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131.
We investigate whether seasonal-adjustment procedures are, at least approximately, linear data transformations. This question was initially addressed by Young and is important with respect to many issues including estimation of regression models with seasonally adjusted data. We focus on the X-11 program and rely on simulation evidence, involving linear unobserved component autoregressive integrated moving average models. We define a set of properties for the adequacy of a linear approximation to a seasonal-adjustment filter. These properties are examined through statistical tests. Next, we study the effect of X-11 seasonal adjustment on regression statistics assessing the statistical significance of the relationship between economic variables. Several empirical results involving economic data are also reported. 相似文献
132.
In this paper we provide a comprehensive Bayesian posterior analysis of trend determination in general autoregressive models. Multiple lag autoregressive models with fitted drifts and time trends as well as models that allow for certain types of structural change in the deterministic components are considered. We utilize a modified information matrix-based prior that accommodates stochastic nonstationarity, takes into account the interactions between long-run and short-run dynamics and controls the degree of stochastic nonstationarity permitted. We derive analytic posterior densities for all of the trend determining parameters via the Laplace approximation to multivariate integrals. We also address the sampling properties of our posteriors under alternative data generating processes by simulation methods. We apply our Bayesian techniques to the Nelson-Plosser macroeconomic data and various stock price and dividend data. Contrary to DeJong and Whiteman (1989a,b,c), we do not find that the data overwhelmingly favor the existence of deterministic trends over stochastic trends. In addition, we find evidence supporting Perron's (1989) view that some of the Nelson and Plosser data are best construed as trend stationary with a change in the trend function occurring at 1929. 相似文献
133.
Eric Chicken 《统计学通讯:理论与方法》2013,42(10):1915-1934
Nonparametric regression is considered where the sample point placement is not fixed and equispaced, but generated by a random process with rate n. Conditions are found for the random processes that result in optimal rates of convergence for nonparametric regression when using a block thresholded wavelet estimator. Previous results on nonparametric regression via wavelets on both fixed and random sample point placement are shown to be special cases of the general result given here. The estimator is adaptive over a large range of Hölder function spaces and the convergence rate exhibited is an improvement over term-by-term wavelet estimators. Threshold selection is implemented in a data-adaptive fashion, rather than using a fixed threshold as is usually done in block thresholding. This estimator, BlockSure, is compared against fixed-threshold block estimators and the more traditional term-by-term threshold wavelet estimators on several random design schemes via simulations. 相似文献
134.
Eric Chicken 《统计学通讯:模拟与计算》2013,42(8):1530-1542
A wavelet method is proposed that reduces function estimation error and provides smooth reconstructions, while still estimating jumps in the function well. It is based on analyzing multiple dilated versions of the sampled function. In simulation studies, the estimator exhibits low mean squared errors without sacrificing smoothness or jump detection ability when compared to other wavelet methods. 相似文献
135.
Eric Abella Roth Zishan Cui Ashleigh Rich Nathan Lachowsky Paul Sereda Kiffer George Card 《Journal of homosexuality》2018,65(4):524-539
British Columbia’s treatment as prevention policy has provided free access to highly active antiretroviral therapy (HAART) to all HIV-positive provincial residents since 1996. One outcome is an increase in HIV-positive gay and bisexual men (GBM) with suppressed viral loads. Previous cross-sectional analyses indicated that some Vancouver GBM now recognize condomless anal sex with men on HAART who report a suppressed viral load as a seroadaptive strategy. To test the hypothesis that this new strategy, termed viral load sorting (VLS), is recognized and used among by GBM in the Momentum Health Study, we analyzed longitudinal data for HIV-negative/unknown (n = 556) and HIV-positive (n = 218) serostatus participants. Analyses indicated that both groups reported VLS, and that serostatus and Treatment Optimism Scale scores were significant determinants in frequency and use. Results exemplify the medicalization of sex and Rogers’ Diffusion Of Preventative Innovations Model, and they have important implications for HIV research and GBM sexual decision-making. 相似文献
136.
Eric Dante Gutierrez 《Globalizations》2020,17(6):1008-1026
ABSTRACT The illicit drug crops opium and coca are conventionally regarded as sources of instability, an ‘evil’ that breeds fragility and violence. Fragile states are supposed to be most vulnerable to their production and consequent harms. Yet by looking into the local contexts of the world’s leading opium and coca producers – Afghanistan, Myanmar, Colombia and Bolivia – these illicit crops are found to also be sources of stability, even drivers of economic growth. They enable marginalized communities and territories abandoned by the state to be reinserted into national and global markets. Within so-called ‘fragile’ and conflict-affected areas are displaced and dispossessed households adopting innovative and unorthodox strategies for coping and survival in changing and insecure environments. This paper maps out an approach, useful for examining the resilience that has emerged amidst violence and uncertainty in illicit-crop-producing territories, and which can hopefully tackle the continuing disconnect between drugs and development policy. 相似文献
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