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1.
2.
The use of an in situ generated Ni(0) catalyst associated with 2,2'-bipyridine or N,N'-bis(2,6-diisopropylphenyl)dihydroimidazol-2-ylidene (SIPr) as a ligand and NaO-t-Bu as the base for the intramolecular coupling of aryl chlorides with amines is described. The procedure has been applied to the formation of five-, six-, and seven-membered rings. [reaction: see text] 相似文献
3.
Phosphorescence has been simultaneously observed from both a 3π, π* and a 3n,π* level of 5-methylbicyclo-[4.3.01,5non-1-en-3-one. The emission from the higher energy 3n,π* state, which is in thermal equilibrium with the 3π,π* state, is quenched by lowering the temperature and also quenched by increasing the solvent polarity so as to raise the energy of the 3n,π* state relative to the 3π,π* state. 相似文献
4.
5.
Ab initio HF/6-31G and DFT B3LYP/6-31G (d,p) calculations for the cleavage of Menger’s aliphatic amide 3 (a peptidase model) under physiological conditions, indicate that the rate limiting step in the cleavage process is a proton transfer from one of the carboxyl groups onto the amidic carbonyl oxygen. The acceleration in rates is mainly due to proximity orientation, and the effect of pseudoallylic strain relief on the rates is negligible. Moreover, the calculations reveal that the mode and the mechanism of the amide cleavage are largely dependent on the pH of the reaction. These results explain the findings that peptidase enzymes are reactive around neutral pH while their activities vanish under basic medium. 相似文献
6.
Numerical modeling of multiphase flow generally requires a special procedure at the solid wall in order to be consistent with Young's law for static contact angles. The standard approach in the lattice Boltzmann method, which consists of imposing fictive densities at the solid lattice sites, is shown to be deficient for this task. Indeed, fictive mass transfer along the boundary could happen and potentially spoil the numerical results. In particular, when the contact angle is less than 90 degrees, the deficiencies of the standard model are major. Various videos that demonstrate this behavior are provided (Supporting Information). A new approach is proposed and consists of directly imposing the contact angle at the boundaries in much the same way as Dirichlet boundary conditions are generally imposed. The proposed method is able to retrieve analytical solutions for static contact angles in the case of straight and curved boundaries even when variable density and viscosity ratios between the phases are considered. Although the proposed wetting boundary condition is shown to significantly improve the numerical results for one particular class of lattice Boltzmann model, it is believed that other lattice Boltzmann multiphase schemes could also benefit from the underlying ideas of the proposed method. The proposed algorithm is two‐dimensional, and the D2Q9 lattice is used. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
7.
[reaction: see text] Reductive cleavage of the carbon-sulfur bond present in S-alkyl-thionocarbonates (xanthates) was achieved by high-yielding, tin-free radical reactions based on phosphorus reagents. The combination hypophosphorous acid/triethylamine/AIBN led to fast, efficient, and smooth formation of the alkane. Reduction with diethyl phosphite was sufficiently slow to permit sequential intermolecular addition of a 2-oxoalkyl xanthate onto an olefin followed by cleavage of the newly formed carbon-sulfur bond. 相似文献
8.
Karaman R 《Journal of computer-aided molecular design》2010,24(12):961-970
DFT calculation results for intramolecular proton transfer reactions in Kirby’s enzyme models 1–7 reveal that the reaction rate is quite responsive to geometric disposition, especially to distance between the two reactive
centers, r
GM, and the angle of attack, α (the hydrogen bonding angle). Hence, the study on the systems reported herein could provide a
good basis for designing aza nucleoside prodrug systems that are less hydrophilic than their parental drugs and can be used,
in different dosage forms, to release the parent drug in a controlled manner. For example, based on the calculated log EM,
the cleavage process for prodrug 1ProD is predicted to be about 1010 times faster than that for prodrug 7ProD and about 104 times faster than prodrug 3ProD: rate
1ProD
> rate
3ProD
> rate
7ProD
. Hence, the rate by which the prodrug releases the aza nucleoside drug can be determined according to the structural features
of the linker (Kirby’s enzyme model). 相似文献
9.
In this work, we are interested to obtain some result of existence and nonex- istence of positive weak solution for the following p-Laplacian system
{-△piui=λifi(u1,^…,um),inΩ, i=1,...,m, ui=0,
on δΩ,Vi=1,…,m,
where △piz = div(|△z|^pi-2△Z), Pi ≥ 1,λi,1 ≤ i ≤ m are a positive parameter, and Ω is a bounded domain in IR^N with smooth boundary δΩ. The proof of the main results is based to the method of sub-supersolutions. 相似文献
{-△piui=λifi(u1,^…,um),inΩ, i=1,...,m, ui=0,
on δΩ,Vi=1,…,m,
where △piz = div(|△z|^pi-2△Z), Pi ≥ 1,λi,1 ≤ i ≤ m are a positive parameter, and Ω is a bounded domain in IR^N with smooth boundary δΩ. The proof of the main results is based to the method of sub-supersolutions. 相似文献
10.
Mahalingam V Naccache R Vetrone F Capobianco JA 《Chemical communications (Cambridge, England)》2011,47(12):3481-3483
The intensity of high energy UV and blue upconverted emissions of Tm(3+) ions in Tm(3+)/Yb(3+) co-doped LiYF(4) colloidal nanocrystals was selectively reduced compared to the NIR emission at 802 nm. This was achieved by doping a small amount of Dy(3+) ions into the host matrix. 相似文献