全文获取类型
收费全文 | 30732篇 |
免费 | 1285篇 |
国内免费 | 10篇 |
专业分类
32027篇 |
出版年
2020年 | 285篇 |
2019年 | 378篇 |
2018年 | 511篇 |
2017年 | 454篇 |
2016年 | 520篇 |
2015年 | 378篇 |
2014年 | 517篇 |
2013年 | 2329篇 |
2012年 | 893篇 |
2011年 | 900篇 |
2010年 | 583篇 |
2009年 | 578篇 |
2008年 | 803篇 |
2007年 | 842篇 |
2006年 | 774篇 |
2005年 | 693篇 |
2004年 | 669篇 |
2003年 | 589篇 |
2002年 | 624篇 |
2001年 | 1082篇 |
2000年 | 1117篇 |
1999年 | 760篇 |
1998年 | 365篇 |
1997年 | 309篇 |
1996年 | 322篇 |
1995年 | 294篇 |
1992年 | 609篇 |
1991年 | 593篇 |
1990年 | 624篇 |
1989年 | 559篇 |
1988年 | 531篇 |
1987年 | 502篇 |
1986年 | 486篇 |
1985年 | 501篇 |
1984年 | 412篇 |
1983年 | 401篇 |
1982年 | 309篇 |
1979年 | 455篇 |
1978年 | 375篇 |
1977年 | 290篇 |
1975年 | 400篇 |
1974年 | 464篇 |
1973年 | 486篇 |
1972年 | 398篇 |
1971年 | 376篇 |
1970年 | 304篇 |
1969年 | 362篇 |
1968年 | 445篇 |
1967年 | 416篇 |
1966年 | 362篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The present paper selectively reviews the literature which compares full-term and preterm infants' communication with their mothers in the first year of life. The review is focused not only on what differences are found between full-term and preterm infants, but also why such differences exist. Particular emphasis is placed on the importance of interpreting the findings in the light of the developmental phase of the infants, the heterogeneity of the preterm population and the situation in which communication is studied. Most studies were not designed to consider these issues in any detail. Differences with respect to these factors can be found between studies, however, which may have contributed to the often contradictory findings. Consequently, comparisons between these studies provide clues about the effects of these factors on communicative development. The ultimate goal of this review is to point to important directions for future research on early communication in preterm infants. 相似文献
992.
Allen D. Szalda-Petree Andrea M. Karkowski Lisa R. Brooks Nabil F. Haddad 《Behavior research methods》1994,26(1):54-56
A running-wheel-movement-detection system is described for use with an IBM-compatible system and a serial mouse. It is an adaptation of a system developed for use on a Commodore 64. The IBM-compatible system provides obvious advantages in speed, memory, data storage, and programming ease over the earlier Commodore 64 system. 相似文献
993.
In the present paper, we describe a method for recording the coordinates of a fish in an aquarium in a three-dimensional space, using a single video camera and a mirror. We use photogrammetic equations for this, considering the image obtained in the mirror as a virtual image obtained by a second camera. A transformation of the coordinate system is required to express the obtained coordinates in anx,y,z system defined by the edges of the aquarium. The accuracy of the proposed method was estimated, and errors in extreme conditions were found to be 0.8% to 1.2 %, compared with the dimensions of the aquarium used in the test. 相似文献
994.
Jeffrey T. Andre Richard A. Tyrrell Herschel W. Leibowitz Mary E. Nicholson Minqi Wang 《Attention, perception & psychophysics》1994,56(3):261-267
Contrast sensitivity was measured for 12 healthy young males while sober, after ingestion of an alcohol placebo, and after ingestion of alcohol (95% grain alcohol; mean estimated blood alcohol level = .088%). Observations were made for both stationary gratings and gratings that traveled through a circular path and required pursuit eye movements. The significant alcohol-related reduction in contrast sensitivity was 2.6 times greater for moving (.29-log-unit reduction) than for stationary gratings (.11-log-unit reduction). The loss in contrast sensitivity for the moving gratings of high spatial frequency (12 cpd) was particularly severe (.37 log unit). Estimated blood alcohol level was correlated with the loss in contrast sensitivity for moving gratings (r = .61), but not with the loss for stationary gratings. Estimated blood alcohol level was strongly correlated with the difference between the loss in contrast sensitivity to moving and stationary gratings (r = .75). These results are consistent with reports that alcohol consumption degrades the ability to make pursuit eye movements. Subjects’ perceived intoxication level was not a reliable predictor of any index of visual performance. 相似文献
995.
Previous research has shown that a task-irrelevant sudden onset of an object will capture an observer’s visual attention or draw it to that object (e.g., Yantis & Jonides, 1984). However, further research has demonstrated the apparent inability of an object with a task-irrelevant but unique color or luminance to capture attention (Jonides & Yantis, 1988). In the experiments reported here, we reexplore the question of whether task-irrelevant properties other than sudden onset may capture attention. Our results suggest that uniquely colored or luminous objects, as well as salient though irrelevant boundaries, do not appear to capture attention. However, these irrelevant features do appear to serve as landmarks for a top-down search strategy which becomes increasingly likely with larger display set sizes. These findings are described in terms of stimulus-driven and goal-directed aspects of attentional control. 相似文献
996.
Joseph E. O. Newton M.D. D. Michael Oglesby Peggy T. Ackerman Roscoe A. Dykman 《Integrative psychological & behavioral science》1994,29(1):39-54
Using a two-stimulus reaction time paradigm, with two separate reward conditions (contingent and noncontingent), we compared slow wave brain potentials (ERPs) in 144 children with attention deficit disorder (ADD) and 30 normal control children. This article reviews the findings during the 900 msec visual warning stimulus. As we had expected, based on ERP work of Forth and Hare (1989) and Raine, Venables and Williams (1990), and on previous work from our own laboratory, the group differences were found in the negative slow wave portions of the ERP complex during the contingent reward condition but not during the noncontingent condition. Aggressive hyperactive subjects with attention deficit disorder (ADDHA) were discriminated from nonaggressive subjects (including control subjects) during the contingent reward condition in the following ways: (1) greater fronto-central negativity (640–900 msec slow wave) and (2) greater right parietal than left parietal negativity (430–750 msec slow wave). All ADD subgroups, when compared to control (CONTR) subjects, showed greater slow wave negativity (700–900 msec) at the midline occipital electrode site during the contingent reward condition. This could be explained in part as an IQ effect on ERPs reflecting the IQ difference between the ADD subgroups and the controls. These slow wave findings seem to relate to attentional problems of these children. They are discussed in terms of a psychobiological model of inhibition/disinhibition and appetitive activation. 相似文献
997.
998.
Two common methods of measuring personality variables are examined with respect to the ways in which they control respondent biases. A form of the mental-test theory model is developed which makes explicit differences in score components that result from different methodological constraints imposed by the two methods. From the model, it is possible to specify the operations necessary to provide equivalent information from the two sets of data. Performance of these operations in an empirical test supports the model by producing generally higher correlations between the variables having score components which are more closely matched. 相似文献
999.
1000.