全文获取类型
收费全文 | 115405篇 |
免费 | 8400篇 |
国内免费 | 4126篇 |
专业分类
电工技术 | 5031篇 |
技术理论 | 26篇 |
综合类 | 8283篇 |
化学工业 | 24315篇 |
金属工艺 | 4361篇 |
机械仪表 | 5515篇 |
建筑科学 | 11342篇 |
矿业工程 | 7870篇 |
能源动力 | 5135篇 |
轻工业 | 10819篇 |
水利工程 | 2188篇 |
石油天然气 | 5268篇 |
武器工业 | 2269篇 |
无线电 | 9518篇 |
一般工业技术 | 8895篇 |
冶金工业 | 5508篇 |
原子能技术 | 954篇 |
自动化技术 | 10634篇 |
出版年
2024年 | 390篇 |
2023年 | 1403篇 |
2022年 | 2789篇 |
2021年 | 3657篇 |
2020年 | 3606篇 |
2019年 | 2470篇 |
2018年 | 2144篇 |
2017年 | 3024篇 |
2016年 | 3366篇 |
2015年 | 3634篇 |
2014年 | 8323篇 |
2013年 | 6523篇 |
2012年 | 8854篇 |
2011年 | 8939篇 |
2010年 | 6886篇 |
2009年 | 6963篇 |
2008年 | 6237篇 |
2007年 | 7654篇 |
2006年 | 6898篇 |
2005年 | 6038篇 |
2004年 | 5139篇 |
2003年 | 4757篇 |
2002年 | 3791篇 |
2001年 | 3189篇 |
2000年 | 2532篇 |
1999年 | 2023篇 |
1998年 | 1456篇 |
1997年 | 1103篇 |
1996年 | 915篇 |
1995年 | 745篇 |
1994年 | 608篇 |
1993年 | 439篇 |
1992年 | 339篇 |
1991年 | 256篇 |
1990年 | 195篇 |
1989年 | 130篇 |
1988年 | 119篇 |
1987年 | 74篇 |
1986年 | 74篇 |
1985年 | 47篇 |
1984年 | 42篇 |
1983年 | 26篇 |
1982年 | 26篇 |
1981年 | 16篇 |
1980年 | 24篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1974年 | 4篇 |
1959年 | 5篇 |
1951年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
《Ceramics International》2021,47(23):32882-32890
Transition metals doping has been proved to be a feasible way for tuning the physical properties on the surface and bulk of nanomaterials and also for the good performance in decontamination of emerging pollutants. In this context, doped samples of zinc tin oxide or zinc stannate nanoparticles (ZTO NPs) by several transition metals were synthesized in order to enhance the optical absorbance with the aims of reducing the band gap and therefore ameliorated their photocatalytic activity. They were characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), diffuse reflectance spectroscopy, Raman spectroscopy and photoluminescence. The XRD patterns and the microscopic observations showed the formation of spherical nanoparticles with an average size of about 30 nm and highly pure ZTO phase with an inverse spinel structure. The Raman spectra were dominated by bands relatives to the F2g (2) and A1g symmetries modes of inverse spinel structure. The band gap Eg is estimated to be 3.75 eV for the undoped sample, and 3.67, 3.64, 3.78 and 3.21 eV, for 2% Fe, 2% Mg, 2% Gd, and 2% Mn doped ZTO samples, respectively.Furthermore, the undoped ZTO NPs have the intrinsic problem of recombination of photogenerated charge carriers. We have shown that the reduction of the band gap and oxygen vacancies resulting from the doping effect could be a useful tool for trapping and avoid the recombination of electrons coming from photosensitized rhodamine B (RhB) under visible light irradiation. Owing to the structural advantages and low band gap, 2% Mn doped ZTO NPs, with the kinetic rate constants k of 0.024 min−1, show enhanced performance for the elimination of RhB in aqueous solution compared to undoped and other doped ZTO NPs. 相似文献
32.
《International Journal of Hydrogen Energy》2022,47(49):21033-21043
Magnetron sputtered low-loading iridium-ruthenium thin films are investigated as catalysts for the Oxygen Evolution Reaction at the anode of the Proton Exchange Membrane Water Electrolyzer. Electrochemical performance of 50 nm thin catalysts (Ir pure, Ir–Ru 1:1, Ir–Ru 1:3, Ru pure) is tested in a Rotating Disk Electrode. Corresponding Tafel slopes are measured before and after the CV-based procedure to compare the activity and stability of prepared compounds. Calculated activities prior to the procedure confirm higher activity of ruthenium-containing catalysts (Ru pure > Ir–Ru 1:3 > Ir–Ru 1:1 > Ir pure). However, after the procedure a higher activity and less degradation of Ir–Ru 1:3 is observed, compared to Ir–Ru 1:1, i.e. the sample with a higher amount of unstable ruthenium performs better. This contradicts the expected behavior of the catalyst. The comprehensive chemical and structural analysis unravels that the stability of Ir–Ru 1:3 sample is connected to RuO2 chemical state and hcp structure. Obtained results are confirmed by measuring current densities in a single cell. 相似文献
33.
34.
Xian Suo Xili Cui Lifeng Yang Nan Xu Yuqi Huang Yi He Sheng Dai Huabin Xing 《Advanced materials (Deerfield Beach, Fla.)》2020,32(29):1907601
The design of highly stable and efficient porous materials is essential for developing breakthrough hydrocarbon separation methods based on physisorption to replace currently used energy-intensive distillation/absorption technologies. Efforts to develop advanced porous materials such as zeolites, coordination frameworks, and organic polymers have met with limited success. Here, a new class of ionic ultramicroporous polymers (IUPs) with high-density inorganic anions and narrowly distributed ultramicroporosity is reported, which are synthesized by a facile free-radical polymerization using branched and amphiphilic ionic compounds as reactive monomers. A covalent and ionic dual-crosslinking strategy is proposed to manipulate the pore structure of amorphous polymers at the ultramicroporous scale. The IUPs exhibit exceptional selectivity (286.1–474.4) for separating acetylene from ethylene along with high thermal and water stability, collaboratively demonstrated by gas adsorption isotherms and experimental breakthrough curves. Modeling studies unveil the specific binding sites for acetylene capture as well as the interconnected ultramicroporosity for size sieving. The porosity-engineering protocol used in this work can also be extended to the design of other ultramicroporous materials for the challenging separation of other key gas constituents. 相似文献
35.
36.
37.
SPEEK/cSMM membrane for simultaneous electricity generation and wastewater treatment in microbial fuel cell
下载免费PDF全文
![点击此处可从《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》网站下载免费的PDF全文](/ch/ext_images/free.gif)
38.
With the emergence of distributed ledger technology (DLT), numerous practitioners and researchers have proclaimed its beneficial impact on supply chain transactions in the future. However, the vast majority of DLT initiatives are discontinued after a short period. With the full potential of DLT laying far down the road, especially managers in supply chain management (SCM) seek for short-term cost-saving effects of DLT in order to achieve long-term benefits of DLT in the future. However, the extant research has bypassed grounding long-term as well as short-term effects of DLT on supply chain transaction with empirical data. We address this shortcoming, following an abductive research approach and combining empirical data from a multiple case study design with the corresponding literature. Our study reveals that the effects of DLT on supply chain transactions are two-sided. We found six effects of DLT solutions that have a cost-reducing or cost avoidance impact on supply chain transactions. In addition, we found two effects that change the power distribution between buyers and suppliers in transactions and a single effect that reduces the dependency of supply chain transactions on third parties. While cost-reducing and avoidance as well as dependency-reducing effects are positive effects, the change in power distribution might come with disadvantages. With these findings, the paper provides the first empirical evidence of the impact of DLT on supply chain transactions, which will enable managers to improve their assessment of DLT usage in supply chains. 相似文献
39.
伏彩萍 《有色金属(冶炼部分)》2020,(6):66-69
针对现有柠檬酸铋制备工艺合成时间长、能耗高、产品纯度不高等不足,介绍了一种常温下制备柠檬酸铋的新工艺。新工艺制备时间短,制备的柠檬酸铋产品质量好,合成过程产生的废水可循环利用,废气经碱液循环吸收可生产硝酸钠副产品。 相似文献
40.
现今国内的数字集群网络发展存在局限性、差异性,还远没有达到“网”状分布的程度,因此,共网数字集群发展空间巨大、前景广阔。通过列举共网数字集群系统在龙嘉国际机场和长春雷锋车队的成功应用案例,探讨了我国共网数字集群系统应用的可行性和必要性。 相似文献