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31.
Two classes of electrovac solutions are obtained in oblate spheroidal coordinates, which are the electromagnetic analogs of Zipoy's monopole and dipole solutions. The asymptotic behavior of the solutions is studied to gain some insight into the nature of the source of the gravitational and electromagnetic fields. A similar stationary solution of the pure gravitational field is found to belong to Papapetrou's class. 相似文献
32.
[60]fullerene is known to aggregate in water and all experimental and theoretical evidences support that the aggregates contain (C60)13 units. No chemical kinetic study of the effect of solvent polarity on the aggregation of C60 has so far been reported. Here we show by simple kinetic study of the aggregation process and by scanning electron microscopy (SEM) that when methanol is added to a solution of [60]fullerene in CCl4, spontaneous aggregation starts immediately and the aggregation numbers (n) found to be dependent on the CCl4:CH3OH ratio (v/v) of the medium. One particular ratio of the two liquids gives uniformly sized (C60)13 clusters for about 10 min. The values of n correspond to the minima of the previously reported energy calculations and in the present work, they have been shown to be a natural consequence of stacking of cuboctahedra made up of C60 molecules. A Young diagram-like method has been developed for counting the number of C60 molecules in these cuboctahedral stacks and the numbers obtained from this model and also from the present chemical kinetic and SEM studies agree very well with the "magic numbers" obtained by earlier mass spectrometric studies. 相似文献
33.
Banerji B Conejo-Garcia A McNeill LA McDonough MA Buck MR Hewitson KS Oldham NJ Schofield CJ 《Chemical communications (Cambridge, England)》2005,(43):5438-5440
Cyclic beta-oxocarboxylic acids inhibit factor inhibiting hypoxia-inducible factor via ligation to the active site iron. 相似文献
34.
Roy DK Saha A Mukherjee AK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,63(3):694-699
Cloxacillin sodium has been shown to form a charge transfer complex of 2:1 stoichiometry with riboflavin (Vitamin B(2)) in aqueous ethanol medium. The enthalpy and entropy of formation of this complex have been determined by estimating the formation constant spectrophotometrically at five different temperatures in pure water medium. Pronounced effect of dielectric constant of the medium on the magnitude of K has been observed by determining K in aqueous ethanol mixtures of varying composition. This has been rationalized in terms of ionic dissociation of the cloxacillin sodium (D(-)Na(+)), hydrolysis of the anion D(-) and complexation of the free acid, DH with riboflavin. 相似文献
35.
Vikash Kumar Viraj G. Naik Avijit Das Sourayan Basu Bal Malabika Biswas Nupur Kumar Anasuya Ganguly Amrita Chatterjee Mainak Banerjee 《Tetrahedron》2019,75(27):3722-3732
Available online Development of water soluble AIE-active “light-up” bioprobes for the detection of biomacromolecules has drawn huge research interests in recent past. In this study, a series of ethylene glycol modified water soluble tetrameric tetraphenylethylene amphiphiles with pyridinium polar heads (TPE-xEG-Py, x = 3, 4, 6 or 1a-c) have been synthesized by varying the ethylene glycol spacer. Their unique structure allows them to form vesicles and other nanoaggregates in aqueous solutions. These amphiphiles were successfully utilized for fluorimetric detection and quantitation of BSA and DNA based on the electrostatic interactions to trigger AIE-emission from the TPE moiety. The electrostatic interaction was also proved very effective in wash-free imaging of both Gram-negative (E. coli) and Gram-positive (S. aureus) bacteria with up to 92 folds increase in fluorescence response within bacterial concentration 0–12 × 108 CFU mL?1. The strategy is advantageous due to cost-effective and easy synthesis, high water solubility, and fast response. 相似文献
36.
Nicolaou KC Sun YP Guduru R Banerji B Chen DY 《Journal of the American Chemical Society》2008,130(11):3633-3644
Palmerolide A is a recently disclosed marine natural product possessing striking biological properties, including potent and selective activity against the melanoma cancer cell line UACC-62. The total syntheses of five palmerolide A stereoisomers, including the originally proposed (1) and the revised [ent-(19-epi-20-epi-1)] structures, have been accomplished. The highly convergent and flexible strategy developed for these syntheses involved the construction of key building blocks 2, 19-epi-2, 20-epi-2, ent-2, 3, ent-3, 4, and ent-4, and their assembly and elaboration to the target compounds. For the union of the building blocks, the Stille coupling reaction, Yamaguchi esterification, Horner-Wadsworth-Emmons olefination, and ring-closing metathesis reaction were employed, the latter being crucial for the stereoselective formation of the macrocycle of the palmerolide structure. The Horner-Wadsworth-Emmons olefination and the Yamaguchi lactonization were also investigated and found successful as a means to construct the palmerolide macrocycle. The syntheses were completed by attachment of the enamide moiety through a copper-catalyzed coupling process. 相似文献
37.
Nonendocytotic transport is believed to play a role in the transmigration of particles less than 100 nm within biological systems. Determining the fundamental mechanism of this transport across cell membranes is essential if nanotechnology is to be utilized in general medical practice and may lead to methods of treating the deleterious internalization of ambient, possibly pollutant, nanoparticles. In order to gain a broader understanding of nonendocytotic transmembrane transport, it becomes essential to devise a method which allows the isolation of fundamental modes of transport such as passive Brownian diffusion through a membrane, as opposed to effusion-like transport of particles through transmembrane channels. The passive Brownian diffusion contribution was investigated using gold nanoparticles and mimetic biomembranes. Specifically, gold nanoparticle dispersions consisting of 7, 10, and 15 nm diameter particles were captured in giant unilamelar vesicles composed of phosphatidylcholine, phosphatidic acid, and cholesterol. Nonendocytotic transmembrane transport was modeled as the time derivative of the appearance of nanoparticles in the phosphate buffer outside the vesicles at 37 degrees C. The results show the transport rate to be zero; hence, a simple diffusive process of transmembrane transport is not supported. 相似文献
38.
Surface modification of magnetic nanoparticle via Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition 总被引:1,自引:0,他引:1
The Cu(I)-catalyzed alkyne-azide [2 + 3] cycloaddition has been demonstrated to be an effective and orthogonal conjugation reaction to covalently immobilize biomolecules on magnetic nanoparticles (MNPs). The azido group on the MNP surface provides better conjugation efficiency with alkynated molecules. Moreover, the C-terminal alkynated protein was site-specifically immobilized on MNP. The protein binding activity presented by site-specific immobilization is higher than that by random amide bond formation. 相似文献
39.
The oxidation of thirty‐six monosubstituted benzaldehydes by hexa‐methylenetetramine‐bromine (HABR), in aqueous acetic acid solution, leads to the formation of the corresponding benzoic acids. The reaction is first order with respect to HABR. Michaelis‐Menten–type kinetics were observed with respect to aldehyde. The reaction failed to induce the polymerization of acrylonitrile. There is no effect of hexamethylenetetramine on the reaction rate. The oxidation of [2H]benzaldehyde (PhCDO) indicated the presence of a substantial kinetic isotope effect. The effect of solvent composition indicated that the reaction rate increases with an increase in the polarity of the solvent. The rates of oxidation of meta‐ and para‐substituted benzaldehydes showed excellent correlations in terms of Charton's triparametric LDR equation, whereas the oxidation of ortho‐substituted benzaldehydes correlated well with tetraparametric LDRS equation. The oxidation of para‐substituted benzaldehydes is more susceptible to the delocalization effect but the oxidation of ortho‐ and meta‐substituted compounds displayed a greater dependence on the field effect. The positive value of γ suggests the presence of an electron‐deficient reaction center in the rate‐determining step. The reaction is subjected to steric acceleration when ortho‐substituents are present. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 615–622, 2000 相似文献
40.
The oxidation of lower oxyacids of phosphorus by hexamethylenetetramine bromine (HABR) in glacial acetic acid resulted in the formation of corresponding oxyacids with phosphorus in a higher oxidation state. The reaction exhibited 2:1 stoichiometry. The reaction is first order with respect to HABR. Michaelis–Menten‐type kinetics were observed with respect to the acids. The formation constant of the phenylphosphinic acid–HABR complex also has been determined spectrophotometrically. The thermodynamic parameters for the complex formation and the activation parameters for their decomposition were calculated. The reaction showed the presence of a substantial kinetic isotope effect. It is proposed that the HABR itself is the reactive oxidizing species. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant. A suitable mechanism has been proposed. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 165–170, 2000 相似文献