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   1316篇
  免费   193篇
  国内免费   413篇
  2024年   2篇
  2023年   29篇
  2022年   34篇
  2021年   55篇
  2020年   83篇
  2019年   54篇
  2018年   66篇
  2017年   61篇
  2016年   65篇
  2015年   56篇
  2014年   62篇
  2013年   102篇
  2012年   111篇
  2011年   122篇
  2010年   121篇
  2009年   117篇
  2008年   101篇
  2007年   157篇
  2006年   138篇
  2005年   108篇
  2004年   55篇
  2003年   40篇
  2002年   33篇
  2001年   26篇
  2000年   23篇
  1999年   17篇
  1998年   9篇
  1997年   5篇
  1996年   11篇
  1995年   7篇
  1994年   8篇
  1993年   4篇
  1992年   3篇
  1991年   3篇
  1990年   6篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   3篇
  1985年   6篇
  1984年   4篇
  1983年   1篇
  1981年   3篇
  1976年   1篇
  1973年   1篇
排序方式: 共有1922条查询结果,搜索用时 15 毫秒
91.
The directional solidification process of ternary Ag42.4Cu21.6Sb36 eutectic alloy within a wide growth rate range from 2 to 60 μm/s was accomplished at a constant temperature gradient of 50 K/cm. As growth rate increases, the ternary (θ(Cu2Sb) + ε(Ag3Sb) + Sb) eutectic morphology evolves from “lamellar (θ + ε) plus fibrous (Sb)” structure into “(θ + Sb) fibres in continuous ε matrix” structure. The θ and (Sb) phase spacings decrease with the increase of growth rate according to power functions with exponent values of 0.55 and 0.56, respectively. It is also found that the microhardness of directionally solidified Ag42.4Cu21.6Sb36 alloy samples is enhanced with the increase of growth rate, and the decrease of θ and (Sb) phase spacings.  相似文献   
92.
93.
Repeated administration of cognitive tests improves test performance, making it difficult for researchers to gauge the true extent of age-related cognitive decline. The authors examined this issue using data from the Rush Religious Orders Study and linear mixed-effects models. At annual intervals for up to 8 years, more than 800 older Catholic clergy members completed the same set of 19 cognitive tests from which previously established composite measures of cognitive domains were derived. Retest effects on some measures were substantial and continued to accumulate even after 8 annual test readministrations, but effects on other measures were minimal. Across cognitive measures, retest effects were not related to age, sex, or education. Individual differences in retest effects were substantial but not consistent across cognitive measures. The results suggest that retest-based improvement in cognitive test performance can be substantial and persistent.  相似文献   
94.
The authors compared the associations among perceived maternal socialization goals (self-development, filial piety, and collectivism), perceived maternal parenting styles (authoritative, authoritarian, and training), and the social-emotional adjustment (self-esteem, academic self-efficacy, and depression) between Chinese and European American young adults. The mediation processes in which socialization goals relate to young adults' adjustment outcomes through parenting styles were examined. Results showed that European American participants perceived higher maternal self-development socialization goals, whereas Chinese participants perceived higher maternal collectivism socialization goals as well as more authoritarian parenting. Cross-cultural similarities were found in the associations between perceived maternal authoritative parenting and socioemotional adjustment (e.g., higher self-esteem and higher academic self-efficacy) across the two cultural groups. However, perceived maternal authoritarian and training parenting styles were found only to be related to Chinese participants' adjustment (e.g., higher academic self-efficacy and lower depression). The mediation analyses showed that authoritative parenting significantly mediated the positive associations between the self-development and collectivism goal and socioemotional adjustment for both cultural groups. Additionally, training parenting significantly mediated the positive association between the filial piety goal and young adults' academic self-efficacy for the Chinese group only. Findings of this study highlight the importance of examining parental socialization goals in cross-cultural parenting research.  相似文献   
95.
This paper takes a conceptual look at cosmopolitanism and the related issue of what it means to be human in order to arrive at an alternative conceptual framework which is free from empiricist assumptions. With reference to a discussion on Homer’s Iliad, the author develops a ‘humanist’ model of discerning humanity. This model is then compared and contrasted with Martha Nussbaum’s version of cosmopolitanism. The notion of ‘aspect-seeing’ discussed by Wittgenstein in the second part of the Philosophical Investigations is also examined in order to shed light on what it involves to discern humanity. Finally, racism is discussed from the philosophical perspective elaborated in order to highlight its distinctive conceptual features. It is hoped that this paper can refocus our attention on important issues concerning the basis of what it means to see human beings as human beings.  相似文献   
96.
This study examined the relations between cultural values (i.e., individualism and collectivism) and aggression among 460 (234 girls) Chinese adolescents. Conflict level and social status insecurity were examined as potential explaining mechanisms for these relations. The results showed that adolescents' endorsement of collectivism was negatively related to their use of overt and relational aggression as reported by teachers and peers, whereas positive associations were found between the endorsement of individualism and adolescent aggression. Adolescents' conflict level and social status insecurity accounted for a significant part of these associations. Findings of this study demonstrate the importance of examining intracultural variations of cultural values in relation to adolescent aggression as well as the process variables in explaining the relations. Aggr. Behav. 36:187–194, 2010. © 2010 Wiley‐Liss, Inc.  相似文献   
97.
首词和尾词频率对高熟悉度成语识别的影响   总被引:1,自引:1,他引:0  
采用词汇判定法,考察首词频率和尾词频率对高熟悉度四字成语识别的影响。实验结果表明:(1)对高熟悉度成语的识别规律与多层聚类表征模型的观点比较吻合;(2)构成成语的成份词对成语表征有竞争和干扰作用,高频率成份词相对于低频率成份词,对成语表征的竞争和干扰作用较大。  相似文献   
98.
Cellular precipitation (also known as discontinuous precipitation) has been observed at the grain boundaries of a newly developed nickel-based Inconel740H alloy designed for use at 700?°C in advanced ultrasupercritical coal-fired power plants. By means of element mapping and selected area diffraction, the cellular precipitates were identified as Cr-rich M23C6 carbides. The onset of cellular precipitation was found to follow a pucker mechanism in Inconel740H. The cellular precipitates at the grain boundaries, even at low volume fractions, were severely detrimental to the creep strength at 750?°C. The creep rupture life of Inconel740H containing cellular precipitates at grain boundaries was only one-tenth of that for the alloy without cellular precipitates. The reason for the drastically decreased creep rupture life is attributed to the poor resistance of cellular precipitates to crack propagation during creep.  相似文献   
99.
含有生物碱类、皂苷类、萜类、毒蛋白类、重金属类成分的中药易致急性肝损伤.中药对肝脏损伤的原因及机制较为复杂,可能与药物对肝脏的直接毒性或特异性体质有关.此外,中药炮制方法、给药途径、剂型、剂量、疗程及配伍不当也会引起药物性肝损伤.中药所致的药物性肝损伤的诊断主要依据用药史、发病的时间、过程和临床表现并排除其他因素.治疗可选用还原型谷胱甘肽、S-腺苷蛋氨酸、多烯磷脂酰胆碱、熊去氧胆酸、水飞蓟素等药物,重症可选择人工肝脏支持治疗.  相似文献   
100.
阿尔茨海默病(AD)是常见的中枢神经系统变性疾病,是痴呆最常见的病因,发病率高.病理特征为老年斑及神经元纤维缠结.AD的确诊有赖病理学,临床诊断极其耗时.由于尚无准确的早期诊断方法,常使AD患者错过早期治疗的时机,这成为制约有效防控AD的瓶颈问题.因此寻找高敏感性、特异性、无创性的生物学标志物对AD的早期诊断至关重要.本文仅将目前较为广泛研究的生物学标志物及其研究现状作一概述.分别对脑脊液、血液、尿液及唾液中的AD标志物作逐一介绍.  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