全文获取类型
收费全文 | 5860篇 |
免费 | 91篇 |
国内免费 | 20篇 |
专业分类
教育 | 4076篇 |
科学研究 | 654篇 |
各国文化 | 33篇 |
体育 | 478篇 |
综合类 | 6篇 |
文化理论 | 45篇 |
信息传播 | 679篇 |
出版年
2023年 | 37篇 |
2022年 | 48篇 |
2021年 | 61篇 |
2020年 | 118篇 |
2019年 | 170篇 |
2018年 | 237篇 |
2017年 | 261篇 |
2016年 | 217篇 |
2015年 | 150篇 |
2014年 | 216篇 |
2013年 | 978篇 |
2012年 | 148篇 |
2011年 | 151篇 |
2010年 | 157篇 |
2009年 | 123篇 |
2008年 | 137篇 |
2007年 | 153篇 |
2006年 | 125篇 |
2005年 | 81篇 |
2004年 | 103篇 |
2003年 | 88篇 |
2002年 | 65篇 |
2001年 | 117篇 |
2000年 | 149篇 |
1999年 | 101篇 |
1998年 | 76篇 |
1997年 | 66篇 |
1996年 | 66篇 |
1995年 | 47篇 |
1994年 | 49篇 |
1993年 | 35篇 |
1992年 | 78篇 |
1991年 | 72篇 |
1990年 | 60篇 |
1989年 | 63篇 |
1988年 | 75篇 |
1987年 | 61篇 |
1986年 | 79篇 |
1985年 | 73篇 |
1984年 | 55篇 |
1983年 | 70篇 |
1982年 | 55篇 |
1981年 | 42篇 |
1979年 | 54篇 |
1978年 | 50篇 |
1977年 | 39篇 |
1976年 | 41篇 |
1975年 | 32篇 |
1974年 | 36篇 |
1973年 | 34篇 |
排序方式: 共有5971条查询结果,搜索用时 218 毫秒
751.
Investigating the temporal order of regulatory processes can explain in more detail the mechanisms behind success or lack of success during collaborative learning. The aim of this study is to explore the differences between high- and low-challenge collaborative learning sessions. This is achieved through examining how the three phases of self-regulated learning occur in a collaborative setting and the types of interaction associated with these phases. The participants were teacher training students (N?=?44), who worked in groups on a complex task related to didactics of mathematics during 6 weeks. The participants were instructed to use an application that was designed to increase awareness of the cognitive, motivational and emotional challenges the group might face. Based on the application’s log files, the sessions were categorized into low- and high-challenge sessions. The video data from each session were coded based on the self-regulation phases and the types of interaction. The frequencies of the phases and the types of interaction were calculated for each session, and process discovery methods were applied using the heuristic miner algorithm. The results show no significant differences between the sessions in the frequency of phases. However, the process models of the two sessions were different: in the high-challenge sessions, the groups switched between the forethought and performance phases more. In conclusion, the regulation phases and types of interaction that contribute to successful collaboration differ in high- and low challenge sessions and support for regulated learning is needed especially at the middle of the learning process. 相似文献
752.
Thyagaraju K. Hemavathi B. Vasundhara K. Rao A. D. Devi K. N. 《Journal of Zhejiang University. Science. B》2005,6(8):759-769
A comparative study was made on the tissue specific expression of glutathione transferases (GST) in brain and testis after
exposure of rat to phenobarbitol (PB) and β-methylcholanthrene (MC). Glutathione transferases, a family of multifunctional
proteins are involved in intracellular transport processes and in detoxication of electrophilic xenobiotics by catalyzing
reactions such as conjugation, isomerization, reduction and thiolysis. On purification, the yield of GST proteins by affinity
chromatography was 39% in testis and 32% in brain. The affinity purified testis GSTs were resolved by chromatofocusing into
six anionic and four cationic isozymes, and in brain glutathione transferases were resolved into four anionic and three cationic
isozymes, suggesting the presence of multiple isozymes with Yc, Yb, Yβ and Yδ in both of them. In testis and brain, these
isozymes at identical pI values showed variable functions with a battery of substrates and the cationic isozymes of brain
and testis showed identical properties in CHP (cumene hydroperoxide) at pH values of above 7.0. Substrate specificity studies
and immunoblot analysis of testis and brain proteins revealed that they play a predominant role in the detoxication of phenobarbitol
or β-methylcholanthrene. Expression of the isozymes in testis and brain on exposure to PB and MC indicated elevated subunit
variation. In both testis and brain, Yδ of π class was expressed on PB treatment and Yc of α class and Yβ of μ class was expressed
in MC treated testis and only Yc was predominantly expressed in MC treated brain. Thus these subunits expression is considered
as markers for carcinogenesis and specific to chemical toxicity under phenobarbitol and β-methylcholanthrene stress.
Project supported by Department of Science and Technology and Council for Scientific and Industrial Research, New Delhi 相似文献
753.
S. N. Ganguli 《Resonance》2002,7(10):30-44
In this first part of the article on LEP detector, we have described in brief the standard model for the fundamental constituents of matter. We have also described the experimental supports for the electroweak theory and quantum chromodynamics, which are the two pillars of the standard model. In the next part of the article, we will focus on the LEP detector and the measurements that have been carried out with it. 相似文献
754.
Judit N. Moschkovich 《Educational Studies in Mathematics》2004,55(1-3):49-80
This case study uses a sociocultural perspective and the concept of appropriation (Newman, Griffin and Cole, 1989; Rogoff, 1990) to describe how a student learned to work with linear functions. The analysis describes in detail the impact that interaction with a tutor had on a learner, how the learner appropriated goals, actions, perspectives, and meanings that are part of mathematical practices, and how the learner was active in transforming several of the goals that she appropriated. The paper describes how a learner appropriated two aspects of mathematical practices that are crucial for working with functions (Breidenbach, Dubinsky, Nichols and Hawks, 1992; Even, 1990; Moschkovich, Schoenfeld and Arcavi, 1993; Schwarz and Yerushalmy, 1992; Sfard, 1992): a perspective treating lines as objects and the action of connecting a line to its corresponding equation in the form y = mx + b. I use examples from the analysis of two tutoring sessions to illustrate how the tutor introduced three tasks (estimating y-intercepts, evaluating slopes, and exploring parameters) that reflect these two aspects of mathematical practices in this domain and describe how the student appropriated goals, actions, meanings, and perspectives for carrying out these tasks. I describe how appropriation functioned in terms of the focus of attention, the meaning for utterances, and the goals for these three tasks. I also examine how the learner did not merely repeat the goals the tutor introduced but actively transformed some of these goals. 相似文献
755.
Widely cited experiments on optimal foraging have used bivalued distributions as representing environmental stochasticity, characterizing these in terms of their arithmetic means. In contrast, research on free-operant choice has established that organisms prefer variable patterns of food delivery, relative to fixed patterns with the same mean values. To explore such departures from linear averaging, specifically with respect to bivalued alternatives, pigeons were given choices between a fixed-ratio (FR) schedule of food delivery that required 15, 30, or 60 responses and bivalued variable-ratio schedules with an arithmetic mean of 60,5 or 60, A bivalued schedule of 1 and 120 was preferred almost exclusively over each of the FR values. With a bivalued schedule of 15 and 105, there was a shift of preference, most notably in the FR-15 condition, but in no case was linear averaging a good predictor of the birds’ choices. Geometric averaging fared better, but even this failed to represent the apparent salience of the minimum value of the bivalued schedule in some conditions. 相似文献
756.
Based on their performance on a standardized achievement test, second-grade children (N = 49) were classified as having mathematics difficulties with normal reading achievement (MD only), both mathematics and reading difficulties (MD/RD), reading difficulties with normal mathematics achievement (RD only) and normal mathematics and reading achievement (NA). Each child was given a series of tasks so that we might assess their thinking across four areas of mathematics: number facts, story problems, place value, and written calculation. Children with MD/RD performed significantly worse than NA children in most areas of mathematical thinking, whereas children with MD only performed worse than NA children only on complex story problems. The MD-only group outperformed the MD/RD group on story problems and written calculation. No significant differences were found between the RD-only and NA groups on any of the tasks. The results suggested that among children with mathematics difficulties, the MD/RD subgroup is distinct from the MD-only subgroup, with the former being characterized by pervasive deficiencies in mathematical thinking and the latter by more specific deficits in problem solving. 相似文献
757.
Roger Säljö 《Educational Psychology Review》1991,3(2):117-126
This article is a comment on Ed Elbers' analysis of the debate between R. Gelman and R. Siegler on the development of fundamental counting competencies. An attempt is made to characterize some aspects of the theoretical positions of Gelman and Siegler. It is argued that the tendency to reduce human cognitive performance to an issue of either the application of preformed competencies of various kinds, or, alternatively, of the use of domain specific knowledge, hampers our understanding of cognitive growth and the mastery of intellectual tools. The alternative offered is that all human activity—including what takes place in the experiment — should be seen as socially and culturally situated, and that our focus should be on understanding the resources—mental as well as practical—that people draw on when solving problems. 相似文献
758.
759.
N. ALBERTI B. DI MAIO S. NOTO LA DIEGA A. BRANDOLESE 《European Journal of Engineering Education》1988,13(4):411-414
The essentials of a new Italian degree in Management Engineering are illustrated. Aspects such as engineers versus managers, educational curriculum and envisaged development of the course are discussed in some detail, including European perspectives. 相似文献
760.
A presentation of King Fahd University of Petroleum and Minerals’ (KFUPM) unique experience with the preparatory year workshop programme as a first pre-college engineering technology laboratory is given. The phases of development of the programme and its supporting laboratories are described. The technological and academic features of the programme are evaluated and conclusions and recommendations are derived from the KFUPM experience. 相似文献