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Vitali Vogel Jean‐Franois Gohy Bas G. G. Lohmeijer Jacomina A. Van Den Broek Winfried Haase Ulrich S. Schubert Dieter Schubert 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3159-3168
In aqueous solutions, amphiphilic block copolymers in which a polystyrene (PS) segment is connected to a poly(ethylene oxide) (PEO) block via a bis(2,2′:6′,2″‐ terpyridine ruthenium) complex can form micelles. Such micelles of the protomer type PS20‐[Ru]‐PEO70, according to the preparation procedure representing frozen micelles, were studied by sedimentation velocity and sedimentation equilibrium analysis in an analytical ultracentrifuge and by transmission electron microscopy, with different techniques applied for the sample preparation. The particles obtained were surprisingly multifarious in size. In ultracentrifugation experiments performed at relatively low salt concentrations, the distributions of the sedimentation coefficient s20,w showed a pronounced peak at 9.6 S and a broad, only partly separated second peak around 14 S. The molar mass of the particles at the peak was around 430,000 g/mol, corresponding to an aggregation number of approximately 85. The average hydrodynamic diameter of the particles in the peak fraction was approximately 13 nm. In electron micrographs of negatively stained samples, spheres of diameters between 10 and 25 nm were the most abundant particles, but larger ones with a wide size range were also visible. The latter particles apparently were composed of smaller ones. The data from both sedimentation analysis and electron microscopy showed that (1) the studied compound formed primary micelles of diameters around 20 nm and (2) the primary micelles had a tendency toward aggregation. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3159–3168, 2003 相似文献
14.
Winfried Kohnen 《Proceedings of the American Mathematical Society》2007,135(4):997-999
We shall show that the eigenvalues of a Hecke eigenform of integral weight and genus 2 not contained in the Maass space change signs infinitely often.
15.
We investigate traces of functions, belonging to a class of functions with dominating mixed smoothness in ℝ3, with respect to planes in oblique position. In comparison with the classical theory for isotropic spaces a few new phenomenona
occur. We shall present two different approaches. One is based on the use of the Fourier transform and restricted to p = 2. The other one is applicable in the general case of Besov-Lizorkin-Triebel spaces and based on atomic decompositions. 相似文献
16.
Wendelin Winfried Knotz Florian Schramm Hans-Wolfgang 《Monatshefte für Chemie / Chemical Monthly》1975,106(1):159-168
Monatshefte für Chemie - Chemical Monthly - Primary, secondary and tertiary aliphatic alcohols quickly react with 1-chloromethyl-isatin (1) to give good yields of alkoxymethylisatines4-novel... 相似文献
17.
Hägele Gerhard Boenigk Winfried Engelhardt Michael 《Analytical and bioanalytical chemistry》1985,320(7):676-677
Analytical and Bioanalytical Chemistry - 相似文献
18.
K. Dimroth A. Berndt F. Br A. Schweig R. Volland 《Angewandte Chemie (International ed. in English)》1967,6(1):34-40
The distribution of the unpaired electron over the oxygen and the 24 carbon atoms in the free 2,4,6-triphenylphenoxy radical was determined by electron spin resonance spectroscopy and quantum-mechanical approximation methods. The hyperfine splitting was evaluated with the aid of the spectra of triphenylphenoxyls deuterated in some or all of the substituent phenyl groups. The results of the quantum-mechanical approximations were checked by recording the ESR spectra of triphenylphenoxyls labeled with 13C in positions 1,2,3, or 4 of the central ring. The spin density distribution permits a first discussion of the 17O-coupling constants of correspondingly labeled triphenylphenoxyl and other organic free radicals. 相似文献
19.
Winfried Haumesser Werner Gerlach und Claus -Henning Röder 《Fresenius' Journal of Analytical Chemistry》1977,287(4-5):291-295
Zusammenfassung Eine direkte maßanalytische Methode zur Bestimmung diverser Carbamate wird beschrieben. Die potentiometrische Titration mit käuflicher Tetra-n-butylammoniumhydroxid-Lösung, verdünnt mit Propanol-(2), ist bequem durchzuführen, und die erhaltenen Titrationskurven gestatten eine korrekte Auswertung.
Direct volumetric determination of carbamates as very weak acids
Summary A volumetric procedure for the determination of some carbamates is described. The potentiometric titration with commercial tetra-n-butylammonium hydroxide solution diluted with propanol-(2) is convenient and the obtained titration curves permit a correct calculation.相似文献
20.
When using a direct determination procedure with graphite-furnace a.a.s. (e.t.a.a.s.), it is sufficient to make an addition of nitric acid in order to arrive at the optimal reduction of the spectral background. A “matrix modifier” (NH4NO3, (NH4)2HPO4) produces a background which often cannot be compensated completely. Detection limits of the direct determination technique are: Cd 0.1, Co 8, Cu 4, Ni 5, Pb 2 and Tl 3 (μg l?1). A similar power of detection can be achieved as with flame-a.a.s. due to a preceding preconcentration step (trace adsorption on highly dispersed silicic acid). After preconcentration and determination with e.t.a.a.s., the detection limits are: Cd 0.002, Co 0.1, Cu 0.05, Ni 0.09, Pb 0.09 and Tl 0.06 (μg l?1). The trace concentrations in urine of healthy persons were found to be: Cd 0.2–0.8, Co ? 0.1, Cu 4–10, Ni 1–3, Pb 6–10 and Tl 0.7–1.3 (μg l?1). Direct e.t.-a.a.s. is, therefore, found to be suitable for the determination of Cd, Cu and Pb. For the determination of Co, Ni and Tl concentrations, a preconcentration is required. Cobalt was not found in any of the urine samples at the limit of detection of 0.1 μg l?1. 相似文献