全文获取类型
收费全文 | 237篇 |
免费 | 8篇 |
国内免费 | 13篇 |
专业分类
化学 | 67篇 |
晶体学 | 6篇 |
力学 | 11篇 |
综合类 | 1篇 |
数学 | 10篇 |
物理学 | 113篇 |
综合类 | 50篇 |
出版年
2023年 | 1篇 |
2022年 | 5篇 |
2021年 | 2篇 |
2020年 | 3篇 |
2019年 | 7篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 8篇 |
2015年 | 3篇 |
2014年 | 9篇 |
2013年 | 16篇 |
2012年 | 13篇 |
2011年 | 42篇 |
2010年 | 18篇 |
2009年 | 20篇 |
2008年 | 15篇 |
2007年 | 14篇 |
2006年 | 18篇 |
2005年 | 5篇 |
2004年 | 3篇 |
2003年 | 3篇 |
2002年 | 5篇 |
2001年 | 5篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1986年 | 1篇 |
排序方式: 共有258条查询结果,搜索用时 15 毫秒
51.
Gerolf Ziegenhain Alexander Hartmaier Herbert M. Urbassek 《Journal of the mechanics and physics of solids》2009,57(9):1514-1526
Molecular-dynamics simulation can give atomistic information on the processes occurring in nanoindentation experiments. In particular, the nucleation of dislocation loops, their growth, interaction and motion can be studied. We investigate how realistic the interatomic potentials underlying the simulations have to be in order to describe these complex processes. Specifically we investigate nanoindentation into a Cu single crystal. We compare simulations based on a realistic many-body interaction potential of the embedded-atom-method type with two simple pair potentials, a Lennard-Jones and a Morse potential. We find that qualitatively many aspects of nanoindentation are fairly well reproduced by the simple pair potentials: elastic regime, critical stress and indentation depth for yielding, dependence on the crystal orientation, and even the level of the hardness. The quantitative deficits of the pair potential predictions can be traced back: (i) to the fact that the pair potentials are unable in principle to model the elastic anisotropy of cubic crystals and (ii) as the major drawback of pair potentials we identify the gross underestimation of the stable stacking fault energy. As a consequence these potentials predict the formation of too large dislocation loops, the too rapid expansion of partials, too little cross slip and in consequence a severe overestimation of work hardening. 相似文献
52.
Strategies for computing chemical reactivity indices 总被引:3,自引:0,他引:3
Paul W. Ayers 《Theoretical chemistry accounts》2001,106(4):271-279
Two recent articles [(2000) J Am Chem Soc 122: 2010, (2001) J Am Chem Soc 123: 2007] have explored electron-density-based and external-potential-based chemical reactivity indices. In this article,
methods are presented for computing these indices from the output of a Kohn–Sham density functional theory calculation.
Received: 18 October 2000 / Accepted: 4 April 2001 / Published online: 9 August 2001 相似文献
53.
Szu-Ko WangTing-Chun Lin Sheng-Rui Jian Jenh-Yih JuangJason S.-C. Jang Jiun-Yi Tseng 《Applied Surface Science》2011,258(3):1261-1266
In this study, the effects of post-annealing on the structure, surface morphology and nanomechanical properties of ZnO thin films doped with a nominal concentration of 3 at.% Ga (ZnO:Ga) are investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) and nanoindentation techniques. The ZnO:Ga thin films were deposited on the glass substrates at room temperature by radio frequency magnetron sputtering. Results revealed that the as-deposited ZnO:Ga thin films were polycrystalline albeit the low deposition temperature. Post-annealing carried out at 300, 400 and 500 °C, respectively, has resulted in progressive increase in both the average grain size and the surface roughness of the ZnO:Ga thin film, in addition to the improved thin films crystallinity. Moreover, the hardness and Young's modulus of ZnO:Ga thin films are measured by a Berkovich nanoindenter operated with the continuous contact stiffness measurements (CSM) option. The hardness and Young's modulus of ZnO:Ga thin films increased as the annealing temperature increased from 300 to 500 °C, with the best results being obtained at 500 °C. 相似文献
54.
Starting from a density functional theory (DFT) formalism describing the energy change from one ground state representing an isolated solute, to another one representing the same solute in the field of the solvent, it is possible to obtain a simple and useful expression for the solvation energy in terms of the variation of the electronic chemical potential and global hardness associated to the change from gas to solution phase. Since both properties may be obtained from an orbital theory within the approximate Self Consistent Reaction Field (SCRF) methodology, the proposed model is expected to be useful for the analysis of chemical reactivity in solution. 相似文献
55.
本文以轻质页岩为原料,制备出一种新型硬水软化剂,用该软化剂处理造纸工业用水得到了良好的效果。其使嫩江江水的硬度下降58.1%。 相似文献
56.
Analysis of Solvent Effect on Mechanical Properties of Poly(ether ether ketone) Using Nano-indentation 下载免费PDF全文
Tanveer Iqbal Saima Yasin Ahmad Shakeel Hamayoun Mahmood Fahad Nazir Paul F. Luckham 《化学物理学报(中文版)》2018,31(2):211-215
Poly (ether ether ketone)(PEEK) is a high-performance semi-crystalline thermoplastic polymer.Exposure of the polymeric surface to solvents can have a strong effect like softening/swelling of polymeric network or dissolution.In this study, nano-indentation analysis was performed to study the effect of acetone on the surface mechanical properties of PEEK using different exposure time.The experiments were performed with a constant loading rate (10 nm/s) to a maximum indentation displacement (1000 nm).A 30-second hold segment was included at the maximum load to account for any creep effects followed by an unloading segment to 80% unloading.The indentation hardness and the elastic modulus were computed as a continuous function of the penetration displacement in the continuous stiffness mode (CSM) indentation.The experimental data showed that the peak load decreased from ~5.2 mN to ~1.7 mN as exposure time in solvent environment increased from 0 to 18 days.The elastic modulus and the hardness of PEEK samples also displayed a decreasing trend as a function of exposure time in the solvent environment.Two empirical models were used to fit the experimental data of hardness as a function of exposure time which showed a good agreement with the experimental values. 相似文献
57.
Nanoindentation was performed on cross sections of regenerated cellulose fibres with different structure and properties. Same
as in single-fibre tensile tests, the elastic modulus of lyocell was higher than the elastic modulus of viscose. However,
in spite of its tensile strength being twice as high as viscose, the hardness of lyocell was 15% lower than viscose. The overall
degree of orientation of cellulose chains being higher in lyocell than in viscose, it is proposed that reduced lateral bonding
in lyocell is the reason for the low hardness measured by nanoindentation compared to viscose. 相似文献
58.
59.
Wire arc spraying process was used to deposit FeBSiCrNbMnY amorphous/nanocrystalline alloy coating onto stainless steel substrate. The microstructure of the coating was characterized by using X-ray diffraction (XRD), scanning election microscopy (SEM) equipped with energy dispersive X-ray analysis (EDXA) and transmission electron microscopy (TEM). The coating is about 500 μm in thickness with fully dense and low porosity. The microstructure of the coating is classified into two regions, namely, a full amorphous phase region and homogeneous dispersion of α Fe, Cr nanoscale particles with a scale of 30–60 nm in a residual amorphous matrix region. The formation mechanism of the amorphous and nanocrystalline alloy was discussed. Mechanical properties, such as microhardness and wear resistance of the coating were also analyzed. The Vickers hardness of the coating is around Hv = 900–1050. The relatively wear resistance of the amorphous/nanocrystalline alloy coating is about 3× than that of crystalline structure 3Cr13 martensite stainless steel coating under the same wear testing condition. The FeBSiCrNbMnY amorphous/nanocrystalline alloy coating has high microhardness and excellent wear resistance. 相似文献
60.
L.F Capitán-Vallvey M.D Fernández-Ramos F Santoyo-González 《Analytica chimica acta》2003,481(1):139-148
An optical and reversible test strip that uses an ion-exchange mechanism which responds equally to calcium and magnesium and makes it possible to determine water hardness is described. The transparent test strip, made of a polyester sheet, has a circular polymeric film of plasticised poly(vinyl chloride) (PVC) that contains all of the reagents necessary to produce an equal response to calcium and magnesium, namely, a cation-selective neutral ionophore, such as 4,13-[bis(N-adamantylcarbamoyl)acetyl]-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane, a chromoionophore, such as lipophilised Nile Blue, and potassium tetrakis (4-chlorophenyl)borate as a lipophilic salt, which it is evaluated by absorbance measurement at 655 nm in a standard photometer.All experimental variables that influence test strip response, especially in terms of selectivity and response time, have been studied. The sensor responded linearly to hardness up to 14,800 mg l−1, in activities, expressed as CaCO3. The detection limit is 1.9 mg l−1 as CaCO3, the reproducibility intermembrane at a medium level of the range was 7.0%, as R.S.D., of and 2.6% as intramembrane. The procedure was applied to the determination of hardness in different types of waters (tap, well, mineral and spring) validating results against a reference procedure. This proposed method is quick, inexpensive, selective and sensitive and uses only conventional instrumentation. 相似文献