首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   15736篇
  免费   661篇
  国内免费   207篇
管理学   1861篇
劳动科学   2篇
民族学   63篇
人才学   3篇
人口学   314篇
丛书文集   777篇
理论方法论   354篇
综合类   7395篇
社会学   525篇
统计学   5310篇
  2024年   19篇
  2023年   115篇
  2022年   207篇
  2021年   235篇
  2020年   346篇
  2019年   454篇
  2018年   511篇
  2017年   652篇
  2016年   541篇
  2015年   555篇
  2014年   881篇
  2013年   2106篇
  2012年   1174篇
  2011年   1018篇
  2010年   841篇
  2009年   829篇
  2008年   909篇
  2007年   881篇
  2006年   809篇
  2005年   683篇
  2004年   565篇
  2003年   481篇
  2002年   419篇
  2001年   362篇
  2000年   229篇
  1999年   176篇
  1998年   95篇
  1997年   98篇
  1996年   72篇
  1995年   62篇
  1994年   45篇
  1993年   39篇
  1992年   37篇
  1991年   40篇
  1990年   24篇
  1989年   18篇
  1988年   15篇
  1987年   9篇
  1986年   7篇
  1985年   13篇
  1984年   8篇
  1983年   9篇
  1982年   5篇
  1981年   1篇
  1980年   1篇
  1979年   4篇
  1978年   2篇
  1977年   1篇
  1975年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
311.
以多相瞬变流理论为基础,建立了井筒内气液两相流动模型,并对低压欠平衡钻井中注气量对井内压力的影响关系和规律进行计算和分析。计算分析结果表明,注气量对井内压力的影响除与注气量本身大小有关外,还与井深、井眼与钻柱结构尺寸、井内液相流量和性质等因素密切相关。单纯增大注气量并不一定就必然会导致井内压力的降低,这取决于所给条件下构成井筒内气液两相流体的静液压力和流阻间的平衡关系。介绍的模型及方法对确定低压欠平衡钻井过程中各相关参数、地面压缩机组的配置、以及设计方案等有一定指导意义。  相似文献   
312.
We study a new family of continuous distributions with two extra shape parameters called the Burr generalized family of distributions. We investigate the shapes of the density and hazard rate function. We derive explicit expressions for some of its mathematical quantities. The estimation of the model parameters is performed by maximum likelihood. We prove the flexibility of the new family by means of applications to two real data sets. Furthermore, we propose a new extended regression model based on the logarithm of the Burr generalized distribution. This model can be very useful to the analysis of real data and provide more realistic fits than other special regression models.  相似文献   
313.
This article explores Myanmar teachers’ and community stakeholders’ constructions of disability. We examine how various religious perspectives – particularly Buddhism – inform and shape understandings of impairment and how these beliefs intersect with a strongly medicalised construction of disability. However, in our discussion and exploration of the responses, we also found that the notion of two primary disability ‘models’ – namely the medical model and the social model – lack nuance, complexity, and socio-cultural consideration. Through examining teachers’ and community members’ perspectives of disability in Myanmar, we highlight the importance of socio-cultural variance in understanding local constructions of disability.  相似文献   
314.
Logic models (LMs) have been used in programme evaluation for over four decades. Current debate questions the ability of logic modelling techniques to incorporate contextual factors into logic models. We share experience of developing a logic model within an ongoing realist evaluation which assesses the extent to which, and under what circumstances a community health workers (CHW) programme promotes access to maternity services in Nigeria. The article contributes to logic modelling debate by: i) reflecting on how other scholars captured context during LM development in theory-driven evaluations; and ii) explaining how we explored context during logic model development for realist evaluation of the CHW programme in Nigeria. Data collection methods that informed our logic model development included documents review, email discussions and teleconferences with programme stakeholders and a technical workshop with researchers to clarify programme goals and untangle relationships among programme elements. One of the most important findings is that, rather than being an end in itself, logic model development is an essential step for identifying initial hypotheses for tentative relevant contexts, mechanisms and outcomes (CMOs) and CMO configurations of how programmes produce change. The logic model also informed development of a methodology handbook that is guiding verification and consolidation of underlying programme theories.  相似文献   
315.
随着网络视频运营商收费节目试看的兴起,而节目试看对网络视频运营商诸如市场规模,利润等市场策略的影响所知甚少。本文在考虑网络用户情绪效用情况下,通过构建高质量视频运营商首播节目与后来跟进的低质量视频运营商播出该节目的博弈模型,研究高质量视频运营商首播节目之前提供节目试看对两个运营商收费模式下的节目最优收费价格和免费模式下的最优嵌入广告量以及视频节目提供模式选择的影响。研究表明,高质量视频运营商在节目首播之前提供节目充分试看能够实现节目最优收费价格最高,利润最大,因此节目充分试看是其最优策略;并且低质量运营商在其单位广告收益与用户单位广告"成本"满足一定条件下,高质量运营商提供的节目的充分试看能够减少低质量运营商总利润,因此避免低质量视频运营商搭乘节目试看的顺风车;高质量视频运营商提供节目充分试看情况下,高质量视频运营商只采取收费模式为其最优市场策略,低质量视频运营商采取免费模式为其最优市场策略。本文的研究成果对网络视频运营商日常运营有一定的管理学启示与应用价值。  相似文献   
316.
大芦家地区渐新统东二1亚段主要由三角洲前缘亚相组成,发育的微相类型包括河口坝、水下分流河道、水下决口扇及天然堤、远砂坝、席状砂、分流间湾等,它们在纵横向上表现出多次复合,多次叠加的特征,且各微相的界限和单砂层的界限并不一致;所有这些微相在垂向上的沉积序列可分为均一型、垂向减小型和垂向增大型三类;此外,该区三角洲体系沉积物源主要由河流从西北方向搬运而来,属高建设性的河控型三角洲,其平面呈朵状向东南方或南方延伸,其微相模式的特点是水下分流河道和河口坝沉积位于中心,其他微相分布在它们的外缘。  相似文献   
317.
提高城市群土地利用TFP对合理高效利用土地资源,协调好城市群经济发展、资源配置和环境保护具有重大理论和实践意义.文章运用DEA-Malmquist指数对2003—2016年动态视角下中国城市群土地利用TFP进行测度和时空演变分析,并利用Tobit回归模型对影响城市群土地利用TFP变化的因素进行深入研究.结果表明:从时间维度看,城市群土地利用TFP年均上升0.7%,城市群土地利用TFP增长由技术效率和技术进步"双核驱动",技术效率的提升主要与纯技术效率提升有关,规模效率是技术效率和土地利用TFP提升的瓶颈约束;从空间维度看,晋中、哈长、海峡西岸、中原、长江中游、北部湾、成渝、黔中、关中平原和兰西城市群土地利用TFP呈下降趋势,其余城市群土地利用TFP均呈上升趋势,且京津冀、呼包鄂榆、辽中南、长江三角洲、山东半岛和天山北坡城市群土地利用TFP增长为技术进步和技术效率"双核驱动";从影响因素看,人均GDP和年末金融机构人民币各项贷款余额对中国城市群土地利用TFP具有正向促进作用,城市财政支出占本市GDP的比重和人口密度具有负向阻碍作用.  相似文献   
318.
Bridge penalized regression has many desirable statistical properties such as unbiasedness, sparseness as well as ‘oracle’. In Bayesian framework, bridge regularized penalty can be implemented based on generalized Gaussian distribution (GGD) prior. In this paper, we incorporate Bayesian bridge-randomized penalty and its adaptive version into the quantile regression (QR) models with autoregressive perturbations to conduct Bayesian penalization estimation. Employing the working likelihood of the asymmetric Laplace distribution (ALD) perturbations, the Bayesian joint hierarchical models are established. Based on the mixture representations of the ALD and generalized Gaussian distribution (GGD) priors of coefficients, the hybrid algorithms based on Gibbs sampler and Metropolis-Hasting sampler are provided to conduct fully Bayesian posterior estimation. Finally, the proposed Bayesian procedures are illustrated by some simulation examples and applied to a real data application of the electricity consumption.  相似文献   
319.
In recent years, seamless phase I/II clinical trials have drawn much attention, as they consider both toxicity and efficacy endpoints in finding an optimal dose (OD). Engaging an appropriate number of patients in a trial is a challenging task. This paper attempts a dynamic stopping rule to save resources in phase I/II trials. That is, the stopping rule aims to save patients from unnecessary toxic or subtherapeutic doses. We allow a trial to stop early when widths of the confidence intervals for the dose-response parameters become narrower or when the sample size is equal to a predefined size, whichever comes first. The simulation study of dose-response scenarios in various settings demonstrates that the proposed stopping rule can engage an appropriate number of patients. Therefore, we suggest its use in clinical trials.  相似文献   
320.
In modeling disease transmission, contacts are assumed to have different infection rates. A proper simulation must model the heterogeneity in the transmission rates. In this article, we present a computationally efficient algorithm that can be applied to a population with heterogeneous transmission rates. We conducted a simulation study to show that the algorithm is more efficient than other algorithms for sampling the disease transmission in a subset of the heterogeneous population. We use a valid stochastic model of pandemic influenza to illustrate the algorithm and to estimate the overall infection attack rates of influenza A (H1N1) in a Canadian city.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号