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171.
Frank Herwig Köhler Hans Jürgen Kalder Ernst Otto Fischer 《Journal of organometallic chemistry》1975,85(2):C19-C22
Carbon-13 NMR data are reported for trimethyltin derivatives containing ERn groups where E C, Si, Ge, Sn, N, O and S including a series of cyclic amines with ring sizes from three to seven. Coupling constant values for the homologous series of fourth group derivatives give goood correlations with the electronegativity of E. The observation of the two-bond, ¦ 2J(119SnE13C) ¦ couplings only in the derivatives containing bulky R groups is rationalized by a bimolecular exchange of ERn groups in the concentrated solutions studied. 相似文献
172.
van Dijken A Bastiaansen JJ Kiggen NM Langeveld BM Rothe C Monkman A Bach I Stössel P Brunner K 《Journal of the American Chemical Society》2004,126(24):7718-7727
A carbazole homopolymer and carbazole copolymers based on 9,9'-dialkyl-[3,3']-bicarbazolyl, 2,5-diphenyl-[1,3,4]-oxadiazole and 9,9-bis(4-[3,7-dimethyloctyloxy]phenyl)fluorene were synthesized and their electrical and photophysical properties were characterized with respect to their application as host in phosphorescent polymer light-emitting diodes. It is shown that the triplet energy of a polymer depends on the specific connections between its building blocks. Without changing the composition of the polymer, its triplet energy can be increased from 2.3 to 2.6 eV by changing the way in which the different building blocks are coupled together. For poly(9-vinylcarbazole) (PVK), a carbazole polymer often used as host for high-energy triplet emitters in polymer light-emitting diodes, a large hole-injection barrier of about 1 eV exists due to the low-lying HOMO level of PVK. For all carbazole polymers presented here, the HOMO levels are much closer to the Fermi level of a commonly used anode such as ITO and/or a commonly used hole-injection layer such as PEDOT:PSS. This makes high current densities and consequently high luminance levels possible at moderate applied voltages in polymer light-emitting diodes. A double-layer polymer light-emitting diode is constructed comprising a PEDOT:PSS layer as hole-injection layer and a carbazole-oxadiazole copolymer doped with a green triplet emitter as emissive layer that shows an efficacy of 23 cd/A independent of current density and light output. 相似文献
173.
Bolm C Hildebrand JP Muñiz K Hermanns N 《Angewandte Chemie (International ed. in English)》2001,40(18):3284-3308
Addition and substitution reactions with carbon nucleophiles are fundamental processes in organic synthesis, and the development of general catalytic asymmetric variants thereof is still a major challenge today. In contrast to enantioselective alkyl transfer reactions, the corresponding arylations have not yet reached a high level of maturity. The existing protocols are either of no general applicability or are limited in terms of selectivity. This article summarizes established routes for catalytic asymmetric aryl transfer together with the latest developments in this area. The scope and limitations of this reaction are discussed. 相似文献
174.
The preparation, the spectroscopic characterization, the crystal structure and chemical reactions of the new six-membered heterocyclic betaine2 are reported; 2 is a representative of a possibly large group of yet unkonwn betaines of the general structure 8. 相似文献
175.
Palladium(II) bromide reacts with gallium(III) bromide in the presence of arenes yielding binuclear palladium(I) complexes [Pd2(GaBr4)2(arene)2], where arene=benzene (1), toluene (2) and p-xylene (3). Reaction of palladium(II) chloride with gallium(III) chloride in p-xylene leads to the analogous palladium(I) compound [Pd2(GaCl4)2(p-xylene)2] (4); the X-ray structures of 1-4 were determined. 相似文献
176.
Werner Marty Pramesh N. Kapoor Hans-Beat Bürgi Erwin Fischer 《Helvetica chimica acta》1987,70(1):158-170
The bidentate diphosphine ligand, 3,3′-oxybis[(dipenylphosphino)methylbenzene] ( 1 ) forms monomeric, trans-square-planar complexes MX2( 1 ) (M = Ni, Pd, Pt; X = Cl?, Br? I?, and, in part, N, NCS?, CN?, NO) as well as Pt(H)Cl( 1 ), Pt(H)Br( 1 ), and RhCl(CO)( 1 ). Polymeric species have been observed with substitutionally inert metal centres: trans-[PtCl2( 1 )]2 and cis-[PtCl2( 1 )]n (mean value of n ≈ 4–5) 31P-NMR, and selected IR and UV/VIS parameters are reported. Ligand 1 shows a marked preference for trans-spanning and monomeric chelate formation, despite its various degrees of freedom of internal rotation in the lignad backbone. The readily available ligand 1 as well as analogues with other donor atoms, therefore, appear useful in most potential applications of trans-spanning chelate ligands. The crystal structure of AgCl( 1 )·0.5 (CH3)2C?O·0.39 C6H12 (space group C2/c,a = 21.02 Å, b = 14.57 Å, c = 24.79 Å, β = 99.77°, V = 7531.4 Å3, Z = 8) confirms the presence of three-coordinate Ag( I ), with a coordination intermediate between a trigonal-planar and a T-shaped geometry (P-Ag-P = 145.61(8)°). 相似文献
177.
178.
Fischer CJ Gafni A Steel DG Schauerte JA 《Journal of the American Chemical Society》2002,124(35):10359-10366
The interpretation of room temperature phosphorescence studies of proteins requires an understanding of the mechanisms governing the tryptophan triplet-state lifetimes of residues fully exposed to solvent and those deeply buried in the hydrophobic core of proteins. Since solvents exposed tryptophans are expected to behave similarly to indole free in solution, it is important to have an accurate measure of the triplet state lifetime of indole in aqueous solution. Using photon counting techniques and low optical fluence (J/cm(2)), we observed the triplet-state lifetime of aqueous, deoxygenated indole and several indole derivatives to be approximately 40 micros, closely matching the previous reports by Bent and Hayon based on flash photolysis (12 micros; Bent, D. V.; Hayon, E. J. Am. Chem. Soc. 1975, 97, 2612-2619) but much shorter than the 1.2 ms lifetime observed more recently (Strambini, G. B.; Gonnelli, M. J. Am. Chem. Soc. 1995, 117, 7646-7651). However, we have now been able to reproduce the long lifetime reported by the latter workers for aqueous indole solutions and show that it likely arises from geminate recombination of the indole radical cation and solvated electron, a conclusion based on studies of the indole radical cation in water (Bent and Hayon, 1975). The evidence for this comes from a fast rise in the phosphorescence emission and measurements of a corresponding enhanced quantum yield in unbuffered solutions. This species can be readily quenched, and the corresponding fast rise disappears, leaving a monoexponential 40 micros decay, which we argue is the true indole triplet lifetime. The work is put in the context of room temperature phosphorescence studies of proteins. 相似文献
179.
Dieter Naumann Prof. Dr. Wieland Tyrra Dr. Hendrik T. M. Fischer Silke Kremer 《无机化学与普通化学杂志》2007,633(4):527-528
Tetrakis(pentafluorophenyl)tellurium(IV), Te(C6F5)4, was prepared from the reaction of TeCl4 and Mg(C6F5)Br. Crystallization of the crude product from n‐pentane at ?25 °C gave suitable single crystals. The title compound crystallizes in the monoclinic space group P21/c (Z = 8) with two independent molecules per unit cell. 相似文献
180.
Andrea Schfer Manfred Hesse Max Viscontini Henning Paul Berthold Fischer 《Helvetica chimica acta》1995,78(7):1763-1776
The experimental conditions developed for the detection of rather stable radical cations in solution by electrospray-ionization mass spectrometry (ESI-MS) of a FeII complex of 2-amino-5,6,7,8-tetrahydro-5-methylpteridin-4 (3H)-one ( 1c ) are used to observe the formation of the more unstable radical cations formed from 2-amino-5,6,7,8-tetrahydropteridin-4(3H)-one ( 1a ) and tris(pentane-2,4-dionato)iron(III) ([FeIII(acac)3]; 4 ) and to monitor their oxidation to the corresponding p-quinonoid dihydropterin complexes. These results contribute to the understanding of the important role played by 6β-5,6,7,8-tetrahydro-L -biopterin ( 1b ; a homologue of 1a ) together with iron as constituent of some cofactors. The complexes obtained from 1a and iron may be considered, e.g. as a model of the cofactor of the phenylalanine hydroxylase. Moreover, we describe an improved synthesis of 1c . 相似文献