全文获取类型
收费全文 | 5327篇 |
免费 | 532篇 |
国内免费 | 425篇 |
专业分类
化学 | 666篇 |
晶体学 | 32篇 |
力学 | 2012篇 |
综合类 | 84篇 |
数学 | 1704篇 |
物理学 | 1786篇 |
出版年
2024年 | 11篇 |
2023年 | 55篇 |
2022年 | 86篇 |
2021年 | 80篇 |
2020年 | 149篇 |
2019年 | 115篇 |
2018年 | 160篇 |
2017年 | 166篇 |
2016年 | 201篇 |
2015年 | 181篇 |
2014年 | 243篇 |
2013年 | 468篇 |
2012年 | 200篇 |
2011年 | 266篇 |
2010年 | 184篇 |
2009年 | 229篇 |
2008年 | 264篇 |
2007年 | 328篇 |
2006年 | 312篇 |
2005年 | 256篇 |
2004年 | 265篇 |
2003年 | 232篇 |
2002年 | 229篇 |
2001年 | 193篇 |
2000年 | 196篇 |
1999年 | 192篇 |
1998年 | 166篇 |
1997年 | 126篇 |
1996年 | 108篇 |
1995年 | 101篇 |
1994年 | 95篇 |
1993年 | 65篇 |
1992年 | 66篇 |
1991年 | 75篇 |
1990年 | 36篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 23篇 |
1986年 | 19篇 |
1985年 | 20篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 6篇 |
1957年 | 3篇 |
排序方式: 共有6284条查询结果,搜索用时 9 毫秒
31.
Yu. Gangrsky 《Hyperfine Interactions》2006,171(1-3):203-208
This review summarizes the experimental data on charge radii differences among ground state and high spin isomeric states
determined by high-resolution laser spectroscopic methods. A comparison is presented between radii changes obtained from the
isomeric shifts in the atomic spectra and from the quadrupole moments of both ground and isomeric states under the assumption
that the radii changes are determined by the difference of the quadrupole deformations. Special attention is paid to isomers
arising from the break-up of nucleon pairs and isomers of odd–odd nuclei. The characteristic features of the radii changes
for isomeric states of different origin are discussed. 相似文献
32.
Min Zhang Aanying Ma Lu Bai Lewei Li Zhensen Wu 《International Journal of Infrared and Millimeter Waves》2005,26(5):701-713
We present an effective numerical technique to characterize the scattering of wide-slot antennas fed by waveguides with arbitrary terminations in terms of the method of moment (MoM) and the mixed potential integral equation (MPIE). In particular, the precorrected-fast Fourier transform (P-FFT) eliminates the need to generate and store the usual square impedance matrix andthus leads to speed up the matrix-vector multiplication in the resultant system. This property makes the Rao-Wilton-Glisson (RWG) functions to be useful in simulating electrically large-scale problems. In addition, the scattering from the finite ground surfaces is accounted for in the total scattered field by using the method of equivalent edge currents. The numerical results are presented and compared with both the traditional method of moment results obtained using the entire-domain basis functions and the experimental results, to demonstrate the proposed method to be a good candidate for study on the scattering of arbitrary wide-slot large array. 相似文献
33.
We continue our study of the exponential law for occurrences and returns of patterns in the context of Gibbsian random fields.
For the low-temperature plus-phase of the Ising model, we prove exponential laws with error bounds for occurrence, return,
waiting and matching times. Moreover we obtain a Poisson law for the number of occurrences of large cylindrical events and
a Gumbel law for the maximal overlap between two independent copies. As a by-product, we derive precise fluctuation results
for the logarithm of waiting and return times. The main technical tool we use, in order to control mixing, is disagreement
percolation 相似文献
34.
A random two-dimensional large scale nano-network of silver nanowires(Ag-NWs) is fabricated by MeV hydrogen(H~+) ion beam irradiation. Ag-NWs are irradiated under H~+ion beam at different ion fluences at room temperature. The Ag-NW network is fabricated by H~+ion beam-induced welding of Ag-NWs at intersecting positions. H~+ion beam induced welding is confirmed by transmission electron microscopy(TEM) and scanning electron microscopy(SEM). Moreover, the structure of Ag NWs remains stable under H~+ion beam, and networks are optically transparent. Morphology also remains stable under H~+ion beam irradiation. No slicings or cuttings of Ag-NWs are observed under MeV H~+ion beam irradiation.The results exhibit that the formation of Ag-NW network proceeds through three steps: ion beam induced thermal spikes lead to the local heating of Ag-NWs, the formation of simple junctions on small scale, and the formation of a large scale network. This observation is useful for using Ag-NWs based devices in upper space where protons are abandoned in an energy range from MeV to GeV. This high-quality Ag-NW network can also be used as a transparent electrode for optoelectronics devices. 相似文献
35.
为更精确地描述真实人体呼吸道内的空气流动,明晰颗粒的运动沉积规律,本文从直接医学CT扫描得到的原始数据出发,利用图像辨识技术,重构了一个男性真人气管支气管树前三级的三维几何模型.采用大涡模拟的方法计算了非规则几何曲面结构内的气体流动现象,并在拉格朗日框架下跟踪颗粒的运动规律.数值计算得到了气流场的三维分布,以及颗粒的运动轨迹情况,结果表明现有基于Weibel的对称模型与真实人体的几何结构有较大的差异,而几何结构对流动影响较大;受非对称复杂结构影响,在不同截面的二次气流速度的分布规律不同;分叉后颗粒进入左右支气管的数量有明显的不同. 相似文献
36.
LIU Yu-Xiao WANG Yong-Qiang DUAN Yi-Shi 《理论物理通讯》2007,48(4):675-679
We study fermionic zero modes in the self-dual vortex background on an extra two-dimensional Riemann surface in (5+1) dimensions. Using the generalized Abelian-Higgs model, we obtain the inner topological structure of the self-dual vortex and establish the exact self-duality equation with topological term. Then we analyze the Dirac operator on an extra torus and the effective Lagrangian of four-dimensional fermions with the self-dual vortex background. Solving the Dirac equation, the fermionic zero modes on a torus with the self-dual vortex background in two simple cases are obtained. 相似文献
37.
38.
Yang Zhao Yue‐Jiao Zhang Jin‐Hui Meng Shu Chen Rajapandiyan Panneerselvam Chao‐Yu Li Sain Bux Jamali Xia Li Zhi‐Lin Yang Jian‐Feng Li Zhong‐Qun Tian 《Journal of Raman spectroscopy : JRS》2016,47(6):662-667
Silver nanoparticles (Ag NPs) enjoy a reputation as an ultrasensitive substrate for surface‐enhanced Raman spectroscopy (SERS). However, large‐scale synthesis of Ag NPs in a controlled manner is a challenging task for a long period of time. Here, we reported a simple seed‐mediated method to synthesize Ag NPs with controllable sizes from 50 to 300 nm, which were characterized by scanning electron microscopy (SEM) and UV–Vis spectroscopy. SERS spectra of Rhodamine 6G (R6G) from the as‐prepared Ag NPs substrates indicate that the enhancement capability of Ag NPs varies with different excitation wavelengths. The Ag NPs with average sizes of ~150, ~175, and ~225 nm show the highest SERS activities for 532, 633, and 785‐nm excitation, respectively. Significantly, 150‐nm Ag NPs exhibit an enhancement factor exceeding 108 for pyridine (Py) molecules in electrochemical SERS (EC‐SERS) measurements. Furthermore, finite‐difference time‐domain (FDTD) calculation is employed to explain the size‐dependent SERS activity. Finally, the potential of the as‐prepared SERS substrates is demonstrated with the detection of malachite green. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
39.
The chaotic classical single-particle motion in an oblate octupole deformed potential with a non-zero z-component of angular momentum Lz is investigated. The stability analysis of the trajectories shows that with increasing rotation of the system, the unstable negative curvature regions of the effective potential surface decrease, which converts the chaotic motion of the system into a regular one. 相似文献
40.
The chaotic classical single-particle motion in an oblate octupole deformed potential with a nonzero z-component of angular momentum Lz is investigated. The stability analysis of the trajectories shows that with increasing rotation of the system, the unstable negative curvature regions of the effective potential surface decrease, which converts the chaotic motion of the system into a regular one. 相似文献