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 15 毫秒
221.
Mohammad Muzaffar Mir Abdul Rashid Khan Nazir Ahmad Dar Mohammad Salahuddin 《Indian journal of clinical biochemistry : IJCB》2005,20(1):184-192
Alpha-1-proteinase inhibitor activity was studied in presence of resting and activated polymorphonuclear leucocytes. Four
different agonists; phorbol myristic acetate, N-formyl-methionyl-leucyl-phenylalanine, opsonised zymosan and arachidonic acid
decreased the inhibitor activity by 23.3%, 20%, 12% and 16.6^ respectively. The inhibitor activity was protected by using
various free radical scavengers. Catalase and superoxide dismutase both restored activity by about 18%, mannitol by 13% and
sodium azide by 17.3%. The inhibitor activity was also protected significantly by pretreatment of polymorphs with L-Arg, a
precursor of nitric oxide, before activation. L-Arg was also observed to suppress the generation of superoxide and hydroxyl
radical appreciably. The nitric oxide synthase inhibitor, aminoguanidine drastically inhibited the nitrite release and reversed
the protection offered by L-Arg to the inhibitor activity. Our results indicate a multifactorial nature of the inactivation
process, the culprit species being superoxide, hydrogen peroxide, hydroxyl radical and hypohalides. Nitric oxide seems to
scavenge the superoxide radical directly after its formation rather than inhibiting its generation by NADPH oxidase as was
believed earlier. 相似文献
222.
An evaluation of traditional admission standards in predicting Kuwait University students' academic performance 总被引:1,自引:0,他引:1
The purpose of this study was to evaluate the usefulness of the traditional admission standards utilized by Kuwait University in predicting students' academic performance. It was found that the established practice of using students' score in standardized secondary school examinations and branch of study (i.e. sciences or arts emphasis) to be highly predictive of their college cumulative grade point average. Moreover, it was established that students' secondary school scores reflect intellective as well as the non-intellective factors pertaining to students' background. 相似文献
223.
DEHGHANI Mohammad Hadi MAHVI Amir Hossein NAJAFPOOR Ali Asghar AZAM Kamal 《浙江大学学报(A卷英文版)》2007,8(9):1462-1468
The effectiveness of using acoustical (sonochemical) reactor for degradation of linear alkylbenzen sulfonate (LAS) from aqueous solution was investigated. LASs are anionic surfactants,found in relatively high amounts in domestic and industrial wastewaters. In this study,experiments on LAS solution were performed using methylene blue active substances (MBAS) method. The effectiveness of acoustical processor reactor for LAS degradation is evaluated with emphasis on the effect of treatment time and initial LAS concentration. Experiments were performed at initial concentrations of 0.2,0.5,0.8 and 1.0 mg/L,acoustic fre-quency of 130 kHz,applied power of 500 W and temperature of 18 °C~20 °C. At the conditions involved,LAS degradation was found to increase with increasing sonochemical time. In addition,as the concentration increased,the LAS degradation rate de-creased in the acoustical processor reactor. 相似文献
224.
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
225.
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
226.
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
227.
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
228.
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
229.
230.
A. Aziz Khater Ahmad M. El-Nagar Mohammad El-Bardini Nabila M. El-Rabaie 《Journal of The Franklin Institute》2019,356(16):9254-9285
In this study, an adaptive interval type-2 Takagi-Sugeno-Kang fuzzy logic controller based on reinforcement learning (AIT2-TSK-FLC-RL) is proposed. The proposed controller consists of an actor, a critic and a reward signal. The actor is represented by the IT2-TSK-FLC in which the antecedents and the consequents are interval type-2 fuzzy sets (IT2FSs) and type-1 fuzzy sets (T1FSs), respectively, which are named A2-C1. The critic is represented by a neural network, which approximates the optimal guaranteed cost in the control design to ensure the system stability for all admissible uncertainties and noise. The use of a reward signal to formalize the idea of a goal is one of the most distinctive features of RL. Thus, the proposed controller evolves in time as a result of the online learning algorithm. The parameters of the proposed controller are learned online based on the Lyapunov theorem to guarantee the stability, overcome the shortcomings of the gradient descent, such as the local minima and instability, and determine the learning rate of the IT2-TSK-FLC controller. Furthermore, the critic stability is discussed for determining the optimal learning rate. The proposed controller is applied to uncertain nonlinear systems to show its robustness in reducing the effect of system uncertainties and external disturbances and is compared to other controllers. 相似文献