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61.
D. V. Tsyganov A. P. Yakubov L. D. Konyushkin S. I. Firgang V. V. Semenov 《Russian Chemical Bulletin》2007,56(12):2460-2465
A series of analogs of the natural mitostatic agent combretastatin were synthesized by the reaction of nitrile oxides with
natural allylbenzenes, such as myristicin, apiol, and dillapiol. The 1,3-dipolar cycloaddition reactions in allylic systems
proceed regiospecifically. The reactions with trans isomers of propenylbenzenes, viz., isomyristicin, isoapiol, and isodillapiol, as dipolarophiles produce regioisomers.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2375–2380, December, 2007. 相似文献
62.
Samet AV Niyazymbetov ME Semenov VV Laikhter AL Evans DH 《The Journal of organic chemistry》1996,61(25):8786-8791
Regioselective Michael addition of nitro and heterocyclic compounds to levoglucosenone, 1, is effectively catalyzed by amines and also by cathodic electrolysis. In comparison to the base-catalyzed reaction, it was found that under electrochemical conditions the reaction proceeds under milder conditions and with higher yields. Cathodically-initiated Michael addition of thiols to levoglucosenone using small currents produces the previously unknown threo addition product in several instances. The normal erythro isomer, identified as the kinetic product, tends to be formed when large currents are used. In contrast, slow, low current electrolyses promote equilibration of the two forms so that erythro can be converted to threo by the retro reaction and readdition. Addition of 2-naphthalenethiol to (R)-(+)-apoverbenone is also reported. 相似文献
63.
A. A. Bogolyubov N. B. Chernysheva V. V. Nesterov M. Yu. Antipin V. V. Semenov 《Chemistry of Heterocyclic Compounds》2004,40(10):1305-1309
The dehydration of two 5,5-disubstituted 4-hydroxy-4-methyl-3-phenylaminooxazolidin-2-ones into the corresponding 4-methylene-3-phenylaminooxazolidin-2-ones has been carried out. The structure of the products was confirmed by X-ray diffraction analysis.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1512–1517, October, 2004. 相似文献
64.
The properties and the self-assembly of single comb macromolecules in solution were studied. The elastic properties of a polymer chain with a high density of side chains forming a cylindrical brush were discussed, in particular, its persistence length was calculated. The cases of brushes with flexible and rigid side chains, as well as brushes with two types of incompatible side segments, were considered. It was shown that brushes with rodlike dangling chains have a higher rigidity. In addition, a comb macromolecule with the hydrophobic main chain and hydrophilic side chains was considered. Such a macromolecules in a selective solvent forms a globule with the hydrophobic core and a soluble shell. The specific feature of the globule is its ability to acquire nonspherical spatial forms. Problems related to the stability and transformation of globule shape are discussed in detail. 相似文献
65.
O. V. Bryanskii V. V. Tolstikhina S. V. Zinchenko A. A. Semenov 《Chemistry of Natural Compounds》1993,28(6):556-560
A sesquiterpene glucoside has been isolated from a tissue culture ofScorzonera hispanica, and its structure has been established by mass spectrometry and two-dimensional NMR as 6,9-dihydroxy-4,10,14,15-tetradehydroguaian-6,12-olide 9-O--D-glucopyranoside.Irkursk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 640–645, November–December, 1992. 相似文献
66.
Results obtained in studying the structure of olefin and diene molecules, and complexes of these, in the ground and lower excited states by RHF, ROHF, GVB/DN, and 6-31G* quantum-chemical methods are presented. Attention is paid to the identity of the main structural and electronic parameters of triplet T
1 and singlet S
1 states forming a reactive fourfold spin-degenerate diradical equilibrium excited state (S·T)1 having the lowest energy. A new mechanism of cyclodimerization of ethylene and tetrafluoroethylene and anionic polymerization of dienes, involving the (S·T)1 states, is suggested. 相似文献
67.
Semenov V. V. Cherepennikova N. F. Khorshev S. Ya. Mushtina T. G. Lopatin M. A. Domrachev G. A. 《Russian Journal of Coordination Chemistry》2002,28(12):856-863
1-(3"-Amino)propylsilatrane (I) and 1-(3"-acetamido)propylsilatrane (II) react with anhydrous cobalt(II) chloride to give dichlorobis[1-(3"-amino)propylsilatrane]cobalt(II) {Co[NH2CH2CH2CH2Si(OCH2CH2)3N]2Cl2} (III) and dichlorobis[1-(3"-acetamido)propylsilatrane]cobalt(II) {Co[CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N]2Cl2} (IV). Being unstable, compound IV transforms into an imidic acid derivative. Reactions of silatranes I and II with dicobalt octacarbonyl afford hexakis[1-(3"-aminoamido)propylsilatrane]cobalt(II) bis(tetracarbonylcobaltate) {Co[NH2CH2CH2CH2Si(OCH2CH2)3N]4.8[HC(O)NHCH2CH2CH2Si(OCH2CH2)3N]1.2}[Co(CO)4]2 (V) and hexakis[1-(3"-acetamido)propylsilatrane]cobalt(II) bis(tetracarbonylcobaltate) {Co[CH3C(O)NHCH2CH2CH2Si(OCH2CH2)3N]6}[Co(CO)4]2 (VI), respectively. In acetonitrile, tetracarbonylcobaltate anions of compound VI are oxidized with atmospheric oxygen and moisture to cobalt hydroxocarbonate, giving a carbonate gel (VII). 相似文献
68.
Yu. A. Semenov 《Letters in Mathematical Physics》1977,1(5):379-385
In this paper we consider operatorsH 0 andV possessing the following properties:
- H 0 is a positive self-adjoint operator acting inL 2(M, γ) with γ a probability measure, so that exp(?tH 0) is a contraction onL 1(M, γ) for eacht>0.
- V is a semibounded multiplicative operator acting inL 2(M, γ) {fx379-1}
69.
Vera A. Vil' Yana A. Barsegyan Leah Kuhn Maria V. Ekimova Egor A. Semenov Alexander A. Korlyukov Alexander O. Terent'ev Igor V. Alabugin 《Chemical science》2020,11(20):5313
How far can we push the limits in removing stereoelectronic protection from an unstable intermediate? We address this question by exploring the interplay between the primary and secondary stereoelectronic effects in the Baeyer–Villiger (BV) rearrangement by experimental and computational studies of γ-OR-substituted γ-peroxylactones, the previously elusive non-strained Criegee intermediates (CI). These new cyclic peroxides were synthesized by the peroxidation of γ-ketoesters followed by in situ cyclization using a BF3·Et2O/H2O2 system. Although the primary effect (alignment of the migrating C–Rm bond with the breaking O–O bond) is active in the 6-membered ring, weakening of the secondary effect (donation from the OR lone pair to the breaking C–Rm bond) provides sufficient kinetic stabilization to allow the formation and isolation of stable γ-hydroperoxy-γ-peroxylactones with a methyl-substituent in the C6-position. Furthermore, supplementary protection is also provided by reactant stabilization originating from two new stereoelectronic factors, both identified and quantified for the first time in the present work. First, an unexpected boat preference in the γ-hydroperoxy-γ-peroxylactones weakens the primary stereoelectronic effects and introduces a ∼2 kcal mol−1 Curtin–Hammett penalty for reacquiring the more reactive chair conformation. Second, activation of the secondary stereoelectronic effect in the TS comes with a ∼2–3 kcal mol−1 penalty for giving up the exo-anomeric stabilization in the 6-membered Criegee intermediate. Together, the three new stereoelectronic factors (inverse α-effect, misalignment of reacting bonds in the boat conformation, and the exo-anomeric effect) illustrate the richness of stereoelectronic patterns in peroxide chemistry and provide experimentally significant kinetic stabilization to this new class of bisperoxides. Furthermore, mild reduction of γ-hydroperoxy-γ-peroxylactone with Ph3P produced an isolable γ-hydroxy-γ-peroxylactone, the first example of a structurally unencumbered CI where neither the primary nor the secondary stereoelectronic effect are impeded. Although this compound is relatively unstable, it does not undergo the BV reaction and instead follows a new mode of reactivity for the CI – a ring-opening process.Protecting stereoelectronic effects prevent Baeyer–Villiger rearrangement and stabilize γ-OX-γ-peroxylactones (X = H, OH), the previously elusive non-strained Criegee intermediates. 相似文献
70.
Published data on methods for the synthesis of indole derivatives (isogramines) containing a dimethylamino group at positions 1, 2 and also at various positions of the benzene ring in the indole bicycle and their chemical properties are reviewed.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 483–504, April, 2005. 相似文献