全文获取类型
收费全文 | 24434篇 |
免费 | 289篇 |
国内免费 | 62篇 |
专业分类
教育 | 17523篇 |
科学研究 | 2212篇 |
各国文化 | 217篇 |
体育 | 1759篇 |
综合类 | 45篇 |
文化理论 | 131篇 |
信息传播 | 2898篇 |
出版年
2021年 | 275篇 |
2020年 | 360篇 |
2019年 | 524篇 |
2018年 | 773篇 |
2017年 | 788篇 |
2016年 | 732篇 |
2015年 | 474篇 |
2014年 | 692篇 |
2013年 | 4612篇 |
2012年 | 640篇 |
2011年 | 679篇 |
2010年 | 579篇 |
2009年 | 561篇 |
2008年 | 610篇 |
2007年 | 560篇 |
2006年 | 560篇 |
2005年 | 507篇 |
2004年 | 407篇 |
2003年 | 364篇 |
2002年 | 350篇 |
2001年 | 524篇 |
2000年 | 449篇 |
1999年 | 398篇 |
1998年 | 239篇 |
1997年 | 273篇 |
1996年 | 262篇 |
1995年 | 207篇 |
1994年 | 238篇 |
1993年 | 200篇 |
1992年 | 350篇 |
1991年 | 314篇 |
1990年 | 330篇 |
1989年 | 343篇 |
1988年 | 286篇 |
1987年 | 269篇 |
1986年 | 283篇 |
1985年 | 276篇 |
1984年 | 254篇 |
1983年 | 249篇 |
1982年 | 189篇 |
1981年 | 202篇 |
1980年 | 186篇 |
1979年 | 283篇 |
1978年 | 216篇 |
1977年 | 170篇 |
1976年 | 168篇 |
1975年 | 156篇 |
1974年 | 157篇 |
1973年 | 154篇 |
1971年 | 152篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
48 healthy neonates born to multiparae were randomly assigned to view a moving stimulus either in the horizontal or the upright position, with or without added vestibular stimulation and with or without pacifier sucking. The infant was shown a moving black line inside a strictly controlled visual environment provided by an apparatus which permitted horizontal and upright positioning and displacement of the infant. Visual tracking was recorded by a concealed TV camera positioned at a constant distance and angle from the infants' eyes in both positions. Quality of tracking during each of 4 trials was scored on a 7-point scale. Results indicate that vestibularproprioceptive stimulation provided to the infant either horizontally or semivertically significantly enhanced his visual tracking, whereas the upright position did not. Pacifier sucking also improved his performace. 相似文献
102.
103.
104.
This paper introduces a polynomial operator called the DT-polynomial as a novel approach to network flow problems. The class of networks dealt with is time-varying in the sense that the capacity, cost, and travel-time of each edge may vary in discrete time. The Dt-polynomial is a polynomial in two operators, D (delay) and T (time), which is used for describing the time-varying transmission characteristics. The paper starts with the mathematics involving the DT-polynomials. A new shortest arrival route algorithm is presented, and its computational complexity is found to be favorable in comparison with others such as Dijkstra's method and the potential method derived from Ford-Fulkerson's technique. Furthermore, a dynamic flow problem is formulated and analyzed in terms of DT-polynomials, and a latest-departure earliest-arrival schedule is given. Finally, a modified DT-polynomial is applied to digital filter networks. 相似文献
105.
Yudell L. Luke 《Journal of The Franklin Institute》1978,305(5):259-273
Uniform asymptotic estimates for the error in the main diagonal and first two subdiagonal Padé approximants for exp(iz) in a sector covering the real z axis are derived. The results are applied to analyze the error in a cerain procedure for the numerical inversion of the Laplace transform. 相似文献
106.
To examine the developmental significance of mirrow self-recognition in early childhood, a cross-sectional study with 55 Down's syndrome children was conducted. When their image is altered by rouge on the nose, normal infants by 22 months indicate self-recognition by touching their noses while looking in the mirror. Only a small percentage of Down's syndrome children touched their noses by this age, confirming the expected lag in this development. However, those young Down's syndrome infants with near-normal development quotient did manifest the reaction. In general, when developmental age was equated, the Down's syndrome children showed parallel development to normal children. 相似文献
107.
In an attempt to clarify the chronological relationship between identity and equivalence conservation, normal preschool-aged children (experiment 1) were exposed to brief videotape demonstrations of a model conserving identity and equivalence, identity only, equivalence only, or neither. Subsequent performances indicate that identity was easier to accelerate than equivalence, and training in both identity and equivalence appeared to be most effective in accelerating conservation. Trainable mentally retarded (TMR) children were then exposed to either the identity-equivalence-conserving or control model (experiment 2). This population, which some have argued remains at a preoperational level of functioning, was more likely to conserve identity than equivalence. In addition, conservation in the training group increased following training, though these gains were not maintained over a 3-week retention interval. 相似文献
108.
93 first graders (mean age 6.5 years) were given a pretest and posttest on half of the items from the Children's Embedded Figures Test. Half of the children were randomly assigned to a training condition and received a brief training procedure on visual-spatial disembedding prior to the administration of the posttest. Children in the control condition received no training. The performance of girls improved significantly more from pretest to posttest than the performance of boys. Boys and girls showed similar beneficial effects of training in addition to the benefit of direct practice. The tendency that was observed for boys to perform higher than girls on the pretest, p less than .10, was not evident on the posttest. Scores on the pretest predicted scores on a different measure of visual-spatial ability only for children in the control group. The results are interpreted in terms of current theories of sex differences in visual-spatial perception. 相似文献
109.
The reproducibility of microwave integrated circuits can be improved by employing substrates which are anisotropic. A method is presented which facilitates the computation of the characteristics of distributed integrated microwave circuits of finite conductor thickness on anisotropic and inhomogeneous substrates. The method is variational and it relies on a quasi-static approach which assumes that the charge distribution on each side of the conductor can be represented by a spatially dependent set of exponential functions. 相似文献
110.
The behavior of narcotics-addicted and nonaddicted newborns on the first 2 days of life was assessed with the Brazelton Neonatal Behavioral Assessment Scale. In addition to classic signs of narcotics abstinence, addicted infants were less able to be maintained in an alert state and less able to orient to auditory and visual stimuli. These deficits were especially pronounced at 48 hours of age. Addicted infants were as capable of self-quieting and responding to soothing intervention as normal neonates, although they were substantially more irritable. These characteristics and addicted infants' greater resistance to cuddling are discussed in terms of their potential impact on early infant-care-giver interaction. 相似文献