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41.
An analysis is performed to study a laminar boundary layer flow over a porous flat plate with injection or suction imposed at the wall. The basic equations of this problem are reduced to a system of nonlinear ordinary differential equations by means of appropriate transformations. These equations are solved analytically by the optimal homotopy asymptotic method (OHAM), and the solutions are compared with the numerical solution (NS). The effect of uniform suction/injection on the heat transfer and velocity profile is discussed. A constant surface temperature in thermal boundary conditions is used for the horizontal flat plate.  相似文献   
42.
MP2/aug‐cc‐pVTZ calculations are performed on complexes of YO3 (Y = S, Se) with a series of electron‐donating chalcogen bases YHX (X = H, Cl, Br, CCH, NC, OH, OCH3). These complexes are formed through the interaction of a positive electrostatic potential region (π‐hole) on the YO3 molecule with the negative region in YHX. Interaction energies of the binary O3Y???YHX complexes are in the range of ?4.37 to ?12.09 kcal/mol. The quantum theory of atoms in molecules and the natural bond orbital analysis were applied to characterize the nature of interactions. It was found that the formation and stability of these binary complexes are ruled mainly by electrostatic effects, although the electron charge transfer from YHX to YO3 unit also seems to play an important role. In addition, mutual influence between the Y???N and Y???Y interactions is studied in the ternary HCN???O3Y???YHX complexes. The results indicate that the formation of a Y???N interaction tends to weaken Y???Y bond in the ternary systems. Although the Y???Y interaction is weaker than the Y???N one, however, both types of interactions seem to compete with each other in the HCN???O3Y???YHX complexes. © 2016 Wiley Periodicals, Inc.  相似文献   
43.
In this study, the effects of intracellular delivery of various concentrations of gallic acid (GA) as a semistable antioxidant, gallic acid-loaded mesoporous silica nanoparticles (MSNs-GA), and cellular uptake of nanoparticles into Caco-2 cells were investigated. MSNs were synthesized and loaded with GA, then characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, N2 adsorption isotherms, X-ray diffraction, and thermal gravimetric analysis. The cytotoxicity of MSNs and MSNs-GA at low and high concentrations were studied by means of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test and flow cytometry. MSNs did not show significant toxicity in various concentrations (0–500 μg/ml) on Caco-2 cells. For MSNs-GA, cell viability was reduced as a function of incubation time and different concentrations of nanoparticles. The in vitro GA release from MSNs-GA exhibited the same antitumor properties as free GA on Caco-2 cells. Flow cytometry results confirmed those obtained using MTT assay. TEM and fluorescent microscopy confirmed the internalization of MSNs by Caco-2 cells through nonspecific cellular uptake. MSNs can easily internalize into Caco-2 cells without deleterious effects on cell viability. The cell viability of Caco-2 cells was affected during MSNs-GA uptake. MSNs could be designed as suitable nanocarriers for antioxidants delivery.  相似文献   
44.
Generalized curvilinear coordinates, as, e.g., polyspherical coordinates, are in general better adapted to the resolution of the nuclear Schro?dinger equation than rectilinear ones like the normal mode coordinates. However, analytical expressions of the kinetic energy operators (KEOs) for molecular systems in polyspherical coordinates may be prohibitively complicated for large systems. In this paper we propose a method to generate a KEO numerically and bring it to a form practicable for dynamical calculations. To examine the new method we calculated vibrational spectra and eigenenergies for nitrous acid (HONO) and compare it with results obtained with an exact analytical KEO derived previously [F. Richter, P. Rosmus, F. Gatti, and H.-D. Meyer, J. Chem. Phys. 120, 6072 (2004)]. In a second example we calculated π → π* photoabsorption spectrum and eigenenergies of ethene (C(2)H(4)) and compared it with previous work [M. R. Brill, F. Gatti, D. Lauvergnat, and H.-D. Meyer, Chem. Phys. 338, 186 (2007)]. In this ethene study the dimensionality was reduced from 12 to 6 by freezing six internal coordinates. Results for both molecules show that the proposed method for obtaining an approximate KEO is reliable for dynamical calculations. The error in eigenenergies was found to be below 1 cm(-1) for most states calculated.  相似文献   
45.
A simple, one-pot, efficient and novel protocol has been developed for direct synthesis of symmetrical organic disulfides by domino reaction of aryl halides and K2S in the presence of magnetic Fe3O4 nanoparticles as a readily available, highly efficient and recyclable catalyst. A variety of diaryl disulfides can be obtained in good-to-excellent yields up to 98%.  相似文献   
46.
Density functional theory has been used to study the geometries, electronic structure and harmonic vibrational frequencies of the oxocarbons and the pseudooxocarbons of group VI. The ability of the maximum hardness principle for predicting the stable structures of oxocarbons and pseudooxocarbons of group VI is tested by analyzing the results of these calculations. To obtain the stable structure, the geometrical parameters and stability of molecules are compared and analyzed. Bond orders of candidate molecules are calculated by using natural bond orbital analysis. Except selenium derivatives, atoms in molecule calculations prove being useful for studying the nature of carbon heteroatom bond. Chemical hardness is also reported. This study reveals that (1) DFT gives very similar geometries and energies to ab-initio methods and (2) the maximum hardness principle (MHP) is not verified for some of these structures. Data for C6Se6, which are new, are presented in this work.  相似文献   
47.
Alumina supported ammonium fluoride was found as an efficient reagent for the synthesis of 1,2,4‐oxadi‐azoles of amidoximes under solvent free conditions using microwave irradiation. This method is a one‐pot, easy, rapid, and high‐yielding reaction for the synthesis of 1,2,4‐oxadiazole derivatives from amidoximes and acyl chlorides. Reaction of amidoximes with acylchlorides in the presence of alumina without ammonium fluoride gave only the corresponding O‐acylamidoximes as major product.  相似文献   
48.
A new method is reported for the synthesis of symmetric diaryl and dialkyl disulfides from aryl and alkyl halides in the presence of copper using potassium 5-methyl-1,3,4-oxadiazole-2-thiolate as the base, ligand, and sulfur-transfer reagent.  相似文献   
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