全文获取类型
收费全文 | 19294篇 |
免费 | 393篇 |
国内免费 | 193篇 |
出版年
2012年 | 1855篇 |
2011年 | 2141篇 |
2010年 | 473篇 |
2009年 | 235篇 |
2008年 | 1679篇 |
2007年 | 1634篇 |
2006年 | 1489篇 |
2005年 | 1288篇 |
2004年 | 1122篇 |
2003年 | 1066篇 |
2002年 | 953篇 |
2001年 | 611篇 |
2000年 | 832篇 |
1999年 | 338篇 |
1998年 | 94篇 |
1997年 | 70篇 |
1996年 | 88篇 |
1995年 | 51篇 |
1994年 | 86篇 |
1993年 | 128篇 |
1992年 | 108篇 |
1991年 | 122篇 |
1990年 | 112篇 |
1989年 | 109篇 |
1988年 | 129篇 |
1987年 | 139篇 |
1986年 | 103篇 |
1985年 | 134篇 |
1984年 | 129篇 |
1983年 | 145篇 |
1982年 | 102篇 |
1981年 | 101篇 |
1980年 | 87篇 |
1979年 | 95篇 |
1978年 | 88篇 |
1966年 | 48篇 |
1965年 | 134篇 |
1964年 | 105篇 |
1963年 | 126篇 |
1962年 | 55篇 |
1958年 | 192篇 |
1957年 | 156篇 |
1956年 | 143篇 |
1955年 | 107篇 |
1954年 | 87篇 |
1953年 | 86篇 |
1952年 | 61篇 |
1951年 | 76篇 |
1950年 | 58篇 |
1949年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
The uncertain and complex lineage of the Lumbee American Indian tribe has made the issue of identity of prime concern. The cultural identification, racial identification, bicultural competence, and perceived school environment for 103 Lumbee Indian high school students were examined in this study. Higher self-ratings on American Indian cultural competence and American Indian cultural identification than on White cultural competence and White cultural identification were found, and t-test comparisons revealed no gender differences on responses to the instruments. Analysis of variance was conducted to assess whether differences in perceived school environment could be attributed to cultural orientation. Rather than appearing assimilated, this generation of Lumbees tends to exhibit J. E. Helms's (1995b) Internalization identity status and an American Indian cultural orientation. 相似文献
994.
A number of measures have been used in epidemiological studies of children's exposure to community violence, yet the quality
of these instruments is not uniformly good. This paper undertakes a systematic review of the most commonly used (or most promising)
self-report or interview-administered instruments, with regard to their conceptual bases and psychometric properties. Based
on the review, recommendations are made for working with the current state of the science in order to move the field forward.
A key recommendation is for sounder conceptualization of work in the field and greater transparency in the reporting of research,
in order to facilitate the comparability of studies. 相似文献
995.
The aim of this study is to analyze how the length of time a patient spends in an Intensive Care Unit (ICU) affects close relatives, with regard to specific clinical variables of personality, family relationships and fear of death. The study group consisted of 57 relatives of seriously ill patients admitted to the ICU of "Virgen del Rocío" Rehabilitation and Trauma Hospital (Seville, Spain). The instruments applied were: a psychosocial questionnaire, clinical analysis questionnaire, family environment scale and fear of death scale. The relatives of patients admitted to ICU obtained higher scores in hypochondria, suicidal depression, agitation, anxious depression, guilt-resentment, paranoia, psychasthenia, psychological maladjustment and self-expression, and less in fear of their own death, as when compared to interviews with the same relatives 4 years later. The length of time a patient spent in the ICU influenced relatives in some clinical variables of personality, family relationships and fear of death 相似文献
996.
In the context of a medium-term study designed to integrate the simulation of different types and processes of learning-such as classical, operant, and some cognitive types--one must start with other more elementary ones that are facilitators of the more complex types and processes. Of special interest is habituation, owing to the filtering out of irrelevant stimuli, which means that the simulated agent does not have to respond to them. This paper presents two difference functions constructed to computationally simulate the characteristics that define habituation. The behavior of these functions is described, as are differences arising from stimulus intensity and interstimulus intervals. Results are compared with existing empirical data. 相似文献
997.
This study investigated the relationships between impulsivity, intelligence, and academic failure in a sample of 241 secondary school students who completed Thurstone's (1938) Primary Mental Abilities (PMA) test and Dickman's (1990) and Barratt's (1985) impulsivity questionnaires (DII and BIS-10, respectively). Results show an inverse relationship between impulsivity and intelligence, specific to the scales with higher loadings on crystallized intelligence, and a positive relationship between impulsivity and academic failure. These results indicate that impulsivity is not directly related to intelligence and may act as a moderator variable between individuals' resources and their achievements. 相似文献
998.
Structure and stimulus familiarity: a study of memory in chess-players with functional magnetic resonance imaging 总被引:1,自引:0,他引:1
A grandmaster and an international chess master were compared with a group of novices in a memory task with chess and non-chess stimuli, varying the structure and familiarity of the stimuli, while functional magnetic resonance images were acquired. The pattern of brain activity in the masters was different from that of the novices. Masters showed no differences in brain activity when different degrees of structure and familiarity where compared; however, novices did show differences in brain activity in such contrasts. The most important differences were found in the contrast of stimulus familiarity with chess positions. In this contrast, there was an extended brain activity in bilateral frontal areas such as the anterior cingulate and the superior, middle, and inferior frontal gyri; furthermore, posterior areas, such as posterior cingulate and cerebellum, showed great bilateral activation. These results strengthen the hypothesis that when performing a domain-specific task, experts activate different brain systems from that of novices. The use of the experts-versus-novices paradigm in brain imaging contributes towards the search for brain systems involved in cognitive processes. 相似文献
999.
Spławiński J 《Science and engineering ethics》2005,11(1):71-74
In this presentation, principles of ethics are confronted with the desire of the inventor to make a profit. To this end the
presentation is focused on patent protection. Patents should guarantee the return of an inventor’s investment and profit and,
on the other side, ensure availability — by patent disclosure — of the invention for the society when the patent terminates.
Recent patent applications made by inventors are infringing this principle and societies are paying an unexpected price for
these practices. Patent claims are too broad and disclosures too poor. Extreme examples will be discussed.
An earlier version of this paper was presented at an international conference, “The Ethics of Intellectual Property Rights
and Patents,” held in Warsaw, Poland on 23–24 April, 2004. 相似文献
1000.
Infants' sensitivity to social contingencies was assessed. In Study 1, 1-month-old infants and their mothers interacted face-to-face in three types of imperfect contingent interactions: Normal, Non-Contingent and Imitation. One-month-old infants did not discriminate these conditions. In Study 2, 3-month-old infants were tested as in Study 1. At 3 months of age, infants gazed reliably longer in the Imitation condition and smiled reliably more in the Normal than in the Non-Contingent and Imitation interactions. These findings suggest a developmental transition in the sensitivity to social contingencies between 1 and 3 months of age. The relationship between the developing sensitivity to social contingencies and social cognition is discussed. 相似文献