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41.
Renate Obenaus und Dietrich Mücke 《Fresenius' Journal of Analytical Chemistry》1964,201(6):428-435
Zusammenfassung Es wird eine indirekte Methode zur Bestimmung des spezifischen Kaliumpermanganatverbrauches von Huminsäuren beschrieben. Die Huminsäuren werden mit einer 0,01 m Blei(II)-nitratlösung gefällt und der gebildete Pb-Huminsäure-Niederschlag ausgewogen. Aus dem PbGehalt und dem Kaliumpermanganatverbrauch des Pb-HuminsäureKomplexes ergibt sich der Kaliumpermanganatverbrauch pro Milligramm Huminsäure. Im Gegensatz zu Eisen(III)-chlorid verändert Blei(II)nitrat die Oxydierbarkeit der Huminsäuren nicht, so daß indirekt und direkt bestimmter spezifischer Kaliumpermanganatverbrauch übereinstimmen.Es wurden die spezifischen Kaliumpermanganatverbrauchswerte von zwei Huminsäuren bekannter Oxydierbarkeit (Fluka-Humussäure und Moorwasser-Huminsäure) und von Huminsäuren aus 3 natürlichen Wässern bestimmt. Die Fehlerbereiche der Mittelwerte betragen bei den Modellsubstanzen (je 15 Analysenwerte) ±4% (Huminsäure Fluka) bzw. ±3% (Moorwasser-Huminsäure) und bei den praktischen Analysen ±4% ±11% bzw. ±7% des jeweiligen Mittelwertes.
Wir danken Frl. Roswitha Raspe und Frau Helga Boje für fleißige technische Mitarbeit. 相似文献
Summary An indirect method for the determination of the specific permanganate consumption of humic acids is described. The humic acids are precipitated by 0,01 M lead(II)nitrate and the precipitate of lead-humic acid is weighed. The permanganate consumption per mg humic acid results from the lead-content and the permanganate consumption of the lead-humic acid complex. As opposed to ferric chloride lead(II) nitrate does not change the oxidizability of humic acids; hence, indirectly and directly determined permanganate consumption equal each other. — The values of the specific permanganate consumption of two humic acids of known oxidizability and of three samples of humic acids isolated from natural water-sources are determined. The limit of error of the mean values is between ±3% and ±11%.
Wir danken Frl. Roswitha Raspe und Frau Helga Boje für fleißige technische Mitarbeit. 相似文献
42.
Dietrich Braun 《Angewandte Chemie (International ed. in English)》1976,15(8):451-459
One of the topical problems of macromolecular chemistry is the question of the extent to which macromolecules in solution or in the amorphous solid state can engage in mutual interpenetration. The present article is concerned primarily with recent investigations on cross-linking copolymerization and with inter-and intramolecular reactions of polymers as a contribution to the study of molecular shape. 相似文献
43.
44.
With the aid of thinlayer chromatography mixtures of tetraorganotin compounds containing no polar groups can be separated and identified if they differ in the number of phenyl groups per molecule or in the nature of their aliphatic residues (alkyl or allyl). For analytical purposes mixtures of 80% hexane and 20% benzene by volume are suitable as mobile phase. For preparative purposes (requiring multiple development) pure hexane or hexane containing 10 to 20% benzene by volume are best suited as mobile phase, where the amount of hexane depends on the problem of separation at hand. The Rf values of the mobile phases vary linearly with the number of the phenyl groups x and decrease with increasing x. The straight lines connecting the Rf values cross at x=4 (tetraphenyltin). Dithizone and silver nitrate are suitable spray reagents for organotin compounds. By spraying the plates with dithizone tetra-, tri-, and di-organotin compounds can be immediately distinguished on the basis of the ensuing colourations. With silver nitrate allyltin compounds and polystannanes can be distinguished from alkyltin compounds; tetra-phenyltin is not coloured by this reagent. 相似文献
45.
Wolfgang Frenzel Annette Rauterberg-Wulff Dietrich Schepers 《Fresenius' Journal of Analytical Chemistry》1995,353(2):123-127
Non-suppressed ion chromatography (NSIC) has been optimized to permit the determination of chloride, nitrate and sulfate in the low mg/l concentration range within 3 min. Using conductometric detection the extraneous (positive) injection peak was found to adversely affect the early eluting chloride signal when samples with high amounts of total cations are analyzed. The serial arrangement of a downstream potentiometric detector with a chloride ion selective electrode, which does not respond to other alterations of the composition of the eluent than the change in chloride concentrations, is shown to be suitable for interference-free, sensitive and reliable chloride evaluation. Application of the proposed system to the determination of chloride in extracts of filter collected airborne particulates revealed (for those samples that could be evaluated by both detection methods) high precision and no systematic deviations between conductometric and potentiometric detection.Dedicated to Professor Dr. Peter Brätter on the occasion of his 60th birthday 相似文献
46.
Some laws in physics describe the change of a flux and are represented by parabolic equations of the form (*) \documentclass{article}\pagestyle{empty}\begin{document}$$\frac{{\partial u}}{{\partial t}}=\frac{\partial}{{\partial x_j }}(\eta \frac{{\partial u}}{{ax_j}}-vju),$$\end{document} j≤m, where η and vj are functions of both space and time. We show under quite general assumptions that the solutions of equation (*) with homogeneous Dirichlet boundary conditions and initial condition u(x, 0) = uo(x) satisfy The decay rate d > 0 only depends on bounds for η, v and G § Rm the spatial domain, while the constant c depends additionally on which norm is considered. For the solutions of equation (*) with homogeneous Neumann boundary conditions and initial condition u0(x) ≥ 0 we derive bounds d1u1 ≤ u(x, t) ≤ d2u2, Where di, i = 1, 2, depend on bounds for η, v and G, and the ui are bounds on the initial condition u0. 相似文献
47.
Hans-Detlev Gilsing Jürgen Angerer Dietrich Prescher 《Monatshefte für Chemie / Chemical Monthly》2002,133(8):1147-1155
Summary. The synthesis of two oxidized metabolites of bis-(2-ethylhexyl)-phthalate is described. The target structures were obtained
by esterification of the appropriate alcohol carrying a protected hydroxy group with phthalic anhydride, followed by deprotection
and further oxidation.
Received February 26, 2002. Accepted March 6, 2002 相似文献
48.
H. H. Deubler K. Lekkas P. Sperr K. Dietrich 《Zeitschrift für Physik A Hadrons and Nuclei》1978,284(2):237-244
The process of instantaneous fission in deep inelastic collisions is investigated in a classical model. Kinetic energies and angular distributions of the fragments are calculated for the proposed reaction Pb+U atE cm inc =750 MeV; an experimental setup for the separation of the fragments originating from instantaneous fission from the fragments of thermal fission is explained. We also discuss fusion following instantaneous fission as a mechanism for the production of superheavy elements and arrive at rather promising estimates. 相似文献
49.
Highly pure chromium(II) acetate, was obtained from chromium powder and anhydrous acetic acid in the presence of a small amount of acetylhalide. CrII acetate reacts with acetyl halide in anhydrous acetic acid to sesquisolvates like CrCl2 · 3/2 CH3COOH. If one equivalent of alkali acetate or an organic nitrogen base is added to solutions of CrII acetate in acetyl halide/acetic acid mixtures, trihalochromates(II) are precipitated which are hexagonal in structure, except the ammonium and the potassium salt. With two equivalents of alkali or ammonium acetate tetrachlorochromates(II) of cesium, rubidium and ammonium are precipitated. They are tetragonal in structure (K2NiF4 type). Using pyridinium acetate with various mixtures of acetyl bromide and acetic acid, only the solvates (PyH)3(CrBr5) · 2CH3COOH is formed. 相似文献
50.
The large number of known stable compounds in which phosphorus has a low coordination number makes it clear that such compounds can no longer be regarded as “exotic” in main group chemistry. While the rich chemistry of P? C multiply bonded systems makes clear their affinity to their organic congeners, iminophosphanes in particular are also of increasing importance. The linkage of a phosphinidine fragment with an imine fragment via a multiple bond gives rise to a class of compounds with an unusually wide range of structural types. This in turn leads to a broad spectrum of chemical behavior which makes iminophosphanes extremely useful synthetic building blocks in organoelement chemistry. 相似文献