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1.
文章提出具有卖空总量限制、阈值约束和V型交易成本的多阶段均值—半绝对偏差(M-SAD)投资组合优化模型。该模型分别运用均值和半绝对偏衡量资产的收益率和风险。由于交易成本的存在,该模型不满足无后效性的动态优化问题。文章将该模型近似为一般动态规划问题,提出一种新的离散迭代方法,并证明该算法是线性收敛的。最后,文章通过实证研究比较分析卖空总量限制和风险偏好系数取不同值时对投资组合最优策略的影响,验证模型和算法的有效性。 相似文献
2.
随着信息技术的发展,数字经济已经成为经济增长的"新引擎"。但由于缺乏权威的产业统计分类标准,学者们一直面临"数字经济研究缺乏数字依据"的尴尬境地。文章基于国家统计局公布并实施的《数字经济及其核心产业统计分类(2021)》中的分类标准,对各省份统计年鉴的数据进行重新整理,利用熵权法构建数字经济发展指数,测度了我国30个省份的数字经济发展水平,分析了各省份数字经济发展的差异以及时空特征。研究发现,2009—2019年我国数字经济产业发展迅猛,各项子产业都取得了长足的进步。相比较而言,数字要素驱动业发展速度略低于其他三个子产业;数字经济发展存在着明显的区域不平衡。东中部地区的数字经济发展状况明显优于西部地区,南方优于北方,而且区域不平衡有持续扩大趋势。 相似文献
3.
Cathy W. S. Chen Hong Than-Thi Mike K. P. So 《Journal of Statistical Computation and Simulation》2019,89(2):191-210
This paper proposes a new hysteretic vector autoregressive (HVAR) model in which the regime switching may be delayed when the hysteresis variable lies in a hysteresis zone. We integrate an adapted multivariate Student-t distribution from amending the scale mixtures of normal distributions. This HVAR model allows for a higher degree of flexibility in the degrees of freedom for each time series. We use the proposed model to test for a causal relationship between any two target time series. Using posterior odds ratios, we overcome the limitations of the classical approach to multiple testing. Both simulated and real examples herein help illustrate the suggested methods. We apply the proposed HVAR model to investigate the causal relationship between the quarterly growth rates of gross domestic product of United Kingdom and United States. Moreover, we check the pairwise lagged dependence of daily PM2.5 levels in three districts of Taipei. 相似文献
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Jorge Quiroz Richard Montes Heliang Shi Satrajit Roychoudhury 《Pharmaceutical statistics》2019,18(3):316-328
Assessment of analytical similarity of tier 1 quality attributes is based on a set of hypotheses that tests the mean difference of reference and test products against a margin adjusted for standard deviation of the reference product. Thus, proper assessment of the biosimilarity hypothesis requires statistical tests that account for the uncertainty associated with the estimations of the mean differences and the standard deviation of the reference product. Recently, a linear reformulation of the biosimilarity hypothesis has been proposed, which facilitates development and implementation of statistical tests. These statistical tests account for the uncertainty in the estimation process of all the unknown parameters. In this paper, we survey methods for constructing confidence intervals for testing the linearized reformulation of the biosimilarity hypothesis and also compare the performance of the methods. We discuss test procedures using confidence intervals to make possible comparison among recently developed methods as well as other previously developed methods that have not been applied for demonstrating analytical similarity. A computer simulation study was conducted to compare the performance of the methods based on the ability to maintain the test size and power, as well as computational complexity. We demonstrate the methods using two example applications. At the end, we make recommendations concerning the use of the methods. 相似文献
6.
在分析无偿转入土地对粮食生产效率影响的基础上,运用逆概率加权的方法,实证检验了其影响效果与作用机理。研究发现,与有偿转入土地相比,无偿转入土地是基于家庭社区伦理关系的非市场化行为。在解决了样本选择偏误的基础上,无偿转入土地整体上不利于粮食生产效率提升。其中的原因在于,流转租金缺位的无偿转入土地更容易弱化要素价格的信号功能与农户的生产改进意愿,进而使其在土地细碎化与农业长期投资上不能得到与有偿转入土地农户相同的改进。这一消极影响在户主年龄较小或文化程度较高、获得农业补贴较多或市场化水平较低、转入土地规模较小或期限不明确的农户群体中更为突出。长期来看,随着农村集体经济与新型农业经营主体的继续发展壮大,农村土地无偿流转的情况或将持续减少。但同时,也仍应当充分尊重土地无偿流转的现实选择与价值,立足于各地的具体情况来识别与谋划今后规模化经营的具体方向。 相似文献
7.
David J. Sharrow Jessica Godwin Yanjun He Samuel J. Clark Adrian E. Raftery 《Population studies》2018,72(1):1-15
In 2015, the United Nations (UN) issued probabilistic population projections for all countries up to 2100, by simulating future levels of total fertility and life expectancy and combining the results using a standard cohort component projection method. For the 40 countries with generalized HIV/AIDS epidemics, the mortality projections used the Spectrum/Estimation and Projection Package (EPP) model, a complex, multistate model designed for short-term projections of policy-relevant quantities for the epidemic. We propose a simpler approach that is more compatible with existing UN projection methods for other countries. Changes in life expectancy are projected probabilistically using a simple time series regression and then converted to age- and sex-specific mortality rates using model life tables designed for countries with HIV/AIDS epidemics. These are then input to the cohort component method, as for other countries. The method performed well in an out-of-sample cross-validation experiment. It gives similar short-run projections to Spectrum/EPP, while being simpler and avoiding multistate modelling. 相似文献
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对外承包工程是中国与"一带一路"沿线国家经济合作的主要形式之一,加强沿线国家承包工程的国别环境研究有利于降低风险和提高成功率。文章基于现有研究,新增营商环境因素,指标设计上考虑基础设施承包工程的特点,构建了包含6个环境因素、33个指标的工程承包国别环境综合评价体系,运用熵权法对"一带一路"64个国家的工程承包国别环境进行定量评价,对熵权法结果进行了Spearman检验和对国别环境综合值进行了聚类分析。研究结果表明:基础设施环境和经济环境是"一带一路"沿线工程承包重要的国别选择因素;"一带一路"沿线各国的工程承包环境差异显著,分布很不平衡,东南亚、南亚地区国家环境较好,中东欧和西亚北非区域次之,东亚、中亚和独联体地区较差;根据"一带一路"沿线国家工程承包环境评综合价值的大小,可以划分为四种类型:好、较好、较差和差。研究结论不仅为中国在"一带一路"沿线各国开展工程承包提供了国别选择的经验证据,同时为积极落实我国"走出去"战略以及"一带一路"倡议提供了重要参考。 相似文献
10.
We consider importance sampling (IS) type weighted estimators based on Markov chain Monte Carlo (MCMC) targeting an approximate marginal of the target distribution. In the context of Bayesian latent variable models, the MCMC typically operates on the hyperparameters, and the subsequent weighting may be based on IS or sequential Monte Carlo (SMC), but allows for multilevel techniques as well. The IS approach provides a natural alternative to delayed acceptance (DA) pseudo-marginal/particle MCMC, and has many advantages over DA, including a straightforward parallelization and additional flexibility in MCMC implementation. We detail minimal conditions which ensure strong consistency of the suggested estimators, and provide central limit theorems with expressions for asymptotic variances. We demonstrate how our method can make use of SMC in the state space models context, using Laplace approximations and time-discretized diffusions. Our experimental results are promising and show that the IS-type approach can provide substantial gains relative to an analogous DA scheme, and is often competitive even without parallelization. 相似文献