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排序方式: 共有141条查询结果,搜索用时 15 毫秒
81.
A new resin gel based on Spheron-Oxin(?) chelating ion-exchanger with anchored 8-hydroxyquinoline functional groups was tested for application in diffusive gradient in thin film technique (DGT) for determination of uranium. Selectivity of uranium uptake from model carbonate loaded solutions of natural water was studied under laboratory conditions and compared with selectivity of the conventional Chelex 100 based resin gel. The affinity of Spheron-Oxin(?) functional groups enables determination of the overall uranium concentration in water containing carbonates up to the concentration level of 10(2) mg L(-1). The effect of uranium binding to the polyacrylamide (APA) and agarose diffusive gels (AGE) was also studied. Uranium is probably bound in both gels by a weak interaction with traces of acrylic acid groups in the structure of APA gel and with pyruvic and sulfonic acid groups in the AGE gel. These sorption effects can be eliminated to the negligible level by prolonged deployment of DGT probes or by disassembling probes after the 1-2 days post-sampling period that is sufficient for release of uranium from diffusive gel and its sorption in resin gel. 相似文献
82.
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
83.
Ludk Toman Miroslav Janata Jií Spv
ek Petr Vl
ek Petra Ltalov Bohumil Masa Antonín Sikora 《Journal of polymer science. Part A, Polymer chemistry》2004,42(23):6098-6108
ABCBA‐type pentablock copolymers of methyl methacrylate (MMA), styrene (S), and isobutylene (IB) were prepared by a three‐step synthesis, which included atom transfer radical polymerization (ATRP) and cationic polymerization: (1) poly(methyl methacrylate) (PMMA) with terminal chlorine atoms was prepared by ATRP initiated with an aromatic difunctional initiator bearing two trichloromethyl groups under CuCl/2,2′‐bipyridine catalysis; (2) PMMA with the same catalyst was used for ATRP of styrene, which produced a poly(S‐b‐MMA‐b‐S) triblock copolymer; and (3) IB was polymerized cationically in the presence of the aforementioned triblock copolymer and BCl3, and this produced a poly(IB‐b‐S‐b‐MMA‐b‐S‐b‐IB) pentablock copolymer. The reaction temperature, varied from ?78 to ?25 °C, significantly affected the IB content in the product; the highest was obtained at ?25 °C. The formation of a pentablock copolymer with a narrow molecular weight distribution provided direct evidence of the presence of active chlorine at the ends of the poly(S‐b‐MMA‐b‐S) triblock copolymer, capable of the initiation of the cationic polymerization of IB in the presence of BCl3. A differential scanning calorimetry trace of the pentablock copolymer (20.1 mol % IB) showed the glass‐transition temperatures of three segregated domains, that is, polyisobutylene (?87.4 °C), polystyrene (95.6 °C), and PMMA (103.7 °C) blocks. One glass‐transition temperature (104.5 °C) was observed for the aforementioned triblock copolymer. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6098–6108, 2004 相似文献
84.
85.
Dipanjan Pan Ewald Roessl Jens‐Peter Schlomka Shelton D. Caruthers Angana Senpan Mike J. Scott John S. Allen Huiying Zhang Grace Hu Patrick J. Gaffney Eric T. Choi Volker Rasche Samuel A. Wickline Roland Proksa Gregory M. Lanza 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(50):9829-9833
86.
Jan Kučera Marie Kubešová Bohumil Bartoníček 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(2):685-691
Instrumental neutron activation analysis with k 0 standardization (k 0-INAA) was employed for elemental characterization of individual components of electrical cables currently used in safety systems of nuclear power plants (NPP). The analysis yielded information about the content of 35 elements. It has been found that the presently used cables would not satisfy requirements of qualification set for the new generation of NPP by “The European Utility Requirements for LWR Nuclear Power Plants”, because content of several elements exceeded the maximal admissible levels. This demonstrates that cable polymer materials for safety systems of the new generation NPP must be synthesized and controlled regarding the content of additives, which are undesired from the hygienic and radiological points of view. k 0-INAA proved to be a method of choice for elemental characterization of polymer materials of electrical cables as part of their qualification for use in NPP. 相似文献
87.
Josef Kadlec Radoslav Cipin Dalibor Cervinka Pavel Vorel Bohumil Klima 《Journal of Solid State Electrochemistry》2014,18(8):2307-2313
This article presents Li-ion accumulator system for the electric airplane VUT 051 RAY. This battery is a modular electric source which consists of 3,060 Li-ion NCR18650A accumulator cells connected in serial and parallel combinations, with a total capacity of 102 Ah and nominal voltage of 324 V. The contribution describes, inter alia, a battery monitoring system including accumulator balancing and also electric measurement results of one load cycle. 相似文献
88.
Bohumil Proksa Richard Hercek Tibor Liptaj Nada Prónayová 《Monatshefte für Chemie / Chemical Monthly》2009,140(5):485-487
Abstract A new compound was isolated from the reaction mixture after O-demethylation of 6-O-acetyl-10α-acetoxycodeine with boron tribromide. The structure of this compound, 10α-hydroxy-β-isomorphine, was elucidated by spectral data, and its spatial arrangement was deduced from an NOE experiment. Capillary zone
electrophoresis was used for separation of morphine and its 10-hydroxy analogues.
Graphical abstract
相似文献
89.
Interference effects of co-generated hydrides of arsenic, antimony and bismuth on trapping behavior of selenium hydride (analyte) within an iridium-modified, transversely heated graphite tube atomizer (THGA) were investigated. A twin-channel hydride generation system was used for independent separate generation and introduction of analyte and interferent hydrides, i.e. in a simultaneous and/or sequential analyte–interferent and interferent–analyte mode of operation. The influence of the analyte and modifier mass, interferent amount, trapping temperature and composition of the gaseous phase was studied. A simple approach for the elimination of mutual interference effects by modification of the gaseous phase with oxygen in a substoichiometric ratio to chemically generated hydrogen is proposed and the suppression of these interference effects is demonstrated. A hypothesis on the mechanism of trapping and mutual interference effects is drawn. 相似文献
90.
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