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71.
72.
The synthesis of the retinoid skeleton has been exhaustively explored using the Stille coupling for the formation of the side-chain single bonds. On employing the experimental catalytic conditions developed by Farina [Pd2(dba)3, AsPh3, NMP] we have modified the electronic and steric requirement of the coupling parters, alkenyl stannanes and electrophiles (alkenyl iodides and triflates). The comprehensive survey afforded appropriately matched components for every bond formation considered. Moreover, from the comparison of the reactivities of different coupling partners with different degrees of steric hindrance, the sensitivity of the Stille coupling to steric effects was confirmed. Besides providing a variety of building blocks for retinoid synthesis, the study highlights some trends that might be useful for the application of the Stille reaction to the synthesis of unsubstituted conjugated polyenes. 相似文献
73.
74.
Juan‐José Cid Dr. Miguel García‐Iglesias Jun‐Ho Yum Dr. Amparo Forneli Josep Albero Eugenia Martínez‐Ferrero Dr. Purificación Vázquez Prof. Michael Grätzel Prof. Mohammad K. Nazeeruddin Prof. Emilio Palomares Prof. Tomás Torres Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(20):5130-5137
Let it shine! The impact of the anchoring group on photovoltaic performance by a series of phthalocyanine sensitisers (see figure) has been demonstrated.
75.
A semi-analytic model is developed to estimate continuum lowering in dense plasmas including fluctuations. The model is applied to aluminum and compared with recent experiments at the Linac Coherent Light Source [O. Ciricosta et al., Phys. Rev. Lett. 109 (2012) 065002] that reported the ionization potential depression of K-shell electrons in solid density aluminum at temperatures up to 180 eV. The analysis suggests fluctuations, which are neglected in most continuum lowering models but are essential to describe energy absorption by a system, are sufficiently large to impact the interpretation of the experimental results. 相似文献
76.
Carlos A. Iglesias 《High Energy Density Physics》2012,8(3):260-265
The partially resolved transition array (PRTA) model is developed for intermediate coupling. The PRTA model conserves known array properties, yields improved higher moments, systematically accounts for initial level populations, and is computationally efficient compared to detailed line accounting (DLA) methods. Numerical examples show that the PRTA in intermediate coupling reproduces the effects of the electrostatic interaction between spin-orbit split arrays on the spectrum in good agreement with DLA calculations. 相似文献
77.
为实现三维光存储中折射率失配引起的球差补偿,建立了光学存储系统模型,获得了折射率失配引起的波前偏差函数与存储深度的表达式.采用泽尔尼克循环多项式对波前偏差函数进行补偿展开.在双光子荧光和单光子共焦荧光读出方式下,均可获得读出荧光强度与存储深度的关系:在折射率失配引起的球差未得到补偿矫正的情况下,存储深度在200 μm左右读出荧光强度基本上下降为零;当折射率失配引起的初级球差被补偿矫正后,读出荧光强度随存储深度的下降得到较好改善;当折射率失配引起的二级球差被补偿矫正后,存储深度在1 mm内存储点强度随深度基本上没有明显地变化.并且对像差补偿方法进行了具体地分析. 相似文献
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79.
Ricardo Ferreira Affeldt Rodrigo Sebastian Iglesias Fabiano Severo Rodembusch Dennis Russowsky 《Journal of Physical Organic Chemistry》2012,25(9):769-777
In this article, a series of Hantzsch 1,4‐dihydropyridines with different substituted aryl groups were synthesized and its spectral data obtained by UV–Vis absorption and fluorescence emission spectroscopies in solution. The dihydropyridines present absorption located around 350 nm and fluorescence emission in the blue–green region. A higher Stokes’ shift could be observed for the derivative 3b because of an intramolecular charge transfer in the excited state from the dimethylaniline to the dihydropyridine chromophores, which was corroborated by a linear relation of the fluorescence maxima (νmax) versus the solvent polarity function (Δf) from the Lippert–Mataga correlation. A comparison between the experimental data and time‐dependent density functional theory‐polarizable continuum model calculations of the vertical transitions was performed to help on the elucidation of the photophysics of these compounds. For these calculations, the S0 and S1 states were optimized using Becke, three‐parameter, Lee–Yang–Parr/6‐31 G* and Configuration Interaction Singles/6‐31 G*, respectively. The predicted absorption maxima are in good agreement with the experimental; however, the theoretical fluorescence emission maxima do not match the experimental, which means that the excited specie cannot be related to neither a locally excited state nor to an aromatized structure. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
80.
S. Gon?alves M. F. Laguna J. R. Iglesias 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(6):1-9
Structural and dielectric properties of Potassium Lithium Niobate polycrystalline ceramic K3Li2Nb5O15 (KLN), having the tetragonal tungsten bronze (TTB) ?C type structure are studied in the temperature interval 50?550?°C. Special emphasis is given to the diffuse phase transition occurring around 440?°C. Space charge polarization, relaxation phenomena and free charge conductivity have been elucidated using impedance spectroscopy technique. Argand plots have revealed a non Debye and polydispersive type relaxation. In paraelectric phase the Arrhenius activation energy E ?? ?=?0.533?eV was determined. The structural and dielectric results are compared with two others TTB compounds derived from KLN family: Pb1.85K1.15Li0.15Nb5O15 (PKLN) and GdK2Nb5O15 (GKN). 相似文献