全文获取类型
收费全文 | 10027篇 |
免费 | 2556篇 |
国内免费 | 1098篇 |
专业分类
化学 | 2932篇 |
晶体学 | 178篇 |
力学 | 1664篇 |
综合类 | 91篇 |
数学 | 1132篇 |
物理学 | 7684篇 |
出版年
2024年 | 22篇 |
2023年 | 119篇 |
2022年 | 257篇 |
2021年 | 231篇 |
2020年 | 369篇 |
2019年 | 302篇 |
2018年 | 272篇 |
2017年 | 329篇 |
2016年 | 439篇 |
2015年 | 397篇 |
2014年 | 678篇 |
2013年 | 743篇 |
2012年 | 630篇 |
2011年 | 819篇 |
2010年 | 619篇 |
2009年 | 752篇 |
2008年 | 777篇 |
2007年 | 727篇 |
2006年 | 733篇 |
2005年 | 549篇 |
2004年 | 556篇 |
2003年 | 420篇 |
2002年 | 413篇 |
2001年 | 399篇 |
2000年 | 338篇 |
1999年 | 269篇 |
1998年 | 269篇 |
1997年 | 213篇 |
1996年 | 167篇 |
1995年 | 158篇 |
1994年 | 116篇 |
1993年 | 106篇 |
1992年 | 100篇 |
1991年 | 66篇 |
1990年 | 63篇 |
1989年 | 55篇 |
1988年 | 34篇 |
1987年 | 26篇 |
1986年 | 21篇 |
1985年 | 25篇 |
1984年 | 19篇 |
1983年 | 12篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 10篇 |
1979年 | 12篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Optical trapping forces of polystyrene microspheres are analyzed both theoretically and experimentally, and comparisons are
made between the two. Discrepancies are mainly caused by straight-ray approximation for axial trapping, and by trapping-position
vertical displacement due to gravity for transverse trapping. 相似文献
82.
Yu. D. Perfiliev V. S. Rusakov L. A. Kulikov A. A. Kamnev K. Alkhatib 《Hyperfine Interactions》2006,167(1-3):881-885
To explain line broadening in emission Mössbauer spectra as compared to the corresponding absorber measurements, the model of trapped electrons has been proposed. Auger electrons (emitted, e.g. after electron capture by 57Co or after the converted isomeric transition of 119mSn), as well as secondary electrons, may be trapped in the proximity to the nucleogenic ion. Electrons captured by lattice traps at different distances from the daughter ion induce an asymmetric distribution of quadrupole splitting in the resulting emission spectra, as shown in a few examples. This model is supported by estimates of quadrupole splitting values which may be caused by such trapped electrons located at specified distances from the nucleogenic atom. 相似文献
83.
Electron beam processing of poly(ethylene terephthalate) (PET) films is found to promote significant changes in the melting heat, intrinsic viscosity and polymer film-liquid (water, isooctane and toluene) boundary surface tension. These properties are featured with several maximums depending on the absorbed dose and correlating with the modification of PET surface functionality. Studies using adsorption of acid-base indicators and IR-spectroscopy revealed that the increase of PET surface hydrophilicity is determined by the oxidation of methylene and methyne groups. Electron beam treatment of PET films on the surface of N-vinylpyrrolidone aqueous solution provided graft copolymerization with this comonomer at optimum process parameters (energy 700 keV, current 1 mA, absorbed dose 50 kGy). 相似文献
84.
85.
混凝土动态劈裂拉伸试验的数值模拟 总被引:4,自引:0,他引:4
采用LS-DYNA有限元编码程序,对混凝土的动态劈裂拉伸试验进行了数值模拟,给出了混凝土试样在不同类型加载情况下应力分布之间的差异,证实了动态劈裂拉伸试验的有效性,提出了改进试验方法的若干结论. 相似文献
86.
A detailed study of the generalized M2 factor of hard-edged diffracted beams based on the truncated second-order moments method, asymptotic analysis and self-convergent beam width approach is performed. The dependence of the generalized M2 factor on the parameters characterizing the spatial profile, and beam truncation, etc. is analyzed. 相似文献
87.
A mathematical model of laser beam treatment of double layer alloys (Ni/Fe, Al/Fe and Cr/Fe systems) describing the effect of laser beam on different physical and geometrical parameters of coated layer system has been adapted. The numerical solutions of the non-homogeneous heat-transport differential equation could estimate the temperature of the treated region.The suggested model allows investigation of the temperature distribution as a function of treated surface and laser parameters. The physical parameters of the treated materials were taken as functions of temperature due to the change in the temperature of the treated double layer materials. 相似文献
88.
Based on the generalized Huygens–Fresnel diffraction integral and the expansion of the hard aperture function into a finite sum of complex Gaussian functions, the approximate analytical expression of elegant Laguerre–Gaussian beams passing through a paraxial ABCD optical system with an annular aperture is derived. Meanwhile, the corresponding closed-forms for the unapertured, circular apertured or circular black screen cases are also given. The obtained results provide more convenience for studying their propagation and transformation than the usual way by using diffraction integral formula directly. Some numerical examples are given to illustrate the propagation properties of elegant Laguerre–Gaussian beams. 相似文献
89.
Under the nonresonant case where the carrier frequency of a Gaussian beam deviates from the resonant frequency of a Fabry–Perot etalon, the transmission of a Gaussian beam after incidenting nonnormally on a Fabry–Perot etalon has been investigated. The results show that under the nonresonant case, variations of the peak intensity, the position of the peak intensity and the spot size of the transmitted beam with the input angle behave differently and even with a reversed tendency compared with those obtained under the resonant case. 相似文献
90.