全文获取类型
收费全文 | 22482篇 |
免费 | 1768篇 |
国内免费 | 1088篇 |
专业分类
化学 | 4783篇 |
晶体学 | 15篇 |
力学 | 1023篇 |
综合类 | 91篇 |
数学 | 8251篇 |
物理学 | 4984篇 |
综合类 | 6191篇 |
出版年
2024年 | 35篇 |
2023年 | 184篇 |
2022年 | 309篇 |
2021年 | 417篇 |
2020年 | 480篇 |
2019年 | 496篇 |
2018年 | 381篇 |
2017年 | 444篇 |
2016年 | 673篇 |
2015年 | 605篇 |
2014年 | 949篇 |
2013年 | 1444篇 |
2012年 | 993篇 |
2011年 | 1107篇 |
2010年 | 942篇 |
2009年 | 1248篇 |
2008年 | 1391篇 |
2007年 | 1529篇 |
2006年 | 1300篇 |
2005年 | 992篇 |
2004年 | 884篇 |
2003年 | 940篇 |
2002年 | 893篇 |
2001年 | 741篇 |
2000年 | 734篇 |
1999年 | 655篇 |
1998年 | 635篇 |
1997年 | 481篇 |
1996年 | 446篇 |
1995年 | 374篇 |
1994年 | 334篇 |
1993年 | 340篇 |
1992年 | 311篇 |
1991年 | 207篇 |
1990年 | 203篇 |
1989年 | 202篇 |
1988年 | 223篇 |
1987年 | 139篇 |
1986年 | 100篇 |
1985年 | 119篇 |
1984年 | 93篇 |
1983年 | 29篇 |
1982年 | 56篇 |
1981年 | 51篇 |
1980年 | 53篇 |
1979年 | 43篇 |
1978年 | 33篇 |
1977年 | 35篇 |
1976年 | 30篇 |
1973年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
The synchronization problem of two different dynamical systems is considered by employing mode decomposition approach in this paper. Synchronization of non-identical coupled dynamical systems with non-chaotic attractors, i.e., equilibria, periodic and quasi-periodic solutions, is investigated analytically and numerically. Some results are obtained by this method. Some examples, supported by numerical simulation, are presented to illustrate the conciseness and effectiveness of the approach. 相似文献
993.
994.
995.
Ieva
Dauickait Amos S. Lawless Jennifer A. Scott Peter Jan van Leeuwen 《Numerical Linear Algebra with Applications》2020,27(5)
We consider the large sparse symmetric linear systems of equations that arise in the solution of weak constraint four‐dimensional variational data assimilation, a method of high interest for numerical weather prediction. These systems can be written as saddle point systems with a 3 × 3 block structure but block eliminations can be performed to reduce them to saddle point systems with a 2 × 2 block structure, or further to symmetric positive definite systems. In this article, we analyse how sensitive the spectra of these matrices are to the number of observations of the underlying dynamical system. We also obtain bounds on the eigenvalues of the matrices. Numerical experiments are used to confirm the theoretical analysis and bounds. 相似文献
996.
We consider the random‐cluster model (RCM) on with parameters p∈(0,1) and q ≥ 1. This is a generalization of the standard bond percolation (with edges open independently with probability p) which is biased by a factor q raised to the number of connected components. We study the well‐known Fortuin‐Kasteleyn (FK)‐dynamics on this model where the update at an edge depends on the global geometry of the system unlike the Glauber heat‐bath dynamics for spin systems, and prove that for all small enough p (depending on the dimension) and any q>1, the FK‐dynamics exhibits the cutoff phenomenon at with a window size , where λ∞ is the large n limit of the spectral gap of the process. Our proof extends the information percolation framework of Lubetzky and Sly to the RCM and also relies on the arguments of Blanca and Sinclair who proved a sharp mixing time bound for the planar version. A key aspect of our proof is the analysis of the effect of a sequence of dependent (across time) Bernoulli percolations extracted from the graphical construction of the dynamics, on how information propagates. 相似文献
997.
Yuxin Wang Huafei Sun Shoudong Huang Yang Song 《Mathematical Methods in the Applied Sciences》2020,43(2):486-511
This paper focuses on using the first curvature κ(t) of trajectory to describe the stability of linear time-invariant system. We extend the results for two and three-dimensional systems (Wang, Sun, Song et al, arXiv:1808.00290) to n-dimensional systems. We prove that for a system , (a) if there exists a measurable set whose Lebesgue measure is greater than zero, such that or does not exist for any initial value in this set, then the zero solution of the system is stable; (b) if the matrix A is invertible, and there exists a measurable set whose Lebesgue measure is greater than zero, such that for any initial value in this set, then the zero solution of the system is asymptotically stable. 相似文献
998.
Ruikson S.O. Nunes Waldemar D. Bastos João Manoel S. Pitot 《Mathematical Methods in the Applied Sciences》2020,43(3):1230-1242
In the present paper, we study energy decay and exact boundary controllability for a system of n one-dimensional linear wave equations coupled in parallel. The control obtained is a square integrable of the Neuman type for initial data with finite energy. The controllability time is near optimal value. We treat the case of control in the whole boundary and also in part of it. 相似文献
999.
K.G. Subramanian R. Saravanan M. Geethalakshmi P. Helen Chandra M. Margenstern 《自然科学进展》2007,17(4):479-485
Array P systems were introduced by Paun Gh. which is linking the two areas of membrane computing and picture grammars. Puzzle grammars were introduced by us for generating connected picture arrays in the two-dimensional plane, motivated by the problem of tiling the plane. On the other hand, incorporating into arrays the developmental type of generation used in the well-known biologically motivated L systems, Siromoney and Siromoney proposed a very general rectangular array generating model, called extended controlled tabled L array system (ECTLAS). In this paper we introduce two variations of the array P system, called BPG array P system and parallel array P system. The former has in the regions array objects and basic puzzle grammar rules (BPG), which are a specific kind of puzzle grammar rules. In the latter, the regions have rectangular array objects and tables of context-free rules. We examine these two types of P systems for their array generative power. 相似文献
1000.
Ludwig Gauckler 《计算数学(英文版)》2020,38(5):705-714
Trigonometric integrators for oscillatory linear Hamiltonian differential equations are
considered. Under a condition of Hairer & Lubich on the filter functions in the method,
a modified energy is derived that is exactly preserved by trigonometric integrators. This
implies and extends a known result on all-time near-conservation of energy. The extension
can be applied to linear wave equations. 相似文献