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51.
Alexei S. Komolov Eleonora F. Lazneva Svetlana N. Akhremtchik 《Applied Surface Science》2010,256(8):2419-2422
Ultrathin conjugated layers of Pyronine B were thermally deposited in UHV on the surface of perylene tetracarboxylic acid dianhydride (PTCDA) film. The structure of unoccupied electron states located 5-20 eV above the Fermi level (EF) and the surface potential were monitored during the Pyronine B overlayer deposition, using an incident beam of low-energy electrons according to the total current electron spectroscopy (TCS) method. Electronic work function of the PTCDA surface changed from 4.9 ± 0.1 eV, during the Pyronine B deposition due to the change of the contents of the surface layer, until it reached a stable value 4.6 ± 0.1 eV at the Pyronine B film thickness 8-10 nm. The interface dipole corresponds to electron transfer from the Pyronine B overlayer to the PTCDA surface and the polarization in the Pyronine B overlayer was found confined within approximately 1 nm near the interfaces. The edges of major bands of density of unoccupied electronic states (DOUS) of PTCDA substrate and of the Pyronine B overlayer were unaffected by the process of the interface formation. The major TCS spectral features of the Pyronine B film corresponding to the DOUS band edges were identified and the assignment of the π*, σ*(C-C) and σ*(CC) character was suggested. 相似文献
52.
Svetlana V. Kirpichenko Bagrat A. Shainyan Erich Kleinpeter 《Journal of Physical Organic Chemistry》2012,25(12):1321-1327
The conformational analysis of the first representative of the Si‐alkoxy substituted six‐membered Si,N‐heterocycles, 1,3‐dimethyl‐3‐isopropoxy‐3‐silapiperidine, was performed by low‐temperature 1H and 13C NMR spectroscopy and DFT theoretical calculations. In contrast to the expectations from the conformational energies of methyl and alkoxy substituents, the Meaxi‐PrOeq conformer was found to predominate in the conformational equilibrium in the ratio Meaxi‐PrOeq : Meeqi‐PrOax of ca. 2 : 1 as from the 1H and 13C NMR study. The thermodynamic parameters obtained by the complete line shape analysis showed that the main contribution to the barrier to ring inversion originates from the entropy term of the free energy of activation. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
53.
Vijay Singh R.P.S. Chakradhar Isabelle Ledoux-Rak Laurent Badie Fabienne Pelle Svetlana Ivanova 《Journal of luminescence》2009,129(11):1375-1380
New near-infrared luminescent, monoclinic CaAl2O4:Er3+ phosphor was prepared by using the combustion route at furnace temperatures as low as 500 °C in a few minutes. Combustion synthesized phosphor has been well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) mapping studies. The luminescence spectra of Er3+-doped calcium aluminate were studied at UV (380 nm), vis (488 nm) and IR (980 nm) excitation. Upon UV and vis excitation, the CaAl2O4:Er3+ phosphor exhibits emission bands at ~523 nm and at ~547 nm, corresponding to transitions from the 2H11/2 and 4S3/2 erbium levels to the 4I15/2 ground state. A strong luminescence at 1.55 μm in the infrared (IR) region due to 4I13/2→4I15/2 transition has been observed in CaAl2O4:Er3+ phosphor upon 980 nm CW pumping. In the spectrum of IR-excited up-conversion luminescence, green (~523 and ~547 nm) and red (662 nm) luminescence bands were present, the latter associated with the 4F9/2→4I15/2 transitions of Er3+ ions. Both excited state absorption and energy transfer may be proposed as processes responsible for the population of the 4S3/2 and 4F9/2 erbium levels upon IR excitation. The mechanisms responsible for the up-conversion luminescence are discussed. 相似文献
54.
Svetlana Boyarchenko 《Applied Mathematical Finance》2013,20(1):26-49
Abstract We consider the Heston model with the stochastic interest rate of Cox–Ingersoll–Ross (CIR) type and more general models with stochastic volatility and interest rates depending on two CIR-factors; the price, volatility and interest rate may correlate. Time-derivative and infinitesimal generator of the process for factors that determine the dynamics of the interest rate and/or volatility are discretized. The result is a sequence of embedded perpetual options arising in the time discretization of a Markov-modulated Lévy model. Options in this sequence are solved using an iteration method based on the Wiener–Hopf factorization. Typical shapes of the early exercise boundary are shown, and good agreement of option prices with prices calculated with the Longstaff–Schwartz method and Medvedev–Scaillet asymptotic method is demonstrated. 相似文献
55.
Yulya N. Biglova Rauilya N. Malikova Svetlana F. Petrova Sergey P. Ivanov Ilshat M. Sakhautdinov Akhat G. Mustafin 《国际化学动力学杂志》2019,51(5):311-320
The kinetics of nucleophilic fullerene cyclopropanation by halomethyl ketones with a diterpene fragment has been studied by the Bingel method, and the influence of the biologically active cyclopropanating agent on the process has been estimated. It has been revealed that favorable conditions for carrying out the reaction result in maximum monofunctionalized methanofullerenes formation with the maximum yield. 相似文献
56.
Maxim V. Musalov Vladimir A. Potapov Vladimir A. Yakimov Maria V. Musalova Arkady A. Maylyan Sergey V. Zinchenko Svetlana V. Amosova 《Molecules (Basel, Switzerland)》2021,26(12)
The regioselective synthesis of novel functionalized condensed organochalcogen compounds by chalcogenocyclofunctionalization reactions based on chalcogen halides and the natural products thymol and carvacrol has been developed. The reactions of selenium dibromide with allyl thymol and allyl carvacrol proceeded in methylene chloride at room temperature in the presence of NaHCO3 affording bis[(7-isopropyl-4-methyl-2,3-dihydro-1-benzofuran-2-yl)methyl] and bis[(4-isopropyl-7-methyl-2,3-dihydro-1-benzofuran-2-yl)methyl] selenides in 90–92% yield. Similar sulfides were obtained in 70–72% yields by the reaction of sulfur dichloride in chloroform under reflux. Trihalotellanes containing the same organic moieties were synthesized from allyl thymol, allyl carvacrol and tellurium tetrachloride or tetrabromide in quantitative yields. Corresponding functionalized ditellurides were prepared in 91–92% yields by the reduction of the trichlorotellanes with sodium metabisulfite in two-phase solvent system. The comparison of reactivity of sulfur, selenium and tellurium halides in chalcogenocyclofunctionalization and distinguishing features of each reaction were discussed. 相似文献
57.
Fernanda das Neves Costa Gerold Jerz Peter Hewitson Fabiana de Souza Figueiredo Svetlana Ignatova 《Molecules (Basel, Switzerland)》2021,26(8)
The detailed metabolite profiling of Laguncularia racemosa was accomplished by high-performance countercurrent chromatography (HPCCC) using the three-phase system n-hexane–tert-butyl methyl ether–acetonitrile–water 2:3:3:2 (v/v/v/v) in step-gradient elution mode. The gradient elution was adjusted to the chemical complexity of the L. racemosa ethyl acetate partition and strongly improved the polarity range of chromatography. The three-phase solvent system was chosen for the gradient to avoid equilibrium problems when changing mobile phase compositions encountered between the gradient steps. The tentative recognition of metabolites including the identification of novel ones was possible due to the off-line injection of fractions to electrospray ionization mass spectrometry (ESI-MS/MS) in the sequence of recovery. The off-line hyphenation profiling experiment of HPCCC and ESI-MS projected the preparative elution by selected single ion traces in the negative ionization mode. Co-elution effects were monitored and MS/MS fragmentation data of more than 100 substances were used for structural characterization and identification. The metabolite profile in the L. racemosa extract comprised flavonoids, hydrolysable tannins, condensed tannins and low molecular weight polyphenols. 相似文献
58.
Carlos Bornes Dr. Dusan Stosic Prof. Dr. Carlos F. G. C. Geraldes Prof. Dr. Svetlana Mintova Prof. Dr. João Rocha Dr. Luís Mafra 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(64):e202201795
The identification of acid and nonacid species at the external surface of zeolites remains a major challenge, in contrast to the extensively-studied internal acid sites. Here, it is shown that the synthesis of zeolite ZSM-5 samples with distinct particle sizes, combined with solid-state NMR and computational studies of trimethylphosphine oxide (TMPO) adsorption, provides insight into the chemical species on the external surface of the zeolite crystals. 1H–31P HETCOR NMR spectra of TMPO-loaded zeolites exhibit a broad correlation peak at δP ∼35–55 ppm and δH ∼5–12 ppm assigned to external SiOH species. Pore-mouth Brønsted acid sites exhibit 31P and 1H NMR resonances and adsorption energies close to those reported for internal acid sites interacting with TMPO. The presence of an external tricoordinate Al-Lewis site interacting strongly with TMPO is suggested, resulting in 31P resonances that overlap with the peaks usually ascribed to the interaction of TMPO with Brønsted sites. 相似文献
59.
Elena V. Suprun Svetlana A. Khmeleva Yana Y. Kiseleva Sergey P. Radko Alexander I. Archakov Victoria V. Shumyantseva 《Electroanalysis》2016,28(9):1977-1983
The tyrosine based electrochemical analysis of synthetic amyloid‐β (Aβ) peptide – an analog of natural peptide implicated in Alzheimer's disease pathogenesis – was applied for a quantitative estimation of peptide aggregation in vitro. The analysis was carried out by square wave voltammetry (SWV) on carbon screen printed electrodes (SPE). The electrooxidation peak current (Ip) for Aβ42 peptide in different aggregation states was directly compared with the size and structure of Aβ42 aggregates occurring in the analyzed sample. Dynamic light scattering (DLS) and thioflavin T (ThT) based fluorescence assay were employed to estimate the size and structure of Aβ42 aggregates. The Ip was found to decrease in a linear fashion when the average diameter of aggregates and the relative ThT fluorescence in Aβ42 solutions exceeded 35 nm and 3, respectively, while being nearly constant below these values. It was suggested that the electrooxidation current is mostly generated by peptide monomers and that a depletion of the monomer pool due to inclusion of Aβ42 molecules in aggregates is responsible for the decrease of electrooxidation current. The direct electrochemistry is emerging as a method complementary to methods based on aggregates’ detection and commonly employed for monitoring Aβ aggregation. The work further enlarges the basis for application of the cost‐effective and rapid electrochemical techniques, such as SWV on carbon SPE, to in vitro studies of Aβ aggregation. 相似文献
60.
Magnetically and Near‐Infrared Light‐Powered Supramolecular Nanotransporters for the Remote Control of Enzymatic Reactions 下载免费PDF全文
Dr. Svetlana A. Chechetka Dr. Eiji Yuba Prof. Kenji Kono Dr. Masako Yudasaka Dr. Alberto Bianco Dr. Eijiro Miyako 《Angewandte Chemie (International ed. in English)》2016,55(22):6476-6481
Cancer is one of the primary causes of death worldwide. A high‐precision analysis of biomolecular behaviors in cancer cells at the single‐cell level and more effective cancer therapies are urgently required. Here, we describe the development of a magnetically‐ and near infrared light‐triggered optical control method, based on nanorobotics, for the analyses of cellular functions. A new type of nanotransporters, composed of magnetic iron nanoparticles, carbon nanohorns, and liposomes, was synthesized for the spatiotemporal control of cellular functions in cells and mice. Our technology will help to create a new state‐of‐the‐art tool for the comprehensive analysis of “real” biological molecular information at the single‐cell level, and it may also help in the development of innovative cancer therapies. 相似文献