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   54659篇
  免费   2205篇
  国内免费   32篇
  56896篇
  2020年   657篇
  2019年   786篇
  2018年   1163篇
  2017年   1171篇
  2016年   1216篇
  2015年   824篇
  2014年   991篇
  2013年   4807篇
  2012年   1816篇
  2011年   1918篇
  2010年   1130篇
  2009年   1151篇
  2008年   1746篇
  2007年   1728篇
  2006年   1489篇
  2005年   1358篇
  2004年   1323篇
  2003年   1193篇
  2002年   1233篇
  2001年   1800篇
  2000年   1700篇
  1999年   1298篇
  1998年   681篇
  1997年   588篇
  1996年   527篇
  1995年   530篇
  1994年   507篇
  1993年   528篇
  1992年   1018篇
  1991年   964篇
  1990年   967篇
  1989年   869篇
  1988年   827篇
  1987年   822篇
  1986年   822篇
  1985年   868篇
  1984年   685篇
  1983年   591篇
  1982年   473篇
  1979年   677篇
  1978年   495篇
  1976年   460篇
  1975年   608篇
  1974年   642篇
  1973年   610篇
  1972年   552篇
  1971年   489篇
  1968年   556篇
  1967年   551篇
  1966年   484篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
942.
Ordinal data occur frequently in the social sciences. When applying principal component analysis (PCA), however, those data are often treated as numeric, implying linear relationships between the variables at hand; alternatively, non-linear PCA is applied where the obtained quantifications are sometimes hard to interpret. Non-linear PCA for categorical data, also called optimal scoring/scaling, constructs new variables by assigning numerical values to categories such that the proportion of variance in those new variables that is explained by a predefined number of principal components (PCs) is maximized. We propose a penalized version of non-linear PCA for ordinal variables that is a smoothed intermediate between standard PCA on category labels and non-linear PCA as used so far. The new approach is by no means limited to monotonic effects and offers both better interpretability of the non-linear transformation of the category labels and better performance on validation data than unpenalized non-linear PCA and/or standard linear PCA. In particular, an application of penalized optimal scaling to ordinal data as given with the International Classification of Functioning, Disability and Health (ICF) is provided.  相似文献   
943.
Categorical moderators are often included in mixed-effects meta-analysis to explain heterogeneity in effect sizes. An assumption in tests of categorical moderator effects is that of a constant between-study variance across all levels of the moderator. Although it rarely receives serious thought, there can be statistical ramifications to upholding this assumption. We propose that researchers should instead default to assuming unequal between-study variances when analysing categorical moderators. To achieve this, we suggest using a mixed-effects location-scale model (MELSM) to allow group-specific estimates for the between-study variance. In two extensive simulation studies, we show that in terms of Type I error and statistical power, little is lost by using the MELSM for moderator tests, but there can be serious costs when an equal variance mixed-effects model (MEM) is used. Most notably, in scenarios with balanced sample sizes or equal between-study variance, the Type I error and power rates are nearly identical between the MEM and the MELSM. On the other hand, with imbalanced sample sizes and unequal variances, the Type I error rate under the MEM can be grossly inflated or overly conservative, whereas the MELSM does comparatively well in controlling the Type I error across the majority of cases. A notable exception where the MELSM did not clearly outperform the MEM was in the case of few studies (e.g., 5). With respect to power, the MELSM had similar or higher power than the MEM in conditions where the latter produced non-inflated Type 1 error rates. Together, our results support the idea that assuming unequal between-study variances is preferred as a default strategy when testing categorical moderators.  相似文献   
944.
The application of 360° videos raised the attention of educators and researchers, as it appears to be an approachable option to mediate complete environments in educational settings. However, challenges emerge from the perspective of educational psychology. Learning irrelevant cognitive strains might be imposed because it is necessary to navigate through spherical material. However, these potential downsides could be compensated for using signaling techniques. In a two (macrolevel vs. no macrolevel signaling) × two (microlevel vs. no microlevel signaling) factorial between-subjects design plus control group, 215 fifth-and sixth-grade students will watch a 360° video about visual and behavioral characteristics of animals. Learning outcomes, cognitive load, disorientation, and presence will be investigated. It is expected that macrolevel signaling will enhance learning and presence and reduce cognitive load and disorientation. Microlevel signaling will have comparable advantages, but these effects will be more pronounced when macrolevel signaling is implemented.  相似文献   
945.
Curmudgeon personality, which is assessed by having participants evaluate a heterogeneous set of attitude objects, provides an applied value beyond that of more established personality traits. Recent research, for instance, suggests that curmudgeon personality is distinct from the Five Factor Model personality traits and that it predicts unique variance in important criteria, such as job attitudes and well-being. In the current paper we contribute to this literature by testing an explanation of how curmudgeon personality is distinct from other traits—their potential resistance to response distortion. We estimated response distortion for scales of curmudgeon personality and FFM traits across two quasi-experimental studies. As expected, the score shifts between nonapplicant and applicant conditions were smaller for scales of curmudgeon personality compared to scales of emotional stability and conscientiousness. We argue that curmudgeon personality scales may be more resistant to response distortion than are measures of other traits because curmudgeon personality items are semi-implicit and lack an obvious desirable response. The resistance to response distortion should serve as a call to future researchers to test the criterion validity of curmudgeon personality in regard to performance criteria.  相似文献   
946.
947.
The COVID-19 pandemic has highlighted the need for further research evaluating the validity of conducting a battery of neuropsychological assessments virtually compared with face-to-face administration. Previous research has suggested that some neuropsychological assessments yield valid results when administered virtually, however, much of the previous research focused on older adults. To determine the validity of virtually administered neuropsychological tests, 28 healthy participants were assessed using a within-subjects, counter-balanced design. Participants completed a neuropsychological assessment battery covering tests of general intellectual functioning, memory and attention, executive functioning, language and information processing speed, as well as effort. There was no significant difference between face-to-face administration of the neuropsychological battery compared with virtual administration for the majority of the tests used. However, there were significant differences in the Colour Naming Task, with participants making fewer errors on the colour naming task and inhibition/switching task when administered virtually compared with face-to-face administration. There was also a significant age cohort effect in the inhibition/switching task. There was also a trending significant difference in mode of administration for the Verbal Fluency Task. Virtually administered neuropsychological assessments largely provide a valid alternative to face-to-face assessments; however, consideration must be given to test selection as well as the population of participants that are being assessed. Other important considerations must focus on preserving the security and integrity of test materials, as well as administration in a medico-legal setting. Future research should focus on validating assessments with specific patient populations and developing a neuropsychological assessment battery using information technology.  相似文献   
948.
We investigated the role of implicit and explicit associations between harm and COVID-19 vaccines using a large sample (N = 4668) of online volunteers. The participants completed a brief implicit association test and explicit measures to evaluate the extent to which they associated COVID-19 vaccines with concepts of harmfulness or helpfulness. We examined the relationship between these harmfulness/helpfulness COVID-19 vaccine associations and vaccination status, intentions, beliefs, and behavior. We found that stronger implicit and explicit associations that COVID-19 vaccines are helpful relate to vaccination status and beliefs about the COVID-19 vaccine. That is, stronger pro-helpful COVID-19 vaccine associations, both implicitly and explicitly, related to greater intentions to be vaccinated, more positive beliefs about the vaccine, and greater vaccine uptake.  相似文献   
949.
The COVID-19 pandemic brought new attention to the issues of food insecurity faced by individuals throughout the United States, a stressor exacerbated by disruptions to work status and supply chains. The burden of food insecurity likely carries consequences for whether individuals feel capable of pursuing their broad goals and life engagements; put differently, food insecurity may pose a threat to people perceiving a sense of purpose in life. The current study tested this claim across three samples taken during 2020 (n = 2009), 2021 (n = 1666), and 2022 (n = 1975). Participants completed inventories for perceived food insecurity, sense of purpose, depressive symptoms, and anxiety, among other measures. Results found consistent negative associations between food insecurity and sense of purpose across all three samples. In addition, food insecurity moderated associations between sense of purpose and depressive or anxiety symptoms. Sense of purpose was more strongly negatively associated with depressive and anxiety symptoms for those participants who reported no food insecurity. That said, sense of purpose remained negatively associated with psychological distress even among those reporting food insecurity.  相似文献   
950.
The ability to reengage with new attainable goals after major setbacks is a core self-regulatory trait linked to health and well-being. Yet little is known about the extent to which such goal reengagement capacities may shift over time in response to changing contextual circumstances. Using a nationally-representative sample of U.S. adults aged 18–80 (n = 293), the present 1-year study examined whether changes in opportunity to influence life circumstances (perceived control) were coupled with dynamic shifts in goal reengagement capacity for individuals who differed in their levels of control at pandemic onset. Results from multilevel models showed that within-person increases in perceived control during the pandemic predicted corresponding within-person increases in goal reengagement capacity. Moderation models showed that the positive within-person association between perceived control and goal reengagement was pronounced for individuals with lower levels of control at pandemic onset who may be particularly sensitive to periods of opportunity to pursue new attainable goals. Findings inform theories of personality and self-regulation in pointing to contextual circumstances under which goal reengagement capacity exhibits dynamic shifts in populations who differ in their perceived opportunities for control.  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