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961.
In this paper, we propose a stenography scheme based on predictive differencing to embed data in a grey-image. In order to
promote the embedding capacity of pixel-value differencing (PVD), we use differencing between a predictive value and an input
pixel as the predictive differencing to embed the message where a predictive value is calculated by using various predictors.
If the predictive differencing is large, then it means that the input pixel is located in the edge area and, thus, has a larger
embedding capacity than the pixel in a smooth area. The experimental result shows that our proposed scheme is capable of providing
greater embedding capacity and high quality of stego-images then previous works. Furthermore, we have also applied various
predictors to evaluate our proposed scheme. 相似文献
962.
M. Brazil J. H. Rubinstein D. A. Thomas J. F. Weng N. Wormald 《Journal of Optimization Theory and Applications》2012,155(1):336-354
The gradient-constrained Steiner tree problem asks for a shortest total length network interconnecting a given set of points in 3-space, where the length of each edge of the network is determined by embedding it as a curve with absolute gradient no more than a given positive value m, and the network may contain additional nodes known as Steiner points. We study the problem for a fixed topology, and show that, apart from a few easily classified exceptions, if the positions of the Steiner points are such that the tree is not minimum for the given topology, then there exists a length reducing perturbation that moves exactly 1 or 2 Steiner points. In the conclusion, we discuss the application of this work to a heuristic algorithm for solving the global problem (across all topologies). 相似文献
963.
The assembly of soluble, air-stable, supramolecular structures {(Zn-TPyP)[Cp*Ir{S2C2(B10H10)}]4(THF)2}(2), {(Cu-TPyP)[Cp*Ir{S2C2(B10H10)}]4(THF)2}(3) and {(Zn-TPyP)[Cp*Ir{S2C2(B10H10)}]2.6(CHCl3)}n (4), based on metal-containing moieties [Cp*Ir{S2C2(B10H10)}] (1) bridged by nitrogen-based organic spacers, are described. 相似文献
964.
The lower critical solution temperature (LCST) behaviors of random and segmented copolymers of N-isopropylacrylamide (NIPAM) and acrylic acid (AA) prepared in dioxane and water have been investigated by using ultrasensitive microcalorimetry (US-DSC). The introduction of AA increases the LCST of the former but slightly affects that of the latter. When the molar fraction of AA is low (approximately 2 mol %), the LCST of the segmented copolymer shifts to a higher temperature with increasing pH, while the LCST of the corresponding random copolymer slightly changes. Below the boiling point of water, the random copolymer and segmented copolymer with the molar fraction of AA about 15 mol % no longer exhibit an LCST at pH > 5. The addition of calcium ions leads the LCST of both the segmented copolymer and random copolymer to decrease. Our results suggest that the LCST behavior of the copolymers is determined by the clustering of poly(N-isopropylacrylamide) segments. 相似文献
965.
A microfluidic device with an all-solid-state potentiometric biosensor array was developed using microfabrication technology. The sensor array included a pH indicator, and potassium and calcium ion-selective microelectrodes. The pH indicator was an iridium oxide thin film modified platinum microelectrode and the iridium oxide was deposited by an electrochemical method. The potassium and calcium ion-selective microelectrodes were platinum coated with silicon rubber based ion-selective membranes with respectively potassium (valinomycin) and calcium (ETH 1001) ionophores. The detection system was integrated with a micro-pneumatic pump which can continuously drive fluids into the microchannel through sensors at flow rates ranging from 52.4 microl min(-1) to 7.67 microl min(-1). The sensor array microfluidic device showed near-Nernstian responses with slopes of 62.62 mV +/- 2.5 mV pH(-1), 53.76 mV +/- 3 mV -log[K+](-1) and 25.77 mV +/- 2 mV -log[Ca2+](-1) at 25 degrees C +/- 5 degrees C, and a linear response within the pH range of 2-10, with potassium and calcium concentrations between 0.1 M and 10(-6) M. In this study the device provided a convenient way to measure the concentration of hydrogen, potassium and calcium ions, which are important physiological parameters. 相似文献
966.
Herein, we present a new method for preparing homoligand 3D coordination polymers. First, a layered metal-organic framework Zn3(BDC)3(H2O)2 x 4DMF 1 (BDC is terephthalate, DMF is N,N-dimethylformamide) was fabricated from a H2BDC by liquid-liquid diffusion. Second, the layered product, 1, was used as a precursor to solvothermally react with further H2BDC at 140-180 degrees C, resulting in two products of BDC insertion into the layered structure. These are [Zn3(p-BDC)4] x 2HPIP, 2 (HPIP is partly protonated piperazine), and [Zn3(p-BDC)3(H2BDC)] x (C6H15NO) x H2O x 3DMF, 3 (C6H15NO is triethylamine N-oxide). Single-crystal X-ray diffraction shows that 2 possesses a layer-pillared structure of mu4-BDC, with 1D channels, while 3 has a layer-pillared structure of mu2-BDC, with 2D channels. N2-sorption experiments show 3 has a relatively high BET surface area of 750 m(2)/g. It is proposed that 2 follows the crystal growth mechanism of Ostwald ripening, whereas the crystal structure of 3 might be formed by an insertion mechanism. 相似文献
967.
The synthesis and structural characterisation of two novel clusters, 2, and 3, are presented. They are the first examples of osmium and ruthenium clusters containing a naked
atom. 相似文献
968.
We demonstrate a compact Q-switched dual-wavelength erbium-doped fiber (EDF) laser based on graphene as a saturable absorber (SA). By optically driven deposition of graphene on a fiber core, the SA is constructed and inserted into a diode-pumped EDF laser cavity. Also benefiting from the strong third-order optical nonlinearity of graphene to suppress the mode competition of EDF, a stable dual-wavelength Q-switching operation has been achieved using a two-reflection peak fiber Bragg grating as the external cavity mirror. The Q-switched EDF laser has a low pump threshold of 6.5 mW at 974 nm and a wide range of pulse-repetition rate from 3.3 to 65.9 kHz. The pulse duration and the pulse energy have been characterized. This is, to the best of our knowledge, the first demonstration of a graphene-based Q-switched laser. 相似文献
969.
This investigation demonstrates leakage coupling between fundamental-mode and high-order mode resonance based on a periodical silica thin-film long-period grating (TFLPG) that was coated on a tapered fiber when wavelengths longer than the fundamental-mode cutoff were propagated. For the leaky guiding situation, these leakage modes still may exhibit strong mode coupling in the taper with the assistance of the TFLPG when the phase-matched condition is satisfied. An extremely high tuning efficiency of 62.9 nm/°C, which is equivalent to a measurement of sensitivity of approximately 168, 182 nm per refractive index unit, is achieved. To the best of our knowledge, this sensitivity is the highest achieved for a fiber sensor to date. 相似文献
970.