全文获取类型
收费全文 | 180篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 62篇 |
力学 | 13篇 |
数学 | 82篇 |
物理学 | 29篇 |
出版年
2023年 | 1篇 |
2022年 | 4篇 |
2021年 | 7篇 |
2020年 | 4篇 |
2019年 | 3篇 |
2018年 | 3篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 6篇 |
2014年 | 5篇 |
2013年 | 16篇 |
2012年 | 13篇 |
2011年 | 21篇 |
2010年 | 12篇 |
2009年 | 15篇 |
2008年 | 4篇 |
2007年 | 8篇 |
2006年 | 9篇 |
2005年 | 6篇 |
2004年 | 10篇 |
2003年 | 1篇 |
2002年 | 4篇 |
2001年 | 1篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1992年 | 4篇 |
1989年 | 3篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1977年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有186条查询结果,搜索用时 0 毫秒
101.
Predrag S.Stanimirovi 《数学研究通讯:英文版》2021,37(4):421-447
The aim of this paper is to systematize solutions of some systems of linear equations in terms of generalized inverses.As a significant application of the Moore-Penrose inverse,the best approximation solution to linear matrix equations (i.e.both least squares and the minimal norm) is considered.Also,characterizations of least squares solution and solution of minimum norm are given.Basic properties of the Drazin-inverse solution and the outer-inverse so-lution are present.Motivated by recent research,important least square prop-erties of composite outer inverses are collected. 相似文献
102.
Višnja Vrdoljak Prof. Dalibor Milić Marina Cindrić Dubravka Matković‐Čalogović Jana Pisk Marina Marković Predrag Novak 《无机化学与普通化学杂志》2009,635(8):1242-1248
New dinuclear pentacoordinate molybdenum(V) complexes, [Mo2VO3L2] [L = thiosemicarbazonato ligand: C6H4(O)CH:NN:C(S)NHR′ and C10H6(O)CH:NN:C(S)NHR′; R′ = H, CH3, C6H5) were obtained either by oxygen atom abstraction from MoVIO2L with triphenylphosphine or by using [Mo2O3(acac)4] in the reaction with the corresponding ligands H2L. Crystal and molecular structure of [Mo2O3{C6H4(O)CH:NN:C(S)NHC6H5}2] · CH3CN has been determined by the single‐crystal X‐ray diffraction method. 相似文献
103.
Stefan Stanimirovi Predrag Stanimirovi Marko Miladinovi Aleksandar Ili 《Applied mathematics and computation》2009,215(2):796-805
We introduce the notion of the Catalan matrix whose non-zero elements are expressions which contain the Catalan numbers arranged into a lower triangular Toeplitz matrix. Inverse of the Catalan matrix is derived. Correlations between the matrix and the generalized Pascal matrix are considered. Some combinatorial identities involving Catalan numbers, binomial coefficients and the generalized hypergeometric function are derived using these correlations. Moreover, an additional explicit representation of the Catalan number, as well as an explicit representation of the sum of the first m Catalan numbers are given. 相似文献
104.
Starting from algorithms introduced in [Ky M. Vu, An extension of the Faddeev’s algorithms, in: Proceedings of the IEEE Multi-conference on Systems and Control on September 3-5th, 2008, San Antonio, TX] which are applicable to one-variable regular polynomial matrices, we introduce two dual extensions of the Faddeev’s algorithm to one-variable rectangular or singular matrices. Corresponding algorithms for symbolic computing the Drazin and the Moore-Penrose inverse are introduced. These algorithms are alternative with respect to previous representations of the Moore-Penrose and the Drazin inverse of one-variable polynomial matrices based on the Leverrier-Faddeev’s algorithm. Complexity analysis is performed. Algorithms are implemented in the symbolic computational package MATHEMATICA and illustrative test examples are presented. 相似文献
105.
Systems such as fluid flows in channels and pipes or the complex Ginzburg–Landau system, defined over periodic domains, exhibit both continuous symmetries, translational and rotational, as well as discrete symmetries under spatial reflections or complex conjugation. The simplest, and very common symmetry of this type is the equivariance of the defining equations under the orthogonal group O(2). We formulate a novel symmetry reduction scheme for such systems by combining the method of slices with invariant polynomial methods, and show how it works by applying it to the Kuramoto–Sivashinsky system in one spatial dimension. As an example, we track a relative periodic orbit through a sequence of bifurcations to the onset of chaos. Within the symmetry-reduced state space we are able to compute and visualize the unstable manifolds of relative periodic orbits, their torus bifurcations, a transition to chaos via torus breakdown, and heteroclinic connections between various relative periodic orbits. It would be very hard to carry through such analysis in the full state space, without a symmetry reduction such as the one we present here. 相似文献
106.
Predrag Tanović 《Archive for Mathematical Logic》2007,46(5-6):517-527
We prove that a countable, complete, first-order theory with infinite dcl() and precisely three non-isomorphic countable models interprets a variant of Ehrenfeucht’s or Peretyatkin’s example. 相似文献
107.
Ratko Pavlović Predrag Kozić Snežana Mitić Ivan Pavlović 《Archive of Applied Mechanics (Ingenieur Archiv)》2009,79(12):1163-1171
The stochastic stability problem of an elastic, balanced rotating shaft subjected to action of axial forces at the ends is
studied. The shaft is of circular cross-section, it rotates at a constant rate about its longitudinal axis of symmetry. The
effect of rotatory inertia of the shaft cross-section is included in the present formulation. Each force consists of a constant
part and a time-dependent stochastic function. Closed form analytical solutions are obtained for simply supported boundary
conditions. By using the direct Liapunov method almost sure asymptotic stability conditions are obtained as the function of
stochastic process variance, damping coefficient, damping ratio, angular velocity, mode number and geometric and physical
parameters of the shaft. Numerical calculations are performed for the Gaussian process with a zero mean and as well as an
harmonic process with random phase. 相似文献
108.
Novak P Tomisić ZB Tepes P Lazarevski G Plavec J Turkalj G 《Organic & biomolecular chemistry》2005,3(1):39-47
Conformations of the 14-membered macrolide antibiotic oleandomycin and its 8-methylene-9-oxime derivative were determined in various solvents. The experimental NMR data--coupling constants and NOE contacts--were compared with the results of molecular modelling--molecular mechanics calculations and molecular dynamics simulations. The conformational changes, on the right-hand side of the 14-membered ring, affected mostly the 3JH2,H3 values and NOE crosspeaks H3 or H4 to H11. Oleandomycin was found to be present predominantly in the C3-C5 folded-in conformations in DMSO-d6 solution, whereas in buffered D2O, acetone-d6 and CDCl3, there was a mixture of folded-in and folded-out conformational families. The predominant conformation of the 8-methylene-oleandomycin-9-oxime derivative in solution was a folded-out one although different amounts of folded-in conformation were also present depending on the solvent. Oleandrose and desosamine sugar moieties adopted the usual and expected chair conformation. The conformation around the glycosidic bonds, governing the relative orientation of sugars vs. the lactone ring, showed a certain flexibility within two conformationally close families. We believe that by combining the experimental NMR data and the molecular modelling techniques, as reported in this paper, we have made significant progress in understanding the conformational behaviour and properties of macrolides. Our belief is based on our own current studies on oleandomycins as well as on the previously reported results and best practices concerning other macrolides. A rational for macrolide conformational studies and advances in methodology has been suggested accordingly. 相似文献
109.
Predrag Djurdjevi? Ratomir Jeli? Ljubinka Joksovi? Mirjana Cvijovi? 《Monatshefte für Chemie / Chemical Monthly》2006,12(2):717-735
Solution equilibria between aluminium(III) ion and L-aspartic acid were studied by potentiometric, 27Al, 13C, and 1H NMR measurements. Glass electrode equilibrium potentiometric studies were performed on solutions with ligand to metal concentration
ratios 1:1, 3:1, and 5:1 with the total metal concentration ranging from 0.5 to 5.0 mmol/dm3 in 0.1 mol/dm3 LiCl ionic medium, at 298 K. The pH of the solutions was varied from ca. 2.0 to 5.0. The non-linear least squares treatment of the data performed with the aid of the Hyperquad program, indicated
the formation of the following complexes with the respective stability constants log βp,q,r given in parenthesis (p, q, r are stoichiometric indices for metal, ligand, and proton, respectively): Al(HAsp)2+ (log β1,1,1 = 11.90 ± 0.02); Al(Asp)+ (log β1,1,0 = 7.90 ± 0.03); Al(OH)Asp0 (log β1,1,−1 = 3.32 ± 0.04); Al(OH)2Asp− (log β1,1−2 = −1.74 ± 0.08), and Al2(OH) Asp3+ (log β2,1,−1 = 6.30 ± 0.04). 27Al NMR spectra of Al3+ + aspartic acid solutions (pH 3.85) indicate that sharp symmetric resonance at δ∼10 ppm can be assigned to (1, 1, 0) complex. This resonance increases
in intensity and slightly broadens upon further increasing the pH. In Al(Asp)+ complex the aspartate is bound tridentately to aluminum. The 1H and 13C NMR spectra of aluminium + aspartic acid solutions at pH 2.5 and 3.0 indicate that β-methylene group undergoes the most pronounced changes upon coordination of aluminum as well as
α-carboxylate group in 13C NMR spectrum. Thus, in Al(HAsp)2+ which is the main complex in this pH interval the aspartic acid acts as a bidentate ligand with –COO− and –NH2 donors closing a five-membered ring. 相似文献
110.
The formation of various hydrolytic and mixed hydrolytic complexes of the aluminium(III) ion in the presence of glycine and L-alanine, has been studied in 0.5 mol dm?3 (Na)NO3 medium at 25deg;C, by emf method. The concentration ratios of amine acids to aluminium(III) were varied from 1 : 1 to 10 : 1. The least-squares treatment of the data obtained, in the absence of the amino acids, indicates the formation of the dimer, [Al2(OH)2]4+, and monomer, [AlOH]2+, with the stability constants log β22 = ?7.03 ± 0.03 and log β11 = ?5.65 ± 0.09, respectively. At pH values higher then ~4.0 formation of the trimer [Al3(OH)4]5+ (log β34 = ?12.60 ± 0.08) becomes significant. In the presence of amino acids the evidence has been found for the formation of [Al2(OH)4]2+ (log β24 = ?15.65 ± 0.09). Besides the formation of the pure hydrolytic complexes, equilibria in the title systems can be explained by assuming the main reaction products to have the compositions [Al(OH)3Gly] (log β131 = ?7.53 ± 0.04), [Al2(OH)2(Gly)2] (log β222 = 6.56 ± 0.09) and [Al(OH)3Ala] (log β131 = ?7.70 ± 0.03), [Al2(OH)2Ala2] (log β222 = 7.23 ± 0.07). 相似文献