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131.
R. Megha S. Kotresh CH. V. V. Ramana S. C. Vijaya Kumari S. Thomas 《Composite Interfaces》2017,24(1):55-68
In the present work, both polypyrrole (PPy) and optimized polypyrrole–magnesium ferrite (PPy-MgFe2O4) hybrid nanocomposite were synthesized separately by simple oxidative chemical polymerization method and then structurally characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The FTIR spectrum of the composite showed the presence of characteristic absorption bands of both PPy and MgFe2O4 in the composite confirming interfacial interaction of PPy with MgFe2O4. That this interaction is not affected by crystalline behaviour of predominant MgFe2O4 particles but that MgFe2O4 has embedded in PPy matrix was confirmed by XRD studies. Agglomerated granular spherical morphology of the composite was confirmed by SEM studies. Decrease in AC conductivity of the composite as compared to PPy due to the formation of interfacial heterojunction barrier between p-type PPy and n-type MgFe2O4 was confirmed experimentally and well supported theoretically by calculating binding energy, hopping distance and density of states at Fermi level of PPy and the composite as per CBH model. 相似文献
132.
A modular total synthesis of cephalosporolides E/F featuring sequential epoxide–alkyne coupling and subsequent highly regioselective gold catalyzed alkynolcycloisomerization of the resulting alkynetetrol to construct the central spiroketal core has been documented. 相似文献
133.
134.
An exact solution is derived by Laplace-transform technique for the problem of the flow of a conducting dusty gas occupying a semi-infinite space in the presence of a transverse magnet field. It is assumed that the flow is independent of the distance parallel to the plate and that the mass concentration of dust is small. Formulas are derived in terms of a constant external impulsive velocity field for the velocity profiles of both the dust and the conducting gas only for values of Hartmann number greater than or equal to unity. For these values of the Hartmann number the skin friction is also obtained. 相似文献
135.
The purpose of this paper is to develop certain geometric results concerning the feasible regions of Semidefinite Programs, called hereSpectrahedra.We first develop a characterization for the faces of spectrahedra. More specifically, given a pointx in a spectrahedron, we derive an expression for the minimal face containingx. Among other things, this is shown to yield characterizations for extreme points and extreme rays of spectrahedra. We then introduce the notion of an algebraic polar of a spectrahedron, and present its relation to the usual geometric polar.Support received under the grants: NSF-STC91-19999 (DIMACS) and Air Force grant F49620-93-1-0041 (RUTCOR).Support from the NSF grant ECS-9111548 is acknowledged. 相似文献
136.
The transfer of a hydrogen from the ortho methoxy group to the acetylenic carbon in 2-methoxyphenylacetylene under electron impact conditions affords the rearranged molecular ion corresponding to 2H-1-benzopyran. Similar processes leading to cyclic products are also noticed in 2-methoxydiphenylacetylenes. The ion structures and the mechanism of fragmentations are established through high-resolution data, collision-induced decomposition, mass-analysed ion kinetic energy spectra, B/E linked scan spectra, D-labelling and chemical substitution. 相似文献
137.
The molecular ions of N,N-dimethylthiobenzamide and its ortho substituted derivatives (substituents CH3, Cl, Br, I) lose a hydrogen atom and/or the ortho substituent. The mechanism of this process has been studied by measurements of the ionization energies, appearance energies of the product ions m/z 164 and the kinetic energy release during this process. The structure of the product ions m/z 164 and relevant reference ions have been investigated by mass analysed ion kinetic energy spectra, B/E linked scan spectra and collision induced decompositions. The results show clearly the formation of two different kinds of product ions m/z 164 depending on the substituent lost. Type a ions are formed by loss of a H atom or the CH3 substituent and correspond to protonated 3,4-benzo-N-methylpyroline-2-thione. The formation of these ions occurs by a hydrogen rearrangement followed by an intramolecular substitution via a 5-membered cyclic intermediate and is associated with a large release of kinetic energy. In contrast, the loss of the halogeno substituents to give type b ions probably occurs via a direct displacement reaction by the sulfur atom of the thioamide group giving rise to Gaussian shaped peaks mass analysed ion kinetic energy spectra. 相似文献
138.
Venkata Ramana Rao P Ramana Rao G 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2002,58(14):3039-3065
The Raman (including FT-Raman) and Fourier transform infrared (FTIR) spectra of 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 2-hydroxybenzaldehyde, 2-hydroxy-3-methoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde, 1,2-dihydroxy-3-methoxybenzene, 2,5-dihydroxytoluene, 2,6-dihydroxytoluene, pentachlorophenol and pentabromophenol were measured. Raman polarisation measurements were made wherever possible. A normal coordinate treatment was carried out for both the in-plane and out-of-plane vibrations of these molecules using a 123-parameter-modified valence force field. An overlay least-squares technique was employed to refine the force constants using 347 frequencies of 10 molecules. The reliability of these force constants was tested by making a zero-order calculation for 10 related molecules. Unambiguous vibrational assignments of all the fundamentals were made using the potential energy distributions and eigenvectors. 相似文献
139.
Expulsion of CO2 from the molecular ions of the 2-(2-carboxyphenyl) derivatives of benzoxazole, benzothiazole and benzimidazole gives rise to the base peaks on electron impact. The proposed mechanism for this fragmentation process, involving the anchimeric assistance of the heteroatom by the initial abstraction of the H˙ from the carboxyl group followed by the expulsion of CO2 from the molecular ions, is supported by the study of the linked scan spectra. 相似文献
140.
D. Ramana A. K. Capoor R. B. Sashidhar Ramesh V. Bhat 《Analytical and bioanalytical chemistry》1995,352(1-2):43-48
Horseradish peroxidase (HRPO) was used as a probe to quantitate aflatoxin B1 by a homogeneous immunoassay. The conjugation of AFB1 to HRPO resulted in 54% loss of enyzme activity. In the presence of AFB1 specific antibodies, the HRPO-AFB1 conjugate showed reversal of its lost enzyme activity by 12%. This positive modulatory effect of antibody on the enzyme activity was used as an analytical tool to quantitate AFB1. The homogeneous assay carried out with free AFB1 and HRPO-AFB1 conjugate in the presence of antibodies indicated poor linearity as compared to the heterogeneous assay. It was observed that the number of HRPO-lysine residues involved in AFB1 conjugation were 6–8. The low level of modulation of enzyme activity by antibody with respect to HRPO-AFB1 conjugate, could possibly be attributed to the limited number of lysine residues in the HRPO molecule and its proximity to the active site of the enzyme. Thus, HRPO was found to be limiting as an enzyme with respect to the homogeneous enzyme immunoassay for AFB1 analysis. The antibodies raised were specific for AFB1, and showed excellent linearity even at high dilution for the detection of AFB1 by ELISA indicating that antibodies per se were not the limiting factor. 相似文献