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131.
Some comparison results are formulated for systems of differential inequalities with different initial points. 相似文献
132.
Tadeusz Jankowski 《Czechoslovak Mathematical Journal》2004,54(4):843-854
We apply the method of quasilinearization to multipoint boundary value problems for ordinary differential equations showing that the corresponding monotone iterations converge to the unique solution of our problem and this convergence is quadratic. 相似文献
133.
134.
Andrzej Frankowski Dariusz DeredasEstelle Dubost François GessierStefan Jankowski Markus NeuburgerCzes?awa Seliga Théophile TschamberKamil Weinberg 《Tetrahedron》2003,59(34):6503-6520
The syntheses of imidazolo[1,5]hexopiperidinoses 2-6 and imidazol-4(5)-yl C-glycosides 7-9 are reported. The crucial step of this approach relies upon the SN2-type cyclisation of selectively protected C(1), C(2), C(3) and C(5)-substituted 1-[imidazol-4(5)-yl]pentitols in which the imidazole nitrogen or the C(1)-connected oxygen are involved as the competitive nucleophilic centers, respectively. Six selected imidazolosugars were evaluated as potential inhibitors of glycosidases. 相似文献
135.
Rafa??Podeszwa Leszek. Z.?StolarczykEmail author Karol?Jankowski Krzysztof?Rubiniec 《Theoretical chemistry accounts》2003,109(6):309-315
To gain some insight into the structure and physical significance of the multiple solutions to the coupled-cluster doubles (CCD) equations corresponding to the Pariser–Parr–Pople model of cyclic polyenes, complete solutions to the CCD equations for the 1A 1g - states of benzene are obtained by means of the homotopy method. By varying the value of the resonance integral ß from –5.0 to –0.5 eV, we cover the so-called weakly, moderately, and strongly correlated regimes of the model. For each value of ß, 230 CCD solutions are obtained. It turned out, however, that only for a few solutions a correspondence with some physical states can be established. It has also been demonstrated that, unlike for the standard methods of solving CCD equations, some of the multiple solutions to the CCD equations can be attained by means of the iterative process based on Pulay's direct inversion in the iterative subspace approach. 相似文献
136.
Results are presented from a numerical investigation of turbulent source flow between two discs, both of which are stationary or corotating. Parabolic flow was assumed and the Box Method used to obtain marching solutions of the governing equations. Turbulence modelling was based on extensions of classical eddy-viscosity/mixing-length concepts which reflect the influences of divergence of the mean-flow streamlines and non-isotropic Reynolds stresses due to disc rotation. The predictions for the rotating case are the first local results available. For the stationary case, earlier work has been extended by the use of empirical formulae for reverse transition and inclusion of the influence of streamline divergence. Comparisons with limited data for stationary and corotating discs show reasonable agreement. Although the turbulence models are probably not optimum, they provide an adequate basis for engineering studies of turbulent source flow between corotating and stationary discs until more extensive and reliable empirical information is available. 相似文献
137.
Monika Bilska-Markowska Wojciech Jankowski Marcin Hoffmann Marcin Ka
mierczak 《Molecules (Basel, Switzerland)》2022,27(17)
Herein, we present the application of fluorinated carbohydrate-derived building blocks for α-hydroxy β-fluoro/β-trifluoromethyl and unsaturated phosphonates synthesis. Pudovik and Horner–Wadsworth–Emmons reactions were applied to achieve this goal. The proposed pathway of the key reactions is supported by the experimental results, as well as quantum chemical calculations. The structure of the products was established by spectroscopic (1D, 2D NMR) and spectrometric (MS) techniques. Based on our data received, we claim that the progress of the Pudovik and HWE reactions is significantly influenced by the acidic protons present in the molecules as assessed by pKa values of the reagent. 相似文献
138.
K. Jankowski K. Kowalski K. Rubiniec J. Wasilewski 《International journal of quantum chemistry》1998,67(4):205-219
The impact of the choice of molecular orbital sets on the results of single-reference-state coupled-cluster (CC) methods was studied for the H4 model. This model offers a straightforward way of taking into account all possible symmetry-adapted orbitals. Moreover, the degree of quasi-degeneracy of its ground state can be varied over a wide range by changing its geometry. The CCD, CCSD, and CCSDT approaches are considered. Surfaces representing the dependence of the energy on the parameters defining the orbitals are obtained. It is documented that for every method there exist alternative orbital sets which allow one to obtain more accurate energies than the standard (HF, BO, and NO) ones. However, for many of the former orbital sets, one obtains relatively large one-body amplitudes or one may encounter problems with solving the CC equations by conventional methods. An interesting variety of orbitals which might be useful for studies of quasi-degenerate states by the CCD method was found. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 67: 205–219, 1998 相似文献
139.
140.
For states of many-electron systems disclosing various degrees of quasidegeneracy, we have carried out comparative studies of Kohn–Sham orbitals (KSO) generated for several xc-potentials, Brueckner orbitals (BO) represented by the Brueckner-coupled cluster orbitals, and Hartree–Fock (HF) orbitals by means of criteria directly related to the orbital structure which are based on relative distance indices for various pairs of equidimensional subspaces defined by the KSO and BO basis sets. We have found that both for weak and strong quasidegeneracy there are systems for which the KSO–BO distances are larger than the BO–HF ones. For strongly quasidegenerate states it is found that the distance indices are the largest for hybrid potentials, and that the subspaces spanned by KSOs are closer to those spanned by HF orbitals than by BOs. Hence, our results do not support the recently formulated expectations concerning the similarity of Brueckner orbitals and Kohn–Sham orbitals, including those corresponding to purely local exchange-correlation potentials. 相似文献