全文获取类型
收费全文 | 581篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
教育 | 276篇 |
科学研究 | 275篇 |
各国文化 | 3篇 |
体育 | 2篇 |
文化理论 | 3篇 |
信息传播 | 32篇 |
出版年
2024年 | 1篇 |
2023年 | 8篇 |
2022年 | 7篇 |
2021年 | 21篇 |
2020年 | 5篇 |
2019年 | 13篇 |
2018年 | 39篇 |
2017年 | 28篇 |
2016年 | 27篇 |
2015年 | 32篇 |
2014年 | 31篇 |
2013年 | 55篇 |
2012年 | 16篇 |
2011年 | 25篇 |
2010年 | 26篇 |
2009年 | 29篇 |
2008年 | 25篇 |
2007年 | 21篇 |
2006年 | 29篇 |
2005年 | 22篇 |
2004年 | 14篇 |
2003年 | 25篇 |
2002年 | 12篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 12篇 |
1997年 | 6篇 |
1996年 | 3篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有591条查询结果,搜索用时 15 毫秒
1.
2.
3.
Vandana Tiwari Jyotsna Agarwal Anumesh Kumar Pathak Shivani Singh 《Indian journal of clinical biochemistry : IJCB》2023,38(2):212
Immune dysregulation is a key feature of the coronavirus disease-2019 (COVID-19). However, disparities in responses across ethnic groups are underappreciated. This study aimed to determine the relationship between chemokines and cytokines and the severity of COVID-19. Multiplex magnetic bead-based Luminex-100 was used to assess chemokine and cytokine levels in COVID-19 patients at admission (day-1) and after 4 days. The mean age of the patients recruited was 54.3 years, with 19 (63.3%) males. COVID-19 patients had significantly lower lymphocyte, monocyte, hemoglobin and eosinophil levels than controls (p < 0.05). COVID-19 patients showed significantly higher neutrophil levels than controls (p < 0.05). The baseline levels of IL-2, IL-6, IL-8, IL-10, and IFN-α/γ significantly increased in COVID-19 patients (p < 0.05). Chemokine levels (IP-10, MCP-1, MIG, and CCL-5) were significantly in COVID-19 patients. IL-8, IP-10, and MIG levels were significantly higher in the patients with severe COVID-19 (p < 0.05). Individuals with mild COVID-19 showed significantly higher levels of INF-α, IL-2, IL-6, and IL-8, whereas IL-10 levels were significantly lower (p < 0.05). TNF-levels decreased significantly in individuals with severe COVID-19, whereas IL-6, IL-8, and MIG levels increased (p < 0.05). After 4 days, INFα-, IL-2, IL-6, IL-8, IP-10, and MIG levels were significantly higher in patients with mild disease, whereas IL-6, MIG, and TNF-αlevels were significantly higher in patients with severe disease (p < 0.05). Thus, we conclude that COVID-19 is characterized by INF-α/γ, IL-6, IL-10, IP-10, MCP-1, MIG, and CCL5 dysregulation. IL-8, MIG, and IP-10 levels distinguish between moderate and severe COVID-19. Changes in INF-α, IL-2, IL-6, IL-8, IP-10, and MIG levels can be used to monitor disease progression.Supplementary InformationThe online version contains supplementary material available at 10.1007/s12291-022-01108-x. 相似文献
4.
5.
Sandip Sinharay 《Educational Measurement》2016,35(3):38-54
Data mining methods for classification and regression are becoming increasingly popular in various scientific fields. However, these methods have not been explored much in educational measurement. This module first provides a review, which should be accessible to a wide audience in education measurement, of some of these methods. The module then demonstrates using three real‐data examples that these methods may lead to an improvement over traditionally used methods such as linear and logistic regression in educational measurement. 相似文献
6.
Objective: A natural cyclic peptide previously isolated from Citrus medica was synthesized by coupling oftetrapep-tide units Boc-Leu-Pro-Trp-Leu-Ome and Boc-Ile-Ala-Ala-Gly-Ome after proper deprotection at carboxyl and amino terminals followed by cyclization of linear octapeptide segment.Methods: Solution phase technique was adopted for the synthesis of cyclooctapeptide--sarcodactylamide.Required tetrapeptide units were prepared by coupling of Boc-protected dipeptides viz.Boc-Leu-Pro-OH and Boc-Ile-Ala-OH with respective dipeptide methyl esters Trp-Leu-Ome and Ala-Gly-Ome.Cyclization of linear octapeptide unit was done by p-nitrophenyl ester method.The structure of synthesized cyclopolypeptide was elucidated by FTIR,1H NMR,13C NMR,FABMS spectral data and elemental analysis.The newly synthesized peptide was evaluated for dif-ferent pharmacological activities including antimicrobial,anthelmintic and cytotoxic activities.Results: Synthesis of sarcodac-tylamide was accomplished with >78% yield utilizing dicyclohexylcarbodiimide (DCC) as coupling agent.Newly synthesized peptide possessed potent cytotoxic activity against Dalton's lymphoma ascites (DLA) and Ehrlich's ascites carcinoma (EAC) cell lines,in addition to moderate anthelmintic activity against earthworms Megascoplex konkanensis,Pontoscotex corethruses and Eudrilus sp.Moreover,cyclopolypeptide displayed good antimicrobial activity against pathogenic fungi Candida albicans and Gram-negative bacteria Pseudomonas aeruginosa,in comparison to standard drugs griseofulvin and ciprofloxacin.Conclusion: Solution phase technique employing DCC and triethylamine (TEA) as base proved to be effective for the synthesis of natural cyclooctapeptide.N-methyl morpholine (NMM) was found to be a better base for the cyclization of linear octapeptide unit in comparison to TEA and pyridine. 相似文献
7.
Pradeep Kumar 《Resonance》2017,22(4):399-405
Richard Feynman once said: “nobody understands quantum mechanics”. Still, those who devised it are perhaps the ones closest to understanding their creation. It suggests that whenever the weirdness of quantum mechanics haunts you, it is better to go back to its creators in terms of their original publications. In the present article, the author has tried to seek help from Heisenberg’s 1925 paper, in order to reduce the weirdness of going from classical observables to quantum operators. 相似文献
8.
Very few empirical studies have investigated programmes in which doctoral students act as peer facilitators in faculty writing groups. We report on the development of a centrally delivered doctoral student writing programme in which twenty student participants were mentored and provided with the resources to initiate their own faculty-based doctoral writing groups. ‘Legitimate peripheral participation’ was used as a conceptual lens to interpret the data collected during the establishment and evaluation of the programme. All student participants in the preparatory training course, which was developed in consultation with postgraduate students and research supervisors, went on to become doctoral writing peer facilitators of peer writing groups. Insights from seven of these showed how a well-structured and supportive programme harnessed the benefits of peer learning by bringing personal rewards to participants and building institutional capacity around doctoral research writing literacies. 相似文献
9.
This paper reports research on the effects of variations in injection velocity and permeability on the heat transfer and flow
through a highly porous medium between two horizontal parallel plates situated at constant distance with constant suction
by the upper plate. Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.
The governing equations are solved by adopting complex variable notations to obtain the expressions for the velocity and temperature
field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs. 相似文献
10.
David Devraj Kumar P. V. Thomas John D. Morris Karen M. Tobias Mary Baker Trudy Jermanovich 《Journal of Science Education and Technology》2011,20(2):116-115
This study examined the impact of computer simulation and supported science learning on a teacher’s understanding and conceptual
knowledge of current electricity. Pre/Post tests were used to measure the teachers’ concept attainment. Overall, there was
a significant and large knowledge difference effect from Pre to Post test. Two interesting interactions were observed during
the data analysis. The first was the difference between Elementary and Secondary teachers. Both groups had significant gains,
with large effect sizes, but the Elementary teachers (Pre-Mean = 3.70, Post-Mean = 7.51) started lower and ended higher exhibiting
a significantly larger gain than the Secondary teachers (Pre-Mean = 4.96, Post-Mean = 6.71). The second interaction was the
impact of gender. Both groups showed significant gains, with large effect sizes, but females (Pre-Mean = 3.90, Post-Mean = 7.21)
gained significantly more than males (Pre-Mean = 5.13, Post-Mean = 7.01). These results confirm that computer simulation supported
science learning can have a positive effect on concept attainment in teachers. 相似文献