全文获取类型
收费全文 | 642篇 |
免费 | 54篇 |
国内免费 | 17篇 |
专业分类
化学 | 118篇 |
晶体学 | 1篇 |
力学 | 12篇 |
数学 | 6篇 |
物理学 | 576篇 |
出版年
2024年 | 4篇 |
2023年 | 9篇 |
2022年 | 8篇 |
2021年 | 5篇 |
2020年 | 4篇 |
2019年 | 7篇 |
2018年 | 3篇 |
2017年 | 15篇 |
2016年 | 17篇 |
2015年 | 13篇 |
2014年 | 40篇 |
2013年 | 17篇 |
2012年 | 30篇 |
2011年 | 43篇 |
2010年 | 37篇 |
2009年 | 70篇 |
2008年 | 50篇 |
2007年 | 67篇 |
2006年 | 46篇 |
2005年 | 25篇 |
2004年 | 23篇 |
2003年 | 29篇 |
2002年 | 21篇 |
2001年 | 21篇 |
2000年 | 12篇 |
1999年 | 7篇 |
1998年 | 19篇 |
1997年 | 3篇 |
1996年 | 10篇 |
1995年 | 12篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 7篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 4篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1976年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有713条查询结果,搜索用时 31 毫秒
71.
V. E. Peet 《Applied physics. B, Lasers and optics》1996,62(4):415-420
Selective excitation of laser-induced breakdown in krypton in the pressure range 1–4 bar and the spectral range 420–620 nm at a laser intensity of 1011 W/cm2 has been studied. It is shown that the breakdown of krypton can be induced selectively due to resonantly enhanced multiphoton ionization via excited atomic states. A number of four- and five-photon atomic resonances have been identified in breakdown excitation spectra. The role of different factors determining the selectivity of the breakdown has been studied. Possible analytical applications of a selective breakdown are discussed. 相似文献
72.
Y. Kimura 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):175-184
In a magnetic field, Cs2 molecules were excited from the ground X1Σ+g(vX=0,JX=55) level to the D 1Σ+u(v=46,J=54) level by dissociation laser light linearly polarized parallel to the field, for which the magnetic sublevels were
degenerated and thus all the transitions between them were simultaneously stimulated. Probe laser light excited the dissociated
Cs 6p2P3/2 atomic fragments to 6p2D3/2 level and the resultant 6p2P1/2 - 6d2D3/2 emission was detected as the function of the wavelength of the probe light. The populations of the 6p2P3/2,mj magnetic sublevels were determined from the relative strengths of the
6p2P3/2,mj - 6d2D3/2,m'j
transitions induced by the probe light. Non-zero orientation O0 was found in the ensemble of dissociated Cs
6p2P3/2
atomic fragments. The orientation O0 increased as the magnetic field strength increased. It was demonstrated both experimentally and theoretically that the orientation
O0 was induced through the interference in the excitation and dissociation paths in the presence of an external magnetic field,
even when all degenerated transitions between the magnetic sublevels of the molecules are simultaneously excited by the light
linearly polarized parallel to the field. 相似文献
73.
74.
Measurement of diameter of metal cylinders using a sinusoidally vibrating interference pattern 总被引:1,自引:0,他引:1
A method for measuring external diameters of metal cylinders is proposed in which a sinusoidally vibrating interference pattern (SVIP) of 100-μm period is used as an exact scale. Lights from the end-points of a metal cylinder are extracted with a spatial filtering in an imaging system to form a cross-sectional image of the metal cylinder. On the image a sinusoidally phase-modulated signal owing to the SVIP is detected with a CCD image sensor to measure the phases of the SVIP at the two end-points of the cylinder. The coordinates of the two end-points are obtained from the phases at the two end-points, the phase distribution of the SVIP, and the coordinates of the pixels of the CCD image sensor. Metal cylinder diameters of 7.99, 8.00, and 9.00 mm are measured along their length directions with an error less than 1 μm. 相似文献
75.
光纤白光干涉法与膜厚纳米测量新技术研究 总被引:6,自引:3,他引:3
运用薄膜光学干涉原理、光纤技术和干涉光谱分析技术,用光纤反射式干涉光谱仪(Reflectromic Interference Spectroscopy)直接测试宽带入射光在单晶硅表面超薄SiO2膜层前后界面反射形成的干涉光谱曲线,并用专业软件对被测光谱信号数据处理后,可直接用公式准确计算出SiO2氧化膜的厚度和光学折射率通过对单晶硅片表面超薄SiO2氧化膜的实测,并与成熟的椭圆偏振仪测试结果相比,测试误差≤2nm但该方法测试简单、快速,精度高,不需要制定仪器曲线和数表,可对薄膜任意位置的厚度在线测试经过对不同厚度聚苯乙烯薄膜的厚度测试表明,该方法适合0.5~20μm薄膜厚度的精确在线测量,测量误差小于7nm. 相似文献
76.
Interference of transverse rings in multifilamentation of powerful femtosecond laser pulses in air 总被引:3,自引:0,他引:3
S. L. Chin S. Petit W. Liu A. Iwasaki M. -C. Nadeau V. P. Kandidov O. G. Kosareva K. Yu. Andrianov 《Optics Communications》2002,210(3-6):329-341
We observe multiple filaments and interference of their ring structures in the propagation of 14 mJ, 45 fs infrared laser pulse in air. We suggest a simple physical model describing the formation and the interference of rings as the result of superposition of the background field of the whole beam and the fields that diverge from the filaments due to the defocusing in the laser-produced plasma. The size and the number of maxima in the interference pattern depend on the position of the filament formation along the direction of propagation. The simulated picture of the ring structure interference is in qualitative agreement with the one obtained from the experiment. 相似文献
77.
78.
转动传能中的量子干涉--干涉角和转动量子数的关系 总被引:9,自引:9,他引:0
沙国河等人在CO(A1∏(v=0)~e3∑-(v=1))体系与He,Ne和Ar碰撞诱导转动传能中首次观测到了量子干涉效应,并测量了干涉度。从理论上进一步研究原子-双原子分子体系碰撞诱导转动传能中量子干涉效应与转动量子数以及能量间隔的关系是十分必要的。我们考虑长程相互作用势,应用一级玻恩近似和直线轨迹近似,分别计算了CO(A1∏(v=0)~e3∑-(v=1))体系和He,Ne,Ar碰撞诱导转动传能中不同转动量子数以及不同能量间隔下的干涉角,得到了干涉角随转动量子数和能量间隔的变化趋势。这些结果对设计、分析这种类型的实验有一定的指导意义。 相似文献
79.
Third order nonlinear optical susceptibility (χ〈3〉) of metallophthalocyanines (MPcs, where M = Co, Cu, Zn, Mg) thin films and solutions was investigated by standard backward degenerate four wave mixing (DFWM) method at 532 nm. Third harmonic generation (THG) measurement at 1064 nm performed on MPcs thin films is also discussed. MPcs thin films were grown by conventional thermal evaporation in high vacuum and solution were dissolved in tetrahydrofuran (THF), in which the studied materials are soluble. In the case of microscopic nonlinearity, we calculated the second order hyperpolarizability (γ) for MPcs solutions. We found that the χ〈3〉 and the γ values are affected by the nature of the central metal atom. We also found that the value is larger than that measured via THG experiment. The variation in χ〈3〉 values occurs due to the different resonance contributions. 相似文献
80.
本文研究了一端弹性支撑的并列双柱和串列双圆柱在气流中自由端的振幅响应,与单圆柱相比,在小间距时,串列双圆柱中前柱的横向振幅受到较强的激励。而在大间距时,振幅受到抑制,特别当L/D=3.5和4.0时,其振幅响应仅为单柱的1/3左右,而对于后柱,则在大间距时,纵向振幅响应有所增大,而且后柱的振幅响应要比前柱的大得多,而并列双圆柱的自由端振幅基本上受到抑制,在T/D>3.0之后,干扰很快减小到接近单个圆 相似文献