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71.
The reaction force is a global property of a chemical reaction that arises when applying the Hellmann–Feynmann theorem to
the potential energy surface that links reactants, products and transition states. In the present work, the reaction force
is defined rigorously from the cartesian components coming out from all forces exerted over each atom of a molecular system
during the chemical reaction; it is demonstrated that the reaction force is a scalar property.
An erratum to this article can be found at 相似文献
72.
Martí I Ferrer A Escorihuela J Burguete MI Luis SV 《Dalton transactions (Cambridge, England : 2003)》2012,41(22):6764-6776
A family of ligands derived from bis(amino amides) containing aliphatic spacers has been prepared, and their protonation and stability constants for the formation of Cu(2+) complexes have been determined potentiometrically. Important differences are associated to both the length of the aliphatic spacer and the nature of the side chains derived from the amino acid. In general, ligands containing aliphatic side chains display higher basicities as well as stability constants with Cu(2+). In the same way, basicities and stability constants tend to increase when decreasing the steric hindrance caused by the corresponding side-chain. FT-IR, UV-vis and ESI-MS were used for analyzing the complex species detected in the speciation diagram. UV-vis studies showed the presence of different coordination environments for the copper(II) complexes. Complexes with different stoichiometries can be formed in some instances. This was clearly highlighted with the help of ESI-MS experiments. 相似文献
73.
Roberto E. Di Paolo Dr. Hugh D. Burrows Prof. Jorge Morgado Prof. António L. Maçanita Prof. 《Chemphyschem》2009,10(2):448-454
Non‐Stokes–Einstein relaxation : The rate constant of conformational relaxation of a phenylenevinylene trimer (see picture) in different solvents is proportional to η?α, with α values decreasing from close to unity (low viscosity) to zero at sufficiently high solvent viscosity. This behaviour is attributed to the flexible methylbutyl side chains of the trimer, which partially screen the solvent friction.
74.
Jorge Rosales 《Fresenius' Journal of Analytical Chemistry》1972,260(5):361-363
Tertiäre Amine und Salze organischer Säuren werden in Acetanhydrid mit 5% Essigsäure durch anodische Proton-Erzeugung auf Platin in Gegenwart von Hydrochinon mit Hilfe der biamperometrischen Endpunkttechnik mit einem Wismutelektrodenpaar quantitativ bestimmt. Mengen von 0,5–0,9 mg wurden mit einer mittleren Abweichung von <1% analysiert. Die Ergebnisse stimmten zufriedenstellend mit denen aus thermometrischen und photometrischen Titrationen überein.Summary Tertiary amines and salts of organic acids have been quantitatively determined in acetic anhydride with 5% of acetic acid by means of anodic generation of protons on platinum in the presence of hydroquinone, applying a biamperometric end-point detection using an indicating system of bismuth electrodes. Amounts of 0.5–0.9 mg have been analysed with average deviations of <1%. Good agreement was obtained with the results of thermometric and photometric titrations.
Coulometrische Bestimmung von schwachen Basen unter Anwendung eines Wismut-Elektrodenpaars als Indicatorsystem相似文献
75.
76.
77.
78.
Jairo Quiroga Jorge Trilleras Rodrigo Abonía Antonio Marchal 《Tetrahedron letters》2010,51(7):1107-402
Several pyrimido[4,5-b]quinolines, flavin analogues, have been prepared by assisted microwave intramolecular cyclization of N4-substituted-2,4-diamino-6-chloropyrimidine-5-carbaldehydes. The reaction takes place with hydrolysis of amino-group and chlorine. Particularly valuable features of this method included the broader substrate scope and operational simplicity as well as increased safety for small-scale high-speed synthesis. 相似文献
79.
José Maria Esbrí Anna Bernaus Marta ávila David Kocman Eva M. García‐Noguero Beatriz Guerrero Xavier Gaona Rodrigo álvarez Gustavo Perez‐Gonzalez Manuel Valiente Pablo Higueras Milena Horvat Jorge Loredo 《Journal of synchrotron radiation》2010,17(2):179-186
The mobility, bioavailability and toxicity of mercury in the environment strongly depend on the chemical species in which it is present in soil, sediments, water or air. In mining districts, differences in mobility and bioavailability of mercury mainly arise from the different type of mineralization and ore processing. In this work, synchrotron‐based X‐ray absorption near‐edge spectroscopy (XANES) has been taken advantage of to study the speciation of mercury in geological samples from three of the largest European mercury mining districts: Almadén (Spain), Idria (Slovenia) and Asturias (Spain). XANES has been complemented with a single extraction protocol for the determination of Hg mobility. Ore, calcines, dump material, soil, sediment and suspended particles from the three sites have been considered in the study. In the three sites, rather insoluble sulfide compounds (cinnabar and metacinnabar) were found to predominate. Minor amounts of more soluble mercury compounds (chlorides and sulfates) were also identified in some samples. Single extraction procedures have put forward a strong dependence of the mobility with the concentration of chlorides and sulfates. Differences in efficiency of roasting furnaces from the three sites have been found. 相似文献
80.
Ronaldo Giro Liliana Y. A. Davila Angelita M. Machado Marilia J. Caldas Leni Akcelrud 《International journal of quantum chemistry》2010,110(4):885-892
We focus this work on the theoretical investigation of the block‐copolymer poly[oxyoctyleneoxy‐(2,6‐dimethoxy‐1,4phenylene‐1,2‐ethinylene‐phenanthrene‐2,4diyl) named as LaPPS19, recently proposed for optoelectronic applications. We used for that a variety of methods, from molecular mechanics to quantum semiempirical techniques (AM1, ZINDO/S‐CIS). Our results show that as expected isolated LaPPS19 chains present relevant electron localization over the phenanthrene group. We found, however, that LaPPS19 could assemble in a π‐stacked form, leading to impressive interchain interaction; the stacking induces electronic delocalization between neighbor chains and introduces new states below the phenanthrene‐related absorption; these results allowed us to associate the red‐shift of the absorption edge, seen in the experimental results, to spontaneous π‐stack aggregation of the chains. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献