全文获取类型
收费全文 | 25606篇 |
免费 | 1981篇 |
国内免费 | 1922篇 |
专业分类
化学 | 2369篇 |
晶体学 | 53篇 |
力学 | 1727篇 |
综合类 | 246篇 |
数学 | 11868篇 |
物理学 | 2640篇 |
综合类 | 10606篇 |
出版年
2024年 | 50篇 |
2023年 | 169篇 |
2022年 | 292篇 |
2021年 | 361篇 |
2020年 | 436篇 |
2019年 | 606篇 |
2018年 | 611篇 |
2017年 | 614篇 |
2016年 | 641篇 |
2015年 | 661篇 |
2014年 | 1164篇 |
2013年 | 1552篇 |
2012年 | 1354篇 |
2011年 | 1659篇 |
2010年 | 1389篇 |
2009年 | 1687篇 |
2008年 | 1698篇 |
2007年 | 1912篇 |
2006年 | 1552篇 |
2005年 | 1266篇 |
2004年 | 1187篇 |
2003年 | 1110篇 |
2002年 | 958篇 |
2001年 | 706篇 |
2000年 | 770篇 |
1999年 | 684篇 |
1998年 | 573篇 |
1997年 | 538篇 |
1996年 | 455篇 |
1995年 | 397篇 |
1994年 | 379篇 |
1993年 | 366篇 |
1992年 | 319篇 |
1991年 | 280篇 |
1990年 | 238篇 |
1989年 | 195篇 |
1988年 | 163篇 |
1987年 | 112篇 |
1986年 | 60篇 |
1985年 | 66篇 |
1984年 | 37篇 |
1983年 | 31篇 |
1982年 | 40篇 |
1981年 | 40篇 |
1980年 | 32篇 |
1979年 | 25篇 |
1978年 | 25篇 |
1977年 | 17篇 |
1976年 | 8篇 |
1957年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
231.
232.
A mean-field model of nonlinearly coupled oscillators with randomly distributed frequencies and subject to independent external white noises is analyzed in the thermodynamic limit. When the frequency distribution isbimodal, new results include subcritical spontaneous stationary synchronization of the oscillators, supercritical time-periodic synchronization, bistability, and hysteretic phenomena. Bifurcating synchronized states are asymptotically constructed near bifurcation values of the coupling strength, and theirnonlinear stability properties ascertained. 相似文献
233.
234.
气体放电击穿过程的物理和数值研究 总被引:1,自引:0,他引:1
胡希伟 《核聚变与等离子体物理》1994,14(1):44-50
本文对低气压(10^-2Pa)热阴极气体放电的击穿过程给出了物理描述和相应的双流体数学型,并发展了一种选择和调整未知初始条件的有效算法,可以通过伴随试射法得到对初始条件十分敏感的非线性两点边值常微分方程组的数值解,从而给出这类气体放电中击穿过程的定量描述。 相似文献
235.
采用对比性试验,研究了接地电阻对火花放电击中点的影响.试验结果和观测均表明,接地电阻能抑制从接地端产生的迎面放电的发展速度和通道强度,从而使其被击中概率下降,负极性比正极性下接地电阻对火花放电击中点的影响要显著得多. 相似文献
236.
大学英语教学低起点高目标的反思及应对策略 总被引:1,自引:0,他引:1
本文结合目前大学英语教学现状及社会对外语人才的要求,尝试着探讨大学英语教学低起点的缘由和高目标要求的应对策略。其意在为大学外语教学建立特殊的机制,充分发挥教育资源的整合效益,起到优化教学过程,达到最优化教学效果,最终最大限度地满足社会对各类外语人才的需要。 相似文献
237.
研究了二阶常微分方程Stum—Liouville问题,通过使用不动点指数这一工具,在适当条件下建立了这类边值问题多正解存在的充分条件 相似文献
238.
Robert J. Daverman 《Topology and its Applications》2007,155(2):105-111
This paper sets forth three mismatch properties, strictly ordered in strength, about sewings of crumpled n-cubes. The strongest is a sufficient but not a necessary condition for a sewing to yield Sn, and the weakest, a necessary but not sufficient one. We show that when both crumpled cubes satisfies the Disjoint Disks Property, then the weakest property implies the sewing yields Sn, and we also show that the intermediate property leads to the same conclusion when just one of the crumpled cubes possesses the Disjoint Disks Property. In addition, we develop examples that confirm sharpness of the relevant Disjoint Disks conditions. 相似文献
239.
R.J. Gardner 《Advances in Mathematics》2007,216(1):358-386
This paper develops a significant extension of E. Lutwak's dual Brunn-Minkowski theory, originally applicable only to star-shaped sets, to the class of bounded Borel sets. The focus is on expressions and inequalities involving chord-power integrals, random simplex integrals, and dual affine quermassintegrals. New inequalities obtained include those of isoperimetric and Brunn-Minkowski type. A new generalization of the well-known Busemann intersection inequality is also proved. Particular attention is given to precise equality conditions, which require results stating that a bounded Borel set, almost all of whose sections of a fixed dimension are essentially convex, is itself essentially convex. 相似文献
240.
Hans Crauel 《Journal of Differential Equations》2007,234(2):412-438
We introduce the concept of “stabilization by rotation” for deterministic linear systems with negative trace. This concept encompasses the well-known concept of “vibrational stabilization” introduced by Meerkov in the 1970s and is a deterministic version of ‘stabilization by noise’ for stochastic systems as introduced by Arnold and coworkers in the 1980s. It is shown that a linear system with negative trace can be stabilized by adding a skew-symmetric matrix, multiplied by a suitable scalar so-called “gain function” (possibly a constant) which is sufficiently large. To overcome the problem of what is “sufficiently large”, we also present a servo mechanism which tunes the gain function by learning from the trajectory until finally the trajectory tends to zero. This approach allows to show that one of Meerkov's assumptions for vibrational stabilization is superfluous. Moreover, while Meerkov as well as Arnold and coworkers assume that a stabilizing periodic function or the noise has sufficiently large frequency and amplitude, we also provide a servo mechanism to determine this function dynamically in a deterministic setup. 相似文献