全文获取类型
收费全文 | 1825篇 |
免费 | 206篇 |
国内免费 | 82篇 |
专业分类
化学 | 74篇 |
晶体学 | 1篇 |
力学 | 422篇 |
综合类 | 16篇 |
数学 | 901篇 |
物理学 | 296篇 |
无线电 | 403篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 24篇 |
2021年 | 34篇 |
2020年 | 56篇 |
2019年 | 35篇 |
2018年 | 37篇 |
2017年 | 69篇 |
2016年 | 78篇 |
2015年 | 65篇 |
2014年 | 84篇 |
2013年 | 148篇 |
2012年 | 112篇 |
2011年 | 108篇 |
2010年 | 96篇 |
2009年 | 93篇 |
2008年 | 114篇 |
2007年 | 110篇 |
2006年 | 111篇 |
2005年 | 105篇 |
2004年 | 80篇 |
2003年 | 68篇 |
2002年 | 57篇 |
2001年 | 41篇 |
2000年 | 34篇 |
1999年 | 33篇 |
1998年 | 34篇 |
1997年 | 43篇 |
1996年 | 34篇 |
1995年 | 23篇 |
1994年 | 14篇 |
1993年 | 22篇 |
1992年 | 25篇 |
1991年 | 18篇 |
1990年 | 17篇 |
1989年 | 9篇 |
1988年 | 8篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 12篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1975年 | 4篇 |
1973年 | 3篇 |
1957年 | 1篇 |
排序方式: 共有2113条查询结果,搜索用时 296 毫秒
901.
902.
Akio Suzukawa Hideyuki Imai Yoshiharu Sato 《Annals of the Institute of Statistical Mathematics》2001,53(2):262-276
This paper is intended as an investigation of parametric estimation for the randomly right censored data. In parametric estimation, the Kullback-Leibler information is used as a measure of the divergence of a true distribution generating a data relative to a distribution in an assumed parametric model M. When the data is uncensored, maximum likelihood estimator (MLE) is a consistent estimator of minimizing the Kullback-Leibler information, even if the assumed model M does not contain the true distribution. We call this property minimum Kullback-Leibler information consistency (MKLI-consistency). However, the MLE obtained by maximizing the likelihood function based on the censored data is not MKLI-consistent. As an alternative to the MLE, Oakes (1986, Biometrics, 42, 177–182) proposed an estimator termed approximate maximum likelihood estimator (AMLE) due to its computational advantage and potential for robustness. We show MKLI-consistency and asymptotic normality of the AMLE under the misspecification of the parametric model. In a simulation study, we investigate mean square errors of these two estimators and an estimator which is obtained by treating a jackknife corrected Kaplan-Meier integral as the log-likelihood. On the basis of the simulation results and the asymptotic results, we discuss comparison among these estimators. We also derive information criteria for the MLE and the AMLE under censorship, and which can be used not only for selecting models but also for selecting estimation procedures. 相似文献
903.
M. Carletti 《Numerical Algorithms》2001,28(1-4):27-44
In this paper we describe an algorithm to determine the instability region of the endemic equilibrium of a delay model for phage–bacteria interaction in open marine environment. The algorithm relies on a new geometric criterion for stability switches introduced by Beretta and Kuang for delay models for which the corresponding characteristic equations have delay-dependent coefficients [6]. The outputs of the algorithm presented in this paper, which can be equivalently applied to similar 2D delay models, show that for this kind of models large delays are usually stabilizing. 相似文献
904.
905.
Bellman and Zadeh have originated three systems of multistage decision processes in a fuzzy environment: deterministic, stochastic and fuzzy systems. In this article, we consider an optimization problem with an optimistic criterion on a fuzzy system. By making use of minimization–maximization expectation in a fuzzy environment, we derive a recursive equation for the fuzzy decision process through invariant imbedding approach. By illustrating a three-state, two-decision and two-stage model, we give an optimal solution through dynamic programming. The optimal solution is also verified by the method of multistage fuzzy decision tree-table. 相似文献
906.
1. IntroductionLet X and Y be p x 1 and q x 1 random vectors, respectively, and let p 5 q. PutCanonica1 correlation analysis focuses on the relationship between the two sets of randomvariables, X.. 1 and Yax 1' We ca1l EFllZl,Zdz Z2l the canonical correlation matrix (CCM).Let pf,',p; (l > Pf 2.' 2 p; 2 0) be the eigenvalues of CCM. Their positive squareroots pl )', pp are the population canonical correlation coefficients. Letbe the sample covaxiance matrix, where U'1,' 5 Wi. ar… 相似文献
907.
A new static failure criterion for isotropic polymers with different strengths in tension and compression based on exponential dependence between the mean stress and the von Mises equivalent stress is proposed. The two material parameters introduced can be determined by two simple tests - the uniaxial tension and compression. The locus of the criterion is nearly conical for low hydrostatic pressures and tends to a cylindrical form if an increased hydrostatic pressure is applied. The validity of the criterion is demonstrated by experimental strength data taken from the literature for several polymers in the case of superimposed hydrostatic pressure. 相似文献
908.
We present information criteria for statistical model evaluation problems for stochastic processes. The emphasis is put on the use of the asymptotic expansion of the distribution of an estimator based on the conditional Kullback–Leibler divergence for stochastic processes. Asymptotic properties of information criteria and their improvement are discussed. An application to a diffusion process is presented. 相似文献
909.
910.
Peter Braunsteins Geoffrey Decrouez Sophie Hautphenne 《Stochastic Processes and their Applications》2019,129(3):713-739
We consider the extinction events of Galton–Watson processes with countably infinitely many types. In particular, we construct truncated and augmented Galton–Watson processes with finite but increasing sets of types. A pathwise approach is then used to show that, under some sufficient conditions, the corresponding sequence of extinction probability vectors converges to the global extinction probability vector of the Galton–Watson process with countably infinitely many types. Besides giving rise to a family of new iterative methods for computing the global extinction probability vector, our approach paves the way to new global extinction criteria for branching processes with countably infinitely many types. 相似文献