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排序方式: 共有95条查询结果,搜索用时 31 毫秒
31.
分子筛催化cis-2-丁烯的双键异构反应机理的DFT研究 总被引:1,自引:0,他引:1
基于含有两个Si和一个Al的分子筛3T簇模型, 利用密度泛函方法(DFT)研究了分子筛催化1-丁烯双键异构为cis-2-丁烯的反应机理. 在B3LYP/6-31G(d,p)计算水平上对反应各驻点进行了全优化, 并计算了反应的活化能. 研究发现, 分子筛上的酸性OH基团首先通过物理吸附靠近1-丁烯的双键, 形成了π配位复合物后, 丁烯双键的端基C原子逐渐抽取这个质子, 同时相邻酸性位的一个O原子也抽取丁烯碳链上的一个H原子, 形成吸附态的cis-2-丁烯, 最后通过脱附形成产物, 使分子筛复原, 反应按照协同反应机理发生. 计算得到的表观活化能是55.9 kJ/mol, 与实验结果接近. 相似文献
32.
在H3PO4存在下进行了2,3-二甲基-2-丁烯与乙酐的酰化反应,结果表明,H3PO4是室温下催化2,3-二甲基-2-丁烯与乙酐酰化反应的有效催化剂,在H3PO4存在下,酰化产物的收率主要取决于:(a)H3PO4的用量,(b)乙酐的用量;(c)反应温度和(d)反应时间,在适宜反应条件下,所得3,3,4-三甲基-4-戊烯-2-酮(TMP)约为99%,另外还发现,反应体系中加入少量乙酸,不会明显减少酰化产物的收率,乙酐的纯度,反应物的加入顺序对该反应几乎没有任何影响,在有和没有溶剂CH2Cl2的条件下所得酰化产物的收率是可比的。 相似文献
33.
Farhan Arafin Andrew Laich Erik Ninnemann Robert Greene Ramees K. Rahman Subith S. Vasu 《国际化学动力学杂志》2020,52(11):739-751
Shock tube experiments have been carried out on 2-methyl-1-butene (2M1B), 2-methyl-2-butene (2M2B), and 3-methyl-1-butene (3M1B)—the three isomers of methyl butene compound. Carbon monoxide (CO) time-histories and ignition delay times are obtained behind reflected shockwaves over the temperature range of 1350-1630 K and pressures of 8.3-10.5 atm with stoichiometric mixtures of 0.075% fuel in O2/Ar. Comparative ignition study reveals that 3M1B ignites significantly faster than the other two isomers, while 2M1B dissociates earlier but ignites later than 2M2B. Possible mechanisms for this behavior are discussed with ignition delay time sensitivity and reaction path analysis. In addition, time-resolved CO measurements are compared with three different reaction mechanisms from the literature. Sensitivity analyses have been carried out to identify important reactions that need attention to accurately predict the chemistry of these isomers. Further investigation into the rates of unimolecular fuel decomposition reactions and C3H3 + O2 = CH2CO + HCO reaction are suggested based on the current investigation. 相似文献
34.
Synthesis and characterization of Ni (II) complexes supported by phenoxy/naphthoxy‐imine ligands with pendant N‐ and O‐donor groups and their use in ethylene oligomerization 下载免费PDF全文
L.L. de Oliveira S.M. da Silva A.C.A. Casagrande R. Stieler O.L. Casagrande Jr. 《应用有机金属化学》2018,32(7)
A series of new Ni(II) complexes of general formula Ni{ZNO} Br ( 2a‐i ) (ZNO = phenoxy/naphthoxy‐imine with pendant N‐ and O‐donor groups) were prepared and characterized by elemental analysis, IR spectroscopy, ESI‐HRMS, and by X‐ray crystallography for 2e . In the solid state, 2e features a monomeric structure with κ3 coordination of the monoanionic naphthoxy‐imine‐quinoline ligand onto the nickel center. Upon activation with MAO, both classes of nickel catalysts were able to produce selectively 1‐butene (81.5–92.1 wt%) with turnover frequencies (TOFs) varying from 3,100 to 24,300 mol(C2H4) mol (Ni)?1 h?1. Nickel precatalysts bearing phenoxy‐imine ligands were much more active than its naphthoxy analogous under the same conditions. The use of a mixture of cocatalysts (MAO/TMA or MAO/TiBA) resulted in poor activities; however the presence of TiBA in the milieu led to a significant improvement on selectivity for 1‐hexene (25.5 wt%). Under optimized conditions ([Ni] = 10 μmol, 30 °C, oligomerization time = 5 min, 20 bar ethylene, [Al]/[Ni] = 600), precatalyst 2c led to TOF = 59,900 mol(C2H4) mol(Ni)?1 h?1 and selectivity for 1‐butene of 89.5 wt%. 相似文献
35.
Wei Wang Chunguang Shao Lirong Zheng Bin Wang Li Pan Guiqiu Ma Yuesheng Li Yaming Wang Chuntai Liu Zhe Ma 《Journal of Polymer Science.Polymer Physics》2019,57(2):116-126
The stretching‐induced phase transition from tetragonal Form II to hexagonal Form I and the evolution of corresponding crystallite orientation were studied for the butene‐1/ethylene random copolymer with 1.5 mol % ethylene by using a combination of tensile test and in situ wide‐angle X‐ray diffraction. Three orientation pathways were distinguished for II‐I phase transition, including phase transition accomplishing within off‐axis oriented crystallites (Orientation Pathway 1), phase transition with simultaneous formation of highly oriented crystallites (Orientation Pathway 2), and phase transition occurring within the highly oriented crystallites already formed (Orientation Pathway 3). The kinetics of II‐I transition was correlated with the macroscopic mechanical response, which exhibits a strong dependence on orientation. In Orientation Pathway 1, the triggering of phase transition corresponds to the mechanical yielding. More interestingly, the kinetics of transition exhibits the identical dependence on stress. However, in Orientation Pathways 2 and 3, appearance of the highly oriented crystallites substantially alters transition kinetics, which is tentatively associated with the stress bearing by interstack tie chains. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 116–126 相似文献
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38.
制备了一系列用过渡金属M (M =Pt,Co ,Ni,Mn ,Fe,Cu)活化的WO3 /ZrO2 固体强酸催化剂 ,用XRD ,DTA TG ,H2 TPR ,NH3 TPD等测定了其晶型结构、表面状态和酸量 .结果表明 ,各样品中的ZrO2 主要以T晶相存在 ,但T晶相ZrO2 所占的比例因过渡金属不同而异 ,比表面积比WO3 /ZrO2 稍有下降 ;金属Pt的引入使呈单层分散的WO3 的表面状态发生了改变 .研究了异丁烷 /丁烯烷基化反应 ,其反应活性与酸量的测定结果有对应关系 ;与WO3 /ZrO2 相比 ,M WO3 /ZrO2 上的丁烯转化率均稍有下降 ,但具有更高的i C08选择性 .从反应机理分析了添加过渡金属无显著效果的原因 . 相似文献
39.
茂金属催化聚合的聚1-丁烯的结构表征 总被引:3,自引:0,他引:3
以 η5 五甲基茂基三苄氧基钛 (Cp Ti(OBz) 3 和改性甲基铝氧烷 (mMAO)为催化剂 ,合成立体嵌段聚 1 丁烯 ,分子量高 ,分子量分布窄 ( Mw/ Mn=1 1~ 1 2 ) .聚合产物经沸乙醚、沸庚烷连续抽提分离 ,聚合物在两种溶剂中都能部分溶解 .各级份经13C NMR ,WAXD ,DSC和GPC等手段分析 ,结果表明乙醚可溶级份是无规聚 1 丁烯 ,庚烷可溶级份是立体嵌段聚 1 丁烯 ,庚烷不溶级份是等规聚 1 丁烯 .聚合温度较低 (0℃和30℃ )时 ,聚合物有结晶性 ,结晶度达 30 %以上 ,DSC分析有两个吸热峰 ;聚合温度较高 (4 0℃ )时 ,聚合物无结晶尖锐X射线衍射峰 ,也无熔融吸热峰 . 相似文献
40.
水蒸气处理对ZSM-5酸性及其催化丁烯裂解性能的影响 总被引:14,自引:1,他引:13
考察了水蒸气处理温度和时间对ZSM-5分子筛酸性及其催化丁烯裂解性能的影响. 结果表明,通过水蒸气处理可降低ZSM-5分子筛的酸量和酸强度,明显提高产物中丙烯与乙烯的选择性和收率,抑制副产物芳烃和低碳烷烃的生成. 用柠檬酸脱除水蒸气处理过程中产生的非骨架铝,可提高ZSM-5分子筛孔道的容碳能力,从而提高催化剂的稳定性. 考察了反应条件对催化剂性能的影响,结果表明较佳的反应条件为WHSV=3.5~8.8 h-1,p=0.06~0.1 MPa,θ=600~620 ℃. 相似文献