全文获取类型
收费全文 | 24826篇 |
免费 | 264篇 |
国内免费 | 128篇 |
专业分类
教育 | 16905篇 |
科学研究 | 3308篇 |
各国文化 | 229篇 |
体育 | 1906篇 |
综合类 | 16篇 |
文化理论 | 200篇 |
信息传播 | 2654篇 |
出版年
2020年 | 299篇 |
2019年 | 451篇 |
2018年 | 569篇 |
2017年 | 565篇 |
2016年 | 547篇 |
2015年 | 361篇 |
2014年 | 491篇 |
2013年 | 4511篇 |
2012年 | 456篇 |
2011年 | 494篇 |
2010年 | 374篇 |
2009年 | 385篇 |
2008年 | 430篇 |
2007年 | 449篇 |
2006年 | 434篇 |
2005年 | 404篇 |
2004年 | 371篇 |
2003年 | 361篇 |
2002年 | 345篇 |
2001年 | 360篇 |
2000年 | 401篇 |
1999年 | 384篇 |
1998年 | 223篇 |
1997年 | 227篇 |
1996年 | 274篇 |
1995年 | 242篇 |
1994年 | 227篇 |
1993年 | 248篇 |
1992年 | 343篇 |
1991年 | 347篇 |
1990年 | 356篇 |
1989年 | 385篇 |
1988年 | 318篇 |
1987年 | 346篇 |
1986年 | 350篇 |
1985年 | 394篇 |
1984年 | 365篇 |
1983年 | 350篇 |
1982年 | 286篇 |
1981年 | 286篇 |
1980年 | 257篇 |
1979年 | 373篇 |
1978年 | 325篇 |
1977年 | 271篇 |
1976年 | 241篇 |
1975年 | 220篇 |
1974年 | 226篇 |
1973年 | 221篇 |
1972年 | 184篇 |
1971年 | 188篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
W.A Campbell 《Endeavour》1979,3(1):38-41
Chemical analysis is now so precise and sophisticated a science that it is difficult to appreciate that scarcely a century ago its deficiencies were a cause for public scandal. This article reviews some of the main causes for complaint and how they were remedied. 相似文献
93.
R.C. Rosenberg 《Journal of The Franklin Institute》1979,308(3):343-352
This paper proposes an extended definition of reciprocity for a multiport junction structure based on the concept of essential gyrator coupling. Two theorems are given for junction structures containing gyrators and an algorithm is presented for identifying essential gyrators. The results are useful both theoretically and for designing efficient computation procedures for junction structures. 相似文献
94.
95.
96.
Dynamic retinoscopy has suggested that near vision may be more acute than far vision during early infancy. To test this, acuity thresholds were determined by presenting square wave gratings in a preference paradigm to 1- and 2-month-old human infants at 4 viewing distances. Gratings were paired with unpatterned fields; direction of first fixation was the dependent measure. Infants exhibited the same acuity at each of the distances at which gratings were presented. The results were interpreted as compatible with the fact that considerable optical defocusing does not seriously affect a visual system, such as the infant's, that is sensitive only to low spatial frequencies. 相似文献
97.
The chief purpose of this study was to identify characteristics that distinguish approach as an attachment behavior from approach serving other behavioral systems. Locomotor approaches of 16 male and 10 female white middle-class infants to an attachment figure (the mother) and to a nonattachment figure (the visitor-observer) were examined under naturalistic conditions at home. Observations were made during 4-hour home visits at 3-week intervals; those from 26 to 54 weeks were used. When approach was examined in a free-choice situation and without regard to behavioral context, infants approached the mother proportionally (though slightly) more often than the visitor (p less than .05). In 2 behavioral contexts, however, spontaneous infant approaches were sharply differential to the mother; approaches accompanied by crying and approaches terminating in a pickup appeal were directed almost exclusively to the mother (p less than .0001 for both). Touching upon completion of the approach was not differential, except in the context of a pickup appeal. Object-oriented approaches were more often directed to the visitor than to the mother (p less than .002) and may be either exploratory or affiliative. It is suggested that neither approach nor touching can be assumed to serve the attachment system without consideration of context- both environmental and behavioral. 相似文献
98.
W. Frank Hull IV Walter H. Lemke Jr. 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》1978,24(1):53-64
While off-campus educational programs grow in number and in importance in American higher education, little systematic research has been conducted concerning their effectiveness and intellectual and developmental impact. The project described here compared students in three categories: those studying abroad; those studying off-campus in this country; and those who remained on their home campus. The implications of the findings of the research suggest that a rethinking of existing programs is appropriate, if off-campus educational programs are to realize their full potential. The authors offer concrete suggestions toward restructuring these programs.
Zusammenfassung Obwohl Bildungsprogramme ausserhalb der Universität in der amerikanischen Hochschulbildung an Anzahl und Bedeutung zunehmen, wurde deren Fruchtbarkeit und geistige und entwicklungsmässige Auswirkung kaum systematisch untersucht. Das hier geschilderte Projekt vergleicht Studenten dreier Kategorien: im Ausland studierende, im Lande ausserhalb der Universität studierende und solche, die in ihrem heimischen Universitätsbetrieb geblieben sind. Die Ergebnisse der Untersuchung legen die Folgerung nahe, es sei angebracht, bei eingeführten Programmen zu überdenken, ob die Bildungsprogramme ausserhalb der Universität ihre Möglichkeiten voll ausschöpfen sollen. Die Verfasser machen konkrete Vorschläge für eine Neugestaltung dieser Programme.
Résumé Tandis que l'importance et le nombre des programmes d'éducation en dehors des universités s'accroît dans l'enseignement supérieur aux Etats-Unis, peu de recherche systématique a été effetué en ce qui concerne leur efficacité et leur impact intellectuel et de développement. Le projet décrit ici a comparé des étudiants de trois catégories: ceux qui étudient à l'étranger, ceux qui étudient hors des universités à l'intérieur du pays et ceux qui sont restés dans leurs universités d'origine. Les implications des conclusions de la recherche suggèrent qu'il convient de repenser les programmes existants, si les programmes d'éducation hors des universités doivent réaliser tout leur potentiel. Les auteurs présentent des suggestions concrètes quant à la restructuration de ces programmes.相似文献
99.
100.