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71.
Štíbr B Bakardjiev M Holub J Růžička A Padělková Z Olejník R Švec P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(47):13156-13159
72.
Bohumil Zítka 《Czechoslovak Journal of Physics》1957,7(2):175-189
. , . . - , 500 10 000 30 500 . - , . 相似文献
73.
74.
Dolenský B Kroulík J Král V Sessler JL Dvoráková H Bour P Bernátková M Bucher C Lynch V 《Journal of the American Chemical Society》2004,126(42):13714-13722
A new, stepwise synthesis of calix[4]phyrins is described. It relies on the condensation of a ketone with pyrrole to form a dipyrromethane containing a quaternary carbon center that is subsequently condensed with an aromatic aldehyde. This methodology, in contrast to the previous rational approach described by this group (involving formation of a trisubstituted dipyrromethane via the condensation of an aldehyde with pyrrole, followed by condensation of this dipyrromethane with acetone), allows for a variety of bulky, ketone-derived substituents to be incorporated into the meso-like positions. The resulting systems, while all containing the same central macrocyclic core, display conformational properties that reflect the nature of these meso-like substituents; these conformational features were independently assessed by X-ray diffraction analysis, NMR spectroscopy, and quantum chemical calculations. 相似文献
75.
Unique Stereocontrol in Carborane Chemistry: Skeletal Alkylcarbonation (SAC) versus Exoskeletal Alkylmethylation (EAM) Reactions
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Dr. Mario Bakardjiev Dr. Josef Holub Dr. Jan Macháček Dr. Drahomír Hnyk Prof. Dr. Bohumil Štíbr Dr. Zdeňka Růžičková Prof. Dr. Aleš Růžička 《Angewandte Chemie (International ed. in English)》2015,54(16):4937-4940
Reactions between the arachno‐6,9‐C2B8H14 ( 1 ) dicarbaborane and acyl chlorides, RCOCl ( 2 ), are subject to stereocontrol that completely changes the nature of the reaction products. While most chlorides produce the 8‐R‐nido‐7,8,9‐C3B8H11 ( 3 ) tricarbollides (by skeletal alkylcarbonation=SAC), bulky RCOCls ( 2 ; where R=1‐adamantyl, 2 a ; 1‐mesityl, 2 b ; 9‐anthranyl, 2 c ; 1‐naphthyl, 2 d ) in 1,2‐dichloroethane (DCE) in the presence of triethylamine at 40–60 °C gave a series of entirely different 1‐R‐2‐CH3‐closo‐1,6‐C2B8H8 ( 4 ) dicarbaboranes upon acidification with conc. H2SO4 (by exosleletal alkylmehylation=EAM). Both types of reactions seem to proceed via a common [8‐R‐nido‐7,8,9‐C3B8H10]? ( 3? ) anion which in the EAM case is unstable because of steric crowd and undergoes rearrangement via the isomeric [R‐nido‐7,8,10‐C3B8H10]? tricarbollide structures which, on protonation, undergo reductive extraction of one CH vertex to generate the 2‐CH3 substituent in structure 4 . 相似文献
76.
Valík M Cejka J Havlík M Král V Dolenský B 《Chemical communications (Cambridge, England)》2007,(37):3835-3837
The first members of a new cavitand family, represented by calix-shaped tris Tr?ger's base diastereoisomers, are prepared via step-by-step synthesis as well as one-pot mixed troegeration. 相似文献
77.
Jan ejka Bohumil Kratochvíl Ivana Císaov Alexandr Jegorov 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(8):o428-o430
Simvastatin, or (1S,3R,7S,8S,8aR)‐8‐{2‐[(2R,4R)‐4‐hydroxy‐6‐oxo‐3,4,5,6‐tetrahydro‐2H‐pyran‐2‐yl]ethyl}‐3,7‐dimethyl‐1,2,3,7,8,8a‐hexahydronaphthalen‐1‐yl 2,2‐dimethylbutanoate, C25H38O5, is almost isostructural with lovastatin, and the general conformational features are closely related to those of other reported crystal structures of statins. The only hydrogen bond present facilitates the formation of infinite chains of molecules along the b axis. 相似文献
78.
Jií Kvapil Josef Kvapil Bohumil Perner Betislav Mnek 《Crystal Research and Technology》1975,10(10):1051-1056
Absorption spectra of molybdenum doped YAG crystals annealed in hydrogen, vacuum, oxygen and argon and exposed to an UV irradiation are given. Yellow or brown colour of the crystals is attributed to the O− centre formation connected with the reduction of molybdenum ions to a lower valency state. Most intensive yellow colour was shown by crystals, the argon annealing of which was followed by a treatment in oxygen at rather low temperature (∼1000 °C) and by UV irradiation. Two types of O− centres are suggested Blue colour of the samples annealed in argon is attributed to e− centres. 相似文献
79.
Lenka Zají?ková Ond?ej Jašek Bohumil David Nadě?da Pizúrová Lukáš Lazar 《Applied Surface Science》2009,255(10):5421-5424
The MW plasma torch (2.45 GHz) in the mixture of CH4/H2/Ar (42/430/1540 sccm) with added Fe(CO)5vapors was used for the synthesis of iron oxide nanoparticles and carbon nanotubes. The particles with well-defined facets consisting of Fe3O4 and -Fe2O3 and self-assembled into long chains were produced at the power of 360 W. At higher power of 440-460 W the deposit contained significant amount of multi-walled carbon nanotubes covered by iron oxide nanoparticles. The diameter of CNTs was 8-20 nm. The particles had Fe3O4 and/or -Fe2O3 cores of spherical shape covered by a thin layer of carbon. 相似文献
80.
Stíbr B Bakardjiev M Holub J Růzicka A Padelková Z Stepnicka P 《Inorganic chemistry》2011,50(7):3097-3102
A systematic method for the incorporation of the {(η(6)-Me(n)C(6)H(6-n))Fe} fragment into the dicarbollide cage was developed based on reactions between [(η(6)-Me(n)C(6)H(6-n))(2)Fe][PF(6)](2) salts (1) and Tl(2)[nido-7,8-C(2)B(9)H(11)]. These reactions proceed with elimination of one arene ligand to generate a complete series of the neutral [1-(η(6)-Me(n)C(6)H(6-n))-closo-1,2,3-FeC(2)B(9)H(11)] (2) complexes with n = 1-6 in yields ranging 15-70% depending on the arene. The structures of mesitylene and pentamethylbenzene complexes were established by X-ray diffraction analyses. All compounds were characterized by (11)B and (1)H NMR measurements, mass spectra, melting points and elemental analyses. Correlations between selected (1)H and (11)B NMR parameters and the Fe(II/III) redox potentials and the number of arene methyls for complexes 2 are linear. These facts establish direct evidence for a strictly additive character of electron donation by the methyl substituents to the arene ring and further to the Fe center and the second (dicarbollide) ligand.Correlations between the number of arene methyls (n) and selected (1)H and (11)B NMR parameters or the Fe(II/III) redox potentials for complexes [1-(η(6)-MenC(6)H(6-n))-closo-1,2,3-FeC(2)B(9)H(11)] are of strictly linear character. 相似文献