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991.
Navid Nasirizadeh Hamid R. Zare Ali R. Fakhari Hamid Ahmar Mohammad R. Ahmadzadeh Amin Naeimi 《Journal of Solid State Electrochemistry》2011,15(11-12):2683-2693
In this study, an oxadiazole multi-wall carbon nanotube-modified glassy carbon electrode (OMWCNT?GCE) was used as a highly sensitive electrochemical sensor for hydrazine determination. The surface charge transfer rate constant, k s, and the charge transfer coefficient, ??, for electron transfer between GCE and electrodeposited oxadiazole were calculated as 19.4?±?0.5?s?1 and 0.51, respectively at pH?=?7.0. The obtained results indicate that hydrazine peak potential at OMWCNT?GCE shifted for 14, 109, and 136?mV to negative values as compared with oxadiazole-modified GCE, MWCNT?GCE, and activated GCE surface, respectively. The electron transfer coefficient, ??, and the heterogeneous rate constant, k??, for the oxidation of hydrazine at OMWCNT?GCE were also determined by cyclic voltammetry measurements. Two linear dynamic ranges of 0.6 to 10.0???M and 10.0 to 400.0???M and detection limit of 0.17???M for hydrazine determination were evaluated using differential pulse voltammetry. In addition, OMWCNT?GCE was shown to be successfully applied to determine hydrazine in various water samples. 相似文献
992.
Marwan Batiha Mohammednoor Altarawneh Abdullah Alsofi Mohammad Al-Harahsheh Ibrahem Altarawneh Saleh Alrawadieh 《Theoretical chemistry accounts》2011,129(6):823-832
The reaction of aniline with hydrogen atom is investigated herein using the hybrid meta-DFT functional of BB1 K. Hydrogen
atom is found to preferentially add at an ortho position. However, the fate of the o-(C6H5NH2)H adduct is found to be solely the deactivation of the initial addition channel. The rate constant for the abstraction channel
(C6H5NH2 + H → C6H5NH + H2) is fitted by the expression 1.10 × 10−11 exp(−4,200/T) cm3 molecule−1 s−1. Our calculated rate constant for the abstraction channel agrees very well with the available experimental measurements.
Satisfactory agreement is found between calculated and experimental measurements for the displacement channel (C6H5NH2 + H → C6H6 + NH2). Our detailed analysis for the corresponding displacements in toluene and phenol suggests that the three systems exhibit
similar behavior with regard to the relative importance of abstraction and displacement channels. 相似文献
993.
994.
In the present study, the density functional theory (DFT) and Gibbs free energy calculations were performed to investigate
the stability and tautomerism of C4-substituted-3,4-dihydropyrimidin-2(1H)-ones. Three different forms are possible for the ethyl 3,4-dihydropyrimidinones (ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2(1H)-one-5-carboxylates, ethyl 4-aryl-2-hydroxy-6-methyl-1,4-dihydropyrimidine-5-carboxylates and ethyl 4-aryl-2-hydroxy-6-methyl-3,4-dihydropyrimidine-5-carboxylates)
forms that the most stable form is ethyl 4-aryl-6-methyl-3,4-dihydropyrimidin-2 (1H)-one-5-carboxylates (keto-form). The obtained data showed that the substitution on the C4-substitut position can be effective
on the equilibrium constant (K
eq). 相似文献
995.
Mohammad Yazdanbakhsh Nahid Lotfian Haman Tavakkoli Roland Boese 《Central European Journal of Chemistry》2011,9(4):585-589
A novel oxo-centered trinuclear mixed-metal carboxylate complex with unsaturated bridging ligands [Fe2Cr(μ3-O)(C3H3O2)6(H2O)3]·NO3·4H2O has been synthesized and characterized by means of Elemental analyses, Infrared spectroscopy and Crystal structure analysis.
The compound crystallizes isotypically in the monoclinic space group type P21/c. In the compound, each M(III) cation is coordinated by six O atoms from four unsaturated carboxylate groups as bridging ligands, one water molecule as
the terminal ligand, and a μ3-oxygen atom in the center of an equilateral triangle. The infrared spectra show resolved bands arising from νasym(COO) and νsym(COO) vibration of bridging carboxylate ligands along with those of νasym(M2M′O) vibration in the complex. The difference between symmetrical and asymmetrical (COO) ligands indicate that the acrylate
bridge is present in the structure of complex.
相似文献
996.
Javed Iqbal Feroza Hamid Wattoo Muhammad Hamid Sarwar Wattoo Rukhsana Malik Syed Ahmad Tirmizi Muhammad Imran Allah Bux Ghangro 《Arabian Journal of Chemistry》2011,4(4):389-395
Chitosan flakes, extracted from prawns and labeo rohita scales, with high adsorption capacity were prepared after chemical treatment and were used to remove acid yellow dye from water. The results showed that adsorption capacity is dependent on pH, initial concentration of dye, BET, Langmuir surface area and pore volume of the adsorbent. In acidic conditions, the polymer amino groups were protonated (positively charged polymer chain), which showed attraction with negative ions of anionic dye. Chitosan from prawns scales showed higher dye adsorption under the same experimental conditions. Adsorption isotherms were developed and equilibrium data fitted well to Langmuir and Freundlich isotherm models. 相似文献
997.
Mohammad Ghadermazi Marilyn M. Olmstead Jafar Attar Gharamaleki Shahideh Rostami 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(4):o134-o138
Two related proton‐transfer compounds, namely piperazine‐1,4‐diium 4‐oxo‐4H‐pyran‐2,6‐dicarboxylate monohydrate, C4H12N22+·C7H2O62−·H2O or (pipzH2)(cdo)·H2O, (I), and piperazine‐1,4‐diium bis(6‐carboxy‐4‐oxo‐4H‐pyran‐2‐carboxylate), C4H12N22+·2C7H3O6− or (pipzH2)(cdoH)2, (II), were obtained by the reaction of 4‐oxo‐4H‐pyran‐2,6‐dicarboxylic acid (chelidonic acid, cdoH2) and piperazine (pipz). In (I), both carboxyl H atoms of chelidonic acid have been transferred to piperazine to form the piperazine‐1,4‐diium ion. The structure is a monohydrate. All potential N—H donors are involved in N—H...O hydrogen bonds. The water molecule spans two anions via the 4‐oxo group of the pyranose ring and a carboxylate O atom. The hydrogen‐bonding motif is essentially two‐dimensional. The structure is a pseudomerohedral twin. In the asymmetric unit of (II), the anion consists of monodeprotonated chelidonic acid, while the piperazine‐1,4‐diium cation is located on an inversion centre. The single carboxyl H atom is disordered in two respects. Firstly, the disordered H atom is shared equally by both carboxylic acid groups. Secondly, the H atom is statistically disordered between two positions on either side of a centre of symmetry and is engaged in a very short hydrogen‐bonding interaction; the relevant O...O distances are 2.4549 (11) and 2.4395 (11) Å, and the O—H...O angles are 177 (6) and 177 (5)°, respectively. Further hydrogen bonding of the type N—H...O places the (pipzH2)2+ cations in pockets formed by the chains of (cdoH)− anions. In contrast with (I), the (pipzH2)2+ cations form hydrogen‐bonding arrays that are perpendicular to the anions, yielding a three‐dimensional hydrogen‐bonding motif. The structures of both (I) and (II) also feature π–π stacking interactions between aromatic rings. 相似文献
998.
Mohammad R. Torshizian Mohammad H. Kargarnovin Cyrus Nasirai 《Mechanics Research Communications》2011,38(3):164-169
In this paper, a two dimensional functionally graded material (2D-FGM) under an anti-plane load with an internal crack is considered. The crack is oriented in an arbitrary direction. The material properties are assumed to vary exponentially in two planar directions. The problem is analyzed and solved by two different methods namely Fourier integral transforms with singular integral equation technique, and then by the finite element method. The effects of crack orientation, material non-homogeneity, and other parameters on the value of stress intensity factor (SIF) are studied. Finally, the obtained results for Mode III stress intensity factor of different methods are compared. 相似文献
999.
Eulerian-Eulerian two-phase numerical simulation of nanofluid laminar forced convection in a microchannel 总被引:1,自引:0,他引:1
Mohammad Kalteh Abbas Abbassi Majid Saffar-AvvalJens Harting 《International Journal of Heat and Fluid Flow》2011,32(1):107-116
In this paper, laminar forced convection heat transfer of a copper-water nanofluid inside an isothermally heated microchannel is studied numerically. An Eulerian two-fluid model is considered to simulate the nanofluid flow inside the microchannel and the governing mass, momentum and energy equations for both phases are solved using the finite volume method. For the first time, the detailed study of the relative velocity and temperature of the phases are presented and it has been observed that the relative velocity and temperature between the phases is very small and negligible and the nanoparticle concentration distribution is uniform. However, the two-phase modeling results show higher heat transfer enhancement in comparison to the homogeneous single-phase model. Also, the heat transfer enhancement increases with increase in Reynolds number and nanoparticle volume concentration as well as with decrease in the nanoparticle diameter, while the pressure drop increases only slightly. 相似文献
1000.
Shahid Hussain Arshad Muhammad Nawaz Naeem Nazra Sultana Zafar Iqbal Abdul Ghafar Shah 《Archive of Applied Mechanics (Ingenieur Archiv)》2011,81(8):999-1016
In the present work, vibration characteristics of thin functionally graded cylindrical shells are studied under the influence
of various boundary conditions. Fabrication of FGM cylindrical shell is carried out by using exponential volume fraction law.
Strain- and curvature-displacements relationships are taken from Love’s thin shell theory. The frequency equation in the form
of eigenvalue problem is obtained by adapting the Rayleigh-Ritz method. Characteristic beam functions are assumed to approximate
the axial modal dependence. Effects of exponential volume fraction law on the natural frequencies of the FGM cylindrical shells
for various boundary conditions are studied against circumferential wave number, length to radius ratio and thickness to radius
ratio for different values of power law exponents. Results evaluated show good agreement with those available in the literature. 相似文献