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:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   31018篇
  免费   489篇
  国内免费   152篇
教育   21607篇
科学研究   2995篇
各国文化   291篇
体育   3150篇
综合类   50篇
文化理论   247篇
信息传播   3319篇
  2022年   172篇
  2021年   290篇
  2020年   496篇
  2019年   660篇
  2018年   927篇
  2017年   1007篇
  2016年   933篇
  2015年   579篇
  2014年   762篇
  2013年   5597篇
  2012年   738篇
  2011年   817篇
  2010年   635篇
  2009年   637篇
  2008年   676篇
  2007年   641篇
  2006年   610篇
  2005年   526篇
  2004年   713篇
  2003年   650篇
  2002年   701篇
  2001年   787篇
  2000年   598篇
  1999年   527篇
  1998年   298篇
  1997年   313篇
  1996年   330篇
  1995年   303篇
  1994年   300篇
  1993年   258篇
  1992年   430篇
  1991年   394篇
  1990年   440篇
  1989年   424篇
  1988年   388篇
  1987年   356篇
  1986年   353篇
  1985年   432篇
  1984年   360篇
  1983年   359篇
  1982年   282篇
  1981年   277篇
  1980年   257篇
  1979年   354篇
  1978年   290篇
  1977年   253篇
  1976年   238篇
  1975年   183篇
  1974年   185篇
  1973年   209篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
991.
This paper analyzes the effects that the 2012 VAT rise in Spain had on household’ demand for cultural goods and services. Household’ demands are modeled as a two-stage QUAIDS. After estimating price and expenditure elasticities, and the pass-through parameter associated with the reform, our results show that the individual welfare loss and the increment in the tax bill increase, but less than proportionately, with income. Consequently, the reform can be considered as regressive. Relating the effects of the VAT reform to households’ incomes also implies a low quantitative effect, because of the low proportion of total household expenditure that cultural expenditure represents. From a social perspective, the size of the induced welfare loss would positively depend on society’s inequality aversion. Regardless of the latter, it cannot be concluded whether the reform would have increased or reduced inequality in the distribution of cultural spending. Our results prove qualitatively robust to alternative values of the pass-through parameter.  相似文献   
992.
Background:In a sprint cross-country(XC)ski competition,the difference in recovery times separating the first and the second semi-final(SF)heats from the final(F)may affect performance.The aim of the current study was to compare the effects of longer vs.shorter recovery periods prescribed between the 3 knock-out races of a simulated sprint XC ski competition involving a prologue(P),quarter-final(QF),SF,and F.Methods:Eleven well-trained XC ski athletes completed 2 simulated sprint XC ski competitions on a treadmill involving 4×883-m roller-ski bouts at a 4°incline using the gear 3 ski-skating sub-technique.The first 3 bouts were completed at a fixed speed(PFIX,QFFIX,and SFFIX)corresponding to~96%of each individual’s previously determined maximal effort.The final bout was performed as a self-paced sprint time trial(FSTT).Test conditions differed by the time durations prescribed between the QFFIX,SFFIX,and FSTT,which simulated real-world XC ski competition conditions using maximum(MAX-REC)or minimum(MIN-REC)recovery periods.Results:The FSTT was completed 5.4±5.5 s faster(p=0.009)during MAX-REC(179.2±18.1 s)compared to MIN-REC(184.6±20.0 s),and this was linked to a significantly higher power output(p=0.010)and total metabolic rate(p=0.009).The pre FSTT blood lactate(BLa)concentration was significantly lower during MAX-REC compared to MIN-REC(2.5±0.8 mmol/L vs.3.6±1.6 mmol/L,respectively;p=0.027),and the pre-to-post FSTT increase in BLa was greater(8.8±2.1 mmol/L vs.7.1±2.3 mmol/L,respectively;p=0.024).No other differences for MAX-REC vs.MIN-REC reached significance(p>0.05).Conclusion:Performance in a group of well-trained XC skiers is negatively affected when recovery times between sprint heats are minimized which,in competition conditions,would occur when selecting the last QF heat.This result is combined with a higher pre-race BLa concentration and a reduced rise in BLa concentration under shorter recovery conditions.These findings may help inform decision making when XC skiers are faced with selecting a QF heat within a sprint competition.  相似文献   
993.
Multicultural classrooms and cultural communities of teachers   总被引:1,自引:0,他引:1  
This paper addresses issues of teacher adoption of culturally responsive pedagogy through reporting data from a 2-year ethnographic study of a teacher education program located in the U.S.A. The research findings reveal that preservice teachers experience and ultimately adopt a meritocratic and hegemonic system of schooling in which academic performance is viewed in terms of individual abilities and based on mainstream norms. The study suggests that, for substantive changes to take place in multicultural classrooms, teacher educators need to engage in the kind of critical examination which will lead to curricular reform intended to foster alternatives to hegemonic experiences and beliefs.  相似文献   
994.
This study investigated the extent to which position in the Australian Football League (AFL) national draft is associated with individual game performance metrics. Physical/technical skill performance metrics were collated from all participants in the 2014 national under 18 (U18) championships (18 games) drafted into the AFL (n = 65; 17.8 ± 0.5 y); 232 observations. Players were subdivided into draft position (ranked 1–65) and then draft round (1–4). Here, earlier draft selection (i.e., closer to 1) reflects a more desirable player. Microtechnology and a commercial provider facilitated the quantification of individual game performance metrics (= 16). Linear mixed models were fitted to data, modelling the extent to which draft position was associated with these metrics. Draft position in the first/second round was negatively associated with “contested possessions” and “contested marks”, respectively. Physical performance metrics were positively associated with draft position in these rounds. Correlations weakened for the third/fourth rounds. Contested possessions/marks were associated with an earlier draft selection. Physical performance metrics were associated with a later draft selection. Recruiters change the type of U18 player they draft as the selection pool reduces. juniors with contested skill appear prioritised.  相似文献   
995.
This study investigated (i) the prevalence of hypohydration and (ii) association between urinary indices of hydration status and confounding factors (e.g., urine protein content, water intake) in elite youth boxers during their weight-stable phase before competition. Sixteen national champion boxers (all male, 17 ± 1 y) were measured on 3 occasions (baseline, day 3, day 10), 30-day prior to competition. Body mass, total body water, urine specific gravity (USG), osmolality (UOSM) and total protein content (TPC) were evaluated to determine hydration status and fluid balance. Overall macronutrient and water intake were assessed using dietary records. Both UOSM and USG increased from day 3 to day 10 by 16% and 0.4% (P < 0.001), despite athletes being in their weight-stability period, and regardless of ad libitum fluid intake. Hypohydration was universally prevalent among all athletes on both test days with USG: 1.027 ± 0.003 g · mL?1 and UOSM: 1035 ± 108 mOsmol · kg?1. An inverse association between mean UOSM values and mean water intake was observed (R = ?0.52, P = 0.04), while TPC was not associated with any urinary dehydration markers (USG, P = 0.51; UOSM, P = 0.61). The present outcomes find that the most prevalent urinary dehydration markers used to classify hydration status in competition exhibit large variability, even during weight-stable periods.  相似文献   
996.
This study examined whether or not activity monitor data collected as part of a typical 7-day physical activity (PA) measurement protocol can be expected to be missing at random. A total of 315 participants (9–18 years) each wore a SenseWear Armband monitor for 7 consecutive days. Participants were classified as “compliant” (86 boys and 124 girls) if they had recorded accelerometer data during 70% or more of the predefined awake time (7 AM–10 PM) on four different days; and “non-compliant” (44 boys and 51 girls) when not meeting these criteria. Linear mixed models were used to examine differences in energy expenditure (EE) levels by compliance across 10 different time periods. The results indicated that non-compliant girls were older (13.4 ± 2.9 vs. 12.2 ± 2.5) and taller (156.8 ± 10.3 vs. 152.8 ± 11.3) than their same gender compliant peers (P < .05). Comparisons of EE rates at segmented portions of the day revealed no differences between compliant and non-compliant groups (P ≥ .05). Differences in EE ranged from ?0.32 kcal · kg?1 · h?1 (before school time) to 0.62 kcal · kg?1 · h?1 (physical education class) in boys and ?0.39 kcal · kg?1 · h?1 (transportation from school) to 0.37 kcal · kg?1 · hour?1 (recess) in girls. The results showed that compliant and non-compliant individuals differed in a few demographic characteristics but exhibited similar activity patterns. This suggests that data were considered to be missing at random, but additional work is needed to confirm this observation in a representative sample of children using other types of activity monitors and protocols.  相似文献   
997.
Team handball is a popular sport worldwide that requires numerous throws to be made throughout the course of a game. Because of the upper extremity demands of repetitive throwing, it is possible that fatigue can alter the mechanics of a shot. The purpose of this study was to determine the influence of localised fatigue on jump shot kinematics and kinetics. Eleven male team handball players (23.1 ± 3.1 years; 185.1 ± 8.3 cm; 89.7 ± 12.2 kg) volunteered. An electromagnetic tracking system was used to examine the jump shot prior to and following localised fatigue. The fatiguing protocol consisted of throwing a 2.2 kg medicine ball into a rebounder until volitional fatigue. No significant kinematic or kinetic differences were observed following fatigue. Shoulder external rotation was ?74.8 ± 14.9° prior to and ?79.0 ± 14.7° following fatigue at MER. Scapula, external rotation at ball release (BR) prior to fatigue was ?2.2 ± 7.0° and ?3.2 ± 11.1° following fatigue. Scapular internal rotation, at maximum shoulder internal rotation (MIR), changed from 18.4 ± 11.2° to 20.4 ± 11.8°. Ball velocity decreased from19.8 m · s–1 to 18.8 m · s–1 (P = 0.12). Accuracy percentage in the pre-fatigue trials was 60.8 ± 14.1% and 52.8 ± 12.7% following fatigue (P = 0.20). While no significant changes were observed, it is possible that other fatiguing protocols that more closely represent the aerobic and throwing demands of the sport may have a greater effect on the kinematics and kinetics of the jump shot.  相似文献   
998.
Considerable research has documented that successful performance in interceptive tasks (such as return of serve in tennis) is based on the performers’ capability to capture appropriate anticipatory information prior to the flight path of the approaching object. Athletes of higher skill tend to fixate on different locations in the playing environment prior to initiation of a skill than their lesser skilled counterparts. The purpose of this study was to examine visual search behaviour strategies of elite (world ranked) tennis players and non-ranked competitive tennis players (n = 43) utilising cluster analysis. The results of hierarchical (Ward’s method) and nonhierarchical (k means) cluster analyses revealed three different clusters. The clustering method distinguished visual behaviour of high, middle-and low-ranked players. Specifically, high-ranked players demonstrated longer mean fixation duration and lower variation of visual search than middle-and low-ranked players. In conclusion, the results demonstrated that cluster analysis is a useful tool for detecting and analysing the areas of interest for use in experimental analysis of expertise and to distinguish visual search variables among participants’.  相似文献   
999.
Limb dominance theory suggests that females tend to be more one-leg dominant and exhibit greater kinematic and kinetic leg asymmetries than their male counterparts, contributing to the increased risk of anterior cruciate ligament injury among female athletes. Thus, the purpose of this study was to examine the influences of sex and limb dominance on lower extremity joint mechanics during unilateral land-and-cut manoeuvres. Twenty-one women and 21 men completed land-and-cut manoeuvres on their dominant limb as well as their nondominant limb. Three-dimensional kinematics and kinetics were calculated bilaterally for the entire stance phase of the manoeuvre. Women performed land-and-cut manoeuvres with altered hip motions and loads as well as greater knee abduction at touchdown compared to men. Dominant limb land-and-cut manoeuvres where characterised by decreased hip flexion at touchdown as well as decreased hip flexion and adduction range of motion compared to nondominant land-and-cuts regardless of sex. The observed sex differences are consistent with previous research regarding mechanisms underlying the sex disparity in anterior cruciate ligament injury rates. However, observed differences regarding limb dominances appear somewhat arbitrary and did not suggest that the dominant or nondominant limb would be at increased risk of anterior cruciate ligament injury.  相似文献   
1000.
Exercise testing on motorised treadmills provides valuable information about running performance and metabolism; however, the impact of treadmill type on these tests has not been investigated. This study compared the energy demand of running on two laboratory treadmills: an HP Cosmos (C) and a Quinton (Q) model, with the latter having a 4.5 times stiffer running platform. Twelve experienced runners ran identical bouts on these treadmills at a range of four submaximal velocities (reported data is for the velocity that approximated 75–81% VO2max). The stiffer treadmill elicited higher oxygen consumption (C: 46.7 ± 3.8; Q: 50.1 ± 4.3 ml·kg?1 · min?1), energy expenditure (C: 16.0 ± 2.5; Q: 17.7 ± 2.9 kcal · min?1), carbohydrate oxidation (C: 9.6 ± 3.1; Q: 13.0 ± 3.9 kcal · min?1), heart rate (C: 155 ± 16; Q: 163 ± 16 beats · min?1) and rating of perceived exertion (C: 13.8 ± 1.2; Q: 14.7 ± 1.2), but lower fat oxidation (C: 6.4 ± 2.3; Q: 4.6 ± 2.5 kcal · min?1) (all analysis of variance treadmill comparisons < 0.01). This study confirms that caution is required when comparing performance and metabolic results between different treadmills and suggests that treadmills will vary in their comparability to over-ground running depending on the running platform stiffness.  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