全文获取类型
收费全文 | 11159篇 |
免费 | 1512篇 |
国内免费 | 2117篇 |
专业分类
化学 | 7345篇 |
晶体学 | 281篇 |
力学 | 649篇 |
综合类 | 185篇 |
数学 | 1711篇 |
物理学 | 4617篇 |
出版年
2024年 | 23篇 |
2023年 | 113篇 |
2022年 | 360篇 |
2021年 | 385篇 |
2020年 | 422篇 |
2019年 | 388篇 |
2018年 | 368篇 |
2017年 | 406篇 |
2016年 | 427篇 |
2015年 | 519篇 |
2014年 | 567篇 |
2013年 | 866篇 |
2012年 | 804篇 |
2011年 | 941篇 |
2010年 | 734篇 |
2009年 | 745篇 |
2008年 | 846篇 |
2007年 | 819篇 |
2006年 | 717篇 |
2005年 | 699篇 |
2004年 | 524篇 |
2003年 | 369篇 |
2002年 | 363篇 |
2001年 | 381篇 |
2000年 | 288篇 |
1999年 | 211篇 |
1998年 | 124篇 |
1997年 | 102篇 |
1996年 | 117篇 |
1995年 | 98篇 |
1994年 | 106篇 |
1993年 | 99篇 |
1992年 | 83篇 |
1991年 | 72篇 |
1990年 | 61篇 |
1989年 | 67篇 |
1988年 | 48篇 |
1987年 | 43篇 |
1986年 | 34篇 |
1985年 | 46篇 |
1984年 | 54篇 |
1983年 | 28篇 |
1982年 | 43篇 |
1981年 | 36篇 |
1980年 | 26篇 |
1979年 | 40篇 |
1978年 | 28篇 |
1976年 | 25篇 |
1975年 | 16篇 |
1974年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
Shui Cao ZHENG Huo Nan LIN Di He HU 《数学学报(英文版)》2005,21(5):1137-1148
In this paper, we investigate the Hausdorff measure for level sets of N-parameter Rd-valued stable processes, and develop a means of seeking the exact Hausdorff measure function for level sets of N-parameter Rd-valued stable processes. We show that the exact Hausdorff measure function of level sets of N-parameter Rd-valued symmetric stable processes of index α is Ф(r) = r^N-d/α (log log l/r)d/α when Nα 〉 d. In addition, we obtain a sharp lower bound for the Hausdorff measure of level sets of general (N, d, α) strictly stable processes. 相似文献
43.
44.
We deal with the problem of determining an inclusion within an electrostatic conductor from boundary measurements. Under mild a priori assumptions we establish optimal stability estimates. Measurements are performed on a portion of the boundary of the conductor. 相似文献
45.
根据广义Laguerre多项式的数学性质,导出了较为简单的三维各向同性谐振子径向矩阵元的普遍公式,并在这基础上计算了一些重要特殊情形的径向矩阵元: 矢径r整数次幂的平均值,电偶极跃迁矩阵元和电四极跃迁矩阵元.
关键词:
三维各向同性谐振子
径向矩阵元
广义Laguerre多项式
偶极跃迁
四极跃迁 相似文献
46.
This paper presents some properties of two restricted classes of multi-degree-of-freedom potential systems subjected to Gaussian white-noise excitations. Specifically, potential systems which exhibit damping terms with energy-dependent polynomial form are referred to. In this context, first systems with coupled stiffness terms and damping terms depending on the total energy are investigated. Then, systems with uncoupled stiffness terms and damping terms depending on the total energy in each degree-of-freedom are considered. For these two classes, it is found that algebraic relations among the stationary statistical moments of the energy functions can be derived by applying standard tools of Itô calculus. Further, it is noted that these relations are very useful within the framework of an equivalent statistical non-linearization technique to build approximate solutions for arbitrary non-linear systems. 相似文献
47.
Zero-schemes on smooth complex projective varieties, forcing all elements of ample and free linear systems to be reducible, are studied. Relationships among the minimal length of such zero-schemes, the positivity of the line bundle associated with the linear system, and the dimension of the variety are established. Bad linear spaces are also investigated. 相似文献
48.
本文介绍GaAs/AlAs超晶格的室温近共振喇曼散射测量结果。由于超晶格中Fr?hlich相互作用的共振增强效应,GaAs LO声子偶模的散射得到了很大的增强。和前人的结果一样,在偏振谱我们观察到了偶模。但和前人的结果不同,在退偏振谱中我们观察到的是奇模,而不是偶模。从而证明了在近共振条件下LO声子限制模仍遵从与非共振时一样的选择定则。二级喇曼散射实验结果表明,在偏振谱中二级谱是由两个偶模组合而成,而在退偏振谱中的二级谱与前人的结果不同,由一个奇模与一个偶模组合而成。上述结果与最近提出的黄朱模型的预言是一
关键词: 相似文献
49.
50.
Gabor Schmera Adi Bulsara David Pierson Frank Moss Enrico Di Cera 《Journal of statistical physics》1993,71(5-6):1179-1190
We consider the class of experiments which can be characterized by a Fokker-PIanck dynamics corresponding to the overdamped motion of a state point in a suitable stochastic potential. We assume that the general form of the potential is known (or can be guessed with reasonable accuracy), but that its parameters are to be determined experimentally by measurements made with a noisy instrument. This possible method for determining the potential parameters, which exploits the system's own internal stochastic motion in order to explore rapidly its available parameter space, is substantially more efficient than traditional methods involving time averages of single point measurements, and yet does not appear to have been previously considered. The method could be important when, for example, the experiment must be completed in a limited time owing either to the expense of the experimental materials or to the temporary stationarity of the preparation, situations which are commonly encountered in experimental biochemistry and biology. 相似文献