全文获取类型
收费全文 | 2911篇 |
免费 | 676篇 |
国内免费 | 88篇 |
专业分类
化学 | 3048篇 |
晶体学 | 47篇 |
力学 | 6篇 |
综合类 | 2篇 |
数学 | 7篇 |
物理学 | 565篇 |
出版年
2023年 | 10篇 |
2022年 | 14篇 |
2021年 | 61篇 |
2020年 | 150篇 |
2019年 | 115篇 |
2018年 | 69篇 |
2017年 | 78篇 |
2016年 | 186篇 |
2015年 | 212篇 |
2014年 | 231篇 |
2013年 | 269篇 |
2012年 | 252篇 |
2011年 | 218篇 |
2010年 | 251篇 |
2009年 | 243篇 |
2008年 | 252篇 |
2007年 | 234篇 |
2006年 | 224篇 |
2005年 | 168篇 |
2004年 | 160篇 |
2003年 | 125篇 |
2002年 | 24篇 |
2001年 | 31篇 |
2000年 | 21篇 |
1999年 | 22篇 |
1998年 | 14篇 |
1997年 | 21篇 |
1996年 | 9篇 |
1995年 | 3篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有3675条查询结果,搜索用时 15 毫秒
81.
82.
83.
84.
85.
86.
This paper presents a study on polycrystalline diamond (PCD) polished by dynamic friction polishing (DFP) with the aid of advanced dual beam FIB (focused ion beam) microscopy. After disclosing a variety of wear tracks by DFP using electron imaging in combination with the ion channelling effect, a dual beam FIB was successfully employed at wear track sites to specifically create both the large cross-sectional specimen for microanalysis and thin foil for nanoanalysis. The study concluded that the polished PCD subsurface was free from microscale cracking. However, the attached debris layer on the top surface contained metal oxides and non-diamond carbon phase with inhomogeneous distributions of C, Fe, Cr, Ni, Si and O across the layer. An attached layer directly above a diamond grain was composed of essentially amorphous carbon, suggesting that a direct phase transformation from diamond crystalline to amorphous occurred during DFP. 相似文献
87.
Synthesis of Cationic Dumbbell-shaped Fullerene Nanostructures as Potential Photodynamic Sensitizers
A design of novel hydrophilic tetracationic dumbbell-shaped [60]fullerene nanostructures was made by balancing the hydrophilicity and hydrophobicity characteristics of the fullerene adduct for their potential application as photodynamic sensitizers in the PDT treatment. A sequential protection-deprotection reaction pathway was applied for the functional differentiation between primary and secondary amine moieties of pentaethylene hexamine. Synthesis of the target molecule involves two key steps of unsymmetrical esterification and amidation of malonic acid and subsequent fullerenation. The synthetic strategy was accomplished using mild reaction conditions in the intermediate molecule preparation and led a moderate overall product yield. 相似文献
88.
89.
90.
Wilson Merchan-Merchan Alexei V. Saveliev Walmy Cuello Jimenez 《Proceedings of the Combustion Institute》2011,33(2):1899-1908
In this paper we report the growth of 1-D and 3-D tungsten-oxide nanostructures on tungsten wire probes inserted in an opposed-flow oxy-fuel flame. The probe diameter and oxygen content in the oxidizer were varied to study their influence on the growth of tungsten-oxide nanostructures. The introduction of a 1-mm diameter W probe into the flame environment with an oxidizer composition of 50%O2 + 50%N2, resulted in the formation of 1-D nanorods on the upper surface of the probe. The formation of triangular, rectangular, square, and cylindrical 3-D channels with completely hollow or semi-hollow morphology was achieved by reducing the probe diameter to 0.5 mm. Whereas, the increase of the O2 content to 100% and the employment of a 1-mm probe resulted in the growth of ribbon-like micron-sized structures. The lattice spacing of ∼0.38 nm measured for the 1-D W-oxides closely matches a monoclinic WO3 structure. X-ray photoelectron spectroscopy analysis revealed that the larger 3-D structures also consist of WO3 confirming that the chemical composition of the structures remains the same while varying the probe and flame parameters. The proposed growth mechanism states that the 3-D WO3 structures are formed through the lateral coalescence of 1-D W-oxide nanorods. 相似文献