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151.
J. N. Spencer J. E. Mihalick I. M. Paul W. J. Nicholson T. J. Nicholson X. Ke Q. He F. J. Carter S. E. Daniels L. J. Fenton J. L. Ealy S. Puppala C. H. Yoder 《Journal of solution chemistry》1994,23(6):711-720
Complex formation between 15-crown-5 and malononitrile was studied in twelve solvents by calorimetry. Thermodynamic parameters for the crown ether adduct were determined and used in a LFER analysis to ascertain the solvent effects on the complexation process. Enthalpy of solution data show that malononitrile is solvated by electron pair donation by the solvents and the crown ether is solvated by donating electron pairs to the solvents. The complex is more solvated than the monomers. 相似文献
152.
The free radical addition of thioacetic acid to 1,2-dicarbethoxy-1,2,3,6-tetrahydropyridazines gave high yields of 1,2-dicarbethoxy-4-S-thiolacetoxypiperidazines. The latter compounds served as the key intermediates in the preparation of 4-piperidazinethiols. The thiolacetoxy derivatives were partially hydrolyzed to afford the related 1,2-dicarbethoxy-4-piperidazinethiols. Complete hydrolysis of the thiolacetates gave rise to 4-piperidazinethiols. Finally, lithium aluminum hydride reduction of the thiolacetoxy esters produced a series of 1,2-dimethyl-4-piperidazinethiols. Only 4-piperidazinethiol hydrochloride showed appreciable anti-radiation activity. 相似文献
153.
154.
The preferential exchange uptake of the cations Cs+, Ba2+ and Zn2+ from pure solutions by zeolite-13X follows the order Q [Cs+]>Q [Ba2+]>Q [Zn2+], while in case of binary mixtures the order is Q [Ba2+(Zn2+)]>Q [Ba2+(Cs+)]>Q [Cs+(Zn2+)]>Q [Cs+(Ba2+)]>Q [Zn2+(Cs+)]>Q [Zn2+(Ba2+)]. Ba2+ uptake from mixtures shows the least suppression effect.
Cs+, Ba+2 Zn+2 -13 Q[Cs+]>Q[Ba+2]>Q[Zn+2] Q[Ba+2(mix Zn+2)]>Q[Ba+2(mix Cs+)]>Q[Cs+(mix Zn+2)]>Q[Cs+(mix Ba+2)]>Q[Zn+2(mix Cs+)]>Q[Zn+2(mix Ba+2)]. Ba+2 .相似文献
155.
The first deliberate syntheses of molecules in which pairs of quadruply bonded Mo2 units are bridged by N,N'-diarylterephthaloyldiamidate (aryl = Ph, m-CF3Ph) ligands are described. The addition of neutral N,N'-diarylterephthaloyldiamide to 2 equiv of [Mo2(DAniF)3(MeCN)2]+ (DAniF = N,N'-di-p-anisylformamidinate) followed by the introduction of excess H3CO- in MeCN results in the formation of (DAniF)3Mo2[(C6H5)NC(O)C6H4(O)CN(C6H5)]Mo2(DAniF)3 (1) and (DAniF)3Mo2[[(m-CF3)C6H5]NC(O)C6H4(O)CN[(m-CF3)C6H5]]Mo2(DAniF)3 (2). The DeltaE1/2 for the oxidation of each Mo2 unit is greater for these terephthaloyldiamidate-bridged molecules (approximately 100 mV) than for the analogous terephthalate-bridged compound (approximately 60 mV). Variation in the nature of the substituents on the diamidate nitrogen atoms offers a means to fine-tune the oxidation potentials of the Mo2 units. 相似文献
156.
Summary A method has been developed for the direct spectrophotometric determination of iron by using the reddish-orange coloured complex formed in the interaction of iron with 2-Hydroxy-methyl-6(2-hydroxymethyl-5-hydroxy-4-pyrone-6)pyranyl[3,2-b]pyran-4,8-dione (Woods reagent). The colour reaction follows Beer's law and is stable. The method is sensitive, reproducible and accurate. Of the several anions and cations studied, only a few interfered seriously in the determination of iron. However, the ones that do interfere seriously can be separated by conventional methods of separation.
Zusammenfassung Es wurde eine Methode zur direkten spektrophotometrischen Bestimmung von Eisen ausgearbeitet. Das Verfahren benutzt den rötlichorange gefärbten Komplex, der sich bei der Reaktion von Eisen mit 2-Hydroxymethyl-6 (2-hydroxymethyl-5-hydroxy-4-pyron-6) pyranyl-[3,2-b]pyran-4,8-dion (Woods' Reagens) bildet. Die Färbung ist beständig und befolgt das Beersche Gesetz. Das Verfahren ist empfindlich und gibt reproduzierbare und genaue Ergebnisse. Die wenigen Ionen, die beträchtliche Störungen verursachen, können nach üblichen Methoden abgetrennt werden.相似文献
157.
Clérac R Cotton FA Daniels LM Dunbar KR Murillo CA Pascual I 《Inorganic chemistry》2000,39(4):752-756
Seven compounds having in common a Cr3(dpa)4(3+) core (dpa = di(2-pyridyl)amide ion) have been prepared and all shown to have an unsymmetrical chain of three Cr atoms. This chain can be described as a pair of quadruply bonded Cr(II) atoms to which a Cr(III) atom is attached. No symmetrical chain has been found, contrary to a previous preliminary report. The seven compounds have been well characterized crystallographically, and their short and long Cr to Cr distances (A, in parentheses) are: 1 [Cr3(dpa)4Cl2]Cl.2CH2Cl2.THF (2.12, 2.47), 2 [Cr3(dpa)4Cl2]AlCl4.CH2Cl2 (2.011, 2.555), 3 [Cr3(dpa)4Cl2]FeCl4.CH2Cl2 (2.009, 2.562), 4 [Cr3(dpa)4Cl2]I3.THF.2H2O (2.08, 2.49), 5 [Cr3(dpa)4Cl2]PF6.2CH2Cl2 (2.08, 2.48), 6 [Cr3(dpa)4(BF4)F]BF4.2CH2Cl2 (1.900, 2.595), 7 [Cr3(dpa)4ClF]BF4.CH2Cl2.C6H14 (2.039, 2.507). Magnetic susceptibility measurements on 1 and 2 reveal mueff = 3.85 +/- 0.05 muB from 10 to 300 K. 相似文献
158.
Sandwich surface-enhanced Raman scattering (SERS) substrates (3S) utilizing coupling between continuous metal films and plasmonic particles were fabricated using silver mirrors, electrochemically roughened films, and various sizes of silver nanoparticles. The effect of excitation wavelength and nanoparticle size on SERS spectra of poly(vinylpyridine), selected as a model compound, was studied to determine the optimum conditions for the strongest SERS signal. The Raman enhancement resulted from the plasmon coupling of silver nanoparticles to the underlying continuous film as well as the lateral plasmon coupling between the silver nanoparticles. The formation of the charge transfer complex was also observed. The 3S configuration was used to obtain SERS spectra of dipicolinic acid (DPA), a chemical signature for Bacillus anthracis. 相似文献
159.
A compound reported earlier (Polyhedron 1989, 8, 2339) as (Bu(n)()(4)N)(2)H(2)[Mo(2)[Mo(CO)(4)(PhPO(2))(2)](2)] has been reexamined. We find that the hydrogen atoms in this formula are not present. Therefore, the complex must be considered as having a central triply bonded Mo(2)(6+) unit, instead of a quadruply bonded Mo(2)(4+) unit. Our conclusion is based on a variety of experimental evidence, including X-ray crystal structures of four crystal forms, as well as the neutron crystal structure of one. This explains the relatively long Mo-Mo bond lengths found in the range 2.1874(7)-2.2225(7) A and the absence of a delta --> delta transition in the visible spectrum. From electrochemistry we also find that the diphosphonate ligand has such an exceptional ability to stabilize higher oxidation states that even common solvents such as CH(2)Cl(2) and C(2)H(5)OH readily oxidize the Mo(2)(4+) unit that is introduced from the Mo(2)(O(2)CCH(3))(4) or [Mo(2)(O(2)CCH(3))(2)(NCCH(3))(6)](BF(4))(2) employed in the preparation. The only chemically reversible wave at E(1/2) = -1.54 V vs Ag/AgCl corresponds to the reduction process Mo(2)(6+) --> Mo(2)(5+). 相似文献
160.
Dr. Christopher Schulz Dr. Jörg Daniels Prof. Dr. Thomas Bredow Prof. Dr. Johannes Beck 《Angewandte Chemie (International ed. in English)》2016,55(3):1173-1177
As a new method for the synthesis of chalcogen polycationic clusters, the electrochemical dissolution of elemental tellurium in ionic liquids (IL) or in liquid SO2 is presented. ILs used are ethylmethylimidazolium triflate [OTf]? and tetraalkylammonium triflylimide [NTf2]?. Tristriflylmethanide [CTf3]? was used as [BuMeIm][CTf3] as the electrolyte in SO2. This allowed for the isolation of [Te4][CTf3]2, [Te6][OTf]4, and [Te8][NTf2]2 containing the square [Te4]2+, the prismatic [Te6]4+, and the novel barrelane‐shaped [Te8]2+. The compounds are novel compositions as they do not contain the usual halometalate anions, but rather common weakly coordinating anions. The 125Te NMR spectrum of an IL solution containing [Te8]2+ features only one broad signal at 2700 ppm. DFT calculations show that slight concerted displacements within the [Te8]2+ cluster lead to a fluxional molecular structure and a fast valence isomerism with a very low activation barrier of about 8 kJ mol?1. 相似文献