全文获取类型
收费全文 | 93996篇 |
免费 | 4842篇 |
国内免费 | 9288篇 |
专业分类
108126篇 |
出版年
2023年 | 1155篇 |
2022年 | 1360篇 |
2021年 | 815篇 |
2020年 | 1229篇 |
2019年 | 1344篇 |
2018年 | 1670篇 |
2017年 | 858篇 |
2016年 | 955篇 |
2015年 | 792篇 |
2014年 | 2058篇 |
2013年 | 1571篇 |
2012年 | 7856篇 |
2011年 | 9535篇 |
2010年 | 3612篇 |
2009年 | 3048篇 |
2008年 | 8428篇 |
2007年 | 8050篇 |
2006年 | 7388篇 |
2005年 | 6201篇 |
2004年 | 5508篇 |
2003年 | 5103篇 |
2002年 | 4520篇 |
2001年 | 3275篇 |
2000年 | 4182篇 |
1999年 | 1765篇 |
1998年 | 619篇 |
1997年 | 590篇 |
1996年 | 543篇 |
1995年 | 596篇 |
1994年 | 586篇 |
1993年 | 516篇 |
1992年 | 483篇 |
1991年 | 458篇 |
1990年 | 484篇 |
1989年 | 457篇 |
1988年 | 592篇 |
1987年 | 577篇 |
1986年 | 437篇 |
1985年 | 530篇 |
1984年 | 437篇 |
1983年 | 454篇 |
1982年 | 366篇 |
1981年 | 352篇 |
1958年 | 641篇 |
1957年 | 523篇 |
1956年 | 448篇 |
1955年 | 425篇 |
1954年 | 334篇 |
1953年 | 304篇 |
1952年 | 292篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
931.
Older people are increasingly the focus of biomedical and behavioral research not only because the elderly constitute the fastest growing segment of our population but because there is a societal concern to improve the elderly's quality of life. The profound need to advance that research carries with it an equally profound obligation to protect the rights and welfare of elderly research subjects, and thus raises difficult ethical and legal issues. Against a background of foundational principles for the protection of human subjects, we discuss whether older subjects should be treated as a special class, the ethical and legal issues over informed consent, capacities for consent, and special problems related to cognitive impairment. We discuss surrogate/proxy consent procedures in research, recruitment of elderly subjects, conflicts of interest, special problems regarding institutional research, and risk/benefit analyses. We offer recommendations and practical guidelines for conducting current and future research involving elderly participants. 相似文献
932.
Recent legislative and regulatory developments have focused attention on older adults' capacity for involvement in health care decision-making. The Omnibus Budget Reconciliation Act of 1987 (OBRA 87) focused attention on the rights of nursing home residents to be involved in health care decision-making to the fullest extent possible. This article uses data from the 1987 National Medical Expenditure Survey (NMES) to examine rates of incapacity for health care decision-making among nursing home residents. Elements of the Oklahoma statute were used to operationalize decision-making incapacity: disability or disorder, difficulty in decision-making or communicating decisions, and functional disability. Fifty-three percent of nursing home residents had a combination of either physical or mental impairment and an impairment in either self-care or money management. The discussion focuses on the policy and practice implications of significant rates of incapacity among nursing home residents. 相似文献
933.
934.
Greene BF Norman KR Searle MS Daniels M Lubeck RC 《Journal of applied behavior analysis》1995,28(4):417-434
Two families, in which the children had been placed in foster care due to abuse and neglect by parents who had disabilities, were studied. In the first case, the mother was instructed in skills that our assessment suggested were important for her child's survival. The mother readily acquired and applied these skills, a fact reflected both in changes in her behavior and in changes in the child's well-being. In the second case, the parent's incremental resumption of child custody was made contingent upon completion of relevant parenting tasks. Initially, improvements in the completion of such tasks were evident, but over time and with the onset of militating factors, no further progress was made and all parental rights were terminated. The implications of these cases for behavior analysis and the effort to reunite and preserve families are discussed. 相似文献
935.
We discuss Belke and Spetch's (1994) work on choice between reliable and unreliable reinforcement. The studies by Belke and Spetch extend a line of basic research demonstrating that under certain experimental conditions in a concurrent chains procedure, pigeons prefer an alternative that produces unreliable reinforcement. The authors describe the variables that influence preference for unreliable reinforcement, including the signaling and the duration of the reinforcement schedules, the context in which the signaling stimuli occur, and the effects of conditioned reinforcement. Hypothetical applied examples that address these variables are provided, and their influence on preference for unreliable reinforcement in humans is discussed. We conclude by suggesting a line of applied research to examine the relationship between these variables and a preference for unreliable reinforcement. 相似文献
936.
Comparing interspersed requests and social comments as antecedents for increasing student compliance
Two students were alternately presented with interspersed high-compliance requests and social comments as antecedents to low-compliance requests. An initial comparison demonstrated similar positive effects on compliance for interspersed requests and social comments. A second analysis indicated that the effectiveness of social comments for increasing compliance was related to the time interval between social comments and low-compliance requests. 相似文献
937.
Although extinction has been an effective treatment for a variety of behavior disorders, its use may be associated with several adverse side effects, the most common being an initial increase in the frequency of the target response, called an "extinction burst." We attempted to determine the prevalence of the extinction burst in applied research and its possible attenuation with other operant procedures. An analysis of 113 sets of extinction data indicated that bursting may not be as common as previously assumed (it occurred in 24% of the cases) and may be less likely when extinction is implemented with alternative procedures rather than as the sole intervention (bursting was evident in 12% of the former cases and 36% of the latter). 相似文献
938.
Predicting and scaling hens' preferences for topographically different responses 总被引:2,自引:1,他引:1 下载免费PDF全文
Six hens were exposed to several concurrent (second-order) variable-interval schedules in which the response requirements on the alternatives were varied. The response requirements were one key peck versus five key pecks, one key peck versus one door push, and five key pecks versus one door push. Response- and time-allocation ratios undermatched the obtained reinforcement ratios but were well described by the generalized matching law. Time and response bias estimates from two pairs of response requirements were used to predict bias in the third pairing. The predicted values were close to those obtained; this result supports the notion that both numerically and topographically different responses act as constant sources of bias within the generalized matching law. The differences between the response and time biases could be accounted for by the different times needed to complete each response requirement. The results also suggest that the door push is a useful operant for research with domestic hens. 相似文献
939.
Stimulus control in the use of landmarks by pigeons in a touch-screen task 总被引:2,自引:1,他引:1 下载免费PDF全文
Pigeons were tested in a search task on the surface of a monitor on which their responses were registered by a touch-sensitive device. A graphic landmark array was presented consisting of a square outline (the frame) and a colored “landmark.” The unmarked goal, pecks at which produced reward, was located near the center of one edge of the frame, and the landmark was near it. The entire array was displaced without rotation on the monitor from trial to trial. On occasional no-reward tests, the following manipulations were made to the landmark array: (a) either the frame or the landmark was removed; (2) either one edge of the frame or the landmark was shifted; and (3) two landmarks were presented with or without the frame present. On these two-landmark tests, the frame, when present, defined which was the “correct” landmark. When the frame was absent, the “correct” landmark was arbitrarily determined. Results showed that pecks of 2 pigeons were controlled almost solely by the landmark, pecks of 3 were controlled primarily by the landmark but the frame could distinguish the correct landmark, and 1 bird's behavior was controlled primarily by the frame. Stimulus control in this search task is thus selective and differs across individuals. Comparisons to other search tasks and to other stimulus control experiments are made. 相似文献
940.
Humphrey and Dahlstrom (1995) presented a study on the comparability of MMPI/MMPI-2 (Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989) profiles in which they concluded that "the bases for clinical interpretation derived from the MMPI and MMPI-2 profiles were sufficiently at variance to require different conclusions" [sic] (p. 2). In this brief critique, we identify procedural and data-analytical deficiencies that invalidate Humphrey and Dahlstrom's argument. Their blanket recommendation based on this argument, namely, that clinicians routinely plot both MMPI and MMPI-2 profiles, is unwarranted. 相似文献