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51.
Michael R. Whittaker Carl N. Urbani Michael J. Monteiro 《Journal of polymer science. Part A, Polymer chemistry》2008,46(18):6346-6357
The new SET‐LRP (using Cu(0) powder for organic synthesis) was successfully used to produce well‐defined linear and star homo‐ and diblock‐copolymers of PMA, PSA, and P(MA‐b‐GA)n (where n = 1 or 4). The kinetic data showed that all SET‐LRP were first order and reached high conversions in a short period of time. The other advantage of using such a system is that the copper can easily be removed through filtration, allowing the production of highly pure polymer. The molecular weight distributions were well controlled with polydispersity indexes below 1.1 and the number‐average molecular weight close to theory, especially upon the addition of Cu(II)Br2/Me6‐TREN complex. The linear and star block copolymers were then hydrolyzed to produce the biocompatible amphiphilic P(MA‐b‐GA)n, where the glycerol side‐groups make the outer block hydrophilic. These blocks were micellized into water and found to have a Rg/RH equal to 0.8 and 1.59 for the liner and star blocks, respectively. This together with the TEM's supported that the linear blocks formed the classical core‐shell micelles, where as, the star blocks formed vesicles. We found direct support for the vesicle structure from a TEM where one vesicle squashed a second vesicle consistent with a hollow structure. Such vesicle structures have potential applications as delivery nanoscaled devices for drugs and other important biomolecules. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6346–6357, 2008 相似文献
52.
53.
Ricard V. Solé 《Complexity》2010,16(1):20-23
Chromosomes exhibit several features indicating that its spatiotemporal dynamics is self‐organized. It has been recently suggested that a negative correlation between genome size and mean chromosome number would also be a fingerprint of selforganization, related to how human language is organized at the level of words and syllables. However, the vast dominance of non‐coding DNA in eukaryotic genomes should prevent an interpretation of genome/chromosome size based on functional trade‐offs related to information storage and transmission. Moreover, the reported negative correlation is shown to be an inevitable consequence of the definitions of chromosome and genome length and it is thus unrelated to any type of special generative process. © 2010 Wiley Periodicals, Inc. Complexity 16: 20–23, 2010 相似文献
54.
Tatsuo Kimura 《Macromolecular rapid communications》2013,34(5):423-430
Exclusive organic templating of macroporous oxide films is reported by using non‐close and lose packing of spherical copolymer aggregates, in combination with facile control of condensation degree/density of inorganic oxide frameworks. Unique macroporous oxide films, mainly titania showing highly porous, crystalline, and versatile properties, can be fabricated with continuous design from unusual 3‐D net‐shape to tunable spherical macrostructures, which expands the preparation of other inorganic oxide films (silica, alumina, and zirconia) and possibly adapts the use of other assembled organic polymers. The macroporous structures are helpful for effective accommodation of bulky biomoleculeshigh and diffusivity of organic molecules (useful for photocatalysts). Unusual structural variation, expansion of spherical voids, is also observed, being useful for fine tuning of optical property. 相似文献
55.
Zhongzhi Zhang Shuigeng Zhou Yi Qi Jihong Guan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):507-513
The uniform recursive tree (URT) is one of the most important models and has been successfully applied to many fields. Here
we study exactly the topological characteristics and spectral properties of the Laplacian matrix of a deterministic uniform
recursive tree, which is a deterministic version of URT. Firstly, from the perspective of complex networks, we determine the
main structural characteristics of the deterministic tree. The obtained vigorous results show that the network has an exponential
degree distribution, small average path length, power-law distribution of node betweenness, and positive degree-degree correlations.
Then we determine the complete Laplacian spectra (eigenvalues) and their corresponding eigenvectors of the considered graph.
Interestingly, all the Laplacian eigenvalues are distinct. 相似文献
56.
F. Semboloni 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(3):295-301
We show that a hierarchical cities structure can be generated by a self-organized process which grows with a bottom-up mechanism,
and that the resulting distribution is power law. First we
analytically prove that the power law distribution satisfies the balance between the offer of the city and the demand of its
basin of attraction, and that the exponent in the Zipf's law corresponds to the multiplier linking the population of the central
city to the population of its basin of attraction. Moreover, the corresponding hierarchical structure shows a variable
spanning factor, and the population of the cities linked
to the same city up in the hierarchy is variable as well. Second a stochastic
dynamic spatial model is proposed, whose numerical results confirm the analytical
findings. In this model, inhabitants minimize the transportation cost, so that the greater
the importance of this cost, the more stable is the system in its microscopic aspect.
After a comparison with the existent methods for the generation of a
power law distribution, conclusions are drawn on the connection of hierarchical
structure, and power law distribution, with the functioning of the system of cities. 相似文献
57.
M. Gligor M. Ausloos 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):533-539
GDP/capita correlations are investigated in various time windows (TW), for the time interval 1990–2005. The target group of
countries is the set of 25 EU members, 15 till 2004 plus the 10 countries which joined EU later on. The TW-means of the statistical
correlation coefficients are taken as the weights (links) of a fully connected network having the countries as nodes. Thereafter
we define and introduce the overlapping index of weighted network nodes. A cluster structure of EU countries is derived from the statistically relevant eigenvalues and
eigenvectors of the adjacency matrix. This may be considered to yield some information about the structure, stability and
evolution of the EU country clusters in a macroeconomic sense. 相似文献
58.
A. Grabowski N. Kruszewska R. A. Kosiński 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,66(1):107-113
We study properties of five different social systems: (i) internet society of friends consisting of over 106 people, (ii) social network consisting of 3 × 104 individuals, who interact in a large virtual world of Massive Multiplayer Online Role Playing Games (MMORPGs), (iii) over
106 users of music community website, (iv) over 5 × 106 users of gamers community server and (v) over 0.25 × 106 users of books admirer website. Individuals included in large social network form an Internet community and organize themselves
in groups of different sizes. The destiny of those systems, as well as the method of creating of new connections, are different,
however we found that the properties of these networks are very similar.
We have found that the network components size distribution follow the power-law scaling form. In all five systems we have
found interesting scaling laws concerning human dynamics. Our research has shown how long people are interested in a single
task, how much time they devote to it and how fast they are making friends. It is surprising that the time evolution of an
individual connectivity is very similar in each system. 相似文献
59.
Zhongzhi Zhang Shuigeng Zhou Zhan Su Tao Zou Jihong Guan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):141-147
In this paper, we define a stochastic Sierpinski gasket, on the basis of which we construct a network called random Sierpinski
network (RSN). We investigate analytically or numerically the statistical characteristics of RSN. The obtained results reveal
that the properties of RSN is particularly rich, it is simultaneously scale-free, small-world, uncorrelated, modular, and
maximal planar. All obtained analytical predictions are successfully contrasted with extensive numerical simulations. Our
network representation method could be applied to study the complexity of some real systems in biological and information
fields. 相似文献
60.
以1978年改革开放以来人民教育出版社出版的5套高中化学教科书作为研究对象,梳理其物质结构内容的演变,发现近40年来高中化学教科书中物质结构内容选择呈钟摆现象,同时其内容组织的结构化理念日益清晰。此外,为新时期我国高中化学教科书的编写提供了一些建议。 相似文献