全文获取类型
收费全文 | 1613篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
教育 | 1111篇 |
科学研究 | 97篇 |
各国文化 | 36篇 |
体育 | 190篇 |
综合类 | 2篇 |
文化理论 | 22篇 |
信息传播 | 186篇 |
出版年
2024年 | 2篇 |
2023年 | 9篇 |
2022年 | 20篇 |
2021年 | 23篇 |
2020年 | 49篇 |
2019年 | 82篇 |
2018年 | 92篇 |
2017年 | 92篇 |
2016年 | 78篇 |
2015年 | 57篇 |
2014年 | 67篇 |
2013年 | 379篇 |
2012年 | 56篇 |
2011年 | 54篇 |
2010年 | 49篇 |
2009年 | 43篇 |
2008年 | 46篇 |
2007年 | 53篇 |
2006年 | 41篇 |
2005年 | 32篇 |
2004年 | 35篇 |
2003年 | 20篇 |
2002年 | 28篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 13篇 |
1998年 | 11篇 |
1997年 | 17篇 |
1996年 | 11篇 |
1995年 | 15篇 |
1994年 | 8篇 |
1993年 | 4篇 |
1992年 | 16篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 9篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 4篇 |
1985年 | 7篇 |
1984年 | 14篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 2篇 |
1967年 | 3篇 |
1955年 | 1篇 |
排序方式: 共有1644条查询结果,搜索用时 15 毫秒
71.
Christopher R. Phaneuf Nikita Pak D. Curtis Saunders Gregory L. Holst Joav Birjiniuk Nikita Nagpal Stephen Culpepper Emily Popler Andi L. Shane Robert Jerris Craig R. Forest 《Biomicrofluidics》2015,9(4)
Amplification of multiple unique genetic targets using the polymerase chain reaction (PCR) is commonly required in molecular biology laboratories. Such reactions are typically performed either serially or by multiplex PCR. Serial reactions are time consuming, and multiplex PCR, while powerful and widely used, can be prone to amplification bias, PCR drift, and primer-primer interactions. We present a new thermocycling method, termed thermal multiplexing, in which a single heat source is uniformly distributed and selectively modulated for independent temperature control of an array of PCR reactions. Thermal multiplexing allows amplification of multiple targets simultaneously—each reaction segregated and performed at optimal conditions. We demonstrate the method using a microfluidic system consisting of an infrared laser thermocycler, a polymer microchip featuring 1 μl, oil-encapsulated reactions, and closed-loop pulse-width modulation control. Heat transfer modeling is used to characterize thermal performance limitations of the system. We validate the model and perform two reactions simultaneously with widely varying annealing temperatures (48 °C and 68 °C), demonstrating excellent amplification. In addition, to demonstrate microfluidic infrared PCR using clinical specimens, we successfully amplified and detected both influenza A and B from human nasopharyngeal swabs. Thermal multiplexing is scalable and applicable to challenges such as pathogen detection where patients presenting non-specific symptoms need to be efficiently screened across a viral or bacterial panel. 相似文献
72.
The use of structural equation modeling (SEM) in communication research has become increasingly popular in recent years, with SEM being commonly used as the primary method of data analysis in studies published within the field’s journals. However, despite its widespread use, there are persistent misapplications of SEM in published empirical studies in the communication sciences. Of these types of misuse, the most troubling are those related to the exploitation of flexibilities in data collection and analysis. Given the number of decisions that must be made when analyzing and reporting structural equation models, decisions which often remain undisclosed, the potential for researchers to exploit flexibilities in SEM research is high. To assess the extent of this problem, as well as the more longstanding types of misuse (i.e., omission of information and disclosed “bad practice”) identified by prior studies, we undertake a methodical review of studies employing structural equation modeling within major journals in the field of communication between the years 2007 and 2011. Articles were coded on the characteristics of the sample, characteristics of the model tested, as well as for various potential problems that we defined a priori. The most serious issues are identified, and recommendations for future standards in SEM research are suggested. 相似文献
73.
74.
75.
76.
Justin X. Nicoll Andrew J. Galpin Donald B. Thomason Christopher A. Moore 《European Journal of Sport Science》2017,17(9):1194-1202
Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels. 相似文献
77.
Jill J. Martin Christopher H. Skinner Christine E. Neddenriep 《Psychology in the schools》2001,38(4):391-400
Researchers have shown that students' perceptions of mathematics assignments could be improved by interspersing additional briefer, easier problems (e.g., Logan and Skinner, 1998). The current study was designed to extend this research to reading tasks. Seventh‐grade students read out loud both a control passage and a similar experimental passage that contained additional interspersed brief (i.e., 16 words), easy (i.e., first‐grade reading level) paragraphs. Students then selected the passage that would require the least effort to read and the least time to read. Students also indicated the passage they liked most (preference) and the passage that they would like to read again (choice). Significantly more students selected the control passage as requiring less time to read, but no differences were found for preference, choice, or effort selections. The results failed to confirm earlier research on the interspersal procedure, thus our findings have applied and theoretical implications regarding causal variables that may account for the effectiveness of the interspersal procedure. Specifically, the current study suggests that the interspersal procedure may improve assignment perception only when the procedure increases discrete task‐completion rates. © 2001 John Wiley & Sons, Inc. 相似文献
78.
Sarah Lam Susan Tracz Christopher Lucey 《International journal for the advancement of counseling》2013,35(3):172-187
This study explored the counselling self-efficacy of students in a counsellor education programme, in regard to age, gender, and ethnicity characteristics. To assess counselling self-efficacy, the Counselling Self-Estimate Inventory (COSE) of Larson et al. (Counsellor Education & Supervision 41: 120–130, 1992) was administered at the end of a semester to counselling students engaged in different stages of a counsellor training program. No significant differences were found in regard to gender and age-group categories, but significant differences were found among ethnic groups. It was found that Asian and White students generally had similar and also lower counselling self-efficacy means than the other ethnic groups in the sample in regard to several counselling-specific categories. Implications for counsellor educators in training counselling students of diverse characteristics are discussed. 相似文献
79.
Laura E. Hume Christopher J. Lonigan Jessica D. McQueen 《Journal of Research in Reading》2015,38(2):172-193
This study examined how children's literacy interests related to parent literacy‐promoting practices across time. Using a sample of 909 preschool‐age children and the newly developed Child Activities Preference Checklist, literacy interest appeared to be a complex construct, not easily captured by a single measure. In a subsample of 230 children with longitudinal data, parent literacy practices and child literacy interests related concurrently and across time. Parent literacy practices were more stable than child literacy interests, with children's literacy interest continuing to develop over the preschool year. Parent practices of exposing children to literacy and teaching them literacy concepts appeared to be distinct constructs. Exposure to literacy was especially important in the growth of literacy interests and the hypothesis that exposure has a negative effect on children with little initial interest was not fully supported. 相似文献
80.