全文获取类型
收费全文 | 88996篇 |
免费 | 11137篇 |
国内免费 | 7997篇 |
专业分类
电工技术 | 8393篇 |
综合类 | 9967篇 |
化学工业 | 10555篇 |
金属工艺 | 6755篇 |
机械仪表 | 6263篇 |
建筑科学 | 6072篇 |
矿业工程 | 3398篇 |
能源动力 | 2180篇 |
轻工业 | 9975篇 |
水利工程 | 3534篇 |
石油天然气 | 2822篇 |
武器工业 | 1382篇 |
无线电 | 9948篇 |
一般工业技术 | 7467篇 |
冶金工业 | 3540篇 |
原子能技术 | 1577篇 |
自动化技术 | 14302篇 |
出版年
2024年 | 518篇 |
2023年 | 1450篇 |
2022年 | 3700篇 |
2021年 | 4681篇 |
2020年 | 3183篇 |
2019年 | 2307篇 |
2018年 | 2465篇 |
2017年 | 2713篇 |
2016年 | 2447篇 |
2015年 | 3893篇 |
2014年 | 4860篇 |
2013年 | 5928篇 |
2012年 | 7390篇 |
2011年 | 7993篇 |
2010年 | 7537篇 |
2009年 | 7182篇 |
2008年 | 7157篇 |
2007年 | 7266篇 |
2006年 | 6291篇 |
2005年 | 5129篇 |
2004年 | 3838篇 |
2003年 | 2388篇 |
2002年 | 2263篇 |
2001年 | 1997篇 |
2000年 | 1616篇 |
1999年 | 642篇 |
1998年 | 240篇 |
1997年 | 181篇 |
1996年 | 126篇 |
1995年 | 99篇 |
1994年 | 94篇 |
1993年 | 99篇 |
1992年 | 60篇 |
1991年 | 53篇 |
1990年 | 47篇 |
1989年 | 53篇 |
1988年 | 27篇 |
1987年 | 29篇 |
1986年 | 21篇 |
1985年 | 14篇 |
1984年 | 11篇 |
1983年 | 12篇 |
1982年 | 3篇 |
1981年 | 14篇 |
1980年 | 25篇 |
1979年 | 16篇 |
1977年 | 12篇 |
1976年 | 24篇 |
1959年 | 15篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
3.
Peiying Wang Juanli Zhao Yun Fan Wei Zhang Yuanyuan Cui Liangmiao Zhang Bin Liu Hongqiang Nian Yiran Li 《Ceramics International》2021,47(11):15023-15029
In this work, the composition-dependent point defect types and formation energies of RE2Hf2O7 (RE = La, Ce, Pr, Nd, Pm, Sm, Eu and Gd) as well as the oxygen diffusion behavior are systematically investigated by first-principles calculations. The possible defect reactions and dominant defect complexes under stoichiometric and non-stoichiometric conditions are revealed. It is found that O Frenkel pairs are the predominant defect in stoichiometric pyrochlore hafnates. Hf-RE cation anti-site defects, accompanied by RE vacancies and/or oxygen interstitials, are stable in the non-stoichiometric case of HfO2 excess. On the other hand, RE-Hf anti-site defects together with oxygen vacancies and/or RE interstitials are preferable in the case of RE2O3 excess. The energy barriers for the migration along the VO48f - VO48f pathway of pyrochlore hafnates were calculated to be between 0.81 eV and 0.89 eV. Based on these results, a defect engineering strategy is proposed and the pyrochlore hafnates investigated here are predicted to exhibit potential oxygen ionic conductivity. 相似文献
4.
7.
8.
9.
简述了艺术铸造热着色技术在国内的发展过程,介绍了目前热着色技术的四大流派,分析了热着色存在的主要问题,并对艺术铸造热着色的发展方向进行了展望,有助于热着色技术在行业内快速普及. 相似文献
10.
Yuanyuan Zhang Haiyan Lu Bing Wang Zhuo Zhang Xiaorong Lin Zhongzheng Chen Bin Li 《International Journal of Food Science & Technology》2015,50(6):1397-1404
Removal of imidacloprid and acetamiprid in tea infusions by microfiltration membrane using dead‐end model was investigated in the present study. The results showed that microfiltration significantly promoted the removal of both pesticides (P < 0.05) in tea infusions. Furthermore, the extent of removal was strongly influenced by the pore size of membrane, operational pressure and the concentrations of tea infusions. The initial concentration of imidacloprid and acetamiprid showed no significant effect on their removal rates. The maximum removal rates were 79.7% for imidacloprid and 81.9% acetamiprid. The changes in major chemical components of tea infusions after microfiltration were evaluated. The results indicated that microfiltration caused no considerable changes in total polyphenols and total free amino acids, and small but statistically significant losses (6.3–18.0%) of eight catechins and three methylxanthines when filtration volume reached to 200 mL. The present study validated the application of microfiltration as a potentially feasible and promising method for the removal of imidacloprid and acetamiprid residues from tea infusions. 相似文献