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831.
832.
V. N. Kartsev 《Journal of Structural Chemistry》2004,45(5):832-837
The previously found empirical relationships between the temperature coefficient of internal pressure, on the one hand, and the structure and its evolution in liquids due to variations of temperature and concentration, on the other, are interpreted in terms of the peculiarities of intermolecular interactions. Analysis has revealed that the curves of the temperature dependences of internal pressure P
i(T) of associated liquids are directed upward by their concavity; they have a minimum and asymptotically tend toward P
i = 0 at T→∞. The curves P
i(T) of weakly associated liquids are directed downward by their concavity and have no extrema, but asymptotically tend to zero at T→∞.Original Russian Text Copyright © 2004 by V. N. Kartsev__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 877–882, September–October, 2004. 相似文献
833.
Experimental results are presented for electrode erosion on copper electrodes in magnetically rotated arcs in argon and helium. Measurements were also made of the arc voltage and velocity. The effects due to the contamination of the electrode surface by either a native contaminant layer (copper oxide and carbon traces) or the continuous injection of very small amounts of various diatomic gases (nitrogen, oxygen, chlorine, and carbon monoxide) into the inert plasma gases were determined. The erosion rates for pure argon were significantly higher than those for pure helium (13.5 g/C for argon and 1 g/C for helium) and with both gases, very high arc velocities were measured initially (>60 m/s for argon and >160 m/s for helium) when a natural contaminant layer was still present on the cathode. The removal of this layer resulted in lower velocities (2m/s for argon and 20m/s for helium) and higher erosion rates. The removal of the layer was much faster with argon, due possibly to higher electrode surface current densities for argon arcs. 相似文献
834.
H. Janeschitz-Kriegl H. Wippel Ch. Paulik G. Eder 《Colloid and polymer science》1993,271(12):1107-1115
In this paper a method for the calibration of the heat transfer coefficient between pan and furnace is given. This (second) calibration is necessary in addition to the usual calibration of the temperature scale. Indeed, with increasing cooling rates as required for kinetic measurements, the finite heat flow resistance between pan and furnace becomes evident anyway. We also propose to enlarge this resistance deliberately, in order to separate the time scales of the control system and of the exponential return of the heat flow curve to the base line, as occurring after completion of the phase transition. Only in this way can the heat transfer coefficient be determined with some accuracy. Another advantage of a lowered heat transfer coefficient will be treated in a third paper. It enables an approximate treatment of polymer crystallization kinetics. 相似文献
835.
836.
A novel and stereospecific synthesis of (+)-exo-brevicomin is disclosed. The key step of the reaction sequence employs the sulfinyl moiety as an intramolecular nucleophile to functionalize an alkene π-complexed to a bromonium ion. 相似文献
837.
Herbert Budzikiewicz Peter-Eric Vieth Uwe Krüger 《Monatshefte für Chemie / Chemical Monthly》1981,112(6-7):825-840
In1H-NMR spectra of amids with long-chain aliphatic N-substituents one observes—despite of the free mobility of the aliphatic chain—splitting of the signals of the terminal methyl groups which is caused by the hindered rotation of the amide bond. 相似文献
838.
用外源荧光探针法和旋光度、电导率及pH滴定法研究了去氧胆酸钠(SDOC)在水溶液中的簇集行为.SDOC浓度低于5×10~(-3)~6×10~(-3)mol/L时在水溶液中以二元缔合物形式存在,具有较高的对称性和较弱的碱性并能提供一定的疏水性微环境;浓度高于该值后簇集成胶束,但簇集数(8~10)较小,同时伴随着对称性略微降低和碱性有所提高. 相似文献
839.
840.
Cirilli R Ferretti R Gallinella B La Torre F La Regina G Silvestri R 《Journal of separation science》2005,28(7):627-634
The enantiomeric separation of a series of imidazole analogues of Fluoxetine and Miconazole endowed with potent antifungal activity was performed using cellulose tris(4-methylbenzoate) (Chiralcel OJ) and cellulose tris(3,5-dimethylphenylcarbamate) (Chiralcel OD) as chiral stationary phases. Binary mixtures of n-hexane and alcohol as well as pure alcohols (ethanol or 2-propanol) were used as eluents. The enantiomer elution order was monitored by chiroptical detectors based on on-line optical rotation and circular dichroism measurements. For some of the compounds studied very high enantioseparation factor values (alpha > 7) on Chiralcel OJ CSP were observed. In order to study the chiroptical characteristics of the two most biologically active compounds, chromatographic resolutions were carried out on a semipreparative scale. Assignment of the absolute configuration was empirically established by comparing the CD spectra of the separated enantiomers with those obtained from the enantiomers of Miconazole. 相似文献