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991.
This paper continues the work about the nonexistence of some complete metrics on the product of two manifolds studied by Tam and Yu (Asian J. Math., 14(2):235–242, 2010), and is motivated by the result of Tosatti (Commun. Anal. Geom., 15(5):1063–1086, 2007). We generalize the corresponding results of Tam and Yu (Asian J. Math., 14(2):235–242, 2010) to the almost-Hermitian case. 相似文献
992.
Generalized polymatroids are a family of polyhedra with several nice properties and applications. One property of generalized polymatroids used widely in existing literature is “total dual laminarity;” we make this notion explicit and show that only generalized polymatroids have this property. Using this we give a polynomial-time algorithm to check whether a given linear program defines a generalized polymatroid, and whether it is integral if so. Additionally, whereas it is known that the intersection of two integral generalized polymatroids is integral, we show that no larger class of polyhedra satisfies this property. 相似文献
993.
Tamás Erdélyi 《Constructive Approximation》2014,39(2):367-384
We prove the right Lax-type inequality on subarcs of the unit circle of the complex plane for complex algebraic polynomials of degree n having no zeros in the open unit disk. This is done by establishing the right Bernstein–Szeg?–Videnskii type inequality for real trigonometric polynomials of degree at most n on intervals shorter than the period. The paper is closely related to recent work by B. Nagy and V. Totik. In fact, their asymptotically sharp Bernstein-type inequality for complex algebraic polynomials of degree at most n on subarcs of the unit circle is recaptured by using more elementary methods. Our discussion offers a somewhat new way to see V.S. Videnskii’s Bernstein and Markov type inequalities for trigonometric polynomials of degree at most n on intervals shorter than a period, two classical polynomial inequalities first published in 1960. A new Riesz–Schur type inequality for trigonometric polynomials is also established. Combining this with Videnskii’s Bernstein-type inequality gives Videnskii’s Markov-type inequality immediately. 相似文献
994.
Márton Elekes Tamás Keleti András Máthé 《Journal of Fourier Analysis and Applications》2013,19(3):545-576
Let us say that an element of a given family $\mathcal{A}$ of subsets of ? d can be reconstructed using n test sets if there exist T 1,…,T n ?? d such that whenever $A,B\in\mathcal{A}$ and the Lebesgue measures of A∩T i and B∩T i agree for each i=1,…,n then A=B. Our goal will be to find the least such n. We prove that if $\mathcal{A}$ consists of the translates of a fixed reasonably nice subset of ? d then this minimum is n=d. To obtain this we prove the following two results. (1) A translate of a fixed absolutely continuous function of one variable can be reconstructed using one test set. (2) Under rather mild conditions the Radon transform of the characteristic function of K (that is, the measure function of the sections of K), (R θ χ K )(r)=λ d?1(K∩{x∈? d :〈x,θ〉=r}) is absolutely continuous for almost every direction θ. These proofs are based on techniques of harmonic analysis. We also show that if $\mathcal{A}$ consists of the enlarged homothetic copies rE+t (r≥1,t∈? d ) of a fixed reasonably nice set E?? d , where d≥2, then d+1 test sets reconstruct an element of $\mathcal{A}$ , and this is optimal. This fails in ?: we prove that a closed interval, and even a closed interval of length at least 1 cannot be reconstructed using two test sets. Finally, using randomly constructed test sets, we prove that an element of a reasonably nice k-dimensional family of geometric objects can be reconstructed using 2k+1 test sets. An example from algebraic topology shows that 2k+1 is sharp in general. 相似文献
995.
Attila Bernáth Tamás Király Erika Renáta Kovács Gergely Mádi-Nagy Gyula Pap Júlia Pap Jácint Szabó László Végh 《Central European Journal of Operations Research》2013,21(4):699-712
We investigate the multiplayer multicommodity flow problem: several players have different networks and commodities over a common node set. Pairs of players have contracts where one of them agrees to route the flow of the other player (up to a given capacity) between two specified nodes. In return, the second player pays an amount proportional to the flow value. We show that the social optimum can be computed by linear programming, and we propose algorithms based on column generation and Lagrangian relaxation. In contrast, we prove that it is hard to decide if an equilibrium solution exists, although some natural conditions guarantee its existence. 相似文献
996.
Tamás Titkos 《Acta Mathematica Hungarica》2013,140(1-2):151-161
We present a new approach for the Lebesgue decomposition of finitely additive measures (or contents, for short). Using the recently proved results of Hassi, Sebestyén and de Snoo, we show that the Lebesgue decomposition of contents exists, and corresponds to the Lebesgue decomposition of their induced forms. Additionally, we also present some new results related to the almost dominated part of a form (resp., a content). 相似文献
997.
In the simplest case, consider a \({\mathbb{Z}^d}\) -periodic (d ≥ 3) arrangement of balls of radii < 1/2, and select a random direction and point (outside the balls). According to Dettmann’s first conjecture, the probability that the so determined free flight (until the first hitting of a ball) is larger than t > > 1 is \({\sim\frac{C}{t}}\) , where C is explicitly given by the geometry of the model. In its simplest form, Dettmann’s second conjecture is related to the previous case with tangent balls (of radii 1/2). The conjectures are established in a more general setup: for \({\mathcal{L}}\) -periodic configuration of—possibly intersecting—convex bodies with \({\mathcal{L}}\) being a non-degenerate lattice. These questions are related to Pólya’s visibility problem (Arch Math Phys Ser 2:135–142, 1918), to theories of Bourgain et al. (Commun Math Phys 190:491–508,1998), and of Marklof–Strömbergsson (Ann Math 172:1949–2033,2010). The results also provide the asymptotic covariance of the periodic Lorentz process assuming it has a limit in the super-diffusive scaling, a fact if d = 2 and the horizon is infinite. 相似文献
998.
We revisit an early example of a nonlinear oscillator that exhibits chaotic motions when subjected to periodic excitation: the magneto-elastically buckled beam. In the paper of Moons and Holmes (1980) [1] magnetic field calculations were outlined but not carried through; instead the nonlinear forces responsible for creation of a two-well potential and buckling were fitted to a polynomial function after reduction to a single mode model. In the present paper we compute the full magnetic field and use it to approximate the forces acting on the beam, also using a single mode reduction. This provides a complete model that accurately predicts equilibria, bifurcations, and free oscillation frequencies of an experimental device. We also compare some periodic, transient and chaotic motions with those obtained by numerical simulations of the single mode model, further illustrating the rich dynamical behavior of this simple electromechanical system. 相似文献
999.
1000.
István M. Mándity Edit Wéber Tamás A. Martinek Dr. Gábor Olajos Gábor K. Tóth Prof. Dr. Elemér Vass Dr. Ferenc Fülöp Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(12):2171-2175
Assembly language : The programmed sequences of stereochemical building blocks lead to novel biomimetic helices. The rational design approach offers new possibilities for creating periodic secondary structures.