全文获取类型
收费全文 | 3856篇 |
免费 | 25篇 |
国内免费 | 4篇 |
专业分类
教育 | 2759篇 |
科学研究 | 487篇 |
各国文化 | 20篇 |
体育 | 174篇 |
综合类 | 6篇 |
文化理论 | 79篇 |
信息传播 | 360篇 |
出版年
2023年 | 4篇 |
2022年 | 16篇 |
2021年 | 21篇 |
2020年 | 25篇 |
2019年 | 43篇 |
2018年 | 111篇 |
2017年 | 151篇 |
2016年 | 214篇 |
2015年 | 96篇 |
2014年 | 71篇 |
2013年 | 267篇 |
2012年 | 95篇 |
2011年 | 208篇 |
2010年 | 121篇 |
2009年 | 162篇 |
2008年 | 80篇 |
2007年 | 90篇 |
2006年 | 90篇 |
2005年 | 719篇 |
2004年 | 571篇 |
2003年 | 318篇 |
2002年 | 104篇 |
2001年 | 63篇 |
2000年 | 36篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 7篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1991年 | 8篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 11篇 |
1986年 | 4篇 |
1985年 | 8篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 4篇 |
1979年 | 7篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1973年 | 6篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 4篇 |
1966年 | 3篇 |
排序方式: 共有3885条查询结果,搜索用时 31 毫秒
81.
The predictive value of rime spellings in English was compared directly to other types of regularities beyond the level of the single letter. A computer-assisted analysis of a list of twenty-four thousand written words, each paired with its corresponding pronunciation, reveals that only a small number of rime spellings are highly regular in their pronunciations. The conventional division of vowel letter pronunciations into short and long in closed and open written syllables is the most reliable key to English pronunciation. Our findings support the notion that English spelling is based at least in part on syllable structure. In addition, prefixes and suffixes provide very reliable clues to pronunciation, which suggests that their regularity should be exploited in the teaching of reading. 相似文献
82.
Village Elders’ and Secondary School Students’ Explanations of Natural Phenomena in Papua New Guinea
Soikava?Pauka David?F.?TreagustEmail author Bruce?Waldrip 《International Journal of Science and Mathematics Education》2005,3(2):213-238
This research investigated the sources of explanations and understanding of natural phenomena in terms of the students’ cultural and school science experiences. The first phase involved interviews with eight village elders that probed their explanations and understanding of natural phenomena. The second phase involved the design, development and administration of two questionnaires on natural phenomena to 179 students in a rural boarding high school in Papua New Guinea (PNG). Most village elders gave explanations of many of the phenomena in terms of spirits, spells, magic, religion, and personal experiences. Most school-aged students choose scientific explanations of natural phenomena in terms of what they had learned in school or from personal experiences. However, many choose explanations of the same phenomena about spirits, spells and magic that came from the village, family or home. The study revealed that students’ ideas about natural phenomena are strongly governed and controlled by their school science knowledge in the school setting. It is likely that their own traditional knowledge cannot be identified in a school setting but that questionnaires in the students’ local language be given to students in their villages (as opposed to school). In addition, so as not to diminish the value of this traditional knowledge, science education programs are needed that are able to consider and harmonise traditional knowledge with school science. 相似文献
83.
Carcinogenic and mutagenic polycyclic aromatic hydrocarbons (PAHs) generated in coal combustion have caused great environmental health concern. Seventeen PAHs (16 high priority PAHs recommended by USEPA plus Benzo[e]pyrene) present in five raw bituminous coals and released during bituminous coal combustion were studied. The effects of combustion temperature, gas atmosphere, and chlorine content of raw coal on PAHs formation were investigated. Two additives (copper and cupric oxide) were added when the coal was burned. The results indicated that significant quantities of PAHs were produced from incomplete combustion of coal pyrolysis products at high temperature, and that temperature is an important causative factor of PAHs formation. PAHs concentrations decrease with the increase of chlorine content in oxygen or in nitrogen atmosphere. Copper and cupric oxide additives can promote PAHs formation (especially the multi-ring PAHs) during coal combustion. 相似文献
84.
This paper addresses a neglected topic in the knowledge management literature: how the size of a network of actors affects the nature of intra-network social relations and knowledge processes. It makes a theoretical contribution to developing understanding in this area drawing on a range of literatures including practice-based perspectives on knowledge, the literature on the embeddedness of social relations, and relevant knowledge management literature. The central focus of this paper is on the relationship between network size, network density, and how these variables affect intra-network knowledge processes. It suggests that as network size increases network density is likely to decrease (as it becomes problematic for the actors in such networks to retain strong ties with a significant proportion of the network's members), which it will be suggested has significant ramifications for intra-network knowledge processes. This paper concludes by reflecting on the implications of the ideas developed for network-based forms of organizing, and innovation processes. 相似文献
85.
Eric Von Hippel 《Research Policy》1982,11(2):95-115
It has been empirically observed that, in some industries product users are the most frequent sources of product innovations while, in other industries, product manufacturers are. I hypothesize that such differences are caused by differences in the ability of these two “functional” categories of innovators to appropriate innovation benefit. I explore this hypothesis by examining the real-world effectiveness of mechanisms (such as patents and lead time) used for the appropriation of innovation benefit and the dependence of this effectiveness on the functional relationship between innovator and innovation. 相似文献
86.
Surapon?TangvarasittichaiEmail author Patcharin?Pingmuanglaew Orathai?Tangvarasittichai 《Indian journal of clinical biochemistry : IJCB》2016,31(4):446-451
Hypertension is the most common cardiovascular risk factor. Lipoprotein(a) [Lp(a)], inflammation, oxidative stress and chronic kidney disease (CKD) exacerbate the response to tissue injury and acts as markers of the vascular disease, especially in glomerulosclerosis. We compared the clinical characteristics of 138 non-diabetes hypertensive women (ndHT) patients with 417 non-diabetes normotensive subjects and tested the association of hypertension with Lp(a), inflammation, CKD and oxidative stress by using multiple logistic regression. BP, BMI, waist circumference, creatinine, Lp(a), inflammation and malondialdehyde levels were significantly higher and CKD state in the ndHT patients (p < 0.05). Multiple logistic regression showed hypertension associated with increased Lp(a), inflammation, ORs and 95 % CIs were 2.52 (1.33, 4.80), 2.75 (1.44, 5.27) after adjusting for their covariates. Elevated serum Lp(a) and inflammation levels concomitants with increased oxidative stress and CKD were the major risk factors associated with hypertension and implications for the increased risk of HT and vascular disease. 相似文献
87.
Relative efficiency of R&D activities: A cross-country study accounting for environmental factors in the DEA approach 总被引:1,自引:0,他引:1
This paper applies the production framework associated with the data envelopment analysis (DEA) method to evaluate the relative efficiency of R&D activities across countries. R&D capital stocks and manpower are treated as inputs while patents and academic publications are considered as outputs. A three-stage approach, which involves using DEA for evaluating efficiency and using Tobit regressions for controlling the external environment, is applied to 30 countries in recent years. The results show that less than one-half of the countries are fully efficient in R&D activities and that more than two-thirds are at the stage of increasing returns to scale. Most countries have a more significant advantage in producing SCI cum EI publications than in generating patents. 相似文献
88.
Evrikleia?Tsagala Maria?KordakiEmail author 《Education and Information Technologies》2007,12(4):281-295
This paper aims to determine the factors affecting the decisions of both male and female secondary school pupils whether or
not to pursue undergraduate studies in Computing. It is based on research conducted in Greece, on a sample of 248 pupils,
135 of whom were female. All were aged 17 and about to decide on their future undergraduate studies. Questionnaires were used,
addressing issues in the following four main categories: a) the reasons pupils chose/rejected Computing, b) how family and
friends, the media and the school environment contribute to their decision, c) how pupils perceived their future after studying
Computing and d) how pupils perceived the profile of a computer professional in terms of gender.
相似文献
Maria KordakiEmail: |
89.
Marital conflict and conduct problems in Children of Twins 总被引:3,自引:0,他引:3
Harden KP Turkheimer E Emery RE D'Onofrio BM Slutske WS Heath AC Martin NG 《Child development》2007,78(1):1-18
The Children-of-Twins design was used to test whether associations between marital conflict frequency and conduct problems can be replicated within the children of discordant twin pairs. A sample of 2,051 children (age 14-39 years) of 1,045 twins was used to estimate the genetic and environmental influences on marital conflict and determine whether genetic or environmental selection processes underlie the observed association between marital conflict and conduct problems. Results indicate that genetic and nonshared environmental factors influence the risk of marital conflict. Furthermore, genetic influences mediated the association between marital conflict frequency and conduct problems. These results highlight the need for quasiexperimental designs in investigations of intergenerational associations. 相似文献
90.
We document some basic facts about how liquids behave in the low gravity of outer space and how this poses challenges to space
scientists and engineers who need to design and test systems that handle fluids in outer space while working in the 1-g environment
on Earth.
N Ananthkrishnan is Director, Coral Digital Technologies (P) Ltd, a Bangalore-based company working in the area of multidisciplinary
simulation and system integration of aerospace, naval and surface vehicles, and in the design and development of autonomous
unmanned/micro air vehicles. 相似文献