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31.
A method for the determination of sulfide based on its interference with the determination of Hg by cold vapor atomic absorption spectrometry is described. The decrease in mercury absorbance at 253.7nm is proportional to the concentration of sulfide over the range of 10–320ngmL–1. The limit of detection was found to be 7ngmL–1 and the relative standard deviation (R.S.D.) for the determination of different concentrations of sulfide was in the range of 1.8–2.2%. This method was applied to the determination of sulfide in whole human blood after gas-phase separation. 相似文献
32.
Abdollah Sharifian Kaykavoos Parang Hassan Zorrieh-Amirian Mehrdad Nazarinia Abbas Shafiee 《Journal of heterocyclic chemistry》1994,31(6):1421-1423
Substituted 2-phenethyl-1,2,4-triazoles, 1-phenethylimidazoles 3 and 1-phenethylbenzimidazoles 5 were synthesized from the reaction of compound 8 with tri-n-butyltin hydride in good yield. The reaction of substituted-2-phenethyl halide with 1H-1,2,4-triazoles, imidazoles and benzimidazoles gave a low yield. The yield was increased by the use of substituted-2-phenethyl p-toluensulfonate. 相似文献
33.
M. A. A. Al-Janabi H. A. Kaleefa M. G. Jalhoom E. H. Abbas A. S. Al-Warith 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(1):165-175
99Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of99Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and99Mo was back-extracted from the organic phase with NH4OH solution. The percent recovery from the organic phase was 91% and the purity of99Mo was more than 99%. Pure99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of99Mo from131I and other fission products (10% HDEHP on kieselguhr bed).131I and other isotopes were quantitatively eluted with 0.1M H2SO4,99Mo was eluted using a mixture of 0.5 M HCl and 30% H2O2. 相似文献
34.
Abbas Eslami 《Thermochimica Acta》2004,409(2):189-193
Solid state thermal isomerization of [Co(NH3)5(ONO)]Cl2 (nitrito isomer) to [Co(NH3)5(NO2)]Cl2 (nitro isomer) and reverse reaction were investigated by non-isothermal differential scanning calorimetry (DSC) and found to be essentially an equilibrium process. The interconversions are accelerated at above 65 °C and reach to equilibrium state at about 155 °C. After establishment of the equilibrium the relative amounts of two isomers at any temperature are governed by Gibbs free energy relationship. The experimental enthalpy changes of isomerization of pure nitrito and nitro solid samples to the equilibrium state are −4.67 (±0.19) and 0.99 (±0.05) kJ mol−1, respectively. From these values, total enthalpy change was calculated as: ΔH°=−5.66(±0.20) kJ mol−1. Using Gibbs free energy relationship, equilibrium constant, total free energy and entropy changes were estimated at 60 °C as: K=7.72(±0.8), kJ mol−1 and J K−1 mol−1.An initial rate method has been developed to determine the kinetic parameters of these reactions from non-isothermal DSC data. Both nitro to nitrito and reverse reactions obey first order kinetic law in solid state. Estimated activation parameters of forward and reverse paths at 60 °C are , , and , respectively. The negative activation entropy of both directions support the intramolecular mechanism of isomerization, including formation of a seven coordinate transition state, which formerly suggested based on spectral and X-ray methods. 相似文献
35.
A new micelle-mediated phase preconcentration method for preconcentration of ultra-trace quantities of beryllium as a prior step to its determination by spectrophotometry has been developed. Chrome Azurol S (CAS) and cetyltrimethylammonium bromide (CTAB) were used as chelating agent and cationic surfactant, respectively. The method evaluates and eliminates the blank bias error present in such procedures using mean centering of ratio spectra. This procedure gives more accurate results than the traditional approach using absorbance values against reagent blank. The optimal extraction and reaction conditions were studied and the analytical characteristics of the method (e.g., limit of detection, linear range, preconcentration and improvement factors) were obtained. Linearity was obeyed in the range of 0.9-18.0 ng mL−1 (1.00 × 10−7-2.00 × 10−6 mol L−1) of beryllium. The detection limit of the method is 0.51 ng mL−1 (5.66 × 10−8 mol L−1) of beryllium. The interference effect of some anions and cations was also tested. The method was applied to the determination of beryllium in spring water samples. 相似文献
36.
Structural characterization of nickel oxide nanowires by X-ray absorption near-edge structure spectroscopy 总被引:1,自引:0,他引:1
Wu ZY Liu CM Guo L Hu R Abbas MI Hu TD Xu HB 《The journal of physical chemistry. B》2005,109(7):2512-2515
Nickel oxide nanowires modified by poly(vinylpyrrolidone) (PVP) were synthesized via a simple chemical pattern. For the first time NiO nanowires with diameters ranging from 40 to 100 nm with the expected ratio (length vs diameter) ranging from 54 to 90 were grown using a simple solution-phase approach (mild method). These nickel nanowires exhibited unique photoluminescence features and displayed a significant UV luminescence. X-ray absorption near-edge spectroscopy has been used to characterize the local Ni environment and identify the electronic structure. Comparing experimental and theoretical spectra at the Ni and O K edges, we determine the lattice distortion via the analysis of the characteristic preedge features and the multiple-scattering structures detected in the X-ray absorption near-edge structure spectra. The correlation between experimental features and the disordered or distorted local structures is also discussed. 相似文献
37.
The partial least squares (PLS-1) calibration model based on spectrophotometric measurement, for the simultaneous determination of CN− and SCN− ions is described. The method is based on the difference in the rate of the reaction between CN− and SCN− ions with chloramine-T in a pH 4.0 buffer solution and at 30 °C. The produced cyanogen chloride (CNCl) reacts with pyridine and the product condenses with barbituric acid and forms a final colored product. The absorption kinetic profiles of the solutions were monitored by measuring absorbance at 578 nm in the time range 20-180 s after initiation of the reaction with 2 s intervals. The experimental calibration matrix for partial least squares (PLS-1) calibration was designed with 31 samples. The cross-validation method was used for selecting the number of factors. The results showed that simultaneous determination could be performed in the range 10.0-900.0 and 50.0-1200.0 ng mL−1 for CN− and SCN− ions, respectively. The proposed method was successfully applied to the simultaneous determination of cyanide and thiocyanate in water samples. 相似文献
38.
Alkylation of cyclohexenyl monoacetate 1 with R2Cu(CN)(MgCl)2 or RMgBr/CuCN (cat.) in Et2O produced trans 1,2-isomers 4, while arylation and alkenylation of 1 was accomplished with lithium borates 5 and a nickel cat. to afford trans 1,4-isomers 3 selectively. Furthermore, several transformations of the products were carried out to demonstrate synthetic advantages of the present reactions. 相似文献
39.
[reaction: see text]. Commercially available cyanoethyl phosphoramidites derived from T, d(C), d(A), and d(G) were hydrolyzed (1H-tetrazole, MeCN/H2O) to give the corresponding H-phosphonates in excellent yields. Palladium(0)-catalyzed cross-coupling of each of these with the thymidine-derived vinylbromide 2 afforded the corresponding vinylphosphonate-linked dimers TT, d(C)T, d(A)T, and d(G)T in modest to good yields. The TT dimer was further elaborated to give a 5'-DMT-TT-3'-CEP building block, and this was used in the automated synthesis of the TpTTpT tetramer. 相似文献
40.
Abolghasem Moghimi Robabeh Alizadeh Hossein Aghabozorg Abbas Shockravi M. Carla Aragoni Francesco Demartin Francesco Isaia Vito Lippolis Andrew Harrison A. Shokrollahi Mojtaba Shamsipur 《Journal of Molecular Structure》2005,750(1-3):166-173
The one-pot reaction between the novel proton transfer compound (pydaH2)2+(phendc)2−, LH2, and Cu(II) afforded the compounds (pydaH)2[Cu(phendc)2]·10H2O, 1, and (pydaH)2[Cu(phendc)(phendcH)]2·5H2O, 2, where pyda=2,6-diaminopyridine, and phendcH2=1,10-phenanthroline-2,9-dicarboxylic acid. The single crystal X-ray diffraction analysis of 1 and 2 revealed that these are two novel self-assembled 3D Cu(II) complex-organo-networks, in which (pydaH)+ ions and [Cu(phendc)2]2− or complex units are held together by ion pairing, H-bonding, and π–π interactions. Magnetic measurements over the temperature range 1.8–310 K revealed no significant magnetic coupling between Cu(II) centers in 1 or 2. 相似文献