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991.
The intramolecular chain oxidation of artemisinin was analyzed using the parabolic model. The competition of the mono- and
bimolecular peroxy radicals formed from artemisinin was considered. Artemisinin is predominantly oxidized via the intramolecular chain mechanism to form polyatomic hydroperoxides. This results in the situation when, under aerobic conditions,
artemisinin is transformed from the monofunctional into polyfunctional initiator with several hydroperoxide groups. The enthalpy
was calculated, and the activation energies and rate constants of the intramolecular reactions of the artemisinin peroxy radicals,
as well as those of their bimolecular reactions with C-H, S-H, and O-H bonds of biological substrates and their analogs, were
calculated in the framework of the parabolic model. A new kinetic scheme for artemisinin oxidation was proposed.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 267–275, February, 2008. 相似文献
992.
Yuto Sumida Yuko Takada Sayuri Hayashi Koji Hirano Hideki Yorimitsu Dr. Koichiro Oshima Prof. Dr. 《化学:亚洲杂志》2008,3(1):119-125
The treatment of an aldehyde with a tertiary homoallylic alcohol at 100–250 °C in the presence of cesium carbonate and a rhodium catalyst leads to allyl transfer from the homoallylic alcohol to the aldehyde. The process includes Rh‐mediated retroallylation to form an allyl rhodium species as the key intermediate. The homoallylic alcohol formed initially through allyl transfer is converted under the reaction conditions into the corresponding saturated ketone when bulky ligands are used. Microwave heating at 250 °C accelerates the reaction significantly. 相似文献
993.
Grzegorz Mlostoń Marta Woźnicka Józef Drabowicz Anthony Linden Heinz Heimgartner 《Helvetica chimica acta》2008,91(8):1419-1429
The reactions of 3‐phenyl‐1‐azabicyclo[1.1.0]butane with α‐chlorosulfenyl chlorides and sulfinyl chlorides lead to the corresponding sulfenamides and sulfinamides, respectively, which possess an azetidine ring. It is proposed that a two‐step mechanism occurs involving an intermediate carbenium ion, which is formed by the addition of the electrophile at the N‐atom and cleavage of the N(1)? C(3) bond. The structures of 9b and 10b are established by X‐ray crystallography. 相似文献
994.
The title cyclohexenone 1d undergoes photodimerization selectively at the exocyclic C?C bond to give a 1 : 1 mixture of 1,2‐dialkynyl‐1,2‐dimethylcyclobutanes 6 and 7 . On irradiation in the presence of 2,3‐dimethylbuta‐1,3‐diene, 1d affords bicyclo[8.4.0]tetradeca‐1,2,3,7‐tetraen‐11‐one 9 . This – formal – (6+4)‐cycloadduct undergoes quantitative isomerization to 3‐cycloheptadienyl‐2,5,5‐trimethylcyclohex‐2‐enone 11 on treatment with basic silica gel. 相似文献
995.
New naphtho‐aza‐crown ethers containing different phenolic side‐arms attached through the ortho‐position of the phenol have been prepared under solvent‐free conditions. The starting macrocyclic naphtho‐aza‐crown ether 2 was obtained by treatment of naphthalene dicarboxylic acid diester 1 with diethylenetriamine in EtOH at room temperature for two days without stirring in 77% yield (Scheme 1). Phenolic ligands ( 3 – 14 ) were synthesized by the Mannich reaction of the secondary macrocyclic amine 2 with the substituted phenols using nontoxic and inexpensive CaCl2. This procedure was applied successfully for the synthesis of Mannich bases from simple secondary amines. The CaCl2 powder can be reused up to three times after simple washing with dry acetone. 相似文献
996.
Aurelia Pascariu Mircea Mracec Stefan Berger 《International journal of quantum chemistry》2008,108(6):1052-1058
Dynamic NMR spectroscopy at very low temperatures (148–182 K) reveal the dynamic behavior of the (2‐tri(3‐furyl)‐3‐methyl‐4‐cyclopropenyl‐oxaphosphetane) generated during a Wittig reaction between tri(3‐furyl)ethylphosphonium iodine and cyclopropylaldehyde. The possibility of formation of different adducts between Li+ ions and oxaphosphetane or betainic intermediates was checked calculating the formation enthalpies using the MNDO, AM1, and PM3 semiempirical MO methods. The observed species are interpreted as oxaphosphetane complexes with lithium ions present in solution. Quantum mechanical calculations confirm the spectroscopic results. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
997.
Wojciech Grochala 《Journal of fluorine chemistry》2008,129(2):82-90
The available thermodynamic data for a variety of oxides, chlorides and fluorides of various elements and for the AgF2/AgF, AgF2/Ag2O redox pairs are analyzed in detail. We show that AgF2 is capable of oxidizing a vast majority of oxides and chlorides with the concomitant evolution of O2 or Cl2, respectively. Interesting cases are discussed of the inertness of sulfates, perchlorates and nitrates against AgF2. In addition, perfluorinated amines should not be susceptible to oxidation and they might form complexes with AgII. The DFT calculations support the view that AgII transfers substantial share of d9 hole into the oxide and chloride bands in hypothetical model compounds. 相似文献
998.
Piyali Datta Chaudhuri 《Journal of organometallic chemistry》2008,693(3):567-573
Stable pallada(II)cycles featuring Csp2-Pd and Csp3-Pd bonds reacted with vinyl- and alkynyl(phenyl)iodonium salts to generate two new geminal carbon-carbon bonds to the terminal carbon of the vinyl and alkynyl substituents providing benzofuran and dihydrobenzofuran heterocycles. The new annulation process was rationalized by the involvement of Pd(IV) intermediates arising via an initial oxidative addition of hypervalent iodonium electrophiles to the Pd(II) center. Reaction monitoring via low temperature 1H NMR spectroscopy was performed, and organopalladium(II) intermediates featuring a new Csp2-Csp2 or Csp2-Csp bond were isolated and characterized, providing insights into the regiochemical course of the proposed mechanistic pathway. 相似文献
999.
N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
1000.
E. B. Melnikova M. M. Elchaninov A. A. Milov B. S. Lukyanov 《Chemistry of Heterocyclic Compounds》2008,44(9):1070-1076
The electrophilic reactions (nitration, bromination, hydroxymethylation, formylation, acylation) and radical substitution
reactions (nitration, arylation) of 2-(2-furyl)benzothiazole have been studied. It was found that all of the reactions occur
at position 5 of the furan ring. Only nitration in PPA gave the 5',6-dinitro derivative. Quantum-chemical calculation data
for the electron density distribution in the neutral and protonated 2-(2-furyl)benzothiazole molecules are given.
Dedicated to Boris Aleksandrovich Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1331–1338, September, 2008. 相似文献