全文获取类型
收费全文 | 381篇 |
免费 | 70篇 |
国内免费 | 81篇 |
学科分类
数理化 | 532篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 10篇 |
2018年 | 9篇 |
2017年 | 23篇 |
2016年 | 18篇 |
2015年 | 21篇 |
2014年 | 31篇 |
2013年 | 45篇 |
2012年 | 29篇 |
2011年 | 52篇 |
2010年 | 44篇 |
2009年 | 34篇 |
2008年 | 27篇 |
2007年 | 32篇 |
2006年 | 21篇 |
2005年 | 31篇 |
2004年 | 16篇 |
2003年 | 6篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1992年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
排序方式: 共有532条查询结果,搜索用时 250 毫秒
1.
以高纯ZnS粉末为基质,采用高温转相、扩散,以及表面涂敷工艺,制得了147Pm激发的ZnS:Cu,Cl发光粉。分析了ZnS:Cu,Cl的晶体结构,测量了ZnS:Cu,Cl的激发光谱、发射光谱、发光亮度。其晶体结构主要是六方纤锌矿型结构,激发光谱峰值波长为341nm,发射光谱峰值波长为513nm,初始发光亮度达到312mcd/m2。由激发光谱的峰值波长341nm推算得到六方ZnS晶体的禁带宽度为3.64eV。分析了147Pm激发的ZnS:Cu,Cl发光粉的发光寿命,其发光寿命达到5年以上。还探讨了该放射性发光粉的发光机理。147Pm激发的ZnS:Cu,Cl的稳定发光,实际上是激发过程与复合过程的准平衡。ZnS:Cu,Cl的绿色发光来源于深施主-深受主对的复合发射。实验结果的分析表明,ZnS:Cu,Cl中深施主-深受主之间的能级间隔约为2.42eV。 相似文献
2.
3.
We reported controllable synthesis of ZnS nanocrystal-polymer transparent hybrids by using polymethylmethacrylate (PMMA) as
a polymer matrix. In a typical run, the appropriate amounts of zinc chloride (ZnCl2) and sodium sulfide (Na2S) in the presence of 2-mercaptoethanol (ME) as the organic ligand were well dispersed in H2O/dimethylformamide solution without any aggregation. In addition, the Mn-doped ZnS nanocrystals (NCs) were synthesized with
similar method. Then, ZnS-PMMA hybrids were obtained via free radical polymerization in situ by using ZnS NCs functionalized
with methacryloxypropyltrimethoxysilane (MPS). FT-IR characterization indicates the formation of robust bonding between ZnS
NCs and the organic ligand. The TEM images show that ZnS NCs are well dispersed in PMMA matrix, and particle size of as-prepared
ZnS NCs is about 2.6 nm, in agreement with the computing results of Brus’s model and Debye–Scherrer formula. The photoluminescence
measurements present that ZnS NCs, Mn-doped ZnS NCs, and ZnS/PMMA hybrid show good optical properties. 相似文献
4.
A series of lightly La-doped CdO thin films (1%, 5%, and 7%) have been prepared by a spin coater sol-gel technique on amorphous
glass and crystalline Si substrates. Those prepared films were studied by X-ray diffraction (XRD), UV-VIS-NIR absorption spectroscopy,
and dc-electrical measurements. The investigation shows that La doping grows slightly the CdO lattice parameter and decreases
the intrinsic energygap from 2.1 eV to 1.7 eV. The optical properties were easily explained in the framework of classical
Drude theory and thus all the corresponding parameters were determined. The electrical behaviour of the samples shows that
they are degenerate semiconductors until the atomic percentage of the La dopant was 7% then the sample was converted into
a non-degenerate semiconductor. Generally, it was observed that the conductivity and mobility of the carriers were decreased
by increasing the La content in the CdO film samples. 相似文献
5.
Arrayed structures are desirable for many applications, but the fabrication of many material arrays remains a significant challenge. As a prominent II-VI semiconductor, large-scale arrayed ZnS structure has not been easily fabricated. Here, we introduce a simple structure conversion route for the synthesis of novel arrayed structures, and large-scale tube-like ZnS structure arrays and cable-like ZnS-ZnO composite arrays were successfully prepared through sulfuration conversion from arrayed rod-like ZnO structure based on a hydrothermal method at low temperature. XRD, EDS, SEM, TEM and PL are used to confirm the formation of the novel arrayed structure and trace the conversion process. The results show that the conversion ratio can be conveniently tailored by the reaction time, and the PL properties of the obtained materials can be adjusted through the conversion ratio. Especially, the cable-like structure holds the PL properties of both ZnO and ZnS structures. This simple solution method can be further extended to the preparation of other semiconductor sulfide and selenide, and can amplify the application field of large-scale arrays of semiconductors. 相似文献
6.
7.
利用静电纺丝法与气固反应相结合, 成功地制备了硫化锌掺锰/聚乙烯醇复合纳米纤维, 并对所制备的复合物进行了表征, 探讨了复合物的结构及其性能. 相似文献
8.
Ordered ZnS semiconductor nanoparticles were in situ synthesized in metal halide perovskite organic/inorganic layered hybrids (CnH2n 1NH3)2ZnCl4 (n=10 and 12) by reaction of their spin-casting films with H2S gas. Transmission electron microscopy, UV-vis spectroscopy and small-angle X-ray diffraction were used to characterize the morphology and the structure of formed nanoparticles. Obtained results indicate an effective way to incorporate functional inorganic nanoparticles into structured organic matrices. 相似文献
9.
Application of L-Cysteine-Capped ZnS Nanoparticles in the Determination of Nucleic Acids Using the Resonance Light Scattering Method 总被引:2,自引:0,他引:2
Yongxin?LiEmail author Jinlong?Chen Shujuan?Zhuo Yuqin?Wu Changqin?Zhu Lun?Wang 《Mikrochimica acta》2004,146(1):13-19
Nanometer-sized L-cysteine-capped ZnS particles were synthesized by a colloidal aqueous method. The functionalized nanoparticles are water-soluble and suitable for biological applications. In Tris-HCl buffer solution, nucleic acids combine with cysteine-capped nano-ZnS particles by intermolecular forces to form larger nanoparticles. There are two resonance light scattering peaks at 304.5nm and 373.8nm, respectively. The enhanced RLS is related to the concentration of nucleic acids in the range of 0.04 to 1.2µgmL–1 for calf thymus DNA and 0.2 to 1.0µgmL–1 for fish sperm DNA. The detection limits (3) are 19ngmL–1 for calf thymus DNA and 23ngmL–1 for fish sperm DNA, respectively. Four synthetic samples were analyzed satisfactorily. 相似文献
10.
Preparation and characterization of high-specific-surface-area activated carbons from K2CO3-treated waste polyurethane 总被引:2,自引:0,他引:2
Hayashi J Yamamoto N Horikawa T Muroyama K Gomes VG 《Journal of colloid and interface science》2005,290(2):437-443
An activated carbon with high specific surface area was prepared from polyurethane foam by chemical activation with K2CO3 and the influences of carbonization temperature and impregnation ratio on the pore structure of the prepared activated carbon were investigated. It was found that the specific surface area of the activated carbon was at a maximum value (about 2800 m(2)/g) at a carbonization temperature of 1073 K and at an impregnation ratio of 1.0. It was concluded that the polyurethane foam structure was modified during impregnation by K2CO3, K2CO3 promoted charring during carbonization, and then the weight loss behavior was changed below 700 and above 1000 K, carbon in the char was consumed by K2CO3 reduction, and this led to the high specific surface area. The prepared activated carbon had a very sharp micropore size distribution, compared with the commercial activated carbon having high specific surface area. The amounts of three organic vapors (benzene, acetone, and octane) adsorbed on the prepared activated carbons was much larger than those on the traditional coconut shell AC and the same as those on the commercial activated carbon except for octane. We surmised that the high specific surface area was due to the modification of the carbonization behavior of polyurethane foam by K2CO3. 相似文献