全文获取类型
收费全文 | 3971篇 |
免费 | 445篇 |
国内免费 | 300篇 |
专业分类
电工技术 | 83篇 |
综合类 | 207篇 |
化学工业 | 819篇 |
金属工艺 | 490篇 |
机械仪表 | 188篇 |
建筑科学 | 114篇 |
矿业工程 | 46篇 |
能源动力 | 197篇 |
轻工业 | 232篇 |
水利工程 | 37篇 |
石油天然气 | 32篇 |
武器工业 | 17篇 |
无线电 | 1125篇 |
一般工业技术 | 695篇 |
冶金工业 | 191篇 |
原子能技术 | 26篇 |
自动化技术 | 217篇 |
出版年
2024年 | 14篇 |
2023年 | 60篇 |
2022年 | 99篇 |
2021年 | 110篇 |
2020年 | 153篇 |
2019年 | 123篇 |
2018年 | 131篇 |
2017年 | 161篇 |
2016年 | 149篇 |
2015年 | 176篇 |
2014年 | 205篇 |
2013年 | 249篇 |
2012年 | 289篇 |
2011年 | 347篇 |
2010年 | 234篇 |
2009年 | 222篇 |
2008年 | 213篇 |
2007年 | 247篇 |
2006年 | 260篇 |
2005年 | 204篇 |
2004年 | 203篇 |
2003年 | 152篇 |
2002年 | 105篇 |
2001年 | 97篇 |
2000年 | 100篇 |
1999年 | 62篇 |
1998年 | 61篇 |
1997年 | 33篇 |
1996年 | 47篇 |
1995年 | 39篇 |
1994年 | 38篇 |
1993年 | 29篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 23篇 |
1989年 | 14篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有4716条查询结果,搜索用时 171 毫秒
71.
F.J. Pérez-Alonso C. AdánS. Rojas M.A. PeñaJ.L.G. Fierro 《International Journal of Hydrogen Energy》2014
A series of Ni/Fe electrodes have been prepared by electrodeposition of metal salt precursors on different substrates. The surface morphology, chemical composition and electrochemical characteristics of these electrodes were studied by various physico-chemical techniques such as X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM). The electrochemical properties of the electrodes were examined by steady-state polarization curves. First, the influence of features such as Ni/Fe composition and type of substrate for the oxygen evolution reaction (OER) were determined by electrochemical techniques in a conventional 3-electrodes cell. The overpotential for the OER is lower for the electrodes with the higher concentrations of Ni. The electrodes with a Ni/Fe composition of 75/25 wt.% electrodeposited on steel mesh and/or 75/25 and 50/50 wt.% on nickel foam result in the most active configurations for the OER. These electrodes were further tested as anodes for alkaline water electrolysis during at least 70 h. In order to understand their activity and stability, the used electrodes were also characterized by SEM and compared to the fresh electrodes. Among the compositions and substrates examined, the Ni50Fe50-Nf electrode exhibited the lowest overpotential (2.1 V) for the OER and the higher stability as anode in an alkaline water electrolysis cell. 相似文献
72.
73.
74.
75.
《Microelectronics Reliability》2014,54(9-10):2064-2069
The semiconductor technologies evolution allows greatly reducing noise impact on products and many structures have been created to reduce its effect. However, this paper presents the apparition of a noise issue during the production of a mixed-mode device dedicated to automotive applications. The research investigations concerned the fact that failure was not detected at test level but at customer level; therefore, it was determinant to understand the root cause of this failure mode to drive corrective actions in order to secure customer. The challenge was to analyse noise in Failure Analysis (FA) without fault spatial localization results. Indeed, Light Emission Microscopy (EMMI) and Thermal Laser Stimulation (ex: Soft Defect Localization – SDL) were unable to provide any defective area in the product. The lack of failing device identification led us to combine electrical and design analyses in order to define hypothesis on the failure origin. It was then possible to drive physical investigations through different approaches, using physical cross-section, Secondary Ion Mass Spectrometry (SIMS) and Scanning Capacitance Microscopy (SCM) techniques. Finally, the obtained complementary results will be discussed and an explanation of the failure mechanism will be presented as the root cause issue, allowing defining the defective step in production process. 相似文献
76.
碳纳米管涂层已在低温工作环境中大量应用,所选用的粘结剂在很大程度上影响其红外吸收性能及与基体的结合性能。分别用水玻璃粘结剂和磷酸盐粘结剂与碳纳米管、镍粉混合制成涂料,并将其涂覆在铜基体表面。采用XRD和SEM对涂层的红外吸收性能、物相、晶体结构及形貌进行了表征;测试了涂层的抗热震性能。结果表明:当粘结剂为磷酸盐、含量为90%~85%时,1 400~3 570 cm~(-1)(2.80~7.14μm)波段内涂层的平均光吸收度达1.992~2.084,红外吸收性能最佳,抗热震次数可达35次(25~120℃),满足了用户要求(10次)。 相似文献
77.
Physicochemical and sensory characteristics of soya protein isolate hydrolysates with added substrate‐like amino acids 下载免费PDF全文
Jianan Zhang Jucai Xu Lei Liu Yang Liu Tiantian Zhao Changping Wu Dongxiao Sun‐Waterhouse Mouming Zhao Guowan Su 《International Journal of Food Science & Technology》2016,51(1):69-77
Soya protein isolate (SPI) with or without added substrate‐like amino acid was subject to enzymatic hydrolysis catalysed by commercial proteases (Alcalase 2.4 L, flavourzyme and pancreatin). Addition of a small amount of amino acids (amino acid: SPI = 1: 2500, mol g?1) during hydrolysis would cause a significantly (P < 0.05) reduced protein recovery, increased degree of hydrolysis, and altered amino acid composition and antioxidant activities of SPI hydrolysates. The SPI hydrolysates prepared with added Asp, Arg or Lys exhibited a higher antioxidant activity than the control. The bitterness of SPI hydrolysates was largely reduced upon addition of Met, Asp or Glu during hydrolysis, whilst the umami taste and mouthfeel‐liking were remarkably increased. Therefore, adding amino acid during hydrolysis is a feasible and beneficial approach to improve both the functional and sensory properties of SPI hydrolysate. 相似文献
78.
A limited number of bacteria can convert oil palm (Elaeis guineensis) sap to hydrogen with satisfactory yield and productivity. In this study, a total of 18 fermentative enriched cultures and 36 newly isolated thermotolerant bacterial strains were compared for hydrogen production from oil palm (OP) sap. The new isolates were obtained from hot springs, palm oil mill effluent and oil palm sap. The test was conducted in three steps: (i) a test for hydrogen production from mixed substrates (cellulose, starch, xylose, and glucose) and OP sap; (ii) a test for substrate concentration tolerance; and (iii) a test for thermotolerance. Five enriched candidates for each of the hydrogen producers were selected according to the criteria defined for the screening test. The hydrogen production of these selected bacterial strains from hot springs were cultivated in batch fermentation of oil palm sap at room temperature (30 ± 2 °C). Five enriched cultures, namely 81RN1, OPS, 85RN5, 89SR3-2 and 112YL1 were found to give high cumulative hydrogen formation of 1085, 1009, 994, 983 and 778 mL H2/L-OP sap, respectively, with the hydrogen content of 29.8, 29.4, 28.7, 27.1 and 27.5%, respectively. PCR–DGGE profiling showed that all these five enriched cultures consisted of species closely related to the genus Clostridium sp. based on the 16S rRNA gene. For pure cultures, the top five hydrogen producers were the isolates encoded as PS-3, PS-4, PS-5, PS-7 and PS-8 exhibiting the hydrogen production of 1973, 1774, 1335, 1170 and 1070 mL H2/L-OP sap, respectively, with the hydrogen content of 33.7, 29.6, 32.5, 31.5 and 26.4%, respectively. Identification of these high hydrogen producers using 16S rRNA sequence matching showed that the isolates PS-3 and PS-8 belonged to Clostridium beijerinckii, while the isolate PS-7 belonged to Clostridium acetobutylicum and the isolates PS-4 and PS-5 belonged to Klebsiella sp. and Klebsiella pneumoniae, respectively. Therefore, the pure culture C. beijerinckii PS-3 exhibited 1.8 folds higher hydrogen production (1973 mL H2/L-OP sap) than the enriched cultures of 81RN1 (1085 mL H2/L-OP sap). 相似文献
79.
This article studies the axial buckling of a nanowire (NW) lying on Winkler–Pasternak substrate medium with the Timoshenko beam theory. The surface effect of the NW is accounted for with the Steigmann–Ogden model. An explicit solution of the critical buckling force and its associated buckling mode are obtained analytically. The influences of the surface stress effect, the geometry of the NW, and the elastic foundation moduli on the buckling behavior are fully discussed. 相似文献
80.
采用X射线四环衍射技术和背散射电子衍射技术,对具有多层结构的NiW合金复合基带外层Ni5W(at%)的形变织构和再结晶织构进行了研究。研究发现,梯度分布的形变织构和多层材料之间的扩散是决定复合基带外层Ni5W织构演变的两个主要因素。这为进一步研究金属合金复合材料各层之间的织构形成及其关联性奠定了基础。 相似文献