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61.
João R. Vaz Bjørn Harald Olstad Jan Cabri Per-Ludvik Kjendlie Pedro Pezarat-Correia François Hug 《Journal of sports sciences》2016,34(20):1941-1948
The present study aimed to compare muscle coordination strategies of the upper and lower limb muscles between beginners and elite breaststroke swimmers. Surface electromyography (EMG) of eight muscles was recorded in 16 swimmers (8 elite, 8 beginners) during a 25 m swimming breaststroke at 100% of maximal effort. A decomposition algorithm was used to identify the muscle synergies that represent the temporal and spatial organisation of muscle coordination. Between-groups indices of similarity and lag times were calculated. Individual muscle patterns were moderately to highly similar between groups (between-group indices range: 0.61 to 0.84). Significant differences were found in terms of lag time for pectoralis major (P < 0.05), biceps brachii, rectus femoris and tibialis anterior (P < 0.01), indicating an earlier activation for these muscles in beginners compared to elites (range: ?13.2 to ?3.8% of the swimming cycle). Three muscle synergies were identified for both beginners and elites. Although their composition was similar between populations, the third synergy exhibited a high within-group variability. Moderate to high indices of similarity were found for the shape of synergy activation coefficients (range: 0.63 to 0.88) but there was a significant backward shift (?8.4% of the swimming cycle) in synergy #2 for beginners compared to elites. This time shift suggested differences in the global arm-to-leg coordination. These results indicate that the synergistic organisation of muscle coordination during breaststroke swimming is not profoundly affected by expertise. However, specific timing adjustments were observed between lower and upper limbs. 相似文献
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Besides phonotactic principles, orthographies entail graphotactic rules for which the reader must convert a phonological representation on the basis of spelling adaptation rules. In the present study, the learnability of such rules will be investigated with reference to Dutch. Although Dutch orthography can be considered highly regular, there are graphotactic rules that change letter sequences in plural noun formation. In a lexical decision experiment, the acquisition and use of such rules were examined. Participants were groups of 31 children from Grade 3 and 34 children from Grade 6, and 25 adults. The results showed that both children and adults are significantly less accurate and slower in recognizing plural word forms which undergo vowel change as a consequence of pluralization. It is concluded that graphotactic rules in Dutch orthography complicate Dutch word identification from an early stage of development and continue to play a complicating role in the word identification process of adult readers. In the discussion it is shown that current models fail to fully explain the processing of graphotactic rules in visual word identification. 相似文献
64.
Decision‐making in educations systems has become more complex: while decentralisation has moved the locus of power to lower governance levels, the central level still is held responsible for the quality of outcomes. As a consequence, new steering strategies have emerged that tend to apply softer modes of governance as opposed to harder ones in the past. This article aims at shedding empirical and conceptual light on these new developments. It compares two national examples for soft modes of governance with a supra‐national one (the EU's Open Method of Co‐ordination OMC) and argues that OMC might be both a useful analytical lens to categorise new steering mechanisms and a possibly promising policy strategy at the national level. 相似文献
65.
Three experiments on classical differential conditioning of the human skin conductance response to elemental and compound stimuli are reported. Subjects in Experiment 1 received both positive and negative patterning training, followed by either positive or negative patterning transfer tests on new stimuli. In positive patterning, a compound of two stimuli is reinforced and its elements are nonreinforced. In negative patterning, the elements are reinforced and the compound is nonreinforced. Subjects in Experiments 2 and 3 received either positive or negative patterning during training, followed by transfer tests on new stimuli. In Experiment 2, the transfer series began with new elements, after which their compound was presented; in Experiment 3, the new compound was presented first in the transfer series, and then the separate elements were administered. All three experiments provided evidence of the acquisition of positive patterning, while negative patterning was found only in Experiments 2 and 3. Positive patterning transferred to new stimuli, indicating that it was not attributable solely to summation of sub-threshold excitation conditioned to the elements on reinforced compound trials. This finding, coupled with the negative patterning found in Experiments 2 and 3, provided support for the unique cue hypothesis. It was concluded that the assumed unique cue constituted a learned “rule,” and that the actual elemental stimuli were neither perceptually nor otherwise modified during the conditioning process. 相似文献
66.
‘Energy regions’: The transformative power of regional discourses on socio-technical futures 总被引:1,自引:0,他引:1
‘Guiding visions’ play an important role in the transition management approach as a central means of mobilizing social actors and the co-ordination of dispersed agency.‘Energy regions’ in Austria are an interesting example for the strategic promotion of such guiding visions in the context of regional development. We describe the case of Murau, an alpine district in which a strong actor network has been built around a vision of systematically exploiting renewable energy sources and at the same time saving the region from economic decay. The vision gained much authority and has been institutionalised at various levels of regional governance. It furthermore was supported by and played an important role for regime level attempts to influence socio-technical change.Development and social propagation of such visions are inherently political and contested processes involving much strategizing and anticipation of conflict. We describe particular discursive strategies applied in niches - such as the combination and translation of sentiments into localised visions and demonstrations of feasibility. These strategies can be understood as systematic attempts to support discursive shifts at regime level by means of local activities, and aim to modify rather durable power structures.We suggest ways to analyse such discursive practices in order to orient strategic action in the course of such processes: analysing ‘guiding visions’ and their interference with other emerging trends; extending analyses across spatial scales (e.g. translations) and across thematic fields (e.g. convergence of agendas); and focusing on processes of stabilisation, institutionalisation and mutually reinforcing developments. 相似文献
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Bjørn Harald Olstad João Rocha Vaz Christoph Zinner Jan M.H. Cabri Per-Ludvik Kjendlie 《Journal of sports sciences》2017,35(11):1107-1117
The aims of this study were to describe muscular activation patterns and kinematic variables during the complete stroke cycle (SC) and the different phases of breaststroke swimming at submaximal and maximal efforts. Surface electromyography (sEMG) was collected from eight muscles in nine elite swimmers; five females (age 20.3 ± 5.4 years; Fédération Internationale de Natation [FINA] points 815 ± 160) and four males (27.7 ± 7.1 years; FINA points 879 ± 151). Underwater cameras were used for 3D kinematic analysis with automatic motion tracking. The participants swam 25 m of breaststroke at 60%, 80% and 100% effort and each SC was divided into three phases: knee extension, knee extended and knee flexion. With increasing effort, the swimmers decreased their SC distance and increased their velocity and stroke rate. A decrease during the different phases was found for duration during knee extended and knee flexion, distance during knee extended and knee angle at the beginning of knee extension with increasing effort. Velocity increased for all phases. The mean activation pattern remained similar across the different effort levels, but the muscles showed longer activation periods relative to the SC and increased integrated sEMG (except trapezius) with increasing effort. The muscle activation patterns, muscular participation and kinematics assessed in this study with elite breaststroke swimmers contribute to a better understanding of the stroke and what occurs at different effort levels. This could be used as a reference for optimising breaststroke training to improve performance. 相似文献
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