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101.
Chinh Tam Le Daniel J. Clark Farman Ullah Velusamy Senthilkumar Joon I. Jang Yumin Sim Maeng‐Je Seong Koo‐Hyun Chung Hyoyeol Park Yong Soo Kim 《Annalen der Physik》2016,528(7-8):551-559
In this study, we utilized picosecond pulses from an Nd:YAG laser to investigate the nonlinear optical characteristics of monolayer MoSe2. Two‐step growth involving the selenization of pulsed‐laser‐deposited MoO3 film was employed to yield the MoSe2 monolayer on a SiO2/Si substrate. Raman scattering, photoluminescence (PL) spectroscopy, and atomic force microscopy verified the high optical quality of the monolayer. The second‐order susceptibility χ(2) was calculated to be ~50 pm V?1 at the second harmonic wavelength ~810 nm, which is near the optical gap of the monolayer. Interestingly, our wavelength‐dependent second harmonic scan can identify the bound excitonic states including negatively charged excitons much more efficiently, compared with the PL method at room temperature. Additionally, the MoSe2 monolayer exhibits a strong laser‐induced damage threshold ~16 GW cm?2 under picosecond‐pulse excitation. Our findings suggest that monolayer MoSe2 can be considered as a promising candidate for high‐power, thin‐film‐based nonlinear optical devices and applications. 相似文献
102.
Yoon HJ Kim YW Lee BK Lee WK Kim Y Ha HJ 《Chemical communications (Cambridge, England)》2007,(1):79-81
An efficient and highly stereoselective synthesis of D-ribo-(2S,3S,4R)-phytosphingosine was accomplished in 62% overall yield starting from commercially available (2S)-hydroxymethylaziridine via osmium-catalyzed asymmetric dihydroxylation as a key step. 相似文献
103.
Yongkwan Dong Hoseop Yun Chan Sun Park Won Koo Lee Hyun‐Joon Ha 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(12):o659-o660
In the title compound, C13H14BN3O, the aziridine ring is an almost equilateral triangle, the C—C distance being slightly shorter than the C—N distances, probably because of the dative B—N bond. The five‐membered ring, composed of two C atoms and N, B and O atoms, is fused with the aziridine ring to form a six‐membered ring with a chair conformation. 相似文献
104.
105.
Jin Koo Kim Sun Young Jeong Sae Hoon Lim Jang Hyeok Oh Seung‐Keun Park Jung Sang Cho Yun Chan Kang 《化学:亚洲杂志》2019,14(18):3127-3140
Increasing demand for sodium‐ion batteries (SIBs), one of the most feasible alternatives to lithium ion batteries (LIBs), has resulted because of their high energy density, low cost, and excellent cycling stability. Consequently, the design and fabrication of suitable electrode materials that govern the overall performance of SIBs are important. Aerosol‐assisted spray processes have gained recent prominence as feasible, scalable, and cost‐effective methods for preparing electrode materials. Herein, recent advances in aerosol‐assisted spray processes for the fabrication of nanostructured metal chalcogenides (e.g., metal sulfides, selenides, and tellurides) for SIBs, with a focus on improving the electrochemical performance of metal chalcogenides, are summarized. Finally, the improvements, limitations, and direction of future research into aerosol‐assisted spray processes for the fabrication of various electrode materials are presented. 相似文献
106.
107.
T. William Bentley Robert O. Jones Dae Ho Kang In Sun Koo 《Journal of Physical Organic Chemistry》2009,22(9):799-806
Rate constants for a wide range of binary aqueous mixtures and product selectivities (S) in ethanol–water (EW) and methanol–water (MW) mixtures, are reported at 25 °C for solvolyses of benzenesulfonyl chloride and the 4‐chloro‐derivative. S is defined as follows using molar concentrations: S = ([ester product]/[acid product]) × ([water solvent]/[alcohol solvent]). Additional selectivity data are reported for solvolyses of 4‐Z‐substituted sulfonyl chlorides (Z = OMe, Me, H, Cl and NO2) in 2,2,2‐trifluoroethanol–water. To explain these results and previously published data on kinetic solvent isotope effects (KSIEs) and on other solvolyses of 4‐nitro and 4‐methoxybenzenesulfonyl chloride, a mechanistic spectrum involving a change from third order to second order is proposed. The molecularity of these reactions is discussed, along with new term ‘SN3–SN2 spectrum’ and its connection with the better established term ‘SN2–SN1 spectrum’. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
108.
The capacitance characteristics of platinum nanoparticle (NP)-embedded metal–oxide–semiconductor (MOS) capacitors with gate Al2O3 layers are studied in this work. The capacitance versus voltage (C–V) curves obtained for a representative MOS capacitor exhibit flat-band voltage shifts, demonstrating the presence of charge storages in the platinum NPs. The counterclockwise hysteresis and flat-band voltage shift, observed from the C–V curves imply that electrons are stored in a floating gate layer consisting of the platinum NPs present between the tunneling and control oxide layers in the MOS capacitor and that these stored electrons originate from the Si substrate. Moreover, the charge remains versus time curve for the platinum NP-embedded MOS capacitor is investigated in this work. 相似文献
109.
Hyun-Joo Koo 《Solid State Communications》2009,149(21-22):847-851
The magnetic properties of Ag2V OP2O7 were examined by evaluating its spin exchange interactions in terms of spin dimer analysis based on tight binding calculations and mapping analysis based on first principles density functional theory calculations. Both calculations show that a strong spin exchange interaction occurs through the super-superexchange path J1 with the V…V distance of 5.293 Å. This strong antiferromagnetic interaction forms isolated spin dimer units, which are coupled antiferromagnetically by the spin exchange path J3 to form a two-leg spin ladder that has no spin frustration. The inter–dimer interaction J2 is found to be ferromagnetic, and does not lead to spin frustration. 相似文献
110.
T. -K. Hong B. -H. Koo S. -Y. Ly M. -H. Kim M. -Z. Czae 《Journal of Analytical Chemistry》2009,64(11):1158-1165
A theoretical model for the potentiometric analysis of precipitation titrations using a pH electrode has been developed and
tested. The new analytical method is possible by introducing a mediator which must be a weak acid and must be able to form
an insoluble salt with a cation (a titrant). Theoretical expressions of pH, as well as the concentrations of all other species,
were derived and solved numerically using bisection method. Among the various factors that influence pH during the titration,
concentrations of the mediator and initial values of pH were proved to be very critical. The experimental potentiometric titration
curves agree well with those predicted from the theoretical model. Crossing point method was adopted to determine an equivalence
point from the titration curves. The method is tested using a known system of chloride determination. Among the several mediators
tested (bisulfite, chromate, phosphate, cyanide, arsenate and EDTA), phosphate yielded the best results with an error of 0.1%;
bisulfite, chromate and arsenate yielded comparably good results with an error of 0.3∼0.5%, but cyanide and EDTA yielded unsatisfactory
results. The optimum mediator concentration found to be in a range of 1–2 mM. 相似文献