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71.
This paper addresses the problem of scheduling jobs in a single machine with sequence dependent setup times in order to minimize
the total tardiness with respect to job due dates. We propose variants of the GRASP metaheuristic that incorporate memory-based
mechanisms for solving this problem. There are two mechanisms proposed in the literature that utilize a long-term memory composed
of an elite set of high quality and sufficiently distant solutions. The first mechanism consists of extracting attributes
from the elite solutions in order to influence the construction of an initial solution. The second one makes use of path relinking
to connect a GRASP local minimum with a solution of the elite set, and also to connect solutions from the elite set. Reactive
GRASP, which probabilistically determines the degree of randomness in the GRASP construction throughout the iterations, is
also investigated. Computational tests for instances involving up to 150 jobs are reported, and the proposed method is compared
with heuristic and exact methods from the literature. 相似文献
72.
The purpose of this paper is to present an example of nonisomorphic involution semigroups which are globally isomorphic,
i.e. which have isomorphic power algebras (elements of which are the nonempty subsets of the original algebras). As an immediate
consequence, we obtain that (involution) semirings are not globally determined.
September 7, 1999 相似文献
73.
A weak characterisation of the Delaunay triangulation 总被引:1,自引:0,他引:1
Vin de Silva 《Geometriae Dedicata》2008,135(1):39-64
We consider a new construction, the weak Delaunay triangulation of a finite point set in a metric space, which contains as a subcomplex the traditional (strong) Delaunay triangulation. The two simplicial complexes turn out to be equal for point sets in Euclidean space, as well as
in the (hemi)sphere, hyperbolic space, and certain other geometries. There are weighted and approximate versions of the weak
and strong complexes in all these geometries, and we prove equality theorems in those cases also. On the other hand, for discrete
metric spaces the weak and strong complexes are decidedly different. We give a short empirical demonstration that weak Delaunay
complexes can lead to dramatically clean results in the problem of estimating the homology groups of a manifold represented
by a finite point sample.
相似文献
74.
Laurie J. Burn Jean-Pierre Candelone Graeme R. Burton Vin I. Morgan Sungmin Hong 《Analytica chimica acta》2009,634(2):228-20
Measurements of Pb isotope ratios in ice containing sub-pg g−1 concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g−1 and fg g−1 concentrations in Polar ice, were also measured. The final blank amounted to 0.2 ± 0.2 pg of Pb with 206Pb/207Pb and 208Pb/207Pb ratios of 1.16 ± 0.12 and 2.35 ± 0.16, respectively, 1.5 ± 0.4 pg of Ba and 0.6 ± 2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only ∼5%, ∼14% and ∼0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g−1, 0.3 pg g−1 and 2.3 fg g−1. Uncertainties in the Pb isotopic ratio measurements were degraded by only ∼0.2%. 相似文献
75.
In this paper spaces of entire functions of Θ-holomorphy type of bounded type are introduced and results involving these spaces are proved. In particular, we “construct an algorithm” to obtain a duality result via the Borel transform and to prove existence and approximation results for convolution equations. The results we prove generalize previous results of this type due to B. Malgrange: Existence et approximation des équations aux dérivées partielles et des équations des convolutions. Annales de l’Institute Fourier (Grenoble) VI, 1955/56, 271–355; C. Gupta: Convolution Operators and Holomorphic Mappings on a Banach Space, Séminaire d’Analyse Moderne, 2, Université de Sherbrooke, Sherbrooke, 1969; M. Matos: Absolutely Summing Mappings, Nuclear Mappings and Convolution Equations, IMECC-UNICAMP, 2007; and X. Mujica: Aplicações τ (p; q)-somantes e σ(p)-nucleares, Thesis, Universidade Estadual de Campinas, 2006. 相似文献
76.
Vinícius Albano Araújo S?nia Nair Báo Jane Moreira Clóvis Andrade Neves José Lino-Neto 《Micron (Oxford, England : 1993)》2010,41(4):306-311
The Hemiptera order is currently divided into four suborders. Among them the Auchenorrhyncha suborder is considered to be paraphyletic. Morphology of insect spermatozoa has provided promising characteristics that can be used for phylogenetic inference. In this study, Aethalion reticulatum (Aethalionidae) spermatozoa were examined by light and electron microscopy. The head of the spermatozoa is composed of an acrosome and a nucleus. The nucleus is linear and filled with compact chromatin but has electron-lucid spaces. The centriole adjunct initiates parallel to the nucleus and terminates in the region anterior to the mitochondrial derivatives. Flagella consist of an axoneme, two mitochondrial derivatives and two accessory bodies and the axoneme has the typical 9 + 9 + 2 microtubule pattern. The mitochondrial derivatives are symmetric. The accessory bodies are long and are shaped like a half moon when viewed from a cross-section. The presence of accessory bodies differs from other species of Cicadomorpha previously studied. Spermatozoa morphology of other Auchenorrhyncha families can reveal synapomorphies and contribute to systematics of the suborder. 相似文献
77.
L. Guyon K.M. Hajek F. Courvoisier V. Boutou R. Nuter A. Vinçotte S. Champeaux L. Bergé J.-P. Wolf 《Applied physics. B, Lasers and optics》2008,90(3-4):383-390
Multiple filamentation in a high concentration solution of coumarin 153 in ethanol is studied. It is shown that the output
filament pattern may be controlled by placing diffractive elements (circular aperture, edge) in the input beam path. These
filaments are formed in highly reproducible arrays along diffraction maxima corresponding to the element used. Experimental
results are supported by numerical simulations. They confirm that diffraction-induced intensity gradients swamp modulational
instability on the wavefront, forcing filaments to form along diffraction maxima. The effect of two-photon absorption by coumarin
molecules on filament patterns is also investigated over a range of dye concentrations. Control results are finally exploited
in the production of arrays of localized lasing filaments, which should open novel applications. The resultant lasing sources
are mutually coherent and highly repeatable from shot-to-shot, as is shown by their far-field interference patterns.
PACS 42.65.Tg; 52.38.Hb; 42.68.Ay 相似文献
78.
do Nascimento C Issa JP Iyomasa MM Regalo SC Siéssere S Pitol DL de Oliveira Wolga N Pedrazzi V 《Micron (Oxford, England : 1993)》2008,39(7):868-874
Mineral trioxide aggregate (MTA) is a powder aggregate containing mineral oxides with a good biological action and may facilitate the regeneration of the periodontal ligament and formation of bone. Calcium hydroxide demonstrates antibacterial properties, enhances tissue dissolution, and induces bone formation. The objective of this study was to evaluate the MTA in the bone healing process and verify if the calcium hydroxide P.A. can improve and accelerate this process. It was used forty male Wistar rats, which were divided into two groups, considering or not the use of calcium hydroxide P.A. solution before treatment. Thus, each one of these groups was divided in four groups with five animals each, according to the treatment and the defect filled by: animal's coagulum, monoolein gel, MTA in aqueous solution, and MTA combined with monoolein gel. After 10 days, the animals were perfused and the right hemimandibles removed for histological analysis. Statistical analysis of the data showed significant difference between all analyzed groups when it was made comparisons using or not calcium hydroxide P.A. (p<0.0001). There was found statistical difference between the groups that was inserted or not MTA, independently the calcium hydroxide application (p<0.05). Results showed that the MTA used was able to induce bone regeneration and had its action optimized when combined to calcium hydroxide P.A. 相似文献
79.
Erin W. Chambers Vin de Silva Jeff Erickson Robert Ghrist 《Discrete and Computational Geometry》2010,44(1):75-90
Fix a finite set of points in Euclidean n-space
\mathbbEn\mathbb{E}^{n}
, thought of as a point-cloud sampling of a certain domain
D ì \mathbbEnD\subset\mathbb{E}^{n}
. The Vietoris–Rips complex is a combinatorial simplicial complex based on proximity of neighbors that serves as an easily-computed
but high-dimensional approximation to the homotopy type of D. There is a natural “shadow” projection map from the Vietoris–Rips complex to
\mathbbEn\mathbb{E}^{n}
that has as its image a more accurate n-dimensional approximation to the homotopy type of D. 相似文献
80.
The concentration of silica in water samples from the desert area of Xinjiang, N. W. China, has been measured by colorimetry with ammonium molybdate. The observed pattern of dependence of the concentration of silica on the concentration of sodium ion (Na+) in the water samples is consistent with the pattern obtained by experiments on in-vitro dissolution of silica gel in sodium chloride (NaCl) solution. This indicates that the dissolution of silica in the hydrologic system in this area depends on the concentration of Na+. Calcium ion (Ca2+), which is known to play an important role on the dissolution of silica on the basis of in-vitro experiments, was observed to take little part in the dissolution of silica in actual natural water samples. This implies that the Ca2+ is bound to the hydrogen carbonate anion or that the Ca2+ content of natural water containing salts is very low, owing to precipitation. In these samples silicate-Na+ was identified as the dissolution species of silica; it was also ascertained that Ca2+ did not form complexes with silicate species. These observations resulted from direct identification of dissolved chemical species by use of FAB-MS (fast atom bombardment mass spectrometry). The research indicates that in water samples in this critically arid region the concentration of dissolved silica is basically determined by the concentration of Na+, indicative of pure inorganic conditions in the desert area of Xinjiang, N.W. China. 相似文献