全文获取类型
收费全文 | 5415篇 |
免费 | 88篇 |
国内免费 | 5篇 |
专业分类
教育 | 4033篇 |
科学研究 | 356篇 |
各国文化 | 89篇 |
体育 | 469篇 |
综合类 | 2篇 |
文化理论 | 51篇 |
信息传播 | 508篇 |
出版年
2023年 | 18篇 |
2022年 | 40篇 |
2021年 | 69篇 |
2020年 | 109篇 |
2019年 | 157篇 |
2018年 | 198篇 |
2017年 | 230篇 |
2016年 | 205篇 |
2015年 | 134篇 |
2014年 | 167篇 |
2013年 | 1210篇 |
2012年 | 164篇 |
2011年 | 143篇 |
2010年 | 134篇 |
2009年 | 127篇 |
2008年 | 170篇 |
2007年 | 152篇 |
2006年 | 138篇 |
2005年 | 137篇 |
2004年 | 128篇 |
2003年 | 100篇 |
2002年 | 110篇 |
2001年 | 77篇 |
2000年 | 81篇 |
1999年 | 80篇 |
1998年 | 60篇 |
1997年 | 55篇 |
1996年 | 73篇 |
1995年 | 56篇 |
1994年 | 66篇 |
1993年 | 51篇 |
1992年 | 58篇 |
1991年 | 47篇 |
1990年 | 57篇 |
1989年 | 48篇 |
1988年 | 36篇 |
1987年 | 39篇 |
1986年 | 32篇 |
1985年 | 38篇 |
1984年 | 29篇 |
1983年 | 20篇 |
1982年 | 30篇 |
1981年 | 32篇 |
1980年 | 30篇 |
1979年 | 26篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 28篇 |
1974年 | 24篇 |
1973年 | 17篇 |
排序方式: 共有5508条查询结果,搜索用时 15 毫秒
131.
Mergers and acquisitions: Their effect on the innovative performance of companies in high-tech industries 总被引:6,自引:0,他引:6
This study examines the post-M&A innovative performance of acquiring firms in four major high-tech sectors. Non-technological M&As appear to have a negative impact on the acquiring firm's post-M&A innovative performance. With respect to technological M&As, a large relative size of the acquired knowledge base reduces the innovative performance of the acquiring firm. The absolute size of the acquired knowledge base only has a positive effect during the first couple of years after which the effect turns around and we see a negative effect on the innovative performance of the acquiring firm. The relatedness between the acquired and acquiring firms’ knowledge bases has a curvilinear impact on the acquiring firm's innovative performance. This indicates that companies should target M&A ‘partners’ that are neither too unrelated nor too similar in terms of their knowledge base. 相似文献
132.
It is shown that reinvestment and inventory effects can be described in 0431 0368 bond-graph terms. The associated differential equations in price and order-flow 0431 0368 V variables are bilinear forms. These effects are the fundamental inertia and compliance 0431 0368 V 3 of economic bond graph theory. Properties of the components and example market 0431 0368 V 3 graphs are discussed. 相似文献
133.
Paul C. Kainen 《Journal of The Franklin Institute》2004,341(4):391-399
It is shown that cartesian product and pointwise-sum with a fixed compact set preserve various approximation-theoretic properties. Results for pointwise-sum are proved for F-spaces and so hold for any normed linear space, while the other results hold in general metric spaces. Applications are given to approximation of Lp-functions on the d-dimensional cube, 1?p<∞, by linear combinations of half-space characteristic functions; i.e., by Heaviside perceptron networks. 相似文献
134.
Two property regimes for software development may be distinguished. Within corporations, on the one hand, a Private Regime obtains which excludes all outsiders from access to a firm's software assets. It is shown how the protective instruments of secrecy and both copyright and patent have been strengthened considerably during the last two decades. On the other, a Public Regime among hackers may be distinguished, initiated by individuals, organizations or firms, in which source code is freely exchanged. It is argued that copyright is put to novel use here: claiming their rights, authors write ‘open source licenses’ that allow public usage of the code, while at the same time regulating the inclusion of users. A ‘regulated commons’ is created. The analysis focuses successively on the most important open source licenses to emerge, the problem of possible incompatibility between them (especially as far as the dominant General Public License is concerned), and the fragmentation into several user communities that may result. 相似文献
135.
Vaughan Van Hecke A Mundy PC Acra CF Block JJ Delgado CE Parlade MV Meyer JA Neal AR Pomares YB 《Child development》2007,78(1):53-69
Infant joint attention has been observed to be related to social-emotional outcomes in at-risk children. To address whether this relation is also evident in typically developing children, 52 children were tested at 12, 15, 24, and 30 months to examine associations between infant joint attention and social outcomes. Twelve-month initiating and responding to joint attention were related to 30-month social competence and externalizing behavior, even when accounting for 15-month temperament ratings, 24-month cognition and language, and demographic variables. These results suggest that, in addition to associations with language and cognition, infant joint attention reflects robust aspects of development that are related to individual differences in the emergence of social and behavioral competence in childhood. 相似文献
136.
This study examined developmental trends in object and spatial working memory (WM) using heart rate (HR) to provide an index of covert cognitive processes. Participants in 4 age groups (6-7, 9-10, 11-12, 18-26, n=20 each) performed object and spatial WM tasks, in which each trial was followed by feedback. Spatial WM task performance reached adult levels before object WM task performance. The differential developmental trends for object and spatial WM found in this study are taken to suggest that these WM components are separable. Negative performance feedback elicited HR slowing that was more pronounced for adults than for children. The development of performance monitoring as indexed by covert HR slowing following performance feedback contributes to WM performance. 相似文献
137.
Cognition-related brain responses to meaningful and meaningless figures were registered in 5-year-old kindergarten children who either had been subtyped as being at-risk of developing an L- or P-type dyslexia (LAL versus LAP) or who were not at-risk. While identifying, naming, or categorizing pictures, event-related potentials (ERP) were registered. Three cognition-related components were found: the N460, the P780, and the Slow Wave (SW). LAP-children produced weak N460 activity across tasks, whereas LAL children, and to a lesser degree, non-risk children produced robust task-dependent activity. This finding may indicate that LAP-children lack semantic input while processing the figures. P780 latencies to frequently occurring figures were found hemisphere-dependent: LAP-children showed longer latencies in the right than in the left hemisphere, whereas the distribution was reversed in the LAL and non-risk children. It was also found that the right hemisphere is generally responsible for a lion's share of the processing of figures and therefore it seems that the right hemisphere of LAP-children invests ample time in doing so. Whereas LAP-children showed largest SW amplitude differences between frequent and infrequent stimuli at posterior locations, LAL children did so at frontal locations. Assuming that the SW represents working-memory processes, it may be that working-memory in LAP-children deals with figure-relevant visual-spatial information and with figure-derived concepts in LAL children. Overall, the findings suggest that LAL and LAP represent two different groups of kindergartners at risk of dyslexia and that these differences, to some degree, fit with the presumed etiology of L- and P-type dyslexia. 相似文献
138.
Cultural Studies of Science Education - The hope for multicultural, culturally competent, and diverse perspectives in science education falls short if theoretical considerations of whiteness are... 相似文献
139.
Paul H. Smith 《Cambridge Journal of Education》2019,49(2):163-179
Student-mothers who study vocationally related higher education programmes are a relatively under-researched group. Specifically, there is a paucity of research into the emotions that these learners experience. This article discusses a qualitative investigation that examined the emotional narratives that a group of vocational student-mothers offered. They were studying for a foundation degree for teaching assistants at a university in the North of England. The student-mothers were largely found to have experienced positive emotions. However, familial and workplace guilt had also been encountered. These emotions emanated from notions about how family and workplace time should be used. Student-mothers managed this cognitive dissonance by stressing the reciprocal relationships that existed between their studies, family lives and school work. However, for many of these learners familial and workplace guilt was a strong and continuing emotion. 相似文献
140.
Noyens Dorien Donche Vincent Coertjens Liesje van Daal Tine Van Petegem Peter 《European Journal of Psychology of Education - EJPE》2019,34(1):67-86
European Journal of Psychology of Education - Previous theoretical research proposed a link between students’ academic motivation and students’ experiences of social integration, but... 相似文献