全文获取类型
收费全文 | 239篇 |
免费 | 10篇 |
国内免费 | 1篇 |
专业分类
教育 | 121篇 |
科学研究 | 84篇 |
各国文化 | 3篇 |
体育 | 11篇 |
文化理论 | 2篇 |
信息传播 | 29篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 10篇 |
2020年 | 11篇 |
2019年 | 9篇 |
2018年 | 31篇 |
2017年 | 18篇 |
2016年 | 10篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 20篇 |
2012年 | 13篇 |
2011年 | 11篇 |
2010年 | 9篇 |
2009年 | 17篇 |
2008年 | 12篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2001年 | 2篇 |
1999年 | 1篇 |
1998年 | 3篇 |
1994年 | 1篇 |
1988年 | 1篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有250条查询结果,搜索用时 31 毫秒
211.
Shayan A. Tabrizi Azadeh Shakery Hamed Zamani Mohammad Ali Tavallaei 《Information processing & management》2018,54(4):630-656
Despite the importance of personalization in information retrieval, there is a big lack of standard datasets and methodologies for evaluating personalized information retrieval (PIR) systems, due to the costly process of producing such datasets. Subsequently, a group of evaluation frameworks (EFs) have been proposed that use surrogates of the PIR evaluation problem, instead of addressing it directly, to make PIR evaluation more feasible. We call this group of EFs, indirect evaluation frameworks. Indirect frameworks are designed to be more flexible than the classic (direct) ones and much cheaper to be employed. However, since there are many different settings and methods for PIR, e.g., social-network-based vs. profile-based PIR, and each needs some special kind of data to do the personalization based on, not all the evaluation frameworks are applicable to all the PIR methods. In this paper, we first review and categorize the frameworks that have already been introduced for evaluating PIR. We further propose a novel indirect EF based on citation networks (called PERSON), which allows repeatable, large-scale, and low-cost PIR experiments. It is also more information-rich compared to the existing EFs and can be employed in many different scenarios. The fundamental idea behind PERSON is that in each document (paper) d, the cited documents are generally related to d from the perspective of d’s author(s). To investigate the effectiveness of the proposed EF, we use a large collection of scientific papers. We conduct several sets of experiments and demonstrate that PERSON is a reliable and valid EF. In the experiments, we show that PERSON is consistent with the traditional Cranfield-based evaluation in comparing non-personalized IR methods. In addition, we show that PERSON can correctly capture the improvements made by personalization. We also demonstrate that its results are highly correlated with those of another salient EF. Our experiments on some issues about the validity of PERSON also show its validity. It is also shown that PERSON is robust w.r.t. its parameter settings. 相似文献
212.
Rami Zurayk Mutasem El-Fadel Iman Nuwayhid 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2010,47(5):299-314
The American University of Beirut’s Interfaculty Graduate Environmental Sciences Program was launched in 1997 as a means of
addressing salient issues on the environment and development in Lebanon and the Arab World using an interdisciplinary approach.
The programme adopts a student-centred learning approach and aims to develop critical and systems thinking skills to produce
socially and environmentally conscious leaders and agents of change in the Arab World. In this paper, we provide an evaluation
of the programme’s ESD dimensions using the criteria of interdisciplinarity, local relevance and competence-based learning.
This is followed by a critical analysis of the programme’s potential for use as a model in the Arab World. We find that, while
the model may be useful in providing inspiration and a good practice case, its transfer “as is” to institutions of higher
education in the Arab World or even in Lebanon is unlikely, and perhaps undesirable, in view of the inherently diverse nature
of Arab universities. 相似文献
213.
In the present work, the fruits of four Morus species, namely Morus alba (white mulberry), Morus nigra (black mulberry), Morus laevigata (large white fruit), and Morus laevigata (large black fruit), were analyzed for proximate composition, essential minerals, and antioxidant potentials. For this purpose,
the ripe fruits were collected from the northern regions of Pakistan. The major nutritional components (moisture, ash, lipids,
proteins, fibres, carbohydrates, and total sugar) were found to be in the suitable range along with good computed energy.
Total dry weight, pH, and titratable acidity (percent citric acid) were (17.60±1.94)–(21.97±2.34) mg/100 g, (3.20±0.07)–(4.78±0.15),
and (0.84±0.40)%–(2.00±0.08)%, respectively. Low riboflavin (vitamin B2) and niacin (vitamin B3) contents were recorded in all the fruits, while ascorbic acid (vitamin C) was in the range from (15.20±1.25) to (17.03±1.71)
mg/100 g fresh weight (FW). The mulberry fruits were rich with regard to the total phenol and alkaloid contents, having values
of (880±7.20)–(1650±12.25) mg/100 g FW and (390±3.22)–(660±5.25) mg/100 g FW, respectively. Sufficient quantities of essential
macro-(K, Ca, Mg, and Na) and micro-(Fe, Zn, and Ni) elements were found in all the fruits. K was the predominant element
with concentration ranging from (1270±9.36) to (1731±11.50) mg/100 g, while Ca, Na, and Mg contents were (440±3.21)–(576±7.37),
(260±3.86)–(280±3.50), and (240±3.51)–(360±4.20) mg/100 g, respectivly. The decreasing order of micro-minerals was Fe>Zn>Ni.
The radical scavenging activity of methanolic extract of fruits was concentration-dependent and showed a correlation with
total phenolic constituents of the respective fruits. Based on the results obtained, mulberry fruits were found to serve as
a potential source of food diet and natural antioxidants. 相似文献
214.
Cell-secreted soluble factor signaling in a diffusion dominant microenvironment plays an important role on early stage differentiation of pluripotent stem cells invivo. In this study, we utilized a membrane-based two-chambered microbioreactor (MB) to differentiate mouse embryonic stem cells (mESCs) in a diffusion dominant microenvironment of the top chamber while providing enough nutrient through the bottom chamber. Speculating that accumulated FGF4 in the small top chamber will augment neuronal differentiation in the MB culture, we first differentiated mESCs for 8 days by using a chemically optimized culture medium for neuronal induction. However, comparison of cellular morphology and expression of neuronal markers in the MB with that in the 6-well plate (6WP) indicated relatively lower neuronal differentiation in the MB culture. Therefore, to investigate whether microenvironment in the MB facilitates non-neuronal differentiation, we differentiated mESCs for 8 days by using chemically defined basal medium. In this case, differentiated cell morphology differed markedly between the MB and 6WP cultures: epithelial sheet-like morphology in the MB, whereas rosette morphology in the 6WP. Expression of markers from the three germ layers indicated lower neuronal but higher meso- and endo-dermal differentiation of mESCs in the MB than the 6WP culture. Moreover, among various cell-secreted soluble factors, BMP4 expression was remarkably upregulated in the MB culture. Inhibition of BMP4 signaling demonstrated that enhanced effect of upregulated BMP4 was responsible for the prominent meso- and endo-dermal differentiation in the MB. However, in the 6WP, downregulated BMP4 had a minimal influence on the differentiation behavior. Our study demonstrated utilization of a microbioreactor to modulate the effect of cell-secreted soluble factors by autoregulation and thereby inducing alternative self-capability of mESCs. Understanding and implementation of autoregulation of soluble factors similar to this study will lead to the development of robust culture systems to control ESC behavior. 相似文献
215.
Badami R VaezMousavi M Wulf G Namazizadeh M 《Research quarterly for exercise and sport》2012,83(2):196-203
One purpose of the present study was to examine whether self-confidence or anxiety would be differentially affected byfeedback from more accurate rather than less accurate trials. The second purpose was to determine whether arousal variations (activation) would predict performance. On day 1, participants performed a golf putting task under one of two conditions: one group received feedback on the most accurate trials, whereas another group received feedback on the least accurate trials. On day 2, participants completed an anxiety questionnaire and performed a retention test. Shin conductance level, as a measure of arousal, was determined. The results indicated that feedback about more accurate trials resulted in more effective learning as well as increased self-confidence. Also, activation was a predictor of performance. 相似文献
216.
Ahmad Mohammad Qablan Amjad Abuloum Jamal Abu Al-Ruz 《Journal of Science Education and Technology》2009,18(3):291-300
A series of interviews and classroom observations were conducted with a group of in-service science teachers, students, school
principal, and computer lab supervisors, from a “Discovery” female school in Jordan to assess their utilization of information
and communication technology (ICT) in teaching science. The study also intended to determine how these participants were using
ICT and if they had any internal and external impediments in the way of the effective integration of ICT in the teaching of
science. Results showed that some participants were using ICT creatively in their science teaching. However, despite considerable
political pressure to increase ICT use in the classroom, most expressed frustration at the lack of ICT tools, support from
the school, from the Ministry of Education, and from the surrounding community. The article proposes possible resolutions
to help these participants overcome their impediments. Some of the suggested resolutions for the internal impediments include
involving teachers in preparing the school’s time-table, equipping the school with more ICT tools and offering more training
courses for teachers. However, the suggested resolutions for the external impediments involve (1) The Ministry of Education
to rethink the administration of board examinations, (2) The school to sacrifice scoring higher in board examinations for
preparing more creative and more versatile students’ perspectives. 相似文献
217.
Neda Nasiri Ahmad Fakharian Mohammad Bagher Menhaj 《Journal of The Franklin Institute》2021,358(10):5185-5212
This paper presents a novel combined State Dependent Riccati Equation (SDRE) / Function Approximation Technique (FAT)-based control design for nonlinear uncertain systems. The SDRE is employed to construct an optimal controller and the function approximation technique is utilized to estimate time-varying disturbances and uncertainties. Moreover, a robust term in the proposed control law compensates for the truncation error. The closed-loop stability and boundedness of the tracking error and FAT weights approximation error are proved in the sense of Lyapunov, with consideration of truncation error. Due to the great importance of the adequate performance of transient response from practical point of view, performance evaluation has been accomplished. The proposed scheme is computationally simple due to utilizing the FAT to represent uncertainties and disturbances as a function of time. Compared with the SDRE based SMC, the proposed controller is superior in terms of capability to track a fast and highly complicated trajectory and no need to determine time-varying disturbances and uncertainties bounds. The case study is a Selective Compliant Articulated Robot for Assembly (SCARA) flexible joint manipulator as a representative of highly nonlinear, coupled, large robotic systems. Simulation results easily verify the effectiveness and superiority of the proposed controller. 相似文献
218.
Simin Sohrabi Azim Akbarzadeh Dariush Norouzian Ali Farhangi Mehri Mortazavi Mohammad Reza Mehrabi Mohsen Chiani Zahra Saffari Soheil Ghassemi 《Indian journal of clinical biochemistry : IJCB》2011,26(4):354-359
The attempt is made to produce recombinant factor VIII but the first step in producing such product is production and purification
of rabbit’s polyclonal antibody against factor VIII. The second and third steps involve monoclonal antibody and recombinant
factor VIII production. Factor VIII is one of the most important coagulating factor where its deficiency leads to diseases
like hemophilia type A or classic. It is an inherited disease. Previously, it was obtained through fractionation of blood
plasma of blood donors. After processing, factor VIII could be used to manage such patients. Due to transfer of viral disease
like hepatitis and HIV through factor VIII obtained by fractionation, high cost of production, insufficiency of the donors
and the process of virus removal, thus production of factor VIII through recombinant technology can be useful and helpful.
The reaction between antibody and antigen is one the most specific reaction; therefore, such reaction can be employed to identify
factor VIII. Thereby, rabbits were injected several times with adjuvant-linked antigen to produce antibody. The antibody was
separated from the blood sample, purified and used to identify factor VIII in the research. 相似文献
219.
Faramarz Soheili Ali Akbar Khasseh Afshin Mousavi Chelak Mohammad Tavakolizadeh‐Ravari 《Learned Publishing》2018,31(2):121-129
Influence and capital are two concepts used to evaluate scholarly outputs, and these can be measured using the Scholarly Capital Model as a modelling tool. The tool looks at the concepts of connectedness, venue representation, and ideational influence using centrality measures within a social network. This research used co‐authorships and h‐indices to investigate authors who have published papers in the field of information behaviour between 1980 and 2015 as extracted from Web of Science. The findings show a relationship between the authors’ connectedness and the venue (journal) representation. It could be seen that the venue (journal) influences the chance of citation, and equally, the prestige (centrality) of authors probably raises the citations of the journals. The research also shows a significant positive relationship between the venue representation and ideational influence. This means that a research work that is published in a highly cited journal will find more visibility and will receive more citations. 相似文献
220.
古代伊朗科学家曾对科学,特别是天文学做出过重大贡献。当代的伊朗科学家继承了这一传统,并致力于向公众传播科学。21世纪初,由一批科学家、热心科学传播的社会人士和私营企业组成的非政府组织积极筹建马什哈德天文馆、科学中心等科普场馆。本文通过这一案例,讨论了非政府组织在科普场馆建设和科学传播中的作用、问题和可行性,并介绍了马什哈德天文学会为此采取的相应对策。 相似文献