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101.
The study of the degree of association of biologically active disubstituted fullerene derivatives at different substance concentrations
in an aqueous solution using the diffusion method showed that the nature of substituents exerts the strongest effect on the
degree of association of the fullerene derivatives. 相似文献
102.
P. A. Apanasevich A. A. Kananovich G. I. Timofeeva 《Journal of Applied Spectroscopy》2010,77(2):223-231
A method is developed for calculating the power and lasing threshold for longitudinally pumped lasers with intracavity Raman
conversion. The theoretical analysis is based on equations for the powers of light beams in the cavity. Expressions for the
power and lasing threshold of a Raman laser with self-conversion as functions of the parameters of the active medium, cavity,
and pumping, taking into account the overlap of all the interacting beams, are derived and analyzed. 相似文献
103.
Two types of redox processes, with the formation of (a) dissolved reduced forms of tungstates and (b) solid products, occur on a platinum electrode in metastable long-lived true solutions of isopolytungstates (pH 0.5) in the hydrogen adsorption region. The solid products accumulate on the platinum surface as crystalline films capable of reversible recharging. Basic parameters of the films are determined using cyclic voltammetry, x-ray diffractometry, and scanning tunneling microscopy. Based on a spectrophotometric analysis of solutions, redox conversions, observed in the hydrogen range of potentials, are referred to dissolved hepta- and decatungstates present in the system. 相似文献
104.
Bronstein LM Linton C Karlinsey R Stein B Timofeeva GI Svergun DI Konarev PI Kozin M Tomaszewski J Werner-Zwanziger U Zwanziger JW 《Langmuir : the ACS journal of surfaces and colloids》2004,20(4):1100-1110
Polymer colloids with internal ordering were synthesized using hydrolytic condensation of octadecyl-dimethyl(3-trimethoxysilylpropyl)ammonium chloride (ODMACl) and a mixture of ODMACl and the trisodium salt of the triacetic acid N-(trimethoxysilylpropyl)ethylenediamine (TANED). The structure and morphology of these colloids were studied with small-angle X-ray scattering, transmission electron microscopy, nuclear magnetic resonance, sedimentation in ultracentrifuge; and other methods. When polymer colloids are obtained from a single precursor (ODMACl), their local structure, molecular weight characteristics, and morphology strongly depend on the reaction conditions, while lamellar ordering remains nearly unaffected. Use of a mixture of cationic and anionic silanes (ODMACl and TANED) as precursors in hydrolytic condensation results in novel zwitterionic copolymer colloids with two-dimensional hexagonal packing. Interaction of the ODMACl quaternary ammonium groups with the three carboxy groups of TANED leads to replacement of sodium and chloride ions and formation of gegenions, resulting in a molar ratio ODMACl:TANED = 3:1 (each TANED molecule contains three carboxy groups). Due to their ordered interior, polyODMACl (PODMACl) and PODMACl-TANED colloids can be used as templates for controlled positioning of nanoparticles within these colloids. For example, lamellar ordering controls Pt nanoparticle formation within PODMACl colloids providing Pt nanoparticle alignment within the lamellar structure. Loading of PODMACl-TANED colloids with iron salts followed by pH increase results in the formation of iron oxide nanoparticles located within PODMACl-TANED cylinders. 相似文献
105.
Timofeeva M. N. Matrosova M. M. Il'inich G. N. Reshetenko T. V. Avdeeva L. B. Kvon R. I. Chuvilin A. L. Budneva A. A. Paukshtis E. A. Likholobov V. A. 《Kinetics and Catalysis》2003,44(6):778-787
The adsorption of H3PW12O40 (HPA) from methanol solutions on mesoporous carbon supports (multiwall carbon nanotubes (CFC-3) and CFC modified with nitrogen atoms (N-CFC)) was studied. It was found that up to 10 wt % HPA was irreversibly adsorbed on the surface of CFC. This character of adsorption is indicative of the strong interaction of the adsorbate (HPA molecules) with coal surface groups (carboxylic, lactone, etc.) to form intermolecular hydrogen bonds with -electron interactions. It was found that N-containing surface centers affected the adsorption of HPA on N-CFC. The acid and catalytic properties of HPA/CFC systems in the esterification reaction of n-butanol with acetic acid were studied ([BuOH]/[HOAc] = 1 : 15 mol/mol; 80°C). It was found that the strength of proton centers, which was determined as proton affinity, decreased upon supporting HPA. The HPA/CFC-3 systems most actively catalyzed the reaction. The catalytic activity of HPA/N-CFC depended on the nature of N-containing groups at the support surface, and it decreased with concentration of pyridine-like structures. 相似文献
106.
Barlow S Risko C Coropceanu V Tucker NM Jones SC Levi Z Khrustalev VN Antipin MY Kinnibrugh TL Timofeeva T Marder SR Brédas JL 《Chemical communications (Cambridge, England)》2005,(6):764-766
The E-4,4'-bis[di(p-anisyl)amino]stilbene cation is a class-III mixed-valence species with electronic coupling comparable to that in its biphenyl-bridged analogue, whereas its tolane-bridged analogue belongs to class II. 相似文献
107.
I. V. Kozhevnikov A. I. Tsyganok M. N. Timofeeva S. M. Kulikov V. N. Sidelnikov 《Reaction Kinetics and Catalysis Letters》1992,46(1):17-23
Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H3PW12O40 and 25% H3PW12O40/SiO2 at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H2SO4, easily separated from the reaction mixture and can be used repeatedly. -- () - () H3PW12O40 25% H3PW12O40/SiO2 100–150°C - - . , H2SO4, - - . 相似文献
108.
Badaeva EA Timofeeva TV Masunov A Tretiak S 《The journal of physical chemistry. A》2005,109(32):7276-7284
Time-dependent density functional theory (TD-DFT) is applied to model one-photon (OPA) and two-photon (TPA) absorption spectra in a series of conjugated cytotoxic dyes. Good agreement with available experimental data is found for calculated excitation energies and cross sections. Calculations show that both OPA and TPA spectra in the molecules studied are typically dominated by two strong peaks corresponding to different electronic states. We find that donor-acceptor strengths and conjugated bridge length have a strong impact on the cross-section magnitudes of low- and high-frequency TPA maxima, respectively. These trends are analyzed in terms of the natural transition orbitals of the corresponding electronic states. Observed structure-property relationships may have useful implications on design of organic conjugated chromophores with tunable two-photon absorption properties for photodynamic therapy applications. 相似文献
109.
V. A. Davankov G. I. Timofeeva M. M. Ilyin M. P. Tsyurupa 《Journal of polymer science. Part A, Polymer chemistry》1997,35(17):3847-3852
Atactic polystyrene of M = 330,000 Da and Mw/Mn = 1.04 was subjected to chloromethylation. By the heating of chloromethylpolystyrene with SnCl4 in a very dilute solution in ethylene dichloride, the polymeric coils were converted into intramolecularly hypercrosslinked macromolecules, nanosponges, of molecular weight of about 370,000 Da and a diameter of about 17 nm. When in solution, the nanosponges tend to reversibly self-assemble into regular clusters. Size exclusion chromatography and sedimentation analysis corroborate the suggestion that the clusters consist of 13 spherical subunits and thus acquire a molecular weight of about 5.0 × 106 Da and a diameter of about 45 nm. © John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3847–3852, 1997 相似文献
110.
Boris B. Averkiev Mikhail Yu. Antipin Aleksey B. Sheremetev Tatiana V. Timofeeva 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):o383-o387
In earlier papers, we described the synthesis and structures of bis(3‐nitrofurazan‐4‐yl) ether, C4N6O7, (I), bis[3‐(nitro‐N,N,O‐azoxy)furazan‐4‐yl] ether, C4N10O9, (II), and bis[3‐(5H‐[1,2,3]triazolo[4,5‐c]furazan‐5‐yl)furazan‐4‐yl] ether, C8N14O5, (III). Here we compare the structures of (I)–(III) with those of four 3‐cyanodifurazanyl ethers, namely bis(3‐cyanofurazan‐4‐yl) ether, C6N6O3, (IV), 3‐cyanofurazanyl 3‐nitrofurazanyl ether, C5N6O5, (V), 3,4‐bis(3‐cyanofurazan‐4‐yloxy)furazan, C8N8O5, (VI), and bis[3‐(3‐cyanofurazan‐4‐yloxy)furazan‐4‐yl]diazene, C10N12O6, (VII). It was found that the geometric parameters of the difurazanyl ether fragments are similar in these structures and therefore not influenced by substituent effects; however, the conformation of this fragment is different, viz. structures (I), (III), (V) and (VI) have approximate C2 symmetry, and structures (II), (IV) and (VII) have Cs symmetry. Dense crystal packing (1.626–1.898 Mg m−3) is characteristic for all these hydrogen‐free compounds. A linear correlation is also determined between crystal density and `molecular density' (M/V), where M is the mass of a molecule and V is the molecular volume. 相似文献