全文获取类型
收费全文 | 521751篇 |
免费 | 91996篇 |
国内免费 | 55509篇 |
专业分类
电工技术 | 45346篇 |
技术理论 | 57篇 |
综合类 | 39987篇 |
化学工业 | 81702篇 |
金属工艺 | 41405篇 |
机械仪表 | 28511篇 |
建筑科学 | 38515篇 |
矿业工程 | 23573篇 |
能源动力 | 18253篇 |
轻工业 | 40027篇 |
水利工程 | 12723篇 |
石油天然气 | 34073篇 |
武器工业 | 6318篇 |
无线电 | 66293篇 |
一般工业技术 | 70461篇 |
冶金工业 | 25687篇 |
原子能技术 | 4653篇 |
自动化技术 | 91672篇 |
出版年
2024年 | 3816篇 |
2023年 | 9448篇 |
2022年 | 13951篇 |
2021年 | 18418篇 |
2020年 | 18477篇 |
2019年 | 25638篇 |
2018年 | 28319篇 |
2017年 | 30322篇 |
2016年 | 29285篇 |
2015年 | 31363篇 |
2014年 | 33840篇 |
2013年 | 36546篇 |
2012年 | 36755篇 |
2011年 | 35834篇 |
2010年 | 31065篇 |
2009年 | 27286篇 |
2008年 | 25373篇 |
2007年 | 23889篇 |
2006年 | 24040篇 |
2005年 | 21401篇 |
2004年 | 17924篇 |
2003年 | 15497篇 |
2002年 | 14214篇 |
2001年 | 12859篇 |
2000年 | 12950篇 |
1999年 | 14111篇 |
1998年 | 12196篇 |
1997年 | 10348篇 |
1996年 | 9753篇 |
1995年 | 8695篇 |
1994年 | 7194篇 |
1993年 | 5661篇 |
1992年 | 4941篇 |
1991年 | 3769篇 |
1990年 | 2963篇 |
1989年 | 2607篇 |
1988年 | 2079篇 |
1987年 | 1039篇 |
1986年 | 808篇 |
1985年 | 563篇 |
1984年 | 393篇 |
1983年 | 310篇 |
1982年 | 347篇 |
1981年 | 273篇 |
1980年 | 231篇 |
1976年 | 298篇 |
1975年 | 233篇 |
1972年 | 252篇 |
1971年 | 146篇 |
1960年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
13.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
14.
Wang Chen Bao Chun-Hui Wu Wan-Yu Hsu Chia-Hsun Zhao Ming-Jie Zhang Xiao-Ying Lien Shui-Yang Zhu Wen-Zhang 《Journal of Materials Science》2022,57(26):12341-12355
Journal of Materials Science - Molybdenum oxide (MoOx) films had been grown by using plasma-enhanced atomic layer deposition (PEALD) with Mo(CO)6 precursor and O2 plasma reactant in a substrate... 相似文献
16.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
17.
Yarn-dyed fabric is often woven from warp and weft yarns in the same color depth to ensure a uniform color appearance. The difference in color depth between warp and weft tends to result in the uneven color of the yarn-dyed fabric. This article aims to establish a color tolerance for yarn-dyed fabric that can be woven with a qualified color appearance but from the warp and weft yarns in different color depths. A total of 27 yarn-dyed fabric samples in three color series (red, yellow, and blue) were evaluated by using the yarn-dyed fabric from warp and weft yarns in the same color depth of 2% (on weight of fabric, owf) as the standard. Visual assessment and instrumental measurement of color were carried out to establish the color tolerance ellipse that was defined as CMC (Color Measurement Committee) color differences (2:1) of no more than 1.00. It was found that the color strengths (K/S) and color differences (ΔECMC(2:1)) of these fabric samples for each color series had linear relationships with the color depths of warp and weft yarns. The color tolerance ellipses indicated that, even though the warp and weft yarns had an apparent color difference, they could be woven in fabrics with relatively uniform color appearance and meet the requirements for yarn-dyed fabric. This work provided valuable insight into the production of qualified yarn-dyed fabrics from unqualified dyed yarns. 相似文献
18.
19.
Journal of Porous Materials - Co3O4 has been widely investigated as a promising candidate anode material for lithium-ion batteries. We report on the porous Co3O4 column synthesized via a simple... 相似文献
20.
Shannon Lee Scott L. Carnahan Georgiy Akopov Philip Yox Lin-Lin Wang Aaron J. Rossini Kui Wu Kirill Kovnir 《Advanced functional materials》2021,31(16):2010293
Noncentrosymmetric (NCS) tetrel pnictides have recently generated interest as nonlinear optical (NLO) materials due to their second harmonic generation (SHG) activity and large laser damage threshold (LDT). Herein nonmetal-rich silicon phosphides RuSi4P4 and IrSi3P3 are synthesized and characterized. Their crystal structures are reinvestigated using single crystal X-ray diffraction and 29Si and 31P magic angle spinning NMR. In agreement with previous report RuSi4P4 crystallizes in NCS space group P1, while IrSi3P3 is found to crystallize in NCS space group Cm, in contrast with the previously reported space group C2. A combination of DFT calculations and diffuse reflectance measurements reveals RuSi4P4 and IrSi3P3 to be wide bandgap (Eg) semiconductors, Eg = 1.9 and 1.8 eV, respectively. RuSi4P4 and IrSi3P3 outperform the current state-of-the-art infrared SHG material, AgGaS2, both in SHG activity and laser inducer damage threshold. Due to the combination of high thermal stabilities (up to 1373 K), wide bandgaps (≈2 eV), NCS crystal structures, strong SHG responses, and large LDT values, RuSi4P4 and IrSi3P3 are promising candidates for longer wavelength NLO materials. 相似文献