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991.
Syntheses of Boc-protected 4-amino- and 5-amino-pyrrole-2-carboxylic acid methyl esters have been achieved and the structures of these compounds have been fully characterized by detailed NMR studies. 相似文献
992.
The rate of cyclization of pentafluoro- (1) and 4-Cl-2,3,5,6-tetrafluoro-2-NHY-diphenyl ethers (2a, Y=Ac;2b, Y=H;2c, Y=Me) to form phenoxazines on refluxing in DMF increases with an increase in the nucleophilicity of the amino group. The cyclization of the N-acetyl derivative2a is followed by the Smiles rearrangement, whereas the transformation of ethers2b andc, containing free amino and N-methylamino groups, respectively, includes mainly an attack on the amino group at theortho-position of the fluorinated ring. In the case of ether2c, introduction of K2CO3 into the reaction mixture results in cyclization with the Smiles rearrangement.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1101–1105, June, 1993. 相似文献
993.
EstimationoflocaldensityofsolventaboutthesoluteSolvatochromicbehaviorsofspectroscopicprobesarewidelyusedtoestimatethesol-ventstrengthofsupercriticalfluids(SCF,).i-3lnthiswork,thesolvatochrondcshiftofthen-n*transitionbandforacetone(O.o37mo1.L-')insupercrihcal(SC)CO2wasde-terminedbyUVspectroscopytostUdythesolvationeffect.TheMcRae-BaylissexpressionbasedonthedielectriccontinUUInmodelgivestherelahonshipbetWeenso1vatochromicshiftandpo1arizabilityofnonPolarsolvents4-5asfollows:wherevisthewave… 相似文献
994.
Dielectric permittivities of 2-pyrrolidinone - acetone, -dimethyl sulfoxide,-2-propanol, -dichloromethane and -water systems were measured as a function of mole fraction over the whole composition range at 30 and 50°C. The excess dielectric permittivities are predominantly negative for all the mixtures and the excess molar polarizations are negative except for 2-pyrrolidinone - water and 2-pyrrolidinone - dimethyl sulfoxide mixtures. The large negative excess quantities are indicative of the strong specific interactions between the like and unlike components of the solution mixtures. 相似文献
995.
Alessandro D'Aprano Ines Dorina Donato Vincenzo Turco Liveri 《Journal of solution chemistry》1989,18(8):785-793
Static dielectric constants, refractive indices and viscosities of 1-pentanol +2-methyl-2-butanol mixtures were measured at 5, 25 and 45°C. The results show that the mixing of the two isomers modifies the polarizability and the resistence of viscous flow of the system depending on the composition and temperature. Short range intermolecular interactions producing hetero-alcohol open dimers are considered. 相似文献
996.
Tin dioxide SnO2−δ is a pronounced n-type electron conductor due to its oxygen deficiency. This study investigates the rate of chemical diffusion of oxygen in SnO2−δ single crystals, which is a crucial step in the overall stoichiometry change of the material. The chemical diffusion coefficient Dδ was determined from conductivity- and EPR-relaxation methods. The temperature dependence was found to be . The dependence on crystal orientation, dopant content and oxygen partial pressure was below experimental error. The latter observation leads to the conclusion that the chemical diffusion coefficient is close to the diffusion coefficient of oxygen vacancies. Along with the relaxation process resulting from the chemical diffusion of oxygen, additional processes were observed. One of these was attributed to complications in the defect chemistry of the material. The relevance of the results for the kinetics of drift processes of Taguchi sensors is discussed. 相似文献
997.
Rubén A. Machado David Rivillo Lindora D’Ornelas Reinaldo Atencio Esperanza Galarza 《Journal of organometallic chemistry》2004,689(15):2486-2493
The reaction of the labile compound [Re2(CO)8(CH3CN)2] with trans-1,2-bis(2-pyridyl)ethene (C12H10N2) at room temperature in tetrahydrofuran affords the compounds [Re2(μ:η3-C12H10N2)(CO)8] (1) and the oxidative addition product [Re2(μ-H)(μ:η3-C12H9N2)(CO)7] (2). When the reaction is carried out at temperatures of refluxing tetrahydrofuran, besides compounds 1 and 2, the oxidative addition product [Re2(μ-H)(μ:η4-C12H9N2)(CO)6] (3), the insertion product [Re2(μ:η4-C12H10N2)(CO)8] (4) and [Re2(μ:η6-C24H18N4)(CO)6] (5) are obtained. Compound 5 contains the organic ligand rtct-tetrakis(2-pyridyl)cyclobutandiyl which is derived from a [2 + 2] cycloaddition of 1,2-bis(2-pyridyl)ethene mediated by its coordination to the bimetallic framework. The molecular structures of 1, 2, 4 and 5 were confirmed by X-ray crystallographic studies. 相似文献
998.
E. H. Mørkved 《Chemistry of Heterocyclic Compounds》2007,43(9):1197-1201
Syntheses and spectroscopic characteristics are reported for eight pyrazine-2,3-dicarbonitriles substituted with maleimide
residue in addition to phenyl, 2-thienyl, or 2-furyl substituent.
__________
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1409–1414, September, 2007. 相似文献
999.
Helmut Spreitzer 《Monatshefte für Chemie / Chemical Monthly》1992,123(6-7):593-597
Summary The acetale-ketone9 was synthesized as precursor for the preparation of -santalol derivatives posessing a bicyclo[2.2.2]octane nucleus. After methylenation of the keto-group the subsequent acidic hydrolysis of the acetal leads via a Prins reaction of the liberated aldehyde with the methylene group to tricyclo[6.2.2.02, 7]dodecane derivatives. Their olfactory properties are described. 相似文献
1000.
A detailed singlet potential energy surface(PES) of [Si,C,O,O] system including a van der Waals (vdW) comples SiO……CO2,eight isomers,and twelve transiton states is investigated by MP2 and QCISD(T) (single-point)methods.At the final QCISD(T)/6-311 G(2df)//MP2/6-311G(d) level with zero-point energy included,the complex SiO……CO is found to be thermodynamically and kinetically the most stable species.Although eight ismoers are located as local energy minima,they are rather unstable toward isomerization to the dissociation fragments or comples.For the reaction of silocon atoms with carbon dioxide,two competitive reaction channels are found,and the primary pathway,which leads to the products of SiO and CO fragments,is the direct oxygen-abstraction process from carbon dioxide by silicon atom with a41.16 kJ/mol reaction barrier height.Our predications are in good agreement with previous experimental and theoretical studies. 相似文献