全文获取类型
收费全文 | 102999篇 |
免费 | 4253篇 |
国内免费 | 38篇 |
出版年
2020年 | 1107篇 |
2019年 | 1369篇 |
2018年 | 1897篇 |
2017年 | 1960篇 |
2016年 | 2061篇 |
2015年 | 1483篇 |
2014年 | 1764篇 |
2013年 | 8371篇 |
2012年 | 3292篇 |
2011年 | 3416篇 |
2010年 | 2107篇 |
2009年 | 2125篇 |
2008年 | 2983篇 |
2007年 | 2988篇 |
2006年 | 2741篇 |
2005年 | 2379篇 |
2004年 | 2290篇 |
2003年 | 2179篇 |
2002年 | 2218篇 |
2001年 | 3295篇 |
2000年 | 3154篇 |
1999年 | 2385篇 |
1998年 | 1179篇 |
1997年 | 1048篇 |
1996年 | 1082篇 |
1995年 | 988篇 |
1993年 | 970篇 |
1992年 | 2000篇 |
1991年 | 1875篇 |
1990年 | 1888篇 |
1989年 | 1734篇 |
1988年 | 1689篇 |
1987年 | 1608篇 |
1986年 | 1650篇 |
1985年 | 1706篇 |
1984年 | 1445篇 |
1983年 | 1291篇 |
1981年 | 947篇 |
1979年 | 1520篇 |
1978年 | 1113篇 |
1975年 | 1222篇 |
1974年 | 1358篇 |
1973年 | 1466篇 |
1972年 | 1218篇 |
1971年 | 1146篇 |
1970年 | 1023篇 |
1969年 | 1041篇 |
1968年 | 1306篇 |
1967年 | 1176篇 |
1966年 | 1059篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Age, exercise, and coding performance 总被引:1,自引:0,他引:1
We investigated the effects of exercise on the coding performance of young and older subjects. Hypotheses were tested that exercise either facilitates spatial localization or reduces susceptibility to distraction in older subjects. In a balanced design, we administered Digit Symbol and Symbol Digit coding tasks to exercisers and nonexercisers at two age levels under conditions of low or high within-task interference. The findings showed higher performance by the exercisers than by the nonexercisers only at the older age level and only with the Symbol Digit task. These findings support the hypothesis that exercise compensates for a loss of spatial localization skills with age. We found no evidence that susceptibility to distraction either increased with age or was affected by chronic exercise. 相似文献
992.
This study compared the temporal organization of graphic movements executed either actually or mentally. Six subjects had to perform two tasks, writing a sentence and drawing a cube, either as a real performance or as an imagined one, with either the right or the left hand, and with either a small or a large tracing amplitude. In the same subject, for the same hand, mental and actual movement times were both very stable and very close from trial to trial regardless of the tracing amplitude. Thus, mental movements mimic closely real movements in their temporal organization and are likely to involve the same planning program. 相似文献
993.
The Sentencing Reform Act of 1984, which created the U.S. Sentencing Commission, required that the commisson consider prison capacity in drafting sentencing guidelines. As part of the commission's efforts to meet this requirement, we developed a computer simulation capable of projecting the impact of the commission's guidelines on future sentences and prison populations. According to our projections, “straight” probation sentences will be reduced significantly under the guidelines. However, reducing the use of probation will generate only modest demands on the prisons, and then mostly for community corrections phased in over the course of 5 years. We also project that, while average time served for violent offenses will increase substantially, average time served for most property crimes will remain largely the same. Finally, while we forecast that federal prison populations will grow markedly by the end of this century, this is more a result of the Anti-Drug Abuse Act of 1986 and the career offender provision of the Comprehensive Crime Control Act of 1984 than a result of the guidelines. 相似文献
994.
M T Phelps W A Roberts 《Journal of comparative psychology (Washington, D.C. : 1983)》1989,103(4):326-338
We studied central-place foraging in rats (Rattus norvegicus) by placing food items that varied in size and weight at the ends of a 4-arm radial maze. In Experiments 1-3, rats increasingly tended to carry food to the center of the maze as the size of those items increased. Very large food items often were hoarded in the center. Rats consumed food faster on the arms than in the center, and rats traveled faster when carrying food than when not. Blocking arm entrances increased travel time between the center and the arms and decreased food carrying at every item weight except the largest. In Experiments 4-6, important conditions that influence the degree of food-carrying behavior were discovered; these were the intersection of maze arms, the presence of a conspecific, and the use of open vs. closed maze arms. 相似文献
995.
KATHLEEN McNAMARA KATHRYN M. RICKARD 《Journal of counseling and development : JCD》1989,68(2):184-189
This article discusses the implications of the Downing and Roush (1985) model of feminist identity development for feminist therapy with women. Following a summary of the model, the potential pitfalls of feminist therapy with the passive-acceptant client are described, as well as potential issues at subsequent stages of the client's identity development. Suggestions are made regarding how to facilitate clients' movement to higher levels of development. Finally, a research agenda is proposed that suggests hypotheses to be tested that arise from applying this model to conducting therapy with women. 相似文献
996.
J M Stern S K Johnson 《Journal of comparative psychology (Washington, D.C. : 1983)》1989,103(3):269-280
Prior to assuming the upright crouching posture over their pups during nursing bouts, lactating rats typically engage in several oral behaviors, including nuzzling, licking and rearranging pups. By acutely depriving dams of various aspects of perioral stimulation from pups (with anesthesia of the mystacial pads or of the tongue, with mouth suturing, or with muzzling), we found the following: (1) Distal stimulation from pups maintains proximity-seeking behavior, but is insufficient to stimulate nursing behavior. (2) Lack of tongue feedback decreases pup licking and hastens the onset of crouching. (3) Snout, but not tongue, contact with pups is required for hovering over them. (4) The position of the dam while hovering over her litter enables the pups to gain access to her ventrum, thereby provoking her upright, crouching posture. (5) Older pups are capable of bypassing the dam's perioral attentions and stimulating crouching directly by burrowing under the dam's ventrum. 相似文献
997.
998.
Relationship of racial stressors to blood pressure responses and anger expression in black college students 总被引:5,自引:0,他引:5
The physiological effects of racism, as a stressor, were examined as they related to blood pressure (BP) and anger experiences in Black college students. Current research has failed to consider the stressful effects of racism as a factor contributing to the higher incidence of essential hypertension among Blacks. Twenty-seven Black college students viewed three excerpts showing racist situations involving Blacks; anger-provoking, nonracist situations; and neutral situations. After each scene, BP was taken, and a mood checklist was administered. The Framingham Anger Scale and the Anger Expression Scale were administered. Analyses revealed that BP significantly increased during the presentation of racist stimuli but not of anger-provoking or neutral stimuli. Self-reports of state anger, as measured by the mood checklist, were significant for both the anger-provoking and racist stimuli. BP scores were significantly correlated to the two trait anger measures. Exposure to racist stimuli was associated with BP increases among Blacks. Such cumulative exposure to racism may have important implications for the etiology of essential hypertension. 相似文献
999.
A cross-sex difference on one variable is often hypothesized to be related to a gender difference on a second variable. However, caution should be exercised in making such comparative hypotheses. We gathered the expected and actual examination grades for 168 female and 163 male college students. As in prior research, males had higher expectancies than females (p<.05). But analysis of the intrasex regression equations indicated that the relationship of expectancies to performance was different for women than it was for men. Thus, a cross-sex difference in expectancies did not correspond to a parallel difference in grades. This finding highlights the potential hazards of making certain cross-sex comparisons, and we argue for more caution in their application. 相似文献
1000.