全文获取类型
收费全文 | 4832篇 |
免费 | 547篇 |
国内免费 | 520篇 |
专业分类
化学 | 2148篇 |
晶体学 | 14篇 |
力学 | 695篇 |
综合类 | 29篇 |
数学 | 771篇 |
物理学 | 2242篇 |
出版年
2024年 | 10篇 |
2023年 | 75篇 |
2022年 | 218篇 |
2021年 | 218篇 |
2020年 | 318篇 |
2019年 | 245篇 |
2018年 | 229篇 |
2017年 | 237篇 |
2016年 | 317篇 |
2015年 | 280篇 |
2014年 | 277篇 |
2013年 | 291篇 |
2012年 | 264篇 |
2011年 | 293篇 |
2010年 | 186篇 |
2009年 | 221篇 |
2008年 | 226篇 |
2007年 | 231篇 |
2006年 | 254篇 |
2005年 | 190篇 |
2004年 | 203篇 |
2003年 | 179篇 |
2002年 | 165篇 |
2001年 | 144篇 |
2000年 | 86篇 |
1999年 | 71篇 |
1998年 | 91篇 |
1997年 | 74篇 |
1996年 | 47篇 |
1995年 | 48篇 |
1994年 | 29篇 |
1993年 | 22篇 |
1992年 | 27篇 |
1991年 | 15篇 |
1990年 | 18篇 |
1989年 | 17篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 9篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 10篇 |
1981年 | 5篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 4篇 |
1977年 | 3篇 |
1975年 | 3篇 |
1957年 | 2篇 |
排序方式: 共有5899条查询结果,搜索用时 15 毫秒
81.
82.
基于错误概率达到最小的原则,该文在罐子模型序贯试验中构造了一种渐近最优设计。在这种设计下,不仅能使病员以较多机会分配到较好的处理,而且能使估计量的统计效率在一定意义下达到最优。 相似文献
83.
大学物理实验的双任务教学方法初探 总被引:5,自引:1,他引:4
为搭建课程改革与学习效果之间的桥梁,在大学物理实验中引入了双任务教学方法.本文介绍了双任务教学法的概念、优点及具体实施方法. 相似文献
84.
85.
86.
87.
Leslie P Steffe 《The Journal of Mathematical Behavior》2003,22(3):237-295
A case study of two 5th-Grade children, Jason and Laura, is presented who participated in the teaching experiment, Children’s Construction of the Rational Numbers of Arithmetic. The case study begins on the 29th of November of their 5th-Grade in school and ends on the 5th of April of the same school year. Two basic problems were of interest in the case study. The first was to provide an analysis of the concepts and operations that are involved in the construction of three fractional schemes: a commensurate fractional scheme, a fractional composition scheme, and a fractional adding scheme. The second was to provide an analysis of the contribution of interactive mathematical activity in the construction of these schemes. The phrase, “commensurate factional scheme” refers to the concepts and operations that are involved in transforming a given fraction into another fraction that are both measures of an identical quantity. Likewise, “fractional composition scheme” refers to the concepts and operations that are involved in finding how much, say, 1/3 of 1/4 of a quantity is of the whole quantity, and “fractional adding scheme” refers to the concepts and operations involved in finding how much, say, 1/3 of a quantity joined to 1/4 of a quantity is of the whole quantity. Critical protocols were abstracted from the teaching episodes with the two children that illustrate what is meant by the schemes, changes in the children’s concepts and operations, and the interactive mathematical activity that was involved. The body of the case study consists of an on-going analysis of the children’s interactive mathematical activity and changes in that activity. The last section of the case study consists of an analysis of the constitutive aspects of the children’s constructive activity, including the role of social interaction and nonverbal interactions of the children with each other and with the computer software we used in teaching the children. 相似文献
88.
89.
90.
Mei‐Jiau Huang 《国际流体数值方法杂志》2005,48(5):521-539
The technique of splitting a fat vortex element (with a core width larger than some threshold) into some thin ones in order to fix the convergence problem of the core‐spreading vortex methods is convenient and efficient. In particular, it keeps the method purely Lagrangian. In the present investigation, the splitting process is further viewed as part of the physical diffusion process. A new splitting method in which several weaker child vortices surround a thinned but still strong parent vortex is proposed. It is found that because of the survival of the parent vortex, the error arising from the splitting events can be largely reduced. The computational amount on the other hand is kept reasonably large by merging similar and close‐by vortices. The merging scheme designed herein not only involves fewer restrictions but also allows merging vortices of opposite rotations through the viewpoint of remeshing. The validity and accuracy of these techniques, proposed particularly for simulations undergoing lots of splitting and merging events, are verified by successfully simulating the interactions between two Burgers vortices under an external straining field. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献