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21.
Procedures are described for the high pressure carbonation of substituted 3-pyridinols, yielding the corresponding pyridine carboxylic acids. Treatment of o-aminohydroxypyridinecarboxylic acid with cyanogen and with phosgene, respectively, gave access to oxazolo[4,5-b]pyridine derivatives. The synthesis of 3-amino-6-methyl-2-pyridinecarboxylic acid was accomplished by heating 3-hydroxy-6-methyl-2-pyridinecarboxylic acid in liquid ammonia. 相似文献
22.
Udo Kaatze 《Journal of solution chemistry》1997,26(11):1049-1112
A tutorial on dielectric (relaxation) spectrometry of liquids is given in this article. Some methods of measuring complex
(electric) permittivity spectra are briefly described. Results for water are presented and related to characteristic properties
of the liquid structure and to models of the molecular dynamics, particularly as resulting from computer simulation studies.
Dielectric spectra for aqueous solutions of low weight electrolytes, polyelectrolytes, small molecules, and polymers are discussed
to illustrate effects of kinetic depolarization, structure saturation, as well as positive, negative, and hydrophobic hydration.
Reference is also made to fluctuations in the hydrogen bond network of mixtures of water with liquids that are completely
miscible with this unique solvent. 相似文献
23.
Puzenko A Hayashi Y Ryabov YE Balin I Feldman Y Kaatze U Behrends R 《The journal of physical chemistry. B》2005,109(12):6031-6035
We discuss the relaxation dynamics of glycerol-water mixtures, as studied by dielectric spectroscopy in the frequency range from 1 Hz to 250 MHz and at temperatures between 173 and 323 K. The experimental results obtained for the glycerol-rich mixtures suggest that the main dielectric relaxation process, as well as the so-called high-frequency "excess wing" (EW) and dc conductivity, follow the same temperature dependence. This result indicates that all of these processes are induced by the same molecular origin. A new phenomenological function is proposed to describe the whole dielectric spectrum in the covered frequency range, and some possible mechanisms of dielectric behaviors through the dc conductivity, the main relaxation process, and the EW are discussed. 相似文献
24.
Robert Weis Reto Brun Robert Saf Werner Seebacher 《Monatshefte für Chemie / Chemical Monthly》2003,134(7):1019-1026
Summary. 4-Aminobicyclo[2.2.2]octanones which were prepared in one-pot-reactions from benzylidene acetone and dialkylammonium rhodanides
were reduced stereoselectively to their corresponding alcohols. The activities of the bicyclic compounds against causative
organisms of tropical deseases were examined. The 4-aminobicyclo[2.2.2]octan-2-ols were in general more active against Trypanosoma b. rhodesiense and Plasmodium falciparum than the corresponding keto compounds.
Corresponding author. E-mail: robert.weis@uni-graz.at
Received November 27, 2002; accepted December 2, 2002
Published online May 2, 2003 相似文献
25.
Maximilian W. Kuntze-Fechner Hendrik Verplancke Lukas Tendera Martin Diefenbach Ivo Krummenacher Holger Braunschweig Todd B. Marder Max C. Holthausen Udo Radius 《Chemical science》2020,11(40):11009
The reaction of [Ni(Mes2Im)2] (1) (Mes2Im = 1,3-dimesityl-imidazolin-2-ylidene) with polyfluorinated arenes as well as mechanistic investigations concerning the insertion of 1 and [Ni(iPr2Im)2] (1ipr) (iPr2Im = 1,3-diisopropyl-imidazolin-2-ylidene) into the C–F bond of C6F6 is reported. The reaction of 1 with different fluoroaromatics leads to formation of the nickel fluoroaryl fluoride complexes trans-[Ni(Mes2Im)2(F)(ArF)] (ArF = 4-CF3-C6F42, C6F53, 2,3,5,6-C6F4N 4, 2,3,5,6-C6F4H 5, 2,3,5-C6F3H26, 3,5-C6F2H37) in fair to good yields with the exception of the formation of the pentafluorophenyl complex 3 (less than 20%). Radical species and other diamagnetic side products were detected for the reaction of 1 with C6F6, in line with a radical pathway for the C–F bond activation step using 1. The difluoride complex trans-[Ni(Mes2Im)2(F)2] (9), the bis(aryl) complex trans-[Ni(Mes2Im)2(C6F5)2] (15), the structurally characterized nickel(i) complex trans-[NiI(Mes2Im)2(C6F5)] (11) and the metal radical trans-[NiI(Mes2Im)2(F)] (12) were identified. Complex 11, and related [NiI(Mes2Im)2(2,3,5,6-C6F4H)] (13) and [NiI(Mes2Im)2(2,3,5-C6F3H2)] (14), were synthesized independently by reaction of trans-[Ni(Mes2Im)2(F)(ArF)] with PhSiH3. Simple electron transfer from 1 to C6F6 was excluded, as the redox potentials of the reaction partners do not match and [Ni(Mes2Im)2]+, which was prepared independently, was not detected. DFT calculations were performed on the insertion of [Ni(iPr2Im)2] (1ipr) and [Ni(Mes2Im)2] (1) into the C–F bond of C6F6. For 1ipr, concerted and NHC-assisted pathways were identified as having the lowest kinetic barriers, whereas for 1, a radical mechanism with fluoride abstraction and an NHC-assisted pathway are both associated with almost the same kinetic barrier.A combined experimental and theoretical study on the mechanism of the C–F bond activation of C6F6 with [Ni(NHC)2] is provided. 相似文献
26.
Robert Weis Marcel Kaiser Reto Brun Robert Saf Werner Seebacher 《Monatshefte für Chemie / Chemical Monthly》2006,137(10):1365-1374
Summary. 4-Aminobicyclo[2.2.2]octan-2-ones and -ols showed activity against the causative organisms of East African sleeping sickness
and Malaria tropica. Several imino derivatives of the ketones were more active. Now hydrazono analogues and 3-hydroximino
derivatives of the ketones and alcohols were synthesized. The structures of the obtained isomers were elucidated by NMR spectroscopy.
A single phenylhydrazone exhibited quite good antitrypanosomal activity in the range of already known imino analogues. 相似文献
27.
Robert Weis Marcel Kaiser Reto Brun Robert Saf Werner Seebacher 《Monatshefte für Chemie / Chemical Monthly》2006,31(6):1365-1374
4-Aminobicyclo[2.2.2]octan-2-ones and -ols showed activity against the causative organisms of East African sleeping sickness
and Malaria tropica. Several imino derivatives of the ketones were more active. Now hydrazono analogues and 3-hydroximino
derivatives of the ketones and alcohols were synthesized. The structures of the obtained isomers were elucidated by NMR spectroscopy.
A single phenylhydrazone exhibited quite good antitrypanosomal activity in the range of already known imino analogues. 相似文献
28.
Cyclic sulphurylphosphazochloride (I: formula see ?Inhaltsübersicht”?) reacts with ammonia or methylamine forming the. tetramide(II) and (III), respectively, and with aniline or dimethylamine forming the diamide (IV) resp. (V). The synthesis of the diphenyl derivative (VI) is achieved starting from C6H5? PCl4. (II) gives with PCl5 the ionic compound (VII). 相似文献
29.
C D Weis 《Helvetica chimica acta》1968,51(7):1572-1581
A simple synthesis of tetrachlorophenanthrene starting from DDT has been realized. 1,1,1,2-tetrachloro-2,2-bis-(4-chlorophenyl)-ethane (I) and its rearranged product 1,1,2,2-tetrachloro-1,2-bis-(4-chlorophenyl)-ethane (V) and other analogs substituted by halogen in the para-position undergo a cycliarylation yielding 3,6,9,10-tetrahalogenophenanthrenes. Partial dechlorination of this tetrachlorophenanthrene yields 3,6-dichlorophenanthrene. Oxidation gives 3,6-dichloro-9,10-phenanthrenequinone, and chlorosulfonation leads to 3,6,9,10-tetrachloro-2,7-bis-(chlorosulfonyl)-phenanthrene. The mechanism of this cyclization reaction in presence of LEWIS acids is discussed and compared with the cyclization of DDT derivatives to yield fluorenones. 相似文献
30.
Platinum(II) and palladium(II) complexes of the potentially hexadentate P,N-donor ligand family Ar2P-X-PAr2 (X = (CH2)2 [dmape], cyclic-C5H8 [dmapcp]; Ar = o-N,N-dimethylanilinyl) are described. In CH2Cl2, the dmape complexes exist as equilibrium mixtures of MCl2(P,P'-dmape) and [MCl(P,P',N-dmape)]Cl isomers (M = Pd, Pt), governed by deltaH(o) = -19 +/- 4 kJ mol(-1) and deltaS(o) = -100 +/- 30 J mol(-1) K(-1) for M = Pt, and deltaH(o) = -11 +/- 7 kJ mol(-1) and deltaS(o) = -60 +/- 20 J mol(-1) K(-1) for M = Pd. The water-soluble dmapcp complexes exist solely in the [MCl(P,P',N-dmapcp)]Cl form, but the free and coordinated anilinyl rings in these complexes are in slow diastereoselective exchange. X-ray crystal structures for MCl2(P,P'-dmape) (M = Pd, Pt), and the [PdCl(P,P',N-dmape)]+ and [PtCl(P,P',N-dmapcp)]+ cations, are presented. Some of the complexes show marginal activity in water for the catalyzed hydration of maleic to malic acid, giving about 6-7% conversion in 24 h at 100 degrees C and substrate:catalyst loadings of 100:1. Attempts to synthesize a PdCl(P,P',N-dmapm)+ species led instead to isolation of [Pd(mu-Cl)(P,P'-dmapm)]2[PF6]2 (dmapm = Ar2PCH2Ar2). 相似文献