首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   172450篇
  免费   7778篇
  国内免费   158篇
  2021年   1511篇
  2020年   2796篇
  2019年   3474篇
  2018年   3506篇
  2017年   3960篇
  2016年   4639篇
  2015年   3941篇
  2014年   4831篇
  2013年   23675篇
  2012年   4511篇
  2011年   3623篇
  2010年   3943篇
  2009年   4814篇
  2008年   3908篇
  2007年   3435篇
  2006年   4086篇
  2005年   4046篇
  2004年   3533篇
  2003年   3244篇
  2002年   3024篇
  2001年   3012篇
  2000年   2932篇
  1999年   3004篇
  1998年   2830篇
  1997年   2680篇
  1996年   2603篇
  1995年   2428篇
  1994年   2395篇
  1993年   2338篇
  1992年   2525篇
  1991年   2361篇
  1990年   2208篇
  1989年   2119篇
  1988年   2110篇
  1987年   2096篇
  1986年   2092篇
  1985年   2301篇
  1984年   2451篇
  1983年   2263篇
  1982年   2312篇
  1981年   2288篇
  1980年   2148篇
  1979年   2134篇
  1978年   2158篇
  1977年   2121篇
  1976年   1928篇
  1975年   1972篇
  1974年   2046篇
  1973年   1949篇
  1972年   1481篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
992.
993.
994.
995.
The purpose of this study was to document the responses of pharmacy students and pharmacists to various ethical dilemmas. The responses of the first professional year students, third professional year students and pharmacists were evaluated and compared. In most instances, responses indicated a high priority for patient/client welfare. Pharmacists and students reportedly act with regard to the dignity of life, individual freedom, and an inner sense of right.  相似文献   
996.
997.
Pigeons were trained to acquire a new four-response position sequence each day by pecking three response keys in a predetermined order. The key color varied after each correct response prior to food delivery. Acute administration of Γ9-tetrahydrocannabinol (Δ9-THC) up to a dose that completely eliminated responding, had no effect on total acquisition errors, or on within session patterns of error elimination. Chronic administration of Δ9-THC (3–10 mg/kg/day), either before or after the session for 4–7 weeks, also did not affect these error measures, although rates of responding were markedly suppressed and at times no responding occurred Discontinuation of Δ9-THC administration for periods of 4–6 weeks also was without effect on errors. These experiments suggest that neither acute nor chronic Δ9-THC produce specific effects on the repeated acquisition of serial position responses in pigeons.  相似文献   
998.
Experiment 1 elicited the P1, N1, P2, and N2 components of the long latency auditory evoked potential (AEP) using a 1000 Hz tone presented at 30, 50, or 70 dB SPL and 1-, 3-, or 5- second inter-stimulus intervals to assess the relative effects of the combination of these variables on component amplitude and latency. Four blocks of 16 tone presentations each were recorded from each subject to determine if changes in the AEP would occur because of short-term habituation. Both stimulus factors interacted significantly in a systematic fashion for the amplitude measures, with increases in latency also associated with increases in intensity and inter-stimulus interval. Only minor changes across the four trial blocks for either the amplitude or latency measures were observed over the various stimulus presentation conditions. Experiment 2 employed the same tone stimulus presented at 50 dB SPL and a 3-second inter-stimulus interval. Eight blocks of 64 trials were recorded from each subject on each day for four days to investigate long-term habituation effects. No substantial changes in any of the component amplitudes or latencies were obtained across the 32 trial blocks. It was concluded that intensity and inter-stimulus interval interact to determine AEP amplitude as well as latency values and that the constituent components do not change appreciably with repeated stimulus presentations, even after several days.  相似文献   
999.
The present study outlines a rapid and sensitive on-the-baseline conditional emotional response (CER) procedure. Using rats as the experimental subject, the method detects delay conditioning, incubation, extinction and spontaneous recovery. In addition, the method detects conditional responding using electric shock ranging from 0.23 to 0.50 mA as the unconditional stimulus. Because of its speed and sensitivity, the method shelters the subject from unnecessary long-term deprivation and pain.  相似文献   
1000.
The manipulation of stimulus significance, by instructions from the experimenter, may be taken as an example of verbal conditioning. Consideration of such a mechanism suggested that personality effects previously found in conditioning studies should be apparent in instructional manipulations of significance in a study of the orienting response (OR) to words. Because of recent changes in dimensioning of the personality structure, some of the items originally used to define Eysenck’s extraversion (E) dimension are now used to assess the new dimension of psychoticism (P), suggesting that at least some of the established effects of E upon conditioning may be associated now with P. Hence the P scale was focused on in this study. Words differing on the evaluative dimension of the semantic differential were presented in three blocks, the first under indifferent instructions, the second under instructions to rate the words for their affective impact, and the third under indifferent instructions again. These blocks correspond to baseline, conditioning, and extinction conditions respectively. Electrodermal activity indicated enhanced conditioning, together with greater carry-over effects in the extinction phase, for low-P compared with high-P subjects. The results indicate the importance of personality effects in studies of stimulus significance and illustrate the value of the verbal conditioning mechanism in this area of the OR field. They also suggest the need to re-examine previously obtained E-effects in conditioning studies in light of changing personality tests.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号