全文获取类型
收费全文 | 15119篇 |
免费 | 1924篇 |
国内免费 | 1957篇 |
专业分类
化学 | 12349篇 |
晶体学 | 287篇 |
力学 | 511篇 |
综合类 | 152篇 |
数学 | 1520篇 |
物理学 | 4181篇 |
出版年
2024年 | 22篇 |
2023年 | 167篇 |
2022年 | 312篇 |
2021年 | 456篇 |
2020年 | 487篇 |
2019年 | 550篇 |
2018年 | 408篇 |
2017年 | 468篇 |
2016年 | 652篇 |
2015年 | 711篇 |
2014年 | 918篇 |
2013年 | 1132篇 |
2012年 | 1383篇 |
2011年 | 1434篇 |
2010年 | 1059篇 |
2009年 | 988篇 |
2008年 | 1202篇 |
2007年 | 992篇 |
2006年 | 960篇 |
2005年 | 800篇 |
2004年 | 665篇 |
2003年 | 540篇 |
2002年 | 618篇 |
2001年 | 412篇 |
2000年 | 316篇 |
1999年 | 234篇 |
1998年 | 186篇 |
1997年 | 121篇 |
1996年 | 121篇 |
1995年 | 92篇 |
1994年 | 73篇 |
1993年 | 76篇 |
1992年 | 59篇 |
1991年 | 75篇 |
1990年 | 36篇 |
1989年 | 52篇 |
1988年 | 24篇 |
1987年 | 33篇 |
1986年 | 22篇 |
1985年 | 27篇 |
1984年 | 14篇 |
1983年 | 17篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 8篇 |
1978年 | 10篇 |
1977年 | 8篇 |
1976年 | 9篇 |
1973年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
72.
Flat-top interleavers with chromatic dispersion compensator based on phase dispersive free space Mach-Zehnder interferometer 总被引:2,自引:0,他引:2
In this paper, novel interleavers using circular cavities (CC) in a Mach-Zehnder interferometer (MZI) has been presented and demonstrated for the first time, in which CCs act as phase dispersive mirrors which exhibit a periodic dependence on the frequency of light. Three implementation schemes have been proposed and investigated. Theoretical analysis shows the spectral characteristics of each scheme in a 50-GHz channel spacing application. Furthermore, the chromatic dispersion (CD) of each output comb can be flattened within passband by appending an additional CC. The result shows that the proposed designs with novel interferometer technique can simultaneously provide flat top passbands, high isolation stopband and low CD value as well. 相似文献
73.
Kyung Hwa Hong Jong Lyoul Park In Hwan Sul Ji Ho Youk Tae Jin Kang 《Journal of Polymer Science.Polymer Physics》2006,44(17):2468-2474
Polyvinyl alcohol (PVA) nanofibers containing Ag nanoparticles were prepared by electrospinning PVA/silver nitrate (AgNO3) aqueous solutions, followed by short heat treatment, and their antimicrobial activity was investigated for wound dressing applications. Since PVA is a water soluble and biocompatible polymer, it is one of the best materials for the preparation of wound dressing nanofibers. After heat treatment at 155 °C for 3 min, the PVA/AgNO3 nanofibers became insoluble, while the Ag+ ions therein were reduced so as to produce a large number of Ag nanoparticles situated preferentially on their surface. The residual Ag+ ions were reduced by subsequent UV irradiation for 3 h. The average diameter of the Ag nanoparticles after the heat treatment was 5.9 nm and this value increased slightly to 6.3 nm after UV irradiation. It was found that most of the Ag+ ions were reduced by the simple heat treatment. The PVA nanofibers containing Ag nanoparticles showed very strong antimicrobial activity. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2468–2474, 2006 相似文献
74.
75.
Xie Ruixiang Wang Min Duan Changchun Yan Yihua R. A. Sych A. T. Altyntsev 《中国科学A辑(英文版)》2002,45(1):97-105
A complex solar radio moving type IV burst was observed on 23 September 1998 with the broadband (1.0–2.0 GHz and 2.6–3.8 GHz) spectrometers with high temporal and spectral resolutions at National Astronomical Observatories of China (NAOC). Comparing to the high spatial resolution data of Siberian Solar Radio Telescope (SSRT), we find that this burst is a rare type of moving type IV burst which is caused by the expanding arches, and the spatial structure oscillations of the radio sources are related with the time structure pulsations of the radio emission. Furthermore, the burst is associated with the multiple quasi-periodic long-term pulsations, and this suggests the existence of multi-scale magnetic structures in a large expanding coronal arch. We think the moving type IV burst is due to the synchrotron emission of the energetic electrons trapped in the expanding arch, and the multiple quasi-periodic pulsations are due to the second harmonic plasma emission. 相似文献
76.
Differential scanning calorimetry (DSC) and x-ray diffraction (XRD) are employed to investigate the effects of nickel on the crystallization of the amorphous Zr70Cu20Ni10 alloy. We have found that the crystallization process of the amorphous Zr70Cu20Ni10 alloy is strongly influenced by the addition of nickel. Addition of 10 at% Ni to the Zr70Cu30 amorphous alloy makes the crystallization process proceed from a single-stage mode to a double-stage mode. The activation energy for crystallization of the amorphous Zr70Cu20Ni10 alloy is calculated to be about 388kJ·mol-1 on the basis of the Kissinger equation. The effects of nickel on the crystallization of the amorphous Zr70Cu20Ni10 alloy are discussed in terms of the genetics of metals. 相似文献
77.
78.
We propose a new lens scheme to focus cold atoms by using a controllable inhomogeneous magnetic field from a square current-carrying wire fabricated on a chip. The spatial distributions of the magnetic field are calculated, and the results show that the generated magnetic field is a two-dimensional (2D) quadrupole one and can be used to focus cold atoms or a cold atomic beam. The dynamic processes of cold atoms passing through our square wire layout and its focusing properties are studied by using Monte Carlo simulations. Our study shows that the atomic clouds can be focused effectively by our magnetic lens scheme, and the focal length of the atomic lens and its radius of focused spot can be continuously changed by adjusting the current in the wires. 相似文献
79.
80.
利用现代教育理论,结合物理实验的教学实际,探讨和研究了探索性物理实验的双重教育功能.通过具体的探索性物理实验案例,验证了探索性物理实验具有激发学生的兴趣、发展学生的探索精神和唤起教师创造性的双重教育功能. 相似文献