全文获取类型
收费全文 | 12018篇 |
免费 | 288篇 |
国内免费 | 97篇 |
专业分类
化学 | 8320篇 |
晶体学 | 238篇 |
力学 | 259篇 |
综合类 | 1篇 |
数学 | 2054篇 |
物理学 | 1531篇 |
出版年
2022年 | 95篇 |
2021年 | 121篇 |
2020年 | 141篇 |
2019年 | 130篇 |
2018年 | 100篇 |
2017年 | 100篇 |
2016年 | 245篇 |
2015年 | 196篇 |
2014年 | 220篇 |
2013年 | 599篇 |
2012年 | 562篇 |
2011年 | 649篇 |
2010年 | 344篇 |
2009年 | 305篇 |
2008年 | 602篇 |
2007年 | 642篇 |
2006年 | 609篇 |
2005年 | 567篇 |
2004年 | 506篇 |
2003年 | 396篇 |
2002年 | 470篇 |
2001年 | 126篇 |
2000年 | 133篇 |
1999年 | 128篇 |
1998年 | 124篇 |
1997年 | 158篇 |
1996年 | 195篇 |
1995年 | 126篇 |
1994年 | 123篇 |
1993年 | 132篇 |
1992年 | 130篇 |
1991年 | 113篇 |
1990年 | 128篇 |
1989年 | 115篇 |
1988年 | 115篇 |
1987年 | 91篇 |
1986年 | 102篇 |
1985年 | 182篇 |
1984年 | 193篇 |
1983年 | 138篇 |
1982年 | 225篇 |
1981年 | 191篇 |
1980年 | 167篇 |
1979年 | 156篇 |
1978年 | 149篇 |
1977年 | 135篇 |
1976年 | 144篇 |
1975年 | 129篇 |
1974年 | 149篇 |
1973年 | 132篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
53.
54.
55.
56.
Stochastic resonance is a statistical phenomenon that has been observed in periodically modulated, noise-driven, bistable systems. The characteristic signatures of the effect include an increase in the signal-to-noise of the output as noise is added to the system, and exponentially decreasing peaks in the probability density as a function of residence times in one state. Presented are the results of a numerical simulation where these same signatures were observed by adding achaotic driving term instead of a white noise term. Although the probability distributions of the noise and chaos inputs were significantly different, the stochastic and chaotic resonances were equal within the experimental error. 相似文献
57.
William M. Carroll 《School science and mathematics》1998,98(4):188-197
National and international studies have found U.S. elementary students to be weak in their understandings and applications of geometric concepts. The University of Chicago School Mathematics Project's (UCMSP) Everyday Mathematics Program is one of the current reform-based elementary curricula incorporating geometry throughout the K-6 curriculum, with an emphasis on hands-on and problem-solving activities. In this study, the geometric knowledge of fifth and sixth graders using the UCSMP curriculum is compared to the knowledge of students using more traditional curricula. Because UCSMP students had been in the program since kindergarten, this research attempts to measure the longitudinal effects of such an approach. Along with an overall score, a subset of test items was used to assign each student a van Hiele level for geometric thinking, as well as a reasoning score. On all measures, UCSMP students substantially outperformed their counterparts, and nearly all differences were significant. Aspects of the UCSMP curriculum and the van Hiele model for learning geometry are discussed relative to these results. 相似文献
58.
We calculate the temperature-dependent energy gap in the magnetic excitations spectrum of the two-dimensional antiferromagnet in the presence of a staggered magnetic field, using the nonlinear sigma model. 相似文献
59.
60.
We show that a theorem of Shchepin and Repovš concerning the smoothness of compacta follows from the theory of semicontinuous relations. 相似文献