全文获取类型
收费全文 | 853篇 |
免费 | 20篇 |
国内免费 | 12篇 |
专业分类
化学 | 492篇 |
晶体学 | 3篇 |
力学 | 43篇 |
数学 | 163篇 |
物理学 | 184篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 14篇 |
2020年 | 20篇 |
2019年 | 22篇 |
2018年 | 23篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 31篇 |
2013年 | 45篇 |
2012年 | 33篇 |
2011年 | 52篇 |
2010年 | 35篇 |
2009年 | 37篇 |
2008年 | 50篇 |
2007年 | 39篇 |
2006年 | 41篇 |
2005年 | 29篇 |
2004年 | 38篇 |
2003年 | 15篇 |
2002年 | 22篇 |
2001年 | 18篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 16篇 |
1997年 | 7篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 8篇 |
1993年 | 8篇 |
1992年 | 5篇 |
1991年 | 17篇 |
1990年 | 19篇 |
1989年 | 16篇 |
1987年 | 7篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 8篇 |
1981年 | 4篇 |
1980年 | 6篇 |
1979年 | 4篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 9篇 |
1973年 | 3篇 |
1972年 | 5篇 |
1971年 | 3篇 |
1914年 | 2篇 |
排序方式: 共有885条查询结果,搜索用时 17 毫秒
61.
62.
The method known as the dominant pole algorithm (DPA) has previously been successfully used in combination with model order reduction techniques to approximate standard linear time-invariant dynamical systems and second order dynamical systems. In this paper, we show how this approach can be adapted to a class of second order delay systems, which are large scale nonlinear problems whose transfer functions have an infinite number of simple poles. Deflation is a very important ingredient for this type of methods. Because of the nonlinearity, many deflation approaches for linear systems are not applicable. We therefore propose an alternative technique that essentially removes computed poles from the system?s input and output vectors. In general, this technique changes the residues, and hence, modifies the order of dominance of the poles, but we prove that, under certain conditions, the residues stay near the original residues. The new algorithm is illustrated by numerical examples. 相似文献
63.
We introduce the notion of n-fold track extensions of a category C by a natural system D and prove that such extensions represent classes in the cohomology of C with coefficients in D introduced by Baues–Wirsching. This generalizes a result of Huebschmann on the cohomology of groups. 相似文献
64.
Elias Gabriel Minian 《K-Theory》2000,20(1):37-95
We develop an axiomatic homotopy theory for categories with a family of natural cylinders indexed by a set with relations, generalizing Baues I-categories. The main examples of -cofibration categories are the categories of global actions and simplicial complexes. 相似文献
65.
Elias Katsoulis David W. Kribs 《Transactions of the American Mathematical Society》2005,357(9):3739-3755
Based on a Wold decomposition for families of partial isometries and projections of Cuntz-Krieger-Toeplitz-type, we extend several fundamental theorems from the case of single vertex graphs to the general case of countable directed graphs with no sinks. We prove a Szego-type factorization theorem for CKT families, which leads to information on the structure of the unit ball in free semigroupoid algebras, and show that joint similarity implies joint unitary equivalence for such families. For each graph we prove a generalization of von Neumann's inequality which applies to row contractions of operators on Hilbert space which are related to the graph in a natural way. This yields a functional calculus determined by quiver algebras and free semigroupoid algebras. We establish a generalization of Coburn's theorem for the -algebra of a CKT family, and prove a universality theorem for -algebras generated by these families. In both cases, the -algebras generated by quiver algebras play the universal role.
66.
We consider a productive asset, called equipment or capital good, and we examine the properties of, as well as the interactions between, the operating policies, which are determined by its optimal utilization and maintenance, and the capital policy of scrapping, which defines the optimal time when the productive asset is retired from its current use. Starting with an abstract model and using the approach of optimal control, initially we characterize the various types of equipment by assigning to them a single total profit index, which indicates how the above policies affect the flow of operating revenues plus capital gains or losses. This index is a function of market-determined prices. So using it we then investigate how the operating and capital policies are influenced by the rate of discount, the price of new equipment, and the rise or fall of the price of new equipment relative to the value of its output. Among other interesting results, we find that the effects of these prices on the nature and interactions of optimal policies depend crucially on whether the equipment is of the usual profit making type, where output is the main source of revenue, or of the antique type, where the main source of revenue is capital gains. 相似文献
67.
On Word Equations Originated from Discrete Dynamical Systems Related to Antisymmetric Cubic Maps with Some Applications 下载免费PDF全文
Elias Abboud 《数学学报(英文版)》2018,34(11):1663-1676
In this article, we solve some word equations originated from discrete dynamical systems related to antisymmetric cubic map. These equations emerge when we work with primitive and greatest words. In particular, we characterize all the cases for which <β1β1>=<β2β2> where β1 and β2 are the greatest words in <<β1>> and <<β2>> of M(n). 相似文献
68.
Elias Salomão Helou Sandra A. Santos Lucas E. A. Simões 《Journal of Optimization Theory and Applications》2017,175(1):137-157
The gradient sampling method is a recently developed tool for solving unconstrained nonsmooth optimization problems. Using just first-order information about the objective function, it generalizes the steepest descent method, one of the most classical methods for minimizing a smooth function. This study aims at determining under which circumstances one can expect the same local convergence result of the Cauchy method for the gradient sampling algorithm under the assumption that the problem is stated by a finite max-function around the optimal point. Additionally, at the end, we show how to practically accomplish the required hypotheses during the execution of the algorithm. 相似文献
69.
70.