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31.
Conclusions In our view, the material examined in the present review indicates that, in spite of the appearance of more accurate methods of calculating the electronic structure and the increasing possibilities provided for their realization for fairly complex systems, the applied value of simple semiempirical methods, in particular the CNDO method, is far from exhausted. In the near future, semiempirical calculations will probably provide the chief means of studying the electronic structures of complex molecules, by becoming accessible to an increasing circle of chemists.Leningrad State University. Translated from Zhurnal Strukturnoi Khimii, Vol. 17, No. 3, pp. 549–577, May–June, 1976. 相似文献
32.
The known triterpene tetraoside holothurin A has been isolated from the Pacific Ocean holothurianHolothuria squamifera. By using two independent methods — enzymatic cleavage and two-stage Smith degradation — 22,25-epoxyholost-9(11)-ene-3β,12α,17α-triol, C30H46O6, which is the native aglycone of holothurin A, was obtained. The structure of the native aglycone has been established on the basis of the results of IR, mass, and PMR spectroscopy. 相似文献
33.
O. V. Sizova A. I. Panin V. I. Baranovskii N. V. Ivanova 《Journal of Structural Chemistry》1996,37(2):171-180
Semiempirical INDO-E/S calculations of [RuX6]q (X=NH3, q=+2, +3; X=CN−, q=−4, −3) complexes are performed to demonstrate that the MO relaxation in the electronically excited state can be taken
into account by introducing certain double excitations into the configuration interaction matrix; the principles of selection
of the excitations are discussed. The calculation results are compared with the experimental electronic absorption spectra.
St. Petersburg State University. Translated fromZhurnal Struktumoi Khimii, Vol. 37, No. 2, pp. 195–205, March–April, 1996.
Translated by I. Izvekova 相似文献
34.
Alexander V Lebedev Marina V Ivanova Alexander A Timoshin Enno K Ruuge 《Chemphyschem》2007,8(12):1863-1869
The unexpected effects of Ca(2+) on the free-radical chain reactions of dopamine, norepinephrine, isoproterenol, and pyrocatechol oxidation are studied using oxygen consumption measurements, EPR-spectroscopy, UV/VIS spectrophotometry, and by potentiometric titration. It is found that the formation of Ca(2+)-catecholate complexes is accompanied by an increase in the dissociation constants (K(ai) ) of their phenolic hydroxyls. At pH>pK(ai) and in the presence of alkaline-earth metal cations, the rate of catecholate oxidation increases (Ca(2+), Mg(2+)> Sr(2+), Ba(2+)), whereas on addition of Zn ions the rate decreases. The effects of Group II metal cations on catecholate autoxidation are concomitant with a transient increase of the EPR signal for metal-semiquinonate complexes. Therefore, the effects of Ca(2+) and other alkaline-earth metal cations on catecholate autoxidation can be defined as 1) additional deprotonation of catechol OH-groups involved in the formation of M(2+)-catecholate complexes, the latter exceeding catechols in the susceptibility to dioxygen-induced oxidation and 2) formation of relatively stable free-radical intermediates responsible for chain propagation. 相似文献
35.
Ivanova SM Nolan BG Kobayashi Y Miller SM Anderson OP Strauss SH 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(2):503-510
The relative Lewis basicities of six Al(ORF)4- ions, Al[OC(CH3)(CF3)2]4-, Al(OC(CF3)3]4-, Al(OCPh(CF3)2]4-, Al[OC[4-C6H4(tBu)](CF3)2]4-, Al(OC(Cy)(CF3)2]4-, and Al(OCPh2(CF3)]4-, have been determined by measuring their relative coordinating abilities towards Li+ in dichloromethane. The relative Li- Lewis basicities of the Al(ORF)4- ions are linearly related to the aqueous pKa values of the corresponding parent HORF fluoroalcohols. The Lewis basicity of Al[OCH(CF3)2]4- could not be measured because two of these anions can coordinate to one Li+ cation. The structures of LiAl[OCH(CF3)2]4 and [1-Et-3-Me-1,3-C3H3N2][Li[Al[OCH(CF3)2)4]2] were determined. 相似文献
36.
G. V. Grishina S. A. Abdulganeeva V. M. Potapov I. A. Ivanova A. A. Espenbetov Yu. T. Struchkov I. A. Grishina A. I. Lutsenko 《Chemistry of Heterocyclic Compounds》1985,21(12):1362-1368
The Michael addition of acrylonitrile to the pyrrolidine enamine of 1-(S--phenyl-ethyl)-4-piperidone proceeds with the formation of. a 1:1 mixture of l-(S--phenyl ethyl)-3-(2-cyanoethyl)-4-piperidone diastereomers. A diastereomer isolated in pure form was shown by x-ray diffraction structural analysis to have S-configuration of the new chiral center at C(3) of the piperidone ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp, 1656–1662, December, 1985. 相似文献
37.
T. M. Ivanova M. I. Bazanov A. V. Petrov E. S. Yurina 《Russian Journal of Coordination Chemistry》2006,32(1):71-74
Bi-, tri-, and tetradentate macroheterocylic ligands, i.e., structural analogs of phthalocyanine, are studied by X-ray photoelectron
spectroscopy. The X-ray photoelectron spectra of N1s lines of the nitrogen atoms of these compounds are analyzed. The binding energies and integrated intensities of N1s lines of the nitrogen atoms are determined and the effective charges on the nitrogen atoms are calculated. The structures
of bi-, tri-and tetradentate macroheterocyclic ligands containing isoindole, benzene, and pyridine fragments are established
on the basis of the data obtained. 相似文献
38.
A. S. Ivanova M. V. Mikhan' G. M. Alikina G. S. Litvak E. M. Moroz E. B. Burgina 《Kinetics and Catalysis》2000,41(6):816-825
The possibility for the formation of garnet structures in the Mn–Fe–Zr–O and Ca–Sm–Zr–O systems obtained by the precipitation of the corresponding salts is studied. It is shown that, in the Mn–Fe–Zr–O system, garnet is crystallized at 860–920°C, for which probable cation distribution is estimated to be {Zr2.5
4+Mn0.5
2+}[Mn2
2+](Fe2.5
3+Mn0.5
3+)O12. In the Ca–Sm–Zr–O system, the perovskite CaZrO3, pyrochlore Sm2Zr2O7, and CaO are formed at 900–1200°C, but compounds with garnet structures are not found. The reported systems are characterized by surface areas of 300–450 m2/g at 450°C, and they have the polydisperse distribution of pores over sizes. The introduction of surfactants at the stage of component mixing enables an increase in the overall pore volume and mechanical strength of these systems. The Mn–Fe–Zr and Ca–Sm–Zr compositions are active catalysts for the complete oxidation of hydrocarbons. 相似文献
39.
Grinevich V. I. Ivanova N. V. Kostrov V. V. 《Russian Journal of Applied Chemistry》2003,76(4):561-565
Data on the kinetics of plasma-enhanced and plasma-enhanced catalytic oxidation of carbon(II) oxide with IK-1-6 catalyst are presented. The influence exerted by IK-1-6 catalyst on the conversion of carbon-containing components of the CO-CO2-CH4-SO2-air gas mixture in barrier-discharge plasma is analyzed. 相似文献
40.
E. I. Voronina G. M. Ostapchuk T. M. Ivanova T. A. Babushkina L. B. Shagalov N. N. Suvorov 《Chemistry of Heterocyclic Compounds》1984,20(3):275-277
It is shown that, in addition to the usually formed 3-formyl-4,5-benzindole, 2-formyl-4,5-benzindole can be obtained via the Vilsmeier reaction. The IR, PMR, and UV spectra of the 2- and 3-formyl isomers are compared, and their possible conformations are discussed.See [1] for Communication 22.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 343–345, March, 1984. 相似文献