全文获取类型
收费全文 | 8771篇 |
免费 | 68篇 |
国内免费 | 7篇 |
专业分类
教育 | 6474篇 |
科学研究 | 728篇 |
各国文化 | 147篇 |
体育 | 526篇 |
综合类 | 5篇 |
文化理论 | 105篇 |
信息传播 | 861篇 |
出版年
2021年 | 55篇 |
2020年 | 84篇 |
2019年 | 155篇 |
2018年 | 207篇 |
2017年 | 237篇 |
2016年 | 220篇 |
2015年 | 171篇 |
2014年 | 216篇 |
2013年 | 2047篇 |
2012年 | 172篇 |
2011年 | 192篇 |
2010年 | 182篇 |
2009年 | 158篇 |
2008年 | 200篇 |
2007年 | 205篇 |
2006年 | 188篇 |
2005年 | 191篇 |
2004年 | 177篇 |
2003年 | 154篇 |
2002年 | 147篇 |
2001年 | 126篇 |
2000年 | 126篇 |
1999年 | 133篇 |
1998年 | 113篇 |
1997年 | 117篇 |
1996年 | 118篇 |
1995年 | 147篇 |
1994年 | 121篇 |
1993年 | 106篇 |
1992年 | 114篇 |
1991年 | 106篇 |
1990年 | 102篇 |
1989年 | 107篇 |
1988年 | 98篇 |
1987年 | 96篇 |
1986年 | 88篇 |
1985年 | 99篇 |
1984年 | 105篇 |
1983年 | 99篇 |
1982年 | 109篇 |
1981年 | 82篇 |
1980年 | 61篇 |
1979年 | 74篇 |
1978年 | 77篇 |
1977年 | 85篇 |
1976年 | 67篇 |
1975年 | 56篇 |
1974年 | 59篇 |
1973年 | 60篇 |
1971年 | 44篇 |
排序方式: 共有8846条查询结果,搜索用时 15 毫秒
161.
As the costs of certain types of scientific research have escalated and as growth rates in overall national science budgets have declined, so the need for an explicit science policy has grown more urgent. In order to establish priorities between research groups competing for scarce funds, one of the most important pieces of information needed by science policy-makers is an assessment of those groups' recent scientific performance. This paper suggests a method for evaluating that performance.After reviewing the literature on scientific assessment, we argue that, while there are no simple measures of the contributions to scientific knowledge made by scientists, there are a number of ‘partial indicators’ — that is, variables determined partly by the magnitude of the particular contributions, and partly by ‘other factors’. If the partial indicators are to yield reliable results, then the influence of these ‘other factors’ must be minimised. This is the aim of the method of ‘converging partial indicators’ proposed in this paper. We argue that the method overcomes many of the problems encountered in previous work on scientific assessment by incorporating the following elements: (1) the indicators are applied to research groups rather than individual scientists; (2) the indicators based on citations are seen as reflecting the impact, rather than the quality or importance, of the research work; (3) a range of indicators are employed, each of which focusses on different aspects of a group's performance; (4) the indicators are applied to matched groups, comparing ‘like’ with ‘like’ as far as possible; (5) because of the imperfect or partial nature of the indicators, only in those cases where they yield convergent results can it be assumed that the influence of the ‘other factors’ has been kept relatively small (i.e. the matching of the groups has been largely successful), and that the indicators therefore provide a reasonably reliable estimate of the contribution to scientific progress made by different research groups.In an empirical study of four radio astronomy observatories, the method of converging partial indicators is tested, and several of the indicators (publications per researcher, citations per paper, numbers of highly cited papers, and peer evaluation) are found to give fairly consistent results. The results are of relevance to two questions: (a) can basic research be assessed? (b) more specifically, can significant differences in the research performance of radio astronomy centres be identified? We would maintain that the evidence presented in this paper is sufficient to justify a positive answer to both these questions, and hence to show that the method of converging partial indicators can yield information useful to science policy-makers. 相似文献
162.
R Abraham M Joseph John R Calton J Dhanoa 《Indian journal of clinical biochemistry : IJCB》2006,21(1):95-100
Homocysteine(Hcy) has been implicated as a novel risk factor of Coronary Artery Disease (CAD) among Asian Indians, but many
studies done in India failed to reveal any direct correlation. It has also been reported that Folic acid and Vitamin B12 levels
inversely affect serum levels of homocysteine. In this study, we looked at the levels of homocysteine among patients with
CAD. The effect of Vitamin B12, Folate and other risk factors on homocysteine levels were also evaluated. Mean homocysteine
levels in cases (22.81±13.9, n=70) were significantly higher (p=<0.001) than the controls (7.77±7.3, n=70). However no statistically
significant correlation could be deduced between homocysteine Vitamin B12, and Folate. Cumulative analysis have indicated
an increase in homocysteine levels among patients with CAD with every additional risk factor. 相似文献
163.
Measuring innovative performance: is there an advantage in using multiple indicators? 总被引:10,自引:0,他引:10
The innovative performance of companies has been studied quite extensively and for a long period of time. However, the results of many studies have not yet led to a generally accepted indicator of innovative performance or a common set of indicators. So far the variety in terms of constructs, measurements, samples, industries and countries has been substantial. This paper studies the innovative performance of a large international sample of nearly 1200 companies in four high-tech industries, using a variety of indicators. These indicators range from R&D inputs, patent counts and patent citations to new product announcements. The study establishes that a composite construct based on these four indicators clearly catches a latent variable ‘innovative performance’. However, our findings also suggest that the statistical overlap between these indicators is that strong that future research might also consider using any of these indicators to measure the innovative performance of companies in high-tech industries. 相似文献
164.
Ji Shen Patrick C. Gibbons John F. Wiegers Ann P. McMahon 《Journal of Science Teacher Education》2007,18(3):431-459
We present a practical way of adapting and using four research-based assessments for different purposes in an electricity
and magnetism course for K-8 science teachers. The course is designed to accomplish conceptual change toward accepted scientific
conceptions as well as introducing teachers to materials and activities appropriate for their classrooms. Our data support
that using the research-based tests to identify alternative conceptions and discuss test results with teachers is a promising
way to use the knowledge of alternative conceptions in professional development. We also identify some mismatches between
the research of conceptual change and its use in programs of professional development.
相似文献
Ji ShenEmail: |
165.
166.
167.
168.
One hundred thirty-eight fifth-grade students from three upstate New York school districts were administered a 1930s version of the Pintner General Ability Tests: Verbal Series. Scores from this test were compared and correlated with scores from current IQ and achievement tests. The Pintner means were similar to those of the current IQ tests; the correlations of the Pintner with the other tests were of the same order as those typically reported among contemporary measures; and item difficulty, as indicated by rank order, appeared similar for the current sample and the 1930s norm groups. The findings are discussed with reference to research that has shown sharp increases in IQs of Americans since the 1930s and questions concerning changes in mental ability measures. 相似文献
169.
170.
Instructional design, as it is traditionally conceptualized, is being challenged on several fronts, through surveys of design practice, cross-disciplinary studies of design practice, and practical criticism focusing on issues of design models' flexibility and efficiency. Collectively these challenges raise questions about the viability of the instructional design enterprise. This paper reviews these challenges and attempts to respond by offering alternative approaches to instructional design. 相似文献