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排序方式: 共有123条查询结果,搜索用时 31 毫秒
91.
Maha A. Aboul Ela Abdalla M. El‐Lakany Maged S. Abdel‐Kader Saleh I. Alqasoumi Safa M. Shams‐El‐Din Hala M. Hammoda 《Helvetica chimica acta》2012,95(1):61-66
Fractionation directed by hepatoprotective activity of Inula crithmoides L. root resulted in the isolation of two new quinic acid derivatives, 3,5‐di‐O‐caffeoylquinic acid 1‐methyl ether ( I ; caffeoyl=(E)‐3‐(3,4‐dihydroxyphenyl)prop‐2‐enoyl; quinic acid=1,3,4,5‐tetrahydroxycyclohexanecarboxylic acid) and 4,5‐di‐O‐caffeoylquinic acid 1‐methyl ether ( II ), in addition to the well‐known hepatoprotective compound, 1,5‐di‐O‐caffeoylquinic acid ( III ). The hepatoprotective effect was indicated by the significant decrease in the level of four measured serum biochemical parameters (SGOT, SGPT, ALP, and bilirubin) in experimental rats. The structures of the isolated compounds were determined by analyses of 1D‐ and 2D‐NMR spectroscopic data. 相似文献
92.
Deferiprone and other 3-hydroxy-4-pyridinones are used in metal chelation therapy of iron overload. To investigate the structure and stability of these compounds in the natural aqueous environment, ferric complexes of deferiprone and amino acid maltol conjugates were synthesized and studied by computational and optical spectroscopic methods. The complexation caused characteristic intensity changes, a 300× overall enhancement of the Raman spectrum, and minor changes in UV-vis absorption. The spectra were interpreted on the basis of density functional theory (DFT) calculations. The CAM-B3LYP and ωB97XD functionals with CPCM solvent model were found to be the most suitable for simulations of the UV-vis spectra, whereas B3LYP, B3LYPD, B3PW91, M05-2X, M06, LC-BLYP, ωB97XD, and CAM-B3LYP functionals were all useful for simulation of the Raman scattering. Characteristic Raman band frequencies for 3-hydroxy-4-pyridinones were assigned to molecular vibrations. The computed conformer energies consistently suggest the presence of another isomer of the deferiprone-ferric complex in solution, in addition to that found previously by X-ray crystallography. However, the UV-vis and Raman spectra of the two species are similar and could not be resolved. In comparison to UV-vis, the Raman spectra and their combination with calculations appear more promising for future studies of iron sequestrating drugs and artificial metalloproteins as they are more sensitive to structural details. 相似文献
93.
Cyril Koughia Go Okada Dancho Tonchev Safa Kasap Andy Edgar Christopher R. Varoy Heinz von Seggern 《Journal of Non》2011,357(11-13):2272-2277
Photoluminescence (PL) and conventional and modulated temperature differential scanning calorimetry (DSC and MDSC) experiments have been carried out on a typical fluorochlorozirconate glass and glass-ceramics doped with Sm3+ and Sm2+ introduced by the addition of SmF3 and a reducing agent, NaBH4, into the initial mixture of constituents. The nominal FCZ composition was 53% ZrF4, 20% NaF, 3% AlF3, 3% LaF3, 1% SmF3, 1% BaF2, 19% BaCl2 (molar percentages). Prior to DSC and PL measurements, some of the glasses have been heat treated (annealed at an elevated temperature) under different conditions, which has resulted in glass-ceramics containing BaCl2 nanocrystals with a hexagonal and/or orthorhombic crystal structure, depending on the heat treatment conditions. Hexagonal nanocrystals may be obtained by a simple one step annealing process while the formation of orthorhombic crystallites requires sequential multistep annealing treatments. Long duration, low temperature annealing, required for the formation of orthorhombic BaCl2 nanocrystals, leads to the appearance of an endothermic enthalpy peak at around 250 °C on the conventional DSC thermogram. Temperature modulated DSC experiments identify a clear glass transformation in this regions; and the endothermic peak has been attributed to the structural relaxation enthalpy in the host glass which is usually obscured by the thermal effects associated with the formation of BaCl2 nanocrystals. The observed thermodynamic effects correlate with the suppression of the broad PL band around 900 nm, which is most likely due to Sm2+ ions near or in the “shell-region” of the glass surrounding the nanocrystals. 相似文献
94.
Kazem D. Safa Mina Namvari Shahin Tofangdarzadeh 《Journal of organometallic chemistry》2009,694(15):2448-1051
The synthesis of various vinylbis(silanes) from some aryl and heteroaryl aldehydes and (Me3Si)3CLi in Et2O is described. Friedel-Crafts reaction of 1,1-bis(trimethylsilyl)-2-(2-naphthyl)ethene with various acyl chlorides (RCOCl, R = Me, Et, i-Pr, i-Bu, n-pent) gave the corresponding α-silyl-α,β-unsaturated enones with high E steroselectivity. Moreover, poly(styrene)-co-[2,2-bis(trimethylsilyl)ethenyl(styrene)] obtained via the reaction of polymers bearing pendant enone functions and (Me3Si)3CLi, reacts with the same acyl chlorides in the presence of catalytic amount of AlCl3 to give the new macromolecules bearing α-silyl-α,β-unsaturated enones and α,β-unsaturated enones. 相似文献
95.
Reaction of the iodides TsiSiMe2I and TsiSiPh2I, (Tsi (Me3Si)3C) with AgClO4 in t-BuOH provides a route to the silanols TsiSiMe2OH and (Me3Si)2-C(SiPh2Me)(SiMe2OH), respectively. TsiSiMe2OH gives the disiloxane TsiSiMe2OSiMe3 when treated with either (a) Me3SiOClO3 (prepared in situ from AgClO4 and Me3SiCl) in benzene, (b) Me3SiI (in the presence of a little (Me3Si)2-NH), (c) O,N-bis(trimethylsilyl)acetamide, or (d) MeLi followed by Me3SiCl. It does not react with Me3SiCl, but with Me2SiCl2 gives TsiSiMe2OSiMe2Cl, and with CH3COCl gives TsiSiMe2OCOCH3. The disiloxane is stable to methanolic acid or base, but reacts with KOH in H2O/Me2SO and with CF3COOH to give TsiSiMe2OH. The disiloxane (Me3Si)2C(SiPh2Me)(SiMe2OSiMe3) is formed by treatment of (Me3Si)2C(SiPh2Me)(SiMe2OH) with Me3SiI/(Me3Si)2NH. Treatment of TsiSiPhMeI with AgClO4 in t-BuOH gives the silanols TsiSiPhMeOH and (Me3Si)2C(SiPhMe2)(SiMe2OH) (which with Me3SiI/(Me3Si)2NH give the corresponding disiloxanes) along with some of the t-butoxide (Me3Si)2C(SiPhMe2)(SiMe2OBut). 相似文献
96.
Detection of Explosive Vapors: The Roles of Exciton and Molecular Diffusion in Real‐Time Sensing
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Dr. Mohammad A. Ali Dr. Safa Shoaee Dr. Shengqiang Fan Prof. Paul L. Burn Prof. Ian R. Gentle Prof. Paul Meredith Dr. Paul E. Shaw 《Chemphyschem》2016,17(21):3350-3353
Time‐resolved quartz crystal microbalance with in situ fluorescence measurements are used to monitor the sorption of the nitroaromatic (explosive) vapor, 2,4‐dinitrotoluene (DNT) into a porous pentiptycene‐containing poly(phenyleneethynylene) sensing film. Correlation of the nitroaromatic mass uptake with fluorescence quenching shows that the analyte diffusion follows the Case‐II transport model, a film‐swelling‐limited process, in which a sharp diffusional front propagates at a constant velocity through the film. At a low vapor pressure of DNT of ≈16 ppb, the analyte concentration in the front is sufficiently high to give an average fluorophore–analyte separation of ≈1.5 nm. Hence, a long exciton diffusion length is not required for real‐time sensing in the solid state. Rather the diffusion behavior of the analyte and the strength of the binding interaction between the analyte and the polymer play first‐order roles in the fluorescence quenching process. 相似文献
97.
Since to the best of our knowledge, there is no potentiometric sensors based on carbon paste electrodes were proposed for the potentiometric determination of molybdenum(VI) ion. In this study, 2,2′-(propane-1,3-diylbis(oxy))dibenzoic acid (PBODBA) was synthesized and used as modifier in the fabrication of carbon paste electrode (CPE) for the quantification of molybdenum(VI). The developed electrodes I and II showed hexavalent Nernstian response of 9.80±0.05 and 9.90±0.08 mV decade−1 over the concentration ranges of 1.0×10−7–1.0×10−3 and 1.0×10−8–1.0×10−3 mol L−1, respectively. The electrodes showed good selectivity for Mo(VI). The modified electrodes were applied for the determination of Mo(VI) concentration in masscuaje agricultural fertilizer and spiked juice extractions containing several metals. 相似文献
98.
K. D. Safa A. Hassanpour S. Tofangdarzadeh M. H. Nasirtabrizi 《Journal of the Iranian Chemical Society》2008,5(3):458-463
It is known that metalation of (RMe2Si)3CH (R: a = Me, b = Ph) with MeLi in THF yields (RMe2Si)3CLi, which when reacted with allyl bromide, (RMe2Si)3C-CH2-CH=CH2 (1a, 1b) are produced. In this study, although (PhMe2Si)3CLi does not react with benzyl bromide, under the same conditions (Me3Si)3CLi does, giving the expected product. We found that the bromination of 1b was unsuccessful and the reaction of 1a occurs in low yield due to severe steric hindrance. This idea is supported by our results, which show that, when treated with dichlorocarbene and dibromocarbene, 1a and 1b yield the related dihalocyclopropanes. Furthermore, reduction of the obtained products gives the dehalogenated compounds. 相似文献
99.
Kazem D. Safa Mohammad Shahrivar Shahin Tofangdarzadeh Akbar Hassanpour 《Journal of heterocyclic chemistry》2008,45(2):389-395
100.
Kazem D. Safa Soleiman Paymard Samani Shahin Tofangdarzadeh Akbar Hassanpour 《Journal of organometallic chemistry》2008,693(11):2004-2008
1,1-Bis(trimethylsilyl)-2-phenylethylene (1), which has been synthesized from the Peterson reaction between (Me3Si)3CLi and benzaldehyde, reacts with various acyl chlorides (RCOCl, R = Me, Et, iso-Pr, n-Bu, iso-Bu, iso-C5H11, PhCH2, PhCH2CH2) in the presence of AlCl3 to give -silyl-,β-unsaturated enones 3a–3h with high E stereoselectivity along with trans-,β-unsaturated ketones 4a–4h. The enones 3 can be partially converted into the ketones 4 with an excess of AlCl3. Reaction of 1 with RCOCl, (R = Ph, CH3CH=CH) afforded only the ketones 4. Yields were dependent on time and the amounts of AlCl3 used. 相似文献