全文获取类型
收费全文 | 38352篇 |
免费 | 487篇 |
国内免费 | 28篇 |
专业分类
教育 | 26401篇 |
科学研究 | 4730篇 |
各国文化 | 363篇 |
体育 | 2845篇 |
综合类 | 16篇 |
文化理论 | 274篇 |
信息传播 | 4238篇 |
出版年
2021年 | 379篇 |
2020年 | 545篇 |
2019年 | 866篇 |
2018年 | 1167篇 |
2017年 | 1119篇 |
2016年 | 973篇 |
2015年 | 624篇 |
2014年 | 897篇 |
2013年 | 7269篇 |
2012年 | 924篇 |
2011年 | 922篇 |
2010年 | 727篇 |
2009年 | 703篇 |
2008年 | 761篇 |
2007年 | 709篇 |
2006年 | 637篇 |
2005年 | 606篇 |
2004年 | 574篇 |
2003年 | 533篇 |
2002年 | 516篇 |
2001年 | 698篇 |
2000年 | 605篇 |
1999年 | 556篇 |
1998年 | 336篇 |
1997年 | 345篇 |
1996年 | 401篇 |
1995年 | 346篇 |
1994年 | 308篇 |
1993年 | 359篇 |
1992年 | 518篇 |
1991年 | 510篇 |
1990年 | 505篇 |
1989年 | 503篇 |
1988年 | 422篇 |
1987年 | 471篇 |
1986年 | 472篇 |
1985年 | 516篇 |
1984年 | 421篇 |
1983年 | 399篇 |
1982年 | 372篇 |
1981年 | 312篇 |
1980年 | 309篇 |
1979年 | 466篇 |
1978年 | 375篇 |
1977年 | 330篇 |
1976年 | 308篇 |
1975年 | 258篇 |
1974年 | 292篇 |
1973年 | 256篇 |
1971年 | 284篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
131.
The relationship between peak height velocity and physical performance in youth soccer players 总被引:1,自引:1,他引:0
Philippaerts RM Vaeyens R Janssens M Van Renterghem B Matthys D Craen R Bourgois J Vrijens J Beunen G Malina RM 《Journal of sports sciences》2006,24(3):221-230
Longitudinal changes in height, weight and physical performance were studied in 33 Flemish male youth soccer players from the Ghent Youth Soccer Project. The players' ages at the start of the study ranged from 10.4 to 13.7 years, with a mean age of 12.2 +/- 0.7 years. Longitudinal changes were studied over a 5 year period. Peak height velocity and peak weight velocity were determined using non-smoothed polynomials. The estimations of peak height velocity, peak weight velocity and age at peak height velocity were 9.7 +/- 1.5 cm x year-1, 8.4 +/- 3.0 kg x year-1 and 13.8 +/- 0.8 years, respectively. Peak weight velocity occurred, on average, at the same age as peak height velocity. Balance, speed of limb movement, trunk strength, upper-body muscular endurance, explosive strength, running speed and agility, cardiorespiratory endurance and anaerobic capacity showed peak development at peak height velocity. A plateau in the velocity curves was observed after peak height velocity for upper-body muscular endurance, explosive strength and running speed. Flexibility exhibited peak development during the tear after peak height velocity. Trainers and coaches should be aware of the individual characteristics of the adolescent growth spurt and the training load should also be individualized at this time. 相似文献
132.
133.
The graph-theoretic field model— II. application of multi-terminal representations to field problems
This paper is a sequel to a paper entitled “The Graph-Theoretic Field Model—I: Modelling and Formulations” (1). Herein, the Theory of Multi-Terminal Representations is applied to the Graph-Theoretic Field Model to provide mathematical models of finite elements. The element models are obtained solely from the algebraic building blocks of the Graph-Theoretic Field Model, without recourse to any functional mathematics. The theory of Multi-Terminal Representations is developed for both linear and non-linear problems. Examples of the application of the theory to one- and two-dimensional field problems are presented from heat conduction and electrostatics. 相似文献
134.
A.M. Morshedi 《Journal of The Franklin Institute》1980,310(2):89-105
Optimum process operating conditions are often achieved by on-line computer programming. A general method has been developed which is capable of optimizing processes whose responses are corrupted by random error. The method is particularly useful for application to processes whose response functions contain sharp ridges. Application to ridge and non-ridge systems gives the same results in each case showing that the rate of convergence of the search is totally unaffected by the presence of a ridge. An accelarated gradient method is used which obtains its derivatives from a quadratic interpolation. The inability of the gradient method to move along a ridge is overcome by projecting a straight line through points on the ridge to obtain new starting points for a gradient search. Points on the ridge are located by finding the stationary point of the polynomial which is constructed by regression through points found by the gradient search. The method is applied to several test functions known to the literature—a fast convergence rate is obtained for a wide range of noise levels. 相似文献
135.
136.
137.
J.M. Bowsher 《Endeavour》1980,4(1):20-25
The design of musical instruments owes more to art than to science and assessment of their quality is essentially subjective. Nevertheless, the physical principles of their operation are very interesting and may be of practical importance. This article reviews the acoustics of brass wind instruments, regarding the player and his instrument as an entity, and compares experimental and theoretical results. 相似文献
138.
139.
140.
F. Fallside 《Endeavour》1979,3(2):63-68
While the majority of those afflicted with deafness must still seek relief by conventional methods, new technological developments open up the possibility of aids of quite novel kinds. This article reviews the principal lines of research now being pursued. 相似文献