全文获取类型
收费全文 | 165139篇 |
免费 | 7588篇 |
国内免费 | 155篇 |
专业分类
172882篇 |
出版年
2021年 | 1479篇 |
2020年 | 2763篇 |
2019年 | 3424篇 |
2018年 | 3404篇 |
2017年 | 3835篇 |
2016年 | 4527篇 |
2015年 | 3898篇 |
2014年 | 4779篇 |
2013年 | 23362篇 |
2012年 | 4297篇 |
2011年 | 3237篇 |
2010年 | 3745篇 |
2009年 | 4681篇 |
2008年 | 3525篇 |
2007年 | 3075篇 |
2006年 | 3754篇 |
2005年 | 3768篇 |
2004年 | 3265篇 |
2003年 | 2900篇 |
2002年 | 2715篇 |
2001年 | 3101篇 |
2000年 | 2981篇 |
1999年 | 2992篇 |
1998年 | 2793篇 |
1997年 | 2639篇 |
1996年 | 2562篇 |
1995年 | 2391篇 |
1994年 | 2362篇 |
1993年 | 2310篇 |
1992年 | 2463篇 |
1991年 | 2310篇 |
1990年 | 2178篇 |
1989年 | 2085篇 |
1988年 | 2038篇 |
1987年 | 2082篇 |
1986年 | 2051篇 |
1985年 | 2251篇 |
1984年 | 2411篇 |
1983年 | 2228篇 |
1982年 | 2327篇 |
1981年 | 2296篇 |
1980年 | 2155篇 |
1979年 | 2063篇 |
1978年 | 2123篇 |
1977年 | 2100篇 |
1976年 | 1873篇 |
1975年 | 1877篇 |
1974年 | 1922篇 |
1973年 | 1772篇 |
1972年 | 1384篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
981.
Measurements of gaze movements while driving 总被引:1,自引:0,他引:1
In this study, gaze movements of drivers driving through an intersection were investigated. Gaze movements of drivers in large vehicles were compared with those in small vehicles. There were both similarities and differences in the visual search behaviors of drivers of large and small vehicles. The two groups were similar in that, when approaching an intersection, drivers made repeated saccadic gaze movements; after entering the intersection, saccadic gaze movements were directed ahead in the direction of turning. Differences arose in the frequency and distribution of gaze movements. The number of gaze movements was significantly greater in drivers of large vehicles. The distribution of gaze movements in driving a large vehicle showed a peak at the point 50 to 60 degrees to the right and left of the median plane of the driver. The distribution of gaze movements of drivers of small vehicles showed no peak across the visual field. 相似文献
982.
The hypothesis that there are two neural mechanisms for electrocutaneous stimulation--one that is sensitive to low current and is adaptive to repeated stimulation and another that is responsive to high current and is less adaptive--was tested in a control and four main experiments. In the main experiments, magnitude estimates obtained for single electrical pulses (of 2-msec duration) were described by a simple power function for each combination of high- and low-current levels and 10 trial blocks. The results were: (1) The slope of the power function for low current was steeper than was that for high current; (2) for low current, the intercept of the power function decreased with increasing block, whereas for high current, it remained constant over blocks; (3) this decrease of the intercept for low current disappeared when judgmental blocks were separated by a rest period of 8 min; (4) the modulus did not affect the slope; (5) for a large modulus combined with low current, the intercept decreased rapidly over trial blocks, whereas for a small modulus combined with high current, the intercept increased over trial blocks. The first four findings support the two-mechanism hypothesis, but the last one may also be interpretable in terms of the regression to absolute scale values. 相似文献
983.
The rod-and-frame effect (RFE) was investigated with the use of a frame that oscillated about an axis at its center at five different frequencies, ranging from .013 to .213 Hz. The resultant RFE shifted continuously with the roll motion of the frame, and it was significantly larger at the lowest frequency (.013 Hz) than under comparable static conditions. The dynamic RFE was lowest at the higher oscillation frequencies. Oscillatory roll vection--apparent self-motion--was reported by 3 of the 9 subjects when the frame was oscillating at its highest frequency (.213 Hz). The subjects yielded large increases in the RFE during the sessions with reports of vection. Surrounding the kinetic frame with a circular contour eliminated all reports of vection and significantly interacted with frequency to reduce the RFE--but only at low frequencies. The reduction amounted to 21.2% averaged over all 9 subjects at the three lowest frequencies. A surrounding contour, therefore, suppressed low-frequency kinetic visual orientation information that might otherwise have produced larger changes in apparent self-orientation and perceived vertical. Vection-sensitive subjects differed from nonvection subjects by exhibiting (1) a high-frequency fall-off in real-motion gain, (2) a high-frequency enhancement in illusory-motion gain, and (3) only a small and nonsignificant increase in illusory-movement phase lag with increases in frequency. 相似文献
984.
985.
19 pairs of third grade children from intact and single-parent families matched for sex, intellectual ability, and academic achievement were administered a brief self-concept measure. Teachers and parents rated the students' self-concept on similar measures. There were no significant differences in scores between the groups; however, within each group the teachers and parents consistently overestimated students' self-esteem. 相似文献
986.
A quasi-nonmetric method for multidimensional scaling VIA an extended euclidean model 总被引:1,自引:0,他引:1
An Extended Two-Way Euclidean Multidimensional Scaling (MDS) model which assumes both common and specific dimensions is described and contrasted with the standard (Two-Way) MDS model. In this Extended Two-Way Euclidean model then stimuli (or other objects) are assumed to be characterized by coordinates onR common dimensions. In addition each stimulus is assumed to have a dimension (or dimensions) specific to it alone. The overall distance between objecti and objectj then is defined as the square root of the ordinary squared Euclidean distance plus terms denoting the specificity of each object. The specificity,s
j
, can be thought of as the sum of squares of coordinates on those dimensions specific to objecti, all of which have nonzero coordinatesonly for objecti. (In practice, we may think of there being just one such specific dimension for each object, as this situation is mathematically indistinguishable from the case in which there are more than one.)We further assume that
ij
=F(d
ij
) +e
ij
where
ij
is the proximity value (e.g., similarity or dissimilarity) of objectsi andj,d
ij
is the extended Euclidean distance defined above, whilee
ij
is an error term assumed i.i.d.N(0, 2).F is assumed either a linear function (in the metric case) or a monotone spline of specified form (in the quasi-nonmetric case). A numerical procedure alternating a modified Newton-Raphson algorithm with an algorithm for fitting an optimal monotone spline (or linear function) is used to secure maximum likelihood estimates of the paramstatistics) can be used to test hypotheses about the number of common dimensions, and/or the existence of specific (in addition toR common) dimensions.This approach is illustrated with applications to both artificial data and real data on judged similarity of nations. 相似文献
987.
Robert L. Beck 《Journal of Family Therapy》1989,11(3):231-241
This paper describes the use of concurrent individual and conjoint sessions in couples psychotherapy. The introduction of these individual interviews is seen as supporting the individual changes which must be made to effect change in the structure of the relationship. The benefits of this interventive scheme in dynamically oriented couples' treatment will be illustrated through the presentation of case examples. 相似文献
988.
I. Bennun 《Journal of Family Therapy》1989,11(3):243-255
Thirty-five families completed ratings describing their perceptions of their therapists. These ratings were then correlated with measures of outcome to assess whether there was a relationship between experiences of the therapist and treatment outcome. Further, the study addresses whether some family members' perceptions are more influential in affecting the course of treatment. The results showed that family members' perception of the therapist does have an impact on treatment outcome, but not all members affect the outcome equally. Further results and their implications are discussed. 相似文献
989.
990.
T Eckes 《Archiv für Psychologie》1989,141(2):99-112
An investigation is conducted into whether male and female perceivers hold substantially different implicit theories of personality. 24 male and 24 female subjects were asked to sort a set of 36 trait names into groups of similar traits. On the basis of these data, proximities between trait names and proximities between groupings (or partitions) were computed and subjected to a differential statistical analysis. Neither a global test for sex-specific groupings of trait names nor tests at the level of perceived pairwise trait relationships yielded significant differences. It is concluded that aggregation of sorting data over both male and female perceivers is warranted without too big a loss of information. On the methodological side, this paper demonstrates the feasibility of a quantitative approach to handling the problem of data aggregation in the context of studies using the sorting method as a data-gathering technique. 相似文献