全文获取类型
收费全文 | 673篇 |
免费 | 47篇 |
国内免费 | 60篇 |
专业分类
化学 | 388篇 |
晶体学 | 7篇 |
力学 | 62篇 |
综合类 | 11篇 |
数学 | 149篇 |
物理学 | 163篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 15篇 |
2021年 | 22篇 |
2020年 | 16篇 |
2019年 | 15篇 |
2018年 | 20篇 |
2017年 | 9篇 |
2016年 | 32篇 |
2015年 | 24篇 |
2014年 | 26篇 |
2013年 | 29篇 |
2012年 | 64篇 |
2011年 | 65篇 |
2010年 | 31篇 |
2009年 | 52篇 |
2008年 | 57篇 |
2007年 | 58篇 |
2006年 | 47篇 |
2005年 | 45篇 |
2004年 | 21篇 |
2003年 | 11篇 |
2002年 | 16篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 9篇 |
1998年 | 9篇 |
1997年 | 6篇 |
1996年 | 11篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 3篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 4篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有780条查询结果,搜索用时 0 毫秒
131.
Lattice distortion in AgPt nanoparticles was studied using X-ray diffraction and other techniques. These nanoparticles show high catalytic activity in the reduction of p-nitrophenol and had a turn over frequency of 5.4 × 10(2) s(-1). 相似文献
132.
133.
Liang Liang Peiquan Ling Yuhuan Li Li Li Jiandang Liu Qiquan Luo Hongjun Zhang Qian Xu Yang Pan Junfa Zhu Bangjiao Ye Yongfu Sun 《中国科学:化学(英文版)》2021,(6):953-958
To realize efficient atmospheric CO_2 chemisorption and activation,abundant Ti~(3+) sites and oxygen vacancies in TiO_2 ultrathin layers were designed.Positron annihilation lifetime spectroscopy and theoretical calculations first unveil each oxygen vacancy is associated with the formation of two Ti~(3+) sites,giving a Ti~(3+)-V_o-Ti~(3+)configuration.The Ti~(3+)-V_o-Ti~(3+) sites could bond with CO_2 molecules to form a stable configuration,which converted the endoergic chemisorption step to an exoergic process,verified by in-situ Fourier-transform infrared spectra and theoretical calculations.Also,the adjacent Ti~(3+) sites not only favor CO_2 activation into COOH*via forming a stable Ti~(3+)–C–O–Ti~(3+) configuration,but also facilitate the rate-limiting COOH~* scission to CO~* by reducing the energy barrier from 0.75 to 0.45 e V.Thus,the Ti~(3+)-V_o-TiO_2 ultrathinlayers could directly capture and photofix atmospheric CO_2 into near-unity CO,with the corresponding CO_2-to-CO conversion ratio of ca. 20.2%. 相似文献
134.
135.
136.
Man Zhang Zikun Li Mengqi Dai Hongjun He Bin Liang Chanchan Sun Xiulian Li Changjian Ji 《Molecules (Basel, Switzerland)》2022,27(20)
Chitosan (CS) and pea protein isolate (PPI) were used as raw materials to prepare nanoparticles. The structures and functional properties of the nanoparticles with three ratios (1:1, 1:2 1:3, CS:PPI) were evaluated. The particle sizes of chitosan–pea protein isolate (CS–PPI) nanoparticles with the ratios of 1:1, 1:2, and 1:3 were 802.95 ± 71.94, 807.10 ± 86.22, and 767.75 ± 110.10 nm, respectively, and there were no significant differences. Through the analysis of turbidity, endogenous fluorescence spectroscopy and Fourier transform infrared spectroscopy, the interaction between CS and PPI was mainly caused by electrostatic mutual attraction and hydrogen bonding. In terms of interface properties, the contact angles of nanoparticles with the ratio of 1:1, 1:2, and 1:3 were 119.2°, 112.3°, and 107.0°, respectively. The emulsifying activity (EAI) of the nanoparticles was related to the proportion of protein. The nanoparticle with the ratio of 1:1 had the highest potential and the best thermal stability. From the observation of their morphology by transmission electron microscopy, it could be seen that the nanoparticles with a ratio of 1:3 were the closest to spherical. This study provides a theoretical basis for the design of CS–PPI nanoparticles and their applications in promoting emulsion stabilization and the delivery of active substances using emulsions. 相似文献
137.
Continuous dependence on a modelling parameter are established for solutions to a problem for a complex Ginzburg–Landau equation. We establish continuous dependence on the coefficient of the cubic term, and also on the coefficient of the term multiplying the Laplacian. Copyright 2003 John Wiley & Sons, Ltd. 相似文献
138.
139.
Let D be a bounded positive (m, p)-circle domain in ?2. The authors prove that if dim(Iso(D)0) = 2, then D is holomorphically equivalent to a Reinhardt domain; if dim(Iso(D)0) = 4, then D is holomorphically equivalent to the unit ball in ?2. Moreover, the authors prove the Thullen’s classification on bounded Reinhardt domains in ?2 by the Lie group technique. 相似文献
140.
As an important mid-infrared to far-infrared optical window, ZnS is extremely important to improve spectral transmission performance, especially in the military field. However, on account of the Fresnel reflection at the interface between the air and the high-strength substrate, surface optical loss occurs in the ZnS optical window. In this study, the concave antireflective sub-wavelength structures (ASS) on ZnS have been experimentally investigated to obtain high transmittance in the far-infrared spectral range from 6 μm to 10 μm. We proposed a simple method to fabricate microhole array ASS by femtosecond Bessel beam, which further increased the depth of the microholes and suppressed the thermal effects effectively, including the crack and recast layer of the microhole. The influence of different Gaussian and Bessel beam parameters on the microhole morphology were explored, and three ASS structures with different periods were prepared by the optimized Bessel parameters. Ultimately, the average transmittance of the sample with the ASS microhole array period of 2.6 μm increased by 4.1% in the 6 μm to 10 μm waveband, and the transmittance was increased by 5.7% at wavelength of 7.2 μm. 相似文献