全文获取类型
收费全文 | 3089篇 |
免费 | 562篇 |
国内免费 | 363篇 |
专业分类
化学 | 2300篇 |
晶体学 | 37篇 |
力学 | 209篇 |
综合类 | 10篇 |
数学 | 297篇 |
物理学 | 1161篇 |
出版年
2024年 | 7篇 |
2023年 | 72篇 |
2022年 | 119篇 |
2021年 | 117篇 |
2020年 | 153篇 |
2019年 | 135篇 |
2018年 | 123篇 |
2017年 | 114篇 |
2016年 | 182篇 |
2015年 | 159篇 |
2014年 | 168篇 |
2013年 | 217篇 |
2012年 | 330篇 |
2011年 | 363篇 |
2010年 | 217篇 |
2009年 | 164篇 |
2008年 | 178篇 |
2007年 | 188篇 |
2006年 | 162篇 |
2005年 | 123篇 |
2004年 | 95篇 |
2003年 | 86篇 |
2002年 | 57篇 |
2001年 | 42篇 |
2000年 | 42篇 |
1999年 | 40篇 |
1998年 | 41篇 |
1997年 | 50篇 |
1996年 | 47篇 |
1995年 | 23篇 |
1994年 | 25篇 |
1993年 | 34篇 |
1992年 | 26篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 13篇 |
1988年 | 12篇 |
1987年 | 6篇 |
1986年 | 17篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
1957年 | 2篇 |
排序方式: 共有4014条查询结果,搜索用时 15 毫秒
111.
112.
113.
114.
115.
Yuming Yang Hua Lai Haitao Xu Chunyan Tao Hua Yang 《Journal of nanoparticle research》2010,12(1):217-225
In order to investigate the correlations of morphologies and optical properties, different morphologies of Eu-doped ZnO were
synthesized by different methods. Specifically, the structure of SiO2/ZnO:Eu nanoflower was synthesized for the first time and has not been reported previously. One percent was chosen as the
Eu doping concentration. The relations of the morphology, diameter, and uniformity with the PL intensity were examined. The
PL intensity of ZOE samples has a close relationship with the morphology. The PL intensity order of the different morphologies
of ZnO:Eu is as follows: nanorod arrays > thin film > nanospheres > nanoparticles > nanoflowers > nanorods. The PL intensity
of nanomaterials is larger, if the diameter of the nanomaterials is larger. However, the size of diameter is not the most
important reason. It was found that the sample uniformity plays a key role on ZnO:Eu PL intensity. ZnO:Eu with small particle
diameters may have strong photoluminescence intensity, if the nanoparticles are uniform. 相似文献
116.
117.
118.
119.
Yaming Niu Xiaoliang Zhu Lingzhi Liu Yan Zhao Zhenhua Jiang 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1459-1467
The new monomer (4‐(4′‐trifluoromethyl)phenoxyphenyl)hydroquinone (TFPOPH) was synthesized in a three‐step synthesis. A series of poly(aryl ether ketone) copolymers were prepared by the reaction of (4‐(4′‐Trifluoromethyl)phenoxyphenyl)hydroquinone and hydroquinone (HQ) with 4,4′‐difluorobenzophenone (DFB) in the presence of potassium carbonate in tretramethylene sulfone (TMS). Thermal analyses of the fluorinated copolymers showed that the glass transition temperature and 5.0% weight loss temperature are similar with that of PEEK, and the crystallinity decreased with increasing of TFPOPH. For the copolymer synthesized with the molar fraction of TFPOPH in the diphenol monomers (TFPOPH, HQ) being over 0.2, no cold crystallization temperature and melting temperature were detected, indicating that these copolymers are almost amorphous. The crystal structure of the copolymers with the molar fraction of TFPOPH being not higher than 0.2 is rhombic. The solubility in polar aprotic solvents of poly(aryl ether ketone)s copolymers increases and dielectric constant decreases step by step. 相似文献
120.
Langang Niu Ramaswamy Nagarajan Dingsong Feng Lynne A. Samuelson 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(12):1983-1990
Main‐chain thermotropic liquid‐crystalline polyesters containing rigid biphenyl mesogens and flexible spacers were synthesized by chemo‐enzymatic route. The enzyme‐catalyzed polymerization showed high regio‐ and chemo‐ selectivity, and is environmentally friendly. The resulting polyesters were characterized with 1H‐NMR, 13C‐NMR, gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and polarized light optical microscopy (POM). 相似文献