全文获取类型
收费全文 | 81905篇 |
免费 | 12315篇 |
国内免费 | 8174篇 |
专业分类
化学 | 55549篇 |
晶体学 | 803篇 |
力学 | 5615篇 |
综合类 | 575篇 |
数学 | 10039篇 |
物理学 | 29813篇 |
出版年
2024年 | 169篇 |
2023年 | 1606篇 |
2022年 | 2013篇 |
2021年 | 2619篇 |
2020年 | 2992篇 |
2019年 | 2826篇 |
2018年 | 2576篇 |
2017年 | 2293篇 |
2016年 | 3592篇 |
2015年 | 3564篇 |
2014年 | 4277篇 |
2013年 | 5672篇 |
2012年 | 7043篇 |
2011年 | 7251篇 |
2010年 | 4942篇 |
2009年 | 4813篇 |
2008年 | 5116篇 |
2007年 | 4593篇 |
2006年 | 4303篇 |
2005年 | 3737篇 |
2004年 | 2938篇 |
2003年 | 2264篇 |
2002年 | 2065篇 |
2001年 | 1828篇 |
2000年 | 1701篇 |
1999年 | 1844篇 |
1998年 | 1572篇 |
1997年 | 1385篇 |
1996年 | 1476篇 |
1995年 | 1320篇 |
1994年 | 1168篇 |
1993年 | 1001篇 |
1992年 | 904篇 |
1991年 | 801篇 |
1990年 | 670篇 |
1989年 | 578篇 |
1988年 | 444篇 |
1987年 | 412篇 |
1986年 | 342篇 |
1985年 | 338篇 |
1984年 | 230篇 |
1983年 | 200篇 |
1982年 | 156篇 |
1981年 | 126篇 |
1980年 | 89篇 |
1978年 | 58篇 |
1977年 | 52篇 |
1976年 | 50篇 |
1975年 | 57篇 |
1973年 | 57篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
171.
172.
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
173.
Compact, time‐harmonic, acoustic sources produce waves that decay too slowly to be square‐integrable on a line away from the sources. We introduce an inner product, arising directly from Green's second theorem, to form a Hilbert space of these waves and present examples of its computation.1 © 2005 Wiley Periodicals, Inc. 相似文献
174.
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
175.
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
176.
TANG Chen ZHANG Fang YAN Hai-Qing CHEN Zhan-Qing LUO Tao 《理论物理通讯》2005,44(3):435-439
We develop the three-step explicit and implicit schemes of exponential fitting methods. We use the three- step explicit exponential fitting scheme to predict an approximation, then use the three-step implicit exponential fitting scheme to correct this prediction. This combination is called the three-step predictor-corrector of exponential fitting method. The three-step predictor-corrector of exponential fitting method is applied to numerically compute the coupled nonlinear Schroedinger equation and the nonlinear Schroedinger equation with varying coefficients. The numerical results show that the scheme is highly accurate. 相似文献
177.
Junhua Chen 《Journal of organometallic chemistry》2006,691(3):470-474
Four novel hexadentate imidazolium salts were synthesized from hexakis(bromomethyl)benzene and 1-substituted imidazole. The arylation of aldehydes with arylboronic acids was effected conveniently and in high yields by a catalyst system generated in situ from these hexadentate imidazolium salts, [Rh(COD)Cl]2 and a base. 相似文献
178.
179.
180.
Chen Xiaoyang 《中国科学G辑(英文版)》2004,47(Z1)
The occurrence of time-dependent cavitation and tensile stress in an oscillatory oil squeeze film were investigated experimentally. The test apparatus was a simple thrust bearing consisting of two parallel circular plates separated by a thin viscous oil film. During the test, one plate was at rest while the other (transparent) oscillated in a direction normal to its surface. This test configuration was chosen to avoid the rotational motion and complicated geometry of a squeeze film journal bearing. The frequency of oscillation was in the range of 5 to 50 Hz and was controlled by an electro-magnetic exciter. The process of cavity formation and its subsequent development was recorded by a high-speed video camera. Concomitant pressure in the oil film was measured both within and without the cavitation region. It was found that both tensile stress and cavities existed in a squeeze film under certain working conditions. 相似文献