全文获取类型
收费全文 | 1899篇 |
免费 | 112篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 16篇 |
综合类 | 156篇 |
化学工业 | 830篇 |
金属工艺 | 40篇 |
机械仪表 | 19篇 |
建筑科学 | 50篇 |
矿业工程 | 317篇 |
能源动力 | 20篇 |
轻工业 | 162篇 |
水利工程 | 25篇 |
石油天然气 | 49篇 |
武器工业 | 5篇 |
无线电 | 17篇 |
一般工业技术 | 67篇 |
冶金工业 | 228篇 |
原子能技术 | 22篇 |
自动化技术 | 15篇 |
出版年
2024年 | 5篇 |
2023年 | 10篇 |
2022年 | 22篇 |
2021年 | 34篇 |
2020年 | 27篇 |
2019年 | 23篇 |
2018年 | 29篇 |
2017年 | 35篇 |
2016年 | 44篇 |
2015年 | 58篇 |
2014年 | 96篇 |
2013年 | 93篇 |
2012年 | 149篇 |
2011年 | 141篇 |
2010年 | 97篇 |
2009年 | 102篇 |
2008年 | 97篇 |
2007年 | 142篇 |
2006年 | 130篇 |
2005年 | 114篇 |
2004年 | 82篇 |
2003年 | 73篇 |
2002年 | 61篇 |
2001年 | 68篇 |
2000年 | 60篇 |
1999年 | 48篇 |
1998年 | 38篇 |
1997年 | 21篇 |
1996年 | 26篇 |
1995年 | 22篇 |
1994年 | 20篇 |
1993年 | 15篇 |
1992年 | 17篇 |
1991年 | 9篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有2038条查询结果,搜索用时 15 毫秒
1.
《Food Control》2015
In this work a multicommuted flow system employing copper–4,4′- dipyridyl coordination compound as the solid-phase reagent for the spectrophotometric determination of reducing sugar was developed. The coordination compound was synthesized through a reaction of the 4,4′-dipyridyl and copper (II) nitrate, under hydrothermal conditions. The complex was characterized by infrared spectroscopy (FTIR), power X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and thermogravimetric analysis (TGA). Based on the characterization, a multicommuted spectrophotometric procedure for the determination of reducing sugar using copper (II) complex as solid reagent is proposed. The proposed method was based on the redox reaction between a monosaccharide, such as fructose and glucose (reducing sugar) and Cu(II). This reaction, mediated in an alkaline medium, produces a yellow compound that can be determined by absorption electronic spectroscopy (λABS = 420 nm). Under optimum experimental conditions, a linear response ranging from 1.0 to 20.0 g L−1 (R = 0.9978 and n = 5), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.23 and 0.75 g L−1, respectively, a standard deviation relative of 4.7% (n = 7), for a reference solution of 10.0 g L−1 reducing sugar, and a sampling rate of 75 determinations per hour were achieved. The proposed system was applied to the determination of reducing sugars in coconut water and juices. The analysis of ten samples and the application of the t-test to the results found, and those obtained using reference procedures (AOAC), provided no significant differences at a 95% confidence level. This system enabled the analysis of reducing sugar with ease and simplicity, providing a significant economy of the solid reagent (600 μg per determination) and reducing effluent generation. 相似文献
2.
3.
Fenton氧化法去除酱油生产废水中焦糖色素的研究 总被引:1,自引:0,他引:1
着重考察了Fenton试剂对水中焦糖色素降解的影响因素.从试验中得出,这些影响因素包括pH、催化剂的投加方式、催化剂与氧化剂的化学计量数以及反应时间等.Fenton反应中,pH4的条件下处理效果最好,反应进行40min时去除率达到90%. 相似文献
4.
本文评价了塑料闪烁片用作软β核素探测器时的计数效率、β谱、本底谱和康普顿电子谱的特征。文中强调:采用胶合光导剂构成的系统是一种新型探测器(软β核素内部样品塑料闪烁探测器)。本文提出内部样品固体探测器、胶合光导剂和胶合闪烁光导剂的新概念。 相似文献
5.
在第一部分综合讨论的基础上对甘三酯立体专一分析方法作了初步探讨。以液体油(菜油)及固体脂(猪脂)为基质,系统地研究了这一分析方法,取得了经验并补充了一些具体验证方法。分析液体油的结果与文献数据相一致,分析猪脂的结果欠佳,还存在一些问题需待进一步研究。 相似文献
6.
7.
8.
介绍了4种对钯有高灵敏和选择性的安替比林偶氮胂酸类试剂。试剂在较高酸度介质中能与钯形成稳定的2:1红色络合物。表观摩尔吸光系数为3.5~5.1×104。用AAATAR测定镍铜合金中的钯,结果满意。 相似文献
9.
Comparison of six methylation methods for analysis of the fatty acid composition of albacore lipid 总被引:2,自引:0,他引:2
I. MEDINA S. AUBOURG J. M. GALLARDO R. PÉREZ-MARTÍN 《International Journal of Food Science & Technology》1992,27(5):597-601
Six methods widely used to produce methyl esters for the gas chromatographic determination of the fatty acid composition of a marine lipid were compared. Four acid-catalyzed methods (1% H2 SO4 : CH3 OH; 5% HCl: CH3 OH; 7% and 14% BF3 : CH3 OH) and two base-catalyzed methods [0.5M NaOCH3 : CH3 OH; (1:4) tetramethylguanidine: CH3 OH] were used.
The use of BF3 : CH3 OH (7% and 14%) gave a lower content of 18:1 n9 than the other methods and produced an artefact (2.7–3.2% of total fatty acid content) eluting between the 20:5 and 24:1 fatty acid methyl esters. No significant differences were obtained between the other four methods.
Accordingly the use of BF3 : CH3 OH for transmethylation of marine lipids is not recommended. Results obtained in the other four methods showed that all are comparable. 相似文献
The use of BF
Accordingly the use of BF
10.
The chemical oxidation of aniline to form polyaniline (PANI) films and powder samples was made using Fenton reagent as an oxidizing agent in aqueous sulfuric acid medium. The PANI films were monitored by using the quartz crystal microbalance and the electronic absorption techniques. The optimum concentration was determined and the results were justified by measuring the UV–vis absorption spectra for the in situ PANI films. The conductivity for the PANI films and powder samples, prepared in different conditions, was measured. Also, the IR spectra, X‐ray and the thermogravimetric analysis for the PANI powder formed in the bulk were measured and compared with the polymer prepared using ammonium peroxydisulfate. A preliminary investigation to the dielectric properties of the polymer powder was measured and discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献