全文获取类型
收费全文 | 4567篇 |
免费 | 51篇 |
国内免费 | 10篇 |
专业分类
教育 | 3414篇 |
科学研究 | 241篇 |
各国文化 | 43篇 |
体育 | 406篇 |
综合类 | 3篇 |
文化理论 | 62篇 |
信息传播 | 459篇 |
出版年
2022年 | 27篇 |
2021年 | 44篇 |
2020年 | 59篇 |
2019年 | 112篇 |
2018年 | 141篇 |
2017年 | 152篇 |
2016年 | 146篇 |
2015年 | 99篇 |
2014年 | 118篇 |
2013年 | 936篇 |
2012年 | 131篇 |
2011年 | 128篇 |
2010年 | 149篇 |
2009年 | 135篇 |
2008年 | 146篇 |
2007年 | 144篇 |
2006年 | 108篇 |
2005年 | 95篇 |
2004年 | 99篇 |
2003年 | 81篇 |
2002年 | 96篇 |
2001年 | 66篇 |
2000年 | 107篇 |
1999年 | 74篇 |
1998年 | 74篇 |
1997年 | 63篇 |
1996年 | 73篇 |
1995年 | 57篇 |
1994年 | 67篇 |
1993年 | 63篇 |
1992年 | 49篇 |
1991年 | 70篇 |
1990年 | 51篇 |
1989年 | 47篇 |
1988年 | 37篇 |
1987年 | 45篇 |
1986年 | 45篇 |
1985年 | 43篇 |
1984年 | 47篇 |
1983年 | 39篇 |
1982年 | 31篇 |
1981年 | 35篇 |
1980年 | 30篇 |
1979年 | 24篇 |
1978年 | 32篇 |
1977年 | 38篇 |
1976年 | 27篇 |
1975年 | 22篇 |
1974年 | 23篇 |
1972年 | 14篇 |
排序方式: 共有4628条查询结果,搜索用时 0 毫秒
161.
Thigh muscle volume is a useful determinant of functional fitness. However, anthropometric prediction of muscle content is influenced by the variability of adipose tissue accumulation. The aims of this study were to predict thigh muscle and adipose tissue volumes from anthropometry and to assess the validity of the method by examining the various components of the measurements and the assumptions involved. The 19 participants (9 men, 10 women; age 23-49 years) varied in adiposity. They all underwent magnetic resonance imaging (MRI) of the upper leg and the eight men and two women with the lowest adiposity underwent detailed anthropometry involving girths and skinfolds. Using MRI as the reference method, muscle volume was predictedfrom anthropometry using a circular concentric model, and the assumptions inherent in the method were tested further using the MRI data alone. Muscle volume was best predicted by anthropometry in the 10 leanest participants using a five-slice truncated cone model that overestimated the mean MRI value by 30% (R2 = 0.95; standard error of estimate = 288 cm3; P < 0.001). A single skinfold plus girth measurement at the mid-thigh almost matched its predictive ability, but with an increased bias. Measurements of leg circumference by means of the two techniques agreed well. The assumption of a circular cross-section was valid. In contrast, the agreement between skinfold thickness measured by caliper and superficial adipose tissue thickness by MRI was poor, contributing to the scatter of fat and lean area comparisons. An anterior skinfold thickness measurement underestimated the area of superficial adipose tissue at that level, particularly at the most proximal and distal sites. Although these limitations increase the uncertainties of muscle volume determination by anthropometry, they do not prevent its valid prediction in leaner individuals. The prediction of superficial adipose tissue was poorer. 相似文献
162.
For activities such as squash, badminton and fencing, the ability to quickly complete a lunge and return to the start or move off in another direction is critical for success. Determining which strength qualities are important predictors of lunge performance was the focus of this study. Thirty-one male athletes performed: (1) a unilateral maximal squat (one-repetition maximum, 1-RM) and unilateral jump squat (50% 1-RM) on an instrumented supine squat machine, and (2) a forward lunge while attached to a linear transducer. We performed stepwise multiple regression analysis with lunge performance as the dependent variable and various strength, flexibility and anthropometric measures as the independent variables. From the many strength and power measures calculated, time to peak force was the best single predictor of lunge performance, which accounted for 55% of the explained variance. The best three-variable model for predicting lunge performance accounted for 76-85% of the explained variance. The models differed, however, according to whether lunge performance was expressed relative to body mass (time to peak force, mean power and relative strength = 76%) or taken as an absolute value (time to peak force, leg length and flexibility = 85%). We conclude that one to two trials were reliable for strength diagnosis and that one strength measure cannot accurately explain functional performance because other factors, such as body mass, flexibility and leg length, have diverse effects on the statistical models. 相似文献
163.
The aims of this experiment were to determine whether there are differences between the sexes in the three-dimensional angular rotations of the lumbo-pelvic-hip complex during running and, if such differences exist, to establish whether factors other than sex can explain the observed differences. A cohort of 44 non-injured runners (22 males, 22 females) who usually ran more than 20 km per week were voluntarily recruited. All trials were conducted on a treadmill at a running speed of 4.0 m x s(-1). Reflective markers were placed over specific anatomical landmarks of the thoraco-lumbar spine, pelvis and femur. Data were captured using a VICON motion analysis system. Females tended to display a greater peak-to-peak oscillation for most of the angular rotations. An offset was the main difference between the male and female group mean waveforms for pelvis anterior-posterior tilt. Forward stepwise regression analysis revealed that sex was the most common variable related to the amplitudes of the angular rotations. Given these results, sport scientists conducting future biomechanical studies using angular data to test hypotheses are advised to be extremely cautious about averaging across male and female participants. 相似文献
164.
Other Index
Index to Volume XLI 相似文献165.
166.
Explaining Post-War Cinema Attendance in Great Britain 总被引:1,自引:0,他引:1
This paper models the interaction between cinema admissions and cinema supply in response to changes in exogenous variables, chiefly competition from television viewing. The relationship is estimated empirically by applying near Vector Autoregression (VAR) techniques to a long run of British annual data from 1950 to 1997. The results indicate that sustained negative shocks to cinema demand throughout most of the period reduced the supply of screens, inducing further falls in admissions and closures until a new equilibrium was attained. More recently, the introduction of multiplex cinemas has interrupted and partially reversed this downward demand-supply spiral. 相似文献
167.
Pelvis-thorax coordination has been recognised to be associated with swing speed. Increasing angular separation between the pelvis and thorax has been thought to initiate the stretch shortening cycle and lead to increased clubhead speed. The purpose of this study was to determine whether pelvis-thorax coupling played a significant role in regulating clubhead speed, in a group of low-handicap golfers (mean handicap = 4.1). Sixteen participants played shots to target distances determined based on their typical 5- and 6-iron shot distances. Half the difference between median 5- and 6-iron distance for each participant was used to create three swing effort conditions: “minus”, “norm”, and “plus”. Ten shots were played under each swing effort condition using both the 5-iron and 6-iron, resulting in six shot categories and 60 shots per participant. No significant differences were found for X-factor for club or swing effort. X-factor stretch showed significant differences for club and swing effort. Continuous relative phase (CRP) results mainly showed evidence of the stretch shortening cycle in the downswing and that it was more pronounced late in the downswing as swing effort increased. Substantial inter-individual CRP variability demonstrated the need for individual analyses when investigating coordination in the golf swing. 相似文献
168.
OBJECTIVE: The aim of this study was to examine the trajectory of cases through four systems: child protection, law enforcement, the dependency courts, and the criminal courts. METHOD: This study focused on a county selected from a 41-county telephone survey conducted for the National Incidence Study of Child Abuse and Neglect (NIS-3). For this analysis prospective samples were drawn from law enforcement (n=225) and the county child protection (CPS) agency (n=225) and followed through in-depth case tracking across all agencies and through both the dependency and criminal court systems. RESULTS: The percentage of CPS cases opened in dependency court was similar to prior studies (29%), but the acceptance and prosecution rates were much higher--92% of the cases referred from CPS, including many cases of physical abuse. Compared to referrals from CPS to law enforcement (93%), few cases were referred from law enforcement to CPS (17%). Anecdotally, case referral patterns appeared to be influenced by communication patterns and mutual positive regard, regardless of the collaborative protocols in place. One of the most instructive findings was the degree of difficulty in tracking cases across organizations and the types of obstacles that impeded success. Disorganization was not an issue, rather internal structures set up to facilitate intra-organizational processing were the same structures that actually impeded cross-organizational case finding. CONCLUSIONS: It is not sufficient to rely on the existence of multi-disciplinary teams or Child Advocacy Centers to ensure collaboration. More attention to daily tasks and activities as well as the nature and quality of communication is warranted. On the technical side, use of common case identifiers on cases that are cross-referred is strongly recommended. Future studies should broaden the scope of inquiry to include the consequences of all case trajectories, rather than solely focusing on the justice system. 相似文献
169.
170.
This article addresses the problem of how opportunities to learn in teacher education programs influence future elementary mathematics teachers’ knowledge. This study used data collected for the Teacher Education and Development Study in Mathematics (TEDS-M). TEDS-M measured the mathematics content knowledge (MCK) and the mathematics pedagogical content knowledge (MPCK) of future teachers in their final year in teacher preparation programs. The purpose of this study is to explore whether elementary teaching candidates’ MCK and MPCK are associated with their opportunities to learn in mathematics courses and mathematics methods courses in five countries. The results showed that opportunities to learn in some teacher preparation components are more important than in other components. 相似文献