全文获取类型
收费全文 | 172078篇 |
免费 | 12268篇 |
国内免费 | 6077篇 |
专业分类
电工技术 | 8683篇 |
技术理论 | 9篇 |
综合类 | 8716篇 |
化学工业 | 27499篇 |
金属工艺 | 9966篇 |
机械仪表 | 10054篇 |
建筑科学 | 9781篇 |
矿业工程 | 3930篇 |
能源动力 | 3648篇 |
轻工业 | 9807篇 |
水利工程 | 3134篇 |
石油天然气 | 9523篇 |
武器工业 | 1051篇 |
无线电 | 17501篇 |
一般工业技术 | 26776篇 |
冶金工业 | 16182篇 |
原子能技术 | 4826篇 |
自动化技术 | 19337篇 |
出版年
2024年 | 713篇 |
2023年 | 2315篇 |
2022年 | 4593篇 |
2021年 | 6182篇 |
2020年 | 4662篇 |
2019年 | 4006篇 |
2018年 | 5120篇 |
2017年 | 5575篇 |
2016年 | 5130篇 |
2015年 | 5636篇 |
2014年 | 7289篇 |
2013年 | 8953篇 |
2012年 | 9527篇 |
2011年 | 10226篇 |
2010年 | 8687篇 |
2009年 | 8521篇 |
2008年 | 8399篇 |
2007年 | 7889篇 |
2006年 | 7308篇 |
2005年 | 6245篇 |
2004年 | 4782篇 |
2003年 | 4706篇 |
2002年 | 4742篇 |
2001年 | 4320篇 |
2000年 | 3750篇 |
1999年 | 3452篇 |
1998年 | 4134篇 |
1997年 | 3060篇 |
1996年 | 2549篇 |
1995年 | 2069篇 |
1994年 | 1773篇 |
1993年 | 1573篇 |
1992年 | 1274篇 |
1991年 | 1176篇 |
1990年 | 1162篇 |
1989年 | 1107篇 |
1988年 | 1001篇 |
1987年 | 939篇 |
1986年 | 854篇 |
1985年 | 772篇 |
1984年 | 726篇 |
1981年 | 716篇 |
1979年 | 760篇 |
1978年 | 826篇 |
1977年 | 901篇 |
1976年 | 1117篇 |
1975年 | 753篇 |
1974年 | 743篇 |
1973年 | 747篇 |
1972年 | 734篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
51.
52.
V. E. Gromov A. M. Glezer K. V. Morozov Yu. F. Ivanov K. V. Volkov 《Russian Metallurgy (Metally)》2015,2015(13):1094-1097
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis. 相似文献
53.
54.
Zenan Yu Julian Moore Jean Calderon Lei Zhai Jayan Thomas 《Small (Weinheim an der Bergstrasse, Germany)》2015,11(39):5289-5295
Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm−3), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets. 相似文献
55.
Qingna Gong Songtao Cao Yu Zhou Ruixin Wang Weizhou Jiao 《International Journal of Hydrogen Energy》2021,46(41):21442-21453
Ni2P nanoparticles and CdS nanorods were grew together on a mesoporous g-C3N4 through a facile in-situ solvothermal approach. Under visible light (λ > 400 nm), the as-prepared ternary PCN–CdS-5% Ni2P composite displays a high H2 evolution rate with 2905.86 μmol g?1 h?1, which is about 14, 18 and 279 times that of PCN–CdS, PCN–Ni2P and PCN, respectively. The enhanced photocatalytic activity is mainly attributed to the improved separation efficiency of the photocarriers by the type II PCN–CdS heterojunction and the effective extraction of photogenerated electrons by Ni2P. Meanwhile, Ni2P acts as co-catalyst to provide the photocatalytic active site for hydrogen reduction. In addition, PCN–CdS-5% Ni2P composite exerts good stability in 12-h cycles. 相似文献
56.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
57.
卫星导航地基增强系统(GBAS)是国际民航组织重点推进的新技术。为全面借鉴国际上 GBAS 技术的发展与应用,本文介绍了 GBAS 组成、原理和优缺点,研究了国内外 GBAS 研究与应用的发展,结合中国民航目前的运行需求提出了 GBAS 应用建议,为 GBAS 发展应用提供了参考。 相似文献
58.
Wireless Personal Communications - The existing long term evolution networks originally designed for human-to-human communications are hard to tackle numerous and bursty random access requests from... 相似文献
59.
60.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii 下载免费PDF全文
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献