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201.
M. Pramanik S. K. Srivastava B. K. Samantaray A. K. Bhowmick 《Journal of Polymer Science.Polymer Physics》2002,40(18):2065-2072
We synthesized organosoluble, thermoplastic elastomer/clay nanocomposites by making a jelly like solution of ethylene vinyl acetate containing 28% vinyl acetate (EVA‐28) and blending it with organomodified montmorillonite. Sodium montmorillonite (Na+‐MMT) was made organophilic by the intercalation of dodecyl ammonium ions. X‐ray diffraction patterns of Na+‐MMT and its corresponding organomodified dodecyl ammonium ion intercalated montmorillonite (12Me‐MMT) showed an increase in the interlayer spacing from 11.94 to 15.78 Å. However, X‐ray diffraction patterns of the thermoplastic elastomer and its hybrids with organomodified clay contents up to 6 wt % exhibited the disappearance of basal reflection peaks within an angle range of 3–10°, supporting the formation of a delaminated configuration. A hybrid containing 8 wt % 12Me‐MMT revealed a small hump within an angle range of 5–6° because of the aggregation of silicate layers in the EVA‐28 matrix. A transmission electron microscopy image of the same hybrid showed 3–5‐nm 12Me‐MMT particles dispersed in the thermoplastic elastomer matrix; that is, it led to the formation of nanocomposites or molecular‐level composites with a delaminated configuration. The formation of nanocomposites was reflected through the unexpected improvement of thermal and mechanical properties; for example, the tensile strength of a nanocomposite containing only 4 wt % organophilic clay was doubled in comparison with that of pure EVA‐28, and the thermal stability of the same nanocomposite was higher by about 34 °C. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 2065–2072, 2002 相似文献
202.
Dinuclear (V(IV)V(V)) oxophenoxovanadates of general formula [V2O3L] have been synthesized in excellent yields by reacting bis(acetylacetonato)oxovanadium(IV) with H3L in a 2:1 ratio in acetone under an N2 atmosphere. Here L3- is the deprotonated form of 2,6-bis[{{(2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L1), 2,6-bis[{{(5-methyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L2), 2,6-bis[{{(5-tert-butyl-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L3), 2,6-bis[{{(5-chloro-2-hydroxybenzyl)(N',N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol(H3L4), 2,6-bis[{{(5-bromo-2-hydroxybenzyl)(N'N'-(dimethylamino)ethyl)}amino}methyl]-4-methylphenol (H3L5), or 2,6-bis[{{(5-methoxy-2-hydroxybenzyl)(N'N'-(dimethylamino)ethyl)}methyl]-4-methylphenol (H3L6). In [V2O3L1], both the metal atoms have distorted octahedral geometry. The relative disposition of two terminal V=O groups in the complex is essentially cis. The O=V...V=O torsion angle is 24.6(2) degrees . The V-O(oxo)-V and V-O(phenoxo)-V angles are 117.5(4) and 93.4(3) degrees , respectively. The V...V bond distance is 3.173(5) A. X-ray crystallography, IR, UV-vis, and 1H and 51V NMR measurements show that the mixed-valence complexes contain two indistinguishable vanadium atoms (type III). The thermal ellipsoids of O2, O4, C10, C14, and C15 also suggests a type III complex in the solid state. EPR spectra of solid complexes at 77 K display a single line indicating the localization of the odd electron (3d(xy)1). Valence localization at 77 K is also consistent with the 51V hyperfine structure of the axial EPR spectra (3d(xy)1 ground state) of the complexes in frozen (77 K) dichloromethane solution: S = 1/2, g(parallel) approximately 1.94, g(perpendicular) approximately 1.98, A(parallel) approximately 166 x 10(-4) cm(-1), and A(perpendicular) approximately 68 x 10(-4) cm(-1). In contrast isotropic room-temperature solution spectra of the family have 15 hyperfine lines (g(iso) approximately 1.974 and A(iso) approximately 50 x 10(-4) cm(-1)) revealing that the unpaired electron is delocalized between the metal centers. Crystal data for the [V2O3L1].CH2Cl2 complex are as follows: chemical formula, C32H43O6N4Cl2V2; crystal system, monoclinic; space group, C2/c; a = 18.461(4), b = 17.230(3), c = 13.700(3) A; beta = 117.88(3) degrees ; Z = 8. 相似文献
203.
Anup Pramanik 《Journal of Molecular Spectroscopy》2007,244(1):13-23
Electronic structure and spectroscopic properties of the low-lying electronic states of the SiC radical have been determined from the ab initio based configuration interaction calculations. Potential energy curves of 32 Λ-S states of singlet, triplet, and quintet spin multiplicities have been constructed. Spectroscopic constants (re, Te, and ωe) of 23 states within 6 eV are reported and compared with the existing data. The dipole moments (μe) of most of these states at their respective equilibrium bond lengths have been computed. Effects of the spin-orbit coupling on the spectroscopic properties of SiC have been studied. The E3Π state is found to be an important one which has not been studied before. A transition of the type E3Π-X3Π is predicted to take place in the range 25 000-26 000 cm−1. The partial radiative lifetimes for several electric dipole allowed transitions such as A3Σ+-X3Π, B3Σ+-X3Π, C3Π-X3Π, D3Δ-X3Π, E3Π-X3Π etc. have been reported. 相似文献
204.
We report experimental observations of transverse shear waves in a three-dimensional dusty plasma that is in the strongly coupled fluid regime. These spontaneous oscillations occur when the ambient neutral pressure is reduced below a threshold value and the measured dispersion characteristics of these waves are found to be in good agreement with predictions of a viscoelastic theory of dusty plasmas. 相似文献
205.
From stopped-flow spectrophotometric studies on the kinetics of dissociation of [M(trien)]2+ (M=CuII, NiII) to M
aq
2+
and trien H
4
4+
in aqueous acid medium, it has been established that the reaction occurs in a complex manner conforming to the relation
相似文献
206.
Birendra N. Pramanik Yao Hain IngAjay K. Bose Li-Kang ZhangYan-Hui Liu Subhendu N. GangulyPeter Bartner 《Tetrahedron letters》2003,44(12):2565-2568
The application of microwave assisted modification of the Akabori hydrazinolysis reaction has been found to cleave cyclic oligopeptides in a selective fashion to produce mainly the hydrazide of a specific linear peptide. This ring cleavage requires a few minutes of reaction in a domestic microwave oven. The linear peptide hydrazide can be analyzed by ESI-MS/MS, FAB-MS, and FAB-MS/MS methods for the determination of the amino acid sequence. 相似文献
207.
Chandrani Mukherjee 《Tetrahedron》2006,62(26):6150-6154
To explore the synthetic potential of nitrilase ZmNIT2 from maize, the substrate specificity of this nitrilase was studied with a diverse collection of nitriles. The nitrilase ZmNIT2 showed high activity for all the tested nitriles except benzonitrile, producing both acids and amides. For the hydrolysis of aliphatic, aromatic nitriles, phenylacetonitrile derivatives and dinitriles, carboxylic acids were the major products. Unexpectedly, amides were found to be the major products in nitrilase ZmNIT2-catalyzed hydrolysis of β-hydroxy nitriles. The hydrogen bonding between the hydroxyl group and nitrogen in the enzyme-substrate complex intermediates that disfavors the loss of ammonia and formation of acyl-enzyme intermediate, which was further hydrolyzed to acid, was proposed to be responsible for the unprecedented β-hydroxy functionality assisted high yield of amide formation. 相似文献
208.
Intense pseudomolecular ions were observed for underivatized, multifunctional compounds of low volatilty (e.g., bile acid conjugates, alkaloids, antibiotics) by employing the direct probe technique of NCI MS; especially effective was the use of CF2CL2 as the reagent gas for producing chloride ion adduct negative ions. 相似文献
209.
Sujan Chatterjee Paltu Banerjee Smritimoy Pramanik Attreyee Mukherjee Kumar K. Mahalanabis Subhash Chandra Bhattacharya 《Chemical physics letters》2007,440(4-6):313-320
S0 → S1 and S0 → S2 electronic transitions have been observed in UV–Visible absorption spectroscopy of 3-pyrazolyl-2-pyrazoline (PZ) in different homogeneous solvents. Radiative emissions and relaxation processes from S1 and S2 states of PZ have been resolved in water, ethylene glycol and glycerol whereas in polar aprotic and protic solvents the radiative transitions have been observed from S1 state. The S2–S1 electronic energy spacing has been calculated from the absorption maxima of the S0 → S2 transitions and fluorescence maxima of the S1 → S0 transitions. Solute–solvent interactions have been established to rationalize the photophysical modification of PZ in H-bonding solvents. 相似文献
210.
We investigated the temperature dependence of the splay elastic constant (K11) and rotational viscosity (γ1) of a binary liquid crystal system comprising 5-trans-n-butyl-2-(4-isothiocyanatophenyl)-1,3-dioxane (4DBT) and 4-cyano-4′-n-undecyloxy-biphenyl (11OCB), exhibiting induced nematic phase. Both the splay elastic constant and rotational viscosity increased following lowering of the temperature. In the vicinity of smectic A-nematic (SmA-N) transition, both the relaxation time and rotational viscosity exhibited a strong pretransitional behaviour. The critical exponent (ν) presented here led to valuable qualitative information about the pre-transitional behaviour of the rotational viscosity data near the SmA-N phase transition. The extracted ν values ranging between 0.336 and 0.352 are in fair agreement with those predicted in the de Gennes model as compared to that by the mean-field model. 相似文献
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