全文获取类型
收费全文 | 77篇 |
免费 | 1篇 |
专业分类
综合类 | 1篇 |
化学工业 | 45篇 |
金属工艺 | 3篇 |
能源动力 | 1篇 |
轻工业 | 15篇 |
石油天然气 | 3篇 |
无线电 | 1篇 |
一般工业技术 | 8篇 |
自动化技术 | 1篇 |
出版年
2022年 | 1篇 |
2018年 | 1篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2014年 | 9篇 |
2013年 | 9篇 |
2012年 | 7篇 |
2011年 | 7篇 |
2010年 | 3篇 |
2009年 | 6篇 |
2008年 | 9篇 |
2007年 | 5篇 |
2006年 | 1篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 2篇 |
2000年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1994年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
排序方式: 共有78条查询结果,搜索用时 0 毫秒
1.
Some substituted coumarins have been synthesized by von-Pechmann condensation using SnCl2 · 2H2O (10 mol %) as catalyst in ethanolic medium. The reactions are simple, easy in handling and environmentally benign. 相似文献
2.
Majid M. Heravi Marzieh Khorasani Fatemeh Derikvand Hossein A. Oskooie Fatemeh F. Bamoharram 《Catalysis communications》2007,8(12):1886-1890
A variety of heteropolyanions including: Keggin, Dawson, Preyssler, mixed addenda and sandwich types, catalyzed the formation of 4-methylnaphtho-(1,2-b)-pyran-2-one (coumarin) from the condensation of α-naphthol and ethylacetoacetate in a solvent free system and under heating conditions. Our data vividly indicate that sodium30–tungsto pentaphosphate, [NaP5W30O110]14−, which so-called Preyssler’s anion, with high hydrolytic (pH 0–12) and thermal stability is the catalyst of choice. This catalyst catalyzed the synthesis of other coumarin derivatives in high yields and good selectivity. 相似文献
3.
Ki-Pung Yoo Hun Yong Shin Min Jeong Noh Seong Sik You 《Korean Journal of Chemical Engineering》1997,14(5):341-346
To design a supercritical fluid extraction process for the separation of bioactive substances from natural products, a quantitative
knowledge of phase equilibria between target biosolutes and solvent is necessary. How-ever, mostly no such information is
available in literature to date. Thus in the present study, illustratively the solubility of bioactive coumarin and its various
derivatives (i.e., hydroxy-, methyl-, and methoxy-derivatives) in supercritical CO2 were measured at 308.15–328.15 K and 10–30 MPa. Also, the pure physical properties such as normal boiling point, critical
constants, acentric factor, molar volume and standard vapor pressure for coumarin and its derivatives were estimated. By these
estimated information, the measured solubilities were quantitatively correlated by an approximate lattice equation of state
proposed recently by the present authors. 相似文献
4.
The performance of DSSCs (dye sensitized solar cells) with a new series of dyes having different halide groups (i.e. F, Cl and Br) on o-position substituted phenyl spacers with same coumarin donor moieties have been reported. Optical, electrochemical, molecular orbital and photovoltaic properties were studied by varying the halide groups using these dyes. The replacement of halide atoms in same coumarin based dye had a significant effect on the short circuit current density (Jsc), open circuit voltage (Voc), and photo conversion efficiency (PCE). The Jsc and PCE of dye CD-1 (fluorine substituted) are 10.3 mA/cm2 and 5.2% respectively, which is higher than CD-2 (chlorine substituted) and CD-3 (bromine substituted) dyes (having PCE 4.1% and 3.5% respectively) devices. The optimized geometry calculation of o-halide phenyl π-spacer dyes were ascertained by density functional theory (DFT) using the B3LYP/6-31G(d,p) basis set. Moreover, we have checked the effect of various substituents in the same dye structure by DFT analysis. 相似文献
5.
6.
H. Abd El-Wahab M. Abd El-Fattah N. Abd El-Khalik Hesham S. Nassar Mahmoud M. Abdelall 《Progress in Organic Coatings》2014
Coumarin, thiazole and their respective derivative products are some of the oldest and most commonly known class of nitrogen and sulphur containing compounds. In recent years there has been considerable interest in this coumarin–thiazole derivatives, which have been reported to exhibit significant biological activity and are widely used as pharmaceuticals. They are capable of imparting anti-microbial activity properties when incorporated into polymers and polymer composites. In this research, coumarin–thiazole derivative 2-(2-amino-1,3-thiazol-4-yl)-3H benzo[f]chromen-3-one (compound III), was prepared and its structure was confirmed by means of its spectra data. It was also screened for its anti-microbial activity against eight different micro-organisms when physically incorporated into a polyurethane varnish formula. Experimental coatings were manufactured on a laboratory scale and applied by means of a brush on both glass and steel panels. The results of the biological activity indicated that the polyurethane varnishes containing the 2-(2-amino-1,3-thiazol-4-yl)-3H-benzo[f]chromen-3-one (compound III) derivative, exhibit a very good antimicrobial effect. The molecular modeling study revealed that it is biologically safe, it is active and it fulfills Lipinski's rule of five. The physical and mechanical resistances of the polyurethane varnish formulations were also studied to evaluate any drawbacks associated with the addition of the derivative. The studies indicate that the physical incorporation of compound III actually enhances slightly both the physical and mechanical properties. 相似文献
7.
Hee Jung Kim Ji Eun Park Myung Gil Choi Sangdoo Ahn Suk-Kyu Chang 《Dyes and Pigments》2010,84(1):54-58
A novel, Hg2+-selective chemosensor was prepared via Mannich reaction of dichlorofluorescein with piperazinyl-coumarin moiety. The dichlorofluorescein–coumarin derivative exhibited well-defined Hg2+-selective chromogenic behavior, indicated by a green to pink colour change in solution, as well as fluorogenic signalling. Significant changes in fluorescence of the dichlorofluorescein subunit were analyzed in reference to the rather constant coumarin emission as an internal standard yielding Hg2+ selectivity. The Hg2+ selectivity of the chemosensor was not appreciably affected by the presence of common coexisting alkali, alkaline earth, and transition metal ions. The detection limit of the dichlorofluorescein–coumarin conjugate for the determination of Hg2+ ions was 4.3 × 10−6 mol L−1 and the conjugate dye could be used as a chemosensor for the analysis of Hg2+ ions in aqueous environments. 相似文献
8.
Effect of coumarin and xanthotoxin on mitochondrial structure,oxygen uptake,and succinate dehydrogenase activity in onion root cells 总被引:1,自引:0,他引:1
Ewa Kupidlowska Katarzyna Dobrzynska Eugeniusz Parys Alicja M. Zobel 《Journal of chemical ecology》1994,20(10):2471-2480
At concentrations in which they occur on the plant surface and retard mitosis, coumarin and xanthotoxin lowered uptake of oxygen (by 60 and 30%, respectively) by meristematic cells ofAllium cepa root tips. They caused changes in the structure of the mitochondrial matrix to become dense, and protrusions of mitochondrial membranes were visible parallelling their hypertrophy, indicating alteration in the structure and physiology of these organelles. Coumarin and, to a lesser extent, xanthotoxin increased succinate dehydrogenase production in mitochondria and also in the cytoplasm, indicating changes in membrane permeability. Changes in oxygen uptake and mitochondrial structure, in addition to the retardation of mitosis, may be the reason these compounds act as allelochemicals after they have been removed from the plant surface and reach the root meristem. 相似文献
9.
Sanjay Kumar 《材料科学与工程:中英文B版...》2014,(12):358-365
In the present work, an array of novel substituted 2H-chromen-2-one (coumarin derivatives abbreviated as C-337, C-480, C-540A) has been subjected to photophysical analysis. Although the influence of the electron donating groups such as amino, substituted amino, hydroxyl, alkoxy groups at position 7 of the coumarin ring system has been extensively studied, However, coumarin moieties with substituent at position 3 have not been explored much. Attempt is made to explain the effect of electron donating and electron accepting substituent on excited state and ground state dipole moment. The ground state (μ) and excited state (μ*) dipole moment of C-337, C-480, C-540A coumarins are estimated from solvatochromic shift of absorption and fluorescence spectra as a function of the dielectric constant and refractive index using Bakhshiev and Kwaski-Chamma Vialletequ. μ* and μ for all the reported coumarin are also calculated using Reichardt correlation method. The small angle is also reported between the ground and excited state dipole moment suggesting that they are almost parallel to each other. Excited state dipole moment is observed larger than ground state dipole moment for all the coumarins studied indicating substantial n-electron density redistribution. 相似文献
10.