全文获取类型
收费全文 | 1407篇 |
免费 | 90篇 |
国内免费 | 52篇 |
专业分类
化学 | 170篇 |
晶体学 | 2篇 |
力学 | 18篇 |
综合类 | 1篇 |
数学 | 116篇 |
物理学 | 369篇 |
无线电 | 873篇 |
出版年
2024年 | 4篇 |
2023年 | 18篇 |
2022年 | 8篇 |
2021年 | 22篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 32篇 |
2017年 | 55篇 |
2016年 | 38篇 |
2015年 | 39篇 |
2014年 | 74篇 |
2013年 | 117篇 |
2012年 | 68篇 |
2011年 | 75篇 |
2010年 | 77篇 |
2009年 | 65篇 |
2008年 | 92篇 |
2007年 | 84篇 |
2006年 | 71篇 |
2005年 | 61篇 |
2004年 | 42篇 |
2003年 | 44篇 |
2002年 | 33篇 |
2001年 | 32篇 |
2000年 | 23篇 |
1999年 | 36篇 |
1998年 | 66篇 |
1997年 | 34篇 |
1996年 | 35篇 |
1995年 | 27篇 |
1994年 | 22篇 |
1993年 | 13篇 |
1992年 | 17篇 |
1991年 | 11篇 |
1990年 | 8篇 |
1989年 | 7篇 |
1988年 | 8篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 4篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 3篇 |
排序方式: 共有1549条查询结果,搜索用时 0 毫秒
41.
This work deals with the numerical localization of small electromagnetic inhomogeneities. The underlying inverse problem considers, in a three-dimensional bounded domain, the time-harmonic Maxwell equations formulated in electric field. Typically, the domain contains a finite number of unknown inhomogeneities of small volume and the inverse problem attempts to localize these inhomogeneities from a finite number of boundary measurements. Our localization approach is based on a recent framework that uses an asymptotic expansion for the perturbations in the tangential boundary trace of the curl of the electric field. We present three numerical localization procedures resulting from the combination of this asymptotic expansion with each of the following inversion algorithms: the Current Projection method, the MUltiple Signal Classification (MUSIC) algorithm, and an Inverse Fourier method. We perform a numerical study of the asymptotic expansion and compare the numerical results obtained from the three localization procedures in different settings. 相似文献
42.
关于环网G(N;S1,S2)的直径 总被引:6,自引:0,他引:6
本文首先给出了环网G(N;s_1,s_2)存在有限直径的充要条件;用初等数论方法给出了其直径的简明计算公式;最后讨论了类似文献[3]的环网直径的对偶性问题. 相似文献
43.
44.
45.
46.
47.
For sonochemical processing on an industrial scale the traditional choice is either a batch or flow system. The former is straightforward in concept but it requires large scale powerful ultrasonic transducers capable of delivering high intensity ultrasound to large volumes of liquid. Unfortunately at the moment the cost and problems involved in building very large sonication devices for batch processes cannot justify the replacement of existing industrial processes. For this reason most sonochemists prefer some form of flow system where small quantities of reagents can be treated as they are pumped from a large vat of reagents through a smaller sonochemical reactor where high intensity ultrasound can be applied. In this short paper we draw attention to a problem which seems common in a number of papers dealing with such flow systems – a confusion between the terms continuous reactor and loop reactor. Further we emphasise the importance of calculating the actual amount of ultrasonic processing experienced by the reaction mixture within the sonication zone of a loop reactor during its operation. The parameters required for such a calculation are: ultrasonic processor volume (Rv in L), pump flow rate (Fr in L/min), stock solution volume in the reservoir (Sv in L) and the overall system operating time (So in min). 相似文献
48.
Chen-Huan Wu 《Physics letters. A》2019,383(6):550-557
We theoretically investigate the current–current correlation of the two-dimensional (2D) parabolic Dirac system in hexogonal lattice. The analytical expressions of the random phase approximation (RPA) susceptibility, Ruderman–Kittel–Kasuya–Yosida (RKKY) Hamiltonian, and the diamagnetic orbital susceptibility in noninteracting case base on the density–density or current–current correlation function are derived and quantitatively analyzed. In noninteracting case, the dynamical polarization within RPA, and spin transverse susceptibility as well as the RKKY interaction (when close to the half-filling) are related to the current–current response in the 2D parabolic Dirac systems. Both the cases of anisotropic dispersion and isotropic dispersion are discussed. 相似文献
49.
本文简述了用数值方法研究Bitter型环向场线圈中电流分布情况,给出了不同时刻线圈中电流分布的形式以及线圈电感、电阻随时间的变化,也对电磁力的分布作了分析。 相似文献
50.
本文利用低混杂波电流驱动的准线性理论模型,研究了由于磁场的随机涨落而引起的快电子的反常输运对驱动电流分布和驱动效率的影响。结果表明,高能电子径向扩散将使驱动电流分布变平和展宽,同时驱动电流减小。 相似文献