全文获取类型
收费全文 | 894篇 |
免费 | 181篇 |
国内免费 | 89篇 |
专业分类
化学 | 611篇 |
晶体学 | 40篇 |
力学 | 2篇 |
综合类 | 1篇 |
数学 | 1篇 |
物理学 | 509篇 |
出版年
2023年 | 10篇 |
2022年 | 25篇 |
2021年 | 36篇 |
2020年 | 66篇 |
2019年 | 29篇 |
2018年 | 41篇 |
2017年 | 28篇 |
2016年 | 55篇 |
2015年 | 49篇 |
2014年 | 56篇 |
2013年 | 88篇 |
2012年 | 61篇 |
2011年 | 70篇 |
2010年 | 40篇 |
2009年 | 61篇 |
2008年 | 64篇 |
2007年 | 76篇 |
2006年 | 68篇 |
2005年 | 35篇 |
2004年 | 20篇 |
2003年 | 69篇 |
2002年 | 27篇 |
2001年 | 52篇 |
2000年 | 11篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 7篇 |
1995年 | 1篇 |
1990年 | 1篇 |
排序方式: 共有1164条查询结果,搜索用时 0 毫秒
91.
Highly Luminescent Cesium Lead Halide Perovskite Nanocrystals with Tunable Composition and Thickness by Ultrasonication 下载免费PDF全文
Yu Tong Eva Bladt Meltem F. Aygüler Aurora Manzi Dr. Karolina Z. Milowska Verena A. Hintermayr Prof. Dr. Pablo Docampo Prof. Dr. Sara Bals Dr. Alexander S. Urban Dr. Lakshminarayana Polavarapu Prof. Dr. Jochen Feldmann 《Angewandte Chemie (International ed. in English)》2016,55(44):13887-13892
We describe the simple, scalable, single‐step, and polar‐solvent‐free synthesis of high‐quality colloidal CsPbX3 (X=Cl, Br, and I) perovskite nanocrystals (NCs) with tunable halide ion composition and thickness by direct ultrasonication of the corresponding precursor solutions in the presence of organic capping molecules. High angle annular dark field scanning transmission electron microscopy (HAADF‐STEM) revealed the cubic crystal structure and surface termination of the NCs with atomic resolution. The NCs exhibit high photoluminescence quantum yields, narrow emission line widths, and considerable air stability. Furthermore, we investigated the quantum size effects in CsPbBr3 and CsPbI3 nanoplatelets by tuning their thickness down to only three to six monolayers. The high quality of the prepared NCs (CsPbBr3) was confirmed by amplified spontaneous emission with low thresholds. The versatility of this synthesis approach was demonstrated by synthesizing different perovskite NCs. 相似文献
92.
Ying Liu Dr. Ximing Rong Mingze Li Prof. Maxim S. Molokeev Prof. Jing Zhao Prof. Zhiguo Xia 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(28):11731-11737
The incorporation of impurity ions or doping is a promising method for controlling the electronic and optical properties and the structural stability of halide perovskite nanocrystals (NCs). Herein, we establish relationships between rare-earth ions doping and intrinsic emission of lead-free double perovskite Cs2AgInCl6 NCs to impart and tune the optical performances in the visible light region. Tb3+ ions were incorporated into Cs2AgInCl6 NCs and occupied In3+ sites as verified by both crystallographic analyses and first-principles calculations. Trace amounts of Bi doping endowed the characteristic emission (5D4→7F6-3) of Tb3+ ions with a new excitation peak at 368 nm rather than the single characteristic excitation at 290 nm of Tb3+. By controlling Tb3+ ions concentration, the emission colors of Bi-doped Cs2Ag(In1−xTbx)Cl6 NCs could be continuously tuned from green to orange, through the efficient energy-transfer channel from self-trapped excitons to Tb3+ ions. Our study provides the salient features of the material design of lead-free perovskite NCs and to expand their luminescence applications. 相似文献
93.
This Concept article provides an elementary discussion of a special class of large‐sized gold compounds, so‐called Au nanoclusters, which lies in between traditional organogold compounds (e.g., few‐atom complexes, <1 nm) and face‐centered cubic (fcc) crystalline Au nanoparticles (typically >2 nm). The discussion is focused on the relationship between them, including the evolution from the Au???Au aurophilic interaction in AuI complexes to the direct Au? Au bond in clusters, and the structural transformation from the fcc structure in nanocrystals to non‐fcc structures in nanoclusters. Thiolate‐protected Aun(SR)m nanoclusters are used as a paradigm system. Research on such nanoclusters has achieved considerable advances in recent years and is expected to flourish in the near future, which will bring about exciting progress in both fundamental scientific research and technological applications of nanoclusters of gold and other metals. 相似文献
94.
A facile method to control the synthesis and self‐assembly of monodisperse Ag and Ag2S nanocrystals with a narrow‐size distribution is described. Uniform Ag nanoparticles of less than 4 nm were obtained by thermolysis of Ag–oleate complexes in the presence of oleic acid and dodecylamine, and monodisperse Ag nanoparticles of less than 10 nm were also prepared in one step by using dodecylamine and oleic acid as capping agents. Moreover, the surface‐enhanced Raman scattering (SERS) properties of the Ag substrates have also been investigated. It is worth mentioning that these Ag nanoparticles and assemblies show great differences in the SERS activities of Rhodamine B dye. In addition, the superlattices of Ag2S nanocrystals were synthesized with Ag–oleate complexes, alkanethiol, and sulfur as the reactants. The resulting highly monodisperse nanocrystals can easily self‐assemble into interesting superstructures in the solution phase without any additional assembly steps. This method may be extended to the size‐controlled preparation and assembly of many other noble‐metal and transition‐metal chalcogenide nanoparticles. These results will aid the study of the physicochemical properties of the superlattice assemblies and construction of functional macroscopic architectures or devices. 相似文献
95.
A drug nanocrystals self-stabilized Pickering emulsion (NSSPE) with a unique composition and microstructure has been proven to significantly increase the bioavailability of poorly soluble drugs. This study aimed to develop a new solid NSSPE of puerarin preserving the original microstructure of NSSPE by spray-drying. A series of water-soluble solid carriers were compared and then Box-Behnken design was used to optimize the parameters of spray-drying. The drug release and stability of the optimized solid NSSPE in vitro were also investigated. The results showed that hydroxypropyl-β-cyclodextrin (HP-β-CD), rather than solid carriers commonly used in solidification of traditional Pickering emulsions, was suitable for the solid NSSPE to retain the original appearance and size of emulsion droplets after reconstitution. The amount of HP-β-CD had more influences on the solid NSSPE than the feed rate and the inlet air temperature. Fluorescence microscopy, confocal laser scanning microscopy and scanning electron microscopy showed that the reconstituted emulsion of the solid NSSPE prepared with HP-β-CD had the same core-shell structure with a core of oil and a shell of puerarin nanocrystals as the liquid NSSPE. The particle size of puerarin nanocrystal sand interfacial adsorption rate also did not change significantly. The cumulative amount of released puerarin from the solid NSSPE had no significant difference compared with the liquid NSSPE, which were both significantly higher than that of puerarin crude material. The solid NSSPE was stable for 3 months under the accelerated condition of 75% relative humidity and 40 °C. Thus, it is possible todevelop the solid NSSPE preserving the unique microstructure and the superior properties in vitro of the liquid NSSPE for poorly soluble drugs. 相似文献
96.
本文研究了Mg2CoH5纳米晶的制备及其储氢性能。在室温和氩气气氛下,以MgH2和纳米Co为原料,采用球磨法制备了Mg2CoH5纳米晶。对所制备Mg2CoH5的组成、结构和形貌进行了表征,并且对Mg2CoH5的储氢性能进行了研究。实验结果表明,通过该种方法制备了纯度较高(产物纯度为79%)的四方结构Mg2CoH5纳米晶,其形貌呈球形且分布较均匀,最频粒径为80 nm。制备的Mg2CoH5纳米晶具有较低的活化能和较好的吸放氢动力学性能,其放氢的脱附焓和脱附熵分别为-115.0 kJ.mol-1H2和-193.6.1 J.mol-1.K-1H2。再氢化时,在543 K时仅7 min内其吸氢量就达到1.5wt%。 相似文献
97.
98.
Andrew Ritchhart Brandi M. Cossairt 《Angewandte Chemie (International ed. in English)》2018,57(7):1908-1912
We have synthesized InP nanocrystals of an unprecedented crystal phase at low temperature (35–100 °C) by templated growth of InP magic‐sized clusters. With the addition of stoichiometric equivalents of P(SiMe3)3 to the starting cluster, we demonstrate nanocrystal growth mediated through a partial dissolution and recrystallization pathway. This growth process was monitored using a combination of in situ UV/Vis and 31P NMR spectroscopy, revealing the intermediacy of smaller cluster species of higher symmetry. The nanocrystals that result from this templated growth exhibit a crystal structure that is neither zincblende nor wurtzite, and instead is derived from the original cluster. This structure is best described as a 3D polytwistane phase as deduced from a combination of X‐ray diffraction, Raman, and solid‐state NMR spectroscopy methods. 相似文献
99.
Anuj Kumar Yuvraj Singh Negi Veena Choudhary Nishi Kant Bhardwaj 《International Journal of Polymer Analysis and Characterization》2017,22(2):139-151
Cellulose nanocrystal-reinforced poly(vinyl alcohol)/silica glass hybrid scaffolds were fabricated using the freeze-drying method. In this study, we develop molecular-level-based hybrid scaffolds with possible bioactivity behavior by adding silica sol–gel. The results showed a highly porous structure and a significant improvement in mechanical performance (stiffness) of hybrid scaffolds with an increased content of cellulose nanocrystals followed by the addition of silica-based bioactive glass. In vitro cell study with MC3T3-E1 cells on hybrid scaffolds for 1 and 3 days revealed good cell adhesion and growth. Thus, the obtained hybrid scaffold may be a competitive candidate for bone tissue engineering applications. 相似文献
100.
GdF3∶Eu3+/NaGdF4∶Eu3+纳米晶的水热合成及发光性质 总被引:1,自引:0,他引:1
采用水热法,以聚乙二醇(400)为分散剂,以NaOH和HNO3溶液调节初始溶液pH值,合成GdF3∶Eu3+和NaGdF4∶Eu3+纳米晶。XRD和SEM结果表明:在酸性溶液(pH=3,5)、中性溶液(pH=7)和碱性溶液(pH=9)中,分别获得具有正交结构的GdF3∶Eu3+纳米晶,GdF3∶Eu3+和NaGdF4∶Eu3+混合晶,六方结构NaGdF4∶Eu3+棒状微米晶。根据Scherrer公式估算pH=3和pH=5时制备纳米晶的一次性粒径分别为49和28 nm。样品的发射光谱结果表明:特征发射峰来自于5D2、5D1、5D0到7FJ跃迁。在主晶相为GdF3样品中,主发射峰来自于Eu3+的5D0→7F1的磁偶极跃迁;晶相为NaGdF4样品的主发射峰来自于Eu3+的5D0→7F2电偶极跃迁。5D0→7F1和5D0→7F2跃迁发射相对强度比值显示:Eu3+在NaGdF4晶体中的格位对称性下降。激发光谱显示出Gd3+和Eu3+具有较好的能量传递。 相似文献