全文获取类型
收费全文 | 13933篇 |
免费 | 1631篇 |
国内免费 | 1189篇 |
专业分类
化学 | 3844篇 |
晶体学 | 69篇 |
力学 | 1067篇 |
综合类 | 275篇 |
数学 | 6364篇 |
物理学 | 5134篇 |
出版年
2023年 | 92篇 |
2022年 | 228篇 |
2021年 | 313篇 |
2020年 | 285篇 |
2019年 | 267篇 |
2018年 | 279篇 |
2017年 | 396篇 |
2016年 | 441篇 |
2015年 | 344篇 |
2014年 | 684篇 |
2013年 | 1000篇 |
2012年 | 685篇 |
2011年 | 815篇 |
2010年 | 715篇 |
2009年 | 820篇 |
2008年 | 975篇 |
2007年 | 954篇 |
2006年 | 799篇 |
2005年 | 781篇 |
2004年 | 645篇 |
2003年 | 608篇 |
2002年 | 583篇 |
2001年 | 439篇 |
2000年 | 435篇 |
1999年 | 409篇 |
1998年 | 404篇 |
1997年 | 325篇 |
1996年 | 273篇 |
1995年 | 220篇 |
1994年 | 223篇 |
1993年 | 135篇 |
1992年 | 153篇 |
1991年 | 114篇 |
1990年 | 92篇 |
1989年 | 100篇 |
1988年 | 78篇 |
1987年 | 75篇 |
1986年 | 59篇 |
1985年 | 83篇 |
1984年 | 57篇 |
1983年 | 41篇 |
1982年 | 64篇 |
1981年 | 31篇 |
1980年 | 28篇 |
1979年 | 43篇 |
1978年 | 42篇 |
1977年 | 25篇 |
1976年 | 24篇 |
1975年 | 12篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
A new series representation of the exact distribution of Hotelling's generalized T02 statistic is obtained. Unlike earlier work, the series representation given here is everywhere convergent. Explicit formulae are given for both the null and the non-central distributions. Earlier results by [1], 215–225), which are convergent on the interval [0, 1), are also derived quite simply from our formulae. The paper therefore provides a solution to the long standing problem of the exact distribution of the T02 statistic in the general case. 相似文献
992.
993.
本文研究在预报更新环境下具有快、慢两种配送方式和需求预报更新的库存系统,为了得到更多关于费用参数和预报改进对最优定货量以及最优的平均费用的影响,我们考虑两个周期的情形.以动态规划为工具我们得到了系统的最优策略.对于需求预报服从均匀分布情形,本文得到了最优定货量和最优的平均总费用的精确表达式.我们通过一些数值例子来说明库存费用、罚金、需求的预报改进和预报误差对最优定货量和最优的 相似文献
994.
Queueing theorists have presented, as solutions to many queueing models, probability generating functions in which state probabilities are expressed as functions of the roots of characteristic equations, evaluation of the roots in particular cases being left to the reader. Many users have complained that such solutions are inadequate. Some queueing theorists, in particular Neuts [6], rather than use Rouché's theorem to count roots and an equation-solver to find them, have developed new algorithms to solve queueing problems numerically, without explicit calculation of roots. Powell [7] has shown that in many bulk service queues arising in transportation models, characteristic equations can be solved and state probabilities can be found without serious difficulty, even when the number of roots to be found is large. We have slightly modified Powell's method, and have extended his work to cover a number of bulk-service queues discussed by Chaudhry et al. [1] and a number of bulk-arrival queues discussed in the present paper. 相似文献
995.
采用构造相容分布与非负上鞅的方法研究任意信源随机和相对熵密度的强极限定理,并由此得出若干任意信源,m阶马氏信源,无记忆信源的随机Shannon-Mcmillan定理.将已有的关于离散信源的结果加以推广. 相似文献
996.
Thomas Lorenz 《Set-Valued Analysis》2008,16(1):1-50
The mutational equations of Aubin extend ordinary differential equations to metric spaces (with compact balls). In first-order
geometric evolutions, however, the topological boundary need not be continuous in the sense of Painlevé–Kuratowski. So this
paper suggests a generalization of Aubin’s mutational equations that extends classical notions of dynamical systems and functional
analysis beyond the traditional border of vector spaces: Distribution-like solutions are introduced in a set just supplied
with a countable family of (possibly non-symmetric) distance functions. Moreover their existence is proved by means of Euler
approximations and a form of “weak” sequential compactness (although no continuous linear forms are available beyond topological
vector spaces). This general framework is applied to a first-order geometric example, i.e. compact subsets of ℝ
N
evolving according to the nonlocal properties of both the current set and its proximal normal cones. Here neither regularity
assumptions about the boundaries nor the inclusion principle are required. In particular, we specify sufficient conditions
for the uniqueness of these solutions.
相似文献
997.
In this paper we study normal forms for a class of germs of 1-resonant vector fields on R^n with mutually different eigenvalues which may admit extraneous resonance relations. We give an estimation on the index of finite determinacy from above as well as the essentially simplified polynomial normal forms for such vector fields. In the case that a vector field has a zero eigenvalue, the result leads to an interesting corollary, a linear dependence of the derivatives of the hyperbolic variables on the central variable. 相似文献
998.
本文证明了在正规locale范畴中,Banaschewski-Mulvey形式的紧正则反射与Johnstone形式的Wallman紧化一致,从而推广了Johnstone在文献[4]中的主要结果. 相似文献
999.
1000.
The Gauss–Markov theorem provides a golden standard for constructing the best linear unbiased estimation for linear models. The main purpose of this article is to extend the Gauss–Markov theorem to include nonparametric mixed-effects models. The extended Gauss–Markov estimation (or prediction) is shown to be equivalent to a regularization method and its minimaxity is addressed. The resulting Gauss–Markov estimation serves as an oracle to guide the exploration for effective nonlinear estimators adaptively. Various examples are discussed. Particularly, the wavelet nonparametric regression example and its connection with a Sobolev regularization is presented. 相似文献