全文获取类型
收费全文 | 225篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
综合类 | 18篇 |
化学工业 | 48篇 |
金属工艺 | 1篇 |
机械仪表 | 12篇 |
建筑科学 | 4篇 |
能源动力 | 1篇 |
轻工业 | 19篇 |
水利工程 | 2篇 |
石油天然气 | 6篇 |
武器工业 | 10篇 |
无线电 | 15篇 |
一般工业技术 | 2篇 |
冶金工业 | 58篇 |
自动化技术 | 41篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2017年 | 2篇 |
2016年 | 8篇 |
2015年 | 6篇 |
2014年 | 28篇 |
2013年 | 10篇 |
2012年 | 25篇 |
2011年 | 25篇 |
2010年 | 38篇 |
2009年 | 6篇 |
2008年 | 4篇 |
2007年 | 4篇 |
2006年 | 4篇 |
2005年 | 1篇 |
2004年 | 2篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 6篇 |
2000年 | 3篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 2篇 |
1995年 | 3篇 |
1993年 | 4篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1988年 | 2篇 |
排序方式: 共有237条查询结果,搜索用时 265 毫秒
81.
Blue emitting rare earth(Eu2+,Ce3+) doped BaAl2Si2O8 phosphors were synthesized by combustion methods at 600 oC. BaAl2Si2O8: Eu2+ phosphor showed isolated broad blue emission band at 455 nm, when it was excited with the wavelength of 329 nm. Whereas BaAl2Si2O8:Ce3+ phosphor exhibited blue emission band at 442 nm, under 303 nm excitation wavelength. These observed emission bands of Eu2+ and Ce3+ ions corresponded to 5d-4f allowed transitions. The position of emission band was calculated by using the equationE=Q[1-〔V/4〕^1/V)]× 10 (nEar/80)Also the spin orbit splitting difference in the ground state levels of Ce3+ ion was studied by Gaussian curve fitting. Broad absorption and emission bands in blue regions made prepared phosphors a promising blue host for the white-LEDs. 相似文献
82.
In this study a series of trivalent lanthanum complexes with 4-(R)-cinnamate (4-Rcinn, R=H(1), MeO(2), Cl(3)) and 4-methoxyphenylacetate ligands (4) were prepared and their antifungal activity against Candida albicans, Aspergillus niger and Trichophyton mentagrophytes were examined. Compounds 1-4 were synthesized by a metathesis reaction and fully characterized by elemental analysis, IR, 1H and 13C NMR spectroscopy, fluorescence spectra, thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC) and X-ray diffraction powder patterns. In emission studies, it was observed that lu-minescence intensity was enhanced in the presence of lanthanide ion. The results of X-ray diffraction patterns indicated that all com-plexes studied exhibited crystalline structure. Thermal behavior by TG, DTG, and DSC studies permitted to estimating the hydration degree of the compounds and showed the formation of decomposition products like lanthanum oxide. Determined by antifungal stud-ies, lanthanum complexes 1-4 demonstrated antifungal activity toward all pathogenic fungal strains tested. Compounds 2 and 4 showed significant growth inhibition for A. niger and C. albicans, respectively. 相似文献
83.
<正>作为全球最大的涂料制造商,阿克苏诺贝尔始终将可持续发展深植于其发展战略之中。而作为其业务部之一的阿克苏诺贝尔粉末涂料,以成为首家获得可持续材料评价技术(SMaRT)白金证书的涂料制造商的殊荣和积极推进不含TGIC环保系列粉末涂料的实际行动,向社会提交了一份满意的答卷,很好地诠释了其可持续发展之道,使其赢得了可持 相似文献
84.
85.
FU Shaobo CHEN Baojiu LI Xiangping ZHANG Jinsu TIAN Yue SUN Jiashi ZHONG Haiyang CHENG Lihong WU Zhongli 《中国稀土学报(英文版)》2012,30(10):979-984
Eu3+-doped binary borate glasses with different metal oxide components RO (R=Ca, Sr, Ba, Zn or Pb) were prepared by meltquenching technique. The fluorescent spectral properties of Eu3+in these glasses were experimentally studied. The analysis on the phonon sidebands (PSBs) indicated that RO component did not cause obvious change of the electron-phonon coupling constant (EPC). By inspecting the optical absorption edges it was found that RO could greatly affect the band gap energy, and the glass with PbO component revealed the smallest band gap energy, the glasses with ZnO, BaO and SrO showed similar band gap energy. The optical transition intensity parameters of Eu3+in all studied glasses were calculated, it was found that for each sample its value of2 was larger than that of 4 and 6, and the sample with PbO component exhibited the smallest2, but the λ values for ZBE, CBE, BBE and SBE were very similar. These results might be helpful for the design of borate glasses. 相似文献
86.
DU Qingqing ZHOU Guangjun ZHOU Juan ZHOU Haifeng ZHAN Jie YANG Zhongsen 《中国稀土学报(英文版)》2012,30(10):1000-1004
CaZrO3:Sm and CaZrO3:Sm,Gd nanophosphors were synthesized by a facile and efficient sol-gel combustion method. Their structure and optical properties were studied. The photoluminesce (PL) results showed that the phosphor could be efficiently excited by irradiation at wavelengths in the visible light region (350-430nm). The CaZrO3:Sm nanophosphor exhibited strong yellow-green, orange and red emissions with peak wavelength centered at 565nm (4G5/2→6H5/2), 601nm (4G5/2→6H7/2) and 645nm (4G5/2→6H9/2), respectively. The incorporation of Gd3+ ions could greatly improve the luminescence intensity. The highest emission intensity was observed with 2mol.% Gd3+ doped CaZrO3:3mol.% Sm powder. The material had potential application in the development of materials for LED’s and other optical devices in the visible region. 相似文献
87.
ZHU 《中国稀土学报(英文版)》2010,28(6):907-913
Two-step steam reforming of methane(SRM)is a novel chemical looping process towards the production of pure hydrogen and syngas(synthesis gas),consisting ofa syngas production step and a water-splitting step.Renewable energy can be used to drive this process for hydrogen production,especially solar energy.CeO2-Fe2O3 complex oxide oxygen carrier was prepared by the impregnation method and characterized by means of X-ray diffractometer(XRD),Raman spectroscopy(Raman)and hydrogen programmed reduction(H2-TPR).CH4temperature programmed and isothermal reactions were adopted to test syngas production reactivity,and water splitting reaction was employed to investigate water-splitting activity.Moreover,two-step SRM performance was evaluated by a successive redox cycle.The results showed that CO-uncontaminated H2 and highly selective syngas(with H2/CO ratio close to 2)could be respectively obtained from two steps,and CeFeO3 formation was found in the first redox cycle and proved to be enhanced by the redox treatment.After 10 successive cycles,obvious CeFeO3 phase was detected,which may be responsible for favorable successive redox cycle performances. 相似文献
88.
XING 《中国稀土学报(英文版)》2010,28(6):927-930
Eutectic Al-12.6 wt.%Si alloys with various contents of the rare earth dement Er were prepared by the conventional casting technique.The effect of Er on the microstructure and properties of the eutectic Al-Si alloys was investigated using optical microscopy,scanning electron microscopy as well as the friction and wear tests.It was found that the addition of Er obviously improved the anti-wear properties,and reduced the friction coefficient of the alloys.The appropriate addition of Er would change the size and shape of the eutectic silicon,and thereby refine the microstructure of the Al-Si alloys.The refinement mechanism was also discussed. 相似文献
89.
ZHANG 《中国稀土学报(英文版)》2010,28(6):944-947
Rapidly solidified nanocrystalline α-Fe/Nd2Fe14B alloys with enhanced coercivity were obtained by melt spinning.The effects of Ti addition on the microstructore and magnetic properties of the nanocomposite α-Fe/Nd2Fe14B alloys were investigated by X-ray diffraction(XRD)and superconducting quantum interference device(SQUID)magnetometer.The analysis of XRD showed that Vα-Fe estimated to be about 35.3% in the Ti-free α-Fe/Nd2Fe14B nanocomposites decreased down to 26.5% as the addition of was 5 at.% Ti.Accordingly,adding Ti resulted in relevant improvements of magnetic properties,especially of the coercivity Hc from 595 kA/m up to 1006 kA/m.The dependence of Mirrev(H)/2Mr on the reverse field H indicated that nucleation was the dominating mechanism for the magnetization reversal in these nanocomposites.The analysis of the temperature dependence of the demagnetization curve in the α-Fe/Nd2Fe14B nanocomposite magnets indicated that a reduction of αex could play a leading role in an increase in the coercivity of Ti-doped sample. 相似文献
90.
A new lanthanum complex formulated as {(bpyH2)[La(btc)(H2O)4(NO3)]·2H2O}n (1) (btcH4=benzene-1,2,4,5-tetracarboxylic acid; bpy=4,4′-bipyridine) was hydrothermally synthesized. The complex was characterized by FT-IR spectroscopy, elemental analysis and X-ray diffraction. X-ray crystal structural analysis revealed that the compound belonged to the monoclinic space group C2/c with cell parameters a= 1.42806(7) nm, b=1.10258(5) nm, c=1.60333(8) nm and β=101.9400(10)°. The complex was polymeric with LaIII atoms linked by four O atoms from two carboxylate groups of one benzene-1,2,4,5-tetracarboxylate. The LaIII atom was ten coordinated in a distorted tetracapped trigonal prism. In the crystal structure, a wide range of noncovalent interactions consisting of hydrogen bonding (of the types of O—H…O, N—H…O and C—H…O) and ion pairing interactions connected the various components into a supramolecular structure. 相似文献