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   23854篇
  免费   858篇
  国内免费   12篇
  24724篇
  2020年   240篇
  2019年   256篇
  2018年   397篇
  2017年   434篇
  2016年   434篇
  2015年   275篇
  2014年   366篇
  2013年   1831篇
  2012年   693篇
  2011年   755篇
  2010年   459篇
  2009年   432篇
  2008年   641篇
  2007年   608篇
  2006年   558篇
  2005年   495篇
  2004年   484篇
  2003年   454篇
  2002年   496篇
  2001年   743篇
  2000年   756篇
  1999年   564篇
  1998年   270篇
  1997年   228篇
  1992年   453篇
  1991年   415篇
  1990年   451篇
  1989年   422篇
  1988年   404篇
  1987年   402篇
  1986年   413篇
  1985年   436篇
  1984年   344篇
  1983年   308篇
  1982年   244篇
  1981年   223篇
  1979年   394篇
  1978年   282篇
  1977年   251篇
  1976年   224篇
  1975年   346篇
  1974年   380篇
  1973年   352篇
  1972年   331篇
  1971年   291篇
  1970年   262篇
  1969年   323篇
  1968年   361篇
  1967年   324篇
  1966年   325篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
We report the performance of a brain-damaged subject showing a particularly pure dissociation between impairment in processing thematic roles and spared ability to process the morphological structure of sentences. The thematic role processing impairment was observed in both comprehension and production of active and passive reversible sentences, although it was more severe for the latter sentence type. This pattern of performance poses interesting challenges for current conceptions of the nature of language breakdown in aphasia and for models of normal sentence processing.  相似文献   
942.
Tested a preventive intervention in which peer telephone dyads were developed for low-income, community-living, elderly women with low perceived social support. After an initial assessment, respondents were randomly assigned to either an assessment-only control or received 10 weeks of friendly staff telephone contact. After a second assessment, participants receiving the staff contact were randomly assigned to continue that contact or were paired in dyads to continue phone contact with one another. Dependent variables were measures of perceived social support, morale, depression, and loneliness. All groups, particularly the staff contact group, showed some improvement in mental health scores over time, but there were no significant differences between intervention groups, or between intervention and assessment-only control groups. The results suggest that participation in the study and in personal assessment interviews at home were probably morale enhancing, and that additional telephone contact did not significantly add to that effect. Evidence also indicates that, in this sample, low perceived family support was significantly related to poor mental health, so it is possible that a program designed to increase friend support may have been the wrong intervention.  相似文献   
943.
This study was designed to test whether information transmission between the perceptual and motor levels occurs continuously or in discrete steps. Ss performed visual search across nontargets that shared visual features with one of two possible targets, each assigned to a different response. In addition to reaction time, psychophysiological measures were used to assess the duration of target search and the onset of central and peripheral motor activity. Nontargets sharing features with a target selectively activated the response associated with that target, even when it was not present in the display. This suggests that information transmission to the motor level can consist of fine-grained visual information and that visual search and response selection occur in parallel.  相似文献   
944.
Task dynamics corresponding to rhythmic movements emerge from interactions among dynamical resources composed of the musculature, the link segments, and the nervous and circulatory systems. This article investigated whether perturbations of interlimb coordination might be effect over circulatory and nervous elements. Stiffness of wrist-pendulums oscillated at a common tempo and at 180 degrees relative phase was perturbed through the use of tonic activity about an ankle. Left and right stiffnesses, the common period, and the phase relation all changed. Stiffnesses increased with ankle torque in proportion to the wrist's inertial load. Despite different changes in stiffness at the two wrists, isochrony was preserved. The stability was shown to be consistent with the proportionality of changes in stiffness to the inertial loads. The phase departed from antiphase in proportion to the asymmetry of inertial loads. The size of departures decreased with increasing ankle torque. An account was developed in terms of muscular, circulatory, and nervous functions.  相似文献   
945.
Immediate post-training subcutaneous administration of lysine vasopressin (LVP, 0.003-1.00 microgram/kg) enhanced retention, whereas the vasopressin antagonist AAVP (0.01-0.30 microgram/kg) impaired it, in male Swiss mice tested 48 h after training in an inhibitory avoidance task. Both effects were dose-dependent. Neither LVP nor AAVP affected response latencies in mice not given the footshock on the training trial. The simultaneous administration of AAVP at a dose (0.01 microgram/kg) which had no effect on retention shifted the dose-response curve of LVP to the right. Nicotine (1.0-30.0 micrograms/kg, sc), a central nicotinic cholinergic agonist, also facilitated retention in a dose-related manner without affecting the retention performance of unshocked mice. The effect of nicotine was prevented by the central acting nicotinic cholinergic receptor antagonist mecamylamine (5 mg/kg, sc.). In contrast, neither hexamethonium (5 mg/kg, sc), a peripheral acting nicotinic receptor blocker, nor atropine (0.5 mg/kg, sc) or methylatropine (0.5 mg/kg, sc), two anticholinergic drugs which are known to act on muscarinic cholinergic receptors, prevented the effect of post-training nicotine. The effects of LVP and nicotine were time-dependent, suggesting that both treatments enhanced retention by influencing post-training processes involved in memory storage. Low doses of nicotine (1.50 microgram/kg, sc) or the central anticholinesterase physostigmine (35 micrograms/kg, sc) and LVP (0.003 microgram/kg, sc), which had no effect on retention when administered alone, produced a synergistic interaction when given together following training. The influence of LVP (0.03 microgram/kg, sc) on retention was prevented not only by AAVP (0.01 microgram/kg, sc) but also by mecamylamine (5 mg/kg, sc), whereas the effects of nicotine (10.0 micrograms/kg, sc) were prevented only by mecamylamine. These results suggest that the enhancement of retention induced by vasopressin is probably due to an activation of central nicotinic cholinergic mechanisms which are critical for memory formation.  相似文献   
946.
The aim of this study was to assess the validity of the notion that anxiety influences maternal style in monkeys. To this end, we investigated the correlations between measures of the quality of mother-infant relationship and scratching, a behavior pattern that reflects a state of anxiety. The subjects were seven group-living macaque mothers and their infants observed during the first 12 weeks postpartum. Postpartum scratching by the mothers was positively correlated with both maternal possessiveness and maternal warmth, two composite measures of the quality of mother-infant relationship that reflect a possessive and attentive maternal style. Evaluation of the correlations between maternal rank and scratching before and after parturition indicated that interactions with their infants, not those with other group companions, were the main source of anxiety for the mothers. These results support the notion that anxiety influences maternal style in monkeys and suggest that studies aimed at investigating physiological and social correlates of maternal emotionality in nonhuman primates could use scratching as a useful and simple behavioral measure.  相似文献   
947.
The present study investigated the role of verbal labeling and exposure duration in implicit memory for novel visual patterns. Encoding condition was varied in Experiment 1. Two encoding conditions discouraged verbal labeling and a third required it. In Experiment 2, exposure duration was manipulated to determine whether a new memory representation could be formed after a single 1-s exposure. The results suggest that verbal labeling is not necessary to support priming. Type of encoding did not affect implicit memory, but had a pronounced effect on explicit memory. Furthermore, a single 1-s exposure was sufficient to support priming, and priming was not further enhanced by longer stimulus exposures. In contrast, recognition performance was enhanced by a longer stimulus duration. Thus, priming effects with these novel figures are likely to be supported by newly acquired representations rather than by preexisting memory representations.  相似文献   
948.
Susan G. Ziegler 《Sex roles》1991,25(3-4):119-127
The differences in both perceived benefits and attitudes toward running between male and female runners, and between runners who classified themselves as competitive runners (CR) or recreational runners (RR), was the focus of this study. Four-hundred and two runners completed the Ten-Minute Survey for Runners within two weeks of completing a marathon. RR, more so than CR, perceived greater benefits from running. However, CR expressed a more positive attitude toward running and its role in their lives than did RR. Men perceived running to be more beneficial to them than women. However, women, more so than men, felt running had a positive effect on self-image and their lives were richer because of running. Future research concerns on the effects of competition on the lives of women are explored.  相似文献   
949.
Even though in Italy, as in the majority of Mediterranean countries, the increase in suicide rates is not among the highest in Europe, between 1969 and 1989 it showed a sharp upswing (+43% among males and +31% among females). In terms of geographical differences, the regions with the highest suicide rate are the northern ones (up to twice the national average). The age groups with the highest suicide risk are those over 74 years (in 1989 the rate among males over 65 was the highest of all: 31.3 per 100,000). The differences in the between-sexes distribution show that among females over 65 years old the suicide rate rose by 70% between 1974 and 1989, versus 77% for males of the same age. The preliminary epidemiological results of one of two Italian centers are presented. These centers are collaborating with the WHO/EURO Multicenter Study on Parasuicide; parasuicide rates are higher for females than for males (55.9 per 100,000, as against 38.1 for males), while the age group at highest risk is seen to be young women (15-24 years), with a specific rate of 115.6.  相似文献   
950.
The present investigation focused upon the impact of gender and various powerful and less powerful linguistic features on the communication of unfamiliar male and female college students. Same-sex and mixed-sex dyads were recorded as they engaged in discussions regarding suggestions for a bogus freshman orientation booklet. Although few gender differences were found, the result of a factor analysis yielded three factors: questions, suggestions, and process variables. These factors are consistent with a power perspective in the use of various linguistic features. However, the present findings suggest that gender and power alone cannot explain differences in communication styles. Rather, the results suggest the need to consider other aspects of the speaker to explain differences that occur in the use of language.  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