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101.
A series of Cs-phosphate glasses, xCs2O(1−x)P2O5, where 0?x?0.60, were prepared. The glass transition temperature (Tg) decreases with the initial addition of Cs2O to P2O5, from 637 K at x=0 to 472 K at x=0.16. There is little change in Tg with further additions of Cs2O up to x=0.60. The 31P magic angle spinning nuclear magnetic resonance (MAS NMR) spectra show that Cs2O additions systematically convert the cross-linked ultraphosphate network of ν-P2O5 to a chain-like metaphosphate structure as x approaches 0.50. The 133Cs MAS NMR spectra show a 90 ppm increase in isotropic chemical shift (δiso) with increasing Cs2O content, which indicates a decrease in the average electron density around the Cs+ ions, more covalent Cs-O bonding, and a shorter average Cs-O bond length. The physical properties and spectroscopic results are interpreted using a structural model that considers the effects of composition on the average coordination environment of Cs+ ions. 相似文献
102.
Daniel J. Williams Daniel Gulla Kimberly A. Arrowood Lindsey M. Bloodworth Angela L. Carmack Taylor J. Evers Mark S. Wilson Javier J. Concepcion Carol A. S. Brevett Benjamin E. Huck Donald VanDerveer 《Journal of chemical crystallography》2009,39(8):581-584
Abstract A new compound, [Cd(mipit)4][PF6]2 has been synthesized and characterized via standard solid and solution state methods including single crystal X-ray crystallography
(mipit = 1-methyl-3-(2-propyl)-2(3H)-imidazolethione). The title compound crystallizes in tetragonal space group I4
1
/a with a = 12.478(2) ?, b = 12.478(2) ?, c = 28.806(6) ?, and Z = 4. The complex is a high melting, colorless solid that has a distorted tetrahedral CdS4 coordination geometry. Thermogravimetric analysis results for the title compound as well as for another potential CdS synthon
and two potential CdSe synthons are reported.
Graphical Abstract The synthesis and characterization of the title compound, a new ionic homoleptic cadmium complex, tetrakis[1-methyl-3-(2-propyl)-2(3H)-imidazolethione]cadmium(II)
hexafluorophosphate is reported. The results of a single crystal X-ray diffraction analysis reveal a distorted tetrahedral
CdS4 coordination sphere about the cadmium.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
103.
104.
Dr. Carol Cristescu 《Monatshefte für Chemie / Chemical Monthly》1977,108(6):1455-1459
5-Substituted 4-thio-6-azauracils [I, 6-alkylthio-3,4-dihydro-5-thioxo-1,2,4-triazin-3(2H)-ones] have been converted with hexamethyldisilazane in 3-trimethylsilyloxy-5-trimethylsilylthio-derivatives(II). These were condensed with 1-O-acetyl-2,3,5-tri-O-benzoyl-d-ribofuranose in the presence of anhydrous stannic chloride to afford the corresponding 1-(2,3,5-tri-O-benzoyl--d-ribofuranosyl)-4-thioxo-5-substituted-6-azauracil (III). 相似文献
105.
Hairong Shi Tomy Varghese Carol C. Mitchell Matthew McCormick Robert J. Dempsey Mark A. Kliewer 《Ultrasonics》2009,49(8):779-785
We have previously reported on the equivalent scatterer size, attenuation coefficient, and axial strain properties of atherosclerotic plaque ex vivo. Since plaque structure and composition may be damaged during a carotid endarterectomy procedure, characterization of in vivo properties of atherosclerotic plaque is essential. The relatively shallow depth of the carotid artery and plaque enables non-invasive evaluation of carotid plaque utilizing high frequency linear-array transducers. We investigate the ability of the attenuation coefficient and equivalent scatterer size parameters to differentiate between calcified, and lipidic plaque tissue. Softer plaques especially lipid rich and those with a thin fibrous cap are more prone to rupture and can be classified as unstable or vulnerable plaque. Preliminary results were obtained from 10 human patients whose carotid artery was scanned in vivo to evaluate atherosclerotic plaque prior to a carotid endarterectomy procedure. Our results indicate that the equivalent scatterer size obtained using Faran’s scattering theory for calcified regions are in the 120–180 μm range while softer regions have larger equivalent scatterer size distribution in the 280–470 μm range. The attenuation coefficient for calcified regions as expected is significantly higher than that for softer regions. In the frequency bandwidth ranging from 2.5 to 7.5 MHz, the attenuation coefficient for calcified regions lies between 1.4 and 2.5 dB/cm/MHz, while that for softer regions lies between 0.3 and 1.3 dB/cm/MHz. 相似文献
106.
An analysis of the conformational preferences of two maleimide substituted cyclohexane derivatives proposed as scaffolds for HIV-1 fusion inhibitors is presented. Hybrid Low Mode-Monte Carlo (1:1) conformational searches using seven different force fields were performed in combination with the GBSA(water) solvent model. Low energy structures identified in this way were subjected to geometry optimization on the B3LYP/6-31G** surface. Solvent effects were included in the quantum calculation using the self-consistent reaction field model for water. Quantum results indicate that the 1,3,5-maleimide functionalized 1,3,5-methyl cyclohexane is more stable in the boat conformation, whereas 1,3,5-maleimide functionalized cyclohexane adopts the expected chair conformation with equatorial arms. None of the force fields studied was able to predict the unexpected preference for the boat conformation of 1,3,5-maleimide functionalized 1,3,5-methyl cyclohexane. Comparison of low energy and experimental structures was also performed. 相似文献
107.
Reversed phases for high-performance liquid chromatography (RP-HPLC) were obtained by thermal immobilization of polysiloxanes having different length chains (C1, C8 and C14) onto HPLC silica particles. The importance both of percent loading of the stationary phase promoted by each immobilization procedure and of the length of the lateral chain of the polymer on the chromatographic performances of the phases obtained is compared and discussed. 相似文献
108.
ABSTRACTWe develop a bit-reversible implementation of Milne's fourth-order predictor algorithm so as to generate precisely time-reversible simulations of irreversible processes. We apply our algorithm to the collision of two zero-temperature Morse-potential balls, which collide to form a warm liquid oscillating drop. The oscillations are driven by surface tension and damped by the viscosities. We characterise the ‘important’ Lyapunov-unstable particles during the collision and equilibration phases in both time directions to demonstrate the utility of the Milne algorithm in exposing ‘Time's Arrow’. 相似文献
109.
Idlir Liko Jonathan T. S. Hopper Timothy M. Allison Justin L. P. Benesch Carol V. Robinson 《Journal of the American Society for Mass Spectrometry》2016,27(6):1099-1104
Membrane protein complexes are commonly introduced to the mass spectrometer solubilized in detergent micelles. The collisional activation used to remove the detergent, however, often causes protein unfolding and dissociation. As in the case for soluble proteins, electrospray in the positive ion mode is most commonly used for the study of membrane proteins. Here we show several distinct advantages of employing the negative ion mode. Negative polarity can yield lower average charge states for membrane proteins solubilized in saccharide detergents, with enhanced peak resolution and reduced adduct formation. Most importantly, we demonstrate that negative ion mode electrospray ionization (ESI) minimizes subunit dissociation in the gas phase, allowing access to biologically relevant oligomeric states. Together, these properties mean that intact membrane protein ions can be generated in a greater range of solubilizing detergents. The formation of negative ions, therefore, greatly expands the possibilities of using mass spectrometry on this intractable class of protein. 相似文献
110.