全文获取类型
收费全文 | 2015篇 |
免费 | 116篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 30篇 |
综合类 | 5篇 |
化学工业 | 525篇 |
金属工艺 | 30篇 |
机械仪表 | 78篇 |
建筑科学 | 56篇 |
矿业工程 | 4篇 |
能源动力 | 181篇 |
轻工业 | 192篇 |
水利工程 | 20篇 |
石油天然气 | 33篇 |
无线电 | 192篇 |
一般工业技术 | 404篇 |
冶金工业 | 51篇 |
原子能技术 | 18篇 |
自动化技术 | 325篇 |
出版年
2024年 | 10篇 |
2023年 | 73篇 |
2022年 | 135篇 |
2021年 | 158篇 |
2020年 | 113篇 |
2019年 | 113篇 |
2018年 | 131篇 |
2017年 | 107篇 |
2016年 | 138篇 |
2015年 | 82篇 |
2014年 | 134篇 |
2013年 | 190篇 |
2012年 | 117篇 |
2011年 | 114篇 |
2010年 | 92篇 |
2009年 | 84篇 |
2008年 | 60篇 |
2007年 | 44篇 |
2006年 | 40篇 |
2005年 | 23篇 |
2004年 | 20篇 |
2003年 | 20篇 |
2002年 | 17篇 |
2001年 | 16篇 |
2000年 | 6篇 |
1999年 | 13篇 |
1998年 | 17篇 |
1997年 | 6篇 |
1996年 | 14篇 |
1995年 | 5篇 |
1994年 | 9篇 |
1993年 | 6篇 |
1992年 | 6篇 |
1991年 | 4篇 |
1990年 | 4篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有2144条查询结果,搜索用时 15 毫秒
31.
Na Yang Chun Tang Kunyang Wang Gu Du Abdullah M. Asiri Xuping Sun 《Nano Research》2016,9(11):3346-3354
Developing efficient water-splitting electrocatalysts, particularly for the anodic oxygen evolution reaction (OER), is an important challenge in energy conversion technologies. In this study, we report the development of iron-doped nickel disulfide nanoarray on Ti mesh (Fe0.1-NiS2 NA/Ti) via the sulfidation of its nickel–iron-layered double hydroxide precursor (NiFe-LDH NA/Ti). As a three-dimensional OER anode, Fe0.1-NiS2 NA/Ti exhibits remarkable activity and stability in 1.0 M KOH, with the requirement of a low overpotential of 231 mV to achieve 100 mA·cm?2. In addition, it exhibits excellent activity and durability in 30 wt.% KOH. Notably, this electrode is also efficient for the cathodic hydrogen evolution reaction under alkaline conditions. 相似文献
32.
Abdullah Saad Abdullah Ibrahim El Tantawy El Sayed Abdel Moneim A. El-Torgoman Abul Kalam S. Wageh Maher A. Kamel 《International journal of molecular sciences》2022,23(10)
Background: Silymarin (SIL) has long been utilized to treat a variety of liver illnesses, but due to its poor water solubility and low membrane permeability, it has a low oral bioavailability, limiting its therapeutic potential. Aim: Design and evaluate hepatic-targeted delivery of safe biocompatible formulated SIL-loaded chitosan nanoparticles (SCNPs) to enhance SIL’s anti-fibrotic effectiveness in rats with CCl4-induced liver fibrosis. Methods: The SCNPs and chitosan nanoparticles (CNPs) were prepared by ionotropic gelation technique and are characterized by physicochemical parameters such as particle size, morphology, zeta potential, and in vitro release studies. The therapeutic efficacy of successfully formulated SCNPs and CNPs were subjected to in vivo evaluation studies. Rats were daily administered SIL, SCNPs, and CNPs orally for 30 days. Results: The in vivo study revealed that the synthesized SCNPs demonstrated a significant antifibrotic therapeutic action against CCl4-induced hepatic injury in rats when compared to treated groups of SIL and CNPs. SCNP-treated rats had a healthy body weight, with normal values for liver weight and liver index, as well as significant improvements in liver functions, inflammatory indicators, antioxidant pathway activation, and lipid peroxidation reduction. The antifibrotic activities of SCNPs were mediated by suppressing the expression of the main fibrosis mediators TGFβR1, COL3A1, and TGFβR2 by boosting the hepatic expression of protective miRNAs; miR-22, miR-29c, and miR-219a, respectively. The anti-fibrotic effects of SCNPs were supported by histopathology and immunohistochemistry (IHC) study. Conclusions: According to the above results, SCNPs might be the best suitable carrier to target liver cells in the treatment of liver fibrosis. 相似文献
33.
Polat Cevik Ibrahim Kocaman Abdullah S. Akgul Barbaros Akca 《Journal of Intelligent and Robotic Systems》2013,70(1-4):595-608
At the last two decades, according to UAVs concepts and technological advances, there have been lots of unimagined improvements. Nowadays there are serious works and researches about the usage of UAVs in military operations at electronic warfare (EW) missions. But most of the work on UAV platforms is based upon the advantages of a single, big, expensive, and non-expendable platform. In this study, to get rid off the disadvantages of a stand alone platform a new concept is developed consisting of multiple UAVs with smaller dimensions, at a cheaper price and a wider coverage. According to clarify the study, firstly the EW and RADAR systems and then the swarm UAV concepts are explained. In this manner the current and previous works are pointed out and then the use of the swarm UAVs for EA in military operations is stated. Objectively, the swarm UAV concept’s advantages and some outstanding challenges to the intra-theater space have been put forward regarding the information mentioned above. As a result it is considered that the swarm UAV systems will be tasked important EW missions in the future operation theatres, as soon as the technical handicaps are solved. 相似文献
34.
Rahim Airee Afiq Abd Abdullah Shahrum Singh Salvinder Singh Karam Nuawi Mohammad Zaki 《Journal of Mechanical Science and Technology》2020,34(1):137-142
Journal of Mechanical Science and Technology - This paper discusses the determination of the optimum decomposition level by using the discrete wavelet transform (DWT) method for an automobile... 相似文献
35.
确保粮食安全和环境可持续发展的水土资源利用 总被引:1,自引:0,他引:1
主要讨论灌溉农业所面临的挑战.随着人均可用水量的不断下降,灌溉农业必须提高水资源利用效率,同时进一步采用有利于环境的经营和管理方式.灌溉界面临的压力是如何通过提高作物产量和用水效率来实现生产率的最大化.今后的发展方向是以更加高效率、有成效的方式利用水资源,而实现从"提高每滴水的粮食产量"向"少用水,多产粮"的转变,则有助于该目标的实现.为了尽可能减小外在因素的影响,将来的努力方向是在全面性和整体性上下工夫. 相似文献
36.
37.
该研究探讨了桑根来源的三种二苯乙烯化合物(氧化白藜芦醇,白藜芦醇和白藜芦醇苷)的富集提取工艺,并对提取物的抗氧化活性和酪氨酸酶抑制作用进行了研究。结果表明,通过单因素试验和响应面试验确定富集二苯乙烯化合物的最佳条件为:提取时间1h,料液比1:20,乙醇浓度90%,在此条件下,桑根中氧化白藜芦醇,白藜芦醇和白藜芦醇苷的含量分别为2923.59μg/g,32.45μg/g和3.15μg/g,富含三种二苯乙烯化合物提取物的得率为10.23%。并且,提取物表现出极强的DPPH自由基清除能力(IC50=0.063 mg/mL)和ABTS自由基清除能力(IC50=0.008 mg/mL)。此外,提取物比熊果苷表现出更强的酪氨酸酶抑制活性,其酪氨酸酶抑制率IC50(2.514μg/m L)仅约为熊果苷(IC50=15.551μg/m L)的16%。综上,高活性的二苯乙烯化合物提取物具有天然抗氧化剂和美白剂的潜力,在食品、美容与医药领域有很大的应用价值。桑根可作为二苯乙烯化合物的重要天然来源,是值得被开发利用的抗氧... 相似文献
38.
Cobalt-doped (Zn,Ni)(O,S) or Co-(Zn,Ni)(O,S) was facilely synthesized at low temperature below 100 °C with different cobalt precursor contents for photocatalytic hydrogen production. The X-ray pattern and elemental mapping proved that cobalt was successfully doped into zinc sites in the (Zn,Ni)(O,S) host lattice. We found the incorporation with a small amount of cobalt into (ZnNi)(O,S) enhanced its photo activity for hydrogen production. The best hydrogen production was achieved for 2.5% Co-(ZnNi)(O,S) with a rate of 8,527 μmol/g·h during a span of 5 h in a 20% (v/v) ethanol/water solution. Based on the results of optical characterizations, the enhancement of hydrogen production was caused by the slow electron-hole recombination and the low charge transfer resistance. A different photocatalytic kinetic mechanism for hydrogen generation from the conventional one with the simultaneous formation of hydrogen and oxygen gases is proposed, based upon the activated surface oxygen anion to initiate or trigger the key reaction of oxidation for water splitting to proceed. Our strategy in preparing catalyst at low process temperature and in doping to activate catalyst is for weakening the lattice oxygen bonding on the catalyst surface in order to firstly initiate the oxidation reaction and the formation of oxygen vacancies. These freshly formed oxygen vacancies play a critical role to trap the water and weaken its OH bonding to form hydrogen gas through the reduction reaction. 相似文献
39.
40.
Alafara A. Baba Daud T. Olaoluwa Ayo F. Balogun Abdullah S. Ibrahim Fausat T. Olasinde Folahan A. Adekola 《Canadian Metallurgical Quarterly》2019,58(2):232-240
This study examines the extraction of beryllium and aluminium from a Nigerian beryl ore using Cyanex®272 in kerosene from an aqueous sulphate pregnant solution. Parameters such as extractant concentration and equilibrium pH that dictates the extraction yield were studied. Under the following conditions: temperature 27?±?2°C, phase ratio 1?1, about 45.50 and 46.76% of beryllium and aluminium were extracted by 0.15?mol?L?1 Cyanex®272 concentration within 30?min. However, the extraction yield of beryllium and aluminium was increased to 91.68% and 97.89% at equilibrium pH of 3 and 4, respectively, for beryllium and aluminium at 27?±?2°C. A 0.05?mol?L?1 H2SO4 solution was found to be adequate for the stripping of about 99.00% Be and 95.40% Al from the loaded organic phase. The pure solutions containing metal ions were accordingly beneficiated to obtain beryllium and aluminium compounds of industrial values. 相似文献