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211.
J. P. Grayson 《Journal of historical sociology》2018,31(4):512-525
Over the past few years a number of studies have focused on the disadvantages confronted by students who are the first in their families to attend university. Their liabilities include relatively low levels of preparedness, a lack of involvement in campus activities, and low levels of academic achievement. Rather than accepting the universality of this characterization, in this article, these negative characteristics and experiences were viewed as one ‘ideal type.’ Using this ideal type as a reference point, the current study focused on a period in Canadian history in which first generation students were the norm. In an examination of Glendon College, York University, located in Toronto Canada, in the mid 1960s, it was found that the experiences of the first generation did not fit the ideal type. Those who likely were the first in their families to attend university were prepared for their studies, involved in campus activities, and earned good grades. Possible explanations for this deviation from the ideal type include the buoyancy of the economy in the mid-sixties, an expanding university sector, the size and relative intimacy of the College, the way in which high schools prepared students for university, and stringent admission requirements. 相似文献
212.
Christopher R. Heathcote Borek D. Puza Steven P. Roberts 《Australian & New Zealand Journal of Statistics》2009,51(4):481-497
We consider two related aspects of the study of old‐age mortality. One is the estimation of a parameterized hazard function from grouped data, and the other is its possible deceleration at extreme old age owing to heterogeneity described by a mixture of distinct sub‐populations. The first is treated by half of a logistic transform, which is known to be free of discretization bias at older ages, and also preserves the increasing slope of the log hazard in the Gompertz case. It is assumed that data are available in the form published by official statistical agencies, that is, as aggregated frequencies in discrete time. Local polynomial modelling and weighted least squares are applied to cause‐of‐death mortality counts. The second, related, problem is to discover what conditions are necessary for population mortality to exhibit deceleration for a mixture of Gompertz sub‐populations. The general problem remains open but, in the case of three groups, we demonstrate that heterogeneity may be such that it is possible for a population to show decelerating mortality and then return to a Gompertz‐like increase at a later age. This implies that there are situations, depending on the extent of heterogeneity, in which there is at least one age interval in which the hazard function decreases before increasing again. 相似文献
213.
M. P. Wand 《Australian & New Zealand Journal of Statistics》2009,51(1):9-41
Semiparametric regression models that use spline basis functions with penalization have graphical model representations. This link is more powerful than previously established mixed model representations of semiparametric regression, as a larger class of models can be accommodated. Complications such as missingness and measurement error are more naturally handled within the graphical model architecture. Directed acyclic graphs, also known as Bayesian networks, play a prominent role. Graphical model-based Bayesian 'inference engines', such as bugs and vibes , facilitate fitting and inference. Underlying these are Markov chain Monte Carlo schemes and recent developments in variational approximation theory and methodology. 相似文献
214.
There has been increasing use of quality-of-life (QoL) instruments in drug development. Missing item values often occur in QoL data. A common approach to solve this problem is to impute the missing values before scoring. Several imputation procedures, such as imputing with the most correlated item and imputing with a row/column model or an item response model, have been proposed. We examine these procedures using data from two clinical trials, in which the original asthma quality-of-life questionnaire (AQLQ) and the miniAQLQ were used. We propose two modifications to existing procedures: truncating the imputed values to eliminate outliers and using the proportional odds model as the item response model for imputation. We also propose a novel imputation method based on a semi-parametric beta regression so that the imputed value is always in the correct range and illustrate how this approach can easily be implemented in commonly used statistical software. To compare these approaches, we deleted 5% of item values in the data according to three different missingness mechanisms, imputed them using these approaches and compared the imputed values with the true values. Our comparison showed that the row/column-model-based imputation with truncation generally performed better, whereas our new approach had better performance under a number scenarios. 相似文献
215.
Gabriel Escarela Luis Carlos Pérez-Ruíz Russell J. Bowater 《Journal of applied statistics》2009,36(6):647-657
A fully parametric first-order autoregressive (AR(1)) model is proposed to analyse binary longitudinal data. By using a discretized version of a copula, the modelling approach allows one to construct separate models for the marginal response and for the dependence between adjacent responses. In particular, the transition model that is focused on discretizes the Gaussian copula in such a way that the marginal is a Bernoulli distribution. A probit link is used to take into account concomitant information in the behaviour of the underlying marginal distribution. Fixed and time-varying covariates can be included in the model. The method is simple and is a natural extension of the AR(1) model for Gaussian series. Since the approach put forward is likelihood-based, it allows interpretations and inferences to be made that are not possible with semi-parametric approaches such as those based on generalized estimating equations. Data from a study designed to reduce the exposure of children to the sun are used to illustrate the methods. 相似文献
216.
Agustín Hernández Bastida José María Pérez Sánchez 《Journal of applied statistics》2009,36(8):853-869
The distribution of the aggregate claims in one year plays an important role in Actuarial Statistics for computing, for example, insurance premiums when both the number and size of the claims must be implemented into the model. When the number of claims follows a Poisson distribution the aggregated distribution is called the compound Poisson distribution. In this article we assume that the claim size follows an exponential distribution and later we make an extensive study of this model by assuming a bidimensional prior distribution for the parameters of the Poisson and exponential distribution with marginal gamma. This study carries us to obtain expressions for net premiums, marginal and posterior distributions in terms of some well-known special functions used in statistics. Later, a Bayesian robustness study of this model is made. Bayesian robustness on bidimensional models was deeply treated in the 1990s, producing numerous results, but few applications dealing with this problem can be found in the literature. 相似文献
217.
Classical nondecimated wavelet transforms are attractive for many applications. When the data comes from complex or irregular
designs, the use of second generation wavelets in nonparametric regression has proved superior to that of classical wavelets.
However, the construction of a nondecimated second generation wavelet transform is not obvious. In this paper we propose a
new ‘nondecimated’ lifting transform, based on the lifting algorithm which removes one coefficient at a time, and explore
its behavior. Our approach also allows for embedding adaptivity in the transform, i.e. wavelet functions can be constructed
such that their smoothness adjusts to the local properties of the signal. We address the problem of nonparametric regression
and propose an (averaged) estimator obtained by using our nondecimated lifting technique teamed with empirical Bayes shrinkage.
Simulations show that our proposed method has higher performance than competing techniques able to work on irregular data.
Our construction also opens avenues for generating a ‘best’ representation, which we shall explore. 相似文献
218.
The data collection process and the inherent population structure are the main causes for clustered data. The observations in a given cluster are correlated, and the magnitude of such correlation is often measured by the intra-cluster correlation coefficient. The intra-cluster correlation can lead to an inflated size of the standard F test in a linear model. In this paper, we propose a solution to this problem. Unlike previous adjustments, our method does not require estimation of the intra-class correlation, which is problematic especially when the number of clusters is small. Our simulation results show that the new method outperforms the existing methods. 相似文献
219.
Julian P. T. Higgins Simon G. Thompson David J. Spiegelhalter 《Journal of the Royal Statistical Society. Series A, (Statistics in Society)》2009,172(1):137-159
Summary. Meta-analysis in the presence of unexplained heterogeneity is frequently undertaken by using a random-effects model, in which the effects underlying different studies are assumed to be drawn from a normal distribution. Here we discuss the justification and interpretation of such models, by addressing in turn the aims of estimation, prediction and hypothesis testing. A particular issue that we consider is the distinction between inference on the mean of the random-effects distribution and inference on the whole distribution. We suggest that random-effects meta-analyses as currently conducted often fail to provide the key results, and we investigate the extent to which distribution-free, classical and Bayesian approaches can provide satisfactory methods. We conclude that the Bayesian approach has the advantage of naturally allowing for full uncertainty, especially for prediction. However, it is not without problems, including computational intensity and sensitivity to a priori judgements. We propose a simple prediction interval for classical meta-analysis and offer extensions to standard practice of Bayesian meta-analysis, making use of an example of studies of 'set shifting' ability in people with eating disorders. 相似文献
220.
Bringing together women and family in quality perspective bring about interesting discussions in this paper. By integrating
previous studies and considering expert opinions, we determinate the variables and dimensions with respect to women’s existence
regarding their roles both in the family and at work. Many activities carried out by women represent the consumer aspects
of their role. Women undertake these activities to fulfill their needs, which can be classified in the order of preference
using Maslow’s Hierarchy of Need. Women success can be measured based on their ability to perform their roles successfully.
We identify women’s performance by using quality approach of Personal Quality Maintenance (PQM), which is widely applied in
many organizations in order to maintain the service delivery, which meets the customer satisfaction. The effort to enhance
women’s satisfaction for their success in playing the multirole in the family and at work is our main consideration. This
study may contribute a new point of view regarding for the women’s welfare and existence. 相似文献