全文获取类型
收费全文 | 5156篇 |
免费 | 464篇 |
国内免费 | 69篇 |
专业分类
电工技术 | 30篇 |
技术理论 | 2篇 |
综合类 | 101篇 |
化学工业 | 3598篇 |
金属工艺 | 99篇 |
机械仪表 | 12篇 |
建筑科学 | 14篇 |
矿业工程 | 14篇 |
能源动力 | 630篇 |
轻工业 | 27篇 |
水利工程 | 2篇 |
石油天然气 | 410篇 |
武器工业 | 4篇 |
无线电 | 175篇 |
一般工业技术 | 463篇 |
冶金工业 | 88篇 |
原子能技术 | 14篇 |
自动化技术 | 6篇 |
出版年
2024年 | 11篇 |
2023年 | 220篇 |
2022年 | 114篇 |
2021年 | 196篇 |
2020年 | 225篇 |
2019年 | 223篇 |
2018年 | 189篇 |
2017年 | 145篇 |
2016年 | 167篇 |
2015年 | 130篇 |
2014年 | 188篇 |
2013年 | 256篇 |
2012年 | 210篇 |
2011年 | 250篇 |
2010年 | 178篇 |
2009年 | 243篇 |
2008年 | 243篇 |
2007年 | 251篇 |
2006年 | 218篇 |
2005年 | 233篇 |
2004年 | 199篇 |
2003年 | 187篇 |
2002年 | 197篇 |
2001年 | 171篇 |
2000年 | 178篇 |
1999年 | 123篇 |
1998年 | 102篇 |
1997年 | 38篇 |
1996年 | 150篇 |
1995年 | 66篇 |
1994年 | 77篇 |
1993年 | 68篇 |
1992年 | 48篇 |
1991年 | 57篇 |
1990年 | 39篇 |
1989年 | 12篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 6篇 |
1985年 | 11篇 |
1984年 | 23篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1980年 | 1篇 |
1974年 | 1篇 |
1951年 | 2篇 |
排序方式: 共有5689条查询结果,搜索用时 15 毫秒
31.
《International Journal of Hydrogen Energy》2022,47(8):5337-5353
CO2 utilization through the activation of ethane, the second largest component of natural and shale gas, to produce syngas, has garnered significant attention in recent years. This work provides a comparative study of Ni catalysts supported on alumina, alumina modified with CaO and MgO, as well as alumina modified with La2O3 for the reaction of dry ethane reforming. The calcined, reduced and spent catalysts were characterized employing XRD, N2 physisorption, H2-TPR, CO2-TPD, TEM, XPS and TPO. The modification of the alumina support with alkaline earth oxides (MgO and CaO) and lanthanide oxides (La2O3), as promoters, is found to improve the dispersion of Ni, enhance the catalyst's basicity and metal-support interaction, as well as influence the nature of carbon deposition. The Ni catalyst supported on modified alumina with La2O3 exhibits a relatively stable syngas yield during 8 h of operation, while H2 and CO yields decrease substantially for Ni/Al2O3. 相似文献
32.
Zhiqiang Liu Jian Zhou Xiaomin Tang Fujian Liu Jiamin Yuan Guangchao Li Ling Huang Rajamani Krishna Kuan Huang Anmin Zheng 《American Institute of Chemical Engineers》2020,66(8):e16269
Zeolites have been widely used for the processes of adsorption, separation, and catalysis, which are strongly correlated with molecular diffusion. However, the correlation between pore dimension and diffusion properties has not been systematically investigated so far. In this work, the diffusion properties of alkanes in six zeolites with similar pore sizes but different pore dimension have been examined. It is found that the diffusion coefficients of alkanes in zeolites are 2–5 orders of magnitude smaller than that in gas phase. Moreover, the diffusion of alkanes inside zeolites is sensitive to the pore dimension, and can be differentiated by 1-D straight, 1-D tortuous, and 3-D intersecting channels, based on the derived quantitative correlation between the diffusion behavior and pore dimension. Our work may not only provide deep insights into the effects of pore dimension on diffusion, but also benefits for the future design and practical applications of zeolite catalysts. 相似文献
33.
Dolly Yadav Rajesh K. Yadav Abhishek Kumar No-Joong Park Jae Young Kim Jin-Ook Baeg 《应用聚合物科学杂志》2020,137(14):48536
C60-based polymeric systems have been constantly anticipated for sustainable solar energy conversion. Reported, herein is a C60 polymer film as visible light active photocatalyst for efficient and selective reduction of CO2 for the first time. The C60 polymer photocatalyst is synthesized via covalent coupling of C60 monomer units consisting of tetra substituted C60-pyrene conjugates through spacer groups. The synthesized C60 polymer photocatalyst possesses an extended network of well-defined repeating monomer units with good stability and visible light-induced photocatalytic activity. The enhanced visible light harvesting ability of C60 polymer photocatalyst reasonably yields it with higher catalytic ability than its monomer unit. The C60 polymer film photocatalyst upon coupling with the biocatalyst carries out highly selective visible light driven reduction of CO2 to HCOOH (239.46 μmol). The tandem way of incorporating C60 into visible light active polymeric films for continuous use may be highly rewarding for their extended photocatalytic activity for solar fuel production from CO2. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48536. 相似文献
34.
Elchin Jafariyeh-Yazdi Akram Tavakoli Farhang Abbasi Mohammad Javad Parnian Amin Heidari 《应用聚合物科学杂志》2020,137(15):48553
Bi-supported Ziegler–Natta catalysts (TiCl4/MCM-41/MgCl2 (ethoxide type)) were synthesized to improve the morphology and the properties of polyethylene. The morphology control is a crucial issue in polymerization process, while tailoring the properties of polymers is needed for specific applications. The catalysts were synthesized in different ratios of two supports with impregnation method. The polymerization process was carried out in atmospheric slurry reactor. The catalysts were characterized with scanning electron microscopy - energy dispersive X-ray spectroscopy (SEM–EDX), inductively coupled plasma, Fourier transform infrared spectrometry (FTIR), and Brunauer-Emmett-Teller (BET) methods. The polymers were analyzed with scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry, FTIR, and tensile-strength analyses. Ubbelohde viscometer and frequency sweep measurements showed that the synthesized polymers are ultra-high-molecular-weight polyethylene. Mechanical properties of polymers showed higher Young's modulus in samples containing MCM-41, having higher thermal stability supported by TGA analysis. SEM images of bi-supported catalyst showed a controlled spherical morphology with uniform size distribution. SEM analysis support that the polymers replicate their morphology from catalyst, improving their morphology comparing to MgCl2-supported catalyst. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48553. 相似文献
35.
36.
类似于锂/氟化碳(Li/CFx)电池,钠/氟化碳(Na/CFx)电池具有低廉的价格和较高的能量密度,是未来锂离子电池的理想替代选项。但是Na/CFx电池目前还存在着极化大和循环性能差等问题。为解决以上问题,在CFx阴极中加入催化剂成为改善电池电化学性能的一个重要途径。分别采用水热法和溶胶-凝胶法制备了催化剂材料Co3O4-TiO2和ZrO2,并对其进行了表征。分别将TiO2、Co3O4、Co3O4-TiO2以及ZrO2 4种催化剂材料按10%(质量比,下同)加入CFx正极中并组装成电池,然后对电池进行了恒流充放电、交流阻抗以及循环伏安等电化学性能测试。实验结果表明,加入4种催化剂后,Na/CFx电池的放电比容量得到明显提升。其中,ZrO2催化剂表现出最佳的催化性能。经过100次后循环后,含有ZrO2的Na/CFx电池的放电比容量为167.3 mAh·g-1,极大地改善了钠/氟化碳电池的循环性能。 相似文献
37.
Ammaru Ismaila Huanhao Chen Yan Shao Shaojun Xu Yilai Jiao Xueli Chen Xin Gao Xiaolei Fan 《中国化学工程学报》2020,28(9):2328-2336
Excess crude glycerol derived as a by-product from biodiesel industry prompts the need to valorise glycerol to value-added chemicals. In this context, catalytic steam reforming of glycerol (SRG) was proposed as a promising and sustainable alternative for producing renewable hydrogen (H2). Herein, the development of nickel (Ni) supported on ceria-modified mesoporous γ-alumina (γ-Al2O3) catalysts and their applications in catalytic SRG (at 550–750 °C, atmospheric pressure and weight hourly space velocity, WHSV, of 44,122 ml·g−1·h−1 (STP)) is presented. Properties of the developed catalysts were characterised using many techniques. The findings show that ceria modification improved Ni dispersion on γ-Al2O3 catalyst support with highly active small Ni particles, which led to a remarkable catalytic performance with the total glycerol conversion (ca. 99%), glycerol conversion into gaseous products (ca. 77%) and H2 yield (ca. 62%). The formation rate for H2 production (14.4 × 10−5 mol·s−1·g−1, TOF (H2) = 3412 s−1) was significantly improved with the Ni@12Ce-Al2O3 catalyst, representing nearly a 2-fold increase compared with that of the conventional Ni@Al2O3 catalyst. In addition, the developed catalyst also exhibited comparatively high stability (for 12 h) and coke resistance ability. 相似文献
38.
Teh C. Ho 《American Institute of Chemical Engineers》2020,66(6):e16930
Metal sulfide catalysts for ultra-deep hydrodesulfurization of diesel generally lose a fraction of their catalytically active sites during reactor startup. The underlying mechanisms are discussed. A laboratory diagnostic tool consisting of three probe molecules is developed for testing metal sulfide catalysts' start-of-run (SOR) activity maintenance. It is found that a significant fraction of the active sites on a commercial supported catalyst are deactivated permanently, but this is not the case with a bulk metal sulfide catalyst. The SOR deactivation of the bulk catalyst is completely reversible, while that of the supported catalyst is partially reversible. The diagnostic tool may provide a basis for developing a high-throughput approach for evaluating and enhancing catalyst SOR stability, thereby increasing plant productivity. 相似文献
39.
以浸渍法模拟碱金属中毒NH3-SCR催化剂过程,制备不同Na含量(质量分数)的铜基小孔分子筛Cu/SSZ-13和Cu/SAPO-34,对比研究了二者的碱金属中毒机理。结果表明,外引Na离子均可严重影响两种催化剂的NH3-SCR催化活性,造成催化剂的晶相结构坍塌,酸性量减少,活性物种减少。不同的是,Na引入量较低(<1.82%)时,Cu/SAPO-34比Cu/SSZ-13具有更强的Na离子耐受性,而当Na含量高于3.48%时,Cu/SAPO-34几乎完全丧失NH3-SCR催化活性。通过催化剂的结构表征(BET、XRD和SEM)和酸性位表征(DRIFTS、NH3-TPD和H2-TPR),研究表明随着Na中毒程度的加深,Cu/SSZ-13的结构破坏是渐变式的,而Cu/SAPO-34的结构破坏是突变式的;Na中毒的机理研究表明,酸性位的减少是Cu/SSZ-13的SCR活性下降的主导原因,结构坍塌是Cu/SAPO-34的SCR活性下降的主导原因。 相似文献
40.