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31.
Allison K. O'Brien Neil B. Cramer Christopher N. Bowman 《Journal of polymer science. Part A, Polymer chemistry》2006,44(6):2007-2014
The overall effects of oxygen on thiol–acrylate photopolymerizations were characterized. Specially, the choice of thiol monomer chemistry, functionality, and concentration on the extent of oxygen inhibition were considered. As thiol concentration was increased, the degree of oxygen inhibition was greatly reduced because of chain transfer from the peroxy radical to the thiol. When comparing the copolymerization of 1,6‐hexanediol diacrylate with the alkane‐based thiol (1,6‐hexane dithiol) to the copolymerization with the propionate thiol (glycol dimercaptopropionate), it was found that the propionate system was much more reactive and polymerized to a greater extent in the presence of oxygen. In addition, the functionality was considered where the glycol dimercaptopropionate was compared to a tetrafunctional propionate of similar chemistry (pentaerythritol tetrakis(mercaptopropionate)). Given the same thiol concentration, the higher functionality thiol imparted a faster polymerization rate, due to the increased polymer system viscosity, which limited oxygen diffusion and decreased the extent of overall oxygen inhibition. Thus, preliminary insight is provided into how thiol monomer choice affects the extent of oxygen inhibition in thiol–acrylate photopolymerization. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2007–2014, 2006 相似文献
32.
33.
Much recent work has been done to investigate convergence of modified continued fractions (MCF's), following the proof by Thron and Waadeland [35] in 1980 that a limit-periodic MCFK(a
n
, 1;x
1), with
andnth approximant
相似文献
34.
Crystals of the title compound H2C(SiPh3)2 are triclinic, space group P, with a = 9.290(2), b = 12.128(4), c = 16.882(4) Å, α = 62.08(1), β = 106.88(1), γ = 117.28(2)° and Z = 2. The central skeletal angle SiCSi is 128.8(7)°. The structures of the molecules H2C(SiR3)2 (R = H, CH3, and Ph) are compared and discussed: a simple model for the skeletal geometry of species H2C(MR3)2 is proposed, and tested against experimental data and theoretical calculations. 相似文献
35.
Berhan Teclé Kaniz F. Siddiqui Christopher Ceccarelli John P. Oliver 《Journal of organometallic chemistry》1983,255(1):11-15
The structure of di-trans-β-styrylmercury has been determined by single crystal X-ray methods from counter data. The compound crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a 15.413(6), b 11.161(9), c 7.668(5) Å, V 1319(1) Å3, Dcalc 2.049 g/cm3, and Z = 4. The crystal was solved by conventional heavy atom techniques. The crystal consists of individual molecular units with the mercury atom located on a two fold axis of symmetry. The CHgC fragment is nearly linear with an angle of 178°. The β-styryl groups are oriented so that a dihedral angle of 66.8° is formed between the planes defined by HgC(1)C(2) and HgC(1)′C(2)′ fragments. The HgC bond distance is 2.07(4) Å. 相似文献
36.
Peter C. Cherry Derek N. Evans Christopher E. Newall Nigel S. Watson Peter Murray-Rust Judith Murray-Rust 《Tetrahedron letters》1980,21(6):561-564
1,4-Addition of sulphur nucleophiles to the diene () derived the pen-2-em () from clavulanic acid provides the thiadeoxa analogues (–). X-ray analysis of the ester () shows the thermodynamically stable isomers to have the same relative stereochemistry as clavulanic acid. 相似文献
37.
Abstract— The aerobic dye-sensitized photooxygenation of monohydric phenols proceeds by way of singlet oxygen under the conditions studied. Various phenols give different proportions of reaction with and quenching of singlet oxygen. Para-substituted 2,6-di-t-butylphenols show a linear correlation between the log of the total rate of singlet oxygen removal and their halfwave oxidation potentials; the same correlation is given for certain phenol methyl ethers. A Hammett plot using s?+ gives ρ - 1.72 ± 0.12, consistent with development of some charge in the quenching step. Reaction of photo-chemically generated singlet oxygen with 2,4,6-triphenylphenol gives 2,4,6-triphenylphenoxy radical as an intermediate in singlet oxygen quenching, although no overall reaction occurs. Kinetic analysis indicates that the radical is derived exclusively from the interaction of 2,4,6-triphenylphenol with singlet oxygen. A charge-transfer mechanism for quenching of singlet oxygen by phenols is proposed. 相似文献
38.
Armando J.L. Pombeiro Christopher J. Pickett Raymond L. Richards 《Journal of organometallic chemistry》1982,224(3):285-294
The isocyanide complexes trans-[ReCl(CNR)(dppe)2] (R Me, But, C6H4CH3-4, C6H4CH3-2, C6H4Cl-4, C6H4OCH3-4 and C6H3Cl2-2,6; dppe Ph2PCH2CH2PPh2) have been prepared by isocyanide displacement of dinitrogen from the parent complex trans-[ReCl(N2)(ddpe)2]. Their redox properties have been studied by cyclic voltammetry and are interpreted on the basis of the electronic properties and the geometry of the ligating isocyanides which are believed to be bent in these complexes, appearing to exhibit ligand parameter (PL) values ca. +0.3 V higher than those which would be expected for linear geometry. A very high polarisability (B ? 3.4) is observed for the {ReCl(dppe)2} site. 相似文献
39.
Christopher J. Chandler Leslie W. Deady James A. Reiss Vasilios Tzimos 《Journal of heterocyclic chemistry》1982,19(5):1017-1019
The preparation of a series of macrocycles, formed by reaction of HO-(-CH2-CH2-O-)nH with 1,10-phenanthroline-2,9-dicarbonyl chloride (n = 2,3,4) and 1,8-naphthyridine-2,7-dicarbonyl chloride (n = 3,4), is described. An improved synthetic route to 2,7-dimethyl-1,8-naphthyridine 9 is also reported. 相似文献
40.
Addition of palladium acetate to 2-(dicyclohexylphosphino)-phenylferrocene gave palladacycle 16 that is a very effective precatalyst for the Suzuki cross-coupling of aryl chlorides at room temperature (1 mol% 16) or 60 degrees C (> or = 0.01 mol% 16). 相似文献
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