全文获取类型
收费全文 | 43514篇 |
免费 | 6322篇 |
国内免费 | 4909篇 |
专业分类
化学 | 31469篇 |
晶体学 | 516篇 |
力学 | 2495篇 |
综合类 | 297篇 |
数学 | 5187篇 |
物理学 | 14781篇 |
出版年
2024年 | 86篇 |
2023年 | 756篇 |
2022年 | 1132篇 |
2021年 | 1310篇 |
2020年 | 1495篇 |
2019年 | 1476篇 |
2018年 | 1291篇 |
2017年 | 1215篇 |
2016年 | 1912篇 |
2015年 | 1828篇 |
2014年 | 2214篇 |
2013年 | 2969篇 |
2012年 | 3651篇 |
2011年 | 3863篇 |
2010年 | 2699篇 |
2009年 | 2610篇 |
2008年 | 2938篇 |
2007年 | 2658篇 |
2006年 | 2398篇 |
2005年 | 2120篇 |
2004年 | 1615篇 |
2003年 | 1313篇 |
2002年 | 1282篇 |
2001年 | 1076篇 |
2000年 | 911篇 |
1999年 | 891篇 |
1998年 | 764篇 |
1997年 | 673篇 |
1996年 | 740篇 |
1995年 | 643篇 |
1994年 | 554篇 |
1993年 | 483篇 |
1992年 | 469篇 |
1991年 | 420篇 |
1990年 | 351篇 |
1989年 | 287篇 |
1988年 | 251篇 |
1987年 | 196篇 |
1986年 | 191篇 |
1985年 | 193篇 |
1984年 | 130篇 |
1983年 | 89篇 |
1982年 | 83篇 |
1981年 | 69篇 |
1980年 | 61篇 |
1979年 | 58篇 |
1978年 | 42篇 |
1976年 | 37篇 |
1974年 | 40篇 |
1973年 | 45篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
71.
72.
73.
74.
75.
76.
The crystal structure, magnetic and magnetotransport properties of the variation of B′-site transition metal in Sr2FeMO6 (M=Mo, W) with double perovskites structure have been investigated systematically. Measurements of magnetization vs. temperature at H=5 T show that Sr2FeMoO6 is a ferromagnet and Sr2FeWO6 is an antiferromagnet with TN∼35 K. Additionally, the large magnetoresistance ratio (MR) of ∼22% (H=3 T) at room temperature (RT) was observed in the Sr2FeWO6 compound. However, the Sr2FeMoO6 compound did not show any significant MR even at high fields and RT (MR∼1%; H=3 T and 300 K). The implications of these findings are supported by band structure calculations to explain the interaction between the 4d(Mo) and 5d(W) orbitals of transition metal ions and oxygen ions. 相似文献
77.
Yang Mujie Zhao Jian Li Aibing Shen Zhiquan Zhang Mingjian Lin Senhao 《Journal of polymer science. Part A, Polymer chemistry》1989,27(11):3829-3835
This paper reports that 60Co γ-ray irradiation can convert cis-polyphenylacetylene (cis-PPA) films prepared with rare-earth coordination catalysts to highly photosensitive materials. The dependence of the photosensitivity on irradiation dose, preparation methods, and microstructure of the PPA films has been investigated by means of a potential discharge technique. The photosensitivity was enhanced with increasing irradiation dose. The critical dose to produce a light response was 5 × 103 Gy. The maximum surface potential discharge rate was 618 V/s, and the dark decay was approximately 2 V/s for cis-PPA films irradiated with 60Co γ-ray (dose: 2 × 105 Gy). The cis-transoidal-PPA and an electrophotographic photoreceptor device incorporating cis-PPA showed a higher irradiation effect. The structure and properties of 60Co γ-ray irradiated rare-earth PPA films are similar to the unirradiated films. 相似文献
78.
Weidong Gao Meiqiong Zhan Shuhai Fan Janda Shao Zheng-Xiu Fan 《Applied Surface Science》2005,250(1-4):195-202
The laser-induced damage (LID) behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064 nm under single-pulse mode and free-running mode. The absorption measurement of such coatings was performed with surface thermal lensing (STL) technique. The damage morphologies under the two different laser modes were also studied in detail. It was found that all the filters exhibited a pass-band-center-dependent absorption and laser-induced damage threshold (LIDT) behavior, but the damage morphologies were diverse. The explanation was given with the analysis of the electric field distribution and the operational behavior of the irradiation laser. 相似文献
79.
Hong-Wen Gao 《Journal of Analytical Chemistry》2003,58(4):328-332
The reactions between Cu(II) and picramine CA (PCA) and Al(III) and PCA were both sensitive at pH 7. The competition coordination between Cu and the Al–PCA complex was applied to the selective determination of Cu (CCSD) by the spectral correction technique. Results have shown that the complexes formed at pH 7 are Al2(PCA) and Cu(PCA)3, their cumulative stability constants are 4.43 × 105 and 2.08 × 1015, respectively, and their real molar absorptivities are 5.78 × 103 at 650 nm and 3.19 × 104at 530 nm. At the analysis of the samples, the relative standard deviation (RSD) was 5.0% and the recovery rate of Cu was between 94 and 108%. 相似文献
80.
Deposition of Hydrogen-Free Silicon Nitride Thin Films by Microwave ECR plasma Enhanced Magnetron Sputtering at Room Temperature
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hydrogen-free silicon nitride (SiNx) films were deposited at room temperature by microwave electron cyclotron resonance (MW-ECR) plasma enhanced unbalance magnetron sputtering system. Both Fourier-transform infrared spectroscopy and x-ray photoelectron spectroscopy are used to study the bonding type and the change of bonding structures of the silicon nitride films. The results indicate that the chemical structure and composition of SiNx films deposited by this technique depend strongly on the N2 flow rates, the stoichiometric SiNx film, which has the highest hardness of 22.9 GPa, could be obtained at lower N2 flow rate of 4 sccm. 相似文献