全文获取类型
收费全文 | 274804篇 |
免费 | 22819篇 |
国内免费 | 12197篇 |
专业分类
电工技术 | 16010篇 |
技术理论 | 28篇 |
综合类 | 19481篇 |
化学工业 | 45159篇 |
金属工艺 | 14950篇 |
机械仪表 | 17039篇 |
建筑科学 | 22076篇 |
矿业工程 | 7670篇 |
能源动力 | 7685篇 |
轻工业 | 20777篇 |
水利工程 | 4796篇 |
石油天然气 | 15092篇 |
武器工业 | 2194篇 |
无线电 | 31917篇 |
一般工业技术 | 32122篇 |
冶金工业 | 13031篇 |
原子能技术 | 3003篇 |
自动化技术 | 36790篇 |
出版年
2024年 | 1096篇 |
2023年 | 4265篇 |
2022年 | 7743篇 |
2021年 | 10394篇 |
2020年 | 7987篇 |
2019年 | 6538篇 |
2018年 | 7369篇 |
2017年 | 8523篇 |
2016年 | 7486篇 |
2015年 | 10386篇 |
2014年 | 13269篇 |
2013年 | 16037篇 |
2012年 | 17763篇 |
2011年 | 19321篇 |
2010年 | 17106篇 |
2009年 | 16482篇 |
2008年 | 16336篇 |
2007年 | 15494篇 |
2006年 | 15696篇 |
2005年 | 13324篇 |
2004年 | 9222篇 |
2003年 | 7952篇 |
2002年 | 7619篇 |
2001年 | 6891篇 |
2000年 | 6553篇 |
1999年 | 7001篇 |
1998年 | 5880篇 |
1997年 | 4892篇 |
1996年 | 4477篇 |
1995年 | 3565篇 |
1994年 | 3039篇 |
1993年 | 2260篇 |
1992年 | 1783篇 |
1991年 | 1386篇 |
1990年 | 1072篇 |
1989年 | 891篇 |
1988年 | 697篇 |
1987年 | 507篇 |
1986年 | 361篇 |
1985年 | 276篇 |
1984年 | 158篇 |
1983年 | 139篇 |
1982年 | 146篇 |
1981年 | 102篇 |
1980年 | 91篇 |
1979年 | 46篇 |
1978年 | 28篇 |
1977年 | 26篇 |
1976年 | 43篇 |
1959年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Qi Yang Qilong Wu Yang Liu Shuiping Luo Xiaotong Wu Xixia Zhao Haiyuan Zou Baihua Long Wen Chen Yujia Liao Lanxi Li Pei Kang Shen Lele Duan Zewei Quan 《Advanced materials (Deerfield Beach, Fla.)》2020,32(36):2002822
Engineering novel Sn-based bimetallic materials could provide intriguing catalytic properties to boost the electrochemical CO2 reduction. Herein, the first synthesis of homogeneous Sn1−xBix alloy nanoparticles (x up to 0.20) with native Bi-doped amorphous SnOx shells for efficient CO2 reduction is reported. The Bi-SnOx nanoshells boost the production of formate with high Faradaic efficiencies (>90%) over a wide potential window (−0.67 to −0.92 V vs RHE) with low overpotentials, outperforming current tin oxide catalysts. The state-of-the-art Bi-SnOx nanoshells derived from Sn0.80Bi0.20 alloy nanoparticles exhibit a great partial current density of 74.6 mA cm−2 and high Faradaic efficiency of 95.8%. The detailed electrocatalytic analyses and corresponding density functional theory calculations simultaneously reveal that the incorporation of Bi atoms into Sn species facilitates formate production by suppressing the formation of H2 and CO. 相似文献
63.
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
64.
Requirements Engineering - In software reuse, the reuse of UML class diagram produced in design phase has received more attention due to the important influence on the following developing process.... 相似文献
65.
66.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
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
67.
Dy3+, Eu3+: NaLa(WO4)2 phosphors are successfully synthesized through the solid-state reaction technique. The phase-structure and morphology are measured via X-ray diffraction and energy dispersive spectrometry. The concentrations of Dy3+, Eu3+, La3+, and W6+ are measured via ICP. The absorption and excited spectra are presented, which indicate that a blue band ranging from 430 to 480 nm is suitable for excitation. Using a commercial blue LED with a wavelength of 450 nm as the excitation light source, emission spectra for samples with varying dopant concentration ratios of Dy3+ to Eu3+ are obtained, which show good tunable yellow and red emission. For the purpose of investigating white LED performance, CIE spectra and a white light photo are also presented. The results reveal that varying the dopant concentration ratio of Dy3+ to Eu3+ plays a key role in the warm-white performance. With increasing concentration of Eu3+, the correlated color temperature decreases from 4069 to 3172 K, which indicates good warm-white performance. 相似文献
68.
本研究针对水泥窑余热发电系统的工作条件,根据耐磨材料的损毁机理,采用高铝矾土、煅烧氧化铝粉、黏土、硅微粉等为原料,以磷酸二氢铝为结合剂,以铝酸钙水泥为促硬剂,通过添加掩蔽剂和优化配料工艺,制备了水泥窑余热发电系统用耐磨材料,并对不同处理温度对耐磨材料的性能影响进行了分析。结果表明增强骨料与基质的结合能力有利于耐磨性的提高,磷酸及磷酸盐与氧化铝之间会随着温度的升高生成不同的磷酸铝相,都能够起到结合作用,比采用水泥结合更有利于提高材料在不同温度下的强度和耐磨性。使用结果表明,制备的耐磨材料施工性能优良,凝结硬化时间适当,强度高,抗冲刷性能好,在水泥窑余热发电系统中取得了良好的使用效果。 相似文献
69.
70.