全文获取类型
收费全文 | 32692篇 |
免费 | 1329篇 |
国内免费 | 8篇 |
专业分类
34029篇 |
出版年
2019年 | 428篇 |
2018年 | 559篇 |
2017年 | 586篇 |
2016年 | 584篇 |
2015年 | 418篇 |
2014年 | 529篇 |
2013年 | 2372篇 |
2012年 | 972篇 |
2011年 | 1037篇 |
2010年 | 610篇 |
2009年 | 606篇 |
2008年 | 897篇 |
2007年 | 878篇 |
2006年 | 830篇 |
2005年 | 746篇 |
2004年 | 729篇 |
2003年 | 658篇 |
2002年 | 692篇 |
2001年 | 1018篇 |
2000年 | 928篇 |
1999年 | 710篇 |
1998年 | 381篇 |
1997年 | 309篇 |
1996年 | 306篇 |
1992年 | 548篇 |
1991年 | 541篇 |
1990年 | 526篇 |
1989年 | 537篇 |
1988年 | 530篇 |
1987年 | 494篇 |
1986年 | 521篇 |
1985年 | 570篇 |
1984年 | 451篇 |
1983年 | 431篇 |
1982年 | 354篇 |
1981年 | 337篇 |
1979年 | 521篇 |
1978年 | 378篇 |
1977年 | 311篇 |
1976年 | 358篇 |
1975年 | 432篇 |
1974年 | 486篇 |
1973年 | 507篇 |
1972年 | 407篇 |
1971年 | 381篇 |
1970年 | 378篇 |
1969年 | 408篇 |
1968年 | 488篇 |
1967年 | 421篇 |
1966年 | 422篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
251.
Edmond A. Murphy Kenneth R. Berger Joseph E. Trojak E. Manuel Rosell 《Theoretical medicine and bioethics》1989,10(4):355-365
Some properties are discussed of regular polygons that may result from angular homeostatic processes in stable orbit. To characterize these homeostatic polygons we need to discuss the winding number, the sidedness (integer, fractional and irrational), multiplicity, envelopes, and density. A regular (i.e., equilateral, equiangular) polygon may be closed in one revolution about its unique center, in multiple revolutions, or not at all. A homeostatic polygon can be generated only if all vertices are included in a single polygon, which occurs if and only if the number of vertices and the number of revolutions required to complete the polygon are relatively prime. For the homeostatic polygon to have a finite number of sides (without repeating itself) the angle subtended by any two successive vertices at the center must be a rational multiple of 2. Biological implications of these properties are illustrated. 相似文献
252.
Deborah E. Bender 《Theoretical medicine and bioethics》1989,10(3):239-249
The challenge of excellence in community health services has been taken up by medical educators in Colombia. Confronted with a nation where the primary indicators of disease mortality and morbidity (cardiovascular disease and infant mortality) were characteristic of First and Third World patterns, respectively, the Ministry of Health and La Asociacion Colombiana de Facultades de Medicina (ASCOFAME), representatives of institutions of medical education, have collaborated to conduct a needs assessment of the country's health needs and devised an implementation plan designed to better address the needs of the majority of that nation's people.As a model, the Colombian reorganization of medical education is an example which could be emulated by the U.S. where policy makers are struggling with troublesome questions of cost, equity and quality. 相似文献
253.
Patricia J. Krantz Steven E. Rams Land Lynn E. McClannahan 《Behavioral Interventions》1989,4(3):171-189
In this study, an autistic youth served as peer prompter for three other autistic adolescents. The peer prompter encouraged the other boys to talk about sports, a topic frequently discussed by typical teenagers. A multiple-baseline design across participants was used to assess the effectiveness of the peer-prompting procedure. During baseline, the youth rarely talked about sports, although all three had previously completed a sports-appreciation class and had displayed large pre-to-post gains on a paper-and-pencil test. During intervention, when a peer prompted sports discussions, all three youth engaged in much more sports-related conversation. Generalization measures indicated that: (1) the youth engaged in sports discussions in groups, as well as in the dyads that characterized the training situation; (2) they talked about sports in a setting other than the training setting; (3) they discussed sports with their peers when an unfamiliar teacher was present; and (4) they continued to discuss sports when training tapes and behavioral contracts between the teacher and the peer prompter were withdrawn. Previously, it has been common to use nonhandicapped or less-handicapped peers as tutors; this study demonstrates that an autistic youth may also effectively serve as a prompter who assists his schoolmates in acquiring conversational skills that contribute to their normalization. 相似文献
254.
Annabel J. Cohen Sandra E. Trehub Leigh A. Thorpe 《Attention, perception & psychophysics》1989,46(1):18-28
In three experiments, musically trained and untrained adults listened to three repetitions of a 5-note melodic sequence followed by a final melody with either the same tune as those preceding it or differing in one position by one semitone. In Experiment 1, ability to recognize the final sequence was examined as a function of redundancy at the levels of musical structurein a sequence, contour complexity of transpositions in a trial, and trial context in a session. Within a sequence, tones were related as the major or augmented triad; within a trial, the four sequences began on successively higher notes (simple macrocontour) or on randomly selected notes (complex macrocontour); and within a session, trials were either blocked (all major or all augmented) or mixed (major and augmented randomly selected). Performance was superior for major melodies, for systematic transpositions within a trial (simple macrocontours), for blocked trials, and for musically trained listeners. In Experiment 2, we examined further the effect of macrocontour. Performance on simple macrocontours exceeded that on complex, and excluded the possibility that repetition of the 20-note sequences provided the entire benefit of systematic transposition in Experiment 1. The effect of musical structure (major/augmented) was also replicated. In Experiment 3, listeners provided structure ratings of ascending 20-note sequences fromExperiment 2. Ratings onsame trials were higher than those on correspondingdifferent trials, in contrast to performance scores for augmentedsame anddifferent trials in previous experiments. The concept of functional uncertainty was proposed to account for recognition difficulties on augmented same trials. The significant effects of redundancy on all the levels examined confirm the utility of the information-processing framework for thestudy of melodic sequence perception. 相似文献
255.
A frequent complaint of depressed people concerns their poor interpersonal relationships. Yet, although nonverbal cues are considered of primary importance in interpersonal communication, the major theories of depression focus little attention on nonverbal social perception. The present study investigated the ability of depressed, disturbed control, and normal American adults to make rapid discriminations of facial emotion. We predicted and found that depressed subjects were slower than normal subjects in facial emotion discrimination but were not slower in word category discrimination. These findings suggest that current theories of depression may need to address difficulties with nonverbal information processing. There were also no significant differences between depressed and disturbed control subjects, suggesting that the unique social-behavioral consequences of depression have yet to be identified. 相似文献
256.
S Kreitler E Zigler H Kreitler 《Genetic, social, and general psychology monographs》1989,115(4):505-533
This study focused on the relations between performance on a three-choice probability-learning task and conceptions of probability as outlined by Piaget concerning mixture, normal distribution, random selection, odds estimation, and permutations. The probability-learning task and four Piagetian tasks were administered randomly to 100 male and 100 female, middle SES, average IQ children in three age groups (5 to 6, 8 to 9, and 11 to 12 years old) from different schools. Half the children were from Middle Eastern backgrounds, and half were from European or American backgrounds. As predicted, developmental level of probability thinking was related to performance on the probability-learning task. The more advanced the child's probability thinking, the higher his or her level of maximization and hypothesis formulation and testing and the lower his or her level of systematically patterned responses. The results suggest that the probability-learning and Piagetian tasks assess similar cognitive skills and that performance on the probability-learning task reflects a variety of probability concepts. 相似文献
257.
A controlled comparative investigation of psychological treatments for chronic sleep-onset insomnia 总被引:4,自引:1,他引:3
A sample of physician-referred chronic insomniacs was randomly allocated to either progressive relaxation, stimulus control, paradoxical intention, placebo or no treatment conditions. Treatment process and outcome were investigated in terms of mean and standard deviation (night to night variability) measures of sleep pattern and sleep quality. Only active treatments were associated with significant improvement, but the nature of treatment gains varied. In particular, stimulus control improved sleep pattern, whereas relaxation affected perception of sleep quality. All improvements were maintained at 17 month follow-up. Results are discussed with reference to previous research and guidelines are given for clinical practice. 相似文献
258.
The theme of this paper is the well-known resistance of adolescents to participate in analytic treatment and analysts' reservations about treating adolescents, which is perhaps less well known. Several reasons are discussed: For adolescents, the revival of separational and fusional anxieties during the process of individuation as well as resistance to the analytic setting are held responsible; analysts may lack sufficient awareness of their own adolescence and its resulting anxieties to be able to confront this developmental period. In addition, there are countertransference anxieties that are triggered and kept alive by the behavior of the juvenile patient. The different types of analyst anxieties as well as those of the adolescent under analysis are explained and their significance in the process of individuation and the course of therapy is noted. 相似文献
259.
A E Kazdin 《The American psychologist》1989,44(2):180-187
Developmental psychopathology refers to the study of clinical dysfunction in the context of maturational and developmental processes. Although the field encompasses the entire life span, the present focus is on childhood. Special characteristics make the study of childhood dysfunction somewhat unique, including the emergence, evolution, and attenuation of seemingly problematic behaviors over the course of development; the manner in which children are referred for clinical evaluation; and complexities in identifying the appropriate foci for clinical intervention. Notwithstanding these obstacles, recent work has advanced considerably in diagnosis, assessment, and treatment of childhood disorders. The present article highlights recent advances in these areas and promising extensions in current research. Many advances have relied heavily on the extension of paradigms developed in research with adults. Additional research is needed that draws on and integrates conceptual and empirical work from developmental psychology. 相似文献
260.
Emotions and emotional communication in infants 总被引:8,自引:0,他引:8
E Z Tronick 《The American psychologist》1989,44(2):112-119
Important advances have recently been made in studying emotions in infants and the nature of emotional communication between infants and adults. Infant emotions and emotional communications are far more organized than previously thought. Infants display a variety of discrete affective expressions that are appropriate to the nature of events and their context. They also appreciate the emotional meaning of the affective displays of caretakers. The emotional expressions of the infant and the caretaker function to allow them to mutually regulate their interactions. Indeed, it appears that a major determinant of children's development is related to the operation of this communication system. Positive development may be associated with the experience of coordinated interactions characterized by frequent reparations of interactive errors and the transformation of negative affect into positive affect, whereas negative development appears to be associated with sustained periods of interactive failure and negative affect. 相似文献