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排序方式: 共有225条查询结果,搜索用时 31 毫秒
61.
62.
M. Sc. Niklas Felix König Dr. Abdelaziz Al Ouahabi Dr. Salomé Poyer Prof. Laurence Charles Dr. Jean-François Lutz 《Angewandte Chemie (International ed. in English)》2017,56(25):7297-7301
A three-step post-polymerization modification method was developed for the design of digitally encoded poly(phosphodiester)s with controllable side groups. Sequence-defined precursors were synthesized, either manually on polystyrene resins or automatically on controlled pore glass supports, using two phosphoramidite monomers containing either terminal alkynes or triisopropylsilyl (TIPS) protected alkyne side groups. Afterwards, these polymers were modified by stepwise copper-catalyzed azide–alkyne cycloaddition (CuAAC). The terminal alkynes were first reacted with a model azide compound, and after removal of the TIPS groups, the remaining alkynes were reacted with another organic azide. This simple method allows for quantitative side-chain modification, thus opening up interesting avenues for the preparation of a wide variety of digital polymers. 相似文献
63.
64.
We consider one-dimensional problem for the thermoelastic diffusion theory and we obtain polynomial decay estimates. Then we show that the solution decays exponentially to zero as time goes to infinity; that is, denoting by E(t) the first-order energy of the system, we show that positive constants C 0 and c 0 exist which satisfy E(t) ≤ C 0 E(0)e ?c 0 t . 相似文献
65.
In this article, we prove that the following weighted Hardy inequality $$\begin{array}{ll}\big(\frac{|{d-p}|}{p}\big)^{p}\, \int\limits_{\Omega}\, \frac{|{u}|^{p}}{|{x}|^{p}}\;d\mu \\ \quad \quad \le \int\limits_{\Omega}\,|{\nabla u}|^{p}\;d\mu+ \big(\frac{|{d-p}|}{p}\big)^{p-1}\,\textrm{sgn}(d-p)\,\int\limits_{\Omega}|{u}|^{p}\,\frac{(x^{t}Ax)^{p/2}}{|{x}|^{p}}\; d\mu \quad \quad \quad (1) \end{array}$$ holds with optimal Hardy constant ${\big(\frac{|d-p|}{p}\big)^{p}}$ for all ${u \in W^{1,p}_{\mu,0}(\Omega)}$ if the dimension d ≥ 2, 1 < p < d, and for all ${u \in W^{1,p}_{\mu,0}(\Omega{\setminus}\{0\})}$ if p > d ≥ 1. Here we assume that Ω is an open subset of ${\mathbb{R}^{d}}$ with ${0 \in \Omega}$ , A is a real d × d-symmetric positive definite matrix, c > 0, and $$ d \mu: = \rho(x) \,dx \qquad \textrm{with} \quad \rho(x) = c \cdot \exp(-\frac{1}{p}(x^{t}Ax)^{p/2}), \quad x \in\Omega.\quad \quad (2) $$ If p > d ≥ 1, then we can deduce from (1) a weighted Poincaré inequality on ${W^{1,p}_{\mu,0}(\Omega \setminus\{0\})}$ . Due to the optimality of the Hardy constant in (1), we can establish the nonexistence (locally in time) of positive weak solutions of a p-Kolmogorov parabolic equation perturbed by a singular potential in dimension d = 1, for 1 < p < + ∞, and when Ω = ]0, + ∞[. 相似文献
66.
In this paper, we study hospital bed capacity management for a set of existing hospitals when the demand for beds is random. We propose a multiobjective stochastic program model to assign beds to hospital departments. We consider three objective functions to be minimized, which are the cost of creation and management of new beds and the number of nurses and physicians working in these hospitals, subject to demand satisfaction of three kinds of health-care specialities. A certainty equivalent program was derived based on a mixture between the chance constrained approach, the recourse approach and the goal programming approach. Empirical results using real data from 157 Tunisian national hospitals are reported. 相似文献
67.
Hayet Benzarouk Abdelaziz Drici Mounira Mekhnache Abdelaziz Amara Mouhamed Guerioune Jean Christian Bernède Hacen Bendjffal 《Superlattices and Microstructures》2012
In the present work we studied the influence of the dopant elements and concentration on the microstructural and electrochemical properties of ZnO thin films deposited by spray pyrolysis. Transparent conductive thin films of zinc oxide (ZnO) were prepared by the spray pyrolysis process using an aqueous solution of zinc acetate dehydrate [Zn(CH3COO)2·2H2O] on soda glass substrate heated at 400 ± 5 °C. AlCl3, MgCl2 and NiCl2 were used as dopant. The effect of doping percentage (2–4%) has been investigated. Afterwards the samples were thermally annealed in an ambient air during one hour at 500 °C. X-ray diffraction showed that films have a wurtzite structure with a preferential orientation along the (0 0 2) direction for doped ZnO. The lattice parameters a and c are estimated to be 3.24 and 5.20 ?, respectively. Transmission allowed to estimate the band gaps of ZnO layers. The electrochemical studies revealed that the corrosion resistance of the films depended on the concentration of dopants. 相似文献
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69.
Wessameldin S. Abdelaziz 《Journal of Russian Laser Research》2012,33(1):14-19
We use the energy levels, transition probabilities, and effective collision strengths for the states 1s2 2s2 2p6 3s2 3p6 3d10 and 1s2 2s2 2p6 3s2 3p6 3d9 4 l (l = s, p, d, and f) of a nickel-like Nd ion to determine reduced population for 55 fine-structure levels over a wide
range of electron density values (from 1020 to 4 · 1022 cm
−3) at various electron plasma temperatures in the range of 1–2 keV. We find the gain coefficients for those transitions with
the positive population inversion factor and show their dependences on the electron density. 相似文献
70.
Helena Sidorenkova Théo Berclaz Bassirou Ndiaye Abdelaziz Jouaiti Michel Geoffroy 《Journal of Physics and Chemistry of Solids》2009,70(3-4):713-718
A radical species characterized by a large g-anisotropy and a clearly resolved hyperfine structure with 95/97Mo and 31P nuclei is formed, at 77 K, by radiolysis of a single crystal of Mo(CO)5PPh3. The corresponding EPR signals disappear irreversibly with increasing temperature and the angular dependence of the various coupling constants imply a spin delocalization of ~60% and ~4% on the molybdenum and the phosphorus atoms, respectively and are, a priori, consistent with the trapping of a one-electron deficient centre. The ability of DFT to predict the EPR tensors for a 17-electron Mo(I) species is verified by calculating the g-tensor and the various 14N and 13C coupling tensors previously reported by Hayes for [Mo(CN)5NO]3?. Calculations at the B3LYP/ZORA/SOMF level of theory show that, in contrast to Mo(CO)5PH3, one-electron oxidation of Mo(CO)5PPh3 causes an appreciable change in the geometry of the complex. The g-tensor and the 95/97Mo and 31P isotropic and anisotropic coupling constants calculated for [Mo(CO)5PPh3]+· confirm the trapping of this species in the irradiated crystal of Mo(CO)5PPh3; they also show that the conformational modifications induced by the electron release are probably hindered by the nearby complexes. 相似文献