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   78320篇
  免费   3100篇
  国内免费   26篇
  81446篇
  2019年   907篇
  2018年   1257篇
  2017年   1289篇
  2016年   1368篇
  2015年   997篇
  2014年   1206篇
  2013年   5773篇
  2012年   2215篇
  2011年   2400篇
  2010年   1510篇
  2009年   1478篇
  2008年   2142篇
  2007年   2127篇
  2006年   1961篇
  2005年   1718篇
  2004年   1619篇
  2003年   1553篇
  2002年   1664篇
  2001年   2393篇
  2000年   2353篇
  1999年   1813篇
  1998年   895篇
  1997年   838篇
  1996年   838篇
  1995年   754篇
  1992年   1574篇
  1991年   1450篇
  1990年   1440篇
  1989年   1330篇
  1988年   1322篇
  1987年   1246篇
  1986年   1366篇
  1985年   1369篇
  1984年   1165篇
  1983年   1055篇
  1982年   758篇
  1981年   769篇
  1979年   1235篇
  1978年   916篇
  1976年   757篇
  1975年   1027篇
  1974年   1153篇
  1973年   1262篇
  1972年   1028篇
  1971年   1002篇
  1970年   901篇
  1969年   945篇
  1968年   1184篇
  1967年   1065篇
  1966年   973篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
992.
993.
Golden hamsters are able to detect differences in the height of a platform from which they jump, as measured by their increasing latencies prior to jumping from increased elevations. This ability is very effective when optical information is available, but it is also present when hamsters jump in total darkness. A second experiment shows that, when hamsters are placed on a real physical cliff, they preferentially use tactile information over visual information to guide their choice of the side from which to descend. In a nonvisual setting, tactile stimulation is used in conjunction with other types of cues. Evidence is provided to suggest that these cues are of an acoustical nature.  相似文献   
994.
This study was designed to determine possible differences in the cognitive, perceptual, and personal-social development of prematurely and maturely born 3-yr.-olds which might foreshadow later learning problems. The subjects were 40 prematurely born graduates of a neonatal intensive care unit (birth weight less than 2,500 gm, less than 37 wk. gestation) matched on the pair-level with full-term controls on sex, race, post-conceptual age, and socioeconomic background. All subjects were singletons and parity was matched at the group level. No differences were found between the groups on tests of higher mental processes including the General Cognitive, Verbal, Quantitative, and Memory Scales of the McCarthy Scales of Children's Abilities, and researcher-devised measures of problem-solving competence. No differences in parental reports of personal-social development were noted. Prematures did not perform as well as controls on perceptual performance tasks, and this difference was interpreted as reflecting relatively impaired visual-motor coordination.  相似文献   
995.
This annotated listing is of group reports pertaining to therapeutic strategies utilized with infants and young children who have cerebral palsy. The studies are organized by type of design used.  相似文献   
996.
A longitudinal study of the development of hand preference in 152 adopted and 120 nonadopted (control) infants measured in natural behavioral situations at both 12 and 24 mo. of age is reported. Significant developmental trends were observed for both increasing strength and direction of handedness. Less than 10% of the infants exhibited a clear preference at 12 mo. of age, whereas about 30% were lateralized at 24 mo., with more boys than girls being left-handed. In contrast, over 90% of the parents of these children (both biological and adoptive parents of the adopted children and parents of the nonadopted children) were lateralized. Perhaps because so few infants were lateralized at either age, parent-offspring resemblances were inconsistent and the number of significant parent/child correlations was about that expected on the basis of chance alone.  相似文献   
997.
Data from several studies of college students yielded moderate correlations among faces recognition scores (ratings, answers to questions), but association between visual imagery and recognition memory for faces was small to medium. Women reported more vivid and better controlled visual imagery for faces than men.  相似文献   
998.
This paper presents the results of an in-depth study of parameters characterizing sequenced saccadic eye movements for a group of dyslexic children and a comparative normal control group with ages in the range greater than 8.0 yr. and less than 13.0 yr. No parameters were statistically different for the two groups, which supports the findings of Brown, et al. and contradicts the findings of Pavlidis. Our results indicate that sequenced saccadic eye movements are not diagnostically useful for early detection of dyslexia.  相似文献   
999.
Previous research aimed at quantifying and reducing the decrements encountered in performing manual tasks in cold weather has not described the relationships between task characteristics and cold-induced impairments. The amount of decrement and, often times, the optimal means for reducing the decrement, appear to be task-specific. The research reported here is one in a series of studies formulated to explore those relationships. The strategy is to use tasks from the battery developed by Fleishman (1967) to measure the factorially 'pure' abilities needed to perform all manual tasks. 24 U.S. Marines performed this battery of nine tasks across a range of cold temperatures. To determine if the decrement due to wearing gloves might be less than the decrement due to cold hands as the air temperature decreased, performance on the battery of tasks was measured with and without gloves. Only three of the tasks (abilities) were affected by cold temperatures, and the amount of decrement increased as the air temperature decreased. Three tasks deteriorated due to wearing of gloves, two of those affected by cold and one other. Temperature affected performance independently of the glove effect. Half of the subjects did not complete bare-handed testing at -18 degrees C (approximately 20 min.), indicating this is the lower end of the temperature range in which bare-handed performance for more than a few minutes is practical.  相似文献   
1000.
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