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931.
The quenching of the fluorescence of HPTS (1-hydroxypyrene-3,6,8-trisulfonate) by Cu(2+), Ni(2+), Co(2+), I(-), and CP(+) (cetylpyridinium cation) has been studied in the w/o microemulsion medium formed with water, AOT [sodium salt of bis (2-ethylhexyl) sulfosuccinic acid], and heptane as components at two [H(2)O]/[AOT] ratios (omega), 6 and 20. The quenching process has been found to be dynamic in nature. The lifetimes of HPTS in the microemulsion medium in the absence and in the presence of quencher have been determined. The analysis of the results has been performed in terms of the Stern-Volmer equation and the quenching sphere of action model. The Poisson distribution equation has been also used in the analysis of the probability of quencher distribution in the microemulsion compartment. The quenching of HPTS has been found to be much lower in microemulsion than in bulk water. 相似文献
932.
Anupam Bhattacharya Ashok K Prasad Jyotirmoy MaityHimanshu PoonamCarl E Olsen Richard A GrossVirinder S Parmar 《Tetrahedron》2003,59(51):10269-10277
Different acid anhydrides (of C2 to C7 aliphatic fatty acids and benzoic acid) have been used to study the selective acylation of primary/secondary hydroxyl groups in 2-phenyl-4-(d-threo-1′,2′,3′-trihydroxypropyl)-2H-1,2,3-triazole, 2-phenyl-4-(d-erythro-1′,2′,3′-trihydroxypropyl)-2H-1,2,3-triazole, 2-phenyl-4-(d-arabino-1′,2′,3′,4′-tetrahydroxybutyl)-2H-1,2,3-triazole and 2-phenyl-4-(d-lyxo-1′,2′,3′,4′-tetrahydroxybutyl)-2H-1,2,3-triazole in the presence of Candida antarctica lipase B in diisopropyl ether. Among the different acid anhydrides, butanoic anhydride was found to be the most efficient acylating agent (for butanoylation); for acetylation, vinyl acetate gave the best results. The reactions with both these acylating agents were highly selective and efficient yielding exclusively the monoacylated products in 95-99% yields in 1-5 h. 相似文献
933.
Upendra Nath Dash Banka Behari Das Uttam Kumar Biswal Tapodhan Panda Narendra Kumar Purohit Dushmanta Kumar Rath Shubhankar Bhattacharya 《Thermochimica Acta》1983,63(3):261-276
The standard potentials of the silver-silver ion electrode in alcohol+water solvent mixtures containing 10 and 20 wt% methanol, ethanol, 1-propanol and 2-propanol have been determined from the electromotive force measurements of the cell Ag(s), AgCl(s), NaCl(c), NaNO3(c)// NaNO3(c), AgNO3(c), Ag(s) at seven different temperatures in the range 5–35°C. The standard potentials in each solvent have been represented as a function of temperature. The standard thermodynamic functions for the electrode reaction, the primary medium effects of various solvents upon Ag+, and the standard thermodynamic quantities for the transfer of 1 g-ion of Ag+ from water to the respective alcohol + water media have been evaluated and discussed in the light of ion-solvent interactions as well as the structural changes of the solvents. From the values of the standard potentials of the Ag/Ag+ and Ag/AgX, X? electrodes, the thermodynamic solubility product constants of silver chloride, silver bromide, silver iodide and silver thiocyanate have been determined in alcohol + water solvent mixtures at different temperatures. 相似文献
934.
Abhoy Karmakar Amit Bhattacharya Diganta Sarkar Guy M. Bernard Arthur Mar Vladimir K. Michaelis 《Chemical science》2021,12(9):3253
Tin halide perovskites are promising candidates for lead-free photovoltaic and optoelectronic materials, but not all of them have been well characterized. It is essential to determine how the bulk photophysical properties are correlated with their structures at both short and long ranges. Although CsSnCl3 is normally stable in the cubic perovskite structure only above 379 K, it was prepared as a metastable phase at room temperature. The transition from the cubic to the monoclinic phase, which is the stable form at room temperature, was tracked by solid-state 133Cs NMR spectroscopy and shown to take place through a first-order kinetics process. The complete solid solution CsSn(Cl1−xBrx)3 (0 ≤ x ≤ 1) was successfully prepared, exhibiting cubic perovskite structures extending between the metastable CsSnCl3 and stable CsSnBr3 end-members. The NMR spectra of CsSnBr3 samples obtained by three routes (high-temperature, mechanochemical, and solvent-assisted reactions) show distinct chemical shift ranges, spin-lattice relaxation parameters and peak widths, indicative of differences in local structure, defects and degree of crystallinity within these samples. Variable-temperature 119Sn spin-lattice relaxation measurements reveal spontaneous mobility of Br atoms in CsSnBr3. The degradation of CsSnBr3, exposed to an ambient atmosphere for nearly a year, was monitored by NMR spectroscopy and powder X-ray diffraction, as well as by optical absorption spectroscopy.Unravelling the atomic-level chemical structure, slow phase conversion or degradation pathways and rapid halogen hopping of cesium tin(ii) halide perovskites using solid-state 119Sn and 133Cs NMR spectroscopy. 相似文献
935.
A spectrophotometric method has been described for the estimation of ammonium acetate with the help of sensitized Schiff's reagent. 1) Ammonium acetate restores the colour of fuchsin from the Schiff's reagent as shown by the same absorption maxima at 535 mμ of the coloured compound and fuchsin. 2) Standard curves of optical density versus concentration of ammonium acetate with different sets of sensitized Schiff's reagent having varying SO2 contents have been presented. 3) There is a limit of ammonium acetate concentration beyond which the sensitivity considerably decreases. 4) Appropriate amounts of acetone along with a particular set of sensitized Schiff's reagent make the latter useful for different sensitive ranges of concentrations of ammonium acetate. 5) The method may be extended in its scope for the estimation of ammonium salts of other organic acids which are weaker than H2SO2. 相似文献
936.
Mishra L Bindu K Bhattacharya S 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(5):807-813
2,6-Diacetylpyridine and 1,2-diaminoethane in the presence of copper(II) and zinc(II) chlorides containing a few drops of acetic acid were condensed into compositions [CuLH2]2.2HCl.H2O (1), [Cu2LPyz]2.2HCl.4CH3COCH3 (2) [CuZnLPyz]2.2HCl.2CH3COCH3.10H2O (3) and [ZnL'Cl]3.3HCl.3H2O (4) substantiated by elemental analyses, IR, UV-vis, 1H NMR and FAB mass spectral data. Demetallation of a Ni(II) complex (isolated as above) afforded macrocyclic skeleton LH4, whereas L' symbolizes a skeleton of the ligand containing only ethylenediamine and 2,6-diacetylpyridine. Molecular structure optimization using MM2 force field calculations for the complexes revealed distorted square pyramidal geometry around Cu(II) centers in complexes 1 and 2 and tetrahedral geometry around Cu(II) and Zn(II) centers with different degrees of distortion in complex 3 whereas three Zn(II) atoms (each in distorted square pyramidal geometry) attached via Cl bridges form a cyclic structure in complex 4. In complexes 1 and 2,Cu-Cu = 2.63-2.66 angstroms indicated the possibility of coupling between the two Cu(II) centers which has been supported by lower magnetic moment as well as ESR spectra showing half-field signal. 相似文献
937.
J. N. Sharma K. Bhattacharya R. G. Swami S. K. Tangri T. K. Mukherjee 《Journal of Radioanalytical and Nuclear Chemistry》1966,214(3):223-233
The dissolution of UO2 in carbonate-bicarbonate solutions containing sodium hypochlorite as an oxidant has been investigated. The effect of temperature, sodium hypochlorite concentration and stirring speed was examined. In the temperature range of 303 to 318 K, the leaching reaction displayed linear kinetics. Apparent activation energy obtained from the differential approach was found to be 57 kJ mol–1. This relatively high activation energy value indicates a chemically controlled behavior of UO2 dissolution. The order of reaction with respect to sodium hypochlorite concentration was found to be unity. 相似文献
938.
Mousumi Chakraborty Chiranjib Bhattacharya Siddhartha Dutta 《Journal of membrane science》2003,220(1-2):155-164
An artificial neural network (ANN) model of emulsion liquid membrane (ELM) process is proposed in the present study which is able to predict solute concentration in feed during extraction operation and ultimate % extraction at different initial solute concentration in feed phase, internal reagent concentration, treat ratio, volume fraction of internal aqueous phase in emulsion and time. Because of the complexity in generalization of the phenomenon of ELM process by any mathematical model, the neural network proves to be a very promising method for the purpose of process simulation. The network uses the back-propagation algorithm (BPA) for evaluating the connection strengths representing the correlations between inputs (initial solute concentration in feed phase, internal reagent concentration, treat ratio, volume fraction of internal aqueous phase in emulsion and time) and outputs (solute concentration in feed during extraction operation and % extraction). The network employed in the present study uses five input nodes corresponding to the operating variables and two output nodes corresponding to the measurement of the performance of the network (solute concentration in feed during extraction and % extraction). Batch experiments are performed for separation of nickel(II) from aqueous sulphate solution of initial concentration in the 200–100 mg/l ranges. The network employed in the present study uses two hidden layers of optimum number of nodes being thirty and twenty. A leaning rate of 0.3 and momentum factor of 0.4 is used. The model predicted results in good agreement with the experimental data and the average deviations for all the cases are found to be well within ±10%. 相似文献
939.
J. Bhattacharya S. K. Chakravarti S. Talapatra S. K. Saha S. C. Guhaniyogi 《Journal of polymer science. Part A, Polymer chemistry》1989,27(12):3977-3983
Initiation of polymerization of methyl methacrylate with redox system montmorillonite (with lattice Fe3+)–thiourea has been achieved. The rates are dependent on both clay mineral and thiourea. Amidosulfenyl radicals are believed to initiate the polymerization on the clay surface. The polymerization produced nonextractable clay–polymer adduct up to an extent of 70 wt %. The pH of the medium (in the acidic range) did not affect the polymerization rate. 相似文献
940.
Bhattacharya S Banerjee S Nayak SK Chattopadhyay S Mukherjee AK 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(5):1099-1104
Molecular complex formation between [60]- and [70]fullerenes with a series of phosphine oxides, namely, tri-n-octyl phosphine oxide, triphenyl phosphine oxide and tri-n-butyl phosphine oxide has been studied in CCl4 medium by NMR spectrometric method. Both [60]- and [70]fullerenes have been shown to form 1:1 adducts with the above series of phosphine oxides. Formation constants (K) for all the complexes have been determined from the systematic variation of NMR chemical shifts of specific protons of the donors in presence of [60]- and [70]fullerenes. Trends in the values of K suggest that [70]fullerene binds stronger with the phosphine oxides relative to [60]fullerene. 相似文献