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41.
Spectroscopic Investigations of Dicyanamidometallates(II), [M(NCNCN)4]2? of the Zinc Group The synthesis of homologeous tetrakis-(dicyanamido)metallates(II) [M(NCNCN)4]2? (M: Zn, Cd, Hg) is reported. The coordination type of the ambivalent anionic ligand is discussed on the basis of the IR, ESCA, 15N, and 13C NMR spectra of the new complexes. 相似文献
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43.
Acrylamide complexes of metal nitrates: [M(O‐OC(NH2)CHCH2)n(H2O)m][NO3]2 (M = Co( 1 ), Ni( 2 ) (n = 6 and m = 0) and Zn( 3 ) (n = 4 and m = 2)) have been determined by using single crystal X‐ray diffraction analysis. All complexes crystallize in the triclinic space group . The structures of 1 and 2 represent octahedral species [M(AAm)6]2+ (AAm = O‐OC(NH2)CHCH2 and M = Co or Ni) and uncoordinated nitrate ions. The structure of 3 involves the octahedral cation [Zn(AAm)4(H2O)2]2+ in which the Zn2+ environment includes oxygen atoms of four acrylamide and two water molecules that are stabilized using ionic nitrate ions. The observations of the solid‐state IR spectroscopic vibrational frequencies of these acrylamide complexes are in agreement with the crystal structures. 相似文献
44.
Beat Ernst Reinhold Oehrlein Daniel Bellu Jozef Gonda Rainer Jeschke Udo Nubbemeyer 《Helvetica chimica acta》1997,80(3):876-891
A novel type of ketene-Claisen rearrangement in which the precursor of the rearrangement is generated in situ by reaction of optically active allyl thioethers with dichloroketene is described. A characteristic feature of this rearrangement is the excellent chemoselectivity in favor of allyl thioethers vs. allyl ethers, i.e., exclusive chirality transfer of the allylic sulfur moiety is observed with 12, 13 , and 25--27 . The cyclic, optically active allyl thioethers (+)-(R)- 4 and (?)-(S)- 4 and the open-chain allyl thioethers 11--13 rearrange with in situ generated dichloroketene to the optically active thioesters (?)-(S)- 28 , (+)-(R)- 28 , and 31-33 , respectively. A chirality-transfer of > 99% in the cyclic cases (+)-(R)- 4 and (?)-(S)- 4 , and 96--98 % in the open-chain cases 11--13 is observed. Furthermore, the dichloroketene-Claisen rearrangement is characterized by a high asymmetric 1,2-induction. The chiral allylic sulfides 25--27 give the optically active thioesters 36--38 with a 1,2-induction > 99% as determined by NMR-shift experiments. 相似文献
45.
Crystal Structures of Acid Hydrates and Oxonium Salts. XX. Oxonium Tetrafluoroborates H3OBF4, [H5O2]BF4, and [H(CH3OH)2]BF4 The crystal structures of three oxonium tetrafluoroborates were determined. H3OBF4, oxonium tetrafluoroborate proper, is triclinic with space group P1 , Z = 2 and the unit cell dimensions a = 4.758, b = 6.047, c = 6.352 Å and α = 80.40, β = 79.48, γ = 88.25° at ?26°C. Cations H3O+ and anions BF4? are linked by hydrogen bonds O? H…?F into ribbons of condensed rings. In [H5O2]BF4 (diaquohydrogen tetrafluoroborate, monoclinic, P21/c, Z = 4, a = 6.584, b = 9.725, c = 7.084 Å, β = 95.15° at ?100°C) the hydrogen bond in the cation H5O2+ is 2.412 Å short, asymmetric and approximately centered and the linking of cations and anions three-dimensional. In [H(CH3OH)2]BF4 (Bis(methanol)hydrogen tetrafluoroborate, monoclinic, P21/c, Z = 4, a = 5.197, b = 14.458, c = 9.318 Å, β = 94.61° at ?50°C) the cation [H(CH3OH)2]+ is characterized for the first time in a crystal structure with an again very short (2.394 Å), asymmetric and effectively centered hydrogen bond. By further hydrogen bonds cations and anions form only dimers of the formula unit of centrosymmetric cyclic structure. 相似文献
46.
Peter Bellotti Maximilian Koy Christian Gutheil Steffen Heuvel Frank Glorius 《Chemical science》2021,12(5):1810
A highly modular radical cascade strategy based upon radical cyclisation/allylic substitution sequence between alkyl/aryl bromides, 1,3-dienes and nucleophiles ranging from sulfinates to amines, phenols and 1,3-dicarbonyls is described (>80 examples). Palladium phosphine complexes – which merge properties of photo- and cross coupling-catalysts – allow to forge three bonds with complete 1,4-selectivity and stereocontrol, delivering highly value added carbocyclic and heterocyclic motifs that can feature – inter alia – vicinal quaternary centers, free protic groups, gem-difluoro motifs and strained rings. Furthermore, a flow chemistry approach was for the first time applied in palladium–photocatalysed endeavors involving radicals.Highly modular three-bond three-component cascade featuring palladium as dual photoredox/cross coupling catalyst. 相似文献
47.
Markus Follmann Nils Griebenow Michael G. Hahn Ingo Hartung Franz‐Josef Mais Joachim Mittendorf Martina Schfer Hartmut Schirok Johannes‐Peter Stasch Friederike Stoll Alexander Straub Peter Jeschke Ralf Nauen Michael Edmund Beck Hans‐Wilhelm Engels Hans‐Georg Pirkl Reinhard Albers Rolf W. Albach Jens Krause Andreas Hoffmann Holger Casselmann Jeff Dormish 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2013,125(36):9503-9503
48.
Dr. Qingquan Lu Steffen Greßies Felix J. R. Klauck Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2017,56(23):6660-6664
A MnI-catalyzed regioselective C−H allenylation is reported that allows a broad range of 2-allenylindoles to be synthesized regioselectively on a gram scale under simple conditions. Notably, a highly efficient chirality transfer was observed (up to 93 % ee) in this transformation. This procedure was further found to allow, for the first time, the direct preparation of ketones by MnI-catalyzed C−H activation. Mechanistic investigations revealed that the precoordination of the oxygen atom to the manganese center as well as the congested tertiary carbon atom in the propargylic carbonates play a crucial role. 相似文献
49.
50.
Ingolf Kahle Stefan Krause Cornelius Krasselt Alexander Jakob Alexander Oehlke Colin Georgi Steffen Schulze Heinrich Lang Michael Hietschold Stefan Spange Christian von Borczyskowski 《Applied Physics A: Materials Science & Processing》2014,115(2):617-625
Optical properties of nanomaterials such as semiconductor and metal quantum dots are important for sensors and photovoltaic applications. We report on optical, microscopic, and AFM investigations on bulk and single nanoobjects such as metal and semiconducting nanoparticles. Firstly, of special interest is the investigation of Ag metal nanoaggregates formed in zeolites. Here, the defined structure of the zeolite serves both as size directing and a stabilizing agent. The size selected Ag aggregates fluoresce in the zeolite cages even after storage under ambient conditions for almost one year. In addition, single Ag particles escape the cages and can be investigated by fluorescence microscopy also with respect to sensor applications. Secondly, with respect to photovoltaic applications, energy transfer among organic dye molecules and semiconductor quantum dots is of great importance. We report on the extension of the optical absorption of ZnSe quantum dots into the UV regime and investigate excitation energy transfer within self-assembled nanoaggregates of surface functionalized QDs and fluorescent styrylpyridine dyes. 相似文献