全文获取类型
收费全文 | 57060篇 |
免费 | 2350篇 |
国内免费 | 21篇 |
专业分类
59431篇 |
出版年
2020年 | 526篇 |
2019年 | 642篇 |
2018年 | 906篇 |
2017年 | 939篇 |
2016年 | 1014篇 |
2015年 | 768篇 |
2014年 | 868篇 |
2013年 | 4149篇 |
2012年 | 1628篇 |
2011年 | 1605篇 |
2010年 | 999篇 |
2009年 | 958篇 |
2008年 | 1394篇 |
2007年 | 1440篇 |
2006年 | 1225篇 |
2005年 | 1174篇 |
2004年 | 1097篇 |
2003年 | 1036篇 |
2002年 | 1076篇 |
2001年 | 1848篇 |
2000年 | 1771篇 |
1999年 | 1322篇 |
1998年 | 583篇 |
1996年 | 534篇 |
1992年 | 1212篇 |
1991年 | 1145篇 |
1990年 | 1175篇 |
1989年 | 1024篇 |
1988年 | 1035篇 |
1987年 | 976篇 |
1986年 | 1028篇 |
1985年 | 1103篇 |
1984年 | 843篇 |
1983年 | 772篇 |
1982年 | 542篇 |
1981年 | 533篇 |
1979年 | 966篇 |
1978年 | 658篇 |
1977年 | 604篇 |
1976年 | 584篇 |
1975年 | 821篇 |
1974年 | 961篇 |
1973年 | 1013篇 |
1972年 | 847篇 |
1971年 | 801篇 |
1970年 | 796篇 |
1969年 | 757篇 |
1968年 | 1011篇 |
1967年 | 884篇 |
1966年 | 787篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Barrie B. Alexander Suzanne B. Johnson Randy L. Carter 《Journal of abnormal child psychology》1984,12(2):199-207
The Family Adaptability and Cohesion Evaluation Scales (FACES), a measure of family functioning, contains three scales: cohesion, adaptability, and social desirability. These were slightly modified (FACES- R) on the basis of pilot data and were administered to 42 clinic families (families seeking or receiving psychological services) and 206 nonclinic families. Support for the scales was found in high coefficient alpha reliabilities and similarity of the sample means and standard deviations to those of the standardization sample. However, there was little agreement among family members' scale scores. Therapists' ratings of cohesion and adaptability did not correlate with scale scores among clinic families. There was no difference between clinic and nonclinic samples on the cohesion or adaptability scales, although the social desirability scale did discriminate between groups. Factor analysis suggested that cohesion, adaptability, and social desirability cannot be clearly differentiated using this measure.This work was supported by the American Association of University Women and by Grant R01HD13820 from the National Institute of Child Health and Human Development. 相似文献
992.
993.
994.
995.
Stimulus selection in passive avoidance learning and retention: weanling, periadolescent, and young adult rats 总被引:1,自引:0,他引:1
Periadolescent rats exhibit a number of behavioral differences in comparison with younger or older animals. For instance, periadolescents tend to show enhanced acquisition of simple active avoidance tasks, but impaired acquisition of more complex appetitive and aversive discriminations. In this experiment, rats were trained on a simple passive avoidance task at one of three ages, as weanlings (25 days), periadolescents (35 days), or young adults (45 days). Training occurred in the presence of both a redundant discriminative stimulus and a specified, redundant contextual stimulus. The periadolescents did not differ from either younger or older rats in rate of learning the passive avoidance task. The retention performance of these animals was then tested following a change in either, neither, or both of the redundant cues. When a measure of performance that controls for baseline activity was used, it was observed that periadolescents were not disrupted by a change in the redundant discriminative stimulus, a cue change that clearly disrupted performance in 25- and 45-day-old animals, and tended to be more disrupted by the contextual change than younger or older rats. It is hypothesized that the alterations in performance exhibited by periadolescents may be related to an ontogenetic alteration in stimulus selection modulated by the catecholaminergic systems. 相似文献
996.
Exposure to electric shock produces an analgesic reaction (SIA) that is reversed by opiate antagonists ("opioid" SIA) under some conditions but not under other conditions ("nonopioid" SIA). A number of studies using tail-flick to radiant heat as the measure of pain sensitivity have found that a small number of shocks lead to nonopioid SIA, while a large number of shocks produce opioid SIA. In contrast, a small number of shocks have been reported to produce opioid SIA when the Formalin test was used to measure pain reactivity. However, the Formalin test involves administering a chronic pain stimulus (injection of Formalin into the paw) for an extended period before the shocks. Here it is reported that this "preexperimental" stress is sufficient to convert the SIA after a small number of shocks measured by tail-flick to the opioid form. 相似文献
997.
Rats provided with chronic, continuous access to intracranial self-stimulation (ICS) exhibit discrete episodic response patterns. Response episodes under two conditions were examined for systematic trends in the spacing of times between successive responses (interresponse times; IRTs) to better identify the motivational bases of ICS. Three trends were observed in self-initiated and experimenter-provoked episodes. First, initial responses of spontaneous episodes typically had declining interresponse times. Second, this trend was not present when responses were provoked rather than spontaneous. Third, absolute times between responses varied across conditions, with provoked behavior having significantly lower initial IRTs. The findings suggest that for spontaneously initiated responding a transient facilitatory process cumulates at the beginning of ICS episodes. For provoked responding, it is possible that a manipulation which increased the initial probability of responding over time may have done so by maximizing an initial phasic priming process. At their onset, spontaneous and provoked episodes may be characterized by quantitatively differing motivational profiles. 相似文献
998.
The effect of environmental enrichment on normal rats, rats that received hemidecortication at birth, and rats that received hemidecortication when adult was studied in the Morris water task, which is a spatial navigation task requiring the use of distal cues for successful performance. Enrichment was achieved by housing the rats for 90 days in a large outdoor compound that was designed to model a natural environment. Adult hemidecorticated lab-raised rats were severely impaired in the acquisition of the task but neonatally hemidecorticated rats, although also impaired, showed significant sparing. Postsurgical, but not presurgical, enrichment of adult hemidecorticated rats significantly enhanced their recovery. Enrichment had little effect on neonatally decorticated rats or on normal rats. Although there were no gross anatomical changes associated with enrichment, the paradigm provides both a robust phenomena and a cortically dependent task that is ideal for investigating the processes in the remaining intact hemisphere that must support recovery. 相似文献
999.
Recent data on post-war birth cohorts in the U.S.A. show a negative relationship between IQ and fertility, both actual and expected. Previous investigators (e.g. Bajema, the Reeds and Waller) had found a slightly positive relationship for certain pre-war birth cohorts. This secular change in the relationship between IQ and fertility is replicated here for data on the membership of the American Mensa. Members born before the war exhibit a fertility below but close to that of the equivalent cohorts in the nation as a whole. Members born during and after the war exhibit a fertility that is substantially lower than that of the equivalent national cohorts. Apparently, rising fertility, which characterized the period in which the pre-war birth cohorts bore their children, causes a convergence in birth rates across IQ classes. Declining and/or low fertility, which characterizes the period in which the post-war birth cohorts are bearing their children, has the opposite effect, i.e. a divergence in birth rates across IQ classes, with the lower birth rates in the higher-IQ classes. The membership of Mensa may not be a representative sample of the high-IQ population as a whole, as it seems to attract a disproportionate number of low procreators even for this population. However, there is no reason to believe that changes in fertility rates across cohorts within Mensa, relative to changes in the national fertility rates, do not reliably reflect changes in fertility rates across cohorts within the high-IQ population of the U.S.A. as a whole, again relative to those of the nation, though these rates may be fluctuating around different means. 相似文献
1000.
Sybil B.G. Eysenck G. Easting P.R. Pearson 《Personality and individual differences》1984,5(3):315-321
A total of 1505 children (633 boys and 872 girls) completed the I6 Impulsiveness Questionnaire. Reliabilities, scale intercorrelations and means and standard deviations are given after slight modifications were made to the original scoring key on the basis of factor analyses. Age means for both sexes are also given. 相似文献