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151.
Based on experimental data about the density of very dilute solutions of H2O and D2O in 1,4-dioxane, hexamethylphosphotriamide, and acetonitrile at 278.15 K-318.15 K we determined the limiting partial molar volume (error ±0.03 cm3·mol−1) and dilatability of the water component. A correlation equation has been derived which relates the isotope effect (IE) in the limiting excess partial molar dilatability of water to the energy of the H2O-solvent hydrogen bond. The stated IE may be used as a “structural indicator” for evaluating the ability of an aprotic dipolar solvent to undergo specific interactions through hydrogen bonding.Original Russian Text Copyright © 2004 by E. V. Ivanov, V. K. Abrosimov, and E. Yu. Lebedeva__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1020–1026, November–December, 2004. 相似文献
152.
Adducts of bis(dimethyldithiocarbamato)zinc and -copper(II) complexes with pyridine, [M(Py)(Mdtc)2], and their benzene solvates [M(Py)(Mdtc)2] · 0.5C6H6 were synthesized. The electron paramagnetic resonance method and solid-state 13C and 15N CP/MAS NMR spectroscopy were used to perform a comparative study of the compounds obtained. The EPR data showed that the geometry of Cu(II) coordination polyhedra both in the adduct itself [Cu(Py)(Mdtc)2], and in its solvate, [Cu(Py)(Mdtc)2] · 0.5C6H6 is intermediate between a square pyramid (SP) and a trigonal bipyramid (TBP), the contribution from the latter being dominant (75%) in [Cu(Py)(Mdtc)2]. In the solvated adduct [Cu(Py)(Mdtc)2] · 0.5C6H6, the copper(II) polyhedron is distorted to form an SP-enriched structure (the contribution from TBP is reduced to 55%). It was found NMR data that [Zn(Py)(Mdtc)2] exists in a single high-symmetry molecular form. Coordinated pyridine molecule shows molecular motion about the Zn–N bond. The solvation of the adduct results in structural nonequivalence of the Mdtc–ligands in [Zn(Py)(Mdtc)2] · 0.5C6H6. Signals in the 15N NMR spectra were assigned to the structural positions of the atoms in the previously described molecular structure of a solvated adduct. It was found that the heterogeneous reaction of adduct formation during the absorption of pyridine from the gas phase by polycrystalline [Zn2(Mdtc)4] species is accompanied by the dissociation of binuclear molecules. 相似文献
153.
The thermal decomposition of the Pt(II) complexes with cyclobutane-and cycloheptanespiro-5′-hydantoins were studied by TG
and DTA techniques. The Pt(II) complex with cyclobutanespiro-5′hydantoin (PtCBH) was stable up to 115°C (388 K) and Pt(II)
complex with cycloheptanespiro-5′-hydantoin (PtCHTH) was stable up to 150°C (423 K). After the thermal decomposition of PtCBH
the solid residue was platinum, while the decomposition of PtCHTH gave a mixture of platinum carbides (PtC2, Pt2C3). 相似文献
154.
Micellization ofn-decylamine in aqueous solution leads to substantial decrease in its pK
a, and increase in its reactivity in the nucleophilic substitution ofp-nitrophenylic esters of carboxylic acids (up to 70 times compared to ethylamine which forms no micelles). The influence of cetylpyridinium bromide on the acid-base properties ofn-decylamine and its reactivity was investigated. It was found that the reaction withn-decylamine can be accelerated or retarded depending on the hydrophobicity of the esters. The quantitative characteristics of the mieellar catalytic processes were estimated.Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 2, pp. 366–370, February, 1996. 相似文献
155.
The condensation of ethyl 3-aryl-2-cyano-2-butenoates with benzylideneanilines in the presence of aluminum chloride affords 1,4,6-triaryl-2-oxo-1,2,5,6-tetrahydropyridine-2-carbonitriles; the reaction with hydrobenzamide gives N-unsubstituted tetrahydropyridine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 209–211, February, 1988. 相似文献
156.
Christo Ivanov A. Dobrev Tzv. Tcholakova G. Dontchev 《Journal of organometallic chemistry》1975,92(2):125-130
By treating ω-cyanocarboxylic acids with lithium amide in liquid ammonia, salts, of the type [NCCH(CH2)nCOOLi]Li are prepared. The formation of these salts is confirmed by their reaction with N-benzolydiphenylketimine and benzophenone to give ω-diarlylate, ω-benzoylamino- and ω-hydroxy-ψ-cyanocarboxylic acids respectively. 相似文献
157.
A. V. Kucherov A. V. Ivanov T. N. Kucherova A. N. Shigapov 《Kinetics and Catalysis》2006,47(6):881-890
The surface of pure mesoporous SiO2 with an MCM-41 structure has been modified by introducing Al, Zr, or W ions (1 mmol/g). The original and modified materials have been loaded with Cu2+ ions. The distribution, properties, and thermal stability of different Cu2+ sites have been studied by EPR and IR spectroscopy. The resulting catalysts have been tested for activity in ethane oxidation. The modification of original MCM-41 exerts a very strong effect on the stability of isolated Cu2+ ions on the support surface. Among the modified supports, Al-MCM-41 affords the highest thermal stability and degree of dispersion (70–80%) of the copper-containing phase. There is no correlation between the total number of surface Cu2+ sites and the catalytic activity. The specific catalytic activity (per Cu2+ ion accessible to the reactants) depends strongly on the local structure of the sites. The isolated pentacoordinated Cu2+ sites stabilized by the Al-MCM-41 surface show a comparatively high activity in the sample calcined at 520°C. The heat treatment of Cu/Al-MCM-41 at 650–750°C reduces the specific activity of the catalytic sites by a factor of ~20 without sintering the copper phase, as in the case of CuHZSM-5 zeolite. The least dispersed copper phase, which is observed in the original MCM-41 and likely consists of aggregates of weakly interacting Cu2+ ions, exhibits the highest specific activity and thermal stability. In the case of Cu/W-MCM-41, heat treatment causes both the sintering of copper particles and a decrease in the specific activity of the surface Cu2+ ions. 相似文献
158.
It was demonstrated that cation exchangers of different nature can be used for the sorption preconcentration of iron(II) as phenanthrolinate and its determination in the adsorbent phase by diffuse reflectance spectrometry and chromaticity measurements. A procedure was developed for the determination of iron in solutions with a detection limit of 2.5 g/L. A scale was proposed for the visual determination of iron(II) at concentrations down to 0.4 g/L. The test procedure was verified using water samples from the Severnaya Dvina estuary and Dvinskii Bay taken during the summer and winter periods in 2000–2001. 相似文献
159.
V. L. Ivanov V. A. Artemov A. M. Shestopalov V. N. Nesterov Yu. T. Struchkov V. P. Litvinov 《Chemistry of Heterocyclic Compounds》1996,32(3):359-364
A novel regioselective synthesis of thieno[3, 2-blpyridines and thiazolo[4,5-blpyridines from 2-bromo-I-phenyl ethylidenemalononitrile is proposed. In the case of the thiazolo[4, 5-b]pyridines, the intermediate 5-(2, 2-dicyano-l-phenylvinyl)thiazoles were separated. Formation of the thiazolo(4,5-b]pyridines was confirmed by x-ray analysis.A. D. Zelinski Institute of Organic Synthesis, Russian Academy of Sciences, Moscow 117913. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 413–419, March, 1996. Original article submitted December 22, 1995. 相似文献
160.
L. A. Isupova V. A. Sadykov V. P. Ivanov A. A. Rar S. V. Tsybulya M. P. Andrianova V. N. Kolomilchuk A. N. Petrov O. F. Kononchuk 《Reaction Kinetics and Catalysis Letters》1994,53(1):223-229
Catalytic properties of strontium-substituted lanthanum cobaltites La1–xSrxCoO3 in the reaction of CO oxidation were compared with the data about chemical composition of the surface and bulk defect structure. It was found that (1) the initial catalytic activity correlates with the cobalt concentration on the surface; (2) surface composition differs from the bulk one; (3) the steady-state activity is proportional to the density of bulk extended defects. Under our experimental conditions no role of point defects was noted. 相似文献