全文获取类型
收费全文 | 8834篇 |
免费 | 265篇 |
国内免费 | 25篇 |
专业分类
化学 | 5784篇 |
晶体学 | 68篇 |
力学 | 276篇 |
综合类 | 1篇 |
数学 | 1143篇 |
物理学 | 1852篇 |
出版年
2023年 | 62篇 |
2022年 | 200篇 |
2021年 | 274篇 |
2020年 | 165篇 |
2019年 | 182篇 |
2018年 | 167篇 |
2017年 | 156篇 |
2016年 | 349篇 |
2015年 | 260篇 |
2014年 | 283篇 |
2013年 | 530篇 |
2012年 | 575篇 |
2011年 | 606篇 |
2010年 | 456篇 |
2009年 | 416篇 |
2008年 | 544篇 |
2007年 | 524篇 |
2006年 | 414篇 |
2005年 | 378篇 |
2004年 | 306篇 |
2003年 | 285篇 |
2002年 | 237篇 |
2001年 | 174篇 |
2000年 | 152篇 |
1999年 | 112篇 |
1998年 | 95篇 |
1997年 | 83篇 |
1996年 | 93篇 |
1995年 | 80篇 |
1994年 | 75篇 |
1993年 | 62篇 |
1992年 | 67篇 |
1991年 | 55篇 |
1990年 | 54篇 |
1989年 | 45篇 |
1988年 | 43篇 |
1987年 | 31篇 |
1986年 | 44篇 |
1985年 | 66篇 |
1984年 | 44篇 |
1983年 | 38篇 |
1982年 | 29篇 |
1981年 | 27篇 |
1980年 | 38篇 |
1979年 | 32篇 |
1978年 | 32篇 |
1977年 | 16篇 |
1976年 | 26篇 |
1975年 | 22篇 |
1973年 | 21篇 |
排序方式: 共有9124条查询结果,搜索用时 15 毫秒
21.
Lui Lam Flonnie Dowell Helmut Brand Guenter Ahlers 《Journal of statistical physics》1991,64(5-6):899-901
22.
On a recursive method for the estimation of unknown parameters of partially observed chaotic systems
We investigate a recently proposed method for on-line parameter estimation and synchronization in chaotic systems. This novel technique has been shown effective to estimate a single unknown parameter of a primary chaotic system with known functional form that is only partially observed through a scalar time series. It works by periodically updating the parameter of interest in a secondary system, with the same functional form as the primary one but no explicit coupling between their dynamic variables, in order to minimize a suitably defined cost function. In this paper, we review the basics of the method, and investigate its robustness and new extensions. In particular, we study the performance of the novel technique in the presence of noise (either observational, i.e., an additive contamination of the observed time series, or dynamical, i.e., a random perturbation of the system dynamics) and when there is a mismatch between the primary and secondary systems. Numerical results, including comparisons with other techniques, are presented. Finally, we investigate the extension of the original method to perform the estimation of two unknown parameters and illustrate its effectiveness by means of computer simulations. 相似文献
23.
L. G. Marcassa V. A. Nascimento L. L. Caliri A. Caires D. V. Magalhães V. S. Bagnato 《Laser Physics》2006,16(12):1722-1725
In this paper, we report observation of an enhancement of the ground state molecule Rb2 formation in a Rb magneto-optical trap due to a photoassociation laser. Such an enhancement effect is due to flux enhancement of atomic pairs at short internuclear distances. Our experimental observations consist in the measurement of the molecular formation rate constant due to a probe laser as a function of the trap laser intensity. The results are compared with a simple semi-classical model, showing good agreement. We conclude that the production of cold Rb2 may be enhanced using appropriate laser parameters; this may be useful for future experiments involving production and trapping of ultracold ground state molecules. 相似文献
24.
Magnetization measurements in the (Dy
x
Y1−x
)Fe2 intermetallic compounds show evidence of blocking of domain wall motion. This effect is a function of concentrationx. The direction of magnetization is also dependent on the Dy concentration. We have used the Mossbauer spectroscopy of57Fe to verify the direction of magnetization in the series as a function ofx and temperature. The results show that this change in easy direction occurs at higher temperatures than those where the blocking
is detected through DC magnetization measurements.
supported by RHAE/SCT. 相似文献
25.
We study interpolation, generated by an abstract method of means, of bilinear operators between quasi-Banach spaces. It is
shown that under suitable conditions on the type of these spaces and the boundedness of the classical convolution operator
between the corresponding quasi-Banach sequence spaces, bilinear interpolation is possible. Applications to the classical
real method spaces, Calderón-Lozanovsky spaces, and Lorentz-Zygmund spaces are presented.
The author is supported by the National Science Foundation under grant DMS 0099881.
The author is supported by KBN Grant 1 P03A 013 26. 相似文献
26.
27.
Mössbauer effect studies of Pt3−xFe1+x fcc ordered alloys in the range 4.2 K <T<300 K, in zero and in external magnetic field, for samples with x = 0.16 to 0.28, are reported. The low-temperature spectra show several satellite lines which are related to different excess-Fe nearest-neighbor configurations. Experiments in external fields give information on the different local spin structure at different concentrations. 相似文献
28.
29.
30.