全文获取类型
收费全文 | 4376篇 |
免费 | 417篇 |
国内免费 | 194篇 |
专业分类
电工技术 | 308篇 |
综合类 | 249篇 |
化学工业 | 757篇 |
金属工艺 | 238篇 |
机械仪表 | 279篇 |
建筑科学 | 340篇 |
矿业工程 | 126篇 |
能源动力 | 120篇 |
轻工业 | 303篇 |
水利工程 | 81篇 |
石油天然气 | 345篇 |
武器工业 | 30篇 |
无线电 | 487篇 |
一般工业技术 | 538篇 |
冶金工业 | 214篇 |
原子能技术 | 34篇 |
自动化技术 | 538篇 |
出版年
2024年 | 23篇 |
2023年 | 89篇 |
2022年 | 190篇 |
2021年 | 244篇 |
2020年 | 175篇 |
2019年 | 131篇 |
2018年 | 138篇 |
2017年 | 133篇 |
2016年 | 146篇 |
2015年 | 195篇 |
2014年 | 246篇 |
2013年 | 259篇 |
2012年 | 280篇 |
2011年 | 308篇 |
2010年 | 258篇 |
2009年 | 236篇 |
2008年 | 212篇 |
2007年 | 199篇 |
2006年 | 217篇 |
2005年 | 216篇 |
2004年 | 133篇 |
2003年 | 121篇 |
2002年 | 102篇 |
2001年 | 102篇 |
2000年 | 106篇 |
1999年 | 89篇 |
1998年 | 77篇 |
1997年 | 71篇 |
1996年 | 57篇 |
1995年 | 48篇 |
1994年 | 47篇 |
1993年 | 28篇 |
1992年 | 18篇 |
1991年 | 13篇 |
1990年 | 14篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 14篇 |
1986年 | 10篇 |
1985年 | 4篇 |
1984年 | 8篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 1篇 |
排序方式: 共有4987条查询结果,搜索用时 125 毫秒
1.
Fancong Zeng Yingrui Sui Yanjie Wu Dongyue Jiang Zhanwu Wang Fengyou Wang Bin Yao Lili Yang 《Ceramics International》2021,47(13):18376-18384
Element doping into the Cu2ZnSn(S,Se)4 (CZTSSe) absorber is an effective method to optimize the performance of thin film solar cells. In this study, the Cu2InxZn1-xSn(S,Se)4 (CIZTSSe) precursor film was deposited by magnetron cosputtering technique using indium (In) and quaternary Cu2ZnSnS4 (CZTS) as targets. Meanwhile, the In content was controlled using the direct current (DC) power on In target (PIn). A single kesterite CIZTSSe alloy was formed by successfully doping a small number of In3+ into the main lattice of CZTSSe. The partial Zn2+ cations were substituted by In3+ ions, resulting in improving properties of CZTSSe films. Morphological analysis showed that large grain CIZTSSe films could be obtained by doping In. The well-distributed, smooth, and dense film was obtained when the PIn was 30 W. The band gap of CIZTSSe could be continuously adjusted from 1.27 to 1.05 eV as PIn increased from 0 to 40 W. In addition, the CIZTSSe alloy thin film at PIn = 30 W exhibited the best p-type conductivity with Hall mobility of 6.87 cm2V?1s?1, which is a potential material as the absorption layer of high-performance solar cells. 相似文献
2.
Longzhi Li Xiaowei Jiang Zhiguo Bian Jianwei Wang Fumao Wang Zhanlong Song 《Drying Technology》2019,37(2):173-185
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading. 相似文献
3.
4.
在充分调研阵列声波测井分波提取方法的基础上,针对阿特拉斯公司的交叉多极子阵列声波测井(XMACⅡ)提供的单极波形信息,研究纵波时差提取及高分辨率处理方法。首先利用相关-互功谱法高精度地提取纵波时差,然后针对XMACⅡ仪器的接收阵列,研究组合子阵列的方法,形成共发射子阵列和共接收子阵列,最后利用子阵列对提取的纵波时差做高分辨率处理。处理现场实际测井资料,并将高分辨率处理成果与引进的eXpress软件处理成果、实测的国产高分辨率声波(纵波)测井曲线及岩心纵波时差对比分析,表明该方法提取的纵波时差曲线的纵向分辨率有很大提高,时差计算准确可靠,提取的单极纵波时差与国产高分辨率声波时差及岩心纵波时差的平均相对误差均小于7%。该方法具有较高的实用价值和广阔的应用前景。 相似文献
5.
6.
A large quantity of laminated fine grain zones were observed in the Al-Mg-Li alloy weld metal by manual TIG, which was not found in ordinary Al alloy welds. The fine grain zone is formed because of the Al3(Zr,Ti) particles in the filler metal and the manual filling of filler metal in welding process 相似文献
8.
9.
10.