全文获取类型
收费全文 | 39660篇 |
免费 | 5661篇 |
国内免费 | 4056篇 |
专业分类
化学 | 28458篇 |
晶体学 | 393篇 |
力学 | 2389篇 |
综合类 | 326篇 |
数学 | 4553篇 |
物理学 | 13258篇 |
出版年
2024年 | 90篇 |
2023年 | 745篇 |
2022年 | 963篇 |
2021年 | 1200篇 |
2020年 | 1466篇 |
2019年 | 1445篇 |
2018年 | 1195篇 |
2017年 | 1096篇 |
2016年 | 1751篇 |
2015年 | 1697篇 |
2014年 | 2073篇 |
2013年 | 2736篇 |
2012年 | 3469篇 |
2011年 | 3600篇 |
2010年 | 2304篇 |
2009年 | 2323篇 |
2008年 | 2450篇 |
2007年 | 2294篇 |
2006年 | 2079篇 |
2005年 | 1755篇 |
2004年 | 1361篇 |
2003年 | 1205篇 |
2002年 | 1233篇 |
2001年 | 935篇 |
2000年 | 779篇 |
1999年 | 853篇 |
1998年 | 728篇 |
1997年 | 701篇 |
1996年 | 772篇 |
1995年 | 594篇 |
1994年 | 540篇 |
1993年 | 451篇 |
1992年 | 443篇 |
1991年 | 378篇 |
1990年 | 298篇 |
1989年 | 234篇 |
1988年 | 182篇 |
1987年 | 153篇 |
1986年 | 142篇 |
1985年 | 139篇 |
1984年 | 101篇 |
1983年 | 70篇 |
1982年 | 52篇 |
1981年 | 42篇 |
1980年 | 23篇 |
1978年 | 22篇 |
1977年 | 24篇 |
1976年 | 26篇 |
1975年 | 29篇 |
1974年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
勿庸置疑,课堂只是学生腾飞的基地,社会才是学生飞翔的天空.如何架设课堂与社会之间的桥梁,使学生从理论走向实践,从空想走向实际,是每位教师必须思考的问题.就物理教学而言,实验是架设课堂和社会的桥梁之一.那就是通过物理实验来实现. 相似文献
72.
A fluorous osmium catalyst was firstly developed. It had been effectively used as recoverable and reusable catalyst in the dihydroxylation of olefins. 相似文献
73.
Li Yingle Huang Jiying Gong Shuohong 《International Journal of Infrared and Millimeter Waves》2003,24(6):953-961
The dielectric constant for rain medium is investigated by utilizing the system identification method. The rain rate model and frequency model of permittivity in millimeter waves band for rain medium are presented. The results obtained with models are in very good agreement with references in calculating the attenuation of electromagnetic waves induced by rain, which Shows that the obtained models are valid and practicable. The cross-polar discrimination gotten with rain rate model is in agreement with references. 相似文献
74.
Zhang Xinliang Huang Dexiu Sun Junqiang Liu Deming 《Optical and Quantum Electronics》2004,36(7):627-634
A simple scheme for single to multi-channel wavelength conversion based on cross-gain modulation of amplified spontaneous emission (ASE) spectrum in semiconductor optical amplifier (SOA) is described. Single to 16-channel wavelength conversion at 10 Gb/s is first demonstrated without any additional probe lights, the modulation information carried by input signal could be converted into arbitrary many channels if only the demultiplexer with enough channels is exploited. Output performance and pattern effects are investigated experimentally. 相似文献
75.
Mid-infrared generation based on a periodically poled LiNbO3 optical parametric oscillator
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We report a nanosecond Nd:YVO_4-pumped optical parametric oscillator (OPO) based on periodically poled LiNbO_3 (PPLN). Tuning is achieved in this experiment by varying the temperature and period of the PPLN. The design of double-pass singly resonant oscillator (DSRO) and confocal cavity enables the OPO threshold to be lowered considerably, resulting in a simple, compact, all-solid-state configuration with the mid-infrared idler powers of up to 466mW at 3.41μm. 相似文献
76.
77.
J. Song H. Jiang Z.J. Liu D.Y. Khang Y. Huang J.A. Rogers C. Lu C.G. Koh 《International Journal of Solids and Structures》2008,45(10):3107-3121
A finite-deformation theory is developed to study the mechanics of thin buckled films on compliant substrates. Perturbation analysis is performed for this highly nonlinear system to obtain the analytical solution. The results agree well with experiments and finite element analysis in wavelength and amplitude. In particular, it is found that the wavelength depends on the strain. Based on the accurate wavelength and amplitude, the membrane and peak strains in thin films, and stretchability and compressibility of the system are also obtained analytically. 相似文献
78.
Current methodologies used for the inference of thin film stress through curvature measurement are strictly restricted to stress and curvature states that are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to a single layer of thin film deposited on a substrate subjected to the non-uniform misfit strain in the thin film. Such methodologies are further extended to multi-layer thin films deposited on a substrate in the present study. Each thin film may have its own non-uniform misfit strain. We derive relations between the stresses in each thin film and the change of system curvatures due to the deposition of each thin film. The interface shear stresses between the adjacent films and between the thin film and the substrate are also obtained from the system curvatures. This provides the basis for the experimental determination of thin film stresses in multi-layer thin films on a substrate. 相似文献
79.
Pengbo Jiang Tiexin Cheng Yan Liu Xianghao Cui Yingli Bi Kaiji Zhen 《Reaction Kinetics and Catalysis Letters》2004,82(1):49-56
The novel phase transfer catalysts S-8 [4-(dimethyloctylammonium) propansultan] and DB-X [1,4-bis(triethylmethylammonium)benzene dibromide] were synthesized and employed for high conversion synthesis of dichlorocyclopropane from various olefins.This revised version was published online in December 2005 with corrections to the Cover Date. 相似文献
80.
Ching Sum Hui Lillian Sze Man Lam Chun Yin Wai Kin Chan Aleksandra B. Djurii 《Journal of polymer science. Part A, Polymer chemistry》2003,41(11):1708-1715
Polyurethanes incorporated with rhenium diimine complexes were synthesized. The polymers exhibited interesting morphologies and solution properties. Results from gel permeation chromatography suggested the formation of polymer aggregates in solutions. The polymers could act as probes for metal ions. The addition of metal ions to polymer solutions led to significant changes in the electronic absorption properties of the polymer solutions. This was attributed to the interactions between the polyether moieties and metal ions. The metal complexes could also act as efficient photosensitizers. After doping with charge‐transport viologens, the photoconductivity of the polymers was greatly enhanced. The experimental quantum efficiency was simulated with Onsager's theory. The thermalization distances and the primary yields were typically 12–14 Å and 10?3, respectively. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1708–1715, 2003 相似文献