首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   5篇
  免费   0篇
  国内免费   3篇
林业   1篇
农学   1篇
  4篇
综合类   1篇
园艺   1篇
  2017年   1篇
  2015年   1篇
  2012年   1篇
  2011年   2篇
  2007年   1篇
  2002年   1篇
  1997年   1篇
排序方式: 共有8条查询结果,搜索用时 31 毫秒
1
1.
针对氢氧化钠作用下水合肼还原硒形成Na2Se2 与磺酸酯反应制备二烷基二硒醚需要在高温(100 ℃)下才能有效进行,且仅适用于制备不含官能团的二烷基二硒醚的问题.由于铯离子体积大, 与阴离子之间的静电作用弱, 使与之键合的阴离子表现出强的碱性和亲核性,利用铯碱作缩合剂,能显著降低反应的活化能, 使许多反应在温和条件下就能有效进行.根据离子交换原理,采用氯化铯和TBAI作催化剂, 以无水DMF作溶剂, 4A分子筛作吸水剂, 氢氧化钾促进肼还原硒, 随后与含官能团的卤代烃或磺酸酯反应, 高收率地形成对应的二烷基二硒醚.本方法不仅可以合成含官能团的二硒醚,而且具有反应条件温和、产率高等优点.  相似文献   
2.
Polyaluminum silicate is a new type of inorganic macromolecular flocculants, which is developed as a complex product in recent years on the base of polyalumium flocculant and polysilicic acid flocculant. Sodium silicate is diluted to the concentration of 3.0% SiO 2 with distilled water. The solution was adjusted to pH 4.5 with sulphate acid and kept at quiescency for different time to get polysilicic acid with different polymerization degrees. Using polysilicic acid prepared and aluminium chloride as materials, a series of polyaluminium silicate chlorides(PASC) with different basicities(B), Al/Si molar ratios and polymerization degree of silicic acid are prepared by copolymerization technique. The Al-Ferron timed complex colorimetric method is applied to characterize species distribution of PASC and to study its influence factors. The interaction between hydrolyzed aluminum species and polysilicic acid with different polymerization degrees in PASC is discussed.The flocculant prepared is applied to the treatment of commercial concrete wastewater. The turbidity removal of commercial concrete wastewater is up to 97% when a PASC, prepared with polysilicic acid of 145 min polymerization degree.  相似文献   
3.
研究月桂烯氢氯化反应产物中里哪基氯、香叶基氯和橙花基氯3种烯丙型氯化物与醋酸钠的酯化反应。重点考察了催化剂、反应温度和氯化物组成对酯化反应产物分布的影响。结果表明:(1)在氯化亚铜催化剂存在下,3种烯丙基型氯化物与醋酸钠在醋酸溶剂中均可转化成醋酸里哪酯,酯化反应选择性达96%以上;(2)在三乙胺催化剂存在下,3种烯丙基型氯化物与醋酸钠反应可转化成相应的醋酸酯,但里哪基氯酯转化生成醋酸里哪酯的选择性明显低于香叶基氯和橙花基氯,且伴随有消除副产物生成;(3)低温有利于醋酸里哪酯的生成,温度升高有利于醋酸里哪酯向醋酸香叶基酯和醋酸橙花酯的生成;在优化反应条件下,醋酸里哪酯的选择性达96.5%。  相似文献   
4.
为研究金属盐对水稻秸秆热裂解特性的影响,在Li2CO3-Na2CO3-K2CO3(LNK碳酸盐)中分别添加氯化盐和硫酸盐与水稻秸秆干混,采用热重分析与傅里叶变换红外光谱联用技术(thermogravimetric analyzer coupled with Fourier transform infrared spectrometry,TG-FTIR)研究了水稻秸秆的热裂解过程,并使用Coats-Redfern法计算了热裂解过程的动力学参数。结果表明:在LNK碳酸盐作用下,热裂解的活化能降低。与添加硫酸盐相比,氯化盐作用下热裂解活化能更低,热裂解反应更易进行。与纯水稻秸秆热裂解相比,LNK碳酸盐能使CO、CH4、苯酚、甲苯、甲酸和水等的浓度明显下降,而CO2浓度显著上升。在LNK碳酸盐基础上,氯化盐和硫酸盐均能促进水稻秸秆热裂解产物的生成和逸出。当温度高于550℃时,碳酸盐能催化Boudouard反应,氯化盐和硫酸盐均能促进该反应的进行。其中,Ni Cl2和Co Cl2对该反应的影响尤其明显。研究为生物质资源的高值化利用提供了一定的理论参考。  相似文献   
5.
AIM: Using the mouse model of lipopolysaccharide(LPS) attack,we study the effect of Kupffer cell (KC) blockade on the activation of mitogen-activated protein kinases(MAPKs) signal transduction pathway induced by LPS.METHODS: GdCl3 (10 mg/kg) or the same volume of NS was continually injected intravenously at 48 h and 24 h before LPS (5 mg/kg) was injected into the male mice of Kunming species.The liver was then took out and KCs were isolated 30 minute after LPS was injected.The KCs isolated from the mice were cultured,and pretreated with GdCl3 (100 μmol/L) for 1 h.The culture medium containing LPS (100 μg/L) was added and continuously incubated for 30 minute.The protein expression and phosphorylation level of ERK1/2 and p38MAPK in liver or KCs were assayed in vivo and in vitro,and effect of GdCl3 on the phagocytosis function was observed,respectively.RESULTS: LPS induced the protein phosphorylation of ERK1/2 and p38MAPK in KCs or liver,no effect on the protein expression was observed.GdCl3 treatment inhibited LPS-induced KCs activation and secretion of TNF-α,however,it had no effect on ERK1/2 and p38MAPK in KCs or liver,neither at the protein expression nor the phosphorylation.KCs secreted a few TNF-α with short time treatment with GdCl3 alone in vitro.CONCLUSION: KC blockade with GdCl3 alleviates LPS-induced KCs activation and the release of TNF-α not through modulating intracellular ERK1/2 or p38MAPK signal transduction pathways.We presume that GdCl3 might reduce liver injury through cross talk of other intracellular signal transduction pathways (JNK,NF-кB,GPCR,etc).  相似文献   
6.
为了研究超富集植物热解中氯对重金属迁移特性的影响,该文考察了在管式反应炉上N2气氛中,不同温度下无机氯(NaCl)和有机氯(PVC)的加入对重金属迁移特性的影响。结果表明,无论NaCl,还是PVC,都将增加重金属的挥发。对于Cd、Pb,有机氯的影响大于无机氯,而对于Zn、Mn和Cu,NaCl添加剂对其挥发特性比PVC添加剂的影响大。除Cd外,在400~700°С温度范围内,相同含量氯下重金属的挥发随温度的升高变化不大,只有700°С以上挥发率的差别比较明显。在温度为900°С时,不论是否加入氯,Cd、Pb和Zn的挥发率都达到100%。在试验范围内,Mn和Cu的最大挥发率为66.15%和66.99%,底渣中Mn和Cu含量较多。  相似文献   
7.
Hydroponic production of rocket as a salad vegetable has become increasingly important in recent years. Rocket is known to be a high nitrate (NO3)-accumulating vegetable, which can be grown throughout the year. In the present study, rocket was grown in a floating hydroponic system at three levels of nitrogen (N) and sodium chloride (NaCl). The highest yield was obtained at 14 mM N, whereas the yield was lower at 20 mM and 40 Mm NaCl. Leaf elongation was more sensitive to salinity than leaf differentiation. Adding NaCl to the nutrient solution increased the relative chlorophyll content. Na+ and Cl concentrations increased as salinity increased. NO3? levels in fresh biomass increased with increased amounts of NO3? in the nutrient solution, and plants at 18 mM N were able to maintain a higher NO3? : Cl? ratio than those at 10 mM N.  相似文献   
8.
该文对蔗渣在温和条件(75~95℃)下转化制备5-氯甲基糠醛(5-CMF)的一锅法反应进行了研究,考察了AlCl3、LiCl、NaCl、KCl、MgCl2、CaCl2、BaCl2、CrCl3、NiCl2和FeCl3的催化效果,并利用GC-MS、1HNMR和FT-IR对目标产物进行了表征。研究结果表明:供试用的金属氯化物都具有一定的催化效果,其中AlCl3的催化效果明显优于碱金属、碱土金属和过渡金属氯化物;以AlCl3为催化剂,考察了反应温度、反应时间和AlCl3浓度对5-CMF产率的影响。得到反应的最佳条件为反应温度85℃,反应时间3h和AlCl3质量浓度为6.0g/L。在最优反应条件下5-CMF的产率为72%。该研究结果,对利用各种纤维素废弃物,开发潜在的生物汽油具有重要价值。  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号