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941.
942.
V. A. Shaposhnik V. I. Vasil’eva R. B. Ugryumov M. S. Kozhevnikov 《Russian Journal of Electrochemistry》2006,42(5):531-537
A laser interferometry method is proposed for studying the instability of concentration fields during electrodialysis. It is shown that exceeding the limiting diffusion current density first gives rise to alternating oscillations and then to oscillations at the membrane whose ionogenic groups exhibit the lowest catalytic activity towards the water dissociation reaction. Thereafter, the auto-oscillation process extends over the whole solution volume in the compartments, and dissipative chaos is observed with a further increase in the current density. This instability is presumably a consequence of unevenly distributed heat sources, namely, the Joule heat and the heat of dissociation and recombination of water molecules. 相似文献
943.
A series of studies have been made on the circulation structure and the responsible mechanisms related to the Cold Water Mass of the Yellow Sea. From the present model governing the nonlinear thermally driven circulation in shallow seas, some complete analytical solutions of temperature and velocity components have been obtained in this paper by solving the coupled equations of motion and heat conduction. The results demonstrate that the wind-induced stirring and the tidal mixing are all responsible for the termal structure formation of Cold Water Mass. The computed vertical convection (u-w) develops only within a thin layer (called "a current shell" here) in the vicinity of thermocline while the deeper layer remains almost motionless. This current structure represents well the maintenance mechanisms of thermocline or the Cold Watermass during the summer. 相似文献
944.
Methanol oxidation on smooth Pt electrode modified with differ-ent coverage of Ru was studied using cyclic voltammetry and potential step combined with differential electrochemical mass spectroscopy. The current efficiency of formed CO2 was calcu-lated from faraday current and ion current of m/z = 44. The results show that Ru modified Pt electrode with the coverage of ca. 0.3 has the highest catalytic activity for methanol electroox-idation, i. e. faraday current and the current efficiency of CO2 at the low potentials reach to the maximum. In addition, Ru loses its co-catalytic properties at the high potentials. 相似文献
945.
P. Palaska 《Talanta》2007,72(3):1199-1206
The interaction of cyclophosphamide (CP) with calf thymus double-stranded DNA (dsDNA) and thermally denatured single-stranded DNA (ssDNA) immobilized at the carbon paste (CPE) and pencil graphite electrodes (PGE), was studied electrochemically based on oxidation signals of guanine and adenine using differential pulse voltammetry (DPV).As a result of the interaction of CP with DNA, the voltammetric signals of guanine and adenine increased in the case of dsDNA while a slight increase was observed in ssDNA. The effect of experimental parameters such as the interaction time between CP and DNA forms and the concentration of CP, were studied using DPV with CPE and PGE. Additionally, reproducibility and detection limits were determined using both electrodes. A comparison of the analytical performance between CPE and PGE was done. Our results showed that these two different DNA biosensors could be used for the sensitive, rapid and cost effective detection of CP itself as well as of CP-DNA interaction.Furthermore, the interaction of CP with dsDNA and ssDNA was studied in solution and at the electrode surface by means of alternating current voltammetry (ACV) in 0.3 M NaCl and 50 mM sodium phosphate buffer (pH 8.5) supporting electrolyte, using a hanging mercury drop electrode (HMDE) as working electrode.The conclusions of this study were mainly based on tensammetric peaks I (at −1.183 V) and II (−1.419 V) of DNA. This study involved the interaction of CP with surface-confined and solution phase DNA where experimental parameters, such as the concentration of CP and the interaction time, were studied. By increasing the concentration of CP, an increase of peak II was observed in both ds and ssDNA, while an increase of peak I was observed only in the case of dsDNA. An overall conclusion of the study using HMDE was that the interaction of CP with surface-confined DNA significantly differed from that with solution phase DNA. The increase of peaks I and II was lower in the case of interaction of CP with surface-confined DNA, probably due to steric positioning of DNA at the electrode surface. 相似文献
946.
《Electroanalysis》2004,16(16):1351-1358
In a recent paper [9] we reported the manufacturing and performance of miniaturized reference electrodes (MREs) with low sensitivity to chloride ions and pH. Here, we demonstrate the wide range applicability of a MRE based on an Ag/Ag2S internal reference element (IRE), imbedded in a photopolymerized hydrogel of improved composition, which contains the supporting electrolyte. Exchange current density, temperature coefficient, impedance value, and the voltammetric and potentiometric use of the Ag/Ag2S‐based MRE are discussed relative to the previously reported Ag/AgSCN, Ag/Ag3PO4, and Ag/AgCl‐based MREs. No special or extensive conditioning is required when moving these MREs from aqueous supporting electrolyte to an organic solution or from one organic medium to another, and the equilibration time in a new medium is very rapid (<6 min). The new Ag/Ag2S MRE has a highly stable potential in various media, including aqueous solutions (salt buffers and 20 wt.% H2SO4), biological samples (bovine serum albumin), mixed aqueous‐organic, and organic supporting electrolytes (methanol, ethanol, acetonitrile, propylene carbonate, methylene chloride, and DMSO). This is particularly advantageous when in the course of the electrochemical analysis an organic solution is being added to an aqueous supporting electrolyte. Such MREs are suitable for analyses of μL sample volumes and for use in protein‐containing media. 相似文献
947.
《Electroanalysis》2005,17(14):1269-1278
Oxidation/reduction of polypyrrole films coupled with ion exchange on the polymer/solution interface can be utilized for amperometric sensing of electroinactive ions. Anion or cation exchanging films (polypyrrole doped by chloride or poly(4‐styrenesulfonate) ions, respectively) can be used to determine common anions (as Cl?, NO , SO etc) or cations (K+, Na+, Li+, Ca2+, Mg2+) under conditions of alternating current (AC) amperometry in the range 10?4–1 M. A sensitivity can be tuned by choosing appropriate electrode potential, corresponding to polypyrrole oxidation (anion‐exchanging films) or reduction (cation‐exchangers). Electrochemical impedance spectroscopy and AC‐voltammetry studies have shown that applied frequency and potential could also affect the observed dependence of the signal (admittance or AC‐current) on ion concentration. For high frequency the sensitivity is higher but selectivity lower, due to influence of solution conductivity on the response. For low frequencies the sensitivity is lower; however, a selectivity increase was observed due to diverse mobility of ions in the polymer film. Selectivity of AC‐amperometric responses was studied both in separate and mixed solutions. 相似文献
948.
The operation of ice-going vessels depends on the condition of the hull surface. Corrosion increases the roughness of ship hull, which increases drag and fuel consumption. The hull surface smoothness is maintained by using coatings and cathodic protection. The cold brackish water is different from ocean water as it has lower salt content, lower conductivity, and higher concentration of dissolved oxygen. These factors mean that the design of the cathodic protection system for ship hulls requires different design values, such as protection current density and protected length, than those given in cathodic protection standards. In this paper, we have estimated the protection current density with polarization curves and the protected length by using Wagner number and dimension and conductivity scaling. In brackish water the protection current density was two times that in ocean water. The protected length in brackish water varied between 10 and 15% of that in ocean water. In poorly conducting brackish water, the current capacity of a cathodic protection system is used mostly for overcoming the solution resistance, not for delivering protection current. 相似文献
949.
To enhance film conformality together with electrical property suitable for dynamic random access memory (DRAM) capacitor
dielectric, the effects of oxidant and post heat treatment were investigated on aluminum and titanium oxide (Al2O3–TiO2) bilayer (ATO) thin film formed by atomic layer deposition method. For the conformal deposition of Al2O3 thin film, the O3 oxidant required a higher deposition temperature, more than 450 °C, while H2O or combined oxygen sources (H2O+O3) needed a wide range of deposition temperatures ranging from 250 to 450 °C. Conformal deposition of the TiO2 thin film was achieved at around 325 °C regardless of the oxidants. The charge storage capacitance, measured from the ATO
bilayer (4 nm Al2O3 and 2 nm TiO2) deposited at 450 °C for Al2O3 and 325 °C for TiO2 with O3 oxidant on the phosphine-doped poly silicon trench, showed about 15% higher value than that of 5 nm Al2O3 single layer thin film without any increase of leakage current. To maintain the improved electrical property of the ATO bilayer
for DRAM application, such as enhanced charge capacitance without increase of leakage current, upper electrode materials and
post heat treatments after electrode formation must be selected carefully.
Dedicated to Professor Su-Il Pyun on the occasion of his 65th birthday. 相似文献
950.
V. D. Ivanov 《Russian Journal of Electrochemistry》2003,39(10):1042-1048
Methods of analysis of voltammograms for redox systems adsorbed on an electrode are analyzed. The methods allow for the interaction between species in the adsorption layer. An approximate equation of the adsorption peak, suitable for performing numerical calculations on a computer using standard programs, is proposed. The accuracy of the equation and conditions of its application are discussed. 相似文献