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101.
Seebauer EG Dev K Jung MY Vaidyanathan R Kwok CT Ager JW Haller EE Braatz RD 《Physical review letters》2006,97(5):055503
The technologically useful properties of a crystalline solid depend upon the concentration of defects it contains. Here we show that defect concentrations as deep as 0.5 microm within a semiconductor can be profoundly influenced by gas adsorption. Self-diffusion rates within silicon show that nitrogen atoms adsorbed at less than 1% of a monolayer lead to defect concentrations that vary controllably over several orders of magnitude. The results show that previous measurements of diffusion and defect thermodynamics in semiconductors may have suffered from neglect of adsorption effects. 相似文献
102.
Interactions between short strands of DNA can be tuned from repulsive to attractive by varying solution conditions and have been quantified using small angle x-ray scattering techniques. The effective DNA interaction charge was extracted by fitting the scattering profiles with the generalized one-component method and inter-DNA Yukawa pair potentials. A significant charge is measured at low to moderate monovalent counterion concentrations, resulting in strong inter-DNA repulsion. The charge and repulsion diminish rapidly upon the addition of divalent counterions. An intriguing short range attraction is observed at surprisingly low divalent cation concentrations, approximately 16 mM Mg2+. Quantitative measurements of inter-DNA potentials are essential for improving models of fundamental interactions in biological systems. 相似文献
103.
Analysis of a bi-piezoelectric ceramic layer with an interfacial crack subjected to anti-plane shear and in-plane electric loading 总被引:1,自引:0,他引:1
The behaviour of a bi-piezoelectric ceramic layer with a centre interfacial crack subjected to anti-plane shear and in-plane electric loading has been studied. The dislocation density functions and the Fourier integral transform method have been employed to eliminate the problem of singular integral equations. The normalized energy release rate, stress and electrical displacement intensity factors, G/G0,KIII/KIII0 and KD/KD0, respectively, were determined for different geometric and property parameters by use of two different crack surface electric boundary conditions, i.e. impermeable and permeable. It has been shown that the effects of the thickness and material constants of the piezoelectric layer on all the three parameters, i.e. G/G0,KIII/KIII0 and KD/KD0 were significant. 相似文献
104.
A method for the measurement of arbitrary pretilt angles in liquid crystal displays is proposed and demonstrated. The cell gap can also be determined accurately in the same experiment as well. This method makes use of a photo-elastic modulator and is capable of measuring pretilt angles from 0 to 90deg precisely. 相似文献
105.
Inhibitory activity and conformation changes of soybean trypsin inhibitors induced by ultrasound 总被引:1,自引:0,他引:1
The inhibitory activities, sulfhydryl bonds and far-UV circular dichroism (CD) spectra of Kunitz and Bowman–Birk soybean trypsin inhibitors (KTI and BBTI) were measured before and after ultrasound treatments. The differences between KTI and BBTI in conformation changes and resistance to ultrasound were observed. The secondary structures of KTI were found to be composed of β-sheet (22.5%), β-turn (16.2%) and random coils (61.4%) while that of BBTI composed of only β-sheet (52.6%) and random coils (47.4%). KTI lost its inhibitory activity more quickly than BBTI, proportionally to the ultrasound amplitudes and sonication durations used. Relevant synchronous phenomena observed included the inactivation of KTI, significant rise in sulfhydryl content and corresponding conformation changes, in which there were dramatic decreases in both β-turn and random coil contents and increase in the β-sheet structure over the entire sonication duration and ultrasonic amplitude scale used by the study. Ultrasound affected the activities and conformations of KTI and BBTI by exerting an influence on their disulfide bonds. For KTI, up to 55% of inhibitory activity could be inactivated, at which about 71.5% of disulfide bonds were altered and the [θ]200nm value was changed from native −2545 deg cm2 dmol−1 to −1827 deg cm2 dmol−1. Whereas for BBTI, far-UV CD spectra, β-sheet and random structures were barely affected, only about 5.29% of disulfide bonds were found altered and the [θ]200nm value was changed only from native −797 deg cm2 dmol−1 to −700 deg cm2 dmol−1. It is concluded that ultrasound inactivates KTI by inducing a reduction in the disulfide bonds and then changes the conformations. 相似文献
106.
Hu Rong Chen Xu Zhou Taotao Si Han He Benzhao Kwok Ryan T. K. Qin Anjun Tang Ben Zhong 《中国科学:化学(英文版)》2019,62(9):1198-1203
Unnatural reaction in the living cells is a powerful tool for biological research. However, the polymerization inside cells is rarely reported. In this work, a lab-in-cell is illustrated based on our developed spontaneous amino-yne click polymerization. Carbonyl group activated terminal diyne can spontaneously polymerize with tetraphenylethene(TPE)-containing primary diamine inside cells, and polymer with weight-average molecular weight of 7,300 was yielded. By utilizing this in vivo amino-yne click polymerization and taking advantage of the aggregation-induced emission feature of TPE, a "turn-on" cell imaging was realized,and in-situ killing of cells was also acquired by destroying the structures of actin and tubulin, which cannot be realized by preprepared polymer. This strategy provides a useful platform and holds great promise in biochemistry and therapy applications. 相似文献
107.
A ray model is developed and validated for prediction of the insertion loss of hard parallel noise barriers placed in an urban environment either in front of a row of tall buildings or in a street canyon. The model is based on the theory of geometrical acoustics for sound diffraction at the edge of a barrier and multiple reflections by the ground, barrier and fa?ade surfaces. It is crucial to include the diffraction and multiple reflection effects in the ray model as they play important roles in determining the overall sound pressure levels for receivers located between the fa?ade and the near-side barrier. Comparisons of the ray model with a wave-based boundary element formulation show reasonably good agreement over a broad frequency range. Results of scale model experimental studies are also presented. It is demonstrated that the ray model agrees tolerably well with the scale model experimental data. 相似文献
108.
Hua J Xiao ZL Imre A Yu SH Patel U Ocola LE Divan R Koshelev A Pearson J Welp U Kwok WK 《Physical review letters》2008,101(7):077003
We investigated confinement effects on the resistive anisotropy of a superconducting niobium strip with a rectangular cross section. When its transverse dimensions are comparable to the superconducting coherence length, the angle dependent magnetoresistances at a fixed temperature can be scaled as R(theta,H) = R(H/Hctheta) where Hctheta =Hc0(cos2theta + gamma(-2)sin2theta)(-1/2) is the angular dependent critical field, gamma is the width to thickness ratio, and Hc0 is the critical field in the thickness direction at theta=0 degrees . The results can be understood in terms of the anisotropic diamagnetic energy for a given field in a one-dimensional superconductor. 相似文献
109.
A Substitution‐Dependent Light‐Up Fluorescence Probe for Selectively Detecting Fe3+ Ions and Its Cell Imaging Application 下载免费PDF全文
Xing Feng Ying Li Xuewen He Haixiang Liu Zheng Zhao Ryan T. K. Kwok Mark R. J. Elsegood Jacky W. Y. Lam Ben Zhong Tang 《Advanced functional materials》2018,28(35)
Deliberate design of specific and sensitive molecular probes with distinctive physical/chemical properties for analyte sensing is of great significance. Herein, by taking advantage of the position‐dependent substituent effects, an aggregation‐induced emission featured iron (III) probe from ortho‐substituted pyridinyl‐functionalized tetraphenylethylene (TPE‐o‐Py) is synthesized. It displays high sensitivity and selectivity toward iron (III) detection. The recognition arises from the position isomer of ortho‐substitution, and the fact that TPE‐o‐Py has a low acid dissociation constant (pK a) that is close to that of hydrolyzed Fe3+. Importantly, TPE‐o‐Py as a light‐up fluorescence probe could be employed for Fe3+ sensing in living cells with a pronounced red‐shift in fluorescence emission. 相似文献
110.