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61.
62.
钯系催化剂的氨中毒研究 总被引:5,自引:0,他引:5
考察了CO常压气相偶联合成草酸酯反应体系中在不同氨含量下P\r\nd系催化剂活性随反应时间的变化.结果表明,随着氨含量的增加,催\r\n化剂活性降低的速率加快,氨含量不超过0.54%时,仅引起催化剂活\r\n性下降,但不会造成催化剂完全失活;当氨含量达1.16%时,催化剂\r\n活性随反应时间迅速下降,直至完全失活.同时,观测了催化剂氨中毒\r\n的不可逆性.利用XPS和TEM表征手段探讨了Pd系催化剂氨中毒机理,并\r\n分析了在工业生产条件下催化剂氨中毒不可逆性的原因. 相似文献
63.
以陶瓷为骨架,用溶胶凝胶法和浸渍法制备了V2O5-MoO3/ TiO2催化剂,并用SiO2进行改性。采用浸渍法模拟碱K中毒,研究了SiO2改性前后催化剂中毒脱硝效率的变化,并通过BET、H2-TPR、NH3-TPD等技术手段对催化剂进行了表征。结果表明,加入SiO2后,催化剂的比表面积明显提高。SiO2改性后新鲜催化剂还原温度向低温方向迁移10 ℃左右,氧化还原能力得到了提高,其表面酸强度和酸量也得到较大的提高。反应评价结果表明,SiO2改性可以提高催化剂抗碱中毒的性能。 相似文献
64.
65.
Pascal Granger Hermann W. Siaka Shubhangi B. Umbarkar 《Chemical record (New York, N.Y.)》2019,19(9):1813-1828
This paper reports a short review on the impact of poisoning effects and thermal aging on the reactivity of surface vanadate species on benchmark V2O5?WO3/TiO2 Selective‐Catalytic‐Reduction catalysts. A renewed interest of this SCR technology is related to its diversification notably as after‐treatment systems to treat the exhaust from Diesel engines with higher running temperature especially when SCR catalysts are coated on Diesel Particulates Filters. Particular attention is also paid to poisoning effects in conjunction with the progressive replacement of fossil fuels by bio‐fuels containing alkaline contaminants which drastically deactivate the catalyst through neutralization of strong acid sites. Most of the investigations show that better insight into the mechanisms of poisoning and aging processes is needed especially to understand the relative sensibility of various vanadate species. This could provide original guidelines to catalyst preparation and or the developments of more stable bulk systems as exemplified. 相似文献
66.
从铅中毒发铅诊断标准、发铅诊断试验及发铅诊断临床应用3个方面论述了发铅检测法在铅中毒诊断、筛查和监督中的实际应用问题。根据临床经验和发铅-血铅比值确定了居民发铅正常值上限及铅中毒发铅诊断分级标准;即使以血铅测定值为"金标准",诊断试验表明,发铅测定在铅中毒诊断中仍有实际应用价值;发铅检测法自上世纪60年代以来一直沿用至今,绝大多数研究者认为,发铅测定是诊断、筛查铅中毒和监督环境铅污染最简单、有效的工具。 相似文献
67.
Manuel F. Gomez Luis A. Arrúa Maria C. Abello 《Reaction Kinetics and Catalysis Letters》2001,73(1):143-149
The surface of an unpoisoned and sulfur-poisoned industrial iron ammonia catalysts is investigated by K, K+ thermal desorption. The K+ desorption energy increases while the K energy decreases upon poisoning. Presence of sulfur also suppresses the potassium
desorption in electronically excited states.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
68.
杞枣口服液治疗儿童铅中毒的疗效观察 总被引:2,自引:0,他引:2
观察了应用杞枣口服液治疗儿童铅中毒的疗效。选择128例年龄2~14岁,血铅100~199μg/L的儿童,随机分为治疗组68例,对照组60例,于治疗前后观察临床症状改善、有益元素变化及血铅变化情况。结果表明,治疗组明显优于对照组,P〈0.05。提示杞枣口服液不仅能降血铅,还能改善临床症状,补充有益元素,无不良反应。 相似文献
69.
F. M. Bautista J. M. Campelo A. Garcia D. Luna J. M. Marinas A. A. Romero M. R. Urbano 《Reaction Kinetics and Catalysis Letters》1998,64(1):41-48
The skeletal isomerization of 3,3-dimethyl-1-butene over AlPO4 (Al/P=1), CrPO4 (Cr/P=1), and CrPO4−AlPO4 (CrAlP, 5–10 wt.% AlPO4) catalysts is a first order reaction. Catalytic performance is affected by the precipitation agent. CrPO4 catalysts obtained in propylene oxide-aqueous ammonia showed the highest activity. Moreover, the incorporation of AlPO4 to CrPO4 developed CrAlP catalysts that exhibited increased activity, irrespective of the precipitation method, as compared with both
AlPO4 and CrPO4 catalysts. Besides, CrAlP catalysts prepared in propylene oxide-aqueous ammonia were the more active ones. 相似文献
70.
Díaz Sierra M Furey A Hamilton B Lehane M James KJ 《Journal of mass spectrometry : JMS》2003,38(11):1178-1186
Collision-induced dissociation (CID) mass spectra were generated for azaspiracids using electrospray ionisation (ESI), and hydrogen/deuterium (H/D) exchange was used to ascertain the number and type of replaceable hydrogens in the three predominant azaspiracid toxins. H/D exchange was conveniently achieved using deuterated solvents for liquid chromatography (LC). Using ion-trap mass spectrometry, multiple-stage CID experiments (MS(n)) on the protonated and fully exchanged ions were performed to decipher characteristic fragmentation pathways. The precursor and product ions from azaspiracids lost up to five water molecules from different regions during MS(n) experiments and it was possible to distinguish between the water losses from different molecular regions. These studies confirmed that the first water-loss ion in the spectra of azaspiracids resulted from dehydration at the vicinal diol at C20-C21. Five MS dissociation pathways were identified that resulted from fragmentation of the carbon skeleton of azaspiracids producing nitrogen-containing ions. Two pathways, involving cleavage of the E-ring and C27-C28, gave ions that were found in all azaspiracids. Three pathways, A-ring, C-ring and C19-C20 cleavages, were useful for distinguishing between azaspiracid analogues. The same product ions from backbone fragmentation were also observed using hybrid quadrupole time-of-flight mass spectrometry (QqTOFMS). The fragmentation of the A-ring was the most facile and was exploited in the development of LC/MS(n) methods for the analysis of azaspiracids. 相似文献