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   47593篇
  免费   823篇
  国内免费   813篇
教育   28658篇
科学研究   8576篇
各国文化   152篇
体育   2801篇
综合类   2062篇
文化理论   467篇
信息传播   6513篇
  2024年   7篇
  2023年   44篇
  2022年   431篇
  2021年   1088篇
  2020年   808篇
  2019年   399篇
  2018年   2535篇
  2017年   2566篇
  2016年   1986篇
  2015年   1431篇
  2014年   2152篇
  2013年   2615篇
  2012年   3118篇
  2011年   3762篇
  2010年   3617篇
  2009年   2892篇
  2008年   3063篇
  2007年   3819篇
  2006年   2675篇
  2005年   2527篇
  2004年   1549篇
  2003年   1327篇
  2002年   1105篇
  2001年   869篇
  2000年   567篇
  1999年   590篇
  1998年   377篇
  1997年   326篇
  1996年   238篇
  1995年   187篇
  1994年   153篇
  1993年   96篇
  1992年   80篇
  1991年   55篇
  1990年   40篇
  1989年   34篇
  1988年   17篇
  1987年   4篇
  1986年   10篇
  1985年   9篇
  1984年   15篇
  1983年   7篇
  1982年   2篇
  1980年   3篇
  1979年   7篇
  1976年   2篇
  1975年   3篇
  1974年   3篇
  1972年   1篇
  1957年   16篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
891.

Objective

This study investigated complementary feeding practices among four ethnic groups (Han, Uygur, Tibetan, and Zhuang) based on a cross-sectional survey in rural western China.

Methods

In 2005, a stratified multistage cluster random sampling method was used to recruit 9712 children (7411 Han, 1032 Uygur, 678 Tibetan, and 591 Zhuang) between 6 and 35 months of age and their mothers from 45 counties in 10 provinces (autonomous regions, municipalities) in western China.

Results

The rates of early introduction (before 6 months) of complementary foods in four ethnic groups (Han, Uygur, Tibetan, and Zhuang) were 71.30%, 95.95%, 82.40%, and 72.30%, respectively. The Infant and Child Feeding Index (ICFI) for Uygur and Tibetan children was lower than that for Han children at all age groups. Uygur children were more likely to have unqualified ICFI compared with Han children in a multivariate logistic regression (odds ratio (OR)=5.138, 95% confidence interval (CI): 4.340–6.084). A higher level of maternal education, greater family wealth, and the availability of complementary feeding educational materials decreased the likelihood of an unqualified ICFI. The nutritional status of children (Han, Tibetan, and Zhuang) with qualified ICFI was better than that for children with unqualified ICFI.

Conclusions

Appropriate interventions are required to improve complementary feeding practices in rural western China.
  相似文献   
892.
Objective: To investigate the effect of interleukin-18 (IL-18) on immune response induced by plasmid encoding hepatitis B virus middle protein antigen and to explore new strategies for prophylactic and therapeutic HBV DNA vaccines. Methods: BALB/c mice were immunized with pCMV-M alone or co-immunized with pcDNA3-18 and pCMV-M and then their sera were collected for analysing anti-HBsAg antibody by ELISA; splenocytes were isolated for detecting specific CTL response and cytokine assay in vitro. Results: The anti-HBs antibody level of mice co-immunized with pcDNA3-18 and pCMV-M was slightly higher than that of mice immunized with pCMV-M alone, but there was not significantly different (P>0.05). Compared with mice injected with pCMV-M, the specific CTL cytotoxity activity of mice immunized with pcDNA3-18 and pCMV-M was significantly enhanced (P<0.05) and the level of IFN-γ in supernatant of splenocytes cultured with HBsAg in vitro was significantly elevated (P<0.05) while the level of IL-4 had no significant difference (P>0.05). Conclusion: The plasmid encoding IL-18 together with HBV M gene DNA vaccines may enhance specific TH1 cells and CTL cellular immune response induced in mice, so that IL-18 is a promising immune adjuvant.  相似文献   
893.
Academic performance (i.e., grade point average) determines career entry factors as well as career success and is thus crucial for students’ future careers. Besides individual factors such as personality traits, individuals’ social embeddedness has been shown to enhance performance. Regarding academic performance, relationships to fellow students (peers), which bundle into one’s developmental network, are a valuable source of psychosocial and career support because occupying central positions within a social network provides the benefit of being able to access career-enhancing resources. Integrating individual and social-contextual factors for the purpose of examining academic performance is therefore plausible. Research results indicate that personality, especially extraversion, might predict performance through network centrality. In this study, we examined this assumption by focusing on extraversion and centrality in the peer developmental network of recently acquainted German psychology bachelor students (N?=?47, 15% male). In a longitudinal design, we analyzed the impact of extraversion and centrality on students’ academic performance at the end of their studies. Results revealed that centrality (i.e., popularity) mediates the relationship of extraversion with academic performance, indicating that extraverted students (regardless of their agreeableness) are more popular among their peers, which, in turn, enhances their academic performance. That is, the likelihood of getting superior final grades depends on whether students manage to attract peers at the very beginning of their university life, which is easier for extraverts. These findings emphasize the importance of the social embeddedness of people, highlight its long-term effects on performance, and yield several implications for research and practice.  相似文献   
894.
Four pigeons responded on a two-component multiple token-reinforcement schedule, in which tokens were produced according to a random-interval 30-sec schedule and exchanged according to a variable-ratio 4 schedule in both components. To assess the effects of contingent token loss, tokens were removed after every second response (i.e., fixed-ratio 2 loss) in one of the components. Response rates were selectively lower in the loss components relative to baseline (no-loss) conditions, as well as to the within-condition no-loss components. Response rates were decreased to a greater degree in the presence of tokens than in their absence. To control for the effects of changes in the density of token and food reinforcement, two parts consisted of additional conditions where food density and token loss were yoked to those in a previous loss condition. In the yoked-food condition, tokens were produced as usual in both components, but the overall density of food reinforcement in one of the components was yoked to that obtained during a previous token-loss condition. In the yoked token-loss condition, tokens were removed during one component of the multiple schedule at a rate that approximately matched the obtained rate of loss from a previous token-loss condition. Response rates in these yoked components were less affected than those in comparable loss components, despite similar densities of token, exchange, and food reinforcement. On the whole, the results support the conclusion that contingent token loss serves as an effective punisher with pigeons.  相似文献   
895.
论健身性健美操的发展变化   总被引:1,自引:0,他引:1  
健身性健美操是一项常学常新的项目,但科学、实用是最终的目的,新式健美操较旧式健美操在动作编排、上下肢动作分配、教学模式、教学侧重面、动作节奏、器械利用、音乐选择、运动科学化等八个方面发生了较大变化,有了新的创新与发展。  相似文献   
896.
人们常对自己的成败进行归因。早在1976年,斯奈德等是学家就通过研究发现,人们倾向于将成功解释为自由身内在的一些因素所造成;而将失败归因于外部因素。即人们的归因受到自我价值保护的影响。本研究是通过问卷 形式对小学生的学业成绩进行归因,以期了解社会性发民菜并不成熟的未成年人是否也存在此种现象,并最终证明归因受到自我价值保护这种现象在小学中已产生了萌芽,其产生早晚与表现强弱和儿童的社会性发展密切相关。  相似文献   
897.
Based on the complex dispersion relation for the two-dimensional free-surface waves generated by a moving body in the steady Oseen flows, the effect of viscosity on wavelength and wave amplitude was investigated by means of an asymptotic method and a numerical analysis. A comparison between the asymptotic and numerical analysis for the viscous decay factor demonstrates the validity of the perturbation expansions for the wave profile. The numerical result shows that the wavelength of viscous wave is slightly elongated in comparison with that of inviscid wave.  相似文献   
898.
现金流量是一家企业或某个特定项目在一定时期或现金流量计算期内的现金流入、流出的数量及其净额,无论是一家企业一定时期内的现金流量,还是一个特定投资项目计算期内的现金流量,一般都采用以年为单位计算现金流量的方法编制现金流量表.现金流量表分为企业现金流量表和投资项目现金流量表,二者具有相同点也有不同点.现金流量有其变化规律,认识现金流量的变化规律有重要意义.  相似文献   
899.
结构性失业与高教政策调整   总被引:5,自引:0,他引:5  
目前“知识失业”作为一共同难题正严重困绕着世界上几乎每一个国家。自1999年来,我国大学生就业率持续四年走低,引起社会各界的广泛关注,有人用“过度教育”理论来解释这一现象,然而,教育过度只是一种表象,实质是由于教育结构与经济结构之间的矛盾引起的结构性失业,调整高教政策以适应经济的发展在很大程度上能解决大学生就业问题。  相似文献   
900.
浅议加强高职院校档案管理   总被引:6,自引:0,他引:6  
加强档案管理对提升高职学院整体办学管理水平,为教育教学和学院的建设发展服务具有十分重要的意义。高职院校的档案管理存在一些不容忽视的问题,应从加强领导、提高人员素质,稳定队伍、实行现代化以及健全制度等方面进一步加强高职院校档案管理。  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