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91.
Samuel S. Wu 《统计学通讯:理论与方法》2013,42(8):1483-1494
In this article, three methods of combining dependent univariate tests are studied. The Bahadur approximate efficiencies are derived under the asymptotic normal assumption. These procedures are applied to the multivariate location problem and compared with two Hotelling-type tests. A Monte Carlo study indicates that in certain cases the powers of the combination methods are much better than Hotelling's T 2 and other multivariate nonparametric tests. 相似文献
92.
93.
Cheng Ju Mary Combs Samuel D. Lendle Jessica M. Franklin Richard Wyss Sebastian Schneeweiss 《Journal of applied statistics》2019,46(12):2216-2236
ABSTRACTThe optimal learner for prediction modeling varies depending on the underlying data-generating distribution. Super Learner (SL) is a generic ensemble learning algorithm that uses cross-validation to select among a ‘library’ of candidate prediction models. While SL has been widely studied in a number of settings, it has not been thoroughly evaluated in large electronic healthcare databases that are common in pharmacoepidemiology and comparative effectiveness research. In this study, we applied and evaluated the performance of SL in its ability to predict the propensity score (PS), the conditional probability of treatment assignment given baseline covariates, using three electronic healthcare databases. We considered a library of algorithms that consisted of both nonparametric and parametric models. We also proposed a novel strategy for prediction modeling that combines SL with the high-dimensional propensity score (hdPS) variable selection algorithm. Predictive performance was assessed using three metrics: the negative log-likelihood, area under the curve (AUC), and time complexity. Results showed that the best individual algorithm, in terms of predictive performance, varied across datasets. The SL was able to adapt to the given dataset and optimize predictive performance relative to any individual learner. Combining the SL with the hdPS was the most consistent prediction method and may be promising for PS estimation and prediction modeling in electronic healthcare databases. 相似文献
94.
Jonathan Eaton Samuel Kortum 《Econometrica : journal of the Econometric Society》2002,70(5):1741-1779
We develop a Ricardian trade model that incorporates realistic geographic features into general equilibrium. It delivers simple structural equations for bilateral trade with parameters relating to absolute advantage, to comparative advantage (promoting trade), and to geographic barriers (resisting it). We estimate the parameters with data on bilateral trade in manufactures, prices, and geography from 19 OECD countries in 1990. We use the model to explore various issues such as the gains from trade, the role of trade in spreading the benefits of new technology, and the effects of tariff reduction. 相似文献
95.
They do a great job. So we promote them. Now they supervise people who don't do the job as well as they did. We give them a big raise. But because they're exempt they make less than their leads. They have the toughest job in the company—managing people. So we grant them an entire day of training to prepare. We ask them to mentor, coach, and have close relationships with their direct reports—all 132 of them. Then when the stock dips, we blame “middle management” and lay a bunch of them off. 相似文献
96.
Despite the burgeoning literature on stakeholder green pressure, research is scarce on how it influences eco-product innovation and new product performance. This article examines stakeholder green pressures as antecedents of eco-product innovation and new product performance in firms operating in resource-constrained countries. Using data gathered from surveys in Vietnam (N = 183) and Ghana (N = 217), we find that the positive effects of stakeholder green pressures on new product performance are serially mediated by environmental sustainability orientation and eco-product innovation. Our findings contribute to ongoing efforts to clarify the mechanisms channelling stakeholder pressures into new product performance in resource-constrained environments. 相似文献
97.
While the need for and lack of implementation of more sophisticated methods for measuring the impact of public relations efforts has been well documented in the U.S. and some other world regions, relatively little information exist about this practice in the European Union. Results from a survey of both consumers and providers of public relations in the EU shows that perceptions of effectiveness and actual use are not related for most advanced techniques of measurement and evaluation. These results demonstrate some potentially important differences between the perceptions of providers and consumers that may support practitioner observations regarding a lack of interest among clients in more accurate assessment of results from public relations activities. 相似文献
98.
Chong You John T. Ormerod Samuel Müller 《Australian & New Zealand Journal of Statistics》2014,56(1):73-87
Variational Bayes (VB) estimation is a fast alternative to Markov Chain Monte Carlo for performing approximate Baesian inference. This procedure can be an efficient and effective means of analyzing large datasets. However, VB estimation is often criticised, typically on empirical grounds, for being unable to produce valid statistical inferences. In this article we refute this criticism for one of the simplest models where Bayesian inference is not analytically tractable, that is, the Bayesian linear model (for a particular choice of priors). We prove that under mild regularity conditions, VB based estimators enjoy some desirable frequentist properties such as consistency and can be used to obtain asymptotically valid standard errors. In addition to these results we introduce two VB information criteria: the variational Akaike information criterion and the variational Bayesian information criterion. We show that variational Akaike information criterion is asymptotically equivalent to the frequentist Akaike information criterion and that the variational Bayesian information criterion is first order equivalent to the Bayesian information criterion in linear regression. These results motivate the potential use of the variational information criteria for more complex models. We support our theoretical results with numerical examples. 相似文献
99.
□ A doubly nonstationary cylinder-based model is built to describe the dispersal of a population from a point source. In this model, each cylinder represents a fraction of the population, i.e., a group. Two contexts are considered: The dispersal can occur in a uniform habitat or in a fragmented habitat described by a conditional Boolean model. After the construction of the models, we investigate their properties: the first and second order moments, the probability that the population vanishes, and the distribution of the spatial extent of the population. 相似文献
100.
We provide the first global assessment of the sources of population aging by tracing its origins to the demographic histories of more and less developed countries. In more developed countries, improvements in survival among successive cohorts have accounted for the large majority of the recent increase in the population's mean age. Improved survivorship and declines in the growth rate of births have made roughly equal contributions to the aging that is occurring in less developed countries. Aging is more rapid in less developed countries because the number of births has declined faster, with China and India making large contributions. Use of the proportion of the population above age 65, 70, or 75 as measures of aging produces results similar to those using the mean age. Mortality decline becomes an even larger contributor to aging using all these measures, and its contribution grows as age advances. 相似文献