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71.
Synthesis of a novel tetracationic acidic organic salt based on DABCO containing two sulfonic acid groups in the skeleton and four hydrogensulfate groups as counterion is described. Its catalytic efficiency in the Knoevenagel condensation of aldehydes with active cyclic methylene compounds in water is investigated. While 2,2'-(phenylmethylene)bis(3-hydroxy-5,5-dimethylcyclohex-2-enone) derivatives were obtained in 40–98% isolated yields in the reaction of aldehydes with dimedone, the corresponding Knoevenagel adducts were provided in 85–95% yields using 1,3-dimethylbarbituric acid. In addition, a DABCO-based polycationic organic salt polymer was prepared and characterized for the first time. 相似文献
72.
Nonlinear Dynamics - In this paper, the numerical solution of time-fractional convection diffusion equations (TF-CDEs) is considered as a generalization of classical ones, nonexponential relaxation... 相似文献
73.
Michael P. Doyle Robert L. Dow Vahid Bagheri William J. Patrie 《Tetrahedron letters》1980,21(29):2794-2798
Oxidations of 2,2-disubstituted-1,4-butanediols by the combination of nickel(II) bromide and benzoyl peroxide and by trityl tetrafluoroborate produce β,β-disubstituted-γ-butyrolactones with exceptional selectivity. 相似文献
74.
Saeed Rayati Saeed Zakavi Somayeh H. Motlagh Vahid Noroozi Maryam Razmjoo Andrzej Wojtczak Anna Kozakiewicz 《Polyhedron》2008
X-ray crystallographic studies have shown that the free base β-tetra-brominated meso-tetraphenylporphyrin (H2TPPBr4) has a slightly ruffled structure with the dihedral angles of 70.1–79.2° between the phenyl groups and the porphyrin mean plane. The N(pyrrole)–N(pyrrolenine) distance is very similar to that of the standard planar porphyrins. The decreased N–H bond length of H2TPPBr4 with respect to that of meso-tetraphenylporphyrin (H2TPP) seems to be due to the weaker intramolecular hydrogen bond of the former relative to the latter caused by the electron-withdrawing effects of the β-bromine substituents. The large red shifts of the Soret and Q(0,0) bands of H2TPPBr4 in comparison with those of H2TPP, in spite of the nearly planar porphyrin core of the compound, also may be explained on the basis of the electron-withdrawing effects of the bromine atoms. Oxidation of styrene, the para-substituted derivatives and cyclooctene with tetrabutylammonium oxone in the presence of catalytic amounts of β-tetra-brominated meso-tetraphenylporphyrinatomanganese(III) acetate immediately gives the epoxide as the sole product. Terminal double bonds and unconjugated ones are less reactive than the conjugated double bonds and show lower selectivities. Catalytic activity of the electron-deficient Mn(H2TPPBr4)OAc dramatically depends on the Co-catalytic activity of the nitrogen donors as the axial base. The best axial bases are the nitrogenous donors with mixed σ- and π-donor ability to the metal centre. 相似文献
75.
Seyed Mehrdad Jalilian Hassan Farhadnejad Farshid Ziaee Behrouz Furughi Nia Hossein Abdollahi Vahid Najafi 《Polymer Science Series B》2016,58(6):675-680
The free radical solution polymerization of n-octyl methacrylate has been studied in benzene-d 6 in the presence of 2,2′-azobisisobutyronitrile as thermal initiator. An on-line nuclear magnetic resonance spectroscopy was applied to record the reaction data and to determine the monomer conversion at different times during the polymerization reaction. Effect of monomer and initiator concentration as well as reaction temperature on polymerization rate was studied. The order of the reaction with respect to initiator (0.45) was consistent with the classical kinetic rate equation, while the order of reaction with respect to monomer (1.87) was much greater than unity. An overall activation energy (E a = 53.8 kJ/mol) was obtained over the temperature range 328?338 K. Also, the efficiency of the synthesized poly(n-octyl methacrylate) for improving the viscosity index of the lube oil was investigated. 相似文献
76.
77.
Vahid Khakyzadeh Mohammad Ali Zolfigol Fatemeh Derakhshan-Panah Majid Jafarian Mir Vahid Miri Maryam Gilandoust 《Molecular diversity》2018,22(2):335-342
The aim of this work is to introduce, model, and optimize a new non-acid-catalyzed system for a direct N\(=\)N–C bond formation. By reacting naphthols or phenol with anilines in the presence of the sodium nitrite as nitrosonium (\(\hbox {NO}^{+})\) source and triethylammonium acetate (TEAA), a N\(=\)N–C group can be formed in non-acid media. Modeling and optimization of the reaction conditions were investigated by response surface method. Sodium nitrite, TEAA, and water were chosen as variables, and reaction yield was also monitored. Analysis of variance indicates that a second-order polynomial model with F value of 35.7, a P value of 0.0001, and regression coefficient of 0.93 is able to predict the response. Based on the model, the optimum process conditions were introduced as 2.2 mmol sodium nitrite, 2.2 mL of TEAA, and 0.5 mL \(\hbox {H}_{2}\hbox {O}\) at room temperature. A quadratic (second-order) polynomial model, by analysis of variance, was able to predict the response for a direct N=N–C group formation. Predicted response values were in good agreement with the experimental values. Electrochemistry studies were done to introduce new Michael acceptor moieties. Broad scope, high yields, short reaction time, and mild conditions are some advantages of the presented method. 相似文献
78.
Soleyman Hosseinzadeh Younes Saadat Hormoz Eslami Faramarz Afshar-Taromi Alireza Hosseinzadeh Mehdi Rimaz Vahid Hooshangi 《Colloid and polymer science》2012,290(16):1713-1719
In this work, the preparation of micron-sized polymer particles with nonspherical shapes via seeded dispersion polymerization of 2-ethylhexyl methacrylate with polystyrene seed particles in the presence of hydrocarbon droplets and evaporation of hydrocarbon after the polymerization under various polymerization conditions was discussed. The effect of second monomer and initiator type, mixing method, and stabilizer content on the shape of the obtained particles was investigated. It was observed that particles with more nonspherical shapes were obtained with increasing the alkyl chain length of ester group of the methacrylate of the second monomer which is because of increasing the absorption amounts of hydrocarbon by second polymer domains. Moreover, the experimental results showed that shape of the particles which was produced by shaking is more nonspherical than the shape of the particles which was obtained from tumbling. Furthermore, particles with different nonspherical shapes were prepared by changing the initiator type and stabilizer content. 相似文献
79.
Nanoparticles of a three-dimensional supramolecular, [Cu(L)2(H2O)2] (1), (L− = 1H-1,2,4-triazole-3-carboxylate), have been synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The thermal stability of compound 1 both its bulk and nano-size has been studied by thermal gravimetric (TG) and differential thermal analyses (DTA) and compared each other. Concentration of initial reagents effects on size and morphology of nano-structured compound 1, have been studied. Calcination of the nano-sized compound 1 at 600 °C under air atmosphere yields CuO nanoparticles. 相似文献
80.
Efficient visible-light-induced photocatalytic degradation of MO on the Cr-nanocrystalline titania-S
Masood Hamadanian Ali Sadeghi SarabiAli Mihammadi Mehra Vahid Jabbari 《Applied Surface Science》2011,257(24):10639-10644
In order to improve visible light photocatalytic activities of the nanometer TiO2, a novel and efficient Cr,S-codoped TiO2 (Cr-TiO2-S) photocatalyst was prepared by precipitation-doping method. The crystalline structure, morphology, particle size, and chemical structure of Cr-TiO2-S were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR) techniques, respectively. Results indicate that the doping of Cr and S, cause absorption edge shifts to the visible light region (λ > 420 nm) compare to the pure TiO2, reduces average size of the TiO2 crystallites, enhances desired lattice distortion of Ti, promotes separation of photo-induced electron and hole pair, and thus improves pollutant decomposition under visible light irradiation. The photocatalytic activities of Cr-TiO2-S nanoparticles were evaluated using the photodegradation of methyl orange (MO) as probe reaction under the irradiation of UV and visible light and it was observed that the Cr-TiO2-S photocatalyst shows higher visible photocatalytic activity than the pure TiO2. The optimal Cr-TiO2-S concentration to obtain the highest photocatalytic activity was 5 mol% for both of Cr and S. 相似文献