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81.
O. E. Nasakin E. G. Nikolaev P. B. Terent'ev A. Kh. Bulai B. A. Khaskin K. Dager 《Chemistry of Heterocyclic Compounds》1984,20(11):1206-1210
The products of the addition of tetracyanoethylene to ketones react smoothly with aliphatic, aromatic, and heterocyclic aldehydes to give 4,8,8-tricyano-3-imino-2, 6-dioxabicyclo[2.2.2]octanes. The structures of the reaction products were confirmed by 13C, IR, and mass spectral data.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1462–1466, November, 1984. 相似文献
82.
Synthesis and properties of monodisperse oligofluorene-functionalized truxenes: highly fluorescent star-shaped architectures 总被引:2,自引:0,他引:2
Kanibolotsky AL Berridge R Skabara PJ Perepichka IF Bradley DD Koeberg M 《Journal of the American Chemical Society》2004,126(42):13695-13702
This paper describes the strategy toward novel monodisperse, well-defined, star-shaped oligofluorenes with a central truxene core and from monofluorene to quaterfluorene arms. Introduction of solubilizing n-hexyl groups at both fluorene and truxene moieties results in highly soluble, intrinsically two-dimensional nanosized macromolecules T1-T4. The radius for the largest oligomer of ca. 3.9 nm represents one of the largest known star-shaped conjugated systems. Cyclic voltammetry experiments reveal reversible or quasi-reversible oxidation and reduction processes (Eox = +0.74 to 0.80 V, Ered = -2.66 to 2.80 eV vs Fc/Fc+), demonstrating excellent electrochemical stability toward both p- and n-doping, while the band gaps of the oligomers are quite high (EgCV = 3.20-3.40 eV). Close band gaps of 3.05-3.29 eV have been estimated from the electron absorption spectra. These star-shaped macromolecules demonstrate good thermal stability (up to 400-420 degrees C) and improved glass transition temperatures with an increase in length of the oligofluorene arms (from Tg = 63 degrees C for T1 to 116 degrees C for T4) and show very efficient blue photoluminescence (lambdaPL = 398-422 nm) in both solution (PhiPL = 70-86%) and solid state (PhiPL = 43-60%). Spectroelectrochemical experiments reveal that compounds T1-T4 are stable electrochromic systems which change their color reversibly from colorless in the neutral state (approximately 340-400 nm) to colored (from red to purple color; approximately 500-600 nm) in the oxidized state. 相似文献
83.
L.V. Vinogradova V.N. Zgonnik N.I. Nikolaev Kh.B. Tsvetanov 《European Polymer Journal》1979,15(6):545-550
The electric conductivity of polybutadienyl-lithium and polyisoprenyl-lithium has been investigated in tetrahydrofuran and dimethoxyethane solutions over wide temperature and concentration ranges (0 to ?70°; 7·10?2 to 1·10?7 and 5·10?3 to 1·10?7 mol/l). Dissociation constants, enthalpy and entropy of dissociation of ion pairs, relative constants for formation of ion triplets, and interionic distances were calculated for each system investigated. The nature of “living” chains under these conditions is considered. 相似文献
84.
Summary The liquid phase oxidation of gold in donor-acceptor organic and aqueous-organic media has been studied. The compounds [AuCl(Me2S)], [AuBr(Me2S)], [AuBr3(Me2S)], [Me3S][AuBr4], [Me3S][AuBr4(Me2S)]·H2O, [Me3SO]-[AuBr4]·H2O, [Me3S][Au2Br7(Me2S)2]·3H2O, [Me3S]2-[Au2Br8]·2DMSO·H2O, [Me2(Bu)SO][AuBr4]·H2O and [Me3S]Br were isolated by dissolution of Au0 in DMSO-RX mixtures (R = H or Bu; X = Cl or Br). The products were characterized by elemental analysis and i.r. spectroscopy. The nature of the Au0-DMSO-RX systems and the oxidant species are discussed in terms of a newly-developed concept of donor-acceptor electron transport (DAET) systems. 相似文献
85.
Popov IA Chen H Kharybin ON Nikolaev EN Cooks RG 《Chemical communications (Cambridge, England)》2005,(15):1953-1955
A simple, fast and direct method is presented for detecting traces of solid explosives on cotton swabs or in particulate samples: ions are transferred into a mass spectrometer after thermal desorption and corona discharge chemical ionization in ambient air; specificity is enhanced using ambient ion/molecule reactions or by conventional tandem mass spectrometry. 相似文献
86.
Luminescence spectra and luminescence decay kinetics of uranyl sulphate water and uranyl nitrate acetone solutions of different concentrations have been studied. Similar experiments have been done with uranyl sulphate powder under vacuum. It has been experimentally shown that the hydrolysis of uranyl sulphate in water takes place, and under low salt concentrations (0.1-4.0 times 10-4 M) a luminescence of a basic form of the photoexcited ion with a tentative structure of UO2 OH+ * has been observed. The luminescence of the acidic form UO+ * has been observed under higher salt concentrations (1–4 times 10-2 M) in water and under any salt concentration in acetone. The acidic form has the characteristic emission spectrum possessing vibrational structure. The luminescence concentrational quenching of both photoexcited uranyl forms and exciplex emission have not been observed. The effect of a number of organic quenchers and molecular oxygen on uranyl luminescence has been studied. There is no luminescence quenching by O2 up to 2 times 106 Pa (20 atm) pressure. The low effectiveness of energy transfer from the photoexcited uranyl forms has been explained in terms of strong steric screening of 5f-uranium (VI) orbital by oxygen atoms and by external filled up uranium electronic shells. 相似文献
87.
L.V. Vinogradova N.I. Nikolaev V.N. Sgonnik B.L. Erussalimsky G.V. Sinitsina Ch.B. Tsvetanov I.M. Panayotov 《European Polymer Journal》1981,17(5):517-520
The parallel changes in the electric conductivity and u.v. spectra of polybutadienyl- and polyisoprenyl-lithium (MnLi) have been investigated in tetrahydrofuran and dimethoxyethane solutions during prolonged storage at 0 and 25°. A considerable dependence of the rate of these changes on the nature of the medium and Mn Li concentration was found. The decrease in the initiating activity during storage has been estimated for the PBLi-THF system. 相似文献
88.
Igor E. Uflyand Andrei G. Starikov Vladimir S. Savostjanov Anatoly D. Pomogailo 《Transition Metal Chemistry》1991,16(1):126-129
Summary The spatial and electronic structures of the complexes [Co(AAm)4(H2O)2](NO3)2 (1), Co(AAm)4Cl2 (2), [Ni(AAm)4(H2O)2](NO3)2 (3) and Ni(AAm)4Cl2 (4), where AAm is acrylamide, and the products of their radical, frontal and post-grafting polymerization have been studied by electronic spectroscopy. The complexes (1), (3) and (4) were found to have pseudooctahedral structures in both the solid and solution phases. A change in the spatial structure of complex (2) was established in going from the crystal (tetragonally distorted octahedral) to solution (tetrahedral). The coordination environment of the metal centre does not change markedly during polymerization of the metal-containing monomers. 相似文献
89.
Critical factors for high-performance physically adsorbed (dynamic) polymeric wall coatings for capillary electrophoresis of DNA 总被引:2,自引:0,他引:2
Doherty EA Berglund KD Buchholz BA Kourkine IV Przybycien TM Tilton RD Barron AE 《Electrophoresis》2002,23(16):2766-2776
Physically adsorbed (dynamic) polymeric wall coatings for microchannel electrophoresis have distinct advantages over covalently linked coatings. In order to determine the critical factors that control the formation of dynamic wall coatings, we have created a set of model polymers and copolymers based on N,N-dimethylacrylamide (DMA) and N,N-diethylacrylamide (DEA), and studied their adsorption behavior from aqueous solution as well as their performance for microchannel electrophoresis of DNA. This study is revealing in terms of the polymer properties that help create an "ideal" wall coating. Our measurements indicate that the chemical nature of the coating polymer strongly impacts its electroosmotic flow (EOF) suppression capabilities. Additionally, we find that a critical polymer chain length is required for polymers of this type to perform effectively as microchannel wall coatings. The effective mobilities of double-stranded (dsDNA) fragments within dynamically coated capillaries were determined in order to correlate polymer hydrophobicity with separation performance. Even for dsDNA, which is not expected to be a strongly adsorbing analyte, wall coating hydrophobicity has a deleterious influence on separation performance. 相似文献
90.
Voinov MA Polienko JF Schanding T Bobko AA Khramtsov VV Gatilov YV Rybalova TV Smirnov AI Grigor'ev IA 《The Journal of organic chemistry》2005,70(24):9702-9711
[reaction: see text] An approach to the synthesis of new imidazoline nitroxides bearing an N',N'-disubstituted amidine group is reported. The approach is based on the alkylation of diamagnetic 4-R-amino-1,2,2,5,5-pentamethyl-3-imidazolines with bromoacetic acid ethyl ester; the products of alkylation are further oxidized to the corresponding nitroxides. The approach allows a variety of functional groups to be introduced into the nitroxide molecule structure. Alkylation with bromoacetic acid ethyl ester was found to proceed with high regioselectivity and afford the products of exo-alkylation. The regiochemical assignment is made on the basis of 13C NMR spectra and confirmed by X-ray diffraction study. All of the nitroxides synthesized here were shown to have pH-dependent EPR spectra with pKa ranging from 3.5 to 6.2. For nitroxides 13 bearing the carboxylic group remote to the nitroxide moiety, the changes in isotropic magnetic parameters of EPR spectra due to reversible deprotonation of the carboxylic group were found to be small. For these nitroxides, we demonstrate an alternative approach for pKa determination that is based on measuring the peak-to-peak line width of the EPR spectrum in the presence of the paramagnetic broadening agent potassium ferricyanide. The partition coefficients of nitroxides in octanol/H2O and octanol/phosphate buffer solution mixtures were measured to reveal a range of their lipophilicities. 相似文献