
2011年 | 12074篇 |
2010年 | 11027篇 |
2009年 | 10523篇 |
2008年 | 10462篇 |
2007年 | 9977篇 |
2006年 | 8568篇 |
2005年 | 6847篇 |
2004年 | 5100篇 |
2003年 | 3862篇 |
2002年 | 3888篇 |
2001年 | 3343篇 |
2000年 | 2462篇 |
1999年 | 1206篇 |
1998年 | 521篇 |
1997年 | 425篇 |
1996年 | 338篇 |
1995年 | 294篇 |
1994年 | 227篇 |
1993年 | 196篇 |
1992年 | 154篇 |
1991年 | 116篇 |
1990年 | 89篇 |
1989年 | 60篇 |
1988年 | 64篇 |
1987年 | 47篇 |
1986年 | 45篇 |
1985年 | 22篇 |
1984年 | 19篇 |
1983年 | 15篇 |
1982年 | 25篇 |
1981年 | 25篇 |
1980年 | 44篇 |
1979年 | 23篇 |
1978年 | 1篇 |
1959年 | 18篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Xin Li Yurui Wang Minxuan Xu Yueqin Shi Hemiao Wang Xin Yang Haoting Ying Qi Zhang 《应用聚合物科学杂志》2021,138(19):50406
Polymer electrets have revealed great potential application in electromechanical devices because of the low weight, large quasi-piezoelectric sensitivity, and excellent flexibility. For an electret, a permanent and macroscopic electric field exists on the surface, principally led by a macroscopic electrostatic charge on the surface or a net orientation of polar groups inside the object. Here, progress in the development of polymer electrets is reviewed. After a brief retrospect of the research courses and those typical polymer electrets that are classified into fluorine polymer and nonfluorine polymer, we present a survey on the charging methods, including corona, soft X-ray, contact, thermal and monoenergetic particle beams. The latest representative applications (i.e., power harvesting, sensors, field effect transistors, and biomedicine) based on polymer electrets are also summarized. Finally, we complete this review with a discussion on perspectives and challenges in this field. 相似文献
3.
急性下壁心肌梗死是一种病发急、进展快、致死率高的心脏疾病,该文提出一种新颖的基于形态特征提取的BiLSTM神经网络分类的急性下壁心肌梗死辅助诊断算法,可大幅度提高医生对急性下壁心肌梗死疾病的诊断效率并有助于及时确诊.算法包括:对胸痛中心数据库心拍信号进行降噪及心拍分割;根据临床心内科医学诊断指南提取了12导联波形距离特征和分导联波形幅值特征;依据提取的特征搭建LSTM与BiLSTM神经网络进行心拍的分类识别;使用PTB公开数据库和胸痛中心数据库多临床中心进行交叉验证.实验结果表明,加入胸痛中心真实临床数据后,基于形态特征提取BiLSTM神经网络的急性下壁心肌梗死辅助诊断算法准确率达到99.72%,精度达到99.53%,灵敏度达到100.00%,同时F1-Score达到99.76.该算法比其他现有算法准确率提高至少1%,该项研究具有非常重要的临床应用价值. 相似文献
4.
6.
7.
Shilin Du Yichen Dong Feiqiang Guo Beile Tian Songbo Mao Lin Qian Chengyun Xin 《International Journal of Hydrogen Energy》2021,46(27):14138-14147
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications. 相似文献
8.
9.
Sun Xiaohao Miao Linchang Wang Hengxing Chen Runfa Guo Xin 《Bulletin of Engineering Geology and the Environment》2021,80(6):4957-4966
Bulletin of Engineering Geology and the Environment - Bio-cementation is currently applied to solidify sandy soils, but only few studies use it to cement loess soil particles. In this study, the... 相似文献
10.
Zhenkun Ke Xin Cao Chuanli Shan Lifen Shi Pingping Wang Yong Yang Fengyang Zhao Jiedong Cui Jinwei Li Gang Zhou Min Guan Tao Yu 《Ceramics International》2021,47(14):19605-19613
The purpose of the current work was to research the effect of alkali metal oxide on the structure, thermal properties, viscosity and chemical stability in the glass system (R2O–CaO–B2O3–SiO2) systematically. Because the glass would emulsify when Li2O was added to the glass batch, this article did not discuss Li2O. The results showed that when the amount of Na2O was less than 4 mol.%, there was a higher interconnectivity of borate and silicate sub-networks in glass, as more mixed Si–O–B bonds were present in glass. The glass samples exhibited excellent thermal properties and chemical stabilities. As the amount of Na2O exceeded 4 mol.%, the interconnectivity of borate and silicate sub-networks was weakened. The thermal properties and chemical stabilities of the glass samples were reduced. The connectivity of the silicate sub-network was weakened slightly as the Na/K ratio varied, and the coefficient of thermal expansion (CTE) of the glass samples gradually increased, and the resistance to thermal shock (RTS) value gradually decreased. Moreover, the viscosity of the glass samples decreased with the ratio of Na/Si and Na/K increased. 相似文献