全文获取类型
收费全文 | 54667篇 |
免费 | 1384篇 |
国内免费 | 15篇 |
专业分类
56066篇 |
出版年
2020年 | 399篇 |
2019年 | 459篇 |
2018年 | 3893篇 |
2017年 | 3267篇 |
2016年 | 2805篇 |
2015年 | 667篇 |
2014年 | 708篇 |
2013年 | 3013篇 |
2012年 | 1626篇 |
2011年 | 3356篇 |
2010年 | 3138篇 |
2009年 | 2145篇 |
2008年 | 2713篇 |
2007年 | 3052篇 |
2006年 | 1004篇 |
2005年 | 1045篇 |
2004年 | 1044篇 |
2003年 | 946篇 |
2002年 | 908篇 |
2001年 | 826篇 |
2000年 | 863篇 |
1999年 | 690篇 |
1998年 | 444篇 |
1997年 | 435篇 |
1996年 | 373篇 |
1995年 | 383篇 |
1992年 | 601篇 |
1991年 | 547篇 |
1990年 | 547篇 |
1989年 | 518篇 |
1988年 | 537篇 |
1987年 | 504篇 |
1986年 | 523篇 |
1985年 | 518篇 |
1984年 | 483篇 |
1983年 | 420篇 |
1981年 | 371篇 |
1979年 | 497篇 |
1978年 | 426篇 |
1977年 | 363篇 |
1976年 | 382篇 |
1975年 | 399篇 |
1974年 | 502篇 |
1973年 | 519篇 |
1972年 | 376篇 |
1971年 | 400篇 |
1969年 | 377篇 |
1968年 | 448篇 |
1967年 | 409篇 |
1966年 | 418篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
EEG correlation analyses were conducted with children with and without specific learning weaknesses. Reduced left parietal correlation was found in children with dyslectic problems, and in children with adjustment and concentration problems, reduced bioelectric correlation. The frequent evidence of brain injury criteria suggests a link with general affectations of correlation but not specifically with cerebral correlation affections. It would appear to be appropriate to employ computer-assisted EEG correlation analysis, together with frequency analysis and the examination of evoked potentials in objective neurometric diagnosis where children with learning weaknesses are involved. 相似文献
132.
133.
134.
135.
Ratings of pre-morbid intelligence level, derived from the hospital charts of 26 chronic schizophrenics, were correlated with the post-mortem brain volume measures of cortex, white matter, central grey matter, and ventricles. Contrary to hypothesis, no significant correlations were found. 相似文献
136.
M. W. Bunder 《Studia Logica》1988,47(2):129-143
In the early thirties, Church developed predicate calculus within a system based on lambda calculus. Rosser and Kleene developed Arithmetic within this system, but using a Godelization technique showed the system to be inconsistent.Alternative systems to that of Church have been developed, but so far more complex definitions of the natural numbers have had to be used. The present paper based on a system of illative combinatory logic developed previously by the author, does allow the use of the Church numerals. Given a new definition of equality all the Peano-type axioms of Mendelson except one can be derived. A rather weak extra axiom allows the proof of the remaining Peano axiom. Note. The illative combinatory logic used in this paper is similar to the logic employed in computer languages such as ML.The author wishes to thank Dr. Roger Hindley for proofreading this paper and for making some useful suggestions. This paper was presented at the 1986 Annual Conference of the Australasian Association of Logic in Auckland, 9–12 July, 1986. 相似文献
137.
Perception of translational heading from optical flow 总被引:3,自引:0,他引:3
W H Warren M W Morris M Kalish 《Journal of experimental psychology. Human perception and performance》1988,14(4):646-660
Radial patterns of optical flow produced by observer translation could be used to perceive the direction of self-movement during locomotion, and a number of formal analyses of such patterns have recently appeared. However, there is comparatively little empirical research on the perception of heading from optical flow, and what data there are indicate surprisingly poor performance, with heading errors on the order of 5 degrees-10 degrees. We examined heading judgments during translation parallel, perpendicular, and at oblique angles to a random-dot plane, varying observer speed and dot density. Using a discrimination task, we found that heading accuracy improved by an order of magnitude, with 75%-correct thresholds of 0.66 degrees in the highest speed and density condition and 1.2 degrees generally. Performance remained high with displays of 63-10 dots, but it dropped significantly with only 2 dots; there was no consistent speed effect and no effect of angle of approach to the surface. The results are inconsistent with theories based on the local focus of outflow, local motion parallax, multiple fixations, differential motion parallax, and the local maximum of divergence. But they are consistent with Gibson's (1950) original global radial outflow hypothesis for perception of heading during translation. 相似文献
138.
U W Huck R D Lisk E J Parente 《Journal of comparative psychology (Washington, D.C. : 1983)》1988,102(4):388-391
After 12-15 ejaculatory series, each consisting of several short intromissions (2- to 3-s vaginal penetration) and an ejaculation, male golden hamsters adopt an altered copulatory pattern consisting of long intromissions (5- to 25-s penetration with intravaginal thrusting). Receptivity declines and the tendency for the female to attack the male increases at about the time of this shift in copulatory pattern. Because the mean interintromission interval (III) between short intromissions is about 8 s compared to 100 s between long intromissions, it is possible that females detect this difference and adjust their mating accordingly. When the III between short intromissions from a rested male was experimentally increased to 100 s by use of a halter and lead device, the duration of lordosis was significantly less than that displayed by females paired with control males (8-s III) and virtually the same as that displayed by females paired with males that produced only long intromissions. This suggests that the female uses the temporal patterning of intravaginal stimulation as one criterion for terminating mating with a particular male. 相似文献
139.
The authors discuss the results of a study designed to assess nationally certified counselors' perceptions of the relevance of elements of the National Board for Certified Counselors examination to their work as counselors. Support for the validity and appropriateness of the examination in regard to perceived relevance and lack of differentiation on the basis of respondent characteristics were found. 相似文献
140.
Bonaparte, G., Chapman, J., & Steinberg, J. (1987). Michigan: Two career guidance models. Vocational Education Journal, 62(6), 142–143. Greenwood, K. (1987). Counseling adults in career transition. Vocational Education Journal, 62(6), 44–46. Herr, E.L. (1987). Comprehensive career guidance and vocational education: Natural allies. Vocational Education Journal, 62(6), 30–33. Lambert, R. (1987). A guide to career information. Vocational Education Journal, 62(6), 34–36. Lester, J.N., & McCormac, M.E. (1987). The NOICC career guidance standards project. Vocational Education Journal, 62(6), 47–48. Otto, L.B. (1987). Parents: Key advisors. Vocational Education Journal, 62(6), 37–38. 相似文献