全文获取类型
收费全文 | 245篇 |
免费 | 15篇 |
国内免费 | 6篇 |
专业分类
化学 | 193篇 |
晶体学 | 1篇 |
力学 | 7篇 |
综合类 | 3篇 |
数学 | 16篇 |
物理学 | 46篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 8篇 |
2021年 | 6篇 |
2020年 | 9篇 |
2019年 | 14篇 |
2018年 | 15篇 |
2017年 | 14篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 11篇 |
2013年 | 26篇 |
2012年 | 22篇 |
2011年 | 23篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 8篇 |
2007年 | 13篇 |
2006年 | 5篇 |
2005年 | 2篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 2篇 |
2001年 | 3篇 |
1998年 | 2篇 |
1996年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有266条查询结果,搜索用时 31 毫秒
71.
A. M. Haji Shabani S. Dadfarnia N. Nasirizadeh M. R. Shishehbore 《Journal of Analytical Chemistry》2007,62(1):46-50
A simple and convenient method for the separation and preconcentration of copper from aqueous samples has been developed.
The procedure is based on the chemical sorption of copper(II) onto a column packed with immobilized dithizone on microcrystalline
naphthalene. The trapped copper is eluted with 10 mL of 4 M nitric acid and determined by flame atomic absorption spectrometry.
A preconcentration factor of 200 was obtained for a volume of 2 L. The relative standard deviation for the determination of
5 and 10 μg/L copper was 2.2 and 1.7%, respectively. The procedure was successfully applied to the determination of copper
in water and alloy samples. The accuracy was assessed through the analysis of certified reference materials or recovery experiments.
The text was submitted by the authors in English. 相似文献
72.
A flow injection flame atomic absorption spectrometry system incorporating a microcolumn of rice bran was designed, and its capability for on‐line trace enrichment of copper, cadmium and lead was studied. Analytes were deposited on the microcolumn by processing a standard or solution of analytes on the column. Injection of 250 μL of nitric acid (1 mol/L) then served to elute the retained species to FAAS. The procedure was successfully applied for determination of copper in tap water, well water and multivitamin tablets. The accuracy was assessed through recovery experiments and independent analysis by furnace‐AAS. A sample volume of 20 mL of copper resulted in a preconcentration factor of 96; precision value at the 20 μg/L was 4.1%. 相似文献
73.
A series of 5-((1H-1, 2, 4-triazol-1-yl)methyl)-4H-1,2,4-triazole derivatives were prepared and evaluated for their antifungal
activities. Quantitative structure–activity relationship studies were performed on these compounds using physicochemical parameters
as independent parameters and antifungal activity as a dependent parameter, where antifungal activity correlated best (correlation
coefficient r > 0.8) with physicochemical parameters (Hammett’s constants σ
p
, F) and van der Waals volume V
1. Results are interpreted on the basis of multiple regression and cross-validation methodology. Furthermore, the domain of
applicability which indicates the area of reliable predictions is defined.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Chemical structures of A1–26 and A39; synthetic procedures; synthesis schemes; mps, yields, 1H NMR; elemental analyses of compounds and single crystal X-ray diffraction of compounds. 相似文献
74.
Akbar Ali Mohammad Huq Mirza Aminul Haji Iran Malai Shah Butcher Ray J. Tarafder M.T.H. Boon Keat Tan Manaf Ali A. 《Transition Metal Chemistry》2002,27(3):262-267
Copper(II) complexes of general formula, Cu(NNS)X
2 · nH2O (NNS = the 2-formylpyridine Schiff base of N-methyl-S-methyldithiocarbazate; X = Cl–, Br–, I–, NCS–; n = 0, 2) have been synthesized and characterized by elemental analysis and by magnetic and spectroscopic techniques. Based on magnetic and spectroscopic data, a monomeric five-coordinate square-pyramidal structure is assigned to these complexes. The crystal and molecular structure of [Cu(NNS)I2] has been determined by X-ray diffraction. The complex has a monomeric square-pyramidal structure with the ligand coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thione sulfur atom. The fourth and fifth coordination sites are occupied by the iodide ligands. Antimicrobial tests indicate that Schiff base is inactive against the bacteria, Bacillus subtilis (mutant defective DNA repair), Pseudomonas aeruginosa, methicillin resistant Staphylococcus aureus and Bacillus subtilis (wild type) and weakly active against the fungi, Candida albicans, Candida lypolytica, Saccharomyces cereviseae and Aspergillus ochraceous but its copper(II) complexes, Cu(NNS)X
2 are strongly active against these organisms. A cytotoxicity study of the compounds against leukemic and cervical cancer cells showed that the Schiff base is inactive, but the complexes, [Cu(NNS)I2] and [Cu(NNS)(NCS)2] · 2H2O exhibit significant activity against cervical cancer cells with CD50 values of 4.8 and 4.2 g, respectively. 相似文献
75.
Ali Jebali Seyedhossein Hekmatimoghaddam Aliasghar Behzadi Iraj Rezapor Bahador Haji Mohammadi Tahereh Jasemizad Seyed Ali Yasini Morteza Javadzadeh Asiye Amiri Mansoure Soltani Zeynab Rezaei Najme Sedighi Mina Seyfi Mohammad Rezaei Mehran Sayadi 《Cellulose (London, England)》2013,20(6):2897-2907
In this study, cellulose nanoparticles were prepared by acid hydrolysis, separately conjugated with allicin and lysozyme by a carbodiimide cross-linker, and characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Then, their antimicrobial properties were evaluated by the microdilution method and compared with allicin, lysozyme, and nanocellulose alone. The results showed that nanocellulose had few antimicrobial activities, but allicin-conjugated nanocellulose (ACNC) and lysozyme-conjugated nanocellulose (LCNC) had good antifungal and antibacterial effects against standard strains of Candida albicans, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Noticeably, although allicin and lysozyme had different minimum inhibitory concentrations (MICs) against all strains, the same quantity of MIC50 and MIC90 was observed for both ACNC and LCNC. The authors suggest that both ACNC and LCNC can be used in industries as an antimicrobial agent in food packaging, inside foodstuffs, and in textile materials. 相似文献
76.
Muhammad Haji Hanif Muddasir Tahiri Iftikhar Ahmad Versiani Muhammad Ali Shah Faheem Khaliq Obaid Ali Syed Tahir Ahmed Safeer 《Research on Chemical Intermediates》2018,44(10):6387-6400
Research on Chemical Intermediates - Among the reactive oxygen species, the superoxide anion radical (O 2 ·? ) has a fundamental role in several biological functions. Consequently, its... 相似文献
77.
78.
Pourjavid Mohammad Reza Hosseini Majid Haji Rezaee Mohammad Ashouri Mitra 《Structural chemistry》2018,29(2):615-624
Structural Chemistry - 3-(chloro(2-methyl-1H-indol-3-yl)methyl)-2-methyl-1H-indole (MIMI) was chosen for separation and preconcentration of iron (III), copper (II), and zinc by solid-phase... 相似文献
79.
Green and effective route for the synthesis of monodispersed palladium nanoparticles using herbal tea extract (Stachys lavandulifolia) as reductant,stabilizer and capping agent,and their application as homogeneous and reusable catalyst in Suzuki coupling reactions in water 下载免费PDF全文
Hojat Veisi Ramin Ghorbani‐Vaghei Saba Hemmati Majid Haji Aliani Turan Ozturk 《应用有机金属化学》2015,29(1):26-32
A simple and eco‐friendly procedure has been devised for the green synthesis of palladium nanoparticles, using the aqueous extract of herbal tea (Stachys lavandulifolia), a renewable and nontoxic natural phyto‐exudate. The water‐soluble components of the extract act as reducing agent and stabilizer. This green route does not require a surfactant or capping agent for the growth of palladium nanoparticles. The generated nanoparticles were analysed using UV–visible spectroscopy, transmission electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X‐ray analysis and inductively coupled plasma. The palladium nanoparticles having spherical shape and dimensions of between 5 and 7 nm were employed as a homogeneous catalyst for Suzuki coupling reactions conducted in water under mild conditions. Good yields of products, a facile work‐up, no evidence of leached palladium from the catalyst surface and smooth recovery of the catalysis by adding ethyl acetate, which could be reused at least eight times, confirm the very good efficiency of the catalytic reaction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
80.