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排序方式: 共有162条查询结果,搜索用时 609 毫秒
1.
Martin Gilges Heribert Husmann Maria-Helen Kleemiß Stephan R. Motsch Gerhard Schomburg 《Journal of separation science》1992,15(7):452-457
Mixtures of several basic proteins have been used to test CZE capillaries with surfaces modified by new pretreatment procedures; the performance obtained has been compared with that achieved using capillaries treated by procedures described in the literature. It has been shown that addition of non-ionic polyvinylalcohols (PVA) to CZE buffer solutions deactivates even bare, i.e. untreated, fused silica surfaces and renders them suitable for separations of basic proteins. The performance obtained from such surfaces was comparable with that of capillaries modified by the more elaborate procedures of etching, silanol derivatization, and/or adsorptive coating (again with polymers). A home-made device is described which enables derivatization and coating reactions to be performed on fused silica capillaries under an inert atmosphere, i.e. one free from oxygen and water. 相似文献
2.
Avramopoulos A Reis H Li J Papadopoulos MG 《Journal of the American Chemical Society》2004,126(19):6179-6184
The electronic and vibrational contributions to the dipole moment, polarizabilities, and first hyperpolarizabilities of HArF are reported. These have been computed by using a series of systematically built basis sets and a hierarchy of computational methods. HArF has a very large first hyperpolarizability along the z axis. This has been rationalized by invoking the difference in the electronic structure between the ground and the first excited state. The argon fluorohydride has been recently derived and characterized. The present study provides complementary data for the understanding of the electronic structure of this interesting argon derivative. 相似文献
3.
Heribert Wiedemeier Asim K. Chaudhuri 《Monatshefte für Chemie / Chemical Monthly》1972,103(1):326-332
Zusammenfassung Durch Röntgenstrahlenbeugung mit Hilfe einer 190 mm Unicam-Hochtemperaturkamera wurde die thermische Ausdehnung von MnSe und MnSe2 von Zimmertemperatur bis 710° bzw. 522° C untersucht. Der thermische Ausdehnungskoeffizient wurde aus den Meßdaten nach der Methode der kleinsten Fehlerquadrate erhalten und beträgt für MnSe: =24,5·10–6°C–1 (94–450° C) und =14,3·10–6°C–1 (450–710° C). Die Ausdehnung von MnSe2 verläuft bis zum Bereich, in dem Zersetzung eintritt, linear. Die Methode der kleinsten Fehlerquadrate ergibt den Wert =20,0·10–6°C–1 (73–522° C).
Mit 2 Abbildungen
Herrn Prof.H. Nowotny gewidmet. 相似文献
High temperature X-ray studies of the thermal expansion ofMnSe andMnSe 2
The thermal expansion of MnSe and MnSe2 has been studied above room temperature up to 710° and 522° C, resp., by X-ray diffraction techniques using a 190 mm Unicam high temperature camera. The thermal expansion coefficients, , obtained from a linear least-squares analysis of the data are for MnSe: =24.5·10–6°C–1 (94–450° C) and =14.3·10–6°C–1 (450–710° C). The expansion of MnSe2 is linear up to the temperature range of decomposition. A least-squares analysis yields a value for of 20.0·10–6°C–1 (73–522° C).
Mit 2 Abbildungen
Herrn Prof.H. Nowotny gewidmet. 相似文献
4.
Determination of neutral oligosaccharide fractions from human milk by gel permeation chromatography. 总被引:1,自引:0,他引:1
A gel permeation chromatographic method for quantifying neutral oligosaccharide fractions from human milk has been developed. Oligosaccharides from monofucosyllactoses to trifucosyllacto-N-hexaoses were separated according to size on a Fractogel TSK HW 40 (S) column. Refractive index detection of monofucosyllactoses to difucosyllacto-N-tetraoses yielded a constant mass response factor of ca. 1 relative to glucose. After the addition of glucose as an internal standard, oligosaccharides were isolated from human milk by ethanol precipitation or two ultrafiltration procedures. The oligosaccharide concentrations found by the ultrafiltration procedures were significantly lower (significance level 0.05) than those determined by the ethanol precipitation procedure. 相似文献
5.
Alfred Deege Heribert Husmann Eduard Hübinger Frank Kobor Gerhard Schomburg 《Journal of separation science》1993,16(10):587-593
Complex mixtures of partially alkylated cyclodextrins can be analyzed by both HPLC and high temperature capillary GC. Because of the limited efficiency of LC, suitable analytical and preparative separations can be achieved only with systems of carefully optimized selectivity. Using LC it has been possible to isolate and purify single cyclodextrin species from very complex mixtures of components which contain unreacted hydroxyl groups in addition to the alkoxy groups. Analysis of the reaction mixtures and of fractions taken from LC separations can be performed with advantage by high resolution capillary GC at high temperatures between 300 and 400 °C. The thermal stability of partially alkylated cyclodextrins in high temperature GC is considerably increased by trimethylsilylation of the free hydroxyl groups. Fast atom bombardment mass spectrometry and proton NMR were used to identify species isolated from the preparative LC separations. 相似文献
6.
Über die gemeinsame Umsetzung von α-Mercaptoketonen mit Oxoverbindungen und α-Aminocarbonsäureestern
Zusammenfassung Bei der Umsetzung von -Mercaptoketonen mitSchiffschen Basen aus Glykokolläthylester und Oxoverbindungen (Aldehyden, Cyclohexanon) bzw. bei der gemeinsamen Einwirkung derSchiffschen Base-Komponenten Glykokolläthylester und Oxoverbindungen auf -Mercaptoketone entstehen in glatter Reaktion 4-Thiazolin-3-yl-essigsäureäthylester.Als cyclische Enamine lassen sich diese 4-Thiazoline mit Ameisensäure zu den entsprechenden beständigen Thiazolidinyl-3-essigsäureäthylestern hydrieren.Die 4-Thiazolin-3-yl-essigsäureäthylester, die in 2-Stellung monosubstituiert sind, erleiden beim Erhitzen auf etwa 150° Thermolyse, wobei es unter Abspaltung von Essigsäureäthylester zur Bildung von Thiazolen kommt.
60. Mitt.:F. Asinger, W. Schäfer, H. Kersten undA. Saus, Mh. Chem.98, 1841 (1967).
Teil der DiplomarbeitC. Dudeck, Techn. Hochschule Aachen, 1967. 相似文献
-Mercapto ketones react with aldehydes (or cyclohexanone) and esters of -amino acids (or their hydrochlorides) or with theSchiff bases formed by these compounds to form esters of 4-thiazolin-3-ylacetic acids. These esters can be hydrogenated with formic acid to the corresponding thiazolidines.Esters of 4-thiazolinylacetic acids which have a H atom in position 2, can be pyrolysed by heating at about 150° to form the corresponding thiazoles and alkyl acetate. These reactions are illustrated for the case of 2-mercaptopentan-3-on as -mercapto ketone, glycinethylester as amine component and various aldehydes or cyclohexanone as oxo compound.
60. Mitt.:F. Asinger, W. Schäfer, H. Kersten undA. Saus, Mh. Chem.98, 1841 (1967).
Teil der DiplomarbeitC. Dudeck, Techn. Hochschule Aachen, 1967. 相似文献
7.
F. Asinger H. Offermanns A. Saus C. Dudeck D. Neuray E. Wilms 《Monatshefte für Chemie / Chemical Monthly》1973,104(1):118-136
Zusammenfassung Die Darstellung einigerMannichbasen (3 a-f) bzw.Mannich-basen-hydrochloride (2 a-f) und zahlreicher s-Triazin-Derivate (4 a-d, 5 a–m, 6 a–w, 7 a–e, 8 a–d, und9 a–l) auf Basis des unsubstituierten Thiomorpholins (1 a) sowie C-mono-[2-Methylthiomorpholin (1 b) und 2-Äthylthiomorpholin (1 c)] und C-dialkylierter Thiomorpholine [2-Methyl-3-äthylthiomorpholin (1 d)] wird beschrieben.
HerrE. Wilms dankt der Deutschen Texaco AG. für die Gewährung eines Stipendiums herzlichst. 相似文献
Concomitant action of elementary sulfur and gaseous ammonia upon ketones, LXXIX: On the reactivity of alkyl substituted thiomorpholines, I
The preparation of someMannichbases (3 a-f) andMannich base hydrochlorides (2 a-f), resp., and numerous s-triazine derivatives (4 a-d, 5 a–m, 6 a–w, 7 a–e, 8 a–d, and9 a–l) based upon unsubstituted thiomorpholine (1 a) as well as C-mono-[2-methylthiomorpholine (1 b) and 2-ethylthio-morpholine (1 c)] and C-dialkylated thiomorpholines [2-methyl-3-ethylthiomorpholine (1 d)] is described.
HerrE. Wilms dankt der Deutschen Texaco AG. für die Gewährung eines Stipendiums herzlichst. 相似文献
8.
The temperature-composition phase diagram of the HgTe?HgI2 pseudobinary system on the HgTe rich side
The temperature-composition phase diagram of the HgTe? HgI2 system was determined from 0 to 45 Mol-% HgI2 between 25 and 670°C using Debye-Scherrer powder X-ray diffraction techniques and differential thermal analysis. Solid solutions of HgTe and HgI2 with the cubic, zinc blende-type structure exist above 300°C, having a maximum solubility of 11.7 ± 0.8 Mol-% HgI2 in HgTe at 501 ± 5°C. The known monoclinic compound Hg3Te2I2 is formed by a peritectic reaction upon cooling at 501 ± 5°C, with the peritectic point at approximately 37 ± 4 Mol-% HgI2. 相似文献
9.
Gerhard Schomburg Alfred Deege Heike Hinrichs Eduard Hübinger Heribert Husmann 《Journal of separation science》1992,15(9):579-584
Methods of alkylation of α-, β- and γ-cyclodextrins have been optimized with regard to the parameters of reaction, degree of alkylation and yields. The analysis of the reaction mixtures and of the isolated single species has been performed by high temperature GC and HPLC. The phase systems of the preferably applied HPLC have been carefully adjusted by variation of both the stationary and mobile phases to the very different hydrophobicities of the various alkylated CD species which have been synthesized. Several partially or fully alkylated CD species were isolated from preparative scale HPLC separations in high purity. 相似文献
10.
Knudsen effusion studies of the sublimation of polycrystalline SnS, prepared by annealing and chemical vapor transport, have been performed employing vacuum micro-balance techniques in the temperature range 733–944 K and at pressures ranging from about 6 × 10?3 to 11 Pa.The third-law heats of sublimation and second-law entropy of reaction SnS(s) = SnS(g) were determined to be ΔH0298 = 220.4 ± 3.0 kJ mole? and ΔS0298 = 162.4 ± 4.5 J K?1 mole?1. From these data the standard heat of formation and absolute entropy of SnS(s) were calculated to be ?102.9 ± 4.0 kJ mole?1 and 79.9 ± 6.0 J K?1, respectively. 相似文献