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341.
Tautvydas Venckus Raimonda Celiešiūtė Aneta Radzevič Tomas Rakickas Šarūnas Vaitekonis Živilė Ruželė Rasa Pauliukaite 《Electroanalysis》2014,26(10):2273-2282
Folic acid was polymerised electrochemically at a glassy carbon electrode surface from 0.1 mol L?1 phosphate buffer saline solution, pH 5.0, containing 0.1 mmol L?1 monomer. The obtained thin film was porous with a pore size of 50–60 nm. Since its electrochemical stability was rather short, the polyfolate film was covered with a graphene‐chitosan composite layer which increased its stability significantly. The best strategy to immobilise the enzyme was crosslinking with glutaraldehyde. The lifetime of this glucose biosensor in use was at least 12 days, on‐shelf life time was at least 30 days. The linear range was up to 1 mmol L?1 and the LOD was 0.6 µmol L?1. The first polyfolate‐based biosensor was applied to analysis of natural samples. 相似文献
342.
K. Juodkazis J. Juodkazytė V. Šukienė A. Grigucevičienė A. Selskis 《Journal of Solid State Electrochemistry》2008,12(11):1399-1404
Comparative study of capacitative properties of RuO2/0.5 M H2SO4 and Ru/0.5 M H2SO4 interfaces has been performed with a view to find out the nature of electrochemical processes involved in the charge storage
mechanism of ruthenium (IV) oxide. The methods of cyclic voltammetry and scanning electron microscopy (SEM) were employed
for the investigation of electrochemical behavior and surface morphology of RuO2 electrodes. It has been suggested that supercapacitor behavior of RuO2 phase in the potential E range between 0.4 and 1.4 V vs reference hydrogen electrode (RHE) should be attributed to double-layer-type capacitance,
related to non-faradaic highly reversible process of ionic pair formation and annihilation at RuO2/electrolyte interface as described by following summary equation:
where and represent holes and electrons in valence and conduction bands, respectively. The pseudocapacitance of interface under investigation
is related to partial reduction of RuO2 layer at E < 0.2 V and its subsequent recovery during the anodic process. 相似文献
343.
Birutė Kazakevičienė Gintaras Valinčius Marytė Kažemėkaitė Valdemaras Razumas 《Electroanalysis》2008,20(20):2235-2240
Ferrocene‐terminated self‐assembled monolayer (Fc‐SAM) on gold was used as an electron‐transfer mediator in the electrochemical assay of L ‐ascorbic acid 2‐phosphate (AAP). The assay is based on the enzymatic action of alkaline phosphatase (ALP), which triggers the release of vitamin C (L ‐ascorbic acid, AA) from AAP. The latter is easily oxidized on the Fc‐SAM under the diffusion limiting conditions that favors quantitative measurement of the AA concentration on a rotating disk electrode. We demonstrate the utility of the electrochemically active Fc‐SAM to probe the mechanism and to determine the kinetic parameters of an enzymatic reaction. The electrochemical technique was compared to a conventional spectrophotometric method of ALP activity detection using p‐nitrophenylphosphate (p‐NPP) as a substrate. We demonstrate that our new technique is also suitable for the analytical determination of ALP activity. The detection limits for both AAP and ALP were found to be 13 μM and 2 pM, respectively. 相似文献
344.
G Dunér J Iruthayaraj K Daasbjerg SU Pedersen E Thormann A Dėdinaitė 《Journal of colloid and interface science》2012,388(1):225-234
Chitosan (CS) and poly(acrylic acid) (PAA) were crosslinked by an ionic gelation method to form super absorbent polymers (SAPs). CS and PAA form amide bonds between the amino and carboxyl groups. The CS-PAA copolymers were synthetically engineered by varying the feed ratios of the prepolymer units. The copolymer materials possess tunable sorption and mucoadhesive properties with a backbone structure resembling proteinaceous materials. The sorption properties of the copolymers toward methylene blue (MB) in aqueous solution were studied using UV-Vis spectrophotometry at ambient pH and 295 K. The copolymers showed markedly varied interactions with MB, from physisorption- to chemisorption-like behavior, in accordance with their composition, surface area, and pore structure characteristics. The sorption isotherms were evaluated with the Sips model to provide estimates of the sorption properties. The sorbent surface area (271 and 943 m2/g) and the sorption capacity (Qm = 1.03 and 3.59 mmol/g) were estimated for the CS-PAA copolymer/MB systems in aqueous solution. 相似文献
345.
The solid-state 1H NMR on-resonance and off-resonance techniques have been performed to study molecular dynamics and domain sizes in heterogenous nanocomposites based on poly(butylene terephthalate) and nanoparticles C60 modified by n-decylamine (DA) or tetracyanoethylene oxide (TCNEO), respectively. The spin-lattice off-resonance relaxation times in the rotating frame T1ρoff as well as the second moment M2 of the absorption line were analysed as a function of temperature. To determine the size of heterogeneities and characterize the morphology of the nanocomposites, the 1H NMR spin-diffusion experiment designed by Goldman-Shen [1,2] was performed. The results from the measurements allow us to investigate the spin-diffusion phenomenon and relaxation behavior of the new nanocomposites. 相似文献
346.
Giedrė Grincienė Aušra Selskienė Rolandas Verbickas Eugenijus Norkus Rasa Pauliukaite 《Electroanalysis》2009,21(15):1743-1749
Bi films were deposited on glassy carbon electrode from solutions with and without KBr. The morphology of both types of the films was characterized by scanning electron microscopy (SEM), and their electrochemical behavior was studied by square wave (SWV) and cyclic voltammetry (CV). Bi films were also co‐deposited with common analyte‐heavy‐metals in the presence of KBr and these films also were characterized by SEM, SWV and CV in order to understand the formation of the mixed metal films. All films studied had a different morphology. Bromide addition made the Bi films more compact and uniform, whereas Pb catalyzed Bi film deposition. 相似文献
347.
K. Požela A. Šilėnas J. Požela V. Jucienė G. B. Galiev J. S. Vasil’evskii E. A. Klimov 《Applied Physics A: Materials Science & Processing》2012,109(1):233-237
The alternating change of electron mobility values in the modulation doped InAlAs/InGaAs/InAlAs quantum well (QW) dependently on a thickness of the InAs layer inserted in the center of the QW is theoretically predicted and experimentally observed. The electron mobility enhancement by a factor of 1.5–2 takes place when the 4 nm-thick InAs layer is inserted into the 17 nm-width QW. The experimental maximal value of the electron drift velocity at the threshold electric field for intervalley electron scattering achieves (1.8?2)×107 cm/s and does not nearly depend on the thickness of the InAs insert. The high value of maximal drift velocity is conserved at the additional doping of the InAs insert up to electron density of 4×1012 cm?2 in the QW. 相似文献
348.
Isotactic polypropylene (iPP) modified by heterogeneous nucleation and molten state drawing was investigated using the DMTA and NMR methods. The nucleation was realized by specific α and β nucleating agents, 1,3,2,4-bis(3,4-dimetylobenzylideno) sorbitol (Millad 3988, Miliken) leading to the creation of the α phase, and N,N′-dicyklohexylo-2,6-naftaleno dikarboxy amid (NJ100) as the β phase promoter. The processing induced modification was performed by molten state drawing during an extrusion in the range between the die exit and the calibration unit. An increase of the glass transition temperature of iPP was found to be drawing independent for the β-nucleated samples, and dependent in the case of the α-iPP. Changes in the macromolecular mobility, depending on the α/β iPP structure and molten state drawing, was found by NMR lineshape and second moment measurements. 相似文献