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11.
A three-component coupling was used to prepare a series of 1,4-disubstituted-1,2,3-triazoles from the corresponding acetylated Baylis-Hillman adducts, sodium azide and terminal alkynes. This one-pot reaction further increases the efficacy of ‘Click’ synthesis and diversifies the preparation of multi-functional 1,4-disubstituted-1,2,3-triazoles. 相似文献
12.
Differential
scanning calorimetry (DSC) is a thermal analytical tool for preformulation
studies. Extrapolated melting temperature (TP)
and heat of fusion (ΔHf)
can be used as parameters for optimizing the DSC performance. Two model pharmaceuticals
acetaminophen and nicotinamide are used in this study. Using a factorial design
for the experimental model and matrix analysis the results, the effect of
sample mass, heating rate and the nitrogen flow rate were evaluated on the
ΔHf values
and TP values. Two
levels for each of the procedural variables were used as a balanced experimental
design with two sample sizes, two heating rates and two nitrogen flow rates.
It was found that the change in the heating rate caused significant changes
in the ΔHf
values but not the Tp
values for acetaminophen. However, no significant effect was found for the Tp value but ΔHf value was affected to a
certain extent for nicotinamide. 相似文献
13.
Chatterjee S Basu S Ghosh N Chakrabarty M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2005,61(8):1887-1891
In fluorescence quenching study via electron transfer (ET), the quenching rate constant (k(q)) values generally decrease with lowering of quencher concentration, since smaller concentration of quencher always leads to a red shift in the donor-acceptor (D-A) distance in ET [M. Tachiya, S. Murata, J. Phys. Chem. 96 (1992) 8441; S. Murata, M. Tachiya, J. Phys. Chem. 100 (1996) 4064; L. Burel, M. Mastafavi, S. Murata, M. Tachiya, J. Phys. Chem. A 103 (1999) 5882]. However, while doing a comparative study with different carbazole (CZ) derivatives-1,4-dicyanobenzene (DCB) systems in benzene (BZ), we observed a deviation from that normal behaviour. It was found that for all of them with lower quencher (DCB) concentration, k(q) values actually increase instead of the expected reduction. Exceptionally, for simple CZ (C12H9N) with decrease in concentration of DCB, k(q) values can even reach the order of energy transfer (10(11) s(-1)). Interestingly, it is not observed when toluene (TL) or xylene (XY) is used as solvent. To explain this unique observation, a sandwich type of molecular structure is predicted, where BZ sliding in between CZ and DCB brings them closer enough, imparting more through bond character to CZ-DCB interaction and hence a higher rate of ET (k(q)) is observed [L. Burel, M. Mastafavi, S. Murata, M. Tachiya, J. Phys. Chem. A. 103 (1999) 5882]. 相似文献
14.
The change in semiconductive properties of β-apo-8′-carotenal, astacene and methyl bixin on adsorption of various vapours
on the crystallite surfaces has been studied at a constant sample temperature. The adsorption of vapours enhances the semiconductivity
of the polyenes appreciably. This enhancement depends on the chemical nature and also on the pressure of the adsorbed vapour.
The adsorption and desorption kinetics follow the modified Roginsky-Zeldovich relation. A two stage desorption process, the
first stage of which gives a Lennard-Jones potential energy curve and is followed by a rate-determining transition over a
potential energy barrier to the second stage of adsorption forming weakly bound complexes between the vapour molecules and
the polyene crystallites, can explain satisfactorily the experimentally observed kinetic data. 相似文献
15.
J. Dutta A. Chatterjee S. Basu 《Journal of Radioanalytical and Nuclear Chemistry》1994,181(2):433-439
A radiochemical solvent extraction method for the determination of iron(III) employing the chelating extractant malonic anilide (MA), synthesized in our laboratory, has been described. Effects of different parameters on the extraction of iron(III) from 2M hydrochloric acid into a mixed organic solvent (methyl isobutyl ketone (TIBK) and diethyl ether) have been studied in detail. The method was applied for the estimation of iron content in several fruits using the principle of substoiciometric isotope dilution analysis. 相似文献
16.
Biswanath Das Katta Venkateswarlu Maddeboina Krishnaiah Harish Holla 《Tetrahedron letters》2006,47(49):8693-8697
A simple, efficient and rapid method has been developed for high-yielding regioselective nuclear monobromination of aromatic and heteroaromatic compounds using NBS in the presence of sulfonic-acid-functionalized silica at room temperature. The catalyst works under heterogeneous conditions and can be recycled. 相似文献
17.
Trace amounts of lead in copper can be determined by differential-pulse anodic-stripping voltammetry after separating it from the matrix. Lead was quantitatively retained on a small Dowex 1-X4 ion-exchange column, without retaining copper when present as a copper-amine complex in solutions containing 0.2 M sodium hydroxide. Subsequent desorption was done with 2 M nitric acid. After deposition for 1 min on a hanging mercury drop electrode and subsequent stripping, the limit of detection was 2 ng ml?1 and the limit of quantification was 6.6 ng ml?1. Recoveries of lead were checked by standard addition to copper solution. 相似文献
18.
An amperometric method for the determination of thiocarbamyl sulphonamides has been developed, based on the cleavage of the S-N bond by hydriodic acid. The method can also be applied for the cleavage of the S-S bond in thiuram disulphides and dibenzothiazyl disulphide, and thus provides a useful means for the estimation of these compounds as well. 相似文献
19.
Graff JN McElhaney AE Basu P Gruhn NE Chang CS Enemark JH 《Inorganic chemistry》2002,41(10):2642-2647
Complexes of the form (Tp*)MoOCl(p-OC(6)H(4)X) and (Tp*)MoO(p-OC(6)H(4)X)(2) (Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate and X = OEt, OMe, Et, Me, H, F, Cl, Br, I, and CN) were examined by electrochemical techniques and gas-phase photoelectron spectroscopy to probe the effect of the remote substituent (X) on electron-transfer reactions at the oxomolybdenum core. Cyclic voltammetry revealed that all of these neutral Mo(V) compounds undergo a quasireversible one-electron oxidation (Mo(VI)/Mo(V)) and a quasireversible one-electron reduction (Mo(V)/Mo(IV)) at potentials that linearly depend on the electronic influence (Hammett sigma(p) parameter) of X. The first ionization energies for (Tp*)MoO(p-OC(6)H(4)X)(2) (X = OEt, OMe, H, F, and CN) were determined by photoelectron spectroscopy. A nearly linear correlation was found for the Mo(VI)/Mo(V) oxidation potentials in solution and the gas-phase ionization energies. Calculated heterogeneous electron-transfer rate constants show a slight systematic dependence on the substituent. 相似文献
20.
Summary Investigations were carried out on the isomerization and base hydrolysis ofcis andtrans forms of dithiosulphatobis-(ethylenediamine)cobalt(III) ions. Thecis form isomerizes to thetrans form in neutral aqueous medium, rates being 1.15, 2.30 and 4.0×10–5s–1, respectively at 42, 50 and 58 °C. Thetrans complex isomerizes to thecis form in basic solution only, the rate varying with pH in a sigmoid pattern. In presence of OH–, an acid-base equilibrium of the complex ion sets in, but only the basic form takes part in the isomerization reaction. Hydrolysis of thecis isomer proceeds through a base-dependent path only, but that of thetrans isomer proceeds both through base-dependent and base-independent paths. The mechanisms are associative in nature. Thetrans form reacts faster thancis in all cases. 相似文献