全文获取类型
收费全文 | 638篇 |
免费 | 33篇 |
国内免费 | 100篇 |
专业分类
电工技术 | 5篇 |
综合类 | 19篇 |
化学工业 | 98篇 |
金属工艺 | 99篇 |
机械仪表 | 8篇 |
建筑科学 | 1篇 |
矿业工程 | 15篇 |
能源动力 | 74篇 |
轻工业 | 1篇 |
石油天然气 | 6篇 |
武器工业 | 2篇 |
无线电 | 165篇 |
一般工业技术 | 166篇 |
冶金工业 | 43篇 |
原子能技术 | 38篇 |
自动化技术 | 31篇 |
出版年
2024年 | 2篇 |
2023年 | 15篇 |
2022年 | 12篇 |
2021年 | 14篇 |
2020年 | 24篇 |
2019年 | 20篇 |
2018年 | 16篇 |
2017年 | 24篇 |
2016年 | 18篇 |
2015年 | 26篇 |
2014年 | 25篇 |
2013年 | 23篇 |
2012年 | 27篇 |
2011年 | 71篇 |
2010年 | 29篇 |
2009年 | 59篇 |
2008年 | 31篇 |
2007年 | 51篇 |
2006年 | 40篇 |
2005年 | 30篇 |
2004年 | 31篇 |
2003年 | 42篇 |
2002年 | 23篇 |
2001年 | 24篇 |
2000年 | 13篇 |
1999年 | 9篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 9篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 11篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 4篇 |
1987年 | 1篇 |
1981年 | 2篇 |
1980年 | 2篇 |
排序方式: 共有771条查询结果,搜索用时 15 毫秒
31.
采用不同络合剂化学水浴沉积ZnS薄膜,应用台阶仪、SEM、XRD、波谱仪等手段测定了ZnS薄膜的厚度、表面、物相结构及透过率等.结果表明,氨水体系沉积薄膜速度明显慢于另外两种体系,沉积的ZnS薄膜都为立方结构.柠檬酸钠体系沉积的ZnS 薄膜结晶和透过率最佳,但薄膜表面缺陷较多;氨水-联氨体系沉积的ZnS薄膜表面质量最佳,结晶和透过率也较好;氨水体系沉积的ZnS薄膜质量较差.用3种体系沉积的ZnS薄膜用于制备铜铟镓硒Cu(In,Ga)Se2太阳电池,氨水和氨水-联氨体系沉积的ZnS薄膜制备的电池转换效率明显高于柠檬酸钠体系沉积的ZnS制备的太阳电池. 相似文献
32.
M.B.H. Breese E. Vittone P.J. Sellin 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2007,264(2):345-360
Since its development in the early 1990’s, ion beam induced charge (IBIC) microscopy has found widespread applications in many microprobe laboratories for the analysis of microelectronic devices, dislocations, semiconductor radiation detectors, semi-insulating materials, high power transistors, charge-coupled arrays, solar cells, light emitting diodes, and in conjunction with Single Event Upset imaging. Several modalities of the techniques have been developed, such as lateral IBIC and time-resolved IBIC. The theoretical model of IBIC generation and collection has developed from a one-dimensional model of charge drift and diffusion to a detailed model of the motion of ion charge carriers in semiconductors and insulators. This paper reviews the current state-of-the-art of IBIC theory and applications. 相似文献
33.
The microstructure and electrochemical behavior of Mg–6Al–1Zn, Mg–6Al–1Zn–1Ga, Mg–6Al–1Zn–1Sn, and Mg–6Al–1Zn–0.5Sn–0.5Ga as anode materials in a 3.5 wt% NaCl solution are compared systematically. The results show that Sn alloying refines the second-phases of Mg–6Zn–1Al by promoting tiny granular Mg17Al12 phases containing Sn, and inspires their disperse distribution. However, the Ga results in the formation of semicontinuous reticular Ga containing Mg17Al12 phases. The comparison of discharge tests indicates that Mg–6Al–1Zn–1Sn has the highest discharge activity, and Mg–6Al–1Zn–1Ga displays the largest hydrogen evolution corrosion resistance in 3.5 wt% NaCl solution at 298 K. The synergy of Ga and Sn can shorten discharge activation time and promote low discharge potential. In addition, the utilization efficiencies of the alloys decrease as follows: Mg–6Al–1Zn–1Ga > Mg–6Al–1Zn–0.5Sn–0.5Ga > Mg–6Al–1Zn–1Sn > Mg–6Zn–1Al. This study illustrates that the Mg–6Al–1Zn–0.5Sn–0.5Ga alloy has acceptable utilization efficiency and desirable electrochemical activity, which implies that doping Ga and Sn obtains a balance between discharge activity and utilization efficiencies. 相似文献
34.
Si基氨化ZnO/Ga2O3薄膜制备GaN纳米线 总被引:1,自引:0,他引:1
利用射频磁控溅射法在Si(111)衬底上溅射ZnO中间层和Ga2O3薄膜,然后在管式炉中常压下通氨气对ZnO/Ga2O3薄膜进行氨化,高温下ZnO层在氨气气氛中挥发,而Ga2O3薄膜和氨气反应合成出GaN纳米线.X射线衍射测量结果表明利用该方法制备的GaN纳米线具有沿c轴方向择优生长的六角纤锌矿结构.利用扫描电子显微镜、透射电子显微镜、傅里叶红外透射谱、能量弥散谱及选区电子衍射观测并分析了样品的形貌、成分和晶格结构.研究发现ZnO层的挥发有利于Ga2O3和NH3反应合成GaN纳米线. 相似文献
35.
In this work, gallium doped copper sulfide (Ga-doped CuS) nanocrystals were prepared using a solvothermal method. The effects of Ga doping on the crystal structures, chemical composition, morphology, optical properties and thermal performance of copper sulfide (CuS) were investigated. The Ga-doped CuS nanocrystals had a hexagonal structure comparable to that of pure CuS. The Cu+/Cu2+ ratio first decreased and then increased with increasing Ga3+ doping. Both CuS and Ga-doped CuS exhibited nanoplate and nanorod morphologies. The visible transmittance of the Ga-doped CuS films was in the range of 61–77.1%. Importantly, the near-infrared (NIR) shielding performance of the films can be tuned by adjusting the concentration of the Ga dopant. The NIR shielding value of the optimal Ga-doped CuS film was 72.4%, which was approximately 1.5 times as high as that of the pure CuS film. This can be ascribed to the enhanced plasmonic NIR absorption that resulted from an increase in the hole concentration after doping with Ga3+ ions. In the thermal performance test, the Ga-doped CuS film lowered the interior temperature of the heat box by 9.1 °C. Therefore, the integration of good visible transmittance and high NIR shielding performance make the Ga-doped CuS nanocrystals a promising candidate for energy-efficient window coatings. 相似文献
36.
The effects of the fourth element Si on the martensitic transformation and magnetic properties of Ni–Fe–Ga magnetic shape memory alloys were investigated. A complete thermoelastic martensitic transformation in Ni–Fe–Ga–Si alloys was observed in the temperature range of 218–285 K. The martensitic transformation temperatures of Ni–Fe–Ga alloys are obviously decreased by the substitution of Si for Ga element, that is, the substitution of 1 at.% Si for Ga leads to a decrease of martensitic transformation temperature of about 39.6 K. Moreover, the substitution of Si for Ga leads to a decrease of the saturation magnetic field and the magnetic anisotropy constant K1 obviously. 相似文献
37.
The electrochemical performance of LiGayCo1−yO2 electrodes,y = 0.005 and 0.1, was studied. Charge/discharge curves in galvanostatic condition were obtained for a series of voltages ranging from 4.35 to 4.7 V. Samples were previously characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR), X-ray absorption spectroscopy (XAS) and conductivity measurements. Comparison of data obtained for LiGayCo1−yO2 and the pristine oxide LiCoO2 is provided. Ga doping at 0.5 mol% drastically reduces the electrode capacity fading when charges at 4.35 or 4.5 V are applied, while Ga doping at 10 mol% spoils the Ga-doped oxides electrochemical response, even at a cut-off limit of 4.35 V. These positive and negative effects were attributed to changes in both the electronic conductivity and local structure of LiCoO2, induced by substitution of Co for Ga and cationic disorder. For y = 0.005, a slight distortion in the LiCoO2 local structure occurs, and formation of states in the band gap that the raise oxide electronic conductivity is observed, explaining the electrochemical improvement in LiGayCo1−yO2. In contrast, hybridization with oxygen occurs when y = 0.1, opening LiCoO2 band gap and making LiGayCo1−yO2 an insulator and a cationic disorder material that leads to poor electrochemical performance. Finally, XAS results show that Ga doping does not change the LiCoO2 charge transfer mechanisms, where oxygen is reduced during lithium extraction. 相似文献
38.
Ga2O3/GdGaO dielectric stacks have been grown on GaAs for MOSFETs. This paper highlights variations in the characteristics of GdGaO as the Gd flux, Ga2O flux and substrate temperature are changed. The growth rate, composition, crystallinity are discussed and the sheet resistance of final MOSFET structures are presented. The Gd compositional variation with depth is examined using Rutherford back scattering (RBS) and electron energy loss spectroscopy (EELS). 相似文献
39.
40.
Guo Shiyi Yuan Duorong Shi Xuzhong Cheng Xiufeng Zhang Xiqing Yu Fapeng 《中国稀土学报(英文版)》2007,25(Z1):66-68
Single crystal of cobalt (Co)-doped Y3Sc2Ga3O12 (YSGG) with the dimensions up to φ20×40mm3 and undoped YSGG crystal with the dimensions up to φ28×60mm3 have been grown using the Czochralski technique. The structure of the crystal was characterized by the X-ray powder diffraction (XRPD) method. The absorbance spectra of the crystal shows that it has strong absorption bands at 606 and 1540nm. The results indicate that the crystal Y3Sc2Ga3O12 may be a kind of good Q-switch material. 相似文献