全文获取类型
收费全文 | 693篇 |
免费 | 97篇 |
国内免费 | 11篇 |
专业分类
化学 | 40篇 |
晶体学 | 2篇 |
力学 | 26篇 |
综合类 | 2篇 |
数学 | 47篇 |
物理学 | 684篇 |
出版年
2024年 | 4篇 |
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 8篇 |
2020年 | 12篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 30篇 |
2016年 | 53篇 |
2015年 | 18篇 |
2014年 | 72篇 |
2013年 | 25篇 |
2012年 | 23篇 |
2011年 | 53篇 |
2010年 | 44篇 |
2009年 | 64篇 |
2008年 | 65篇 |
2007年 | 49篇 |
2006年 | 29篇 |
2005年 | 36篇 |
2004年 | 23篇 |
2003年 | 24篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 19篇 |
1999年 | 10篇 |
1998年 | 10篇 |
1997年 | 11篇 |
1996年 | 5篇 |
1995年 | 10篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有801条查询结果,搜索用时 15 毫秒
101.
102.
Summary We derive an explicit form for the current correlation function of a Fermi gas in a finite sample at arbitrary degree of degeneracy.
The expression so found enables a continuous investigation from diffusive to ballistic transport regimes to be carried out.
For degenerate one-dimensional conductors under ballistic regime we find that the noise spectral density exhibits characteristic
geometrical resonances and its low-frequency value has the universal formS
I
(0)=8e
2
KT/h, implying a universal conductanceG=2e
2/h. 相似文献
103.
Apartments that are exposed to the same level of road traffic noise on front of the most exposed façade often have very different neighbourhood soundscapes. In the first part of this paper, a neighbourhood soundscape adjusted exposure indicator, NALden, is derived. NALden-values are designed to be used as input to traditional exposure-effect relationships to improve annoyance impact estimates. In the second part, generic spatial procedures are developed and implemented. These produce map presentations in the form of contiguous neighbourhood quality areas. The quality of each neighbourhood is determined from the predicted annoyance impacts for residents. Noise impact maps provide experts, politicians, and the public with high-level impact visualizations of condensed status, “what-if” and scenario information. Results and illustrations are based on data from the Norwegian socio-environmental survey database, and a comprehensive national noise mapping effort. The methodology should work well for mapping Europe’s “black” and “grey” areas. 相似文献
104.
A review of commonly used analytical and empirical formulae for predicting sound diffracted by a thin screen 总被引:2,自引:0,他引:2
This paper reviews some useful analytical and empirical formulae that are used for the calculation of sound diffracted by a barrier. A brief historic overview of the study of spherical waves diffracted by a rigid half plane is presented also. The physical principles of sound diffraction by a thin plane are explained. The mathematical expressions are cast in a convenient form for ease of numerical implementation. Accurate analytical solutions are expressed in terms of standard mathematical functions that can be computed readily. Among the approximate solutions quoted, quite a few empirical formulations are adequate for most engineering purposes. The information presented in this paper should also be helpful for those who are interested in the study of sound diffracted by a barrier in a room or in a long industrial space. 相似文献
105.
106.
107.
We present detailed multi-channel experimental characterization of different configurations of single pump hybrid Raman-erbium doped fiber (EDF) amplifiers. The incorporation of an EDF section in a dispersion compensating Raman amplifier is demonstrated to provide superior performance than Raman only system. It is shown that the multi-channel gain spectrum is quite different form the single-channel case. We have also measured the polarization dependent gain (PDG) of the hybrid amplifier configurations and results show that different configurations of hybrid amplifiers have different PDG effects on long-haul optically amplified link. 相似文献
108.
The problem of attenuating the noise from weapons firing is studied experimentally and numerically. As a possible method of attenuating the noise significantly, a silencer with no internal baffles is attached to the M242 cannon. The internal pressures inside the muffler are measured. The near-field overpressures outside the muffler at various polar angles are also measured. A numerical simulation of the flow through the muffler is performed, using Harten's shock-capturing method to solve the Euler equations of ideal compressible flow. The numerical simulation yields a detailed picture of the flow field as displayed by the pressure and Mach contours. Pressure–time curves at selected locations are obtained and compared with experimental data. There is good agreement, except that the numerical simulation generates more vigorous oscillations. 相似文献
109.
Roy A. Walters 《国际流体数值方法杂志》1983,3(6):591-604
Numerical noise has been a problem with finite element solutions to the shallow water equations. Two methods used to reduce the noise level are evaluated, and these results are compared with published results for equal-order interpolations. The two methods are mixed-interpolation (quadratic interpolation for velocity and linear interpolation for sea level) and a spectral form of the wave equation. Whereas mixed interpolation removes the troublesome sea level mode, it can still have considerable noise in velocity. The spectral wave equation is efficient and does not contain the spurious eigenmodes which contribute to high noise levels. 相似文献
110.
Network analysis based on low-rank method for mining information on integrated data of multi-cancers
The noise problem of cancer sequencing data has been a problem that can’t be ignored. Utilizing considerable way to reduce noise of these cancer data is an important issue in the analysis of gene co-expression network. In this paper, we apply a sparse and low-rank method which is Robust Principal Component Analysis (RPCA) to solve the noise problem for integrated data of multi-cancers from The Cancer Genome Atlas (TCGA). And then we build the gene co-expression network based on the integrated data after noise reduction. Finally, we perform nodes and pathways mining on the denoising networks. Experiments in this paper show that after denoising by RPCA, the gene expression data tend to be orderly and neat than before, and the constructed networks contain more pathway enrichment information than unprocessed data. Moreover, learning from the betweenness centrality of the nodes in the network, we find some abnormally expressed genes and pathways proven that are associated with many cancers from the denoised network. The experimental results indicate that our method is reasonable and effective, and we also find some candidate suspicious genes that may be linked to multi-cancers. 相似文献