全文获取类型
收费全文 | 25731篇 |
免费 | 847篇 |
国内免费 | 12篇 |
专业分类
26590篇 |
出版年
2019年 | 245篇 |
2018年 | 297篇 |
2017年 | 336篇 |
2016年 | 381篇 |
2015年 | 298篇 |
2014年 | 327篇 |
2013年 | 1833篇 |
2012年 | 629篇 |
2011年 | 643篇 |
2010年 | 406篇 |
2009年 | 421篇 |
2008年 | 600篇 |
2007年 | 542篇 |
2006年 | 482篇 |
2005年 | 477篇 |
2004年 | 443篇 |
2003年 | 448篇 |
2002年 | 465篇 |
2001年 | 686篇 |
2000年 | 674篇 |
1999年 | 469篇 |
1998年 | 244篇 |
1992年 | 467篇 |
1991年 | 452篇 |
1990年 | 457篇 |
1989年 | 458篇 |
1988年 | 408篇 |
1987年 | 420篇 |
1986年 | 445篇 |
1985年 | 481篇 |
1984年 | 410篇 |
1983年 | 376篇 |
1982年 | 271篇 |
1981年 | 314篇 |
1980年 | 243篇 |
1979年 | 439篇 |
1978年 | 317篇 |
1977年 | 286篇 |
1976年 | 274篇 |
1975年 | 409篇 |
1974年 | 459篇 |
1973年 | 484篇 |
1972年 | 410篇 |
1971年 | 403篇 |
1970年 | 378篇 |
1969年 | 401篇 |
1968年 | 493篇 |
1967年 | 476篇 |
1966年 | 453篇 |
1958年 | 252篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
Fred H. Previc 《Behavior research methods》1996,28(1):83-88
An automated bisection device (ABD) is described that is designed for use in assessing the direction of three-dimensional neglect in various clinical populations. This device features an apparatus containing two base sections and a connecting rod, on which is located a bisection indicator assemblage that can be moved either by hand or by a calibrated motor-drive system. The indicator assemblage is, in turn, connected to a motor-control box with variable speed settings and a digital readout. The ABD can be used to measure bisection estimations along all three linear axes (lateral, vertical, and depth) by providing visual cues alone, tactile cues alone, or a combination of visual and tactile cues. 相似文献
912.
The World-Wide Web provides an inviting opportunity to reach large numbers of people, both as an audience for psychoacoustical discussions and demonstrations and as subjects for psychoacoustical experiments. Such use of the Web poses a unique set of challenges. We present the methodologies used to prepare a multimedia primer in auditory perception at McGill University. As well as instructional material, this primer includes acoustical experiments conducted over the Web. We discuss the response and experiences with this site in general and in a particular class situation at Hanover College. 相似文献
913.
914.
A recent extension (Beach, & Tesser, 1993) of Tesser's self-evaluation maintenance model (SEM: Tesser, 1988) proposed that a person's motivation to feel good about the self, and his or her concern for the partner's need to feel good about the self, can affect the couple's interaction behavior. In the present study, individual differences in the motivation to maintain one's own and one's partner's SEM needs are used to predict the couple's problem-solving discussion behaviors. Fifty-three married couples were videotaped for 20 minutes while discussing an important relationship issue on which there was disagreement. From these video records, husbands' and wives' favorable and unfavorable discussion behaviors were coded. During a subsequent session, couples reported their affective reactions to a number of SEM scenarios recalled from memory, which were used to create an individual difference measure representing the strength in motivation to maintain one's own and one's partner's self-evaluation needs. In general, husbands' and wives' responsiveness to their partners' SEM needs was associated with favorable interaction behavior, whereas responsiveness to one's own SEM needs was associated with unfavorable interaction behavior. The results of this study suggest that the extended SEM model provides an experimental framework that incorporates research directed at both the elucidation of individual differences and the examination of the couple as a unit. 相似文献
915.
A case study of conflicting interests: Flemish engineers involved in environmental impact assessment
This article reports of the activities of the working group, Ethics & Engineers, of the Royal Flemish Society of Engineers.
More particularly, the ethical problems that engineers face in the preparation of an environmental report are illuminated.
Irrespective to which party the engineer belongs, he or she is confronted with the difficult weighting of his or her personal
interest, the interests of private companies and last but not least the common good. It is argued that the implementation
of a code of ethics and the introduction of courses on engineering ethics into the education of engineers would strengthen
the engineer in the fulfilment of his vocation.
Dirk Holemans is a bio-engineer preparing a doctoral thesis on the social responsibility of engineers, Herman Lodewyckx teaches
ethics and has research interests in professional and applied ethics. 相似文献
916.
Michael H. Mesches Marino Bianchin James L. McGaugh 《Neurobiology of learning and memory》1996,66(3):324-340
The aim of these experiments was to determine whether impaired retention performance in aversively motivated tasks, induced by blockade of amygdala AMPA receptors, is due to influences on mechanisms underlying memory retrieval or to other influences on performance. Rats received either footshock escape training (1 or 10 trials), or no foot shock, in a two-compartment straight alley and bilateral intra-amygdala infusions of the AMPA receptor antagonist CNQX (0.5 μg) were subsequently administered prior to inhibitory avoidance retention testing 8 days later. The CNQX impaired, but did not block, inhibitory avoidance retention performance as indicated by the initial latencies to enter the shock compartment. The animals were then retained in the alley until they remained in the starting compartment for 100 consecutive s and entries into the shock compartment were recorded as errors. In both the controls and CNQX-treated groups, increases in amount of original training resulted in fewer errors, indicating memory for the escape training. Furthermore, regardless of the amount of original training (i.e., 0, 1, or 10 trials), CNQX-treated groups made more errors. Other experiments examined intra-amygdala CNQX effects on reactivity to footshock, locomotor activity, and anxiety. CNQX decreased reactivity to footshock, blocked shock-induced decreases in locomotor activity, and had an anxiolytic effect in an elevated plus maze comparable to that induced by midazolam (0.5 μg). These findings suggest that intra-amygdala infusions of CNQX prior to retention testing affect inhibitory avoidance retention performance following aversive training by altering locomotor activity, reducing sensitivity to footshock, and reducing anxiety. The implications of these findings for hypotheses concerning amygdala function in aversively motivated learning and memory is discussed. 相似文献
917.
Erich H. Loewy 《Theoretical medicine and bioethics》1996,17(1):61-74
This paper makes the assumption that organ transplantation is, under some conditions at least, a proper use of communal medical resources. Proceeding from this assumption, the author: (1) sketches the history of the problem; (2) briefly examines the prevalent models of communal structure and offers an alternate version; (3) discusses notions of justice and obligation derived from these different models; (4) applies these to the practice of harvesting organs for transplantation; and then (5) offers a different process for harvesting organs from the newly dead. If community is viewed as united by a set of shred goals and common values among which the value of community itself is important, then certain reciprocal obligations among members obtain. I suggest that routine salvage of organs from the newly dead be instituted but that it be routine salvage “with a twist”: rather early in life all members of the community are given the opportunity to refuse but their refusal carries the reciprocal condition that they cannot later become the recipients of that which they refuse to others. 相似文献
918.
Frank H. Durgin 《Attention, perception & psychophysics》1996,58(2):207-223
An aftereffect of perceived texture density contingent on the color of a surrounding region is reported. In a series of experiments, participants were adapted, with fixation, to stimuli in which the relative density of two achromatic texture regions was perfectly correlated with the color presented in a surrounding region. Following adaptation, the perceived relative density of the two regions was contingent on the color of the surrounding region or of the texture elements themselves. For example, if high density on the left was correlated with a blue surround during adaptation (and high density on the right with a yellow surround), then in order for the left and right textures to appear equal in the assessment phase, denser texture was required on the left in the presence of a blue surround (and denser texture on the right in the context of a yellow surround). Contingent aftereffects were found (1) with black-and-white scatter-dot textures, (2) with luminance-balanced textures, and (3) when the texture elements, rather than the surrounds, were colored during assessment. Effect size was decreased when the elements themselves were colored, but also when spatial subportions of the surround were used for the presentation of color. The effect may be mediated by retinal color spreading (Pöppel, 1986) and appears consistent with a local associative account of contingent aftereffects, such as Barlow’s (1990) model of modifiable inhibition. 相似文献
919.
Fetal brain tissue from the occipital or the frontal cortex was implanted into the damaged occipital cortex of adult rats. The animals receiving grafts of embryonic frontal cortex showed partial restoration of brightness discrimination while recipients given homologous implants of occipital cortex were as impaired as those animals with lesions alone. Neither frontal nor occipital grafts aided in the performance of a pattern discrimination problem; both groups of brain-damaged animals were unable to learn the task. Nonetheless, both groups of animals had viable and enlarged grafts with similar neuronal and glial profiles. 相似文献
920.
Cocaine use in the United States has currently reached epidemic proportions. This has resulted in syndromes of intoxication, overdose, and withdrawal, meeting all DMS-III criteria for a substance that can cause dependence as well as abuse syndromes. This paper reviews the current epidemiology of cocaine, its history and pharmacology with major focus on clinical syndromes. This is followed by a review of the current knowledge of the relationship between cocaine and violence and the forensic-psychiatric issues surrounding cocaine. 相似文献