全文获取类型
收费全文 | 6917篇 |
免费 | 467篇 |
国内免费 | 655篇 |
专业分类
化学 | 442篇 |
晶体学 | 4篇 |
力学 | 524篇 |
综合类 | 174篇 |
数学 | 6355篇 |
物理学 | 540篇 |
出版年
2024年 | 6篇 |
2023年 | 75篇 |
2022年 | 79篇 |
2021年 | 125篇 |
2020年 | 136篇 |
2019年 | 152篇 |
2018年 | 164篇 |
2017年 | 179篇 |
2016年 | 176篇 |
2015年 | 150篇 |
2014年 | 294篇 |
2013年 | 444篇 |
2012年 | 290篇 |
2011年 | 396篇 |
2010年 | 355篇 |
2009年 | 456篇 |
2008年 | 460篇 |
2007年 | 443篇 |
2006年 | 443篇 |
2005年 | 383篇 |
2004年 | 294篇 |
2003年 | 336篇 |
2002年 | 304篇 |
2001年 | 284篇 |
2000年 | 239篇 |
1999年 | 236篇 |
1998年 | 215篇 |
1997年 | 203篇 |
1996年 | 136篇 |
1995年 | 104篇 |
1994年 | 82篇 |
1993年 | 69篇 |
1992年 | 50篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 17篇 |
1988年 | 17篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 28篇 |
1984年 | 26篇 |
1983年 | 15篇 |
1982年 | 21篇 |
1981年 | 17篇 |
1980年 | 21篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1974年 | 3篇 |
排序方式: 共有8039条查询结果,搜索用时 31 毫秒
991.
Let be a finite simple graph. For , the difference of , where is the neighborhood of and is called the critical difference of . is called a critical set if equals the critical difference and is the intersection of all critical sets. is the union of all critical independent sets. An independent set is an inclusion minimal set with if no proper subset of has positive difference.A graph is called a König–Egerváry graph if the sum of its independence number and matching number equals .In this paper, we prove a conjecture which states that for any graph the number of inclusion minimal independent set with is at least the critical difference of the graph.We also give a new short proof of the inequality .A characterization of unicyclic non-König–Egerváry graphs is also presented and a conjecture which states that for such a graph , the critical difference equals , is proved.We also make an observation about using Edmonds–Gallai Structure Theorem as a concluding remark. 相似文献
992.
Let and be the domination number and the game domination number of a graph , respectively. In this paper -maximal graphs are introduced as the graphs for which holds. Large families of -maximal graphs are constructed among the graphs in which their sets of support vertices are minimum dominating sets. -maximal graphs are also characterized among the starlike trees, that is, trees which have exactly one vertex of degree at least . 相似文献
993.
In this paper, we show the relationship between two seemingly unrelated approximation techniques. On the one hand, a certain class of Gaussian process-based interpolation methods, and on the other hand inverse distance weighting, which has been developed in the context of spatial analysis where there is often a need for interpolating from irregularly spaced data to produce a continuous surface. We develop a generalization of inverse distance weighting and show that it is equivalent to the approximation provided by the class of Gaussian process-based interpolation methods. The equivalence is established via an elegant application of Riesz representation theorem concerning the dual of a Hilbert space. It is thus demonstrated how a classical theorem in linear algebra connects two disparate domains. 相似文献
994.
《Annals of Pure and Applied Logic》2020,171(3):102754
We introduce a new axiom called inductive dichotomy, a weak variant of the axiom of inductive definition, and analyze the relationships with other variants of inductive definition and with related axioms, in the general second order framework, including second order arithmetic, second order set theory and higher order arithmetic. By applying these results to the investigations on the determinacy axioms, we show the following. (i) Clopen determinacy is consistency-wise strictly weaker than open determinacy in these frameworks, except second order arithmetic; this is an enhancement of Schweber–Hachtman separation of open and clopen determinacy into the consistency-wise separation. (ii) Hausdorff–Kuratowski hierarchy of differences of opens is faithfully reflected by the hierarchy of consistency strengths of corresponding parameter-free determinacies in the aforementioned frameworks; this result is valid also in second order arithmetic only except clopen determinacy. 相似文献
995.
Though the central role of Gösta Mittag-Leffler in the promotion of specialized, research-oriented mathematics at Stockholms Högskola is widely acknowledged, the specific social and technical means by which he sought to cultivate a fledgling research community there during the early- to mid-1880s have received little attention. In particular, a detailed study of the relationship of his own research activity to that of his first Swedish students is absent from the existing literature.Through the juxtaposition of their research activities and unpublished correspondence, this paper explores Mittag-Leffler's active and deliberate efforts to engage his students Ivar Bendixson and Edvard Phragmén in open problems within his own research agenda, support them through his institutional connections, and instill within them norms concerning research ideologies, practices of communication and criticism, and frameworks for shared knowledge. It also illuminates the extent to which his teachings took root in at least one student to emerge from his program, who would perpetuate the mathematical practices set in place by his teacher and set forth on the international stage to promote his newly-acquired system of values. 相似文献
996.
Suruchi Singh Swarn Singh 《Numerical Methods for Partial Differential Equations》2020,36(5):1028-1043
A high order modified nodal bi-cubic spline collocation method is proposed for numerical solution of second-order elliptic partial differential equation subject to Dirichlet boundary conditions. The approximation is defined on a square mesh stencil using nine grid points. The solution of the method exists and is unique. Convergence analysis has been presented. Moreover, the superconvergent phenomena can be seen in proposed one step method. The numerical results clearly exhibit the superiority of the new approximation, in terms of both accuracy and computational efficiency. 相似文献
997.
Based on the generalized Laguerre and Hermite functions, we construct two types of Birkhoff-type interpolation basis functions. The explicit expressions are derived, and fast and stable algorithms are provided for computing these basis functions. As applications, some well-conditioned collocation methods are proposed for solving various second-order differential equations in unbounded domains. Numerical experiments illustrate that our collocation methods are more efficient than the standard Laguerre/Hermite collocation approaches. 相似文献
998.
In this paper, we first present an adaptive nonmonotone term to improve the efficiency of nonmonotone line search, and then an active set identification technique is suggested to get more efficient descent direction such that it improves the local convergence behavior of algorithm and decreases the computation cost. By means of the adaptive nonmonotone line search and the active set identification technique, we put forward a global convergent gradient-based method to solve the nonnegative matrix factorization (NMF) based on the alternating nonnegative least squares framework, in which we introduce a modified Barzilai-Borwein (BB) step size. The new modified BB step size and the larger step size strategy are exploited to accelerate convergence. Finally, the results of extensive numerical experiments using both synthetic and image datasets show that our proposed method is efficient in terms of computational speed. 相似文献
999.
In this paper, we consider regular automorphism groups of graphs in the RT2 family and the Davis‐Xiang family and amorphic abelian Cayley schemes from these graphs. We derive general results on the existence of non‐abelian regular automorphism groups from abelian regular automorphism groups and apply them to the RT2 family and Davis‐Xiang family and their amorphic abelian Cayley schemes to produce amorphic non‐abelian Cayley schemes. 相似文献
1000.
The existence of exponential attractor for the diffusive Hindmarsh-Rose equations on a three-dimensional bounded domain in the study of neurodynamics is proved through uniform estimates and a new theorem on the squeezing property of the abstract reaction-diffusion equation established in this paper. This result on the exponential attractor infers that the global attractor whose existence has been proved in [22] for the diffusive Hindmarsh-Rose semiflow has a finite fractal dimension. 相似文献