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   4358篇
  免费   217篇
  国内免费   28篇
管理学   372篇
劳动科学   1篇
民族学   17篇
人才学   1篇
人口学   137篇
丛书文集   210篇
理论方法论   152篇
综合类   1450篇
社会学   323篇
统计学   1940篇
  2024年   20篇
  2023年   65篇
  2022年   59篇
  2021年   73篇
  2020年   145篇
  2019年   177篇
  2018年   191篇
  2017年   223篇
  2016年   192篇
  2015年   149篇
  2014年   248篇
  2013年   711篇
  2012年   314篇
  2011年   247篇
  2010年   222篇
  2009年   168篇
  2008年   175篇
  2007年   180篇
  2006年   149篇
  2005年   126篇
  2004年   126篇
  2003年   104篇
  2002年   110篇
  2001年   75篇
  2000年   65篇
  1999年   45篇
  1998年   41篇
  1997年   36篇
  1996年   26篇
  1995年   16篇
  1994年   12篇
  1993年   11篇
  1992年   19篇
  1991年   12篇
  1990年   14篇
  1989年   9篇
  1988年   11篇
  1987年   3篇
  1986年   6篇
  1985年   7篇
  1984年   2篇
  1983年   10篇
  1982年   1篇
  1981年   1篇
  1980年   2篇
  1979年   1篇
  1978年   2篇
  1977年   2篇
排序方式: 共有4603条查询结果,搜索用时 368 毫秒
1.
资本创造模型(CC模型)忽视了要素流动对产业空间分布的影响。而发展的新的资本创造模型则认为资本集聚的过程必然伴随着工业劳动力的流动过程。另外,是资本的实际收益而不是名义收益决定资本是否创造。研究结果表明,随着贸易自由度、工业品支出份额及资本贴现率的变大,替代弹性及资本折旧率的变小,将降低对称结构的稳定性,而提高中心-外围结构的稳定性;经济地理空间的产业均衡是集聚力和分散力相互作用的结果。当企业生产工业品的规模报酬递增程度足够显著,或者工业品支出份额很高时,市场拥挤效应将彻底消失,并转化成为促进产业集聚的动力;突破点与持续点的大小比较可以形成不同的关系,这意味着随着贸易自由度的变化,本文发展的资本创造模型可以体现出多样化的产业空间动态演化行为。  相似文献   
2.
Longitudinal studies are the gold standard of empirical work and stress research whenever experiments are not plausible. Frequently, scales are used to assess risk factors and their consequences, and cross-lagged effects are estimated to determine possible risks. Methods to translate cross-lagged effects into risk ratios to facilitate risk assessment do not yet exist, which creates a divide between psychological and epidemiological work stress research. The aim of the present paper is to demonstrate how cross-lagged effects can be used to assess the risk ratio of different levels of psychosocial safety climate (PSC) in organisations, an important psychosocial risk for the development of depression. We used available longitudinal evidence from the Australian Workplace Barometer (N?=?1905) to estimate cross-lagged effects of PSC on depression. We applied continuous time modelling to obtain time-scalable cross effects. These were further investigated in a 4-year Monte Carlo simulation, which translated them into 4-year incident rates. Incident rates were determined by relying on clinically relevant 2-year periods of depression. We suggest a critical value of PSC?=?26 (corresponding to ?1.4 SD), which is indicative of more than 100% increased incidents of persistent depressive disorder in 4-year periods compared to average levels of PSC across 4 years.  相似文献   
3.
4.
巴渝古崖居的分布与地理、地质、交通等诸多因素有关,以成渝交通要道、长江干流和支流为线,串起沿途各个点,由线成面,呈现出渝西、渝东北两头集中、整体北多南少的分布特征。巴渝古崖居大多开凿于明清晚期,这一时期巴渝许多地区战乱频繁、匪患猖獗。古崖居的集中分布与这些地区相吻合,从侧面印证了巴渝古崖居的空间分布特征。巴渝古崖居的广泛开凿体现了古人高超的建筑艺术以及社会历史文化的变迁。  相似文献   
5.
Proportional hazards are a common assumption when designing confirmatory clinical trials in oncology. This assumption not only affects the analysis part but also the sample size calculation. The presence of delayed effects causes a change in the hazard ratio while the trial is ongoing since at the beginning we do not observe any difference between treatment arms, and after some unknown time point, the differences between treatment arms will start to appear. Hence, the proportional hazards assumption no longer holds, and both sample size calculation and analysis methods to be used should be reconsidered. The weighted log‐rank test allows a weighting for early, middle, and late differences through the Fleming and Harrington class of weights and is proven to be more efficient when the proportional hazards assumption does not hold. The Fleming and Harrington class of weights, along with the estimated delay, can be incorporated into the sample size calculation in order to maintain the desired power once the treatment arm differences start to appear. In this article, we explore the impact of delayed effects in group sequential and adaptive group sequential designs and make an empirical evaluation in terms of power and type‐I error rate of the of the weighted log‐rank test in a simulated scenario with fixed values of the Fleming and Harrington class of weights. We also give some practical recommendations regarding which methodology should be used in the presence of delayed effects depending on certain characteristics of the trial.  相似文献   
6.
基于认知隐喻理论,选择德语中14个表征空间性状的形容词,探究其时间映射特质。研究发现:长/短、大/小、远/近、高、深可表征时间,其余则无法表征时间。具体特质如下:存在“一维>二维>三维”映射维度等级;存在“长短>远近>高深/大小”映射宽幅等级;正向形容词比负向更易表征时间。这种映射特质主要与时空相似性、认知思维及隐喻操作有关。  相似文献   
7.
Herein, we propose a data-driven test that assesses the lack of fit of nonlinear regression models. The comparison of local linear kernel and parametric fits is the basis of this test, and specific boundary-corrected kernels are not needed at the boundary when local linear fitting is used. Under the parametric null model, the asymptotically optimal bandwidth can be used for bandwidth selection. This selection method leads to the data-driven test that has a limiting normal distribution under the null hypothesis and is consistent against any fixed alternative. The finite-sample property of the proposed data-driven test is illustrated, and the power of the test is compared with that of some existing tests via simulation studies. We illustrate the practicality of the proposed test by using two data sets.  相似文献   
8.
成都市民旅游感应空间研究   总被引:1,自引:0,他引:1  
旅游感应强度是研究旅游感应空间的一个角度。通过对《成都晚报》“旅游”专刊最近 6年的统计 ,得到全国 34个省级行政区及四川省内分地区作为旅游目的地的出现频次 ,以此频次来表征成都市民对国内及省内旅游目的地的感应强度。利用感应强度从省际和省内不同尺度揭示了成都市民旅游感应空间的特点 ,并发现旅游感应空间的一些新特征  相似文献   
9.
本文研究了随机狄里克莱级数 在随机变量序列{Xn}独立(可不同分布)以及满足等条件时的增长性以及值分布,得到了一些新的结果.  相似文献   
10.
Summary. This study investigates whether there was evidence of increasing risk of still-birth with increasing paternal exposure to ionizing radiation received during employment at the Sellafield nuclear installation before the child was conceived. A significant positive association is found between the total paternal preconceptional exposure to external ionizing radiation and the risk of still-birth (after adjustment for year of birth, social class, birth order and paternal age, odds ratio at 100 mSv 1.24 (95% confidence interval 1.04–1.45)). A summary of the principal scientific findings of this study has been published in the Lancet . This paper describes in detail the statistical methods that were used in the investigation and presents the results in full.  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