全文获取类型
收费全文 | 45464篇 |
免费 | 1004篇 |
国内免费 | 9篇 |
专业分类
46477篇 |
出版年
2020年 | 270篇 |
2019年 | 307篇 |
2018年 | 3773篇 |
2017年 | 3112篇 |
2016年 | 2646篇 |
2015年 | 545篇 |
2014年 | 525篇 |
2013年 | 2276篇 |
2012年 | 1346篇 |
2011年 | 3079篇 |
2010年 | 2945篇 |
2009年 | 1931篇 |
2008年 | 2370篇 |
2007年 | 2866篇 |
2006年 | 776篇 |
2005年 | 892篇 |
2004年 | 783篇 |
2003年 | 718篇 |
2002年 | 690篇 |
2001年 | 857篇 |
2000年 | 882篇 |
1999年 | 623篇 |
1998年 | 357篇 |
1997年 | 334篇 |
1996年 | 323篇 |
1995年 | 283篇 |
1994年 | 286篇 |
1992年 | 498篇 |
1991年 | 473篇 |
1990年 | 474篇 |
1989年 | 416篇 |
1988年 | 401篇 |
1987年 | 404篇 |
1986年 | 379篇 |
1985年 | 391篇 |
1984年 | 380篇 |
1983年 | 355篇 |
1982年 | 324篇 |
1981年 | 285篇 |
1980年 | 268篇 |
1979年 | 338篇 |
1978年 | 334篇 |
1977年 | 300篇 |
1976年 | 270篇 |
1975年 | 330篇 |
1974年 | 374篇 |
1973年 | 364篇 |
1972年 | 288篇 |
1971年 | 250篇 |
1968年 | 281篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Practice in front of a mirror is a common procedure for activities such as dance, gymnastics, and other sports. The purpose of this study was to examine the effect that performing with concurrent visual feedback from a mirror had on the acquisition of the power clean movement. 18 college-age males who had no prior experience with the power clean movement served as subjects who were assigned to one of two groups. One group had use of a mirror during the practice trials and the other practiced without the mirror. All subjects viewed an instructional videotape and had practice trials. All subjects were evaluated for proper technique on a pretest, a posttest without the mirror, and a posttest with the mirror. Analysis showed a significant difference between pre- and posttest performances for both groups and a significant difference between groups on the posttest performances with the mirror. Evidently the videotaped instruction was sufficient to allow both groups to improve in performance of the power clean. Differences in posttest performances with the mirror reflected the type of feedback (with or without the mirror) available during training. 相似文献
72.
73.
Ratings of pre-morbid intelligence level, derived from the hospital charts of 26 chronic schizophrenics, were correlated with the post-mortem brain volume measures of cortex, white matter, central grey matter, and ventricles. Contrary to hypothesis, no significant correlations were found. 相似文献
74.
T L Stawar 《Perceptual and motor skills》1988,67(3):960-962
The IES Arrow-Dot was administered to 41 cocaine detoxification patients. This group's scores indicated lower ego functioning and higher impulsivity and superego functioning than other clinical samples. No significant differences were noted between the Arrow-Dot scores of patients who successfully completed the program and those who did not. 相似文献
75.
Sprague-Dawley rats drank sweetened (3% dextrose + 0.144% saccharin, w/v) or unflavored water for 18 days and subsequent pain reactivity was assessed using a hot plate. Compared to the rats that consumed unflavored water, the rats that consumed sweet water responded more quickly on the hot plate indicating that their threshold for pain was lowered. Another group of rats given identical exposure to the fluids had their brains prepared for measuring opiate receptor binding using the delta-receptor ligand [3H]D-Ala-D-Leu-enkephalin ([3H]DADLE) and the mu-receptor selective ligand [3H]Tyr-D-Ala-Gly-MePhe-Gly-ol ([ 3H]DAGO). Binding of these opiates to mu- and delta-receptors in the cerebral cortex, striatum, hippocampus, hypothalamus, brain stem, and remaining brain regions was the same for the rats that drank sweet fluids and those that drank unflavored water. These findings suggest that drinking sweet fluids lowers pain thresholds but does not alter mu- and delta-receptors. 相似文献
76.
The influence of affect on causal attributions for success and failure was examined in this experiment. A positive, neurtral, or negative mood was induced in subjects who then learned they had either succeeded or failed an aptitude test taken previously. Relative to neutral mood control conditions, subjects in both positive and negative mood conditions showed a pronounced self-serving bias, particularly following success. The finding is interpreted as self-regulation of affective state. Specifically, causal attribution of success to internal factors can sustain or enhance positive affect; attribution of failure to external factors can diminish negative affect. Ancillary analyses corroborated this interpretation. 相似文献
77.
78.
We investigated longitudinally the effects of a stroke on the social support systems and well-being of the patient's primary support person, both acutely and as the condition stabilized. Individuals who had suffered a first stroke and a primary support person participated in two waves of data collection, carried out in 6-month intervals beginning 7 weeks after the stroke. Our data show that the prevalence of depressive symptoms is from 2 1/2 to 3 1/2 times higher than rates found among representative samples of middle-aged and elderly populations. Mean level of depression did not change over time, although level of optimism declined significantly. Multiple regression analyses showed that levels of depression and perceived burden in support persons are highly related to aspects of the stroke such as its severity, and that demographic variables such as age and income play a relatively minor role in attenuating these relations in the acute adjustment phase. However, from 7 to 9 months after the stroke, well-established demographic variables such as health, income, and age were significant predictors of depression. Individuals who were older and who had good health and higher incomes were least depressed. 相似文献
79.
Increasing similarity in the values and life plans of male and female college students? Evidence and implications 总被引:2,自引:0,他引:2
Robert Fiorentine 《Sex roles》1988,18(3-4):143-158
A time-series analysis of college freshmen indicates that from 1969 to 1984 there has been a dramatic increase in the value women place on status-attainment goals, but not a comparable decrease in the value placed on domestic-nurturant goals—a pattern that reflects an amalgamation rather than a masculinization of the feminine value constellation. As the value placed on status-attainment goals has not increased as significantly for males, there has been a narrowing of the difference in the value constellations of the sexes over this time period. Further, there has been a greater increase in the percentage of women than men aspiring to graduate degrees and to the highest status professional and executive occupations, resulting in increased congruence in the educational and high-status career goals of women and men. The limitations and implications of these data are discussed.The research for this paper was funded by a grant from the Josiah Macy Jr. Foundation. I thank Andrea Tyree and Norman Goodman for reading and commenting on earlier drafts of this paper. I particularly thank Stephen Cole for his incisive comments. 相似文献
80.
High-resolution CRT displays are subject togeometric distortion: lines that are straight in the internal coordinates of the graphics software and hardware are curved when projected onto a plane in the observer’s line of sight. As the available resolution of CRT screens increases, it becomes more difficult to measure and correct for this distortion. We present a simple, highly accurate method for determining the mapping between internal coordinates and the viewing plane. It requires that an observer, using a calibration program, adjust triples of displayed points until they are collinear. A metal straightedge placed between the observer and the screen aids in this judgment. We describe the calibration of an IBM Enhanced Graphics Display in high-resolution mode (350 × 640 pixels), and illustrate how to use the estimated mapping to choose internal coordinates to draw undistorted figures that are accurate to within 0.5 pixel. The method can be used to assess or to correct the accuracy of visual displays. The method is relevant to experiments in spatial vision, spatial perception, perception of dot patterns, and any application in which geometrically accurate stimuli are required. 相似文献