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921.
Dayene M. Carvalho Jorge L. B. MacielJr. Leandro P. Ravaro Rogério E. Garcia Valdemir G. Ferreira Luis V. A. Scalvi 《Journal of Sol-Gel Science and Technology》2010,55(3):385-393
The fluid flow of the liquid phase in the sol-gel-dip-coating process for SnO2 thin film deposition is numerically simulated. This calculation yields useful information on the velocity distribution close
to the substrate, where the film is deposited. The fluid modeling is done by assuming Newtonian behavior, since the linear
relation between shear stress and velocity gradient is observed. Besides, very low viscosities are used. The fluid governing
equations are the Navier–Stokes in the two dimensional form, discretized by the finite difference technique. Results of optical
transmittance and X-ray diffraction on films obtained from colloidal suspensions with regular viscosity, confirm the substrate
base as the thickest part of the film, as inferred from the numerical simulation. In addition, as the viscosity increases,
the fluid acquires more uniform velocity distribution close to the substrate, leading to more homogenous and uniform films. 相似文献
922.
Artur Mardyukov Rachel Crespo‐Otero Dr. Elsa Sanchez‐Garcia Dr. Wolfram Sander Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(29):8679-8689
The reaction of the phenyl radical 1 with water has been investigated by using matrix isolation spectroscopy and quantum chemical calculations. The primary thermal product of the reaction between 1 and water is a weakly bound complex stabilized by an OH???π interaction. This complex is photolabile, and visible‐light irradiation (λ>420 nm) results in hydrogen atom transfer from water to radical 1 and the formation of a highly labile complex between benzene and the OH radical. This complex is stable under the conditions of matrix isolation, however, continuous irradiation with λ>420 nm light results in the complete destruction of the aromatic system and formation of an acylic unsaturated ketene. The mechanisms of all reaction steps are discussed in the light of ab initio and DFT calculations. 相似文献
923.
Tsz Kin Tam Marcos Pita Mikhail Motornov Ihor Tokarev Sergiy Minko Evgeny Katz 《Electroanalysis》2010,22(1):35-40
The modified electrode functionalized with a mixed‐polymer brush composed of poly(2‐vinylpyridine) and polyacrylic acid tethered to the surface demonstrated switchable interfacial properties discriminating negatively and positively charged redox species. The switchable electrochemical process was characterized by differential pulse voltammetry and Faradaic impedance spectroscopy. The electrochemical system was discussed as a model of an electrochemical multiplexer with two chemical redox inputs, the pH input operating as the selecting signal and one electronic output signal readable by the impedance spectroscopy in the form of the interfacial resistance. The modified electrode represents a novel component for integration with biocatalytic and biocomputing systems aiming at biochemically and electronically controlled actuators. 相似文献
924.
Poly(ethylene‐b‐ε‐caprolactone) (PE‐b‐PCL) diblock copolymers were synthesized by ring‐opening polymerization (ROP) of ε‐caprolactone (CL) with α‐hydroxyl‐ω‐methyl polyethylene (PE‐OH) as a macroinitiator and ammonium decamolybdate (NH4)8[Mo10O34] as a catalyst. Polymerization was conducted in bulk (130–150°C) with high yield (87–97%). Block copolymers with different compositions were obtained and characterized by 1H and 13C NMR, MALDI‐TOF, SAXS, and DSC. End‐group analysis by NMR and MALDI‐TOF indicates the formation of α‐hydroxyl‐ω‐methyl PE‐b‐PCL. The PE‐b‐PCL degradation was studied using thermogravimetric analysis (TGA) and alkaline hydrolysis. The PCL block was hydrolyzed by NaOH (4M), without any effect on the PE segment. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
925.
Wilkinson I Garcia IA Whitaker BJ Hamard JB Blanchet V 《Physical chemistry chemical physics : PCCP》2010,12(48):15766-15779
We present velocity map images of the NO, O((3)P(J)) and O((1)S(0)) photofragments from NO(2) excited in the range 7.6 to 9.0 eV. The molecule was initially pumped with a visible photon between 2.82-2.95 eV (440-420 nm), below the first dissociation threshold. A second ultraviolet laser with photon energies between 4.77 and 6.05 eV (260-205 nm) was used to pump high-lying excited states of neutral NO(2) and/or probe neutral photoproducts. Analysis of the kinetic energy release spectra revealed that the NO photofragments were predominantly formed in their ground electronic state with little kinetic energy. The O((3)P(J)) and O((1)S(0)) kinetic energy distributions were also dominated by kinetically 'cold' fragments. We discuss the possible excitation schemes and conclude that the unstable photoexcited states probed in the experiment were Rydberg states coupled to dissociative valence states. We compare our results with recent time-resolved studies using similar excitation and probe photon energies. 相似文献
926.
Moderate to good levels of substrate-based 1,5-syn-stereocontrol could be achieved in the boron-mediated aldol reactions of β-tert-butyl methylketones with achiral aldehydes, independent of the nature of the β-alkoxy protecting group (P = PMB or TBS). The analysis of the relative energies of the transition structures by theoretical calculations using the density functional B3LYP shows relative energies favoring the corresponding OUT-1,5-SYN transition structures, explaining the observed 1,5-syn stereoinduction. 相似文献
927.
Harb HY Collins KD Garcia Altur JV Bowker S Campbell L Procter DJ 《Organic letters》2010,12(23):5446-5449
The use of a silicon stereocontrol element in cyclobutanol and cyclopentanol-forming cyclizations mediated by SmI(2) results in excellent diastereocontrol. The C-Si bond in the products of cyclization provides a versatile handle for further manipulation. An asymmetric route to cyclization substrates involving copper-catalyzed silyl transfer has also been developed. 相似文献
928.
Ambient mass spectrometry: bringing MS into the “real world” 总被引:1,自引:0,他引:1
Rosana M. Alberici Rosineide C. Simas Gustavo B. Sanvido Wanderson Romão Priscila M. Lalli Mario Benassi Ildenize B. S. Cunha Marcos N. Eberlin 《Analytical and bioanalytical chemistry》2010,398(1):265-294
Mass spectrometry has recently undergone a second contemporary revolution with the introduction of a new group of desorption/ionization
(DI) techniques known collectively as ambient mass spectrometry. Performed in an open atmosphere directly on samples in their
natural environments or matrices, or by using auxiliary surfaces, ambient mass spectrometry (MS) has greatly simplified and
increased the speed of MS analysis. Since its debut in 2004 there has been explosive growth in the applications and variants
of ambient MS, and a very comprehensive set of techniques based on different desorption and ionization mechanisms is now available.
Most types of molecules with a large range of masses and polarities can be ionized with great ease and simplicity with the
outstanding combination of the speed, selectivity, and sensitivity of MS detection. This review describes and compares the
basis of ionization and the concepts of the most promising ambient MS techniques known to date and illustrates, via typical
analytical and bioanalytical applications, how ambient MS is helping to bring MS analysis deeper than ever into the “real
world” open atmosphere environment—to wherever MS is needed. 相似文献
929.
Filipe Camargo Dalmatti Alves Lima Rafael Rodrigues do Nascimento Marcos Brown Gon?alves Stefaan Cottenier Marília Junqueira Caldas Helena Maria Petrilli 《Hyperfine Interactions》2010,197(1-3):23-27
We compare published TDPAC experiments on 111Cd in the crown thioether C6H12S3AgCl with ab-initio electronic structure calculations performed within the framework of the Density Functional Theory using the Projector Augmented Wave method. We conclude from this comparison that the Cd atom at the very moment of the TDPAC experiment is positively charged, and we point out to a methodological difference between reproducing experimental electric-field gradients in molecules versus solid metals. 相似文献
930.
Sukesh Roy Paul J. Wrzesinski Dmitry Pestov Marcos Dantus James R. Gord 《Journal of Raman spectroscopy : JRS》2010,41(10):1194-1199
Coherent anti‐Stokes Raman scattering (CARS) spectroscopy of gas‐phase CO2 is demonstrated using a single femtosecond (fs) laser beam. A shaped ultrashort laser pulse with a transform‐limited temporal width of ∼7 fs and spectral bandwidth of ∼225 nm (∼3500 cm−1) is employed for simultaneous excitation of the CO2 Fermi dyads at ∼1285 and ∼1388 cm−1. CARS signal intensities for the two Raman transitions and their ratio as a function of pressure are presented. The signal‐to‐noise ratio of the single beam–generated CO2 CARS signal is sufficient to perform concentration measurements at a rate of 1 kHz. The implications of these experiments for measuring CO2 concentrations and rapid pressure fluctuations in hypersonic and detonation‐based chemically reacting flows are also discussed. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献