全文获取类型
收费全文 | 27024篇 |
免费 | 3958篇 |
国内免费 | 1853篇 |
专业分类
电工技术 | 16580篇 |
综合类 | 1607篇 |
化学工业 | 1357篇 |
金属工艺 | 963篇 |
机械仪表 | 888篇 |
建筑科学 | 384篇 |
矿业工程 | 549篇 |
能源动力 | 1317篇 |
轻工业 | 182篇 |
水利工程 | 270篇 |
石油天然气 | 149篇 |
武器工业 | 76篇 |
无线电 | 4572篇 |
一般工业技术 | 1520篇 |
冶金工业 | 788篇 |
原子能技术 | 329篇 |
自动化技术 | 1304篇 |
出版年
2024年 | 117篇 |
2023年 | 441篇 |
2022年 | 692篇 |
2021年 | 853篇 |
2020年 | 996篇 |
2019年 | 804篇 |
2018年 | 757篇 |
2017年 | 1114篇 |
2016年 | 1174篇 |
2015年 | 1392篇 |
2014年 | 1909篇 |
2013年 | 1609篇 |
2012年 | 2312篇 |
2011年 | 2448篇 |
2010年 | 1779篇 |
2009年 | 1839篇 |
2008年 | 1770篇 |
2007年 | 2033篇 |
2006年 | 1814篇 |
2005年 | 1395篇 |
2004年 | 1068篇 |
2003年 | 927篇 |
2002年 | 723篇 |
2001年 | 669篇 |
2000年 | 531篇 |
1999年 | 368篇 |
1998年 | 231篇 |
1997年 | 201篇 |
1996年 | 179篇 |
1995年 | 136篇 |
1994年 | 125篇 |
1993年 | 119篇 |
1992年 | 83篇 |
1991年 | 50篇 |
1990年 | 43篇 |
1989年 | 36篇 |
1988年 | 30篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 7篇 |
1984年 | 13篇 |
1983年 | 8篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1975年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
991.
992.
在10μF钽电容放电激励下,对两种阻值相当质量不同的半导体桥(SCB)和细化的发火药剂斯蒂芬酸铅(LTNR)和叠氮化铅(PbN6)所组成的发火件进行了实验研究,根据发火件的电特性变化和发火现象发现半导体桥存在电热发火、电爆发火和等离子体发火三种情况,测试了SCB/LTNR和SCB/PbN6发火件的50%发火电压和发火时间。结果表明半导体桥的发火电压阈值不仅与发火药剂有关,还与半导体桥换能元有关,所以半导体桥的设计存在最佳质量,通过对比得知LTNR比PbN6感度高,PbN6比LTNR的燃速高。 相似文献
993.
994.
Zhenyu Zhu Zihan Sun Shudong Zhou Shang Xu Xiaoxiao Li Weijun Li Lin Wang Weiyou Yang Fengmei Gao Shanliang Chen 《Journal of the American Ceramic Society》2022,105(2):806-814
Low turn-on field (Eto) and stable electron emission are two of key parameters for reliable application of field emission (FE) cathodes. In the present work, we developed a novel high-performance integrated field emission cathode based on well-aligned SiC nanocone arrays via an electrochemical etching approach. The etched SiC nanocone emitters and the underlying remaining SiC wafer are designed into a single-crystalline integrated architecture without interfaces, which favors cathodes with a sturdy configuration to resist Joule heat during long period electron emission process and structural failure caused by the existed strong electrostatic forces. Accordingly, the Eto of the integrated SiC cathode is reduced to 0.32 V/μm, which is the lowest value among all the previously reported SiC nanostructured emitters. In addition, the integrated cathode presented superior stability with an electron emission fluctuation of 3.3% over 10 h. This work provides a new perspective for designing and fabricating advanced FE cathodes for further promising applications in harsh working conditions with high performance. 相似文献
995.
996.
997.
利用有限元法建立了三维锂电解槽电热场仿真模型,考察了电解槽结构参数对电热场的影响。结果表明,缩短阴阳极间距(ACD),增加阳极半径(Ar)、阴极厚度(Ct)及阴极高度(Ch)均可以在保持能量平衡的前提下提高电解槽的电流强度。对上述参数进行无量纲化研究,得到了方程:CI=30000×(ACD/40)~(-0.24519)×(Ar/150)~(0.79291)×(Ct/225)~(0.09835)×(Ch/700)~(0.37953),对于电解槽的放大设计,可以根据上述方程,不对电解槽进行复杂的建模计算,进而节省资源,提高效率。 相似文献
998.
Michel Piliougine David Elizondo Llanos Mora‐Lpez Mariano Sidrach‐de‐Cardona 《Progress in Photovoltaics: Research and Applications》2015,23(4):513-523
A neural network for modelling photovoltaic modules using angle of incidence and clearness index is proposed. Engineers require methods to estimate the output of a photovoltaic plant depending on meteorological conditions. Therefore, models for the grid inverter and the generator must be provided, and their outputs must be combined. The connection between both models is related to the maximum power point of the generator and how it is tracked by the inverter. That maximum power point under specific conditions of irradiance and module temperature is determined by the I–V curve of the module, which must be simulated under those conditions. Algebraic procedures were used to simulate the I–V curve. Recently, neural networks have been used for the same purpose. Previous methods only take into account the irradiance and the module temperature. The model proposed is based on neural networks, and it uses not only the irradiance and the module temperature but also the angle of incidence and the instantaneous clearness index as additional inputs. The normalised clearness replaces the standard clearness index because it allows the removal of the hourly trend found in this last index. This new model improves the results obtained with previous ones as it can distinguish amongst samples with the same solar irradiance and temperature values but with different angle of incidence and instantaneous clearness index. Results show that this model could be used to improve the accuracy of the tools used to forecast the output of photovoltaic plants. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
999.
Francesco Malara Alessandro Cannavale Giuseppe Gigli 《Progress in Photovoltaics: Research and Applications》2015,23(3):290-301
In the last few years, a new class of smart multifunctional photoelectrochemical devices has been attracting the interest of several academic institutions and industrial companies: photovoltachromic cells, combining the features of photoelectrochromic cells with those of dye‐sensitized solar cells. Here, we report the results of a detailed electrochemical analysis aiming at investigating the electrochemical behavior of these complex photoelectrochemical devices. In particular, we have been focused on the effect of Li+ ions displacement during the coloration of the electrochromic tungsten oxide on the performances of the photovoltaic unit. As we had previously observed striking differences between the performances of the barely photovoltaic mode (with the tungsten oxide in the bleached state) and the photovoltachromic mode (with the tungsten oxide in the colored state), we thus attempted to provide a reasonable physical interpretation to the observed phenomena. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
1000.