全文获取类型
收费全文 | 8700篇 |
免费 | 456篇 |
国内免费 | 403篇 |
专业分类
化学 | 1154篇 |
晶体学 | 51篇 |
力学 | 367篇 |
综合类 | 33篇 |
数学 | 5693篇 |
物理学 | 2261篇 |
出版年
2024年 | 12篇 |
2023年 | 77篇 |
2022年 | 119篇 |
2021年 | 146篇 |
2020年 | 194篇 |
2019年 | 221篇 |
2018年 | 193篇 |
2017年 | 150篇 |
2016年 | 158篇 |
2015年 | 177篇 |
2014年 | 333篇 |
2013年 | 838篇 |
2012年 | 387篇 |
2011年 | 466篇 |
2010年 | 385篇 |
2009年 | 589篇 |
2008年 | 615篇 |
2007年 | 595篇 |
2006年 | 454篇 |
2005年 | 311篇 |
2004年 | 276篇 |
2003年 | 298篇 |
2002年 | 289篇 |
2001年 | 244篇 |
2000年 | 261篇 |
1999年 | 232篇 |
1998年 | 218篇 |
1997年 | 144篇 |
1996年 | 124篇 |
1995年 | 99篇 |
1994年 | 114篇 |
1993年 | 65篇 |
1992年 | 82篇 |
1991年 | 60篇 |
1990年 | 56篇 |
1989年 | 53篇 |
1988年 | 39篇 |
1987年 | 62篇 |
1986年 | 35篇 |
1985年 | 80篇 |
1984年 | 43篇 |
1983年 | 32篇 |
1982年 | 41篇 |
1981年 | 21篇 |
1980年 | 30篇 |
1979年 | 26篇 |
1978年 | 20篇 |
1977年 | 29篇 |
1976年 | 21篇 |
1973年 | 13篇 |
排序方式: 共有9559条查询结果,搜索用时 0 毫秒
1.
Inner derivations and norm equality 总被引:3,自引:0,他引:3
Mohamed Barraa Mohamed Boumazgour 《Proceedings of the American Mathematical Society》2002,130(2):471-476
We characterize when the norm of the sum of two bounded operators on a Hilbert space is equal to the sum of their norms.
2.
The theory of tree-growing (RECPAM approach) is developed for outcome variables which are distributed as the canonical exponential family. The general RECPAM approach (consisting of three steps: recursive partition, pruning and amalgamation), is reviewed. This is seen as constructing a partition with maximal information content about a parameter to be predicted, followed by simplification by the elimination of ‘negligible’ information. The measure of information is defined for an exponential family outcome as a deviance difference, and appropriate modifications of pruning and amalgamation rules are discussed. It is further shown how the proposed approach makes it possible to develop tree-growing for situations usually treated by generalized linear models (GLIM). In particular, Poisson and logistic regression can be tree-structured. Moreover, censored survival data can be treated, as in GLIM, by observing a formal equivalence of the likelihood under random censoring and an appropriate Poisson model. Three examples are given of application to Poisson, binary and censored survival data. 相似文献
3.
G. Dattoli 《Journal of Mathematical Analysis and Applications》2002,269(2):716-725
Bilateral generating functions are those involving products of different types of polynomials. We show that operational methods offer a powerful tool to derive these families of generating functions. We study cases relevant to products of Hermite polynomials with Laguerre, Legendre and other polynomials. We also propose further extensions of the method which we develop here. 相似文献
4.
本文在一类 Lp位势V(x)下建立了广义Schrodinger算子H=(-Δ)m+V(x)在C∞0(Rn)上的本质自伴性,给出了H的本质谱的分布. 相似文献
5.
We consider Markov processes built from pasting together pieces of strong Markov processes which are killed at a position
dependent rate and connected via a transition kernel. We give necessary and sufficient conditions for local absolute continuity
of probability laws for such processes on a suitable path space and derive an explicit formula for the corresponding likelihood
ratio process. The main tool is the consideration of the process between successive jumps – what we call ‘elementary experiments’
– and criteria for absolute continuity of laws of the process there. We apply our results to systems of branching diffusions
with interactions and immigrations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
6.
本文考察了包括平面上的各种广义 Cantor集 ,Sierpinski集和包括某些连续不可微曲线在内的广义 Sierpinski集 .由相似变换 ,导出了它们的级数表达式 ,并利用它和字符串空间的对应关系 ,计算出它们的Hausdorff维数 相似文献
7.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls. 相似文献
8.
Thomas H. Pate 《Linear and Multilinear Algebra》2003,51(3):263-278
If 1≤k≤n, then Cor(n,k) denotes the set of all n×n real correlation matrices of rank not exceeding k. Grone and Pierce have shown that if A∈Cor (n, n-1), then per(A)≥n/(n-1). We show that if A∈Cor(n,2), then , and that this inequality is the best possible. 相似文献
9.
本文给出了Banach空间广义分解定理的一个初等证明,并利用它来证明两个对称不等式.这是首次在Banach空间获得这样的不等式. 相似文献
10.
Jose Manuel Corcuera Joao Guerra David Nualart Wim Schoutens 《Applied Mathematics and Optimization》2006,53(3):279-309
In this paper we consider the optimal investment problem in a market where the stock price process is modeled by a geometric
Levy process (taking into account jumps).
Except for the geometric Brownian model and the geometric Poissonian model, the
resulting models are incomplete and there are many equivalent martingale measures.
However, the model can be completed by the so-called power-jump assets. By doing this we allow investment in these new assets
and we can try to maximize the expected utility of these portfolios. As particular cases we obtain the optimal portfolios
based in stocks
and bonds, showing that the new assets are superfluous for certain martingale measures
that depend on the utility function we use. 相似文献