全文获取类型
收费全文 | 68833篇 |
免费 | 6848篇 |
国内免费 | 5769篇 |
专业分类
电工技术 | 4893篇 |
技术理论 | 1篇 |
综合类 | 4386篇 |
化学工业 | 15593篇 |
金属工艺 | 16391篇 |
机械仪表 | 2449篇 |
建筑科学 | 2434篇 |
矿业工程 | 1002篇 |
能源动力 | 1998篇 |
轻工业 | 3118篇 |
水利工程 | 507篇 |
石油天然气 | 5291篇 |
武器工业 | 517篇 |
无线电 | 6797篇 |
一般工业技术 | 8961篇 |
冶金工业 | 3978篇 |
原子能技术 | 744篇 |
自动化技术 | 2390篇 |
出版年
2024年 | 335篇 |
2023年 | 1239篇 |
2022年 | 2017篇 |
2021年 | 2494篇 |
2020年 | 2532篇 |
2019年 | 2351篇 |
2018年 | 2076篇 |
2017年 | 2736篇 |
2016年 | 2700篇 |
2015年 | 2638篇 |
2014年 | 3763篇 |
2013年 | 4125篇 |
2012年 | 4600篇 |
2011年 | 4919篇 |
2010年 | 3620篇 |
2009年 | 4012篇 |
2008年 | 3343篇 |
2007年 | 4204篇 |
2006年 | 4042篇 |
2005年 | 3301篇 |
2004年 | 2969篇 |
2003年 | 2797篇 |
2002年 | 2357篇 |
2001年 | 2027篇 |
2000年 | 1783篇 |
1999年 | 1452篇 |
1998年 | 1192篇 |
1997年 | 1084篇 |
1996年 | 852篇 |
1995年 | 804篇 |
1994年 | 676篇 |
1993年 | 469篇 |
1992年 | 447篇 |
1991年 | 308篇 |
1990年 | 295篇 |
1989年 | 272篇 |
1988年 | 135篇 |
1987年 | 88篇 |
1986年 | 73篇 |
1985年 | 51篇 |
1984年 | 56篇 |
1983年 | 34篇 |
1982年 | 42篇 |
1981年 | 32篇 |
1980年 | 37篇 |
1979年 | 9篇 |
1978年 | 13篇 |
1975年 | 7篇 |
1959年 | 7篇 |
1951年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
3.
通过制备不同晶相结构〔单斜相(m-ZrO_2)、四方相(t-ZrO_2)和无定型(a-ZrO_2)〕ZrO_2载体,再通过沉积沉淀法制得Cu/m-ZrO_2、Cu/t-ZrO_2和Cu/a-ZrO_2催化剂,分别用于催化二乙醇胺脱氢合成亚氨基二乙酸反应。采用XRD、氮气物理吸附脱附、XPS、H_2-TPR、CO_2-TPD对催化剂的结构进行了表征。结果表明,Cu/m-ZrO_2催化剂界面更加有利于Cu~+/Cu~0稳定存在,具有更多的碱性位点,且抗氧化性较好。在二乙醇胺脱氢反应中,Cu/m-ZrO_2催化剂性能最好,反应时间为2.5 h,亚氨基二乙酸收率为97.64%。 相似文献
4.
5.
6.
《Displays》2015
Modern liquid crystal displays (LCDs) require novel technologies, such as new alignment methods to eliminate alignment layers, fast response and long operation time. To this end, we report an overview of recent efforts in LCD technologies devoted to realize more display modes having no alignment layer, faster switching time and low battery consumption. In particular, we overview recent advances on the liquid crystals (LCs) alignment for display applications, which includes superfine nanostructures, polymeric microchannels and polymer stabilized LCs. Furthermore, we analyze the main optical and electro-optical properties of new generation LCDs displays addressing a particular attention to LCs blue phase hosting gold nanoparticles. Moreover, we focus on the progress of electrofluidic displays, which demonstrates characteristics that are similar to LCDs, with attention on various pixel designs, operation principles and possible future trends of the technology. 相似文献
7.
《Food Control》2015
In this work a multicommuted flow system employing copper–4,4′- dipyridyl coordination compound as the solid-phase reagent for the spectrophotometric determination of reducing sugar was developed. The coordination compound was synthesized through a reaction of the 4,4′-dipyridyl and copper (II) nitrate, under hydrothermal conditions. The complex was characterized by infrared spectroscopy (FTIR), power X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and thermogravimetric analysis (TGA). Based on the characterization, a multicommuted spectrophotometric procedure for the determination of reducing sugar using copper (II) complex as solid reagent is proposed. The proposed method was based on the redox reaction between a monosaccharide, such as fructose and glucose (reducing sugar) and Cu(II). This reaction, mediated in an alkaline medium, produces a yellow compound that can be determined by absorption electronic spectroscopy (λABS = 420 nm). Under optimum experimental conditions, a linear response ranging from 1.0 to 20.0 g L−1 (R = 0.9978 and n = 5), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.23 and 0.75 g L−1, respectively, a standard deviation relative of 4.7% (n = 7), for a reference solution of 10.0 g L−1 reducing sugar, and a sampling rate of 75 determinations per hour were achieved. The proposed system was applied to the determination of reducing sugars in coconut water and juices. The analysis of ten samples and the application of the t-test to the results found, and those obtained using reference procedures (AOAC), provided no significant differences at a 95% confidence level. This system enabled the analysis of reducing sugar with ease and simplicity, providing a significant economy of the solid reagent (600 μg per determination) and reducing effluent generation. 相似文献
8.
Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI ... 相似文献
9.
To improve the electrochemical properties of rare-earth–Mg–Ni-based hydrogen storage alloys, the effects of stoichiometry and Cu-substitution on the phase structure and thermodynamic properties of the ... 相似文献
10.