全文获取类型
收费全文 | 68703篇 |
免费 | 2041篇 |
国内免费 | 22篇 |
专业分类
70766篇 |
出版年
2020年 | 564篇 |
2019年 | 656篇 |
2018年 | 4140篇 |
2017年 | 3457篇 |
2016年 | 3080篇 |
2015年 | 893篇 |
2014年 | 924篇 |
2013年 | 3868篇 |
2012年 | 2106篇 |
2011年 | 3773篇 |
2010年 | 3389篇 |
2009年 | 2390篇 |
2008年 | 3022篇 |
2007年 | 3455篇 |
2006年 | 1280篇 |
2005年 | 1364篇 |
2004年 | 1313篇 |
2003年 | 1147篇 |
2002年 | 1118篇 |
2001年 | 1461篇 |
2000年 | 1446篇 |
1999年 | 1070篇 |
1998年 | 589篇 |
1997年 | 502篇 |
1992年 | 973篇 |
1991年 | 902篇 |
1990年 | 927篇 |
1989年 | 812篇 |
1988年 | 810篇 |
1987年 | 785篇 |
1986年 | 793篇 |
1985年 | 878篇 |
1984年 | 695篇 |
1983年 | 628篇 |
1982年 | 469篇 |
1981年 | 466篇 |
1979年 | 784篇 |
1978年 | 522篇 |
1977年 | 494篇 |
1976年 | 498篇 |
1975年 | 641篇 |
1974年 | 739篇 |
1973年 | 767篇 |
1972年 | 650篇 |
1971年 | 615篇 |
1970年 | 584篇 |
1969年 | 577篇 |
1968年 | 766篇 |
1967年 | 675篇 |
1966年 | 598篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
231.
This paper describes an amplifier for an electroencephalograph with gain of 1×104 to 1×106 and made entirely of commercially available IC components. The two-stage amplifier has a preamplifier stage with fixed gain of 1000, and a second stage with variable gain from 1 to 100. The final stage, an anti-aliasing filter, adds a gain of 10 to the signal. The circuit has high common mode rejection, low input bias current, very low noise characteristics, low offset voltages, and offset nulling capability built into the circuit. 相似文献
232.
A unique relationship exists between physicians and philosophers — one that expands on the constructive potential of the liaison between physicians and, for example, theologians, on the one hand, or, social workers on the other. This liaison should focus in the scientific aspects of medicine, not just the ethical aspects. Philosophers can provide physicians with a perspective on both the philosophy and the history of medicine through the ages — a sense of how medicine has adapted to the social cultural and ethical needs of each period. This perspective, while emphasizing medicine asscience, should not be limited to matters of methodology, or to criteria for distinguishing science from other intellectual pursuits, but should be concerned also with the history, sociology and politics of science. Both physicians and philosophers stand to gain from a strengthening of their active liaison now as never before; but most of all, the public will be the beneficiary. 相似文献
233.
Fear of Success (FOS) was originally conceived as a unidimensional motive. However, there is both theoretical and empirical
support for the hypothesis that FOS is multidimensional. We factor analyzed the responses of 236 undergraduates to twenty-oneConcern Over the Negative Consequences of Success items and found four factors. Our four factors show considerable overlap with dimensions based on theoretical accounts of
FOS etiology as well as with the factor structures obtained from two other factor analytic studies. Thus, there is converging
evidence that FOS is multidimensional. The relationship between multidimensional FOS and a multidimensional approach to achievement
motivation is discussed. 相似文献
234.
Thirty children and 5 adults participated in two experiments designed to compare visual processing in normal and reading disabled children. The children were aged 8, 10, and 12 years. In Experiment 1, subjects were asked to detect the temporal order of two briefly presented stimuli. In Experiment 2, subjects sorted cards containing bracket stimuli that did or did not produce perceptual grouping effects. Poor readers required more time to make accurate temporal order judgments and showed stronger perceptual grouping effects. For both good and poor readers, the amount of time necessary to make a correct temporal order judgment decreased, and perceptual grouping effects became weaker with age. However, the magnitude of the difference between the groups did not lessen with age. These results suggest that there are visual processing differences between good and poor readers that do not appear to correct by age 12. 相似文献
235.
Differences in school behavior and achievement between students from intact, reconstituted, and single-parent families were analyzed. Students from intact two-parent families had fewer absences and tardies, higher grade point averages, and fewer negative and more positive teacher behavioral ratings than did those from reconstituted and single-parent families. 相似文献
236.
To investigate the moderating role of individual differences in hypnotic susceptibility and visuospatial skills on afterimage persistence, we presented a codable (cross) flash of light to 40 men and 46 women who had been dark adapted for 20 min. In an unrelated classroom setting, subjects had previously been given two standardized scales of hypnotic susceptibility (Harvard Group Scale of Hypnotic Susceptibility, Shor & Orne, 1962; Group Stanford Hypnotic Susceptibility Scale, Form C, Crawford & Allen, 1982) and the Mental Rotations Test (Vandenberg & Kuse, 1978). The first afterimage interval and the afterimage duration correlated significantly with hypnotic responsiveness, supporting Wallace (1979), but did not show the anticipated relationships with mental rotation visuospatial skills. Individuals in the high hypnotizable group had (a) significantly longer afterimage intervals between its first appearance and first disappearance than did those in medium or low groups, as well as (b) significantly longer afterimages between the first appearance and the final disappearance than did those in low groups, but those in medium groups did not differ significantly from the other groups. Discriminant analysis using the afterimage persistence measures classified correctly 65.2% of high hypnotizables, 37.5% of medium hypnotizables, and 54.8% of low hypnotizables. Hypothesized cognitive skills that assist in the maintenance of afterimages and underlie hypnotic susceptibility include abilities to maintain focused attention and resist distractions over time and to maintain vivid visual images. 相似文献
237.
238.
This paper suggests that aspects of paranoid character are structured around fantasies of magical and concrete connectedness to objects; these fantasies serve to avoid the terrors of object inconstancy. The authors describe how these fantasies are expressed in the psychoanalytic situation and explore their relation to common paranoid phenomena. The paranoid person must maintain these fantasies of connectedness at all cost or risk experiencing unbearable indifference between self and object. Paradoxically, the sacrifice of self and object boundaries inherent in these fantasies makes object constancy even more difficult to achieve because of the secondary defensive use of anger mobilized to protect the boundaries of the self. 相似文献
239.
Our goal was to test whether current hemisphere predominance is a predictor of scores on standardized measures of personal optimism and preference for risk. In two between-subject experiments, current hemisphere predominance was measured by the direction and extent of line bisecting errors. Pearson correlations and median splits of the line bisecting errors showed significantly greater personal optimism and preference for risk with left hemisphere predominance. These results support previous research in which manipulation of hemisphere predominance produced similar effects on personal optimism in normal individuals and on risk taking in lesioned and normal samples. We conclude that the association of optimism and risk with left hemisphere predominance can be observed in resting as well as in manipulated situations. 相似文献
240.
Seventh-grade students and teachers from twenty-three middle and junior high schools were surveyed to determine the association between teacher attitudes, behavioral intentions, and smoking behavior and the prevalence of student smoking. Teacher attitudes toward smoking policies were found to be strongly related to the current smoking behavior of the teacher but not consistently related to student smoking. In addition, teacher likelihood of intervening showed a modest association with teacher smoking status, with current smokers generally indicating being the least likely to intervene for student possession or use of cigarettes. Teacher intentions to intervene were strongly associated with the prevalence of smoking among boys but not girls. 相似文献