首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   487篇
  免费   2篇
  国内免费   41篇
电工技术   2篇
综合类   4篇
化学工业   117篇
金属工艺   63篇
机械仪表   3篇
矿业工程   2篇
能源动力   143篇
武器工业   1篇
无线电   25篇
一般工业技术   70篇
冶金工业   14篇
原子能技术   6篇
自动化技术   80篇
  2023年   34篇
  2022年   53篇
  2021年   69篇
  2020年   35篇
  2019年   35篇
  2018年   34篇
  2017年   34篇
  2016年   17篇
  2015年   8篇
  2014年   38篇
  2013年   30篇
  2012年   23篇
  2011年   35篇
  2010年   23篇
  2009年   22篇
  2008年   10篇
  2007年   8篇
  2006年   6篇
  2005年   1篇
  2004年   4篇
  2003年   1篇
  2002年   1篇
  2001年   4篇
  1999年   4篇
  1998年   1篇
排序方式: 共有530条查询结果,搜索用时 31 毫秒
1.
Solute-induced grain boundary (GB) strengthening is effective in improving the toughness and tensile strength of polycrystalline alloys. In this work, GB segregation behaviors of solute elements in Al alloys and their potential effects on GB binding have been systematically investigated from first-principles energetics. The low-energy Σ3(111) and Σ11(113) are immune to vacancy segregation, while high-energy Al GBs, such as Σ13(320), Σ9(221), Σ5(210), and Σ5(310), can attract both vacancies and solutes. Under-sized elements (Ni, Fe, Co, Cu) and similar-sized elements (Si, Zn, Ag, and Ti) prefer interstitial or vacancy sites at the GB interface, while over-sized elements (Mg, Zr, Sc, Er) tend to substitute Al or vacancy-neighboring sites at the GB interface. Segregated vacancies weaken GBs. Under-sized Ni, Co, Cu, similar-sized Ti, and over-sized Zr, Er, can directly enhance Al GBs, while similar-sized Ag and over-sized Mg reduce the GB binding strength. Solute strengthening or weakening effects tend to be always mitigated, more or less, by GB-segregated vacancies.  相似文献   
2.
First-principles energetics calculations were performed to investigate the structures and relative stabilities of six low miller-index surfaces of orthorhombic YAlO3 (YAP). The stoichiometric YAP (100) and (001) were predicted to have the lowest surface energies of 1.91 and 1.96 J/m2, respectively. Using a thermodynamic defect model, non-stoichiometric YAP surface energies were further predicted as a function of ${P}_{{\text{O}}_{2}}$(${P}_{{\text{O}}_{2}}<1\ \mathrm{atm}$) and temperature (T). All the results were combined to construct the surface phase diagrams at T = 300 and 1400 K, revealing the strong correlation of the surface stabilities of YAP with its surface stoichiometry.  相似文献   
3.
The structure, chemical bonding and photoemission of amorphous hydrogenated silicon carbonitride (a-SiCN:H) films deposited by plasma-enhanced chemical vapor deposition (PECVD) using hexamethyldisilazane as a main precursor at different hydrogen flow rates are studied. Film properties are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), absorption optical spectra and photoluminescence (PL). The photoluminescence spectra were presented by four photoemission bands centered at 441–451, 489–496, 530–535 and 577–601 (in nm). To explain structural and photoluminescence properties of the deposited films, first-principles molecular dynamics simulations of un-hydrogenated and hydrogenated silicon carbonitride samples were carried out. Based on experimental and theoretical results a possible explanation of the photoemission of the deposited films and its evolution with increasing hydrogen flow rate was done.  相似文献   
4.
A recent commentary by Santhosh and Ravindran on our paper (Int. J. Hydrogen Energy 2014, 39:10,606) demonstrated that the interaction between H2 and MXene (Sc2C and Ti2C) phases are not Kubas-type and should be of weak physisorption, and thus made a conclusion that 2D Sc2C and Ti2C are not suitable for practical hydrogen storage applications. In this responses, we recalculated hydrogen adsorption on 2D Sc2C and Ti2C by using different exchange-correlation functionals. And based on the calculated results, bare MXenes (especially the Ti2C) are suitable as hydrogen storage materials at temperatures of several tens degrees lower than room temperature. And the hydrogen adsorptions on the MXenes terminated with oxygen group were also investigated. Among the Ti2C, Sc2C and their oxygen-functional counterparts, the binding energy of H2 on Sc2CO2 surface is the closest to the ideal range of 0.16–0.42 eV/H2 at ambient conditions, and thus the Sc2C with oxygen group is expected to be more suitable as hydrogen storage materials.  相似文献   
5.
By the first-principles calculations, the sensitivity of CO, H2O and NO adsorption on Au doped SnSe2 monolayer surface is investigated. The results show that CO and H2O molecules are physically adsorbed on Au doped SnSe2 monolayer and act as donors to transfer 0.012 e and 0.044 e to the substrate, respectively. However, the NO molecule is chemically adsorbed on substrate and acts as an acceptor to obtain 0.116 e from the substrate. In addition, our results also show that the biaxial strain can effectively improve the adsorption energy and charge transfer of gas molecules adsorbed on the substrate surface. Also, the recovery time of desorbed gas molecules on the substrate surface is calculated, and the results indicate that the Au doped SnSe2 is a perfect sensing material for detection and recovery of CO and NO under ?8% strain.  相似文献   
6.
Two dimensional (2D) materials have demonstrated huge potential in wide applications ranging from nanodevices to energy storage. In this work, we propose a series of double-metal MXenes functionalized with various terminal atoms (M2M’C2T2), including B, N, O, P and S, based on density-functional theory (DFT) calculation. We screen out a series of stable structures and study their magnetic and electronic properties. We find that the magnetism of M2M’C2T2 can be regulated according to different transition metals and terminal atoms. The magnetic moments of Cr2TiC2T2 and Cr2VC2T2 (T = N, O or S) are mainly contributed by chromium, while those of Mo2VC2T2 (T = N, O or S) are originated from vanadium. We also find that these monolayers are metal with spontaneous conductivity, which is favorable for the electrocatalysis. The Gibbs free energies for the adsorption of hydrogen atoms on Cr2TiC2S2, Cr2VC2S2 and Mo2TiC2P2 are close to zero, indicating their high catalytic activity for hydrogen evolution reaction (HER). Our findings suggest that the functionalized double-metal MXenes are promising materials for magnetic nanodevices and electrocatalysts.  相似文献   
7.
The electronic structures of Zr8Co8 and its hydrides have been systematically investigated using the first-principles calculation based on density functional theory. Additionally, the influence of the Ti and Hf doping on the atomic bonding properties of Zr8Co8 and its hydrides (Zr7HfCo8, Zr7HfCo8H, Zr16Co15HfH48, Zr7TiCo8, Zr7TiCo8H, and Zr16Co15TiH48 compounds) were also studied to provide new insights into the hydrogenation of Zr8Co8. The Ti and Hf atoms were occupied the Zr position in the ZrCo alloy, while they were occupied the Co position in the Zr16Co16H48 system. Ti and Hf doping could achieve the purpose of anti-disproportionation. Ti and Hf could weak the Zr–Co bond for the improvement of the hydrogenation performance of Zr8Co8, and the covalence of the Co–H bond was higher than that of the Zr–H bond. The existence of a Co–H covalent bond in the crystal is conducive to the hydrogen absorption of Zr8Co8 to form Zr16Co16H48. Inhibition of Co–H interaction during Zr8Co8 hydrogenation can accelerate the formation of Zr8Co8H for the improvement of its hydrogenation performance.  相似文献   
8.
The vanadium hydrides have better hydrogen storage capacity in comparison to the other metal hydrides. Although the structure of VH2 hydride has been reported, the structural stability, electronic and optical properties of VH2 hydride are unclear. To solve these problems, we apply the first-principles method to study the structural stability, electronic and optical properties of VH2 hydrides. Similar to the metal dihydrides, four possible VH2 hydrides such as the cubic (Fm-3m), tetragonal (I4/mmm), tetragonal (P42/mnm) and orthorhombic (Pnma) are designed. The result shows that the cubic VH2 hydride is a thermodynamic and dynamical stability. In particular, the tetragonal (I4/mmm) and the orthorhombic (Pnma) VH2 hydrides are firstly predicted. It is found that these VH2 hydrides show metallic behavior. The electronic interaction of V (d-state)-H (s-state) is beneficial to improve the hydrogen storage in VH2 hydride. In addition, the formation of V–H bond can improve the structural stability of VH2 hydride. Based on the analysis of optical properties, it is found that all VH2 hydrides show the ultraviolet response. Compared to the tetragonal and orthorhombic VH2 hydrides, the cubic VH2 hydride has better storage optical properties. Therefore, we believe that the VH2 hydride is a promising hydrogen storage material.  相似文献   
9.
Two-dimensional (2D) materials have been widely developed due to their attractive properties. Here, by using density functional theory (DFT) calculations, for the first time, we explore potential applications of the novel XIS (X = Al, Ga, In) monolayer 2D materials on photocatalytic water splitting. A series of simulations were carried out to predict and study the structural, elastic, phononic, optical and electronic properties of 2D XIS materials. The results show that GaIS and InIS demonstrate low thermal conductivity. For optical properties, AlIS shows strong light absorption coefficients and refractive index only under ultraviolet (UV) light, while GaIS and InIS show stronger performance under both visible light and UV light with the band edge positions spanned the redox potential of water. The reasonable band positions and bandgaps make them promising photocatalysts for water splitting. This work reveals the potential applications of monolayer 2D XIS in thermal, electronic, and photocatalytic water splitting.  相似文献   
10.
The outstanding physical properties make TM5Si4 silicides become the potential silicon-based transition-metal ultrahigh-temperature materials. In present work, we adopt the first-principles scheme to explore the structural stability, mechanical properties and explain the hydrogenated mechanism of Ti5Si4, Zr5Si4 and Hf5Si4 using the electronic structures. And the investigation increases the theoretical support for the developments and applications of TM5Si4 silicides. Three hydrogenated models have shown that the hydrogen displays the stability for hydrogenated TM5Si4 compounds. Furthermore, the introduction of hydrogen occupation has weakened the elastic properties of TM5Si4. The metallic property of TM5Si4 and three hydrogenated models was confirmed by the electronic structures. The localized hybridization between hydrogen and TM5Si4 confirm the hydrogenated structural stability.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号