全文获取类型
收费全文 | 137395篇 |
免费 | 18109篇 |
国内免费 | 7196篇 |
专业分类
电工技术 | 51397篇 |
技术理论 | 8篇 |
综合类 | 11323篇 |
化学工业 | 12406篇 |
金属工艺 | 2901篇 |
机械仪表 | 5868篇 |
建筑科学 | 5486篇 |
矿业工程 | 2670篇 |
能源动力 | 12226篇 |
轻工业 | 2194篇 |
水利工程 | 3202篇 |
石油天然气 | 1832篇 |
武器工业 | 908篇 |
无线电 | 20189篇 |
一般工业技术 | 7138篇 |
冶金工业 | 2801篇 |
原子能技术 | 2873篇 |
自动化技术 | 17278篇 |
出版年
2024年 | 257篇 |
2023年 | 1845篇 |
2022年 | 3302篇 |
2021年 | 3969篇 |
2020年 | 4533篇 |
2019年 | 3781篇 |
2018年 | 3456篇 |
2017年 | 4752篇 |
2016年 | 5254篇 |
2015年 | 6111篇 |
2014年 | 9957篇 |
2013年 | 8875篇 |
2012年 | 11549篇 |
2011年 | 12310篇 |
2010年 | 9031篇 |
2009年 | 8926篇 |
2008年 | 8895篇 |
2007年 | 10027篇 |
2006年 | 8801篇 |
2005年 | 7231篇 |
2004年 | 5810篇 |
2003年 | 4880篇 |
2002年 | 3780篇 |
2001年 | 3138篇 |
2000年 | 2506篇 |
1999年 | 1841篇 |
1998年 | 1356篇 |
1997年 | 1094篇 |
1996年 | 1052篇 |
1995年 | 871篇 |
1994年 | 726篇 |
1993年 | 517篇 |
1992年 | 473篇 |
1991年 | 306篇 |
1990年 | 276篇 |
1989年 | 236篇 |
1988年 | 172篇 |
1987年 | 125篇 |
1986年 | 100篇 |
1985年 | 84篇 |
1984年 | 122篇 |
1983年 | 88篇 |
1982年 | 76篇 |
1981年 | 34篇 |
1980年 | 22篇 |
1979年 | 17篇 |
1978年 | 16篇 |
1977年 | 10篇 |
1959年 | 26篇 |
1951年 | 28篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
52.
《工程(英文)》2020,6(12):1395-1402
In this report, we show that hyperspectral high-resolution photoluminescence mapping is a powerful tool for the selection and optimization of the laser ablation processes used for the patterning interconnections of subcells on Cu(Inx,Ga1−x)Se2 (CIGS) modules. In this way, we show that in-depth monitoring of material degradation in the vicinity of the ablation region and the identification of the underlying mechanisms can be accomplished. Specifically, by analyzing the standard P1 patterning line ablated before the CIGS deposition, we reveal an anomalous emission-quenching effect that follows the edge of the molybdenum groove underneath. We further rationalize the origins of this effect by comparing the topography of the P1 edge through a scanning electron microscope (SEM) cross-section, where a reduction of the photoemission cannot be explained by a thickness variation. We also investigate the laser-induced damage on P1 patterning lines performed after the deposition of CIGS. We then document, for the first time, the existence of a short-range damaged area, which is independent of the application of an optical aperture on the laser path. Our findings pave the way for a better understanding of P1-induced power losses and introduce new insights into the improvement of current strategies for industry-relevant module interconnection schemes. 相似文献
53.
通过粒子图像测速流场实验与传热实验相结合,研究了内插螺旋立式上行管的螺旋节距、丝径、中径比等结构参数在不同Re下对流场、阻力及传热性能的影响。结果表明,内插螺旋能够有效扰动和混合管内流体,使管内形成多个纵向旋涡的流体结构、增大管壁附近液体涡量,有利于强化传热。当Re相同时,管内平均流速v、Nu和综合换热性能PEC均随丝径增大而增大,随中径比减小而增大;随节距增大,3种参数均出现增大的趋势,节距大于20 mm后开始减小。管内流体的阻力f随丝径和节距增大而减小,随中径比增大而增大。综合比较,在较低Re时,节距p=20 mm、丝径e=1.6 mm、中径比D/d=0.75时综合传热效果最好。 相似文献
54.
CO2 stripping during fermentation is a possible way of increasing the production of ethanol in distilleries. Ethanol, water, and carbon dioxide are the main compounds in the exiting gas mixture. To date, few studies have proposed the use of absorption to recover ethanol from this mixture or have considered different absorbents for this purpose. This work evaluates different absorbent solutions used to recover ethanol vapor from CO2 gas. Glycols and glycerol can provide easier separation of ethanol than water, with lower distillation energy demand. A statistical experimental design was used to compare the mass transfers of ethanol from the gas phase to the liquid phase, using solutions of glycerol, ethylene glycol, and diethylene glycol. High concentrations of these substances did not favor the absorption of ethanol. The best results were achieved with 25% absorbent solutions, which offered better options than water for the recovery of ethanol from CO2 gas in absorption columns and could increase the productivity of first generation bioethanol production. 相似文献
55.
56.
《等离子体科学和技术》2020,22(9):94013
The highest deposition of power and temperature is always near the cusp of the ATON-type Hall thruster. This shows that when there are electrons gathering at the cusp, the distribution of heat load will be uniform, which will potentially damage the reliability. Therefore, we optimize the magnetic field near the anode. We changed the magnetic field characteristics in the near-anode region with an additional magnetic screen, and performed numerical simulation with particle-incell simulation. The simulation results show that the magnetic field of the thruster with the additional magnetic screen can alleviate the over-concentration of power deposition on the anode and reduce the power deposition in the anode by 20%, while ensuring that the overall magnetic field characteristics do not change significantly. 相似文献
57.
摘要:针对水下无线传感网络中运动节点定位精度低的问题,提出了一种新的基于双层修正无迹卡尔曼的水下节点定位算法(DLMUKF)。该算法利用下层无迹卡尔曼滤波算法对节点状态进行预测,根据各信标节点的测距传播时延对预测的节点状态进行修正。运用上层无迹卡尔曼滤波算法对修正后的状态进行新的预测与修正。仿真实验中,DLMUKF算法的平均定位误差约为传统多边定位算法的15%,约为基于无迹卡尔曼滤波(UKF)定位算法的16%,受节点运动时间与速度的影响最小。通过实验证明DLMUKF算法能更充分利用实际距离值,可以有效减小运动节点的定位误差。 .txt 相似文献
58.
59.
60.
Alireza HEIDARI Ali ESMAEEL NEZHAD Ahmad TAVAKOLI Navid REZAEI Foad H. GANDOMAN Mohammad Reza MIVEH Abdollah AHMADI Majid MALEKPOUR 《Frontiers in Energy》2020,14(3):510
Recently, renewable energy resources and their impacts have sparked a heated debate to resolve the Australian energy crisis. There are many projects launched throughout the country to improve network security and reliability. This paper aims to review the current status of different renewable energy resources along with their impacts on society and the environment. Besides, it provides for the first time the statistics of the documents published in the field of renewable energy in Australia. The statistics include information such as the rate of papers published, possible journals for finding relative paper, types of documents published, top authors, and the most prevalent keywords in the field of renewable energy in Australia. It will focus on solar, wind, biomass, geothermal and hydropower technologies and will investigate the social and environmental impacts of these technologies. 相似文献