全文获取类型
收费全文 | 54035篇 |
免费 | 2270篇 |
国内免费 | 36篇 |
专业分类
56341篇 |
出版年
2020年 | 635篇 |
2019年 | 757篇 |
2018年 | 1086篇 |
2017年 | 1085篇 |
2016年 | 1222篇 |
2015年 | 846篇 |
2014年 | 995篇 |
2013年 | 4424篇 |
2012年 | 1787篇 |
2011年 | 1798篇 |
2010年 | 1062篇 |
2009年 | 1126篇 |
2008年 | 1443篇 |
2007年 | 1543篇 |
2006年 | 1289篇 |
2005年 | 1171篇 |
2004年 | 1112篇 |
2003年 | 1042篇 |
2002年 | 1056篇 |
2001年 | 1722篇 |
2000年 | 1685篇 |
1999年 | 1265篇 |
1998年 | 535篇 |
1997年 | 498篇 |
1996年 | 507篇 |
1992年 | 1016篇 |
1991年 | 960篇 |
1990年 | 965篇 |
1989年 | 900篇 |
1988年 | 896篇 |
1987年 | 825篇 |
1986年 | 840篇 |
1985年 | 879篇 |
1984年 | 718篇 |
1983年 | 644篇 |
1982年 | 496篇 |
1979年 | 809篇 |
1978年 | 569篇 |
1977年 | 499篇 |
1976年 | 503篇 |
1975年 | 628篇 |
1974年 | 775篇 |
1973年 | 800篇 |
1972年 | 667篇 |
1971年 | 610篇 |
1970年 | 595篇 |
1969年 | 570篇 |
1968年 | 731篇 |
1967年 | 637篇 |
1966年 | 601篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
William Hodos James C. Bonbright Jr. 《Journal of the experimental analysis of behavior》1972,18(3):471-479
Pigeons were trained in a conditional discrimination procedure to discriminate between visual stimuli that varied in intensity. The magnitude of the intensity difference ranged from 0.80 to 0.05 logarithmic units. Psychometric functions were calculated from the data and the mean difference threshold for the 11 subjects was approximately 0.12 logarithmic units. A signal-detection analysis of the data suggested that stimuli that were below the calculated threshold were detectible to the subjects. 相似文献
992.
Williams BA 《Journal of the experimental analysis of behavior》1972,17(3):363-368
Pigeons were trained on a probability learning task where the overall reinforcement probability was 0.50 for each response alternative but where the momentary reinforcement probability differed and depended upon the outcome of the preceding trial. In all cases, the maximum reinforcement occurred with a “win-stay, lose-shift” response pattern. When both position and color were relevant cues, the optimal response pattern was learned when the reinforcement probability for repeating the just-reinforced response was 0.80 but not when the probability was 0.65. When only color was relevant, learning occurred much more slowly, and only for subjects trained on large fixed ratio requirements. 相似文献
993.
Leander JD Milan MA Jasper KB Heaton KL 《Journal of the experimental analysis of behavior》1972,17(2):229-235
The vocal behavior of three Cebus monkeys was maintained by fixed-ratio schedules of response dependent reinforcement at values between fixed-ratio 1 and fixed-ratio 15. In one monkey that was exposed to variable-interval, fixed-interval, and conjunctive fixed-ratio fixed-interval schedules of reinforcement, vocal responding occurred at a low rate, but schedule-appropriate patterns were maintained. The rates and patterns of responding engendered indicated that the vocal operant can be brought under schedule control in the monkey by the use of response-dependent reinforcement. 相似文献
994.
995.
996.
997.
Steven B. Christopher 《Behavior research methods》1972,4(1):19-20
The validity of a primate dominance hierarchy was examined in terms of its relationship to social interactions. Twelve social behaviors associated with dominance and aggression were recorded during 61 h of observation of six pigtail macaques (Macaca nemestrina). Of the 1,462 interactions recorded, 94.7% were oriented in the water dominance hierarchy in the direction that would be predicted on the basis of their ascribed functions. 相似文献
998.
D. C. Mitchell 《Quarterly journal of experimental psychology (2006)》1972,24(4):394-405
The results of two experiments involving the matching of unfamiliar, nameless shapes (Gibson forms) indicated that a visual representation of a brief (30-100 ms) stimulus survives in a Short-Term Visual Memory (STVM) for 6 s or more after the onset of a pattern mask. On the basis of these results a possible alternative to Sperling's (1967) model for short-term memory for visual stimuli was presented. In this model it is assumed that recognition processes occupy several hundred milliseconds and continue after the arrival of the mask using the information available in STVM. 相似文献
999.
Conventional procedures do not provide a practical method for the administration of volatile anesthetics such as halothane to rats while they are undergoing stereotaxic surgery. This paper describes a device which meets this need and which is easy and inexpensive to construct. A two-piece cylinder cut from the mouth of a polyethylene bottle forms a closed system around the muzzle of a rat and does not interfere with the stereotaxic apparatus or with the operation itself. The cylinder is attached to any standard device for the dispension of volatile anesthetics. The immediate advantage is that behavioral assesaments can be made relatively soon after surgery. 相似文献
1000.