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71.
Blumberger J Bernasconi L Tavernelli I Vuilleumier R Sprik M 《Journal of the American Chemical Society》2004,126(12):3928-3938
Electronic states and solvation of Cu and Ag aqua ions are investigated by comparing the Cu(2+) + e(-)--> Cu(+) and Ag(2+) + e(-)--> Ag(+) redox reactions using density functional-based computational methods. The coordination number of aqueous Cu(2+) is found to fluctuate between 5 and 6 and reduces to 2 for Cu(+), which forms a tightly bound linear dihydrate. Reduction of Ag(2+) changes the coordination number from 5 to 4. The energetics of the oxidation reactions is analyzed by comparing vertical ionization potentials, relaxation energies, and vertical electron affinities. The model is validated by a computation of the free energy of the full redox reaction Ag(2+) + Cu(+) --> Ag(+) + Cu(2+). Investigation of the one-electron states shows that the redox active frontier orbitals are confined to the energy gap between occupied and empty states of the pure solvent and localized on the metal ion hydration complex. The effect of solvent fluctuations on the electronic states is highlighted in a computation of the UV absorption spectrum of Cu(+) and Ag(+). 相似文献
72.
The nitrate radical, NO(3), is photochemically unstable but is one of the most chemically important species in the nocturnal atmosphere. It is accompanied by the presence of dinitrogen pentoxide, N(2)O(5), with which it is in rapid thermal equilibrium at lower tropospheric temperatures. These two nitrogen oxides participate in numerous atmospheric chemical systems. NO(3) reactions with VOCs and organic sulphur species are important, or in some cases even dominant, oxidation pathways, impacting the budgets of these species and their degradation products. These oxidative reactions, together with the ozonolysis of alkenes, are also responsible for the nighttime production and cycling of OH and peroxy (HO(2) + RO(2)) radicals. In addition, reactions of NO(3) with biogenic hydrocarbons are particularly efficient and are responsible for the production of organic nitrates and secondary organic aerosol. Heterogeneous chemistry of N(2)O(5) is one of the major processes responsible for the atmospheric removal of nitrogen oxides as well as the cycling of halogen species though the production of nitryl chloride, ClNO(2). The chemistry of NO(3) and N(2)O(5) is also important to the regulation of both tropospheric and stratospheric ozone. Here we review the essential features of this atmospheric chemistry, along with field observations of NO(3), N(2)O(5), nighttime peroxy and OH radicals, and related compounds. This review builds on existing reviews of this chemistry, and encompasses field, laboratory and modelling work spanning more than three decades. 相似文献
73.
Anger E Srebro M Vanthuyne N Toupet L Rigaut S Roussel C Autschbach J Crassous J Réau R 《Journal of the American Chemical Society》2012,134(38):15628-15631
Introducing metal-vinyl ruthenium moieties onto [6]helicene results in a significant enhancement of the chiroptical properties due to strong metal-ligand electronic interactions. The electro-active Ru centers allow the achievement of the first purely helicene-based redox-triggered chiroptical switches. A combination of electrochemical, spectroscopic, and theoretical techniques reveals that the helicene moiety is a noninnocent ligand bearing a significant spin density. 相似文献
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Chengshuo Shen Dr. Emmanuel Anger Dr. Monika Srebro Dr. Nicolas Vanthuyne Dr. Loïc Toupet Prof. Christian Roussel Prof. Jochen Autschbach Prof. Régis Réau Dr. Jeanne Crassous 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(49):16722-16728
Homochiral and heterochiral cis‐bis‐cycloplatinated‐[6]helicene derivatives 1 b1, 2 , as representative examples of platina[6]helicenes that share a common platinum center, have been prepared. A diastereo‐ and enantioselective synthesis, which combines CH activation and dynamic isomerization from heterochiral structure 1 b2 into homochiral structure 1 b1 , is also described. Overall, this isomerization process results in the transfer of chiral information from one helicene moiety to the other one. The chiroptical properties of homochiral (P)‐ and (M)‐ 1 b1 were greatly modified upon oxidation into their corresponding (P)‐ and (M)‐diiodo‐PtIV complexes ( 5 ). The changes were also analyzed by performing theoretical calculations. C? H activation in the synthesis of organometallic helicenes is further demonstrated by the preparation of cis‐bis‐cycloplatinated‐[8]helicene 1 c . 相似文献
76.
Jochen Beyermann Joachim Kötz Werner Jaeger Stig E. Friberg 《Journal of Dispersion Science and Technology》2013,34(7):1809-1820
The influence of different amounts of anionic copolymers of N-Methyl N-vinyl acetamide (NMVA) and acrylic acid with various charge densities on the formation of the lamellar liquid crystal formed by sodium dodecyl sulfate (SDS)/decanol/water was investigated by means of polarization microscopy, small angle x-ray scattering (SAXS), transmission electron microscopy and rheology. On the contrary to the incorporation of poly(acrylic acid) 相似文献
77.
Recent measurements revealed that commercial magnesium standard solutions showed isotopic abundance variations, which cannot clearly be distinguished from each other by calibrating against the only available isotopic reference material, SRM 980, or reference materials made from SRM 980 like IRMM-009. Therefore new SI-traceable magnesium isotopic reference materials are required. 相似文献
78.
Jochen Lutz The Vinh Ho Richard H. Fish Andreas Schmid 《Journal of organometallic chemistry》2004,689(25):4783-4790
The biocatalytic, regioselective hydroxylation of 2-hydroxybiphenyl to the corresponding catechol was accomplished utilizing the monooxygenase 2-hydroxybiphenyl 3-monooxygenase (HbpA). The necessary natural 1,4-dihydronicotinamde adenine dinucleotide (NADH) co-factor for this biocatalytic process was replaced by a biomimetic co-factor, N-benzyl-1,4-dihydronicotinamide, 1b. The interaction between the flavin (FAD) containing HbpA enzyme and the corresponding biomimetic NADH compound, N-benzyl-1,4-dihdronicotinamide, 1b, for hydride transfer, was shown to readily occur. The in situ recycling of the reduced NADH biomimic 1b from 1a was accomplished with [Cp*Rh(bpy)H](Cl); however, productive coupling of this regeneration reaction to the enzymatic hydroxylation reaction was not totally successful, due to a deactivation process concerning the HbpA enzyme peripheral groups; i.e., -SH or -NH2 possibly reacting with the precatalyst, [Cp*Rh(bpy)(H2O)](Cl)2, and thus inhibiting the co-factor regeneration process. The deactivation mechanism was studied, and a promising strategy of derivatizing these peripheral -SH or -NH2 groups with a polymer containing epoxide was successful in circumventing the undesired interaction between HbpA and the precatalyst. This latter strategy allowed tandem co-factor regeneration using 1a or 2a, [Cp*Rh(bpy)(H2O)](Cl)2, and formate ion, in conjunction with the polymer bound, FAD containing HbpA enzyme to provide the catechol product. 相似文献
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