全文获取类型
收费全文 | 8461篇 |
免费 | 212篇 |
国内免费 | 1篇 |
专业分类
管理学 | 1140篇 |
民族学 | 53篇 |
人口学 | 747篇 |
丛书文集 | 26篇 |
理论方法论 | 737篇 |
综合类 | 87篇 |
社会学 | 3813篇 |
统计学 | 2071篇 |
出版年
2023年 | 48篇 |
2021年 | 54篇 |
2020年 | 124篇 |
2019年 | 201篇 |
2018年 | 213篇 |
2017年 | 317篇 |
2016年 | 232篇 |
2015年 | 144篇 |
2014年 | 219篇 |
2013年 | 1607篇 |
2012年 | 255篇 |
2011年 | 268篇 |
2010年 | 206篇 |
2009年 | 212篇 |
2008年 | 223篇 |
2007年 | 206篇 |
2006年 | 224篇 |
2005年 | 207篇 |
2004年 | 182篇 |
2003年 | 169篇 |
2002年 | 192篇 |
2001年 | 212篇 |
2000年 | 217篇 |
1999年 | 206篇 |
1998年 | 145篇 |
1997年 | 136篇 |
1996年 | 114篇 |
1995年 | 105篇 |
1994年 | 148篇 |
1993年 | 117篇 |
1992年 | 139篇 |
1991年 | 140篇 |
1990年 | 123篇 |
1989年 | 109篇 |
1988年 | 96篇 |
1987年 | 97篇 |
1986年 | 94篇 |
1985年 | 94篇 |
1984年 | 99篇 |
1983年 | 75篇 |
1982年 | 79篇 |
1981年 | 57篇 |
1980年 | 64篇 |
1979年 | 65篇 |
1978年 | 51篇 |
1977年 | 53篇 |
1976年 | 42篇 |
1975年 | 47篇 |
1974年 | 41篇 |
1971年 | 25篇 |
排序方式: 共有8674条查询结果,搜索用时 864 毫秒
401.
402.
The use of covariates in block designs is necessary when the covariates cannot be controlled like the blocking factor in the experiment. In this paper, we consider the situation where there is some flexibility for selection in the values of the covariates. The choice of values of the covariates for a given block design attaining minimum variance for estimation of each of the parameters has attracted attention in recent times. Optimum covariate designs in simple set-ups such as completely randomised design (CRD), randomised block design (RBD) and some series of balanced incomplete block design (BIBD) have already been considered. In this paper, optimum covariate designs have been considered for the more complex set-ups of different partially balanced incomplete block (PBIB) designs, which are popular among practitioners. The optimum covariate designs depend much on the methods of construction of the basic PBIB designs. Different combinatorial arrangements and tools such as orthogonal arrays, Hadamard matrices and different kinds of products of matrices viz. Khatri–Rao product, Kronecker product have been conveniently used to construct optimum covariate designs with as many covariates as possible. 相似文献
403.
In quantitative trait linkage studies using experimental crosses, the conventional normal location-shift model or other parameterizations may be unnecessarily restrictive. We generalize the mapping problem to a genuine nonparametric setup and provide a robust estimation procedure for the situation where the underlying phenotype distributions are completely unspecified. Classical Wilcoxon–Mann–Whitney statistics are employed for point and interval estimation of QTL positions and effects. 相似文献
404.
A supersaturated design is a design whose run size is not enough for estimating all the main effects. It is commonly used in screening experiments, where the goals are to identify sparse and dominant active factors with low cost. In this paper, we study a variable selection method via the Dantzig selector, proposed by Candes and Tao [2007. The Dantzig selector: statistical estimation when p is much larger than n. Annals of Statistics 35, 2313–2351], to screen important effects. A graphical procedure and an automated procedure are suggested to accompany with the method. Simulation shows that this method performs well compared to existing methods in the literature and is more efficient at estimating the model size. 相似文献
405.
Aristidis K. Nikoloulopoulos Dimitris Karlis 《Journal of statistical planning and inference》2009,139(11):203
A new family of copulas is introduced that provides flexible dependence structure while being tractable and simple to use for multivariate discrete data modeling. The construction exploits finite mixtures of uncorrelated normal distributions. Accordingly, the cumulative distribution function is simply the product of univariate normal distributions. At the same time, however, the mixing operation introduces association. The properties of the new family of copulas are examined and a concrete application is used to show its applicability. 相似文献
406.
Most studies of quality improvement deal with ordered categorical data from industrial experiments. Accounting for the ordering of such data plays an important role in effectively determining the optimal factor level of combination. This paper utilizes the correspondence analysis to develop a procedure to improve the ordered categorical response in a multifactor state system based on Taguchi's statistic. Users may find the proposed procedure in this paper to be attractive because we suggest a simple and also popular statistical tool for graphically identifying the really important factors and determining the levels to improve process quality. A case study for optimizing the polysilicon deposition process in a very large-scale integrated circuit is provided to demonstrate the effectiveness of the proposed procedure. 相似文献
407.
Several models for studies related to tensile strength of materials are proposed in the literature where the size or length
component has been taken to be an important factor for studying the specimens’ failure behaviour. An important model, developed
on the basis of cumulative damage approach, is the three-parameter extension of the Birnbaum–Saunders fatigue model that incorporates
size of the specimen as an additional variable. This model is a strong competitor of the commonly used Weibull model and stands
better than the traditional models, which do not incorporate the size effect. The paper considers two such cumulative damage
models, checks their compatibility with a real dataset, compares them with some of the recent toolkits, and finally recommends
a model, which appears an appropriate one. Throughout the study is Bayesian based on Markov chain Monte Carlo simulation. 相似文献
408.
The present study deals with the method of estimation of the parameters of k-components load-sharing parallel system model
in which each component’s failure time distribution is assumed to be geometric. The maximum likelihood estimates of the load-share
parameters with their standard errors are obtained. (1 − γ) 100% joint, Bonferroni simultaneous and two bootstrap confidence intervals for the parameters have been constructed. Further,
recognizing the fact that life testing experiments are time consuming, it seems realistic to consider the load-share parameters
to be random variable. Therefore, Bayes estimates along with their standard errors of the parameters are obtained by assuming
Jeffrey’s invariant and gamma priors for the unknown parameters. Since, Bayes estimators can not be found in closed form expressions,
Tierney and Kadane’s approximation method have been used to compute Bayes estimates and standard errors of the parameters.
Markov Chain Monte Carlo technique such as Gibbs sampler is also used to obtain Bayes estimates and highest posterior density
credible intervals of the load-share parameters. Metropolis–Hastings algorithm is used to generate samples from the posterior
distributions of the unknown parameters. 相似文献
409.
Sunil K. Mathur 《Statistical Methods and Applications》2009,18(3):375-388
A strictly nonparametric bivariate test for two sample location problem is proposed. The proposed test is easy to apply and
does not require the stringent condition of affine-symmetry or elliptical symmetry which is required by some of the major
tests available for the same problem. The power function of the proposed test is calculated. The asymptotic distribution of
the proposed test statistic is found to be normal. The power of proposed test is compared with some of the well-known tests
under various distributions using Monte Carlo simulation technique. The power study shows that the proposed test statistic
performs better than most of the test statistics for almost all the distributions considered here. As soon as the underlying
population structure deviates from normality, the ability of the proposed test statistic to detect the smallest shift in location
increases as compared to its competitors. The application of the test is shown by using a data set. 相似文献
410.
Obesity is considered a major cause of premature mortality and a potential threat to the longstanding secular decline in mortality
in the United States. We measure relative and attributable risks associated with obesity among middle-aged adults using data
from the Health and Retirement Study (1992–2004). Although class II/III obesity (BMI _ 35.0 kg/m2) increases mortality by
40% in females and 62% in males compared with normal BMI (BMI = 18.5-24.9), class I obesity (BMI = 30.0-34.9) and being overweight
(BMI = 25.0-29.9) are not associated with excess mortality. With respect to attributable mortality, class II/III obesity (BMI
_ 35.0) is responsible for approximately 4% of deaths among females and 3% of deaths among males. Obesity is often compared
with cigarette smoking as a major source of avoidable mortality. Smoking-attributable mortality is much larger in this cohort:
about 36% in females and 50% in males. Results are robust to confounding by preexisting diseases, multiple dimensions of socioeconomic
status (SES), smoking, and other correlates. These findings challenge the viewpoint that obesity will stem the long-term secular
decline in U.S. mortality. 相似文献