全文获取类型
收费全文 | 14367篇 |
免费 | 983篇 |
国内免费 | 625篇 |
专业分类
电工技术 | 1228篇 |
综合类 | 857篇 |
化学工业 | 3674篇 |
金属工艺 | 3287篇 |
机械仪表 | 907篇 |
建筑科学 | 210篇 |
矿业工程 | 211篇 |
能源动力 | 1098篇 |
轻工业 | 564篇 |
水利工程 | 43篇 |
石油天然气 | 114篇 |
武器工业 | 55篇 |
无线电 | 734篇 |
一般工业技术 | 1290篇 |
冶金工业 | 1091篇 |
原子能技术 | 97篇 |
自动化技术 | 515篇 |
出版年
2024年 | 39篇 |
2023年 | 167篇 |
2022年 | 311篇 |
2021年 | 394篇 |
2020年 | 423篇 |
2019年 | 355篇 |
2018年 | 266篇 |
2017年 | 420篇 |
2016年 | 403篇 |
2015年 | 389篇 |
2014年 | 755篇 |
2013年 | 773篇 |
2012年 | 913篇 |
2011年 | 1232篇 |
2010年 | 933篇 |
2009年 | 985篇 |
2008年 | 862篇 |
2007年 | 1058篇 |
2006年 | 934篇 |
2005年 | 717篇 |
2004年 | 571篇 |
2003年 | 493篇 |
2002年 | 456篇 |
2001年 | 411篇 |
2000年 | 342篇 |
1999年 | 268篇 |
1998年 | 227篇 |
1997年 | 183篇 |
1996年 | 137篇 |
1995年 | 126篇 |
1994年 | 123篇 |
1993年 | 72篇 |
1992年 | 56篇 |
1991年 | 43篇 |
1990年 | 35篇 |
1989年 | 23篇 |
1988年 | 21篇 |
1987年 | 10篇 |
1986年 | 8篇 |
1985年 | 15篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1964年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
为了精确计算三维静电场中球形电极表面的电场强度,提出了基于球坐标变换的球面曲边三角形边界元法。该方法中积分的区域为球面,求解函数采用球面上球坐标线性插值,单元的外法线方向为严格的球面法线方向。计算结果表明,与平面直边单元相比,在网格剖分节点相同时,球面曲边三角形边界元法的计算精度明显提高。在计算精度要求相同时,球面曲边三角形边界元法节点数较少,具有计算速度快,占用计算机内存少等优点。 相似文献
992.
Kexin LI Zhexun YU Yanhong LUO Dongmei LI Qingbo MENG 《材料科学技术学报》2007,23(5):577-582
Dye-sensitized solar cell (DSC) consists a combination of several different materials: photoanodes with nanoparticulated semiconductors, sensitizers, electrolytes and counter electrodes (CEs). Each materials performs specific task for the conversion of solar energy into electricity. The main function of CE is to transfer electrons to the redox electrolyte and regenerate iodide ion. The work of CE is mainly focused on the studies of the kinetic performance and stability of the traditional CEs to improve the overall efficiency of DSC, seeking novel design concepts or new materials. In this review, the development and research progress of different CE materials and their electrochemical performance, and the problems are discussed. 相似文献
993.
通过共沉淀法制备了铈掺杂二氧化锡超细粉体,平均粒径为20nm,并制得氧化锡电极样品。主要研究了在氧化锡电极中添加不同含量的Ce对电极导电性能的影响情况,通过XRD、SEM和电阻率表征样品性能。实验结果表明,Ce掺杂有利于提高SnO2电极的导电性能,并随Ce含量增加,导电性也提高。共沉淀制得的原料粉体具有纯度高、掺杂均匀等特点,有利于充分发挥添加剂在SnO2电极中起到的提高导电性能的作用,且共沉淀法操作较简便,易实现从实验室制备到实际生产的转化。 相似文献
994.
H. Kakiuchi H. Ohmi M. Harada H. Watanabe K. Yasutake 《Science and Technology of Advanced Materials》2007,8(3):137-141
The formation of silicon dioxide (SiO2) layers at low temperatures (150-400 °C) by atmospheric pressure plasma oxidation of Si(0 0 1) wafers have been studied using a gas mixture containing He and O2. A 150 MHz very high frequency (VHF) power supply was used to generate high-density atomic oxygen in the atmospheric pressure plasma. Oxidation rate, structure, and thickness and refractive index profiles of the oxidized layers were investigated by ellipsometry and infrared absorption spectroscopy. Atomic force microscopy was also employed to observe atomic-scale morphologies of the layer surface and wafer Si surface, after chemical removal of the oxidized layers. It was found that stoichiometric SiO2 layers were obtained at higher oxidation rates than conventional dry O2 thermal oxidation and radical oxidation processes, even at a very low substrate temperature of 150 °C. Although thickness variations were observed in the plasma region, the refractive index was independent of both substrate temperature and VHF power. In addition, the SiO2 surface and SiO2/Si interface roughnesses were comparable to those obtained in conventional dry oxidation at high temperatures. 相似文献
995.
An atmospheric-pressure glow-discharge micro plasma in contact with liquid paraffin is stably generated by using a capacitively coupled plasma method with a mesh electrode. When characteristics of the plasma are measured in the boundary between the micro plasma (gas-phase) and liquid paraffin (liquid-phase) using optical emission spectroscopy, spectrum peaks of the emission of CH and C2 which dissociate from paraffin are observed. The result indicates that solution can feed particles to the plasma at gas-liquid interface and this plasma is accordingly expected to promote an attractive plasma process for creating materials consisting of elements in various solutions. 相似文献
996.
有机发光显示被认为是下一代最理想的显示技术,具有自主发光、功耗小、视角宽、成本低和响应速度快等优点。本文在简述有机电致发光器件的电极结构和发光材料的基础上,重点介绍了有机显示器件的驱动技术和面板的研发成果,并展望未来发展的前景。 相似文献
997.
GUO DongYun LI MeiYa LIU Jun PEI Ling YU BenFang ZHAO XingZhong YANG Bin WANG YunBo & YU Jun Department of Physics Wuhan University Wuhan China Department of Electronic Science Technology Huazhong University of Science Technology Wuhan China 《中国科学E辑(英文版)》2007,50(4)
The Bi4Zr0.5Ti2.5O12 (BZT) thin films were fabricated on the LaNiO3 bottom electrode using sol-gel method. The structure and morphology of the films were character-ized using X-ray diffraction, AFM and SEM. The results show that the films have a perovskite phase and dense microstructure. The 2Pr and 2Vc of the Pt/BZT/LaNiO3 capacitor are 28.2 μC/cm2 and 14.7 V respectively at an applied voltage of 25 V. After the switching of 1×1010 cycles, the Pr value decreases to 87% of its pre-fatigue val-ues. The dielectric constant (ε) and the dissipation factor (tanδ) of the BZT thin films are about 204 and 0.029 at 1 kHz, respectively. The films show good insulating behavior according to the test of leakage current. The clockwise C-V hysteresis curve observed shows that the Pt/BZT/LaNiO3 structure has a memory effect be-cause of the BZT film’s ferroelectric polarization. 相似文献
998.
999.
全光纤热光型可变光衰减器 总被引:10,自引:0,他引:10
根据光纤包层中的倏逝场机制,将具有热光效应的聚合物材料直接覆盖在侧边抛磨光纤上,进行了全光纤热光型可变光衰减器(VOA)的研究.根据理论分析,确定了在侧边抛磨光纤的抛磨区上覆盖材料的折射率与纤芯中光衰减量之间的关系,为选择适当折射率的热光材料提供依据.设计适当的侧边抛磨区,利用先进的轮式侧边抛磨技术,制备了侧边抛磨光纤,以达到最佳可变光衰减效果.采用螺绕电极和优化封装,制作出性能优良的全光纤热光型可变光衰减器.性能测试表明,器件插入损耗小于0.1 dB,衰减范围为0~80 dB,偏振相关损耗小于0.02 dB,背向反射大于70 dB.该方法制作的全光纤热光型可变光衰减器具有可用电驱动调控、可靠性高等优点. 相似文献
1000.
Y. Bai X. Liu L. Chen Khizar-ul-Haq M.A. Khan W.Q. Zhu X.Y. Jiang Z.L. Zhang 《Microelectronics Journal》2007,38(12):1185-1190
An organic thin-film transistor (OTFTs) having OTS/SiO2 bilayer gate insulator and MoO3/Al electrode configuration between gate insulator and source–drain (S–D) electrodes has been investigated. Thermally grown SiO2 layer is used as the OTFT gate dielectric and copper phthalocyanine (CuPc) for an active layer. We have found that using silane coupling agents, octadecyltrichlorosilane (OTS) on SiO2, surface energy of SiO2 gate dielectric is reduced; consequently, the device performance has been improved significantly. This OTS/SiO2 bilayer gate insulator configuration increases the field-effect mobility, reduces the threshold voltage and improves the on/off ratios simultaneously. The device with MoO3/Al electrode has similar source–drain current (IDS) compared to the device with Au electrode at same gate voltage. Our results indicate that using double-layer of insulator and modified electrode is an effective way to improve OTFT performance. 相似文献