全文获取类型
收费全文 | 6091篇 |
免费 | 1019篇 |
国内免费 | 578篇 |
专业分类
化学 | 2983篇 |
晶体学 | 41篇 |
力学 | 289篇 |
综合类 | 55篇 |
数学 | 498篇 |
物理学 | 1733篇 |
无线电 | 2089篇 |
出版年
2024年 | 32篇 |
2023年 | 163篇 |
2022年 | 217篇 |
2021年 | 291篇 |
2020年 | 273篇 |
2019年 | 247篇 |
2018年 | 232篇 |
2017年 | 193篇 |
2016年 | 271篇 |
2015年 | 307篇 |
2014年 | 367篇 |
2013年 | 456篇 |
2012年 | 515篇 |
2011年 | 458篇 |
2010年 | 372篇 |
2009年 | 339篇 |
2008年 | 358篇 |
2007年 | 331篇 |
2006年 | 300篇 |
2005年 | 281篇 |
2004年 | 179篇 |
2003年 | 192篇 |
2002年 | 151篇 |
2001年 | 143篇 |
2000年 | 130篇 |
1999年 | 160篇 |
1998年 | 112篇 |
1997年 | 122篇 |
1996年 | 97篇 |
1995年 | 94篇 |
1994年 | 70篇 |
1993年 | 57篇 |
1992年 | 44篇 |
1991年 | 41篇 |
1990年 | 30篇 |
1989年 | 16篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1957年 | 3篇 |
排序方式: 共有7688条查询结果,搜索用时 15 毫秒
71.
Hailin LiuZhihong Lu ling YueJing Liu Zhanghua GanChang Shu Ting ZhangJing Shi Rui Xiong 《Applied Surface Science》2011,257(22):9355-9361
A series of Ti1−xMoxO2−yNy samples were prepared by using sol-gel method and characterized by X-ray diffraction, transmission electron microscopy and UV-vis absorption spectroscopy. All Ti1−xMoxO2−yNy samples are anatase phase. It is found that Mo, N mono-doping can increase visible light absorption, while (Mo + N) co-doping can greatly enhance absorption in whole visible region. Results of our first-principles band structure calculations reveal that (Mo + N)-doping, especially passivated co-doping can increase the up-limit of dopant concentration and create more impurity bands in the band gap of TiO2, which leads to a greatly increase of its visible-light absorption without a decrease of its redox potential. It reveals that (Mo + N) co-doped TiO2 is promising for a photocatalyst with high photocalystic activity under visible light. 相似文献
72.
73.
Huadong Yuan Prof. Jianwei Nai Dr. Yongjin Fang Gongxun Lu Prof. Xinyong Tao Prof. Xiong Wen Lou 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(37):15973-15977
The growth of Li dendrites hinders the practical application of lithium metal anodes (LMAs). In this work, a hollow nanostructure, based on hierarchical MoS2 coated hollow carbon particles preloaded with sulfur (C@MoS2/S), was designed to modify the LMA. The C@MoS2 hollow nanostructures serve as a good scaffold for repeated Li plating/stripping. More importantly, the encapsulated sulfur could gradually release lithium polysulfides during the Li plating/stripping, acting as an effective additive to promote the formation of a mosaic solid electrolyte interphase layer embedded with crystalline hybrid lithium-based components. These two factors together effectively suppress the growth of Li dendrites. The as-modified LMA shows a high Coulombic efficiency of 98 % over 500 cycles at the current density of 1 mA cm−2. When matched with a LiFePO4 cathode, the assembled full cell displays a highly improved cycle life of 300 cycles, implying the feasibility of the proposed LMA. 相似文献
74.
Chen Zhao Zifeng Chen Wei Wang Peixun Xiong Benfang Li Mengjie Li Dr. Jixing Yang Prof. Yunhua Xu 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(29):12090-12096
Organic cathode materials have attracted extensive attention because of their diverse structures, facile synthesis, and environmental friendliness. However, they often suffer from insufficient cycling stability caused by the dissolution problem, poor rate performance, and low voltages. An in situ electropolymerization method was developed to stabilize and enhance organic cathodes for lithium batteries. 4,4′,4′′-Tris(carbazol-9-yl)-triphenylamine (TCTA) was employed because carbazole groups can be polymerized under an electric field and they may serve as high-voltage redox-active centers. The electropolymerized TCTA electrodes demonstrated excellent electrochemical performance with a high discharge voltage of 3.95 V, ultrafast rate capability of 20 A g−1, and a long cycle life of 5000 cycles. Our findings provide a new strategy to address the dissolution issue and they explore the molecular design of organic electrode materials for use in rechargeable batteries. 相似文献
75.
76.
Zhang Yaohui Li Tianbin Feng Wenkai Xiong Zuqiang Zhang Guoqiang 《Journal of Thermal Analysis and Calorimetry》2020,139(1):47-56
Journal of Thermal Analysis and Calorimetry - In order to find out the rules of the effect of temperature on performances and hydration process of sulphoaluminate cement-based dual liquid grouting... 相似文献
77.
A practical and efficient synthesis of phosphatidylinositol pentam annoside (PIM5) was achieved based on a five-component one-pot sequential glycosylation protocol with exclusive regio- and stereo-selectivity. 相似文献
78.
利用现代教育技术优化高等数学教学 总被引:3,自引:0,他引:3
本根据《高等数学》的课程特点,结合现代教育技术的发展以及高等数学课程的教学现状,提出在教学中利用现代教育技术手段优化高等数学课程的教学,以达到现代教育培养综合素质高、应用能力强的复合型人才的总目标。 相似文献
79.
We report a systematic study of the spin polarization of epitaxial CrO2 films at and across an interface using planar junctions with a superconducting counterelectrode. By chemical modification of the CrO2 surface before the deposition of the superconductor, junctions with a wide range of barrier strength were obtained. Analysis of the conductance data on these junctions, especially under Zeeman splitting of the superconducting density of states, yields consistent, close to full spin polarization for CrO2 regardless of the barrier strength. 相似文献
80.
Jigang Yin Yin Hang Lianhan Zhang Jing Xiong Pengchao Hu 《Journal of luminescence》2010,130(8):1338-1342
The electronic structures of LiYF4 (YLF) crystals containing F color center (YLF-F) and Yb doped YLF crystals (Yb3+:YLF, Yb2+:YLF) are systematically studied within the framework of the density functional theory. The calculated results indicate that the 330 nm absorption band originates from the F center in YLF crystals. Thus the doping of Yb3+ can weaken the 330 nm absorption band by competing with F vacancies in capturing free electrons arising after γ-irradiation and change to Yb2. By analyzing the lattice relaxation and the electronic structure of YLF containing Yb2+, we can reasonably believe that once Yb2+ is formed in YLF crystal, its compensating hole will turn out to be shared by two F− nearest to Yb2+ forming a diatomic fluoride molecular ion () perturbed by Yb2+, or to say VF color center. According to the molecular-orbital linear combination of atomic orbital (MO-LCAOs) theory, compared to the alkali halides, e.g. LiF, the in VF center in LiYF4 peaks at about 340 nm, which is in agreement with the experimental results. 相似文献