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991.
Alfredo Tlahuice-Flores Sergio Mejía-Rosales Donald H. Galván 《Journal of nanoparticle research》2012,14(8):1-10
While nephrotoxicity of cadmium is well documented, very limited information exists on renal effects of exposure to cadmium-containing nanomaterials. In this work, ??omics?? methodologies have been used to assess the action of cadmium-containing silica nanoparticles (Cd-SiNPs) in the kidney of Sprague-Dawley rats exposed intratracheally. Groups of animals received a single dose of Cd-SiNPs (1?mg/rat), CdCl2 (400???g/rat) or 0.1?ml saline (control). Renal gene expression was evaluated 7 and 30?days post exposure by DNA microarray technology using the Agilent Whole Rat Genome Microarray 4x44K. Gene modulating effects were observed in kidney at both time periods after treatment with Cd-SiNPs. The number of differentially expressed genes being 139 and 153 at the post exposure days 7 and 30, respectively. Renal gene expression changes were also observed in the kidney of CdCl2-treated rats with a total of 253 and 70 probes modulated at 7 and 30?days, respectively. Analysis of renal gene expression profiles at day 7 indicated in both Cd-SiNP and CdCl2 groups downregulation of several cluster genes linked to immune function, oxidative stress, and inflammation processes. Differing from day 7, the majority of cluster gene categories modified by nanoparticles in kidney 30?days after dosing were genes implicated in cell regulation and apoptosis. Modest renal gene expression changes were observed at day 30 in rats treated with CdCl2. These results indicate that kidney may be a susceptible target for subtle long-lasting molecular alterations produced by cadmium nanoparticles locally instilled in the lung. 相似文献
992.
The relationships between cannibalism and pattern formation in spatially extended prey–predator systems are studied with a
model that degenerates, in the absence of cannibalism, into the most standard prey–predator model, known as Rosenzweig–MacArthur
model. The analysis is based on the theory developed long ago by Turing in his famous paper on morphogenesis, but in a special
form, which allows one to decouple the role of demographic parameters from that of diffusive dispersal. The proofs are given
in terms of prey and predator nullclines because ecologists are mainly familiar with this technique. The final result of the
analysis is that spatial pattern can exist only in systems with highly cannibalistic and highly dispersing predator provided
the attractor of the system in the absence of cannibalism is a limit cycle. This result is more simple and more complete than
that published in this journal a few years ago by Sun and coauthors. 相似文献
993.
We prove the global existence of solutions for a shape-memory alloys constitutive model at finite strains. The model has been
presented in Evangelista et al. (Int J Numer Methods Eng 81(6):761–785, 2010) and corresponds to a suitable finite-strain version of the celebrated Souza–Auricchio model for SMAs (Auricchio and Petrini
in Int J Numer Methods Eng 55:1255–1284, 2002; Souza et al. in J Mech A Solids 17:789–806, 1998). We reformulate the model in purely variational fashion under the form of a rate-independent process. Existence of suitably
weak (energetic) solutions to the model is obtained by passing to the limit within a constructive time-discretization procedure. 相似文献
994.
Francisco López Jiménez Sergio Pellegrino 《International Journal of Solids and Structures》2012,49(3-4):635-647
This paper presents an experimental and numerical study of unidirectional carbon fiber composites with a silicone matrix, loaded transversally to the fibers. The experiments show nonlinear behavior with significant strain softening under cyclic loading. The numerical study uses a plane-strain finite element continuum model of the composite material in which the fiber distribution is based on experimental observations and cohesive elements allow debonding to take place at the fiber/matrix interfaces. It is found that accurate estimates of the initial tangent stiffness measured in the experiments can be obtained without allowing for debonding, but this feature has to be included to capture the non-linear and strain-softening behavior. 相似文献
995.
Ana Tost Carolina Migliorelli Alejandro Bachiller Ins Medina-Rivera Sergio Romero ngeles García-Cazorla Miguel A. Maanas 《Entropy (Basel, Switzerland)》2021,23(8)
Rett syndrome is a disease that involves acute cognitive impairment and, consequently, a complex and varied symptomatology. This study evaluates the EEG signals of twenty-nine patients and classify them according to the level of movement artifact. The main goal is to achieve an artifact rejection strategy that performs well in all signals, regardless of the artifact level. Two different methods have been studied: one based on the data distribution and the other based on the energy function, with entropy as its main component. The method based on the data distribution shows poor performance with signals containing high amplitude outliers. On the contrary, the method based on the energy function is more robust to outliers. As it does not depend on the data distribution, it is not affected by artifactual events. A double rejection strategy has been chosen, first on a motion signal (accelerometer or EEG low-pass filtered between 1 and 10 Hz) and then on the EEG signal. The results showed a higher performance when working combining both artifact rejection methods. The energy-based method, to isolate motion artifacts, and the data-distribution-based method, to eliminate the remaining lower amplitude artifacts were used. In conclusion, a new method that proves to be robust for all types of signals is designed. 相似文献
996.
Brane inflationary universe model in the context of intermediate inflation is studied. General conditions for this model to be realizable are discussed. In the high-energy limit we describe in great details the characteristic of this model. 相似文献
997.
We invoke the Tsallis entropy formalism, a nonextensive entropy measure, to include some degree of non-locality in a neural network that is used for simulation of novel word learning in adults. A generalization of the gradient descent dynamics, realized via nonextensive cost functions, is used as a learning rule in a simple perceptron. The model is first investigated for general properties, and then tested against the empirical data, gathered from simple memorization experiments involving two populations of linguistically different subjects. Numerical solutions of the model equations corresponded to the measured performance states of human learners. In particular, we found that the memorization tasks were executed with rather small but population-specific amounts of nonextensivity, quantified by the entropic index q. Our findings raise the possibility of using entropic nonextensivity as a means of characterizing the degree of complexity of learning in both natural and artificial systems. 相似文献
998.
By using our novel Grassmann formulation we study the phase transition of the spanning-hyperforest model of the k-uniform complete hypergraph for any k2. The case k=2 reduces to the spanning-forest model on the complete graph. Different k are studied at once by using a microcanonical ensemble in which the number of hypertrees is fixed. The low-temperature phase is characterized by the appearance of a giant hyperforest. The phase transition occurs when the number of hyperforests is a fraction (k−1)/k of the total number of vertices. The behaviour at criticality is also studied by means of the coalescence of two saddle points. As the Grassmann formulation exhibits a global supersymmetry we show that the phase transition is second order and is associated to supersymmetry breaking and we explore the pure thermodynamical phase at low temperature by introducing an explicit breaking field. 相似文献
999.
Ferenc Somodi Mihály Heged?s István E. Sajó Sergio Rojas József L. Margitfalvi 《Applied Surface Science》2009,256(3):726-736
In this study the influence of SnOx nanoparticles on the catalytic performance of alumina-supported gold catalysts was investigated in CO oxidation. The tin modified supports were prepared by grafting of tetraethyltin onto the surface of alumina via its hydroxyl groups. The decomposition of organometallic surface species in oxygen yielded highly dispersed tin oxide on the surface of alumina. Gold was introduced onto the tin modified alumina support by both deposition-precipitation with urea and direct anionic exchange techniques using HAuCl4 solution. Based on catalytic and different spectroscopic measurements it is suggested that the presence of “Snn+-Au ensemble sites” is responsible for the increased activity of these catalysts. 相似文献
1000.
M. Enriqueta Díaz de Vivar Sergio Baggio Juan Carlos Muoz Ricardo Baggio 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(1):m30-m33
Two different zinc sulfite compounds have been prepared through the decomposition of pyrosulfite–dithionite ions in aqueous solution, viz. a dimeric complex, di‐μ‐sulfito‐κ3O,O′:O′′;κ3O:O′,O′′‐bis[(4,4′‐dimethyl‐2,2′‐bipyridine‐κ2N,N′)zinc(II)] dihydrate, [Zn2(SO3)2(C12H12N2)2]·2H2O, (I), which was solved and refined from a twinned sample, and an extended polymer, poly[[aqua(1,10‐phenanthroline‐κ2N,N′)zinc(II)]‐μ3‐sulfito‐κ2O:O′:O′′‐zinc(II)‐μ3‐sulfito‐κ3O:O:O′], [Zn2(SO3)2(C12H10N2)(H2O)]n, (II). In (I), the dinuclear ZnII complex has a center of symmetry. The cation is five‐coordinate in a square‐pyramidal arrangement, the anion fulfilling a bridging chelating role. Compound (II) comprises two different zinc units, one being five‐coordinate (square pyramidal) and the other four‐coordinate (trigonal pyramidal), and two independent sulfite groups with different binding modes to the cationic centers. 相似文献