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21.
Results are presented on the efficient spectral manipulation of uniform and chirped Bragg reflectors inscribed in microstructured optical fibers utilizing short lengths of ferrofluids infiltrated in their capillaries. The infiltrated ferrofluidic defects can generate either parasitic reflection notch features in uniform Bragg reflectors of up to 80% visibility and ~0.1 nm spectral shift or tunability of the bandwidth and strength reflection up to 100% when introduced into chirped gratings. Spectra are presented for different spatial positions and optical characteristics of the ferrofluidic section. 相似文献
22.
Reverse scans in square wave voltammetry (SWV) leading to the regeneration of the substance initially present in solution are studied. Widths and peak potentials of waves in SWV performed with both negative and positive potential scans allow us to determine easily the kinetic parameters of a slow electrochemical reaction. The theoretical treatment is verified using the U(V)–U(VI) system in a carbonate medium, which has already been studied by Krulic, Fatouros and Chevalet [J. Electronal. Chem. 251 (1988) 151]. 相似文献
23.
24.
Thomas B. Goudoulas Eleftherios G. Kastrinakis Stavros G. Nychas 《Rheologica Acta》2007,46(3):357-367
Aspects of dense lignite–water slurries (LWS) rheology were investigated using controlled stress and controlled strain rheometers
with parallel disks and Couette geometries. During the preparation of the slurries, the achieved solids volume fractions were
up to 0.425 and the particle size distributions were polydispersed with sizes up to 300 μm. In the ascending parts of consecutive
flow loops, a slope transition of the flow curve was observed and studied in relation to the solids volume fraction. The obtained
results with the different geometries and rheometers were qualitatively the same. By following the model proposed by Cheng
(Rheol Acta 42:372–382, 2003) for thixotropic fluids, and taking into account the yield stress appearance, a suitable correlation for LWS is proposed,
which is consistent with the experimental flow curves. 相似文献
25.
Thomas B. Goudoulas Eleftherios G. Kastrinakis Stavros G. Nychas 《Rheologica Acta》2003,42(1-2):73-85
An investigation of the rheological properties of dense lignite-water suspensions is reported here in order to evaluate the
parameters that affect the rheology of these suspensions. Different types of particle size distributions were achieved via
wet grinding with particle sizes down to 1 μm. Polyelectrolytes and surfactants were used to improve the stability and rheology
of suspensions. The achieved solid volume fraction, φ, with acceptable rheological behavior was 0.45, while the ratio of φ/φ
m
was close to 0.85; φ
m
is the maximum solid volume fraction. Various types of flow tests were performed on lignite-water suspensions with various
preshear times and stress levels. Typical shear rates varied in the range between 10–2 to 102 s–1. The low shear behavior was found to be quite different from the high shear behavior for the most concentrated suspensions,
with a plateau value at low shear rates indicating the appearance of a yield stress. These plateau values, however, depend
on shear history, which is responsible for the development of different structures in the sample. The viscosity curves corresponding
to the ascending and descending parts of the flow curve were found to be different; these flow curve parts can be described
either by well established models or by modified ones. The non-Newtonian time dependent behavior of the lignite-water suspensions
is attributed to the high value of the ratio φ/φ
m
, the polydispersity of the particle size distribution, and the non-spherical shape of the lignite particles. 相似文献
26.
Nikolaos Politakos Stavros Azinas Sergio Enrique Moya 《Macromolecular rapid communications》2016,37(7):662-667
Polymer brushes have a large potential for controlling properties such as surface lubrication or wetting through facile functionalization. Polymer chemistry, chain density, and length impact on the wetting properties of brushes. This study explores the use of diblock copolymer brushes with different block length and spatial arrangement of the blocks to tune surface wettability. Block copolymer brushes of the polyelectrolyte [2‐(methacryloyloxy)ethyl] trimethylammonium chloride (PMETAC) with a contact angle of 17° and a hydrophobic block of 1H, 1H, 2H, 2H‐perfluorodecyl Acrylate (PPFDA) with a contact angle of 130° are synthesized by RAFT polymerization. By changing the sequence of polymerization either block is synthesized as top or bottom block. By varying the concentration of initiator the length of the blocks is varied. Contact angle values with intermediate values between 17° and 130° are measured. In addition, by changing solvent pH and in presence of a different salt the contact angle of the copolymer brushes can be fine tuned. Brushes are characterized by atomic force microscopy, Raman confocal microscopy, and X‐ray photoelectron spectroscopy.
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28.
Weakly quasi-threshold graphs form a proper subclass of the well-known class of cographs by restricting the join operation. In this paper we characterize weakly quasi-threshold graphs by a finite set of forbidden subgraphs: the class of weakly quasi-threshold graphs coincides with the class of {P 4, co-(2P 3)}-free graphs. Moreover we give the first linear-time algorithm to decide whether a given graph belongs to the class of weakly quasi-threshold graphs, improving the previously known running time. Based on the simplicity of our recognition algorithm, we can provide certificates of membership (a structure that characterizes weakly quasi-threshold graphs) or non-membership (forbidden induced subgraphs) in additional ${{\mathcal O}(n)}$ time. Furthermore we give a linear-time algorithm for finding the largest induced weakly quasi-threshold subgraph in a cograph. 相似文献
29.
30.
Zusammenfassung Chromatographische Versuche zeigen, daß die Zwischenprodukte der Kjeldahlisierung des Anilins mit denen der Anilinschwarz-Bildung verwandt sind. Die Elementaranalyse von Polymerisationsprodukten dieser Zwischenstoffe weist darauf hin, daß es sich um sulfonierte Oxyemeraldine handelt. Kinetische Versuche und Überlegungen führen zu dem Ergebnis, daß alle diese Zwischenstufen erst durchlaufen werden, nachdem Anilin zu Sulfanilsäure sulfoniert worden ist, wobei ein der weiteren Oxydation vorgelagertes Gleichgewicht erreicht wird.
Emil Abel zum 80. Geburtstag zugeeignet. 相似文献