全文获取类型
收费全文 | 46058篇 |
免费 | 2057篇 |
国内免费 | 33篇 |
出版年
2020年 | 542篇 |
2019年 | 645篇 |
2018年 | 928篇 |
2017年 | 879篇 |
2016年 | 982篇 |
2015年 | 691篇 |
2014年 | 803篇 |
2013年 | 3605篇 |
2012年 | 1516篇 |
2011年 | 1584篇 |
2010年 | 922篇 |
2009年 | 969篇 |
2008年 | 1263篇 |
2007年 | 1263篇 |
2006年 | 1115篇 |
2005年 | 971篇 |
2004年 | 951篇 |
2003年 | 886篇 |
2002年 | 893篇 |
2001年 | 1632篇 |
2000年 | 1622篇 |
1999年 | 1149篇 |
1998年 | 480篇 |
1997年 | 459篇 |
1995年 | 428篇 |
1992年 | 936篇 |
1991年 | 864篇 |
1990年 | 860篇 |
1989年 | 820篇 |
1988年 | 810篇 |
1987年 | 728篇 |
1986年 | 752篇 |
1985年 | 790篇 |
1984年 | 638篇 |
1983年 | 570篇 |
1982年 | 421篇 |
1979年 | 633篇 |
1978年 | 472篇 |
1977年 | 425篇 |
1976年 | 428篇 |
1975年 | 533篇 |
1974年 | 653篇 |
1973年 | 636篇 |
1972年 | 587篇 |
1971年 | 493篇 |
1970年 | 454篇 |
1969年 | 513篇 |
1968年 | 603篇 |
1967年 | 514篇 |
1966年 | 520篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
981.
Diane K. Kjervik 《Behavioral sciences & the law》1984,2(2):207-218
It is proposed that society should re-examine its assumptions about suicide. Rational suicide is viewed as an extension of the right to die. After a review of the legal liability of the psychotherapist and psychiatric facility for both inpatient and outpatient suicide, the author presents an analysis of philosophical, ethical, and psychoanalytic arguments for allowing rational suicide. It is argued that emotional pain should be given more legitimacy as a reason for suicide. The decision to live or to die is argued to best rest with the individual. 相似文献
982.
不同时相日光下颜色的恒常性 总被引:1,自引:0,他引:1
一、前言 在光源光谱成份改变的条件下,我们周围物体的颜色在眼睛看来保持相对不变,称为颜色恒常性。1807年Thomas Young首先描述了颜色恒常性现象,他指出室内不管是由蜡烛的黄光或火焰的红光来照明的,书页纸仍然看来是白色的。Young认为,外界某一表面的颜色外观,并不完全决定于网膜的红、绿、蓝三种感受器的吸收特性,而也依赖于周围其它物体射入眼睛的光通量。此后,E.Hering对颜色恒常性做了实验表演。一般认为颜色恒常性是对环境照明感受性的降低。视觉通道只传递由物体表面所反射的光谱成 相似文献
983.
Smokers and nonsmokers were compared on three aspects of academic achievement. Although exactly the same percentage of smokers
and nonsmokers passed the first-year university examination, smokers obtained significantly higher marks. Similarly, smokers
achieved significantly higher marks in their final year examinations in comparison with nonsmokers. Finally, a comparison
of the tutorial essay marks of the smokers and nonsmokers again showed that smokers obtained significantly higher marks than
nonsmokers. These data are consistent with the idea that ambitious students adopt smoking in the belief that it will help
them study and sustain concentration. 相似文献
984.
985.
K. J. Gilhooly 《Current Psychology》1984,3(2):24-31
Previous reports of age-of-acquisition effects have been theoretically ambiguous since, in any particular individual, word
age-of-acquisition is perfectly correlated with the length of time that a word has been known. The study reported in this
article attempted to disentangle effects of word age-of-acquisition and length of word residence time in lexical memory. To
this end, words varying in recency-of-introduction to British English were presented in a word-naming task to 46 native speakers
whose ages ranged from 20 to 58 years. Using subjects’ ratings of the words on age-of-acquisition, it was possible to assess
word residence times and to compare the effects on naming speeds of age-of-acquisition and residence times. Regression analyses
indicated that age-of-acquisition was a more important factor than residence time in the word-naming task. 相似文献
986.
Suicide and rurality in urban society 总被引:3,自引:0,他引:3
Recent findings suggest that suicide increases with rurality, but research on rural suicide leaves many questions unanswered. This study specifies problems of community organization as a reason for expecting a positive effect of rurality on the suicide rate. A multiple regression analysis of county data shows that rurality has a substantial positive effect and is, in fact, the best predictor of the suicide rate among several variables selected from the previous literature. Additional research is needed to test the interpretation that rurality contributes to an incomplete, fragmented form of community organization which influences the suicide rate by disrupting primary relationships. 相似文献
987.
988.
Myron Charles Baker Diana F. Tomback Daniel B. Thompson Tad C. Theimer Dana C. Bradley 《Learning and motivation》1984,15(4):428-440
The functional significance of learned population differences in male song in the white-crowned sparrow was explored in natural populations using playback tests. Laboratory results have shown that learning of the population-specific song seems to take place in early life and is strongly dependent upon the nature of the auditory experience at that time. However, the varied results of recent studies make it difficult to reach a confident conclusion about the ecological functions of song learning. The present research took advantage of naturally occurring variation in the differences between songs of adjacent populations to determine a function relating degree of difference in song to intensity of territorial singing elicited. Applying a typological evaluation of syllable structure to the four segments of the song allowed a crude quantitative ranking of the differences between local songs and playback stimuli. These results, together with those of other studies, suggest a unimodal aggressive response function of males to songs of other males. A maximum response to songs slightly different from the local song environment suggests that male exclusion based upon acquired song components may contribute to the maintenance of discrete and stable song dialects. 相似文献
989.
Three experiments are described which elaborate some of the conditions under which rats will contact and manipulate a periodically presented retractable lever. Experiment 1 demonstrated that (i) initial manipulative oral and manual contact with the lever was facilitated if the rat had previous experience of food delivery in the experimental chamber; (ii) persistence in contacting the lever on successive presentations was a function of whether food continued to be presented in the experimental environment; and (iii) food satiation significantly reduced the tendency of the rat to contact the lever even though an expectancy of food had previously been established under conditions of food deprivation. Experiment 2 suggested that the tendency to approach and contact the lever was in part a function of the local moment-to-moment conditional probability of food delivery. Experiment 3 found that the probability of contacting the lever was higher during presentation of an auditory CS signaling a high rate of food delivery than during stimuli signaling no food at all. These results are interpreted as suggesting that the food-signaling aspects of an appetitive CS and that CS's ability to generate signal-directed behaviors are experimentall separable properties. 相似文献
990.
To evaluate a contingency interpretation of conditioned inhibition (CI), rats were given “explicity unpaired” training in which the locus and duration of a CS within the inter-US (shock) interval were systematically manipulated for different groups. Summation and retardation tests in Experiment 1 indicated that stronger CI resulted from both a backward and a trace CS than from a midlocus CS of equal or greater duration. Complementing these findings, the same tests in Experiment 2 showed that, by comparison with novel-stimulus controls, CI developed to a trace CS but not to a mid-locus CS, nor to a trace CS that was accompanied by an immediate signal for the US. These findings argue against a contingency interpretation of CI and favor a contiguity interpretation stressing the short-term rehearsal of stimulus events. Such rehearsal of the US allows a backward CS, but not a mid-locus CS with an extended US-CS interval, to be discriminated as a signal for nonreinforcement, and thus to develop as a conditioned inhibitor. Similarly, excitatory conditioning to the memory trace of a CS allows the nominal trace CS to develop as a signal for nonreinforcement, and thus as a conditioned inhibitor, but not when its memory trace is overshadowed by another CS that immediately precedes the US. In short, the development of CI is facilitated when excitation is mediated by the memorial processing of either the US or a discrete CS for the US rather than by contextual cues. 相似文献