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131.
Microwave-assisted synthesis and antioxidant properties of hydrazinyl thiazolyl coumarin derivatives
ABSTRACT: Coumarin derivatives exhibit a wide range of biological properties including promising antioxidant activity. Furthermore, microwave-assisted organic synthesis has delivered rapid routes to N- and O-containing heterocycles, including coumarins and thiazoles. Combining these features, the use of microwave-assisted processes will provide rapid access to a targeted coumarin library bearing a hydrazino pharmacophore for evaluation of antioxidant properties. RESULTS: Microwave irradiation promoted 3 of the 4 steps in a rapid, convergent synthesis of a small library of hydrazinyl thiazolyl coumarin derivatives, all of which exhibited significant antioxidant activity comparable to that of the natural antioxidant quercetin, as established by DPPH and ABTS radical assays. CONCLUSIONS: Microwave dielectric heating provides a rapid and expedient route to a series of hydrazinyl thiazolyl coumarins to investigate their radical scavenging properties. Given their favourable properties, in comparison with known antioxidants, these coumarin derivatives are promising leads for further development and optimization. 相似文献
132.
Aybüke A. ?sbir-Turan Emine K?l?? Zafer üstünda? Haslet Ek?i Ali Osman Solak Betül Zorer 《Journal of Solid State Electrochemistry》2012,16(1):235-245
The goal of this study was to prepare novel glassy carbon electrode surfaces using two similar bis-diazonium salts, 3,8-benzo[c]cinnoline (3,8-BCC-BDAS) and 3,8-benzo[c]cinnoline 5-oxide (3,8-BCCNO-BDAS) at the glassy carbon (GC) surface. These diazonium salts were reduced electrochemically
and covalently electrografted onto the glassy carbon electrode surface to form modified electrodes. Electrochemical reduction
of 3,8-BCC-BDAS and 3,8-BCCNO-BDAS salts on the electrode surface yielded a compact and stable film. The existence of BCC
moieties on the GC surface was characterized by X-ray photoelectron spectroscopy, reflectance-adsorption infrared spectroscopy,
cyclic voltammetry, ellipsometry, and electrochemical impedance spectroscopy. The stability and working potential range of
the novel modified electrodes were also studied. The possibility of analytical application of these novel surfaces for inorganic
cations and especially selectivity to copper ions was investigated. 3,8-diaminobenzo[c]cinnoline (3,8-DABCC) and its 5-oxide derivative (3,8-DABCCNO) were synthesized from the reductive cyclization of 2,2′-dinitrobenzidine
and prepared their bisdiazonium salts via the tetrazotization reactions of the diamines with NaNO2. The structures of 3,8-DABCC and 3,8-DABCCNO and their corresponding bisdiazonium salts are confirmed by spectral analysis. 相似文献
133.
Secil Tekin-Celebi Ali Osman Solak Zafer Ustundag Serkan Demirci 《Chemical Papers》2012,66(12):1146-1156
Acidity constant values of benzoic acid (BA)-modified platinum electrode (Pt-BA) and p-aminobenzoic acid (pABA)-modified platinum electrode (Pt-NHBA) surfaces were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and contact angle measurements (CAM). Diazonium tetrafluoroborate salt reduction and pABA oxidation reactions were used to prepare (Pt-BA) and (Pt-NHBA) surfaces, respectively. Both surfaces exhibited pH dependence with [Fe(CN)6]3?/4? redox probe solutions at different pH; this allowed us to estimate the surface pK a values. Acidity constants for Pt-BA surface were found to be pK a (3.09 ± 0.25), (4.89 ± 0.11), and (3.91 ± 0.54) by CV, EIS, and CAM techniques, respectively, while the values for Pt-NHBA surface were pK a (3.16 ± 0.45), (4.24 ± 0.40), and (5.64 ± 0.12). The Pt-BA surface pK a values were lower in CV and CAM measurements relative to the bulk solution of BA, while a higher value was observed in EIS for Pt-BA surface. The pK a values determined for Pt-NHBA surface via both CV and EIS were lower than the bulk value; however, the result obtained from CAM was one unit higher than pK a of bulk pABA. 相似文献
134.
Ru(II) complexes of the general formula [RuCl2(′′)(L)] (1: ′N = Nb, L = MeOH; 2: ′N = Nb, L = CH3CN; 3: ′N = Nd, L = CH3CN; 4: ′N = Np, L = CH3CN), [Ru(p‐cymene)(a–b)Cl]Cl (5a: N Na = 2,2′‐bipyridine; 5b: N Nb = 4,4′‐dimethyl–2,2′‐bipyridine), [Ru(′′)(a–b)Cl]Cl (6a: ′N = Nb, a = 2,2′‐bipyridine; 6b: ′N = Nb, b = 4,4′‐dimethyl‐2,2′‐bipyridine; 7a: ′N = Nd, a = 2,2′‐bipyridine; 7b: ′N = Nd, b = 4,4′‐dimethyl‐2,2′‐bipyridine; 8a: ′N = Np, a = 2,2′‐bipyridine; 8b: ′N = Np, b = 4,4′‐dimethyl‐2,2′‐bipyridine) and [Ru(′′)(a)Cl]BF4 (9a: ′N = Nb; a = 2,2′‐bipyridine) were synthesized from the corresponding [RuCl2(p‐cymene)]2 dimer, ′′ and a–b ligands. The compounds were characterized by elemental analysis, IR and NMR. Complex 9a was studied by X‐ray diffraction, confirming its cationic‐mononuclear [RuCl(bb)(a)]+ nature. The synthesized Ru(II) complexes (1–8) were employed as catalysts for the transfer hydrogenation of ketones to secondary alcohols in the presence of KOH using 2‐propanol as a hydrogen source at 82°C. The rates of the transfer hydrogenation reactions strongly depended on the type of and ancillary ligands. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
135.
Osman Canko Ahmet ErdinçFerhat Ta?k?n Ali Fuat Y?ld?r?m 《Journal of magnetism and magnetic materials》2012,324(4):508-513
The magnetization of a cylindrical Ising nano-tube is investigated by the use of the effective field theory with correlations. The effects of the crystal field couplings at the surface shell to the order parameters, susceptibility, internal energy, specific heat and free energy are investigated. Some characteristic phenomena are examined in the thermal variations, depending on crystal field term. Moreover, tricritical and critical points are found on the (D/J,kT/J) plane, where D/J and kT/J are reduced crystal-field and temperature, respectively. 相似文献
136.
Z. Osman 《Journal of Thermal Analysis and Calorimetry》2012,107(2):709-716
In this article, autocondensation reactions of Acacia nilotica spp. nilotica (Ann) tannin extracts solutions have been studied at several pH values by thermomechanical analyzer (TMA). TMA has been chosen
for this study as it has been shown to give results more rapidly and more precisely than panels. It also tends to exaggerate
the differences in results which render it an excellent tool for comparison. Therefore, autocondensation reactions were studied
and compared with its polycondensation reactions upon addition of different hardeners such as paraformaldehyde, urea, and
PMDI at same pH values. The aim was to evaluate the tannin’s reactivity and therefore its suitability for the production of
commercially and technically viable tannin adhesives for wood products. The results of autocondensation showed that the maximum
Young’s modulus values (3300 and 3600 MPa) were obtained at pH 4. However, these values have been achieved at high temperature
(160 and 208 °C). Results of copolymerization reaction of the tannins with different hardeners revealed that some of these
co-reactants were found to depress tannins autocondensations, while others appear to enhance the formation of the final networking.
Polycondensation of the Ann tannins with 8% paraformaldehyde and 10% PMDI gave the maximum Young’s modulus values at lower
temperature (91–101 °C) and acidic pH5. However, the addition of 20 and 30% PMDI achieved the best Young’s modulus values
2300 and 3300 MPa, respectively, at pH 4. Furthermore, the obtained values were comparable to those obtained by the addition
of urea and the self condensation reactions. This is very important for particleboard production from economical and technical
point of view. It has been noticed that the addition of hardeners lowered the temperature of hardening, and the obtained values
were more consistent with the pH acidity. The study concluded that the tannins of Ann were very reactive, and therefore, it
could be a potential precursor for particleboard adhesives. The results also indicated that the tannins can be used alone,
and it would possibly produce zero emission environmentally friendly particleboard. 相似文献
137.
Hussein Osman Ammar S. A. El-Nahhas M. M. Ghorab A. H. Salama 《Journal of inclusion phenomena and macrocyclic chemistry》2012,72(1-2):127-136
One of the most attractive areas of research in drug delivery is the design of nanomedicines consisting of nanosystems that are able to deliver drugs to the right place, at appropriate time. Natural polysaccharides, due to their outstanding merits, have received more and more attention in the field of drug delivery systems. In particular, polysaccharides seem to be the most promising materials in the preparation of nanometric carriers. The main goal of the present study was to investigate the potential of a recent generation of hybrid polysaccharide nanocarriers, composed of chitosan (CS) and an anionic cyclodextrin, carboxymethyl-β-cyclodextrin (CM-β-CD), for the encapsulation of a model drug, sulindac. CS and CM-β-CD were processed to nanoparticles (NPs) via the ionotropic gelation technique. The stoichiometric ratio between these two polymers was found to influence particle size and zeta potential. Decreasing CS:CM-β-CD ratio led to an increase in particle size and decrease in zeta potential. DSC and FTIR analyses confirmed formation of NPs and encapsulation of sulindac inside them. Release profiles indicate a continuous release of the drug throughout 24?h. However, the rate of release was more rapid during the first hours; about 55–90% of the drug being released after 3?h. 相似文献
138.
Osman B Özer ET Kara A Güçer Ş Beşirli N 《Journal of colloid and interface science》2012,378(1):167-174
The barium hexaferrite (BaFe(12)O(19)) containing magnetic poly (ethylene glycol dimethacrylate-vinyl pyridine; mag-poly [EGDMA-VP]) beads (average diameter=53-212 μm) were synthesized and characterized. Their use as an adsorbent in the removal of dimethyl phthalate (DMP) from an aqueous solution was investigated. The mag-poly (EGDMA-VP) beads were prepared by copolymerizing of 4-vinyl pyridine (VP) with ethylene glycol dimethacrylate (EGDMA). The mag-poly (EGDMA-VP) beads were characterized by N(2) adsorption/desorption isotherms (BET), vibrating sample magnetometer (VSM), X-ray powder diffraction (XRD), elemental analysis, scanning electron microscope (SEM), and swelling studies. At a fixed solid/solution ratio, the various factors affecting the adsorption of DMP from aqueous solutions such as pH, initial concentration, contact time, and temperature were analyzed. The maximum DMP adsorption capacity of the mag-poly (EGDMA-VP) beads was determined as 96.2 mg/g at pH 3.0, 25 °C. All the isotherm data can be fitted with both the Langmuir and the Dubinin-Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order, Ritch-second-order, and intraparticle diffusion models were used to describe the adsorption kinetics. The thermodynamic parameters obtained indicated the exothermic nature of the adsorption. The DMP adsorption capacity did not change after 10 batch successive reactions, demonstrating the usefulness of the magnetic beads in applications. 相似文献
139.
Goyal K.O. Mahalingam R. Pedrow P.D. Osman M.A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》2001,29(1):42-50
A pulsed plasma enhanced chemical vapor deposition (PECVD) reactor is used for the preparation of thin polyacetylene films. A theoretical model based on the mass transport characteristics of the reactor is developed in order to correlate with experimentally obtained spatial deposition profiles for the acetylene plasma polymer film deposited within the cylindrical reactor. Utilizing a free radical mechanism with gas phase initiation of the polymerization reaction as the rate controlling step, a system parametric study is performed to predict the Peclet number range of operation for the pulsed PECVD reactor. This parametric study indicates radical decay by diffusion to the reactor walls to be the significant physical phenomenon in the system. It is concluded that a quasi-steady-state model is a good tool for predicting the important mass transfer phenomena occurring in the pulsed plasma reactor 相似文献
140.
Transition metal complexes of ditertiary aminomethylphosphine ligand, (Ph2PCH2)NCH3 [N,N‐bis(diphenylphospinomethyl)aminomethane], dppam, with metal ions which are Ag(I), Au(I), Cu(I), and Co(II) have been synthesized under nitrogen atmosphere by the Schlenk method. [Ag(dppam)2]NO3 ( 1 ), [Au(dppam)2]Cl ( 2 ), and [Cu(dppam)2]Cl ( 3 ) complexes have been isolated as colorless solids, whereas [CoCl2(dppam)] ( 4 ) complex as a blue solid. All complexes have been characterized by atomic absorption, FT‐IR, NMR (1H, 13C, 31P) spectroscopic, thermogravimetric/differantial thermal analysis (TG/DTA), and elemental analysis techniques. Antimicrobial activity of 1 , 2 , 3 , and 4 were studied in vitro on 13 bacteria and 4 yeasts. The cobalt(II) phosphine complex has shown the best antimicrobial activity in comparison with the other metal complexes. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:484–491, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20145 相似文献