全文获取类型
收费全文 | 288篇 |
免费 | 122篇 |
国内免费 | 17篇 |
专业分类
化学 | 50篇 |
晶体学 | 6篇 |
力学 | 59篇 |
综合类 | 8篇 |
数学 | 8篇 |
物理学 | 296篇 |
出版年
2024年 | 1篇 |
2023年 | 2篇 |
2022年 | 19篇 |
2021年 | 12篇 |
2020年 | 15篇 |
2019年 | 13篇 |
2018年 | 8篇 |
2017年 | 14篇 |
2016年 | 18篇 |
2015年 | 14篇 |
2014年 | 37篇 |
2013年 | 29篇 |
2012年 | 39篇 |
2011年 | 28篇 |
2010年 | 20篇 |
2009年 | 16篇 |
2008年 | 14篇 |
2007年 | 9篇 |
2006年 | 15篇 |
2005年 | 23篇 |
2004年 | 7篇 |
2003年 | 9篇 |
2002年 | 10篇 |
2001年 | 16篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 4篇 |
1993年 | 2篇 |
1992年 | 2篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
排序方式: 共有427条查询结果,搜索用时 15 毫秒
1.
Yu. Satov B. Sharkov H. Haseroth Yu. Smakovski K. Makarov S. Kondrashev V. Roerich A. Stepanov H. Kugler R. Scrivens O. Camut A. Shumshurov A. Balabaev A. Charushin 《Journal of Russian Laser Research》2004,25(3):205-216
Experimental and numerical calculation results devoted to development of an optical system for an ion source based on a repetition rate CO2 laser are described. The laser chain consists of a master oscillator, gas absorber cells, and a four-pass amplifier. The optical system provides smooth laser pulses with variable duration and high spatial quality that ensures efficiency for plasma heating and ion generation. The parameters of the plasma ion component measured in the CERN laboratory are applied for a lead target illumination. 相似文献
2.
3.
By using a passive Q-switch with GaAs saturable absorber, the Q-switched self-frequency doubling NYAB laser at 0.531μm has been successfully realized. The pulse width and the single pulse energy are measured. The numerical solutions of the coupling wave rate equations are in agreement with the experimental results. 相似文献
4.
The intensity dynamics of the double-clad Yb fibre laser have been characterised. Stabilisation of the fibre laser intensity by using uniform bi-directional pumping is demonstrated. For the single-end-pumped Yb fibre laser, the output becomes more stable for the shorter fibre length due to the higher threshold of stimulated Brillouin scattering, SBS, and Kerr effects and the reduction of saturated absorber effects caused by any unpumped fibre section. By additional pumping in a double-end-pumped configuration, the output power can be scaled higher before detecting high intensity pulses initiated by SBS in the Yb fibre laser due to the reduction of saturable absorption effect. It is confirmed that uniform pumping enhances the stability of the laser output. 相似文献
5.
A diode-end-pumped Nd:YAG laser is passively Q-switched by using Cr4+:YAG as saturable absorber. When CW pumped with a laser diode which the maximum power is 550 mW, the laser produces pulses of 24 ns duration at 1064 nm, with an energy of 26 μJ. 相似文献
6.
Yuanpeng Liang Bin Xiang Chao Liu Xiangdong Zhou Dan Wang Shan Song Genghua Bai Qi An Quehong Huang Shujun Chen Xuefeng Wei 《Tetrahedron》2014
Novel fluorine-containing ultraviolet absorbers (FBPs) with low surface energy were successfully synthesized based on 2,4-dihydroxy benzophenone (BP-1), and their structures were characterized by 1H NMR, 13C NMR, FTIR, and HRMS. UV absorption of FBPs was studied in 10−4 M dichloromethane (CH2Cl2), which demonstrated the superior UV absorption capability of FBPs (ca. ?=1.7×104 to 2.2×104 at λmax) over the matrix (?=1.7×104 at λmax). Quantum chemistry calculation was performed to investigate the stable structure and UV electronic absorption bands of FBPs. The surface chemistry information of high-chlorinated polyethylene (HCPE) coating films embedded with ultraviolet absorbers (UVAs) was given by X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The results show that the surface enrichment capability of FBPs is remarkably better than traditional UVAs (including BP-1, BP-3, BP-12) because of the low surface energy properties of FBPs. 相似文献
7.
Searching new light‐absorbing materials to replace toxic lead halide in solar cells is very important and highly desirable. In this research, we firstly demonstrated that tellurium iodide (TeI4) could be used as a light‐absorbing material in solar cells due to its suitable optical band gap and the active lone‐pair electron orbital in Te4+. The best power conversion efficiency (PCE=3.56%) was achieved with a concentration of 0.9 M TeI4 in DMF:DMSO (4 : 1, v,v) without any heat treatment or antisolvent dripping. Our study indicates the promising potential of TeI4 for photovoltaic and optoelectronic applications. 相似文献
8.
Manoel Raimundo dos Santos Junior Elinia Castro Costa Caio Campos Ferreira Lucas Pinto Bernar Marcilene Paiva da Silva Andria de Andrade Mncio Marcelo Costa Santos Sílvio Alex Pereira da Mota Douglas Alberto Rocha de Castro Sergio Duvoisin Junior Luiz Eduardo Pizarro Borges Marilena Emmi Araújo Nlio Teixeira Machado 《Molecules (Basel, Switzerland)》2022,27(7)
In this work, the deoxygenation of organic liquid products (OLP) obtained through the thermal catalytic cracking of palm oil at 450 °C, 1.0 atmosphere, with 10% (wt.) Na2CO3 as a catalyst, in multistage countercurrent absorber columns using supercritical carbon dioxide (SC-CO2) as a solvent, with an Aspen-HYSYS process simulator, was systematically investigated. In a previous study, the thermodynamic data basis and EOS modeling necessary to simulate the deoxygenation of OLP was presented. This work addresses a new flowsheet, consisting of 03 absorber columns, 10 expansions valves, 10 flash drums, 08 heat exchanges, 01 pressure pump, and 02 make-ups of CO2, aiming to improve the deacidification of OLP. The simulation was performed at 333 K, 140 bar, and (S/F) = 17; 350 K, 140 bar, and (S/F) = 38; 333 K, 140 bar, and (S/F) = 25. The simulation shows that 81.49% of OLP could be recovered and that the concentrations of hydrocarbons in the extracts of absorber-01 and absorber-02 were 96.95 and 92.78% (wt.) on a solvent-free basis, while the bottom stream of absorber-03 was enriched in oxygenated compounds with concentrations of up to 32.66% (wt.) on a solvent-free basis, showing that the organic liquid products (OLP) were deacidified and SC-CO2 was able to deacidify the OLP and obtain fractions with lower olefin contents. The best deacidifying condition was obtained at 333 K, 140 bar, and (S/F) = 17. 相似文献
10.
《Current Applied Physics》2020,20(2):331-336
We numerically and experimentally investigate single-band and dual-band isotropic metamaterial absorbers (IMAs) based on metallic disks. By optimizing the diameter of the metallic disks and the thickness of the dielectric substrate, the single-band IMA is observed at 16.2 GHz with absorptivity of 97%. When adding one disk-pair to the structure, the dual-band IMA is obtained at 12.8 and 15.5 GHz due to the symmetry breaking. The physical mechanics is explained by near-field coupling effect and equivalent LC circuit model. The measurement results performed in the range 12–18 GHz show a good agreement with simulation and theoretical analysis. Our findings demonstrate a new approach to achieve dual-band and multi-band IMAs. 相似文献