全文获取类型
收费全文 | 1900篇 |
免费 | 154篇 |
国内免费 | 53篇 |
专业分类
电工技术 | 16篇 |
综合类 | 99篇 |
化学工业 | 895篇 |
金属工艺 | 39篇 |
机械仪表 | 20篇 |
建筑科学 | 54篇 |
矿业工程 | 22篇 |
能源动力 | 24篇 |
轻工业 | 644篇 |
水利工程 | 7篇 |
石油天然气 | 40篇 |
武器工业 | 10篇 |
无线电 | 40篇 |
一般工业技术 | 137篇 |
冶金工业 | 19篇 |
原子能技术 | 30篇 |
自动化技术 | 11篇 |
出版年
2024年 | 8篇 |
2023年 | 33篇 |
2022年 | 47篇 |
2021年 | 63篇 |
2020年 | 60篇 |
2019年 | 72篇 |
2018年 | 50篇 |
2017年 | 60篇 |
2016年 | 74篇 |
2015年 | 81篇 |
2014年 | 93篇 |
2013年 | 132篇 |
2012年 | 148篇 |
2011年 | 147篇 |
2010年 | 98篇 |
2009年 | 99篇 |
2008年 | 101篇 |
2007年 | 123篇 |
2006年 | 109篇 |
2005年 | 82篇 |
2004年 | 61篇 |
2003年 | 53篇 |
2002年 | 28篇 |
2001年 | 51篇 |
2000年 | 30篇 |
1999年 | 33篇 |
1998年 | 26篇 |
1997年 | 21篇 |
1996年 | 13篇 |
1995年 | 20篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 13篇 |
1991年 | 13篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1987年 | 1篇 |
1985年 | 5篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1979年 | 2篇 |
1951年 | 1篇 |
排序方式: 共有2107条查询结果,搜索用时 0 毫秒
81.
An experimental comparison of a graphite electrode and a gas diffusion electrode for the cathodic production of hydrogen peroxide 总被引:2,自引:0,他引:2
Anna Da?Pozzo Luca Di?Palma Carlo?Merli Elisabetta?PetrucciEmail author 《Journal of Applied Electrochemistry》2005,35(4):413-419
This work studies the production of hydrogen peroxide through the cathodic reduction of oxygen in acidic medium, by comparing the results obtained using a commercial graphite and a gas diffusion electrode. A low pH was required to allow the application of hydrogen peroxide generation to an electro-Fenton process. The influence of applied potential and the gas flow composition were investigated. The gas diffusion electrode demonstrates a higher selectivity for hydrogen peroxide production, without significantly compromising the iron regeneration, thus making its successful application to a cathodic Fenton-like treatment, possible. Unlike the graphite cathode, the gas diffusion cathode also proved to be effective in the air flow. 相似文献
82.
依据大量文献,综述了近几年来从工业烟气中脱除有害气体SO_2和NO_(?)的新技术。着重论述了国外在高能电子束辐射技术和脉冲流光电晕放电技术方面的新进展。通过比较单位能耗的脱除率,指出了电晕放电技术的优越性。并概述了近几年来作者参与脉冲电晕放电脱硫脱硝的研究情况,提出了进一步研究此课题的建议。 相似文献
83.
84.
利用亚硫酸钠和乙二醛对玉米秸秆木质素进行去甲基化/羟乙基化复合改性,以提高木质素的羟基含量和反应活性。通过FT-IR、TG、DSC以及乙酰化滴定等技术研究了木质素复合改性效果。结果表明:经过去甲基化/羟乙基化复合改性后的玉米秸秆木质素具有优异的活性,其总羟基质量分数较原料木质素提升了88.33%,酚羟基提升了14.70%,反应活性得到明显增强。FT-IR表征发现:复合改性从多方面提升了木质素的羟基含量,对羟基含量的增加有着较为显著的效果。热重和DSC表征发现:复合改性木质素(G-DL)相较于原料木质素降解得更加彻底,其放热峰出现在77℃,放热量达459.82 J/g,反应活性较去甲基化木质素(DL)和原料木质素更高。 相似文献
85.
Ajibola CF Fashakin JB Fagbemi TN Aluko RE 《International journal of molecular sciences》2011,12(10):6685-6702
Enzymatic hydrolysate of African yam bean seed protein isolate was prepared by treatment with alcalase. The hydrolysate was further fractionated into peptide sizes of <1, 1-3, 3-5 and 5-10 kDa using membrane ultrafiltration. The protein hydrolysate (APH) and its membrane ultrafiltration fractions were assayed for in vitro antioxidant activities. The <1 kDa peptides exhibited significantly better (p < 0.05) ferric reducing power, diphenyl-1-picryhydradzyl (DPPH) and hydroxyl radical scavenging activities when compared to peptide fractions of higher molecular weights. The high activity of <1 kDa peptides in these antioxidant assay systems may be related to the high levels of total hydrophobic and aromatic amino acids. In comparison to glutathione (GSH), the APH and its membrane fractions had significantly higher (p < 0.05) ability to chelate metal ions. In contrast, GSH had significantly greater (p < 0.05) ferric reducing power and free radical scavenging activities than APH and its membrane fractions. The APH and its membrane fractions effectively inhibited lipid peroxidation, results that were concentration dependent. The activity of APH and its membrane fractions against linoleic acid oxidation was higher when compared to that of GSH but lower than that of butylated hydroxyl toluene (BHT). The results show potential use of APH and its membrane fractions as antioxidants in the management of oxidative stress-related metabolic disorders and in the prevention of lipid oxidation in food products. 相似文献
86.
J. Prasad RaoKurt E. Geckeler 《Progress in Polymer Science》2011,36(7):887-913
87.
Igbinosa OO Igbinosa IH Chigor VN Uzunuigbe OE Oyedemi SO Odjadjare EE Okoh AI Igbinosa EO 《International journal of molecular sciences》2011,12(5):2958-2971
We assessed the polyphenolic contents and antioxidant potential of the aqueous, ethanol and methanol stem bark extracts of Jatropha curcas. The total phenol, flavonoids, flavonols and proanthocyanidin contents of the extracts were evaluated to determine their effect on the antioxidant property of this plant, using standard phytochemical methods. The antioxidant and free radical scavenging activity of ethanol, methanol and aqueous extracts of the plant were also assessed against 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), ferric reducing, nitric oxide (NO), superoxide anion, (O(2) (-)) and hydrogen peroxide (H(2)O(2)) using spectroscopic methods and results were compared with that of butylated hydroxyl toluene (BHT) and ascorbic acid as standards. The concentrations of different classes of phenolic compounds were higher in methanol and ethanol extracts compared to aqueous extracts. There was correlation between total phenol, total flavonoids, total flavonol and total proanthocyanidins (r = 0.996, 0.978, 0.908, and 0.985) respectively. There was correlations between the amount of phenolic compounds and percentage inhibition of DPPH radicals scavenging activity of the extract (r = 0.98). Findings from the present study indicated that J. curcas is a potential source of natural antioxidants and may be a good candidate for pharmaceutical plant based products. 相似文献
88.
89.
针对水体中存在的难降解农药莠去津(ATZ)污染问题,提出零价铁活化过氧单硫酸盐(PMS/Fe0)降解水中的ATZ,研究不同工艺参数(溶液pH、PMS投加量、Fe0投加量、ATZ初始浓度)条件下ATZ的降解动力学。采用硝基苯(NB)和ATZ竞争实验的方法,原位鉴定PMS/Fe0体系的自由基种类,并进一步基于稳态假设定量推导得到自由基产率比的公式。最后,研究了模拟地下水条件下PMS/Fe0对ATZ的降解规律。结果表明:ATZ降解的假一级速率常数(kobs),随pH的增加而降低,随ATZ初始浓度的增加而降低,随Fe0投量增加而增加,随PMS的投量先增加后降低,在PMS投量为25μmol/L时最大。NB和ATZ的竞争实验结果表明,PMS/Fe0体系中的活性物种为硫酸根自由基(SO-4·)和羟基自由基(·OH),且两种自由基的产率比为10.5∶1。在模拟地下水条件下,Fe0和PM... 相似文献
90.
采用近红外光谱法同时测定了端羟基聚丁二烯(HTPB)的数均相对分子质量、黏度和羟值,与传统方法相比较,可得到满意的结果。该法可在HTPB工业生产中作为一种简捷快速的测定方法使用。 相似文献