全文获取类型
收费全文 | 1085篇 |
免费 | 124篇 |
国内免费 | 122篇 |
专业分类
化学 | 735篇 |
晶体学 | 9篇 |
力学 | 95篇 |
综合类 | 3篇 |
数学 | 110篇 |
物理学 | 379篇 |
出版年
2024年 | 4篇 |
2023年 | 41篇 |
2022年 | 65篇 |
2021年 | 67篇 |
2020年 | 83篇 |
2019年 | 58篇 |
2018年 | 37篇 |
2017年 | 33篇 |
2016年 | 53篇 |
2015年 | 56篇 |
2014年 | 51篇 |
2013年 | 53篇 |
2012年 | 90篇 |
2011年 | 101篇 |
2010年 | 55篇 |
2009年 | 65篇 |
2008年 | 57篇 |
2007年 | 45篇 |
2006年 | 58篇 |
2005年 | 44篇 |
2004年 | 36篇 |
2003年 | 30篇 |
2002年 | 21篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 10篇 |
1997年 | 12篇 |
1996年 | 5篇 |
1995年 | 8篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 6篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1983年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有1331条查询结果,搜索用时 15 毫秒
21.
悬浮液进样—火焰原子吸收光谱法测定玉米中的锌和铁 总被引:14,自引:2,他引:14
本文提出了一种悬浮液进样-火焰原子吸收光谱法测定玉米面中锌,铁的新方法。将玉米面悬浮于琼脂胶体中,直接喷入空气-乙炔火焰中,用标准加入法测定,测定结果与灰化法一致。方法简便,快速。 相似文献
22.
Yan Yu Luan Li-Na Wang Lin-Cheng 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2022,76(8):1-7
The European Physical Journal D - Bent crystals are a compact and versatile tool to manipulate ultra-relativistic particle beams in accelerators. Indeed, the unrivaled steering power achievable... 相似文献
23.
Qingyong He Jiasu Wang Suyu Wang Jiansi Wang Hao Dong Yuxin Wang Senhao Shao 《Physica C: Superconductivity and its Applications》2009,469(2-3):91-94
The loading capacity of the high-temperature superconducting (HTS) Maglev vehicle is an important parameter in the practical application. It is closely related to the levitation force of the HTS bulk. Many papers reported that the levitation force showed the relaxation characteristic. Because different loads cause different levitation gaps and different applied magnetic fields, the levitation force relaxations under the different loads are not the same. In terms of cylindrical YBCO bulk levitated over the permanent magnetic guideway, the relationship between the levitation force relaxation and the reloading is investigated experimentally in this paper. The decrement, the decrement rate and the relaxation rate of the levitation force are calculated, respectively. This work might be helpful for studying the loading capacity of the HTS Maglev vehicle. 相似文献
24.
<正>Projective synchronization of a weighted complex network is studied in which nodes are spatiotemporal chaos systems and all nodes are coupled not with the nonlinear terms of the system but through a weighted connection.The range of the linear coefficient matrix of separated configuration,when the synchronization is implemented,is determined according to Lyapunov stability theory.It is found that projective synchronization can be realized for unidirectional star-connection even if the coupling strength between the nodes is a given arbitrary weight value.The Gray-Scott models having spatiotemporal chaos behaviours are taken as nodes in the weighted complex network,and simulation results of spatiotemporal synchronization show the effectiveness of the method. 相似文献
25.
<正>The statement for the third paragraph of the right column of page 3079 (Chinese Physics B, 2008, Vol. 17,No. 8, pp. 3077-3082 )[1]is inappropriate. This paragraph should be restated as follows. 相似文献
26.
利用泵浦-检测方法,在样品池条件下,研究了Cs(6D5/2)与H2反应碰撞传能过程。利用激光感应荧光(LIF)光谱技术,确定了CsH[X1Σ+(v,J)]振转能级上的布居分布,转动态分布与热统计分布基本一致.Cs激发态原子密度由激光能量吸收得到.记录A1Σ+(v',J+1)→X1Σ+(v,J)的时间分辨荧光,从荧光强度的对数值给出的直线斜率确定(v',J+1)→(v,J)的自然辐射率,结合(v,J)→(v',J+1)吸收系数的测量,得到反应生成物CsH[X1Σ+(v,J)]态的分子密度.由速率方程分析,给出反应截面(v,J),对J求和,得到(v)[10-16cm2单位]分别为(0.64±0.19)(v=0)和(0.58±0.17)(v=1). 相似文献
27.
Yuxin Leng Lihuang Lin Wenyao Wang Yunhua Jiang Bin Tang Zhizhan Xu 《Optics & Laser Technology》2003,35(6):425-429
A birefringent crystal quartz plate of known thickness has been used as a spectral filter for spectral shaping in a Ti:sapphire regenerative amplifier. The spectral profile of the amplified pulse ejected from the regenerative amplifier was observed while adjusting the birefringent crystal plate in the cavity. By altering the gain spectrum, the bandwidth of the regeneratively amplified pulse was increased from 18 to 35 nm by using a 0.34-mm thick birefringent plate. The output pulse spectrum from the regenerative amplifier neared the bandwidth of the seed pulse. As a comparison, we used a coated filter outside the regenerative amplifier cavity, and the bandwidth of the regeneratively amplified pulse was stretched to 28 nm. When the bandwidth was stretched to 35 nm, the pulse was compressed to 35 fs. 相似文献
28.
The photorefractive planar lens for converting a vertical incident plane wave to a lateral-spread spherical wave and vice versa, is suggested. Using the two-beam coupled-wave theory, the coupled wave equations are derived and their half-analytical solutions are also given in terms of an infinite series. The diffraction properties (beam profiles, diffraction efficiency) of the local volume grating in the lens are presented. And the focusing property of the lens is discussed and compared with that of an ideal convergent spherical wave. It is demonstrated that the suggested photorefractive planar lens shows a good focusing effect. 相似文献
29.
对描述双掺杂晶体非挥发性全息记录动力学过程的Kukhtarev方程进行了矢量分析,分析中考虑了体光生伏特效应和外加电场的作用。在小信号近似的基础上给出了双中心全息记录中记录与固定阶段空间电荷场的矢量解析解。在综合考虑空间电荷场的各向异性以及晶体有效电光系数的各向异性后,给出了双中心全息记录的优化记录方向。结果表明,对(Fe,Mn)∶LiNbO3晶体633nm寻常光记录,优化记录方向主要由有效电光系数决定,光栅波矢与光轴夹角为22°,方位角为30°;对(Fe,Mn)∶LiNbO3晶体633nm非寻常光记录,优化记录方向主要由固定空间电荷场决定,光栅波矢与光轴夹角为44°,方位角为90°。 相似文献
30.
Jiangfeng Luan 《Optik》2011,122(2):168-172
The temporal intensity distributions of the transmitted light through the tissue with lesion structures are investigated using the polarized Monte Carlo technique. Simulation results show that time-resolved curves of transmitted light change obviously for different lesion structures. When the lesion thickness increases, the intensity of transmitted light decreases for co-polarization detection and increases for cross-polarization detection. With the increase of the lesion depth, the amplitude rises for both co- and cross-polarization detection. A method considering the dependence of the peak temporal distribution on the lesion position is thus proposed to locate lesions inside live tissues. 相似文献