全文获取类型
收费全文 | 54583篇 |
免费 | 2149篇 |
国内免费 | 15篇 |
出版年
2019年 | 627篇 |
2018年 | 858篇 |
2017年 | 910篇 |
2016年 | 912篇 |
2015年 | 655篇 |
2014年 | 839篇 |
2013年 | 4005篇 |
2012年 | 1490篇 |
2011年 | 1585篇 |
2010年 | 1002篇 |
2009年 | 951篇 |
2008年 | 1449篇 |
2007年 | 1374篇 |
2006年 | 1305篇 |
2005年 | 1147篇 |
2004年 | 1160篇 |
2003年 | 1080篇 |
2002年 | 1129篇 |
2001年 | 1549篇 |
2000年 | 1468篇 |
1999年 | 1144篇 |
1998年 | 611篇 |
1997年 | 562篇 |
1996年 | 553篇 |
1992年 | 980篇 |
1991年 | 940篇 |
1990年 | 912篇 |
1989年 | 906篇 |
1988年 | 914篇 |
1987年 | 853篇 |
1986年 | 913篇 |
1985年 | 951篇 |
1984年 | 779篇 |
1983年 | 718篇 |
1982年 | 577篇 |
1981年 | 574篇 |
1979年 | 889篇 |
1978年 | 669篇 |
1977年 | 571篇 |
1976年 | 617篇 |
1975年 | 729篇 |
1974年 | 859篇 |
1973年 | 917篇 |
1972年 | 709篇 |
1971年 | 700篇 |
1970年 | 681篇 |
1969年 | 715篇 |
1968年 | 861篇 |
1967年 | 768篇 |
1966年 | 777篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
211.
This study was designed to evaluate the possibility that a pattern of cognitive deficit is associated with delinquent behavior, while avoiding some of the methodological problems of previous research. The Self- Report Early Delinquency instrument and a research battery of neuropsychological tests were administered blindly to an unselected cohort of 678 13- year- olds. Because the diagnosis of attention deficit disorder (ADD) was found at markedly elevated rates in the backgrounds of these delinquents, the possibility was examined that the neuropsychological deficits of delinquents might be limited to delinquents with histories of ADD. Although delinquents with past ADD were more cognitively impaired than non-ADD delinquents, both groups scored significantly below nondelinquents on verbal, visuospatial, and visualmotor integration skills. In addition, ADD delinquents scored poorly on memory abilities. Subjects with ADD who had not developed delinquent behavior were not as cognitively impaired as ADD delinquents, suggesting that it is the specific comorbidity of ADD and delinquency that bears neuropsychological study.This work was supported by USPHS Grant 1 R23 MH-42723-01 from the Antisocial and Violent Behavior Branch of the National Institute of Mental Health. The Dunedin Multidisciplinary Health and Development Research Unit is supported by the Medical Research Council of New Zealand. Appreciation is expressed for the methodological advice of Prof. Sarnoff A. Mednick, and for the data collection efforts of Mrs. Pat Brasch, Mrs. Kathleen Campbell, Mr. Rich Poulton, and the psychometrists who administered the WISC-R. 相似文献
212.
Cyd C. Strauss Cynthia G. Last Michel Hersen Alan E. Kazdin 《Journal of abnormal child psychology》1988,16(1):57-68
The relationship between anxiety and depression was examined in a sample of 106 children and adolescents referred to an outpatient anxiety disorder clinic for children. Twenty-eight percent of patients with DSM-III diagnoses of anxiety disorders displayed a concurrent major depression. Children with anxiety disorders plus major depression were found (1) to be older, (2) to demonstrate more severe anxiety symptomatology, and (3) to be diagnosed with different rates of certain anxiety-disorder subtypes, when compared to anxious patients without major depression. Nondepressed anxious children and adolescents did not differ from a psychopathological control group in severity of either anxiety or depression symptoms. 相似文献
213.
214.
The modulation of attacks, genital sniffs, and mounts in male SJL/J mice by ovarian-dependent urogenital substances in the urine voided by estrous females was examined. Urogenital substances were applied onto the external urogenital areas of ovariectomized mice. When compared with urine voided by estrous females, which stimulated genital sniffing, mounting, and reduced aggression, bladder urine was ineffective. Genital sniffing and mounting was stimulated by estradiol-17 beta, vaginal fluids, and preputial extract. Aggression was reduced by estradiol-17 beta, urethral catheterized urine, and vaginal fluids. Preputialectomy reduced, but did not eliminate, urinary stimulation of genital sniffing and mounting. Preputial extract stimulated aggression. Urogenital substances from ovariectomized females were ineffective in reducing attacks and stimulating genital sniffs and mounts. It was concluded that the ovarian-dependent chemosignals in the urine voided by estrous females are contributed by the urethra, vagina, and preputial gland, perhaps in part through the excretion of unconjugated estrogens. 相似文献
215.
Serotonergic and opiate interactions in the modulation of drug- and environmental-induced analgesia were assessed in 6-day-old Sprague-Dawley-derived rat pups using tail-flick testing procedures. In these experiments the serotonergic antagonist metergoline was observed to attenuate both the analgesia induced by the opiate agonist morphine and the analgesia induced by isolation from siblings and the dam, an environmental manipulation which has previously been shown to be associated with increases in opiate activity. In contrast, the opiate antagonist naloxone was observed to be ineffective in blocking not only analgesia induced by the serotonergic agonist quipazine, but also analgesia induced by long-term deprivation from the dam and food, a manipulation that has been previously reported to induce increases in serotonergic utilization. These results suggest that in the neonate, as in the adult, the serotonergic modulation of nociception appears to occur "downstream" from the opiate systems serving to regulate nociception following both drug- and environmental-induced alterations in pain sensitivity. Analgesia induced by long-term deprivation from food and the dam appears to be strongly related to increases in serotonergic activity and relatively unaffected by opiate antagonism, whereas analgesia induced by isolation from siblings and the dam may be related to increases in opiate activity, but modulated by serotonergic systems serving to regulate pain responsivity. Thus alterations in the environment, mediated at least in part by alterations in opiate and serotonergic activity, appear to play an important role in influencing the sensitivity of the neonate to pain stimuli. 相似文献
216.
The ability of right-brain-damaged (RBD) subjects to correctly insert a word into a well-formed stimulus sentence was tested. Subjects also performed three evaluative tasks designed to establish their degree of general cognitive impairment. The performance of RBD subjects on these tasks was compared to that of left-brain-damaged (LBD) and non-brain-damaged (NBD) subjects. Although RBD subjects outperformed LBD subjects on the language-related evaluative tasks, the RBD group was significantly more impaired on a subset of the insertion task. This subset included items which required reassignment of the syntactic status of elements in the stimulus sentence in order for the insertion to be carried out. The results of this study permit refinement of the common characterization of RBD individuals as rigid in their interpretation of meaning and indicate right-hemisphere involvement in aspects of the grammar previously thought to be inaccessible to it. 相似文献
217.
Knowledge and beliefs regarding the consequences of cigarette smoking and their relationships to smoking status in a biracial sample 总被引:3,自引:0,他引:3
R C Klesges G Somes R W Pascale L M Klesges M Murphy K Brown E Williams 《Health psychology》1988,7(5):387-401
The purpose of this investigation was to evaluate carefully smoking-related knowledge and beliefs and their relationships to smoking status in a large, heterogeneous sample of smokers and nonsmokers in two settings: (a) a large, biracial southern city and (b) a small midwestern community. Participants were 611 (198 male, 413 female) adult respondents to a random-dialing telephone survey in Fargo, North Dakota (n = 200), and Memphis, Tennessee (n = 411). Each participant was given the Smoking Attitudes Survey, which assesses generalized health beliefs as well as health-related problems associated with smoking. Participants' knowledge of smoking-associated diseases (e.g., lung cancer) and of diseases not associated with smoking (e.g., kidney stones) was assessed. Stepwise regression analysis of composite knowledge scores revealed four independent predictors of the health consequences of smoking: education, race, smoking status, and income. Smokers, compared to nonsmokers, reported less knowledge related to the health consequences of smoking, were more likely to be male, were less concerned with the health consequences of smoking, and were more concerned about the health consequences of cholesterol. The best predictor of smokers who had never attempted cessation was their greater concern over weight control when compared to smokers with a history of smoking cessation attempts. The results are discussed in terms of smoking prevention and intervention efforts. 相似文献
218.
The vocationally-indecisive individual presents a major counselling problem. The theory and research behind career indecision is discussed and a counselling approach based on identity formation is outlined. Four identity statuses — Identity Achievements, Foreclosures, Identity Diffusions, and Moratoriums — are described and counselling approaches for each are explored. 相似文献
219.
J E Mazur 《Journal of the experimental analysis of behavior》1988,49(1):37-47
In a series of conditions, pigeons chose between 1.5 s and 3 s of access to grain, each preceded by some delay. The delay that preceded the small reinforcer was constant throughout a condition. The delay that preceded the large reinforcer was increased or decreased a number of times each session in order to estimate an "indifference point," a delay at which the subject chose each alternative about equally often. The experiment was designed to determine whether variations in any of four features of this adjusting-delay procedure would systematically alter the estimated indifference points. The four features were the total trial duration, the number of center-key responses necessary to begin a trial, the number of choice trials that preceded each change in the adjusting delay, and step size--the size of each increment and decrement in the delay. Manipulation of the first three features had no systematic effects on the indifference points. As step size was increased from 0.5 s to 6 s, within-session variability of the adjusting delay steadily increased, and the 6-s step size produced larger indifference-point estimates for some subjects. The results suggest that, within certain limits, these procedural features can be altered without affecting the indifference-point estimates, but that the use of a large step size can distort the estimates. Some theoretical implications of the relative constancy of indifference points across these procedural variations are discussed. 相似文献
220.
Self-control in mentally retarded adolescents: choice as a function of amount and delay of reinforcement.
下载免费PDF全文
![点击此处可从《Journal of the experimental analysis of behavior》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Three severely mentally retarded adolescents were studied under discrete-trial procedures in which a choice was arranged between edible reinforcers that differed in magnitude and, in some conditions, delay. In the absence of delays the larger reinforcer was consistently chosen. Under conditions in which the smaller reinforcer was not delayed, increasing the delay to delivery of the larger reinforcer decreased the percentage of trials in which that reinforcer was chosen. All subjects directed the majority of choice responses to the smaller reinforcer when the larger reinforcer was sufficiently delayed, although the value at which this occurred differed across subjects. Under conditions in which the larger reinforcer initially was sufficiently delayed to result in preference for the smaller one, progressively increasing in 5-s increments the delay to both reinforcers increased percentage of trials with the larger reinforcer chosen. At sufficiently long delays, 2 of the subjects consistently chose the larger, but more delayed, reinforcer, and the 3rd subject chose that reinforcer on half of the trials. These results are consistent with the findings of prior studies in which adult humans responded to terminate noise and pigeons responded to produce food. 相似文献