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491.
Devender Gehlawat R. P. Chauhan R. G. Sonkawade S. K. Chakarvarti 《Applied Physics A: Materials Science & Processing》2012,106(1):157-164
In this paper, we report the effect of gamma ray photons on the electrical conductivity of 100 nm Cu nanowires prepared by
the technique of electrodeposition using track-etched membranes. Different fluences of photons have been used to observe the
effect and in each case of post-irradiation, electrical conductivity is found to increase in a linear manner with increase
in applied potential difference; however the rate of increase of conductivity is different in different cases of radiation
fluence. Grain boundary scattering is of significance for the post-irradiation parabolic nature of the I–V characteristics
(IVC), which are of a linear pattern following Ohm’s law before irradiation. Increase or decrease in the number of charge
carriers during their transport through the nanowires is the result of two competitive processes—specular and diffusive scattering
of charge carriers (electrons) from grain boundaries, which are itself a region of high resistance rather than inter-grain
regions. The results have been discussed in light of the Mayadas and Shatzkes (MS) model with a slight modification for irradiated
nanowires. 相似文献
492.
The precipitation of magnesium, calcium, strontium and barium oxalates and of manganous, ferrous, cobalt, nickel and copper oxalates was studied from equivalent aqueous solutions at 22°C: the initial overall concentrations (C) generally varied from 0.001 to 0.2 M and the saturation ratios (Smox) varied from <10 to >3000. The induction periods before the main growth surge were measured and nucleation rates were determined from final crystal numbers and induction periods. Precipitation occurred through homogenous nucleation: the critical nuclei in supersaturated alkaline-earth metal oxalate solutions were formed by aggregation of 6–8 M++Ox− ion-pairs while the critical nuclei in supersaturated transition metal oxalate solutions were formed by aggregation of 6–8 MOx complexes (to units of 3–4 M++MOx2− ion-pairs). Over the range studied, the nucleation rates then varied with saturation ratios according to the relation, Nucleation rates at any saturation ratio decreased in the order Mg > Sr, Ba > Ca and Fe > Mn > Co, Cu > Ni; that is, generally in the order of increasing M++–Ox− and M++–MOx2− bond strengths and increasing surface energies of the metal oxalate crystals. Induction periods decreased with increasing-concentration and saturation ratio; over The factors t C1 and t S1 depended in turn on the ‘rate constants’ for nucleation and growth during the induction periods and on metal oxalate solubilities. 相似文献
493.
Spectroscopy vs. Electrochemistry: Catalyst Layer Thickness Effects on Operando/In Situ Measurements
Dr. Justus S. Diercks Dr. Juan Herranz Dr. Kathrin Ebner Dr. Nataša Diklić Dr. Maximilian Georgi Piyush Chauhan Dr. Adam H. Clark Dr. Maarten Nachtegaal Prof. Dr. Alexander Eychmüller Prof. Dr. Thomas J. Schmidt 《Angewandte Chemie (International ed. in English)》2023,62(16):e202216633
In recent years, operando/in situ X-ray absorption spectroscopy (XAS) has become an important tool in the electrocatalysis community. However, the high catalyst loadings often required to acquire XA-spectra with a satisfactory signal-to-noise ratio frequently imply the use of thick catalyst layers (CLs) with large ion- and mass-transport limitations. To shed light on the impact of this variable on the spectro-electrochemical results, in this study we investigate Pd-hydride formation in carbon-supported Pd-nanoparticles (Pd/C) and an unsupported Pd-aerogel with similar Pd surface areas but drastically different morphologies and electrode packing densities. Our in situ XAS and rotating disk electrode (RDE) measurements with different loadings unveil that the CL-thickness largely determines the hydride formation trends inferred from spectro-electrochemical experiments, therewith calling for the minimization of the CL-thickness in such experiments and the use of complementary thin-film control measurements. 相似文献
494.
Gadge Sandhya Tamboli Ashif Shinde Manish Fouad Hassan Terashima Chiaki Chauhan Ratna Gosavi Suresh 《Journal of Solid State Electrochemistry》2023,27(8):2005-2015
Journal of Solid State Electrochemistry - The industrial revolution has raised major concern of environmental pollution, due to excess release of hazardous chemical, dyes, etc. into water bodies.... 相似文献
495.
The precipitation magnesium oxalate dihydrate, calcium oxalate monohydrate, strontium oxalate monohydrate and barium oxalate hemihydrate was studied from equivalent solutions of concentrations from 0.001 M to 0.5 M, at pHs from 7 to 6, by optical microscopy and other methods. Crystal growth started after induction periods: the precipitations were heterogeneously nucleated at low supersaturations and homogeneously nucleated at medium to high supersaturations. The crystal form and numbers of the final precipitates depended on the type and number of the nuclei (and crystallites) formed during the induction periods. Crystal numbers at medium to high supersaturation, increased with increasing initial mean metal oxalate concentrations according to the relation, N = N1c; β was 5 for calcium oxalate precipitations and β was 6 for the other metal oxalate precipitations. The N1 values increased in the order MgC2O4 · 2 H2O < BaC2O4 · 1/2 H2O < SrC2O4 · H2O < CaC2O4 · H2O. The final crystal lengths, in this supersaturation range, then decreased (from maximum values) with increasing initial concentrations according to the relation, lfin = l1/CMOxβ, where γ was 1.3 to 1.6. For precipitations from solution of any concentration at any pH, smaller crystals were obtained in the precipitates of the metal oxalate of lower solubility. 相似文献
496.
Gunjan Chauhan Suvarcha Chauhan Surbhi Soni Anand Kumar Devendra Singh Negi Indra Bahadur 《中国化学会会志》2023,70(4):879-893
CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs were synthesized by precipitation method involving three mechanisms: inclusion, occlusion, and adsorption. The synthesized NPs were characterized with the help of UV-Vis spectroscopy, FESEM-EDAX, powder x-ray diffraction, TEM, ESIMS, TG/DSC analysis. The morphology of the CoS@MorphcdtH NPs and CoS@4-MPipzcdtH NPs were hexagonal and rectangular, and the particles were in the range 7–12 nm. UV–visible spectral measurements showed surface plasmon resonance at 320 nm–340 nm with band gap of 3.65 eV–3.86 eV. The catalytically active CoSNPs called were investigated for the reduction of 4-nitrophenol (4-NP) via hydrogenation using sodium borohydride (NaBH4) as a reducing agent. Both the CoS NPs successfully reduced 4-NP to 4- aminophenol (4-AP) in a short time, catalytic performances are almost unchanged for the first five cycles. Herein, we report the preparation and characterizations of efficient active CoS NPs consisting carbodithioic acid framework as a support/capping material, along with catalytic property. 相似文献
497.
The coprecipitations of magnesium (and barium) iron(II) and nickel oxalate dihydrates were studied from excess magnesium and barium oxalate solutions. Nucleation rates were estimated from the induction periods for the coprecipitations. The nucleation rates in excess magnesium oxalate solutions first decreased with increasing excess oxalate anion concentration to minimum values and then increased with increasing magnesium cation concentration. At low to intermediate Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were FeOx (and NiOx); at intermediate Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were probably MgOx FeOx (and MgOx NiOx) mixtures and/or solid solutions of compositions MgαFe1 αOx (and MgαNi1 αOx); at high Mg/Fe(II) (and Mg/Ni) ratios the main nuclei were MgOx. The nucleation rates in excess barium oxalate solutions were similar to those for the precipitation of barium oxalate from supersaturated equivalent solutions. The main nuclei in most systems were BaOx. 相似文献
498.
A. Packter A. Alleem P. Chauhan S. C. Uppaladini 《Crystal Research and Technology》1981,16(12):1419-1424
The precipitation of series of alkaline-earth metal and transition hydroxides, sulphates, chromates and molybdates, hydrogen phosphate carbonates, oxalates and ‘oxinates’ were studied in aqueous solution of low to intermediate supersaturation. Heterogeneous nucleation probably occurred onto micro-crystalline particles of some siliceous mineral (of the trigonal, hexagonal or cubic system), dispersed in the solution. The heterogeneous nucleus numbers for these precipitations then depended on the rates of the heterogeneous nucleation onto these substrates and the rates of the mononuclear growth of nuclei to crystallites (during the induction periods). Generally, Nhet values in polypropylene and glass beakers, at low supersaturation, varied from 104 to 1013 dm−3: the Nhet values then increased slightly with concentration and supersaturation according to the relation Nhet = KNβ, where KN is a function of the metal salt surface energy and an ‘epitaxy’ factor; β = 0.4–0.5. In turn, at any supersaturation, log Nhet = log N + Fσ, where N and F were constants for any precipitation: Nhet values then increased from 104 to 108 times for increase in σ from 50 to 150 mJ m−2. At any supersaturation and surface energy, Nhet values increased in the order monoclinic < orthohombic < tetragonal < trigonal crystals. 相似文献