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Differential scanning calorimetry was used to study the thermal decomposition of haemin chloride and its derivatives protoporphyrin and bilirubin. Under a static air atmosphere, exothermic transitions due to degradation were recorded for the two former compounds, whereas bilirubin exhibited a higher thermal stability. Thermogravimetry indicated that the weight loss process with these compounds under an oxidizing atmosphere of oxygen was different from that under an inert atmosphere of nitrogen. Infrared spectra of these compounds were also recorded and are briefly discussed. 相似文献
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Kamal A. Idriss Magda S. Saleh Hassan Sedaira M. M. Seleim Elham Y. Hashem 《Monatshefte für Chemie / Chemical Monthly》1991,122(6-7):507-520
Summary The solution equilibria of 2-hydroxynicotinic acid (hyna) complexes with mercury(II) have been studied spectrophotometrically in 50% (v/v) ethanol at 20°C and an ionic strength of 0.1mol dm–3 (NaClO4). Three mercuric complexes are formed in solution in dependence on the acidity of the medium. The basic characteristics of the different complexes are determined and the analytical aspects of the complexation reaction are demonstrated. A critical investigation has also been presented of the solution equilibria and stability of the mixed complex of mercury(II) withhyna and thiosalicylic acid (tsa). The various complex transitions leading to the formation of the 1 : 1 : 1 Hg(tsa)(hyna) ternary complex in solution are investigated. The non-charged mono-ligand complex Hg(hyna) is used for UV-spectrophotometric determination of mercury atpH 4.5–5 (max=325nm, =0.8·104lmol–1cm–1). The system obeyed Beer's law up to 36.1 µg ml–1 of Hg(II). The optimum concentration range (Ringbom) is between 6 and 28.5µg ml–1. Interference caused by a number of ions was masked by the addition of fluoride ions.
Lösungsgleichgewichte und Stabilitätskonstanten von Komplexen der Pyridincarbonsäuren: Die Komplexierungsreaktion von Quecksilber(II) mit 2-Hydroxynikotinsäure
Zusammenfassung Die Lösungsgleichgewichte von 2-Hydroxynikotinsäure (hyna) mit Hg(II) wurde spektrophotometrisch in 50% (v/v) Ethanol bei 20°C und einer Ionenstärke von 0.1 mol dm–3 (NaClO4) untersucht. In Abhängigkeit von der Acidität des Mediums werden drei Quecksilberkomplexe gebildet. Die grundlegenden Charakteristika der Komplexe wurden bestimmt und die analytischen Aspekte aufgezeigt. Die gemischten Komplexe von Hg(II) mithyna und Thiosalicylsäure (tsa), insbesondere die verschiedenen Komplexübergänge zum ternären 1 : 1 : 1 Hg(tsa)(hyna)-Komplex, wurden ebenfalls untersucht. Der ungeladene Monoligandenkomplex Hg(hyna) kann beipH 4.5–5 zur UV-spektroskopischen Quecksilberbestimmung eingesetzt werden (max=325nm, =0.8·104lmol–1cm–1). Das System gehorcht bis zu einer Hg(II)-Konzentration von 36.1µgml–1 dem Beerschen Gesetz. Der optimale Konzentrationsbereich (Ringbom) liegt zwischen 6 und 28.5µgml–1. Interferenzen mit einer Reihe anderer Ionen konnten durch Maskierung mit Fluoridionen umgangen werden.相似文献
114.
Equilibrium studies in aqueous solution are reported for dimethyltin(IV) complexes of the zwitterionic buffers “Good’s buffer”, such as Mes and Mops (L). Stoichiometry and stability constants for the complexes formed were determined at different temperature and ionic strength 0.1 M NaNO3. The results showed the best fit of the titration curves were obtained when complexes ML, MLH−1, MLH−2, and MLH−3 were expected beside the hydrolysis products of the dimethyltin(IV) cation. The thermodynamic parameters ΔH°, ΔS° and ΔG° calculated from the temperature dependence of the formation constant of the dimethyltin(IV)-Mes complex was investigated. The effect of dioxane as a solvent on the formation constants of dimethyltin(IV)-Mes complex was discussed. The concentration distribution of the various complex species was evaluated as a function of pH. The bonding sites of the dimethyltin(IV) complexes in solid state with Mes and Mops were characterized by means of elemental analyses and FTIR. The NMR (1H, 13C) spectra of the DMT-Mes complex exhibits the strongly distorted octahedron geometry around tin atom. Also, thermal analyses (TGA and DTA) were discussed. Thermodynamic parameters such as activation energy (Ea), pre-exponential factor (A), entropy of activation (ΔS∗) and free energy of activation (ΔG∗) have been calculated for each step, employing integral method Coats and Redfern. The reaction enthalpy (ΔH) is obtained from DTA data. 相似文献
115.
Molecular Diversity - An efficient and simple protocol for the synthesis of trifluoromethylated quinazolines has been described by I2-/KI-promoted oxidative C(sp3)–C(sp2) bond under the... 相似文献
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