首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:从到   被引次数:从到   他引次数:从到 提示：输入*表示无穷大
全文获取类型
  收费全文   17篇
  免费   0篇
专业分类
教育   9篇
科学研究   3篇
各国文化   1篇
体育   4篇
出版年
  2022年   1篇
  2021年   2篇
  2017年   2篇
  2016年   1篇
  2015年   2篇
  2014年   1篇
  2013年   4篇
  2012年   1篇
  2011年   3篇
排序方式： 共有17条查询结果，搜索用时 500 毫秒
1.
  相似文献   
2.
The main purpose of this study was to examine the effect of chalk on the friction coefficient between climber's fingers and two different rock types (sandstone and limestone). The secondary purpose was to investigate the effects of humidity and temperature on the friction coefficient and on the influence of chalk. Eleven experienced climbers took part in this study and 42 test sessions were performed. Participants hung from holds which were fixed on a specially designed hang board. The inclination of the hang board was progressively increased until the climber's hand slipped from the holds. The angle of the hang board was simultaneously recorded by using a gyroscopic sensor and the friction coefficient was calculated at the moment of slip. The results showed that there was a significant positive effect of chalk on the coefficient of friction (+18.7% on limestone and +21.6% on sandstone). Moreover sandstone had a higher coefficient of friction than limestone (+15.6% without chalk, +18.4% with chalk). These results confirmed climbers' belief that chalk enhances friction. However, no correlation with humidity/temperature and friction coefficient was noted which suggested that additional parameters should be considered in order to understand the effects of climate on finger friction in rock climbing.  相似文献   
3.
The aim of this study was to understand how the commonly used climbing-specific grip techniques and hold depths influence the finger force capacities. Ten advanced climbers performed maximal voluntary force on four different hold depths (from 1 to 4 cm) and in two force directions (antero-posterior and vertical) using three grip techniques (slope, half crimp and full crimp). A specially designed platform instrumented with a 6-degrees-of-freedom (DoF) force/torque sensor was used to record force values. Results showed that the maximal vertical forces differed significantly according to the hold depth and the grip technique (ranged from 350.8 N to 575.7 N). The maximal vertical forces increased according to the hold depth but the form of this increase differed depending on grip technique. These results seemed to be more associated with finger-hold contact/interaction than with internal biomechanical factors. Similar results were revealed for antero-posterior forces (ranged from 69.9 N to 138.0 N) but, it was additionally noted that climbers have different hand-forearm posture strategies with slope and crimp grip techniques when applying antero-posterior forces. This point is important as it could influence the body position adopted during climbing according to the chosen grip technique. For trainers and designers, a polynomial regression model was proposed in order to predict the mean maximal force based on hold depth and adopted grip technique.  相似文献   
4.

The present study explored the direct and indirect (serial multiple mediation of math self-efficacy and math enjoyment) effects of perceived parental math support on middle school students’ math engagement. A total of 374 middle school students ranging the age of 11 to 15 years completed a set of questionnaires assessing perceived parental math support, math self-efficacy, math enjoyment, and math engagement. In the analysis of structural model, a multiple-step multiple mediation analysis was employed. The findings indicated that perceived parental math support was directly and positively associated with math engagement. Additionally, math self-efficacy and math enjoyment sequentially mediated the relationship between parental math support and math engagement. The limitations and implications of the results are discussed and suggestions for future research are proposed.

  相似文献   
5.

Objective

This study aims to investigate the degree of biocompatibility and neuroregeneration of a polymer tube, poly-3-hydroxyoctanoate (PHO) in nerve gap repair.

Methods

Forty Wistar Albino male rats were randomized into two groups: autologous nerve gap repair group and PHO tube repair group. In each group, a 10-mm right sciatic nerve defect was created and reconstructed accordingly. Neuroregeneration was studied by sciatic function index (SFI), electromyography, and immunohistochemical studies on Days 7, 21, 45 and 60 of implantation. Biocompatibility was analyzed by the capsule formation around the conduit. Biodegradation was analyzed by the molecular weight loss in vivo.

Results

Electrophysiological and histomorphometric assessments demonstrated neuroregeneration in both groups over time. In the experimental group, a straight alignment of the Schwann cells parallel to the axons was detected. However, autologous nerve graft seems to have a superior neuroregeneration compared to PHO grafts. Minor biodegradation was observed in PHO conduit at the end of 60 d.

Conclusions

Although neuroregeneration is detected in PHO grafts with minor degradation in 60 d, autologous nerve graft is found to be superior in axonal regeneration compared to PHO nerve tube grafts. PHO conduits were found to create minor inflammatory reaction in vivo, resulting in good soft tissue response.  相似文献   
6.
Abstract

We investigated the effect of verbal encouragement on maximal voluntary contraction (MVC) level of the triceps surae muscle group. Our secondary focus was to examine whether the effect of verbal encouragement on MVC level varies as a result of conscientiousness. While the participants performed plantar flexion, MVCs of the triceps surae muscle group were measured using rectified and smoothed surface electromyography (rsEMG) during the absence and presence of verbal encouragement. Participants completed questions from the Five Factor Personality Inventory concerning conscientiousness and were divided into high- and low-conscientiousness groups according to a median split. The sample included 30 female and 53 male elite athletes. In the entire cohort, there was no significant difference in MVCs with and without verbal encouragement. When the sample was partitioned by conscientiousness scores, verbal encouragement led to a significant increase in MVC in the low-conscientiousness group, whereas verbal encouragement led to a non-significant decrease in MVC in the high-conscientiousness group. Percentage change in MVC across experimental conditions was significantly different between the groups, with a 9.72% increase during verbal encouragement of the low-conscientiousness group, and a 2.47% decrease during verbal encouragement of the high-conscientiousness group.  相似文献   
7.
The degree to which pre-service teachers learn biology is related to both motivational factors of self-regulation and factors regarding epistemological beliefs. At the same time, self-regulation and epistemological beliefs are also associated with one another. Based on this relationship, the purpose of this study was to investigate the relationship between components of epistemological beliefs and self-refulation (self-efficacy and test-anxiety) on learning biology. The study was conducted with 411 pre-service elementary and pre-service elementary science teachers by using a predictive research approach. Collected data was analyzed by the multiple linear regression technique. The results showed that only the belief about “existence of one truth” was a significant predictor of test anxiety while there was no epistemological predictor of self-efficacy. Conclusions and implications of the study will be discussed.  相似文献   
8.
In this treatise, three scholars join together to present what they believe to be voids and needs for the field of human performance technology (HPT). They present arguments that support the idea that HPT is an intellectual endeavor. They proceed to present a set of propositions that raise questions about trends and issues that they believe are challenges to HPT's future as a viable field of study. They conclude by presenting a set of recommendations and action plans to form a Scholar's Guild as a means to preserve, guide, and grow the field of HPT.  相似文献   
9.
The aim of this study was to compare the musculature activity and kinematics of knee and hip joints during front and back squat with maximal loading. Two-dimensional kinematical data were collected and electromyographic activities of vastus lateralis, vastus medialis, rectus femoris, semitendinosus, biceps femoris, gluteus maximus and erector spinae were measured while participants (n = 12, 21.2 ± 1.9 years old) were completing front and back squat exercises with maximum loading. Paired sample t-test was used for comparisons between two techniques. Results showed that the electromyographic activity of vastus medialis was found to be greater in the front squat compared to the back squat during the ascending phase (P < 0.05, d = 0.62; 95% CI, ?15.0/?4.17) and the whole manoeuvre (P < 0.05, d = 0.41; 95% CI, ?12.8/?0.43), while semitendinosus (P < 0.05, d = ?0.79; 95% CI, 0.62/20.59) electromyographic activity was greater in the back squat during the ascending phase. Compared to the front squat version, back squat exhibited significantly greater trunk lean, with no differences occurring in the knee joint kinematics throughout the movement. Results may suggest that the front squat may be preferred to the back squat for knee extensor development and for preventing possible lumbar injuries during maximum loading.  相似文献   
10.
Endothelins (ET) are a group of endogenous peptides, which have a strong and long-lasting vasoconstrictive effect. Three isoforms of endothelins coded by three different genes have been identified to date. Endothelin-1 (ET-1) is the most potent vasoconstrictive agent currently identified, and it was originally isolated and characterized from the culture media of aortic endothelial cells. Two other isoforms, named endothelin-2 (ET-2) and endothelin-3 (ET-3), were subsequently identified, along with structural homologues isolated from the venom ofActractapis engaddensis known as the sarafotoxins. The biological effects of endothelin production are determined via activation of one or two G-protein coupled receptors, endothelin receptors A (ETRA) and B (ETRB1 and ETRB2). Recently endothelin receptor C (ETRC) was discovered, however, its functions and distribution still remain unclear. The effects mediated by ET-1 via ETRA are vasoconstriction, bronchoconstriction and secretion of aldosterone. Agonists related to the ETRB1 activation cause vasodilatation by stimulating NO, PGI2 and endothelium-derived hyperpolarizing factor (EDHF). In contrast, coupling to ETRB2 causes vasoconstriction. Involvement of ET has been demonstrated in the pathophysiology of certain disorders. In this review, we discuss the physiological and pathophysiological role of endothelium-derived ET-1, the pharmacology of its two receptors, focusing on the role of ET-1 in the development of some pathophysiological conditions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号