全文获取类型
收费全文 | 1069篇 |
免费 | 23篇 |
国内免费 | 27篇 |
专业分类
教育 | 545篇 |
科学研究 | 104篇 |
体育 | 312篇 |
综合类 | 144篇 |
文化理论 | 1篇 |
信息传播 | 13篇 |
出版年
2022年 | 6篇 |
2021年 | 11篇 |
2020年 | 13篇 |
2019年 | 15篇 |
2018年 | 21篇 |
2017年 | 18篇 |
2016年 | 28篇 |
2015年 | 20篇 |
2014年 | 46篇 |
2013年 | 151篇 |
2012年 | 57篇 |
2011年 | 66篇 |
2010年 | 53篇 |
2009年 | 43篇 |
2008年 | 43篇 |
2007年 | 66篇 |
2006年 | 54篇 |
2005年 | 57篇 |
2004年 | 67篇 |
2003年 | 48篇 |
2002年 | 41篇 |
2001年 | 44篇 |
2000年 | 37篇 |
1999年 | 17篇 |
1998年 | 15篇 |
1997年 | 24篇 |
1996年 | 5篇 |
1995年 | 17篇 |
1994年 | 9篇 |
1993年 | 11篇 |
1992年 | 8篇 |
1991年 | 4篇 |
1990年 | 4篇 |
排序方式: 共有1119条查询结果,搜索用时 15 毫秒
1.
通过将绿色经济评价指标体系的五个不同方面作为约束条件引入模型,可客观、有效地得出影响各评价对象绿色经济发展状况的关键因子。主要做法:一是利用离差最大化优化模型对各评价指标赋权,保证所求权重的客观性与合理性。二是将5个不同层面分别作为制约条件引入评价模型得到模型最优解。三是分别对有、无制约条件下的各评价对象的排名波动情况进行分析比较,确定各盟市绿色经济的发展差异以及影响其发展优劣的关键要素。实证结果表明,环境保护的相关方面对各盟市绿色经济发展影响最大,资源承载力及人的全面发展方面次之。 相似文献
2.
Georgina L. Kent Brian Dawson Lars R. McNaughton Gregory R. Cox Louise M. Burke Peter Peeling 《Journal of sports sciences》2019,37(3):339-346
This investigation assessed the effect of dietary nitrate (NO3?) supplementation, in the form of beetroot juice (BR), on repeat-sprint performance in normoxia and normobaric hypoxia. 12 male team-sport athletes (age 22.3 ± 2.6 y, VO2peak 53.1 ± 8.7 mL.kg?1.min?1) completed three exercise trials involving a 10 min submaximal warm-up and 4 sets of cycling repeat-sprint efforts (RSE; 9 × 4 s) at sea level (CON), or at 3000 m simulated altitude following acute supplementation (140 mL) with BR (HYPBR; 13 mmol NO3?) or NO3–depleted BR placebo (HYPPLA). Peak (PPO) and mean (MPO) power output, plus work decrement were recorded during the RSE task, while oxygen consumption (VO2) was measured during the warm-up. There were no significant differences observed between HYPBR and HYPPLA for PPO or MPO; however, work decrement was reduced in the first RSE set in HYPBR compared with HYPPLA. There was a moderate effect for VO2 to be lower following BR at the end of the 10 min warm-up (ES = 0.50 ± 0.51). Dietary NO3? may not improve repeat-sprint performance in hypoxia but may reduce VO2 during submaximal exercise. Therefore, BR supplementation may be more effective for performance improvement during predominantly aerobic exercise. 相似文献
3.
钴酸镍纳米材料具有良好的电催化氧析出反应(Oxygen Evolution Reaction,OER)活性,是一种很有发展潜力的非贵金属电催化材料。文章以碳纤维纸为基底,采用水热合成的方法对纳米结构钴酸镍的生长进行了系统的研究,分别考察了生长温度、前驱体浓度和配比、生长时间对产物的形貌、尺寸、物相结构、OER电化学性能的影响,通过对比分析后发现在生长温度100℃、生长时间5h、镍钴比为2:1时所获得的多孔片状钴酸镍纳米结构具有最佳的OER特性。 相似文献
4.
Eunkyeng Baek S. Natasha Beretvas Wim Van den Noortgate John M. Ferron 《Journal of Experimental Education》2020,88(4):698-710
AbstractRecently, researchers have used multilevel models for estimating intervention effects in single-case experiments that include replications across participants (e.g., multiple baseline designs) or for combining results across multiple single-case studies. Researchers estimating these multilevel models have primarily relied on restricted maximum likelihood (REML) techniques, but Bayesian approaches have also been suggested. The purpose of this Monte Carlo simulation study was to examine the impact of estimation method (REML versus Bayesian with noninformative priors) on the estimation of treatment effects (relative bias, root mean square error) and on the inferences about those effects (interval coverage) for autocorrelated multiple-baseline data. Simulated conditions varied with regard to the number of participants, series length, and distribution of the variance within and across participants. REML and Bayesian estimation led to estimates of the fixed effects that showed little to no bias but that differentially impacted the inferences about the fixed effects and the estimates of the variances. Implications for applied researchers and methodologists are discussed. 相似文献
5.
Alessandro Moura Zagatto Paulo Eduardo Redkva Rodrigo Araújo Bonetti de Poli Joel Abraham Martinez González Jeniffer Zanetti Brandani Thiago Penedo 《European Journal of Sport Science》2019,19(5):645-652
The purpose of this study was to investigate the use of a single 3-min all-out maximal effort to estimate anaerobic capacity (AC) through the lactate and excess post-exercise oxygen consumption (EPOC) response methods (AC[La?]+EPOCfast) on a cycle ergometer. Eleven physically active men (age?=?28.1?±?4.0?yrs, height?=?175.1?±?4.2?cm, body mass?=?74.8?±?11.9?kg and ?O2max?=?40.7?±?7.3?mL?kg?1?min?1), participated in the study and performed: i) five submaximal efforts, ii) a supramaximal effort at 115% of intensity of ?O2max, and iii) a 3-min all-out maximal effort. Anaerobic capacity was estimated using the supramaximal effort through conventional maximal accumulated oxygen deficit (MAOD) and also through the sum of oxygen equivalents from the glycolytic (fast component of excess post-exercise oxygen consumption) and phosphagen pathways (blood lactate accumulation) (AC[La?]+EPOCfast), while during the 3-min all-out maximal effort the anaerobic capacity was estimated using the AC[La?]+EPOCfast procedure. There were no significant differences between the three methods (p?>?0.05). Additionally, the anaerobic capacity estimated during the 3-min all-out effort was significantly correlated with the MAOD (r?=?0.74; p?=?0.009) and AC[La?]+EPOCfast methods (r?=?0.65; p?=?0.029). Therefore, it is possible to conclude that the 3-min all-out effort is valid to estimate anaerobic capacity in physically active men during a single cycle ergometer effort. 相似文献
6.
Alejandro Torrejón Carlos Balsalobre-Fernández G. Gregory Haff 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(3):245-255
This study aimed to determine the suitability of the load-velocity relationship to prescribe the relative load (%1RM) in women, as well as to compare the load-velocity profile between sexes and participants with different strength levels. The load-velocity relationship of 14 men (1RM: 1.17 ± 0.19) and 14 women (1RM: 0.66 ± 0.13) were evaluated in the bench press exercise. The main findings revealed that: (I) the load-velocity relationship was always strong and linear (R2 range: 0.987–0.993), (II) a steeper load-velocity profile was observed in men compared to women (Effect size [ES]: 1.09), with men showing higher velocities for light loads (ES: ? 0.81 and ? 0.40 for the y-intercept and 30%1RM, respectively), but women reporting higher velocities for the heavy loads (ES: 1.14 and 1.50 at 90%1RM and 100%1RM, respectively); and (III) while the slope of the load-velocity profile was moderately steeper for weak men compared to their strong counterpart (ES: 1.02), small differences were observed between strong and weak women (ES: ? 0.39). While these results support the use of the individual load-velocity relationship to prescribe the %1RM in the bench press exercise for women, they also highlight the large disparities in their load-velocity profile compared to men. 相似文献
7.
Yi-Hung Liao Toby Mündel Yan-Ting Yang Chen-Chan Wei Shiow-Chwen Tsai 《Journal of sports sciences》2019,37(16):1805-1815
The purpose of this study was to examine CHO ingestion on a cognitive task using a field-simulated time-trial (TT) under hypoxia in well-trained triathletes. Ten male triathletes (age: 22.1 ± 1.1 years; VO2max: 59.4 ± 1.4 ml/kg/min) participated in this double-blind/crossover/counter-balanced design study. Participants completed 3 TT trials: 1) normoxic placebo (NPLA; FiO2 = 20.9%), 2) hypoxic placebo (HPLA; FiO2 = 16.3%), and 3) hypoxic CHO (HCHO; 6% CHO provided as 2 ml/kg/15 min; FiO2 = 16.3%). During the TT, physiological responses (SpO2, HR, RPE, and blood glucose/lactate), cognitive performance, and cerebral haemodynamics were measured. Hypoxia reduced TT performance by ~3.5–4% (p < 0.05), but CHO did not affect TT performance under hypoxia. For the cognitive task, CHO slightly preserved exercise-induced cognitive reaction speed but did not affect response accuracy during hypoxic exercise. However, CHO did not preserve the decreased Hb-Diff (cerebral blood flow, CBF) and increased HHb in the prefrontal lobe (p < 0.05) during hypoxic exercise, and CHO failed to preserve hypoxia-suppressed prefrontal CBF and tissue oxygen saturation. In conclusion, the present study demonstrates that CHO is effective in sustaining reaction speed for a cognitive task but not promoting TT performance during hypoxic exercise, which would be important for strategy-/decision-making when athletes compete at moderate high-altitude. 相似文献
8.
ABSTRACTWe propose a new performance measure for table tennis players: the mutual point-winning probabilities (MPW) as server and receiver. The MPWs quantify a player’s chances to win a point against a given opponent, and hence nicely complement the classical match statistics history between two players. These new quantities are based on a Bradley-Terry-type statistical model taking into account the importance of individual points, since a rally at 8–2 in the first set is less crucial than a rally at the score of 9–9 in the final set. The MPWs hence reveal a player’s strength on his/her service against a given opponent as well as his/her capacity of scoring crucial points. We estimate the MPWs by means of maximum likelihood estimation and show via a Monte Carlo simulation study that our estimation procedure works well. In order to illustrate the MPWs’ versatile use, we have organized two round-robin tournaments of ten respectively eleven table tennis players from the Belgian table tennis federation. We compare the classical final ranking to the ranking based on MPWs, and we highlight how the MPWs shed new light on strengths and weaknesses of the players. 相似文献
9.
10.
Vivian Maria Arakelian Cássia da Luz Goulart Renata Gonçalves Mendes Nuno Manoel de Sousa Renata Trimer Solange Guizilini 《Journal of sports sciences》2019,37(12):1420-1428
Aim was to identify critical load (CL) in young and elderly apparently healthy male cohorts. To contrast the metabolic, cardiovascular and perceptual responses on CL according to age. We evaluated 12 young (23 ± 3 years) and 10 elderly (70 ± 2 years) apparently healthy active males, who underwent: (1) 1 repetition maximum (1RM) test on a 45° Leg Press; (2) on different days, three high-intensity resistance exercise constant load tests (60%, 75% and 90% 1RM) until fatigue (Tlim). Absolute values of both the CL asymptote and curvature constant (kg) were significantly lower in elderly subjects (P < 0.05). In contrast, elderly subjects demonstrated a significantly higher number of repetitions at CL when compared with young subjects (P < 0.05). As expected, oxygen uptake (VO2) and heart rate (HR) during maximal aerobic exercise testing were significantly reduced in older subjects. However, percent-predicted aerobic capacity were higher in older subjects (P < 0.05). In addition, blood lactate ([La?]) corrected to Tlim and rating of perceived exertion values were greater in younger subjects at all intensities (P < 0.05). These findings, despite reduced force production in older subjects, endurance-related parameters are well preserved according to age-adjusted percent-predicted values in apparently healthy males. 相似文献