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1.
Nataša Bukovec 《Thermochimica Acta》1985,96(2):391-395
The thermal decomposition of N2H5Nd(SO4)2·H2O has been studied by simultaneous TG and DSC and by isothermal weight change determination. The final product and the intermediate phases have been identified by chemical analysis, X-ray powder patterns and infrared spectroscopy. The solid phases in the decomposition sequence are: N2H5Nd(SO4)2· H2O → N2H5Nd(SO4)2 → NH4Nd(SO4)2 → Nd2(SO4)3. The reactions overlap under dynamicconditions, isothermally, however, NH4Nd(SO4)2 can be obtained by 200°C. 相似文献
2.
Nataša Pejić Slobodan Anić Vesna Kuntić Vladana Vukojević Ljiljana Kolar-Anić 《Mikrochimica acta》2003,143(4):261-267
A kinetic method is described for the microquantitative (microconcentration/microvolume) determination of rutin based on potentiometric monitoring of the concentration perturbations of the Bray-Liebhafsky (BL) oscillatory reaction being in a non-equilibrium stationary state close to a bifurcation point. The experiments are carried out in an open reactor. The response of the matrix system to perturbations by different concentrations of rutin ethanolic solutions is followed by a Pt-electrode. In the concentration range between 7.8×10–8moldm–3 and 9.1×10–6mol dm–3, we found a linear dependence of the maximal potential shift, Em, on the logarithm of the rutin concentrations. The unknown concentrations can be determined from the calibration curve up to an accuracy of ±5%. The detection limit is 3.6×10–8mol dm–3. The amount of required sample can be as small as 10µL. 相似文献
3.
The kinetics of the dehydration of CsNd(SO4)2 · 4 H2O to CsNd(SO4)2 · H2O and then to CsNd(SO4)2 are studied by isothermal weight change. The reactions are phase-boundary-controlled. Reaction mechanism and activation energy depend on sample weight. 相似文献
4.
Nebojša Banjac Gordana Ušćumlić Nataša Valentić Dušan Mijin 《Journal of solution chemistry》2007,36(7):869-878
Absorption spectra of eight 3-substituted-5,5-diphenylhydantoins have been recorded in fourteen solvents in the range 200–400 nm.
The effect of solvent dipolarity/polarizability and solvent/solute hydrogen bonding interactions are analyzed by means of
the linear solvation energy relationship (LSER) concept proposed by Kamlet and Taft. The lipophilic activity of the investigated
hydantoins was estimated by the calculation of log 10
P values with the Advanced Chemistry Development Software. The calculated values of log 10
P were correlated with the ratio of the contributions of specific solvent interactions, and, by employing the linear dependence
thus obtained, the pharmacological activity of the studied hydantoin derivatives is discussed. 相似文献
5.
Nataša Bukovec Peter Bukovec Jože Šiftar 《Monatshefte für Chemie / Chemical Monthly》1980,111(4):957-961
Compounds of the type CsLn(SO4)2, (Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were prepared at 300°C. IR spectra were recorded in the range 4,000-250cm–1 and tentatively assigned. The number of observed bands exceeds the predicted number by site symmetry selection rules. Streching bands show bathochromic shifts whereas the deformations exibit hypsochromic shifts on going to heavier lanthanides. At the same time there is an increased splitting of these bands in the same direction. All these facts indicate an increased coupling in the layer structure which is in accordance with the lanthanide contraction.
N. Bukovec, P. Bukovec undJ. iftar, Vest. Slov. Kem. Drus.26, 103 (1979). 相似文献
6.
Five new CuII complexes of general formula [Cu2(Rdtc)tpmc](ClO4)3, (1)–(5), where tpmc and Rdtc
– refer to N,N,N,N-tetrakis(2-pyridylmethyl)-1,4,8,11-teraazacyclotetradecane and piperidine- (Pipdtc), 4-morpholine- (Morphdtc), 4-thiomorpholine- (Timdtc), piperazine- (Pzdtc) or N-methylpiperazine- (N-Mepzdtc) dithiocarbamates, respectively, have been prepared. Elemental analyses, conductometric and magnetic measurements, u.v./vis, i.r., e.p.r. and mass spectroscopy have been employed to characterize them. The complexes adopt an exo coordination of CuII ions and tpmc. The dithiocarbamate ion joins both the sulphur and the copper atoms acting as a bridging ligand The presence of different heteroatoms in the piperidine ring influences the (C=N) and (C=S) vibrations which decrease in the order of the complexes: Pipdtc>N-Mepipdtc>Pzdtc>Morphdtc>Timdtc ligands. Attention has been paid to the detailed mechanism of the mass spectral fragmentation of the complexes. The g
eff factors of the complexes have been also estimated by e.p.r. spectra. Finally, the complexes obtained demonstrate microbiologycal activity against some bacteria. 相似文献
7.
The compounds TlLn(SO4)2·2H2OLn=La, Ce, Pr, Nd and Tl[Ln(SO4)2(H2O)3]·H2OLn=Nd, Sm, Eu, Gd, Tb have been isolated from aqueous solutions of the corresponding sulfates. The dihydrates are all isomorphous and crystallize monoclinic, space groupP21/n,Z=4. The compounds which belong to the second type are also isomorphous and crystallize in monoclinic space groupP 21/c withZ=4.The dehydration has been studied by thermogravimetry, differential scanning calorimetry and isothermal weight change determination. The dihydrates dehydrate in a single step. For the tetrahydrates the reaction is more complex, however no intermediate phases could be isolated.The unit cell parameters, the dehydration temperatures and the dehydration enthalpies are correlated to the ionic radii ofLn
3+.
Synthese und Charakterisierung von TlLn(SO4)2·xH2O (Ln=La-Tb)
Zusammenfassung Die Verbindungen TlLn(SO4)2·2H2OLn=La, Ce, Pr, Nd und Tl[Ln(SO4)2(H2O)3]·H2OLn=Nd, Sm, Eu, Gd, Tb wurden aus wäßrigen Lösungen der entsprechenden Sulfate isoliert. Die Dihydrate sind alle isomorph und kristallisieren monoklin, RaumgruppeP 21/n,Z=4. Die Verbindungen des zweiten Typs sind auch isomorph und kristallisieren in der monoklinen RaumgruppeP 21/c mitZ=4.Die Dehydration wurde mit TG, DSC und dem isothermalen Gewichtsverlust untersucht. Die Entwässerung der Dihydrate verläuft in einer Stufe, die von Tetrahydraten aber in mehreren Stufen mit keiner isolierbaren Zwischenphase.Die Gitterkonstanten, die Dehydratations-Temperaturen und -Enthalpien wurden mit den Ionenradien vonLn 3+ korreliert.相似文献
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10.
Nives Galić Nataša Burić Renato Tomaš Leo Frkanec Vladislav Tomišić 《Supramolecular chemistry》2013,25(5):389-397
The fluorescent peptidocalixarenes, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(O-methyl-l-tryptophanylcarbonylmethoxy)calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,27-di(O-methyl)-26,28-bis(O-methyl-l-tryptophanylcarbonylmethoxy)calix[4]arene (2), were prepared by introducing tryptophan subunits at a lower calixarene rim. Coordination abilities of 1 and 2 towards Eu(III) and alkali metal cations were studied by spectrophotometric, spectrofluorimetric, conductometric and potentiometric titrations in acetonitrile at 25°C. Rather strong complexation was observed for smaller alkali metal cations Li+ and Na+ (log K Li1 >6, log K Li2 >6, log K Na1 = 8.25, log K Na2 = 6.94), and moderate for K+ (log K K1 = 5.09, log K K2 = 4.09). Larger Rb+ and Cs+ cations did not fit in the ion binding site of 1 so no complexation was detected, whereas the more flexible ligand 2 accommodated Rb+ cation (log K Rb2 = 3.44). The fluorescence of 1 (λex = 280 nm, λem = 340 nm) was remarkably quenched by Eu(III). Stability constant of 1:1 (Eu3+:1) complex determined spectrofluorimetrically amounted to log K Eu1 = 6.16. 相似文献