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   497篇
  免费   23篇
管理学   94篇
民族学   3篇
人才学   1篇
人口学   21篇
丛书文集   1篇
理论方法论   75篇
综合类   1篇
社会学   267篇
统计学   57篇
  2023年   2篇
  2022年   3篇
  2020年   7篇
  2019年   7篇
  2018年   9篇
  2017年   20篇
  2016年   13篇
  2015年   11篇
  2014年   14篇
  2013年   109篇
  2012年   16篇
  2011年   12篇
  2010年   18篇
  2009年   17篇
  2008年   17篇
  2007年   16篇
  2006年   19篇
  2005年   15篇
  2004年   12篇
  2003年   10篇
  2002年   11篇
  2001年   4篇
  2000年   19篇
  1999年   7篇
  1998年   17篇
  1997年   8篇
  1996年   10篇
  1995年   8篇
  1994年   6篇
  1993年   9篇
  1992年   7篇
  1991年   1篇
  1990年   10篇
  1989年   5篇
  1988年   3篇
  1987年   4篇
  1985年   8篇
  1984年   5篇
  1983年   6篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1978年   2篇
  1977年   4篇
  1976年   2篇
  1975年   2篇
  1974年   1篇
  1973年   1篇
  1972年   3篇
  1970年   1篇
排序方式: 共有520条查询结果,搜索用时 531 毫秒
511.
512.
This study evaluated health benefits of a supported physical activity program for 116 older carers (mean age 64.4 [SD = 7.9], 85% women). Participants undertook a 6-month center-based physical activity program (strength training, yoga, or Tai Chi). Eighty-eight participants (76%) completed the program. Multivariate repeated-measures ANOVA identified overall significant improvement postintervention (p = .004). Univariate analyses revealed significant improvements for balance, strength, gait endurance, depression, and SF-36 (physical component; p < .05). There was no change in the Zarit Carer Burden Scale (p > .05). Change in performance scores did not differ significantly between those with higher and lower attendance at classes, although there was significantly greater improvement in gait endurance and balance (p < .05) in those attending classes run twice weekly than in those attending once-weekly classes. In conclusion, a carer physical activity program, providing additional carer support to facilitate participation, can achieve high levels of involvement by carers and significant health benefits.  相似文献   
513.
The interaction between two species often depends on the presence or absence of a third species. One widespread three-species interaction involves fungal endophytes infecting grasses and the herbivores that feed upon them. The endophytes are allied with the fungal family Clavicipitaceae and grow systemically in intercellular spaces in above-ground plant tissues including seeds. Like relatedClaviceps species, the endophytes produce a variety of alkaloids that make the host plants toxic or distasteful to herbivores. A large number of grass species are infected, especially cool-season grasses in temperate areas. Field and laboratory studies have shown that herbivores avoid infected plants in choice trials and suffer increased mortality and decreased growth on infected grasses in feeding experiments. Resistance to herbivores may provide a selective advantage to infected plants in competitive interactions with noninfected plants. Recent studies have shown that differential herbivory can reverse competitive hierarchies among plant species. Both endophyte-infected and noninfected tall fescue grass (Festuca arundinacea) are outcompeted by orchardgrass (Dactylis glomerata) in the absence of insect herbivory. However, when herbivores are present infected tall fescue outcompetes orchardgrass. These results suggest that the frequency of infection in grass species and grassland communities will increase over time. Several studies are reviewed illustrating increases in infection frequency within grass populations subject to herbivore pressure. Endophytic fungi may be important regulators of plant-herbivore interactions and so indirectly affect the structure and dynamics of plant communities.  相似文献   
514.
Two parallel surveys were carried out based in the north-east of England and Cumbria: one ascertaining statutory social work services provided for child and adult survivors of sexual abuse, the other drawing upon the perceptions of adult survivors of child sexual abuse about existing and desirable forms of provision for adults and children. The surveys indicate the need for greater genuine partnership between service users and statutory agencies in the field of child sexual abuse, similar to that which is being pioneered in the field of adult care and disability. A community-orientated response to sexual abuse, centred on service-users, is required if one of the largest social problems facing us today is to be effectively challenged.  相似文献   
515.
In Hungary for most of the nineteenth century mutual benefit societies played a key role in providing various social groups with aid in case of illness, accident, disability or death. The majority were linked to the burgeoning working-class movement and were voluntary associations whose members had no other recourse in times of adversity. Hungary was undergoing transformation in the nineteenth century. Changes in goods production and the craft guilds accelerated the establishment of workers'benefit societies, and so did the lack of a coherent system of social insurance in the new industrial order. They grew in tandem with the expansion of Hungary's economy and the return of constitutional government in 1867, and flourished from the 1870s to the decade preceding the First World War. Austria and Germany provided theoretical justifications and practical models. By the 1890s voluntary mutual benefit societies faced increasing competition from the State. As the economy and social structures evolved, successive governments sponsored their own insurance programmes. By the turn of the century, private companies were also offering life and accident insurance and the appeal of mutual benefit societies to both workers and the middle class diminished. Between the two world wars, they continued to serve a substantial segment of the population.  相似文献   
516.
Current research on the impacts of the 2007 global economic crisis on international migration takes two different positions. Some studies emphasize the negative impacts while others are more positive. This article argues that these two positions offer simplistic interpretations which fail to take account of the complex micro‐level realities that determine migrant experiences. The article discusses how a small group of migrants from Guayaquil, Ecuador, accumulate and consolidate a complex portfolio of assets both before and during the economic crisis in Spain. Conceptualized in terms of an asset accumulation framework, and based on micro‐level longitudinal trend data, rather than the more generally used macro‐level snapshots or anecdotal evidence, the study highlights the fact that the formalization of legal status or citizenship is a crucial pre‐condition, which sets in motion a ‘virtuous’ cycle of consolidation of an interrelated portfolio of assets, regardless of the wider macro‐economic environment. Even if this turns into a ‘vicious’ cycle, for those losing jobs, to date Spanish welfare benefits have acted as a social protection mechanism.  相似文献   
517.
This study examined the mediating role of self-perceived health between perceived spirituality, religiosity, and life satisfaction among a stratified, random sample of college students, while controlling for gender. Although both models displayed excellent fit criteria, the perceived spirituality and life satisfaction model was fully mediated by self-perceived health χ2 (n=459, 4) = 1.64, p=0.80, CFI =0.99, TLI=0.99), and the perceived religiosity and life satisfaction model was partially mediated by self-perceived health χ2 (n=459, 10) = 22.29, p=0.01 CFI = 0.99, TLI = 0.99). Both models were equal for men and women. Students who describe themselves as spiritual (or religious) are likely to report greater self-perceived health and greater self-perceived health likely influences life satisfaction for both men and women. Results preliminarily support the contention that life satisfaction is related to differing reported health status, whether physical or mental, and that life satisfaction may be influenced by religiosity and spirituality engagement. Implications for colleges and universities are discussed.  相似文献   
518.
Given the high prevalence of tuberculosis (TB) and the mortality rate associated with the disease, numerous models, such as the Gammaitoni and Nucci (GN) model, were developed to model the risk of transmission. These models typically rely on a quanta generation rate as a measurement of infectivity. Since the quanta generation rate cannot be measured directly, the unique contribution of this work is to develop state estimators to estimate the quanta generation rate from available measurements. To estimate the quanta generation rate, the GN model is adapted into an augmented single-room GN model and a simplified two-room GN model. Both models are shown to be observable, i.e., it is theoretically possible to estimate the quanta generation rate given available measurements. Kalman filters are used to estimate the quanta generation rate. First, a continuous-time extended Kalman filter is used for both adapted models using a simulation and measurement sampling rate of 60 s. Accurate quanta generate rate estimates are achieved in both cases. A more realistic scenario is also considered with a measurement sampling rate of one day. For these estimates, a hybrid extended Kalman filter (HEKF) is used. Accurate quanta generation rate estimates are achieved for the more realistic scenario. Future work could potentially use the HEKFs, the adapted models, and real-time measurements in a control system feedback loop to reduce the transmission of TB in confined spaces such as hospitals.  相似文献   
519.
Urban Ecosystems - Although urbanization is increasing worldwide, private gardens may help mitigate the impact of urbanization on butterfly diversity. We investigated how local and landscape...  相似文献   
520.
This paper treats some of the important considerations in constructing an analytical model for the distribution of demand during lead time. It presents a formal model that can be developed along one of two lines. The first has order size and order intensity leading to a compound distribution of period demand, then period demand and lead time giving rise to a compound distribution of demand during lead time. The second has order intensity and lead time giving rise to a compound distribution of lead-time order intensity, then lead-time order intensity and order size leading to a compound distribution of demand during lead time. The paper also condenses the state of the art in a table and proposes some simple classification schemes that could help researchers extend that state of the art.  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