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21.
Simple alkali metal cation-TCNQ anion radical salts are classified in two groups from the differences in their physicochemical properties and crystal structures. Li-, Na-, K-, and Rb(I)-TCNQ are comprised in Group A. Li-TCNQ exhibits distinct behavior from other salts in Group A. Rb(II)- and Cs-TCNQ belong to Group B. Phase transitions, electrical conductivities, and absorption spectra in these simple salts are closely related to their crystal structures. 相似文献
22.
4,4'-Dihydroxytriphenylmethanes were synthesized using Br?nsted acid or Lewis acid in yields of 24-86% as target compounds for developing antiviral agents. Most of the 4,4'-dihydroxytriphenylmethanes showed significant activity against herpes simplex virus type 1 (anti-HSV-1 activity) in a plaque reduction assay. Higher cytotoxicity was observed generally in halogenated 4,4'-dihydroxytriphenylmethanes (2a-d) than in non-halogenated derivatives. The non-halogenated derivative, 4,4',4"-trihydroxy-3"-methoxytriphenylmethane (3), showed remarkable antiviral activity with an EC(50) value of 1.8 microg/ml. 相似文献
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Takeshi Kakibe Nobuko Yoshimoto Minato Egashira Masayuki Morita 《Electrochemistry communications》2010,12(11):1630-1633
A series of imidazolium cation-based ionic liquids (ILs) have been synthesized and examined as ionic solvents for rechargeable magnesium batteries. The electrolyte solutions consist of these ILs dissolving methylmagnesium bromide with tetrahydrofuran (MeMgBr/THF). The chemical structure of imidazolium cation much influenced the ionic conductivity and the electrochemical window of the system. A reversible process of cathodic deposition and anodic dissolution of magnesium has been successfully achieved at room temperature. The highest value of anodic peak current for magnesium dissolution was obtained in an optimized-structure IL with allyl and methoxyethyl groups as the substituents. 相似文献
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26.
Aloe plants have been widely documented in artists’ treatises dating from the sixteenth to the nineteenth century as a source
of colorant to achieve lustrous golden glazes on tin- and silver-foiled objects and warm-toned finishes on musical instruments,
such as violins. Aloe extracts contain characteristic anthraquinone and phenolic components which impart a distinctive orange
tone and fluorescence to mixtures containing them. Because of the low concentration of colorant in the coatings and its probable
degradation by high temperature during manufacture, the identification of aloe in heated oil–resin mixtures represents an
analytical challenge. For this reason, the possible presence of aloe in glazes and coatings has been largely overlooked. This
paper describes various analytical approaches to the identification of aloe in historic samples, from comparison with results
obtained from reference standards and mock-up samples. Complementary analytical techniques including thermally assisted hydrolysis
and methylation–gas chromatography–mass spectrometry, high-performance liquid chromatography, laser desorption–mass spectrometry,
matrix-assisted laser desorption-ionization-mass spectrometry and surface-enhanced Raman scattering were used. Different chemical
markers were identified by the individual methods and the advantages and limitations of each technique for the identification
of aloe in oil–resin varnishes are discussed. 相似文献
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29.
Nobuko I. Wakayama 《Journal of luminescence》1982,27(3):299-306
The fluorescence and the excitation spectra are reported for the p-terphenyl crystal in the temperature range from 300 to 5 K. The appearance of a new band at 335 nm in the fluorescence spectrum and the large blue shift of the excitation spectrum, 1200 cm-1, on lowering the temperature are explained by the displacive-type phase transition in a wide temperature range, 191-20 K, where the dihedral angle θ of the TP molecule increases uniformly and continuously. 相似文献
30.
A new method for the preparation of highly substituted cyclohexenones is reported. [2 + 2] Cycloaddition of 2-silyloxydienes with allenecarboxylate affords the 1-alkenyl-3-alkylidenecyclobutanol silyl ethers. Thermolysis of these compounds affords the methylene cyclohexenyl silyl ethers with excellent exo selectivity (>95:5) when monosubstituted alkenyl groups are used, while the use of disubstituted alkenyl groups gives generally low selectivity ( approximately 2:1). However, rearrangement of the anion of the cyclobutanol (prepared by acidic hydrolysis of the TMS silyl ether) at low temperature gives the endo product with good to excellent diastereoselectivity (5-23:1). Two different mechanistic rationales are given for the two different processes: the first via a diradical and the second via a cleavage intramolecular Michael addition. Thus, the same starting material (e.g., 20) can be converted into either the exo or endo product, 22x or 22n, with good diastereocontrol by just changing the rearrangement conditions. 相似文献