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121.
Summary Solochrome violet R.S. has proved to be a sensitive colorimetric reagent for the microdetermination of vanadium in the limits of 0.05 to 6 ppm with a sensitive filter photometer or a spectrophotometer, at 580 nm. A large number of cations up to 100 fold the vanadium amount do not interfere with its determination. The present work comprises a comparative study on the behaviour of solochrome violet and Fast Grey, based upon the great similarity in the molecular structure of the two dyes and the influence of the orthonitrophenolic group in the molecule of Fast Grey.Part I: See Z. analyt. Chem. 178, 184 (1960). 相似文献
122.
Rapid potentiometric methods were given for determination of some sulfide and chromate pigments in pure as well as adulterated samples. The methods are based on oxidation of S2? or Cr3+ with known excess of KBrOs3 to the corresponding (S ↓) or Cr6?. Oxidation of trivalent chromium proceeds only toward completion in presence of a catalyst such as Co2+. Sulfide oxidation needs gradual liberation of H2S—which can be achieved by dropwise additions of the acid—together with the presence of excessive amount of water, in order to obtain accurate results excess oxidant was subsequently reduced with SO2 to produce Br? that can be titrated against Hg(I). The potential breaks are quite sharp for accurate determination of the equivalent points. 相似文献
123.
Adel M. El-Menshawy M. E. Khalifa 《Journal of Radioanalytical and Nuclear Chemistry》2006,268(2):341-348
Summary Duolite
C20 resin modified with trimethylammonium acetosalycoylhydrazone has been
developed, for the selective separation and/or preconcentration of uranium. The
modified resin was characterized by elemental analysis and infrared spectra.
Batch and column modes were applied. The newly designed resin quantitatively
sorbs uranium ion at pH 3 when the flow rate equals to 2 ml . min
-1 . The sorption capacity was 0.750 mmol . g-1 for
uranium ion, whereas its preconcentration factor was 200. The lower limit of
detection was 5 ng . ml-1 and its desorption was
effective with 5 ml of 3 mol . l-1 HCl or HNO3
prior to detection spectrophotometry. The modified resin was highly
ion-selective in nature even in the presence of large concentrations of
electrolyte or organic media, with a preconcentrating ability for uranium ion.
The modified resin was tested on its utility with synthetic, real and certified
ore samples, showed RSD values of <2% reflecting the accuracy and
reproducibility of the newly modified resin.</p>
</p> 相似文献
124.
Irradiation of acetone solutions of trans-chlordane (4a) and trans-nonachlor (4b) with UV light produces new half-cage photoisomers (5a or 6a and 5b or 6b, respectively) with bridging that differs from that of the photoisomers (2 and 8a) obtained from cis-chlordane (1b) and heptachlor epoxide (7). A new photoisomer (10) obtained from heptachlor epoxide is transformed into photoisomer 8a on further irradiation. Detailed PMR and 13C-NMR studies establish the structures of the new photoisomers and permit a decision between alternative formulations for the structures of the half-cage photoisomers of heptachlor epoxide and cis-chlordane, 相似文献
125.
Summary The acid-base properties of Solochrome Black P.V. have been studied with the object of applying it as a metallochromic or as a chromophoric indicator. The pK values of 4.1, 7.0 and 11 corresponding to the three steps of ionisation of the free acid were evaluated by aid of the relation between log (acid)/(salt) and pH values obtained during the course of the potentiometric titration of the free acid with a free base together with the E-pH relation. The molecular ratio of the magnesium-dye chelate and its mode of chelation are given.
Zusammenfassung Die Eigenschaften des Farbstoffs Solochrome Black P.V. werden im Hinblick auf seine Verwendung als Metalloder Farbindicator untersucht. Entsprechend den drei Dissoziationsstufen der freien Säure werden pK-Werte von 4,1, 7,0 und 11 gefunden. Diese werden mit Hilfe der Beziehungen zwischen log [Säure]/[Salz] und pH sowie zwischen E und pH ausgewertet. Bildung und Zusammensetzung des Mg-Farbstoffchelats werden näher untersucht.相似文献
126.
127.
Mercury(I), down to 3 ppm, has been accurately determined by direct titration with iodide or by back-titrating excess of iodide with mercury (II) using silver amalgam as the indicator electrode. The direct method and additional volumetric ones were applied to the rapid analysis of various mixtures involving mercury(I) with fair accuracy and precision. Analysis of Cr(VI)-Cr(III) mixtures involved potentiometric back-titration of excess iodide and of excess EDTA separately with mercury(II). Back-titration of excess iodide was successfully applied to the determination of hypochlorite. 相似文献
128.
Summary A rapid, reliable and accurate method for the determination of trivalent chromium, based on back titrating excess EDTA solutions in the presence of chromium versenate, with mercuric nitrate in alkaline media is given. By its aid amounts of chromium in the order of 50 micro- to 15 milligrams can be determined with fair accuracy. The method is applied for analysis of binary mixtures of chromium with thorium, copper(II), bismuth or mercury(II). 相似文献
129.
Yoshinori Fujimoto Miki Kimura Takeshi Terasawa Fathy A.M. Khalifa Nobuo Ikekawa 《Tetrahedron letters》1984,25(17):1805-1808
(24S,25S)- and (24R,25R)-24,26-Cyclocholesta-5,22E-dien-3β-ols (1a and 1b) were synthesized stereoselectively. Their 1H NMR comparison with natural glaucasterol (1) allowed to conclude that 1 possesses 24S,25S stereochemistry. 相似文献
130.
The effect of substituents on the stability of the complexes formed by reaction of Neville Winter's acid para-substituted azo dyes (p-chloro, methoxy, nitro, and sulfonic) is studied. Log K values for the complexes were determined spectrophotometrically. The p-methoxy and p-chloro chelates exhibited maximum and minimum stabilities, respectively, the methoxy group being electron repelling and chlorine electron withdrawing. Calculations applying Hammett and linear free energy equations indicate that copper in these chelates acts as a π-electron accepter and that such chelates exhibit coplanarity. 相似文献