全文获取类型
收费全文 | 2786篇 |
免费 | 329篇 |
国内免费 | 83篇 |
专业分类
电工技术 | 32篇 |
技术理论 | 1篇 |
综合类 | 187篇 |
化学工业 | 1040篇 |
金属工艺 | 56篇 |
机械仪表 | 49篇 |
建筑科学 | 84篇 |
矿业工程 | 63篇 |
能源动力 | 73篇 |
轻工业 | 485篇 |
水利工程 | 42篇 |
石油天然气 | 50篇 |
武器工业 | 7篇 |
无线电 | 368篇 |
一般工业技术 | 394篇 |
冶金工业 | 149篇 |
原子能技术 | 16篇 |
自动化技术 | 102篇 |
出版年
2024年 | 15篇 |
2023年 | 74篇 |
2022年 | 112篇 |
2021年 | 135篇 |
2020年 | 151篇 |
2019年 | 127篇 |
2018年 | 113篇 |
2017年 | 120篇 |
2016年 | 122篇 |
2015年 | 108篇 |
2014年 | 176篇 |
2013年 | 163篇 |
2012年 | 219篇 |
2011年 | 250篇 |
2010年 | 140篇 |
2009年 | 166篇 |
2008年 | 143篇 |
2007年 | 155篇 |
2006年 | 126篇 |
2005年 | 102篇 |
2004年 | 81篇 |
2003年 | 67篇 |
2002年 | 54篇 |
2001年 | 53篇 |
2000年 | 47篇 |
1999年 | 41篇 |
1998年 | 27篇 |
1997年 | 24篇 |
1996年 | 14篇 |
1995年 | 14篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1978年 | 2篇 |
1966年 | 1篇 |
排序方式: 共有3198条查询结果,搜索用时 15 毫秒
81.
In this study, two types of convolutional neural network (CNN) classifiers are designed to handle the problem of classifying black plastic wastes. In particular, the black plastic wastes have the property of absorbing laser light coming from spectrometer. Therefore, the classification of black plastic wastes remains still a challenging problem compared to classifying other colored plastic wastes using existing spectroscopy (i.e., NIR). When it comes the classification problem of black plastic wastes, effective classification techniques by the laser spectroscopy of Fourier Transform-Infrared Radiation (FT-IR) with Attenuated Total Reflectance (ATR) and Raman to analyze the classification problem of black plastic wastes are introduced. Due to the strong ability of extracting spatial features and remarkable performance in image classification, 1D and 2D CNN through data features are designed as classifiers. The technique of chemical peak points selection is considered to reduce data redundancy. Furthermore, through the selection of data features based on the extracted 1D data with peak points is introduced. Experimental results demonstrate that 2DCNN classifier designed with the help of 2D data feature selection as well as 1DCNN classifier shows the best performance compared with other reported methods for classifying black plastic wastes. 相似文献
82.
本文介绍了广州新造珠江大桥的主梁0#块施工情况,针对0#块分支架、挂篮施工相结合的施工方法做出了主要阐述,突出了其与传统施工方法的差异,强调了临时索、挂篮提前应用的先进性和优势,希望对以后类似的斜拉桥主梁0#块施工提供借鉴。 相似文献
83.
《分离科学与技术》2012,47(4):983-994
Abstract A rapid, selective, and sensitive cloud point extraction process using mixed micelle of a nonionic surfactant, Triton X-114, and an anionic surfactant, SDS, to extract sulfide from aqueous solutions was investigated. The method is based on the color reaction of sulfide with N,N-diethyl-p-phenylenediamine (DPD) in the presence of suitable oxidizing reagent (Fe3+) in acid media and cloud point extraction of ethylene blue (EB) dye. Various factors and optimal extraction and reaction conditions like: acid, Fe3+, reagent, and surfactant concentration were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, RSD%) were obtained. Linearity was obeyed in the range of 1–100 ng mL?1 of sulfide ion. The detection limit of the method is 0.5 ng mL?1 of sulfide ion. The interference effect of some anions, cations, and neutral species was also tested. The method was applied to the determination of sulfide in spring, river, and waste water samples. 相似文献
84.
The formation of anthocyanin–metal chelates, exhibiting intense blue colours was monitored over a period up to 10 weeks. Evaluating normalised absorption spectra in the range of 580–700 nm and their proportion of the total area under the curve (AUC), provided information about the blue colour hue, intensity and stability. Colour stability in model solutions containing commercial sugar beet pectin or an isolated pectic polysaccharide fraction (PPF) therefrom, both being naturally enriched in aluminium and ferric ions, was assessed in a pH range of 3.6–7.0. The pectic structures stabilised anthocyanin–metal chelates, and thus blue colours by efficiently preventing complex precipitation. Highest bathochromic shifts and most intense blue colours were observed in PPF model solutions containing delphinidin-3-glucoside (Dpd-3-glc), exhibiting a pyrogallol moiety in the flavylium B-ring, compared to cyanidin- (Cyd-3-glc) and petunidin-3-glucoside (Pet-3-glc), both carrying a catechol substituted B-ring. Hue and intensity of the blue colour at pH 5.0 were only insignificantly influenced by the buffer system except for citrate and phosphate buffers, which both annihilated anthocyanin–metal chelate formation. The blue colours faded following first order kinetics. Best stabilities as deduced from storage experiments performed at 20 ± 2 °C in the dark were observed for Dpd-3-glc. In contrast, Cyd-3-glc displayed shortened half-life values, whereas blue Pet-3-glc chelates decomposed rapidly. These results demonstrate that the solubilisation of anthocyanin–metal chelates by pectic structures is a promising option for developing water soluble natural blue food colourants. 相似文献
85.
86.
Wei Yang Xiaoxian Pang Zhao Xue Jinhao Ye Haosen Fan Ting Shu Wenzhi Zheng Shengzhou Chen 《金属学报(英文版)》2021,34(3):435-443
Ni3[Fe(CN)6]2 nano-cubic precursors were prepared by chemical coprecipitation at room temperature with nickel acetate and potassium ferricyanide as raw materials.The corresponding NiFe2O4-NiO@C composites with excellent crystallization were prepared by two-stage oxidation at low temperature.The microstructure and electrochemical behavior of the materials showed that the Prussian blue analog was transformed into metal oxide while the carbon coating was maintained in the two-stage oxidation at low temperature.The existence of the carbon coating reduces the charge transfer impedance to 31.5 Ω.At the current density of 500 mA/g,the reversible capacity of 632.7 mAh/g is maintained after 500 cycles.At the same time,carbon cladding can also enhance the role of pseudocapacitance in the material.At the scanning rate of 0.1 mV/s,the pseudocapacitance account for 54.4% of the total discharge capacity,which is significantly higher than that of uncoated materials. 相似文献
87.
以WCYJK14-7-53Z型无游梁式抽油机为研究对象,应用有限元法对其进行了地震谱作用下的动力响应分析。首先建立该抽油机框架结构的有限元模型和编制II类场地8度烈度下的地震反应谱,分别进行了模态分析和地震谱分析,然后对该抽油机结构进行动强度验算,得出该结构满足动强度要求。 相似文献
88.
89.
配合物[Pd(dmphen)CO3]·H2O(dmphen是2,9-二甲基-1,10-菲咯啉)已合成和表征。钯配合物是采用水热合成法制备的,利用X射线单晶衍射法、元素分析、红外等方法对其进行表征。本文以亚甲基蓝(MB)为探针进行了光催化反应对其进行降解,测评了[Pd(dmphen)CO3]·H2O配合物的光催化降解活性。结果表明,在300 W氙灯光源照射下,该配合物对亚甲基蓝光的催化降解有一定效果,亚甲基蓝(MB)的光催化降解率由时间和Pd配合物的参与共同决定。 相似文献
90.