全文获取类型
收费全文 | 1071篇 |
免费 | 79篇 |
国内免费 | 81篇 |
专业分类
化学 | 27篇 |
力学 | 18篇 |
综合类 | 22篇 |
数学 | 1075篇 |
物理学 | 89篇 |
出版年
2023年 | 6篇 |
2022年 | 12篇 |
2021年 | 22篇 |
2020年 | 17篇 |
2019年 | 15篇 |
2018年 | 19篇 |
2017年 | 30篇 |
2016年 | 38篇 |
2015年 | 18篇 |
2014年 | 43篇 |
2013年 | 105篇 |
2012年 | 45篇 |
2011年 | 53篇 |
2010年 | 55篇 |
2009年 | 88篇 |
2008年 | 58篇 |
2007年 | 56篇 |
2006年 | 47篇 |
2005年 | 53篇 |
2004年 | 32篇 |
2003年 | 28篇 |
2002年 | 39篇 |
2001年 | 27篇 |
2000年 | 33篇 |
1999年 | 19篇 |
1998年 | 24篇 |
1997年 | 22篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 27篇 |
1993年 | 17篇 |
1992年 | 13篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 12篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 10篇 |
1983年 | 3篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1978年 | 10篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有1231条查询结果,搜索用时 15 毫秒
41.
Representation theorem and local asymptotic minimax theorem are derived for nonparametric estimators of the distribution function on the basis of randomly truncated data. The convolution-type representation theorem asserts that the limiting process of any regular estimator of the distribution function is at least as dispersed as the limiting process of the product-limit estimator. The theorems are similar to those results for the complete data case due to Beran (1977, Ann. Statist., 5, 400–404) and for the censored data case due to Wellner (1982, Ann. Statist., 10, 595–602). Both likelihood and functional approaches are considered and the proofs rely on the method of Begun et al. (1983, Ann. Statist., 11, 432–452) with slight modifications.Division of Biostatistics, School of Public Health, Columbia Univ. 相似文献
42.
To analyze the isotonic regression problem for normal means, it is usual to assume that all variances are known or unknown but equal. This paper then studies this problem in the case that there are no conditions imposed on the variances. Suppose that we have data drawn fromkindependent normal populations with unknown meansμi's and unknown variancesσ2i's, in which the means are restricted by a given partial ordering. This paper discusses some properties of the maximum likelihood estimates ofμi's andσ2i's under the restriction and proposes an algorithm for obtaining the estimates. 相似文献
43.
44.
The criterion robustness of the standard likelihood ratio test (LRT) under the multivariate normal regression model and also the inference robustness of the same test under the univariate set up are established for certain nonnormal distributions of errors. Restricting attention to the normal distribution of errors in the context of univariate regression models, conditions on the design matrix are established under which the usual LRT of a linear hypothesis (under homoscedasticity of errors) remains valid if the errors have an intraclass covariance structure. The conditions hold in the case of some standard designs. The relevance of C. R. Rao's (1967 In Proceedings Fifth Berkeley Symposium on Math. Stat. and Prob., Vol. 1, pp. 355–372) and G. Zyskind's (1967, Ann. Math. Statist.38 1092–1110) conditions in this context is discussed. 相似文献
45.
This paper concerns the cubic smoothing spline approach to nonparametric regression. After first deriving sharp asymptotic formulas for the eigenvalues of the smoothing matrix, the paper uses these formulas to investigate the efficiency of different selection criteria for choosing the smoothing parameter. Special attention is paid to the generalized maximum likelihood (GML), C
p
and extended exponential (EE) criteria and their marginal Bayesian interpretation. It is shown that (a) when the Bayesian model that motivates GML is true, using C
p
to estimate the smoothing parameter would result in a loss of efficiency with a factor of 10/3, proving and strengthening a conjecture proposed in Stein (1990); (b) when the data indeed come from the C
p
density, using GML would result in a loss of efficiency of ; (c) the loss of efficiency of the EE criterion is at most 1.543 when the data are sampled from its consistent density family. The paper not only studies equally spaced observations (the setting of Stein, 1990), but also investigates general sampling scheme of the design points, and shows that the efficiency results remain the same in both cases.This work is supported in part by NSF grant DMS-0204674 and Harvard University Clark-Cooke Fund.
Mathematics Subject Classification (2000):Primary: 62G08; Secondary: 62G20 相似文献
46.
P. Kabaila 《Acta Appl Math》2003,78(1-3):185-192
We consider the problem of constructing a 1– upper confidence limit for the scalar parameter 0 in the presence of the nuisance parameter vector 0, when the data are discrete. The 'profile plug-in' upper confidence limit is introduced by Kabaila and Lloyd. This confidence limit is based on computing a P-value
from an estimator
of 0, replacing the nuisance parameter by the profile maximum likelihood estimate
for known, and equating to . Theoretical and numerical evidence for the good coverage properties of this confidence limit is presented by Kabaila and Lloyd. An upper confidence limit should be assessed not only by its coverage properties but also by how large this confidence limit is. We measure how large the profile plug-in upper limit is by using a large sample approximation to it. This large sample approximation is used to delineate further the good properties of this confidence limit. 相似文献
47.
Liu Huimei 《Annals of the Institute of Statistical Mathematics》2000,52(1):15-27
Let Xhave a multivariate, p-dimensional normal distribution (p 2) with unknown mean and known, nonsingular covariance . Consider testing H
0 : b
i 0, for some i = 1,..., k, and b
i 0, for some i = 1,..., k, versus H
1 : b
i < 0, for all i = 1,..., k, or b
i
< 0, for all i = 1,..., k, where b
1,..., b
k
, k 2, are known vectors that define the hypotheses and suppose that for each i = 1,..., k there is an j {1,..., k} (j will depend on i) such that b
i b
j 0. For any 0 < < 1/2. We construct a test that has the same size as the likelihood ratio test (LRT) and is uniformly more powerful than the LRT. The proposed test is an intersection-union test. We apply the result to compare linear regression functions. 相似文献
48.
FINE Jason P 《中国科学 数学(英文版)》2012,55(8):1583-1595
We consider the estimation of three-dimensional ROC surfaces for continuous tests given covariates.Three way ROC analysis is important in our motivating example where patients with Alzheimer’s disease are usually classified into three categories and should receive different category-specific medical treatment.There has been no discussion on how covariates affect the three way ROC analysis.We propose a regression framework induced from the relationship between test results and covariates.We consider several practical cases and the corresponding inference procedures.Simulations are conducted to validate our methodology.The application on the motivating example illustrates clearly the age and sex effects on the accuracy for Mini-Mental State Examination of Alzheimer’s disease. 相似文献
49.
In this article we deal with the problem of stability of the conclusions from principal components analysis over repeated
samples. We define a measure of stability for each component and investigate some of the measures properties. We then obtain
the maximum likelihood estimators (MLEs) of the measures, and derive their joint limiting distributions. The MLEs of the measures
turn out to be asymptotically unbiased and jointly have the multivariate normal distribution. Modified estimators are also
found to reduce the amount of bias in the MLEs. To facilitate interpretation of the measures we define stability confidence
level as coverage probability, and associate with each measure a stability confidence level to describe the measure in terms
of probability. Finally, we investigate the stability of the components via a simulation study and compare the performance
of the MLEs and the modified estimators in terms of bias and precision.
This work was sponsored by a grant from the Office of Vice-President for Research at Kuwait University under project number
SS049. 相似文献
50.
A LAW OF ITERATED LOGARITHM FOR THE MLE IN A RANDOM CENSORING MODEL WITH INCOMPLETE INFORMATION 总被引:1,自引:0,他引:1
In this article, a law of iterated logarithm for the maximum likelihood estimator in a random censoring model with incomplete information under certain regular conditions is obtained. 相似文献