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51.
Aslı Deniz 《Journal of Difference Equations and Applications》2013,19(12):1627-1640
In this article, we present a landing theorem for periodic dynamic rays for transcendental entire maps which have bounded post-singular sets, by using standard hyperbolic geometry results. 相似文献
52.
A new transparent bulk glass from the system 76TeO2?·?10ZnO?·?9.0PbO?·?1.0PbF2?·?3.0Na2O doped with Er3+ (TZPPN doped with Er3+) has been prepared using the conventional melt-quenching method. Results of differential thermal analysis (DTA) measurements indicate good thermal stability of this glass. The refractive indices at different wavelengths, the optical energy gap, the Sellmeier gap energy and the dispersion energy have been estimated. The Judd–Ofelt parameters, Ω t (t?=?2,?4,?6) of Er3+ were evaluated from optical absorption spectra. Electric dipole, magnetic dipole type transition probabilities, spectroscopic quality factors, branching ratio and radiative lifetimes of several excited states of Er3+ have been predicted using intensity Judd–Ofelt parameters. The spectroscopic properties indicate that TZPPN glass doped with Er3+ is a promising candidate for laser applications and may be suitable for upconversion fibre optical devices. 相似文献
53.
Polyetherimide (PEI) is an extraordinary type of polyimide with excellent thermal and mechanical properties. The polymer is also gas permeable and is considered one of the best membranes for gas separation. Despite the high selectivity, PEI suffers from low permeability due to the trade‐off between phenomena in polymers. To overcome this limitation, fillers are added during the membrane preparation to create voids for better gas transport. In this paper, permeability and selectivity data of PEI membranes for the separation of oxygen, carbon dioxide, and helium are discussed. The paper also summarizes the reported studies for adding fillers to improve the membrane performance. 相似文献
54.
Fazaeli Yousef Hosseini Mohammad Amin Shahabinia Fatemeh Feizi Shahzad 《Journal of Radioanalytical and Nuclear Chemistry》2019,320(1):201-207
Journal of Radioanalytical and Nuclear Chemistry - Porphyrins and 68Ga have emerged as novel synergic options for PET applications so the idea of preparation of a novel porphyrin complex using this... 相似文献
55.
Polycrystalline ferrites with general formula Co0.5CdxFe2.5−xO4 (0.0?x?0.5) were prepared by sol-gel method. The dielectric properties ε′, ε″, loss tangent tan δ and ac conductivity σac have been studied as a function of frequency, temperature and composition. The experimental results indicate that ε′, ε″, tan δ and σac decrease as the frequency increases; whereas they increase as the temperature increases. These parameters are found to increase by increasing the concentration of Cd content up to x=0.2, after which they start to decrease with further increase in concentration of Cd ion. The dielectric properties and ac conductivity in studied samples have been explained on the basis of space charge polarization according to Maxwell and Wagner's two-layer model and the hoping between adjacent Fe2+ and Fe3+ as well as the hole hopping between Co3+and Co2+ ions at B-sites. The values of activation energies Ef for conduction process are determined from Arrhenius plots, and the variations in these activation energies as a function of Cd content are discussed. The complex impedance analysis is used to separate the grain and grain boundary of the system Co0.5CdxFe2.5−xO4. The variations of both grain boundary and grain resistances with temperature and composition are evaluated in the frequency range 42 Hz-5 MHz. 相似文献
56.
Glasses in the system TeO2/Nb2O5/ZnO/CdS were studied with respect to the density, molar volume, refractive index, polarizability, molar refraction, metallization and third order non-linear optical susceptibility. The third order non-linear optical susceptibilities, χ(3), were measured using degenerate four-wave mixing (DFWM). The addition of CdS to TeO2-based glasses leads to increasing refractive as well as the non-linear refractive indices. The largest measured value of the third order non-linear optical susceptibility was 7.8 × 10?13 esu and has been found in the 90TeO2 · 5Nb2O5 · 5ZnO · 0.4 CdS glass. The non-linear optical susceptibility increased with increasing CdS-concentration. In order to estimate the third order non-linear optical susceptibility, the theoretical model of Lines and the empirical equation of Miller were used. 相似文献
57.
Bassam Abbas Yousef T. Salman Moustafa S. El-Daher 《Journal of Macromolecular Science: Physics》2015,54(12):1457-1465
Photoinduced birefringence in poly(methyl methacrylate) (PMMA), polymeric thin films doped with di-azo Sudan G was investigated. A pump-probe method was used to study the dynamic behavior of the birefringence. The mechanism for the inducement of birefringence is discussed in terms of the photoisomerization of the di-azo Sudan G molecules. The results showed that the dynamic evolution of the photoinduced birefringence was such that the average birefringence increased, saturated, and then decreased with respect to the laser pump intensity. Also, an exponential-like relationship was observed between both the saturation and the isotropic states of the averaged transmitted probe beam (expressing the residual anisotropy) and the birefringence on one hand, and the intensity amplitudes of the pumping powers on the other hand. 相似文献
58.
59.
Zhuang Liu Yousef Faraj Xiao-Jie Ju Wei Wang Rui Xie Liang-Yin Chu 《Journal of polymer science. Part A, Polymer chemistry》2018,56(19):1306-1313
Responsive hydrogels have the ability to change their volume, transparency, or other properties in response to external chemical and/or physical stimuli. The responsiveness properties including responsive rate and degree, as well as mechanical properties such as Young's modulus, toughness, breaking strength, and breaking strain are crucial parameters of the smart hydrogels that determine the scope of hydrogel applications such as soft actuators, artificial muscles, and tissue engineering scaffolds. In this paper, the development of the nanocomposite smart hydrogels, which can achieve both improved responsiveness and mechanical properties, is reviewed. First, the fabrication approaches for building the nanocomposite networks by doping organic or inorganic nanomaterials via crosslinking or blending strategies are introduced. Then, the mechanisms used to improve both responsiveness and mechanical properties of nanocomposite responsive hydrogels are discussed. Finally, the perspectives as well as current challenges of such nanocomposite responsive hydrogels are addressed. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 1306–1313 相似文献
60.
We introduce a new implementation of time-dependent density-functional theory which allows the entire spectrum of a molecule or extended system to be computed with a numerical effort comparable to that of a single standard ground-state calculation. This method is particularly well suited for large systems and/or large basis sets, such as plane waves or real-space grids. By using a superoperator formulation of linearized time-dependent density-functional theory, we first represent the dynamical polarizability of an interacting-electron system as an off-diagonal matrix element of the resolvent of the Liouvillian superoperator. One-electron operators and density matrices are treated using a representation borrowed from time-independent density-functional perturbation theory, which permits us to avoid the calculation of unoccupied Kohn-Sham orbitals. The resolvent of the Liouvillian is evaluated through a newly developed algorithm based on the nonsymmetric Lanczos method. Each step of the Lanczos recursion essentially requires twice as many operations as a single step of the iterative diagonalization of the unperturbed Kohn-Sham Hamiltonian. Suitable extrapolation of the Lanczos coefficients allows for a dramatic reduction of the number of Lanczos steps necessary to obtain well converged spectra, bringing such number down to hundreds (or a few thousands, at worst) in typical plane-wave pseudopotential applications. The resulting numerical workload is only a few times larger than that needed by a ground-state Kohn-Sham calculation for a same system. Our method is demonstrated with the calculation of the spectra of benzene, C(60) fullerene, and of chlorophyll a. 相似文献