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1.
C. Daum L. Hertzberger W. Hoogland R. Jongerius S. Peters P. Van Deurzen V. Chabaud A. Gonzalez-Arroyo B. Hyams H. Tiecke P. Weilhammer A. Dwurazny G. Polok M. Rozanska K. Rybicki M. Turala J. Turnau G. Ascoli H. Backer G. Blanar M. Cerrada H. Dietl J. Gallivan M. Glaubmann R. Klanner E. Lorenz G. Lütjens G. Lutz W. Männer U. Stierlin I. Blakey M. Bowler R. Cashmore J. Loken W. Spalding G. Thompson B. Alper C. Damerell A. Gillman C. Hardwick M. Hotchkiss F. Wickens ACCMOR Collaboration 《Zeitschrift fur Physik C Particles and Fields》1981,10(2):95-100
Muon electron pairs were detected in an Al multiplate spark chamber, exposed to a neutrino beam from the CERN PS. The leptons were not accompanied by other particles, except occasionally by protons. The background came mainly from muon associated π0 production, with one decay gamma lost. It was determined empirically, together with the small contribution from υ e reactions. For electron energies above 2 GeV the background is 5.7±1.5 events, whereas 18 (μe)-candidates have been observed. Hence the effect is established, with a rate of about 10?4 as compared to the muonic reactions above 3 GeV. Charm creation as the origin of this (μe)-production process is excluded; heavy neutral lepton production does not fit the kinematics observed. Instead the events are compatible with the two-body decay of an object with variable invariant mass of order 1 GeV, possibly resulting from axion interactions. 相似文献
2.
This paper presents the importance and usage of natural zeolites, which was recently recognized in the industry. Therefore, the grinding properties of natural zeolite were studied with the emphasis on a kinetic study in a ball mill. The experimental mill employed was laboratory sized, 200 mm diameter, 191 mm length, providing a total mill volume of 6000 cm3, with a total mass of 5.62 kg of steel balls of 25 mm diameter with a charge of 20% of the mill volume and with a rotation speed of 76 rpm. The breakage parameters were determined by using single sized feed fractions of ?850+600 μm, ?600+425 μm, and ?425+300 μm for the zeolite samples. The Si (specific rate of breakage) and Bi, j (primary breakage distribution) values were obtained for those feed size fractions in order to predict the product size distributions by simulation for comparison to the experimental data. From the experimental results, Si values increased as the feed sizes became coarser, i.e., the highest Si value was 0.85 min?1 for ?850+600 μm, while the lowest Si value was 0.65 min?1 for ?425+300 μm feed ground in the mill. The Bi, j values obtained for the zeolite sample were γ=0.84, ?=0.61, and β=4.25. The breakage parameters obtained showed that the zeolite is broken faster than quartz and slower than calcite and barite in terms of the aT values reported previously at the same experimental conditions. The simulations of the product size distributions of zeolite were in good agreement with the experimental data using a standard ball mill simulation program. The slowing‐down effect was also seen in the mill after 4 min. of grinding. 相似文献
3.
E. Alper Yildirim Xiaofei Fan-Orzechowski 《Computational Optimization and Applications》2006,33(2-3):229-247
We study the maximum stable set problem. For a given graph, we establish several transformations among feasible solutions
of different formulations of Lovász's theta function. We propose reductions from feasible solutions corresponding to a graph
to those corresponding to its induced subgraphs. We develop an efficient, polynomial-time algorithm to extract a maximum stable
set in a perfect graph using the theta function. Our algorithm iteratively transforms an approximate solution of the semidefinite
formulation of the theta function into an approximate solution of another formulation, which is then used to identify a vertex
that belongs to a maximum stable set. The subgraph induced by that vertex and its neighbors is removed and the same procedure
is repeated on successively smaller graphs. We establish that solving the theta problem up to an adaptively chosen, fairly
rough accuracy suffices in order for the algorithm to work properly. Furthermore, our algorithm successfully employs a warm-start
strategy to recompute the theta function on smaller subgraphs. Computational results demonstrate that our algorithm can efficiently
extract maximum stable sets in comparable time it takes to solve the theta problem on the original graph to optimality.
This work was supported in part by NSF through CAREER Grant DMI-0237415. Part of this work was performed while the first author
was at the Department of Applied Mathematics and Statisticsat Stony Brook University, Stony Brook, NY, USA. 相似文献
4.
Fatma M. Abdel-Gawad Yousry M. Issa Hussein M. Fahmy Hanan M. Hussein 《Mikrochimica acta》1998,130(1-2):35-40
Three simple, quick and sensitive spectrophotometric methods are described for the determination of ciprofloxacin. The methods are based on the reaction of this drug as ann-electron donor with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ), 7,7,8,8,-tetracyanoquinodimethane (TCNQ) andp-chloranil (CL) as -acceptors to give highly coloured complex species. The coloured products are quantitated spectrophotometrically at 460, 843 and 550 nm for DDQ, TCNQ and CL, respectively. Optimization of the different experimental conditions is described. Beer's law is obeyed in the concentration ranges 5–50, 1.5–15 and 20–200 g ml–1 ciprofloxacin, but the concentration ranges for best accuracy are 10–48, 2.5–15 and 35– 195 g ml–1 of drug for DDQ, TCNQ and CL, respectively. The relative standard deviations are less than 1.5%. Applications of the suggested methods to ciprofloxacin tablets are presented and compared with the USP method. The stability constants of the 11 DDQ and CL complexes were 1.086 × 104 and 2.581 × 104 lmol–1, respectively, whereas for the 12 TCNQ complex it was 3.62 × 1081. mol–1. 相似文献
5.
Mustafa Odabaolu idem Albayrak Reit
zkanca Fatma Zehra Aykan Peter Lonecke 《Journal of Molecular Structure》2007,840(1-3):71-89
Some new substituted polyhydroxy azo–azomethine compounds were prepared by reaction of tris(hydroxymethyl)aminomethane with (E)-2-hydroxy-5-(phenyldiazenyl) benzaldehyde and its substituted derivatives. The structures of azo and azo–azomethine compounds were determined by IR, UV–vis, 1H NMR and 13C NMR spectroscopic techniques, and/or X-ray diffraction studies. According to IR spectra, all azo–azomethine compounds adopt keto form in solid state. UV–vis analysis has shown the presence of keto–enol tautomerism in solution for all azo–azomethine compounds, except that for nitro substituted derivative, enol form is dominantly favored in solution. At the same time, above mentioned derivative compounds were studied in vitro for their antimicrobial properties. Among the phenylazosalicylaldehyde series compound tested, 4-phenylazosalicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde, 4-(2-chlorophenylazo)salicylaldehyde, 4-(4-fluorophenylazo)salicylaldehyde, 4-(3-chlorophenylazo)salicylaldehyde and 4-(4-ethylphenylazo)salicylaldehyde showed a weak antimicrobial activity only against gram positive bacteria. On the contrary, phenylazosalicylaldehyde series compounds were reacted tris(hydroxmethyl)aminomethane, that exhibited a strong antimicrobial activity against gram positive bacteria, yeast and mould. Moreover, while the 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol did not show an inhibition on tested microorganism, the addition of phenyldiazine groups to 2-{[1,3-dihydroxy-2-(hydroxymethyl)propan-2-ylimino]methyl}phenol resulted in a strong increases in antimicrobial activity. 相似文献
6.
Fatma I. Khattab M. M. Amer Nagiba Y. M. Hassan 《Journal of Thermal Analysis and Calorimetry》1982,25(2):367-375
Some sulphonamides are evaluated by means of thermal analysis. Use is made of their characteristic endothermic DTA peaks (melting peaks), where the area changes linearly with variations in the amount of sulphonamides. The method is suitable for the determination of 30–100 mg of sulphathiazole, sulphisomidine, sulphaguanidine, sulphacetamide sodium and sulphamethoxypyridazine with reasonable accuracy. As for sulphisoxazole, two peaks are used for its determination: an endothermic one to determine 30–100 mg, and an exothermic one to determine 6–30 mg.
Zusammenfassung Einige Sulphonamide wurden durch thermische Analyse bestimmt, wobei von der linearen Abhängigkeit der Fläche der charakteristischen endothermen DTA-Peaks (Schmelzpeaks) von der Menge der Sulphonamide Gebrauch gemacht wurde. Mit der Methode können 30–100 mg Sulphathiazol, Sulphisoimidin, Sulphaguanidin, Natrium-Sulphacetamid und Sulphamethoxypyridazin mit ausreichender Genauigkeit bestimmt werden. Bei der Bestimmung von Sulphisooxazol wurde ein endothermer Peak für Mengen von 30–100 mg und ein exothermer für geringere Mengen von 6–30 mg herangezogen.
. - ( ), . 30–100 , , , . , — 30 100 , — 6 30 .相似文献
7.
A catalyst system comprising palladium acetate-bidentate phosphine is effective for the cyclocarbonylation of o-iodoanilines with heterocumulenes at 70-100 degrees C for 12-24 h to give the corresponding 4(3H)-quinazolinone derivatives in good yields. Utilizing o-iodoaniline with isocyanates, carbodiimides, and ketenimines for the reaction, 2,4-(1H,3H)-quinazolinediones, 2-amino-4(3H)-quinazolinones and 2-alkyl-4(3H)-quinazolinones were obtained, respectively. The nature of the substrates including the electrophilicity of the carbon center of the carbodiimide, and the stability of the ketenimine, influence the product yields of this reaction. Urea-type intermediates are believed to be generated first in situ from the reaction of o-iodoanilines with heterocumulenes, followed by palladium-catalyzed carbonylation and cyclization to yield the products. 相似文献
8.
9.
Reaction of α-keto imines with the generated acetylcobalt tetracarbonyl occurs only at the carbon—nitrogen double bond to give β-keto amides. An unexpected by-product was formed in several instances. 相似文献
10.
The effect of addition of sodium anthranilate to 5 mM micellar solutions of gemini surfactant 1,4-bis(N-hexadecyl-N,N-dimethylammonium)butane dibromide is investigated by 1H NMR. The solubilization site of anthranilate anion near the micellar surface is inferred. In the micelles, the An− ions intercalate among the surfactant headgroups producing morphological changes. 相似文献