全文获取类型
收费全文 | 6481篇 |
免费 | 154篇 |
国内免费 | 190篇 |
专业分类
6825篇 |
出版年
2018年 | 21篇 |
2017年 | 27篇 |
2016年 | 26篇 |
2015年 | 37篇 |
2014年 | 29篇 |
2013年 | 35篇 |
2012年 | 461篇 |
2011年 | 505篇 |
2010年 | 150篇 |
2009年 | 75篇 |
2008年 | 387篇 |
2007年 | 426篇 |
2006年 | 365篇 |
2005年 | 325篇 |
2004年 | 321篇 |
2003年 | 261篇 |
2002年 | 252篇 |
2001年 | 183篇 |
2000年 | 214篇 |
1999年 | 95篇 |
1998年 | 53篇 |
1997年 | 26篇 |
1996年 | 50篇 |
1995年 | 26篇 |
1994年 | 81篇 |
1993年 | 86篇 |
1992年 | 94篇 |
1991年 | 101篇 |
1990年 | 91篇 |
1989年 | 91篇 |
1988年 | 112篇 |
1987年 | 121篇 |
1986年 | 90篇 |
1985年 | 111篇 |
1984年 | 104篇 |
1983年 | 136篇 |
1982年 | 87篇 |
1981年 | 85篇 |
1980年 | 75篇 |
1979年 | 82篇 |
1978年 | 67篇 |
1966年 | 48篇 |
1965年 | 131篇 |
1964年 | 104篇 |
1963年 | 127篇 |
1962年 | 54篇 |
1958年 | 84篇 |
1957年 | 69篇 |
1956年 | 49篇 |
1952年 | 20篇 |
排序方式: 共有6825条查询结果,搜索用时 0 毫秒
261.
262.
Semantic generation can cause episodic forgetting 总被引:1,自引:0,他引:1
Bäuml KH 《Psychological science》2002,13(4):356-360
The repeated retrieval of a subset of previously learned items can cause forgetting of the nonretrieved items. The study reported here investigated whether retrieval-induced forgetting generalizes to a situation in which the retrieved and nonretrieved items are not part of the same experiential episode and task. Subjects learned an item list that they had to recall later in the experiment. In a separate intermediate phase, they repeatedly generated related items from semantic memory, or were presented the same items intact for study. Only the semantic generation of items, and not their presentation for study, induced forgetting of the initially learned items. This result indicates that, first, semantic generation can cause recall-specific episodic forgetting and, second, retrieval-induced forgetting can occur even if the retrieved and nonretrieved items belong to different experiential episodes and tasks. Connections of the present results to other memory phenomena, such as part-set cuing and the generation effect, social cognition, and eyewitness memory, are discussed. 相似文献
263.
Although memory for actual events tends to be forgotten over time, memory for misinformation tends to be retrieved at a stable rate over long delays or at a rate greater than that found immediately after encoding. To examine whether source monitoring errors contribute to this phenomenon, two experiments investigated subjects' memory for the source of misinformation at different retention intervals. Subjects viewed a slide presentation, read a narrative containing misinformation, and, either 10 minutes or 1 week later, completed a recognition test about details seen in the slides and about the source of these details. After the longer retention interval in both experiments, participants were more likely to agree that they had seen misleading information and were also more likely to incorrectly associate the misinformation with the slide event. Theoretical implications of these findings are considered. 相似文献
264.
Buchanan A Califano A Kahn J McPherson E Robertson J Brody B 《Kennedy Institute of Ethics journal》2002,12(1):1-15
Pharmacogenetics offers the prospect of an era of safer and more effective drugs, as well as more individualized use of drug therapies. Before the benefits of pharmacogenetics can be realized, the ethical issues that arise in research and clinical application of pharmacogenetic technologies must be addressed. The ethical issues raised by pharmacogenetics can be addressed under six headings: (1) regulatory oversight, (2) confidentiality and privacy, (3) informed consent, (4) availability of drugs, (5) access, and (6) clinicians' changing responsibilities in the era of pharmacogenetic medicine. We analyze each of these categories of ethical issues and provide policy approaches for addressing them. 相似文献
265.
In previous research Libet (1966) discovered that a critical time period for neural activation is necessary in order for a stimulus to become conscious. This necessary time period varies from subject to subject. In this current study, six subjects for whom the time for neural activation of consciousness had been previously determined were administered a battery of psychological tests on the basis of which ratings were made of degree of repressiveness. As hypothesized, repressive subjects had a longer critical time period for neural activation of consciousness, suggesting the possibility that this neurophysiological time factor is a necessary condition for the development of repression. 相似文献
266.
The positive effect of postlearning sleep on memory consolidation as well as the relationship between sleep-related memory processes and the hippocampal formation are increasingly clarified topics in neurobiology. However, the possibility of a stable relationship between waking mnemonic performance and sleep-dependent hippocampal electric activity is unexplored. Here we report a correlative analysis between sleep-dependent parahippocampal-hippocampal (pHip-Hip) electric activity recorded by foramen ovale (FO) electrodes and different types of memory performances in epileptic patients. Psychological testing was performed days or weeks before electrophysiological recordings. The relative spectral power of the slow activity (below 1.25 Hz) during deep non-REM (NREM) sleep at the right pHip-Hip region correlated positively with the visual memory performance according to Rey-Osterrieth Complex Figure Test (ROCFT). Along the posterior-anterior direction of the hippocampal formation a linear increasing of correlations was observed. The relative power of the activity below 1.25 Hz at the left pHip-Hip during phasic REM sleep correlated positively with verbal learning performance and mnemonic retention values according to ROCFT. It is concluded that the pHip-Hip structures' capacity of producing high amplitude and synchronized slow (< 1 Hz) oscillation during deep NREM sleep is related to the functional power of these structures. We hypothesize that the asymmetric (side-specific) propagation of ponto-geniculo-occipital (PGO) activity to the pHip-Hip region is related to the memory correlates of phasic REM sleep. 相似文献
267.
Stress and memory: opposing effects of glucocorticoids on memory consolidation and memory retrieval 总被引:27,自引:0,他引:27
Roozendaal B 《Neurobiology of learning and memory》2002,78(3):578-595
It is well established that glucocorticoid hormones, secreted by the adrenal cortex after a stressful event, influence cognitive performance. Some studies have found glucocorticoid-induced memory enhancement. However, many studies have reported impairing effects of glucocorticoids on memory function. This paper reviews recent findings from this laboratory on the acute effects of glucocorticoids in rats on specific memory phases, i.e., memory consolidation and memory retrieval. The evidence suggests that the consequences of glucocorticoid activation on cognition depend largely on the different memory phases investigated. Posttraining activation of glucocorticoid-sensitive pathways involving glucocorticoid receptors enhances memory consolidation in a pattern highly similar to that previously described for adrenal catecholamines. Also, similar to catecholamine effects on memory consolidation, glucocorticoid influences on memory consolidation depend on noradrenergic activation of the basolateral complex of the amygdala and interactions with other brain regions. By contrast, memory retrieval processes are usually impaired with high circulating levels of glucocorticoids or following infusions of glucocorticoid receptor agonists into the hippocampus. The hypothesis is proposed that these apparently dual effects of glucocorticoids on memory consolidation and memory retrieval might be related and that the basolateral complex of the amygdala is a key structure in a memory-modulatory system that regulates, in concert with other brain regions, stress and glucocorticoid effects on both memory consolidation and memory retrieval. 相似文献
268.
The presentation and clinical diagnosis of Rett syndrome at various ages and stages are reviewed. In addition to the classical form, variability in phenotype between different atypical Rett forms is given. Obligatory, supportive, and differential diagnostic criteria are summarized. Long-term follow-up findings in ageing Rett women are addressed. 相似文献
269.
Hofmann B 《Science and engineering ethics》2002,8(1):17-29
Technology is believed to have liberated health care from dogmas, myths and speculations of earlier times. However, we are
accused of using technology in an excessive, futile and even detrimental way, as if technology is compelling our actions.
It appears to be like the monster threatening Dr. Frankenstein or like the socerer’s broom in the hand of the apprentice.
That is, the same technology that should liberate us from myths, appears to be mythical. The objective of this article is
to investigate the background for the re-entrance of the myth: How we encounter it and how we can explain it. The main point
is that a myth of technology is normative: it relates ‘is’ and ‘ought’ and directs our actions. This becomes particularly
clear in health care. Hence, if there is a myth of technology, it is an ethical issue, and should be taken seriously. 相似文献
270.