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排序方式: 共有247条查询结果,搜索用时 15 毫秒
111.
112.
113.
Ahmed Oueslati Hatem Ben Romdhane Régis Mercier Refaât M. Chaâbouni 《Comptes Rendus Chimie》2010,13(11):1406-1415
Four pentamethylated norbardiene (NBD) models containing imide, bis-imide and diamides were synthesized in the first step of this work with a good yield and characterized by IR, 1HNMR and 13CNMR spectroscopies. These models were used for study, by UV-Visible spectrophotometry, of the photochemical isomerisation under solar radiations of NBD residues, which they contain to quadricyclane (QC). Acquired results show, for all these models, that more than 70 % of NBD are transformed into QC after only 30 minutes of solar radiations and following a first order rate. 相似文献
114.
Hatem Najar Samir Ben Hariz Mounir Ben Salah 《Mathematical Physics, Analysis and Geometry》2010,13(1):19-28
In this study we investigate the bound states of the Hamiltonian describing a quantum particle living on three dimensional
straight strip of width d. We impose the Neumann boundary condition on a disc window of radius a and Dirichlet boundary conditions on the remained part of the boundary of the strip. We prove that such system exhibits discrete
eigenvalues below the essential spectrum for any a > 0. We give also a numeric estimation of the number of discrete eigenvalue as a function of
\fracad\frac{a}{d}. When a tends to the infinity, the asymptotic of the eigenvalue is given. 相似文献
115.
Kaiçar Ammous Bruno Allard Hatem Garrab Anis Ammous 《Journal of Thermal Analysis and Calorimetry》2007,90(1):307-314
In this paper, a measurement technique of losses in the switching cell, based on calorimetric technique is presented. A special
calorimeter was designed to be able to access the heat generated by an operating converter. Power component losses are studied
according to the cyclic ratio and to operating frequency and an extraction method of the different terms of these losses,
using calorimetric measurements, is presented.
An accurate expression of the switching losses in the power semiconductors devices is proposed. 相似文献
116.
Hatem Elloumi Georges Zissis Jean Jacques Damelincourt 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,86(4):361-369
A numerical model has been developed for studying the time-dependent behavior of cylindrical high power xenon flashlamp. The equations of local energy conservation and mass conservation are solved using the finite volume method to give plasma parameters such as radial temperature profiles, instantaneous emission spectra, pressure, velocity, arc conductance, etc. In a first approximation the plasma is described under local thermodynamic equilibrium, LTE. The results are given as a function of time over the pulse and for several nodes in the cross section. Then the detailed spectral and temporal calculations of the output radiation from xenon flashlamp and radiation efficiencies are provided. 相似文献
117.
In this paper, we consider the semilinear wave equation with a power nonlinearity in one space dimension. We exhibit a universal one-parameter family of functions which stand for the blow-up profile in self-similar variables at a non-characteristic point, for general initial data. The proof is done in self-similar variables. We first characterize all the solutions of the associated stationary problem, as a one parameter family. Then, we use energy arguments coupled with dispersive estimates to show that the solution approaches this family in the energy norm, in the non-characteristic case, and to a finite decoupled sum of such a solution in the characteristic case. Finally, in the case where this sum is reduced to one element, which is the case for non-characteristic points, we use modulation theory coupled with a nonlinear argument to show the exponential convergence (in the self-similar time variable) of the various parameters and conclude the proof. This step provides us with a result of independent interest: the trapping of the solution in self-similar variables near the set of stationary solutions, valid also for non-characteristic points. The proof of these results is based on a new analysis in the self-similar variable. 相似文献
118.
Javed Sheikh Harjeet Juneja Vishwas Ingle Parvez Ali Taibi Ben Hadda 《Journal of Saudi Chemical Society》2013,17(3):269-276
The clinically active functionalized β-diketones 1-(2′,4′-dihydroxyphenyl)-3-(2″-substitutedphenyl)-propane-1,3-dione (L1)–(L2) have been synthesized from Baker–Venkataraman transformation of 2,4-diaroyloxyacetophenones. Their transition metal complexes (1)–(8) have been prepared and characterized by physical, spectral and analytical data. The functionalized beta-diketone potentially acts as bidentate ligand and co-ordinate with the transition metal atom through beta-diketo system. The complexes have general formula [ML2] where M = Co(II), Ni(II), Cu(II), Zinc(II) and L = ligand. The 1-(2′,4′-dihydroxyphenyl)-3-(2″-substitutedphenyl)-propane-1,3-dione and their transition metal complexes have been screened for in vitro antibacterial, antifungal and antioxidant bioassay. The biological activity data show that the transition metal complexes are more potent antibacterial, antifungal and antioxidant agents than the parent functionalized beta-diketone against different bacterial and fungal species. This constitutes a new group of compounds that can be used as potential metal derived drugs. Ultimately, here we can prompt about the use of metals for the drugs. The metal complexes were also studied for their thermogravimetric analyses. 相似文献
119.
Ismail Warad Omar H Abd-Elkader Ahmed Boshaala Nabil Al-Zaqri Belkheir Hammouti Taibi Ben Hadda 《Research on Chemical Intermediates》2013,39(2):721-732
The preparation of new [MeC(CH2PPh2)3CuCl] 1 and its derivatives was carried out directly by mixing of CuCl and MeC(CH2PPh2)3 ligand in dry THF, the neutral precursor 1 served to prepare [MeC(CH2PPh2)3Cu(NCCH3)]BF4 2 and [MeC(CH2PPh2)3Cu(PCH2Ph)3]BF4 3. These complexes are characterized on the basis of elemental analysis, IR, EDS, 1H, 13C and 31P{1H}NMR, FAB-MS, TG/DTA and single-crystal X-ray diffraction studies. Complex 1 crystallizes in the Orthorhombic unit cells with the space group Pna2(1). The structural behavior of MeC(CH2PPh2)3 ligand in the formed complexes during the coordination reaction was monitored by 31P{1H}NMR in CDCl3 at room temperature for the first time. 相似文献
120.
Hatem Najar 《Journal of statistical physics》2007,128(4):1093-1112
In this study, we consider acoustic operators in a random quantum waveguide. Precisely we deal with an elliptic operator in
the divergence form on a random strip. We prove that the integrated density of states of the relevant operator exhibits Lifshitz
behavior at the bottom of the spectrum. This result could be used to prove localization of acoustic waves at the bottom of
the spectrum.
2000 Mathematics Subject Classification: 81Q10, 35P05, 37A30, 47F05 相似文献