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101.
Spectral Element Discretization of the Stokes Equations in Deformed Axisymmetric Geometries 下载免费PDF全文
Zakaria Belhachmi & Andreas Karageorghis 《advances in applied mathematics and mechanics.》2011,3(4):448-469
In this paper, we study the numerical solution of the Stokes system
in deformed axisymmetric geometries. In the azimuthal direction the
discretization is carried out by using truncated Fourier series,
thus reducing the dimension of the problem. The resulting
two-dimensional problems are discretized using the spectral element
method which is based on the variational formulation in primitive
variables. The meridian domain is subdivided into elements, in each
of which the solution is approximated by truncated polynomial
series. The results of numerical experiments for several geometries
are presented. 相似文献
102.
Mihoubi Z Wilcox KG Elsmere S Quarterman A Rungsawang R Farrer I Beere HE Ritchie DA Tropper A Apostolopoulos V 《Optics letters》2008,33(18):2125-2127
We report what we believe to be the first demonstration of an all-semiconductor room-temperature terahertz time domain spectrometer. An optical Stark mode-locked vertical-external-cavity surface-emitting laser with 480 fs pulses at 1044 nm was used to illuminate low-temperature-grown photoconductive antennae with 5 mum-gap bow-tie-shaped electrodes. The coherently detected spectrum has a bandwidth close to 1 THz, in which water absorption lines at 0.555 and 0.751 THz can be resolved. 相似文献
103.
The hydrodynamic and heat transfer behavior of a bed consisting of magnetic and shale oil particle admixtures under the effect
of a transverse magnetic field is investigated. The phase diagram, bed void fraction are studied under wide range of the operating
conditions i.e., gas velocity, magnetic field intensity and fraction of the magnetic particles. It is found that the range
of the stabilized regime is reduced as the magnetic fraction decreases. In addition, the bed voidage at the onset of fluidization
decreases as the magnetic fraction decreases. On the other hand, Nusselt number and consequently the heat transfer coefficient
is found to increase as the magnetic fraction decreases. An empirical equation is investigated to relate the effect of the
gas velocity, magnetic field intensity and fraction of the magnetic particles on the heat transfer behavior in the bed. 相似文献
104.
George Ferguson Alan J. Lough David M. Smith Choudhury M. Zakaria Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(8):922-923
In the title compound, [Na(C2H3N2O3)], the Na+ cation lies on a centre of inversion in space group P21/m and all the atoms of the anion lie on a mirror plane. Na is octahedrally coordinated by four O and two N atoms from six different anions and each anion is coordinated to six different Na+ cations, forming chains of confacial octahedra which link the anion layers. Within these layers, the individual anions are linked by both O—H?O and C—H?O hydrogen bonds. 相似文献
105.
Choudhury M. Zakaria George Ferguson Alan J. Lough Christopher Glidewell 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(7):m271-m274
Hexamethylenetetramine, C6H12N4, and ferrocenecarboxylic acid, C11H10FeO2, form a 1:2 adduct, (I), which is a salt, viz. hexamethylenetetraminium(2+) bis(ferrocenecarboxylate), (C6H14N4)[Fe(C5H5)(C6H4O2)]2. The dication in (I) is disordered with two orientations at a site of mm2 symmetry in space group Fmm2, while the anion lies across a mirror plane with its unsubstituted cyclopentadienyl ring disordered over two sets of sites. With ferrocene‐1,1′‐dicarboxylic acid, C12H10FeO4, hexamethylenetetramine forms a 1:1 adduct, (II), in which both components are neutral, viz. hexamethylenetetramine–ferrocene‐1,1′‐dicarboxylic acid (1/1), [Fe(C6H5O2)2]·C6H12N4. The amine component in (II) is disordered with two orientations at a site of mm2 symmetry in space group Cmcm, while the acid component is disordered with two orientations at a site of 2/m symmetry. The components in (I) are linked into a finite three‐ion aggregate by a single N—H⃛O hydrogen bond, while the components of (II) are linked into continuous chains by a single O—H⃛N hydrogen bond. 相似文献
106.
107.
K. S. Hamdan S. M. Abdullah K. Sulaiman R. Zakaria 《Applied Physics A: Materials Science & Processing》2014,115(1):63-68
We report an alternative approach to enhance the optical and electrical performance of a vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine:poly(3hexylthiophene) (VOPcPhO:P3HT) blending system by integrating plasmonic spherical silver into an active layer of organic solar cells. Studies of the influence of the size distribution and optical properties of the silver nanoparticles were carried out using UV–Vis spectroscopy and field emission scanning electron microscopy, respectively. Electrical characteristics with and without the presence of metallic nanostructures were analyzed using J–V characteristics to observe the plasmonic effects on the performance in the VOPcPhO:P3HT organic solar cells. 相似文献
108.
Essam S. Zakaria Ismail M. Ali Ibrahim M. El-Naggar 《Journal of Radioanalytical and Nuclear Chemistry》2004,261(3):689-696
The ion-exchange isotherms of Ni2+/H+ and Co2+/H+ have been determined with a solution of 0.1 ionic strength for both forward and backward reactions at 25°C by a batch technique. The thermodynamic equilibrium constants for
the exchange process have been calculated using the Gains and Thomas equation. The preference Ni2+>Co2+ has been shown. The ion exchange selectivity for exchange of Ni2+ and Co2+ ions with hydrogen ions on zirconium titanate has been investigated as a function of [HCl] from aqueous and 25% of methanol
and/or ethanol solutions. The values of the thermodynamic functions for the studied systems have been reported.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
109.
E. S. Zakaria I. M. Ali H. F. Aly 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):389-397
Iron(III) (FeTi) and chromium (III) titanates (CrTi) were prepared as cation exchange materials in a granular form. The rate
of the isotopic exchange of Na+/*Na+ and Zn2+/*Zn2+ between aqueous solution and iron(III) and chromium(III) titanates in Na+ or Zn2+form has been carried out radiometrically in the 25-60 °C temperature range. The exchange rate is controlled by a particle
diffusion mechanism and experimental and theoretical approaches have been used to obtain the rate of diffusion through the
spherical particles of the exchangers. The values of self diffusion () of Na+ and Zn2+ ions were measured at different operation conditions, particle size, reaction temperatures and drying temperatures of the
matrix. The values of kinetic and thermodynamic parameters were calculated and their significance discussed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
110.
Highly sensitive and selective catalytic determination of formaldehyde and acetaldehyde 总被引:2,自引:0,他引:2
A highly sensitive, simple and selective kinetic method was developed for the determination of ultra-trace levels of formaldehyde and acetaldehyde based on their catalytic effect on the oxidation of N,N-diethyl-p-phenylenediamine (DPD) with hydrogen peroxide. The reaction was monitored spectrophotometrically by tracing the formation of the red-colored oxidized product of DPD at 510nm, within 30s of mixing the reagents. The optimum reaction conditions were: 20mmolL(-1) DPD, 250mmolL(-1) H(2)O(2), 150mmolL(-1) phosphate, 150mmolL(-1) citrate and pH 6.60+/-0.05 at 25 degrees C. Following the recommended procedure, formaldehyde and acetaldehyde could be determined with linear calibration graphs up to 0.50 and 1.4microg mL(-1) and detection limits, based on the 3S(b)-criterion, of 0.015 and 0.035microg mL(-1), respectively. In addition, analytical data for other 10 aldehydes were also presented. The high sensitivity and selectivity of the proposed method allowed its successful application to rain water, mainstream smoke (MSS) and disposed tips of smoked cigarettes (DTSC). A sample aliquot was directly analyzed for its total water-soluble aldehyde content. A second sample aliquot was heated at 80 degrees C for 10min to expel acetaldehyde and the aliquot was analyzed for its content of other water-soluble aldehydes (expressed as formaldehyde equivalent), and acetaldehyde was determined by difference. The analytical results were in excellent agreements with those obtained following the standard HPLC method based on pre-column derivatization with 2,4-dinitrophenylhydrazine. Moreover, published catalytic-spectrophotometric methods for the determination of aldehydes were reviewed. 相似文献