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61.
Noemi Szekély 《European Polymer Journal》2009,45(5):1385-1390
A hydrophilic non-stoichiometric epoxy network was prepared by end-linking reaction of α,ω-diamino terminated poly(oxypropylene)-b-poly(oxyethylene)-b-poly(oxypropylene) (POP-POE-POP) and diglycidyl ether of Bisphenol A propoxylate (PDGEBA) at the excess of amino groups. Series of epoxy hydrogels swollen to various degrees was prepared by swelling of the epoxy network in D2O and solutions of inorganic salt (KNO3) in D2O, respectively, and investigated by small-angle neutron scattering (SANS). Degree of swelling was controlled in two ways: by partial evaporation of the solvent and by KNO3 concentration in the swelling solution. Nanophase separated structure of all hydrogels was confirmed by SANS. Scattering data were fitted to the Teubner-Strey model assuming bicontinuous locally lamellar structure of the hydrogels. Changes in SANS profiles induced by the presence of KNO3 in swelling solutions reflect a refinement of the nanophase separated structure of hydrogels caused by improvement of POE-D2O interaction by means of breakage of deuterium-bonded structure of D2O by nitrate anions. 相似文献
62.
Félix Cabello Sánchez 《Proceedings Mathematical Sciences》2000,110(2):205-211
We study linear bijections of simplex spacesA(S) which preserve the diameter of the range, that is, the seminorm ϱ(f)=sup{|f(x)−f(y)|:x,yεS}. 相似文献
63.
64.
65.
Prof. Carlos O. Areán Dr. Sachin Chavan Carlos P. Cabello Prof. Edoardo Garrone Dr. Gemma T. Palomino 《Chemphyschem》2010,11(15):3237-3242
Interaction between adsorbed hydrogen and the coordinatively unsaturated Mg2+ and Co2+ cationic centres in Mg‐MOF‐74 and Co‐MOF‐74, respectively, was studied by means of variable‐temperature infrared (VTIR) spectroscopy. Perturbation of the H2 molecule by the cationic adsorbing centre renders the H? H stretching mode IR‐active at 4088 and 4043 cm?1 for Mg‐MOF‐74 and Co‐MOF‐74, respectively. Simultaneous measurement of integrated IR absorbance and hydrogen equilibrium pressure for spectra taken over the temperature range of 79–95 K allowed standard adsorption enthalpy and entropy to be determined. Mg‐MOF‐74 showed ΔH0=?9.4 kJ mol?1 and ΔS0=?120 J mol?1 K?1, whereas for Co‐MOF‐74 the corresponding values of ΔH0=?11.2 kJ mol?1 and ΔS0=?130 J mol?1 K?1 were obtained. The observed positive correlation between standard adsorption enthalpy and entropy is discussed in the broader context of corresponding data for hydrogen adsorption on cation‐exchanged zeolites, with a focus on the resulting implications for hydrogen storage and delivering. 相似文献
66.
Fernández-Ruiz R Galisteo FC Larese C Granados ML Mariscal R Fierro JL 《The Analyst》2006,131(4):590-594
A methodology for the quantitative analysis of the elements present in car exhaust catalysts by TXRF is described. Some of the most relevant catalytic components (Zr, Rh, Pd) and contaminant elements (P, Pb, Zn, Pt, Ca and Ni) on car Three Way Catalysts were quantified during vehicle aging. The study was conducted along the main axis of a Ford Focus 1.6i catalytic cartridge, aiming to obtain the axial profile of the elements retained or eliminated after more than 59,000 km. The analysis of a fresh Three Way Catalysts (0 km) was also conducted for comparative purposes. The existence of a strong differences for elemental concentration in the interphase between the two blocks of the catalytic cartridge has been quantitatively measured for first time. In addition, the behaviour of the contaminant absorption capacity of both catalytic blocks has been obtained. Finally, the loss of the contaminant elements Pb and Zn to the environment has been proven. 相似文献
67.
UNEXPECTED SUBSPACES OF TENSOR PRODUCTS 总被引:1,自引:0,他引:1
Sanchez Felix Cabello; Perez-Garcia David; Villanueva Ignacio 《Journal London Mathematical Society》2006,74(2):512-526
We describe complemented copies of 2 both in C(K1) C(K2) when at least one of the compact spaces Kiis not scattered and in L1(µ1)L1(µ2) when at least one of the measures is not atomic.The corresponding local construction gives uniformly complementedcopies of the in c0 c0. We continue the study of c0 c0 showing that it contains a complementedcopy of Stegall's space and proving that (c0 c0)' is isomorphicto , together with other results. In the last section we use Hardy spaces to find an isomorphiccopy of Lp in the space of compact operators from Lq to Lr,where 1 < p, q, r < and 1/r = 1/p + 1/q. 相似文献
68.
In this paper we continue with our work in Lederman and Wolanski (Ann Math Pura Appl 187(2):197–220, 2008) where we developed
a local monotonicity formula for solutions to an inhomogeneous singular perturbation problem of interest in combustion theory.
There we proved local monotonicity formulae for solutions ue{{u^\varepsilon}} to the singular perturbation problem and for u=limue{u=\lim{u^\varepsilon}} , assuming that both ue{{u^\varepsilon}} and u were defined in an arbitrary domain D{\mathcal{D}} in
\mathbbRN+1{\mathbb{R}^{N+1}} . In the present work we obtain global monotonicity formulae for limit functions u that are globally defined, while ue{{u^\varepsilon}} are not. We derive such global formulae from a local one that we prove here. In particular, we obtain a global monotonicity
formula for blow up limits u
0 of limit functions u that are not globally defined. As a consequence of this formula, we characterize blow up limits u
0 in terms of the value of a density at the blow up point. We also present applications of the results in this paper to the
study of the regularity of ∂{u > 0} (the flame front in combustion models). The fact that our results hold for the inhomogeneous singular perturbation problem
allows a very wide applicability, for instance to problems with nonlocal diffusion and/or transport. 相似文献
69.
The activation energies for the methyl exchange reactions between Cp2M-CH3 and H-CH3 have been calculated for M = Sc, Y and representative metals of the lanthanide family (La, Ce, Sm, Ho, Yb and Lu) with DFT(B3PW91) calculations with large-core pseudopotentials for M. The sigma-bond metathesis reactions are calculated to have lower activation energies for early lanthanides than for late lanthanides and any of group 3 metals. The relative activation barriers are analyzed using the NBO charge distributions in the reactant and in the transition states. It is shown that the methane needs to be polarized in the transition state as H((+delta))-CH3((-delta)) by the reactant, because this sigma-bond metathesis is best viewed as heterolytic cleavage of methane, leading to a proton transfer between two methyl groups in the field of an electropositive M metal. Early lanthanides, which are involved in strongly ionic metal-ligands bonds are thus associated with the lowest activation energies. The ionic radius and the steric effects influence the relative rates of reaction for the complexes of Sc, Y and Lu. In agreement with earlier works of Sherer et al., the experimental reactivity trends found by Tilley are reproduced best with Cp*2M-CH3 (Cp* = C5Me5) rather than Cp2M-CH3 (Cp = C5H5) because the steric bulk of C5Me5 deactivates most the complex where the metal has the smallest ionic radius (Sc). While the steric effects and the influence of the metal ionic radius cannot be neglected, these factors are not the only ones involved in determining the activation barriers of the sigma-bond metathesis reaction. 相似文献
70.
A synthetic strategy for fabricating a dense amine functionalized self-assembled monolayer (SAM) on hydroxylated surfaces is presented. The assembly steps are monitored by X-ray photoelectron spectroscopy, Fourier transform infrared- attenuated total reflection, atomic force microscopy, variable angle spectroscopic ellipsometry, UV-vis surface spectroscopy, contact angle wettability, and contact potential difference measurements. The method applies alkylbromide-trichlorosilane for the fabrication of the SAM followed by surface transformation of the bromine moiety to amine by a two-step procedure: S(N)2 reaction that introduces the hidden amine, phthalimide, followed by the removal of the protecting group and exposing the free amine. The use of phthalimide moiety in the process enabled monitoring the substitution reaction rate on the surface (by absorption spectroscopy) and showed first-order kinetics. The simplicity of the process, nonharsh reagents, and short reaction time allow the use of such SAMs in molecular nanoelectronics applications, where complete control of the used SAM is needed. The different molecular dipole of each step of the process, which is verified by DFT calculations, supports the use of these SAMs as means to tune the electronic properties of semiconductors and for better synergism between SAMs and standard microelectronics processes and devices. 相似文献