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   62013篇
  免费   2514篇
  国内免费   39篇
  64566篇
  2020年   666篇
  2019年   830篇
  2018年   1191篇
  2017年   1206篇
  2016年   1259篇
  2015年   874篇
  2014年   1029篇
  2013年   4840篇
  2012年   1845篇
  2011年   1945篇
  2010年   1225篇
  2009年   1286篇
  2008年   1694篇
  2007年   1658篇
  2006年   1497篇
  2005年   1296篇
  2004年   1237篇
  2003年   1201篇
  2002年   1177篇
  2001年   2138篇
  2000年   2072篇
  1999年   1515篇
  1998年   684篇
  1997年   605篇
  1995年   586篇
  1992年   1268篇
  1991年   1215篇
  1990年   1185篇
  1989年   1098篇
  1988年   1073篇
  1987年   1023篇
  1986年   979篇
  1985年   1073篇
  1984年   888篇
  1983年   748篇
  1982年   607篇
  1979年   920篇
  1978年   678篇
  1977年   648篇
  1976年   616篇
  1975年   787篇
  1974年   858篇
  1973年   929篇
  1972年   787篇
  1971年   666篇
  1970年   615篇
  1969年   654篇
  1968年   784篇
  1967年   714篇
  1966年   723篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
An electronic apparatus using infrared beams for monitoring the movements of individual bees under dark conditions is described. The searching behavior of workers in an arena was monitored over 2-h periods. Mean ambulatory velocity for one bee over a distance of 100 mm was 45.6±1.51 mm/sec (n=45). Thigmokinesis and temporal activity patterns are illustrated.  相似文献   
32.
33.
陈莲笙道长生于1917年10月25日,上海市人.历任中国道教协会副会长,中国道教协会顾问,上海市道教协会会长.上海市道教协会名誉会长,上海城隍庙住持,上海道学院院长,<上海道教>杂志主编,上海市宗教学会理事,上海市政协第七届委员,上海市政协第八、九届常委等职.  相似文献   
34.
35.
Rats' lever presses on a retractable lever earned brief presentations of discriminative stimuli signalling periods in which responding on an alternative lever was either non-reinforced (extinction) or reinforced on a random ratio schedule. The predictions of two theoretical accounts of this behaviour were tested by studying the effects of omitting either the stimulus signalling the reinforced or that signalling the non-reinforced schedule component. Under these conditions rats' behaviour is determined by the conditioned, affective properties of the stimuli rather than by their purely informational properties.  相似文献   
36.
OBJECTIVE: To examine dysregulation in biological measures associated with histories of abuse in women and whether women with premenstrual dysphoric disorder (PMDD) differ in their dysregulation. DESIGN: Twenty-five women meeting prospective criteria for PMDD and 42 non-PMDD controls underwent structured interview to determine abuse histories and lifetime Axis I diagnoses, excluding those with current Axis I disorders or using medications. MAJOR OUTCOME MEASURES: Plasma cortisol and norepinephrine (NE), heart rate (HR), blood pressure (BP), and vascular resistance index (VRI) were assessed at rest and in response to mental stress. RESULTS: A greater proportion of PMDD women had prior abuse compared with non-PMDD women. Regardless of PMDD status, all abused women had lower plasma NE and higher HRs and tended to have lower plasma cortisol at rest and during stress. Abused women also reported more severe daily emotional and physical symptoms. Greater VRI and BP at rest and during stress were seen only in PMDD women with abuse. CONCLUSION: There is persistent dysregulation in stress-responsive systems in all abused women that cannot be accounted for by current psychiatric illness or medications, and PMDD women may be differentially more vulnerable to the impact of abuse on measures reflecting alpha-adrenergic receptor function.  相似文献   
37.
The ability to make egocentric distance estimates of a single point source of light, seen in darkness and without the cues of changing size and luminance, was investigated in sixteen observers. The attenuation required to maintain constant luminance, when the target was viewed from different distances, was shown to follow the inverse square law providing the angle subtended by the light was less than 20 s arc. Distance changes were also simulated by means of a split mirror which produced vergence cues, or by test lenses to provide accommodation cues. Over the range 0.5 to 9.2 m distance estimates were surprisingly accurate, although there was some overestimation of near and underestimation of far distances. Most observers made good judgements when only convergence cues were varied, whereas no observers made consistently good judgements when only accommodation cues were varied. The difficulties are discussed in terms of the accommodation-convergence link. When distance was simulated by changing convergence and accommodation cues, estimates were not as good as when real distance was changed. Since good estimates were made with brief target exposures, these judgements were not based on subsequent convergence or accommodation changes. It is suggested that the metric or reference against which the apparently absolute judgements were made was the efferent demand signal associated with a 'resting' position of convergence in darkness.  相似文献   
38.
39.
40.
Four experiments were conducted to determine whether echoic memory plays a role in differences between good and poor readers. The first two experiments used a suffix procedure in which the subject is read a list of digits with either a tone control or the word go appended to the list. For lists that exceeded the length of the subjects memory span by one digit (i.e., that avoided ceiling effects), the poor readers showed a larger decrement in the suffix condition than did the good readers. The third experiment was directed at the question of whether the duration of echoic memory is different for good and poor readers. Children shadowed words presented to one ear at a rate determined to give 75-85% shadowing accuracy. The items presented to the nonattended ear were words and an occasional digit. At various intervals after the presentation of the digit, a light signaled that the subject was to cease shadowing and attempt to recall any digit that had occurred in the nonattended ear recently. Whereas good and poor readers recalled the digit equally if tested immediately after presentation, the poor readers showed a faster decline in recall of the digit as retention interval increased. A fourth experiment was conducted to determine whether the differences in echoic memory were specific to speech stimuli or occurred at a more basic level of aural persistence. Bursts of white noise were separated by 9-400 ms of silence and the subject was to say whether there were one or two sounds presented. There were no differences in detectability functions for good and poor readers.  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