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121.
122.
Dry coating experiments were performed by using the Hybridizer (Nara). Large host silica gel (SG) particles (d50 = 55 μm) were coated with fine invited particles of magnesium stearate (MS, d50 = 4.6 μm) for different contents of MS in the mixture. The real MS mass fraction wI obtained after mechanical treatment has been determined thanks to calibration from TGA measurements. The surface structure and morphology of MS coatings were observed using environmental scanning electron microscopy (ESEM) and atomic force microscopy (AFM) [Y. Ouabbas, A. Chamayou, L. Galet, M. Baron, J. Dodds, A.M. Danna, G. Thomas, B. Guilhot, P. Grosseau, Modification of powders properties by dry coating: some examples of process and products characteristics, Proceedings of CHISA2008, Prague, August 2008, submitted for publication; L. Galet, Y. Ouabbas, A.M. Danna, G. Thomas, P. Grosseau, M. Baron, A. Chamayou, Surface morphology analysis and AFM study of silica gel particles after mechanical dry coating with magnesium stearate, Proceedings of PSA2008, UK, September 2008, submitted for publication].AFM has been also used to measure the adhesion forces between particles. Interaction forces between the material attached to the cantilever (magnesium stearate MS) and the surface of the composite material (silica gel SG or magnesium stearate MS) have been determined at different surface locations. For different compositions wI of the mixture MS-SG, the numeric distribution and the mean value f of the forces fH obtained for MS-SG interactions or fI for MS-MS interactions have been established and the experimental curve showing the evolution of f versus wI has been derived.Models of ordered structures have been developed, implying morphological hypotheses concerning large spherical or cylindrical host particles H and small invited spherical I. Different types of distribution of I materials onto the surface of H have been considered: for examples a discrete monolayer - or multilayers - of monosized particles I on the H surface. The coordinence of MS particles around SG particles has been estimated to calculate the free SG surface fraction through different modelling and to obtain the mean force f versus composition wI. The theoretical force values have been compared to experimental ones. The deviations have been discussed in terms of guest particle distributions on the surface of the large host particles and morphological hypotheses. 相似文献
123.
The effect of enzymes: lipase from Candida cylindracea (LCc), phospholipase A2 from hog pancreas (PLA2) and phospholipase C from Bacillus cereus (PLC) to modulate wetting properties of solid supported phospholipid bilayers was studied via advancing and receding contact angle measurements of water, formamide and diiodomethane, and calculation of the surface free energy and its components from van Oss et al. (LWAB) and contact angle hysteresis (CAH) approaches. Simultaneously, topography of the studied layers was determined by Atomic Force Microscopy (AFM). The investigated lipid bilayers were transferred on mica plates from subphase of pure water by means of Langmuir-Blodgett and Langmuir-Schaefer techniques. The investigated phospolipid layers were: saturated DPPC (1,2-dipalmitoyl-sn-glycero-3-phosphocholine), unsaturated DOPC (1,2-dioleoyl-sn-glycero-3-phosphocholine), and their mixture DPPC/DOPC. The obtained results revealed that the lipid membrane degradation by the enzymes caused increase in its surface free energy due to the amphiphilic hydrolysis products, which may accumulate in the lipid bilayer. In result activity of the enzymes may increase and then break down the bilayer structure takes place. It is likely that after dissolution of the hydrolysis reaction products in the bulk phase, patches of bare mica surface are accessible, which contribute to the apparent surface free energy changes. Comparison of AFM images and the free energy changes of the layers gives better insight into changes of their properties. The observed gradual increase in the layer surface free energy allows controlling of the hydrolysis process to obtain the surfaces of defined properties. 相似文献
124.
Concentration dependent morphology of 3‐armed poly(ethylene glycol)‐b‐poly(ε‐caprolactone) copolymer aggregates in aqueous system was investigated by atomic force microscopy (AFM). The AFM results show that, at a low concentration, 4 × 10?5 g/mL, spherical micelles occur, and unmicellized molecules are not distributed homogeneously in the copolymer aqueous solution. Unequal outspread clusters composed of wormlike aggregates are formed at a moderate copolymer concentration, 4 × 10?4 g/mL, those wormlike aggregates are orderly packed in the clusters. At a high concentration of 0.05 g/mL, the copolymer aqueous system is indeed a gel at room temperature, outspread clusters of wormlike aggregates join together to forma network structure. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1412–1418, 2008 相似文献
125.
The exact frequency shift of an AFM non-uniform probe with an elastically restrained root, subjected to van der Waals force, is derived. The original distributed system is considered and then its exact fundamental solutions and the general frequency equation are derived. Results are compared with those by the force gradient method and the perturbation method. The effects of several parameters on the sensitivity of measurement are investigated. Results show that the interpretation of frequency shift by using the force gradient method is unsatisfactory. The smaller the amplitude of oscillation and the tip–surface distance are, the larger the frequency shift. The design of a taper beam is recommended for increasing the sensitivity of measurement. 相似文献
126.
Elisabeth Holder Veronica Marin Alexander Alexeev Ulrich S. Schubert 《Journal of polymer science. Part A, Polymer chemistry》2005,43(13):2765-2776
A set of novel greenish‐yellow‐, yellow‐, and orange‐light‐emitting polymeric iridium(III) complexes were synthesized with the bridge‐splitting method. The respective dimeric precursor complexes, [Ir(ppy)2‐μ‐Cl]2 (ppy = 2‐phenylpyridine) and [Ir(ppy? CHO)2‐μ‐Cl]2 [ppy? CHO = 4‐(2‐pyridyl)benzaldehyde], were coordinated to 2,2′‐bipyridine carrying poly(ε‐caprolactone) tails. The resulting emissive polymers were characterized with one‐dimensional (1H) and two‐dimensional (1H? 1H correlation spectroscopy) nuclear magnetic resonance and infrared spectroscopy, gel permeation chromatography, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry, and the successful coordination of the iridium(III) centers to the 2,2′‐bipyridine macroligand was revealed. The thermal behavior was studied with differential scanning calorimetry and correlated with atomic force microscopy. Furthermore, the quantitative coordination was verified by both the photophysical and electrochemical properties of the mononuclear iridium(III) compounds. The photoluminescence spectra showed strong emissions at 535 and 570 nm. The color shifts depended on the substituents of the cyclometallating ligands. Cyclic voltammetry gave oxidation potentials of 1.23 V and 1.46 V. Upon the excitation of the films at 365 nm, yellow light was observed, and this could allow potential applications in light‐emitting devices. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2765–2776, 2005 相似文献
127.
Ga‐Young Lee Jin‐Hyang Kim Hyo Jin No Ju‐Yeon Lee Bum Ku Rhee Hee‐dok Choi 《Journal of polymer science. Part A, Polymer chemistry》2009,47(7):1911-1919
1‐{3,4‐Di‐(2‐hydroxyethoxy)phenyl}‐2‐(2‐thiophenyl)ethene (5) was prepared and condensed with terephthaloyl chloride to yield polyester (6). Polymer 6 was reacted with tetracyanoethylene to give a new Y‐type polyester (7) containing 1‐(3,4‐dioxyethoxy)phenyl‐2‐{5‐(2,2,3‐tricyanovinyl)‐2‐thiophenyl)}ethenyl groups as NLO‐chromophores, which are components of the polymer backbones. Polyester 7 is soluble in common organic solvents such as N,N‐dimethylformamide and acetone. Polymer 7 showed a thermal stability up to 300 °C in thermogravimetric analysis with glass transition temperature (Tg) obtained from differential scanning calorimetry near 126 °C. The second harmonic generation (SHG) coefficient (d33) of poled polymer film at the 1560 nm fundamental wavelength was around 6.57 × 10?9 esu. The dipole alignment exhibited high thermal stability up to the Tg, and there was no SHG decay below 125 °C due to the partial main‐chain character of polymer structure, which is acceptable for NLO device applications. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1911–1919, 2009 相似文献
128.
A new interface reconstruction method in 3D is presented. The method involves a conservative level‐contour reconstruction coupled to a cubic‐Bézier interpolation. The use of the proposed piecewise linear interface calculation (PLIC) reconstruction scheme coupled to a multidimensional time integration provides solutions of second‐order spatial and temporal accuracy. The accuracy and efficiency of the proposed reconstruction algorithm are demonstrated through several tests, whose results are compared with those obtained with other recently proposed methods. An overall improvement in accuracy with respect to other recent methods has been achieved, along with a substantial reduction in the central processing unit time required. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
129.
A. Tsargorodskaya S.V. Lishchuk A. Nabok 《Colloids and surfaces. A, Physicochemical and engineering aspects》2008,324(1-3):117-121
The model of binding of micelles of nonylphenol molecules to respective antibodies immobilized on the solid surface is proposed. The actual dimensions of micelles obtained from AFM measurements were used in modelling and allowed to predict the shape of the micelle. An account of non-spherical shape of micelles and their simultaneous binding to several antibodies allows estimation of the micelle binding energy. 相似文献
130.
Novel fluoroalkyl end‐capped vinyltrimethoxysilane oligomer/hydroxyapatite (HAp) nanocomposites were prepared by the reaction of calcium nitrate tetrahydrate and phosphoric acid in the presence of the corresponding oligomer. These fluorinated oligomer/HAp composites thus obtained are nanometer size‐controlled fine particles (83–173 nm), and were found to exhibit good dispersibility in methanol, ethanol, and isopropyl alcohol. These fluorinated HAp nanocomposites were applied to the surface modification of glass and poly(methyl methacrylate) (PMMA) to exhibit good hydro‐ and oleophobic characteristics imparted by fluorine on their surface. In addition, the surface structural changes of the modified polyethylene terephtalate and PMMA films treated with these fluorinated nanocomposites before and after soaking in a simulated body fluid (SBF) were analyzed by using SEM, XRD, and EDX to observe the formation of spherical HAp deposits on the surface. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献