全文获取类型
收费全文 | 1945篇 |
免费 | 183篇 |
国内免费 | 115篇 |
专业分类
化学 | 269篇 |
晶体学 | 9篇 |
力学 | 103篇 |
综合类 | 58篇 |
数学 | 1193篇 |
物理学 | 611篇 |
出版年
2024年 | 3篇 |
2023年 | 30篇 |
2022年 | 30篇 |
2021年 | 48篇 |
2020年 | 51篇 |
2019年 | 53篇 |
2018年 | 57篇 |
2017年 | 86篇 |
2016年 | 94篇 |
2015年 | 59篇 |
2014年 | 145篇 |
2013年 | 142篇 |
2012年 | 94篇 |
2011年 | 101篇 |
2010年 | 97篇 |
2009年 | 127篇 |
2008年 | 124篇 |
2007年 | 117篇 |
2006年 | 101篇 |
2005年 | 89篇 |
2004年 | 67篇 |
2003年 | 65篇 |
2002年 | 68篇 |
2001年 | 54篇 |
2000年 | 63篇 |
1999年 | 58篇 |
1998年 | 46篇 |
1997年 | 29篇 |
1996年 | 21篇 |
1995年 | 11篇 |
1994年 | 19篇 |
1993年 | 16篇 |
1992年 | 6篇 |
1991年 | 15篇 |
1990年 | 8篇 |
1989年 | 3篇 |
1988年 | 8篇 |
1987年 | 2篇 |
1986年 | 6篇 |
1985年 | 8篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 8篇 |
1981年 | 3篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1936年 | 1篇 |
排序方式: 共有2243条查询结果,搜索用时 328 毫秒
81.
C-H. Chu R. V. Hü gli M. Mackey 《Proceedings of the American Mathematical Society》2004,132(11):3305-3308
Let be the Banach algebra of bounded holomorphic functions on the open unit ball of a Banach space. We show that the identity operator is an isolated point in the space of composition operators on . This answers a conjecture of Aron, Galindo and Lindström.
82.
Monika Budzynska 《Proceedings of the American Mathematical Society》2003,131(9):2771-2777
If is the open unit ball in the Cartesian product furnished with the -norm , where and , then a holomorphic self-mapping of has a fixed point if and only if for some
83.
We study a two-layer neural network made of N and M(N) neurons, producing a two-way association search for a family of p(N) patterns, where each pattern is a pair of two independent sub-categories of information having respectively N and M(N) components. In terms of the ratio =lim
N
M(N)/N, we study the retrieval capability of this network and show that there exists, at least, three regimes of association for which we determine the evolution of the threshold
c
() of the storage capacity =lim
N
p(N)/N. 相似文献
84.
J. Garcí a-Meliá n R. Letelier-Albornoz J. Sabina de Lis 《Proceedings of the American Mathematical Society》2001,129(12):3593-3602
In this paper we prove uniqueness of positive solutions to logistic singular problems , , 1$">, 0$"> in , where the main feature is the fact that . More importantly, we provide exact asymptotic estimates describing, in the form of a two-term expansion, the blow-up rate for the solutions near . This expansion involves both the distance function and the mean curvature of .
85.
Properties of target species can be estimated by various means including interpolations in periodic charts. Interpolation is equivalent to numerical solution of the Laplace equation. A test of this equivalence, within some confidence level, for any N-atomic molecule surrounded by 4N nearest neighbors: the sum of the second differences of the data in all directions must be zero. Since very few molecules have 4N neighbors with known data, the test becomes: the sum of the averages of the second differences must be zero. The validity of these tests is explored. For radii of main-group atoms, and for internuclear separations of their diatomic combinations, the averages are different from zero and the sums of the averages are zero to within one if second-nearest neighbors are used. Dissociation potentials pass the tests but with larger scatter. Predictions for dissociation potentials, using iterative interpolation within boundaries on which there are known data, are reviewed. 相似文献
86.
Pannier M Veit S Godt A Jeschke G Spiess HW 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2000,142(2):331-340
A four-pulse version of the pulse double electron-electron resonance (DEER) experiment is presented, which is designed for the determination of interradical distances on a nanoscopic length-scale. With the new pulse sequence electron-electron couplings can be studied without dead-time artifacts, so that even broad distributions of electron-electron distances can be characterized. A version of the experiment that uses a pulse train in the detection period exhibits improved signal-to-noise ratio. Tests on two nitroxide biradicals with known length indicate that the accessible range of distances extends from about 1.5 to 8 nm. The four-pulse DEER spectra of an ionic spin probe in an ionomer exhibit features due to probe molecules situated both on the same and on different ion clusters. The former feature provides information on the cluster size and is inaccessible with previous methods. 相似文献
87.
88.
通过研究爬壁式机器人的控制和运动特征,提出一种基于复小波包分形理论的故障检测方法.利用复小波包的平移不变性,将爬壁式机器人传感器输出信号分解成独立的频谱,并进行阀值处理和重构,从而有效去除高频噪音并提取故障的特征频率;依据信号分形维数的多尺度不变性,在嵌入维数空间,采用维数最大距离法,确定复小波包域故障信号的关联雏数.仿真实验表明,爬壁式机器人在各种异常工作模式下的故障信号关联维数能比较真实地反映其故障状态空间,同时也验证了故障信号的关联维数低于正常信号的关联维数作为故障发生与否的定量判据的正确性. 相似文献
89.
The main aim of this paper is to establish an Ostrowski type inequality on H-type groups using the L∞ norm of the horizontal gradient. The work has been motivated by the work of Anastassiou and Goldstein in [G.A. Anastassiou, J.A. Goldstein, Higher order Ostrowski type inequalities over Euclidean domains, J. Math. Anal. Appl. 337 (2008) 962-968]. 相似文献
90.
本文推广Vogt定理到广义n-赋范空间,即证明了两个广义n-赋范空间之间的保持ρ-诱导距离映射是仿射的. 相似文献