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81.
82.
马克思和恩格斯在《德意志意识形态》中对城市问题进行了系统考察。我们认为这种考察存在两个充满张力的内在逻辑维度:第一种逻辑是从现实的社会生产出发,建立在分工、交往、所有制等社会关系基础之上的历史逻辑;第二种逻辑是立足于资本主义批判,对城市经济和政治进行批判的批判逻辑。在历史逻辑下,马克思和恩格斯将城市视为人类社会生产发展的必然产物和文明形态,客观上高度肯定城市对于人类文明的重要意义,并在《资本论》等著作中将这一思想发展完善。而在批判逻辑下,马克思和恩格斯从私有制和阶级对立的演进来说明城市发展,将城市视为私有制的产物及资本主义社会的典型,从而在价值和道德维度批判资本主义城市的弊端。两种逻辑对于当代中国城市发展都具有重要的指导意义。  相似文献   
83.
We consider a semi-parametric approach to perform the joint segmentation of multiple series sharing a common functional part. We propose an iterative procedure based on Dynamic Programming for the segmentation part and Lasso estimators for the functional part. Our Lasso procedure, based on the dictionary approach, allows us to both estimate smooth functions and functions with local irregularity, which permits more flexibility than previous proposed methods. This yields to a better estimation of the functional part and improvements in the segmentation. The performance of our method is assessed using simulated data and real data from agriculture and geodetic studies. Our estimation procedure results to be a reliable tool to detect changes and to obtain an interpretable estimation of the functional part of the model in terms of known functions.  相似文献   
84.
In this paper, we propose a new partial correlation, the so-called composite quantile partial correlation, to measure the relationship of two variables given other variables. We further use this correlation to screen variables in ultrahigh-dimensional varying coefficient models. Our proposed method is fast and robust against outliers and can be efficiently employed in both single index variable and multiple index variable varying coefficient models. Numerical results indicate the preference of our proposed method.  相似文献   
85.
Studies were carried out in two mining pond complexes in an industrial landscape. The first complex (consisting of six ponds) was located in an urban area and the second one (consisting of six ponds) in a woodland area. The aims of the study were to assess the diversity of benthic oligochaetes and to evaluate which environmental variables are most important in determining variations in the community structure in ponds of varying location. In total, 21 oligochaete species were recorded (7–11 in the urban ponds, 11–15 in the woodland ponds). Aulodrilus pluriseta, Aulodrilus japonicus and Ophidonais serpentina were only found in the woodland ponds, while Potamothrix bavaricus only occurred in the urban ponds. Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Chaetogaster diaphanus and Ophidonais serpentina dominated in the woodland ponds, whereas Limnodrilus hoffmeisteri, Limnodrilus claparedeanus, Potamothrix bavaricus and Tubifex tubifex prevailed in the urban ponds. The total density of oligochaetes was higher in the urban ponds thought the values of the diversity indices were higher in the woodland ponds. The local diversity of the ponds was high, while the among-site diversity made only a small contribution to the regional diversity. Nonetheless, a cluster analysis divided all of the ponds into two distinct groups depending on their location. CCA analysis showed that conductivity, pH, total hardness, alkalinity, the concentration of chlorides and the content of organic matter in the bottom sediments were most associated with the distribution of some oligochaete species among the ponds studied.  相似文献   
86.
Tropical forested ecosystems provide multiple ecosystem services to rural and urban landscapes, with carbon storage gaining particular attention. Deforestation due to rural-urban transitions may lead to a reduction in carbon storage ability. Coastal mangrove forests are particularly at risk from deforestation due to their location in the rapidly urbanizing coastal zone, and the city state of Singapore is an extreme example, losing as much as 90 % of its original mangrove cover due to land reclamation and reservoir construction. Knowledge of mangrove ecosystem services may allow better conservation, restoration and incorporation of remaining mangrove patches into the urban landscape. Focusing on the regulating ecosystem service of carbon storage, mangrove carbon stocks have been estimated for Singapore using a combination of field and remote sensing techniques. Biomass carbon showed substantial spatial variation, with old, contiguous mangrove patches containing a higher density of biomass carbon than fragmented, river-fringing or restored mangroves. In total, national biomass carbon equated to 116,117.1 megagrams of carbon (Mg C), and a coarse estimate of the total carbon stock (including soil carbon) suggests that Singapore’s mangroves may store 450,571.7 Mg C. While lower than other regional estimates focused on natural, oceanic mangroves, this is a significant carbon stock for a disturbed, urban mangrove system, and may be equivalent to the average annual carbon emissions of 621,000 residents. This analysis, alongside a review of other urban forest studies, highlights the importance of forested ecosystems such as mangroves in providing a carbon storage ecosystem service to urban areas.  相似文献   
87.
Recent studies have proposed alternative birth outcome measures as means of assessing infant mortality risk; nevertheless, there hasn’t yet been an integrated analysis of these approaches. We review 14 strategies, including various combinations of birth weight, gestational age, fetal growth rate, and Apgar scores—as predictors of early neonatal, late neonatal, and postneonatal mortality, and infant mortality. Using the NCHS linked birth/infant death file for 2001, we construct multivariate logit models and assess the associations between each of the 14 key birth outcome measures and four mortality outcomes. We find that all evaluated birth outcome measures are strong predictors, but Apgar scores are the strongest among all models for all outcomes, independent of birth weight and gestational age. Apgar scores’ predictive power is stronger for Mexican-, white-, and female-infants than for black- and male-infants. Second, all birth outcome measures remain significantly associated with mortality, but their predictive power reduces drastically over time. These findings suggest a rule of thumb for predicting infant mortality odds: when available, Apgar scores should always be included along with birth weight (or LBW status) and gestational age. Additionally, these findings argue for the continued study of low birthweight, gestational age, and Apgar scores as independently salient health outcomes.  相似文献   
88.
劳动参与率与劳动力增长:1982~2050年   总被引:3,自引:0,他引:3  
劳动参与率是影响劳动力变化的三要素之一。它一方面具备相对稳定的模式,另一方面又受到一系列个人和外部因素的影响。文章基于普查数据,着重分析了劳动参与的年龄模式和主要影响因素,并预测了未来劳动力的发展趋势。结果发现,中国劳动参与年龄模式正趋向于稳定的倒U形,存在着明显的性别、城乡差异。回归结果表明,高中以上受教育程度可大大提高劳动参与,特别是女性的劳动参与,表明人力资本是未来劳动力发展的一个根本因素。预测结果显示,劳动力规模10年后将不可避免地出现负增长,同时中老年劳动力的比重也会大幅上升。对此,应采取相应措施以减轻劳动力变化所带来的震荡。  相似文献   
89.
马梅 《科学发展》2014,(4):8-12
互联网时代第三方支付的发展,揭示了企业"控制用户信息流以控制支付流,控制支付流以控制资金流;获得用户网络接入权胜过获得资本所有权,获得数据投入量胜过获得资金投入量"的新规则。大平台日益成为金融机构控制用户信息流、获得用户网络接入权的重要载体,在平台组合上加载信用有关数据流日益成为形成金融机构风险管理能力的重要生产资料。在互联网时代推进上海国际金融中心建设,既要继续重视金融机构集聚,更要注重鼓励企业赢得全国性用户网络接入权,加强平台组合,增强信用数据流。上海应依托自贸试验区推进互联网金融监管创新;牵头建立长三角征信联盟集团公司;搭建本地金融机构网聚平台。  相似文献   
90.
This article investigates the impact of democracy on growth by simultaneously considering a country's secular‐historical experience of democracy and current political regime. The results obtained show that the effect of democracy on growth exhibits an asymmetrical pattern depending on the country's democracy stock. Only in “democratic countries” with “prolonged experiences of democratic rule” can democracy promote growth. This claim stands in contrast to the earlier literature in which there is either no consistent relationship between growth and democracy or perhaps a nonlinear relationship. This conclusion provides circumstantial support for the claim of the “democracy promotes growth” hypothesis. (JEL O43)  相似文献   
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