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991.
前驱体和沉淀剂浓度对CuO/ZnO/CeO-ZrO甲醇水蒸气重整制氢催化剂性能的影响 《燃料化学学报》2015,43(11):1366-1374
采用共沉淀法制备了CuO/ZnO/CeO2-ZrO2甲醇水蒸气重整制氢催化剂,探讨了前驱体和沉淀剂浓度对催化剂性能的影响,并采用BET、XRD、H2-TPR和XPS等手段对催化剂进行了表征。结果表明,前驱体和沉淀剂浓度对催化剂的结构和性能影响很大,当前驱体浓度为0.1mol/L,沉淀剂浓度为0.5mol/L时,所得催化剂CO选择性最小,催化活性最佳。在360h稳定实验中,甲醇最高转化率达100%,重整尾气中H2含量保持在74.5%以上,CO含量低于0.8%,催化剂稳定性良好。 相似文献
992.
采用水热法和牺牲模板法相结合制备具有中空树枝结构的三氧化钨载体(d-WO3),在其表面进一步负载活性成分Pt,得到纳米Pt/d-WO3复合催化剂。采用X射线粉末衍射(XRD)、透射电镜(TEM)和比表面积和孔结构分析(BET)等对催化剂的形貌和结构进行了表征。结果表明,三氧化钨具有长6 μm和宽2 μm的中空树枝状结构,孔径分布主要集中在20~120 nm,比表面积为24 m2/g,平均粒径为7.2 nm的Pt纳米粒子均匀分布在其表面。采用循环伏安和计时电流法研究了Pt/d-WO3催化剂在酸性溶液中对甲醇的电催化氧化性能。结果表明,Pt/d-WO3催化剂比Pt/C和Pt/WO3催化剂对甲醇有更高的电催化氧化活性和稳定性。d-WO3所具有的中空介孔结构和双功能作用机理有利于甲醇在铂表面的直接脱氢氧化过程。 相似文献
993.
Effects of Coke Deposits on the Catalytic Performance of Large Zeolite H‐ZSM‐5 Crystals during Alcohol‐to‐Hydrocarbon Reactions as Investigated by a Combination of Optical Spectroscopy and Microscopy 下载免费PDF全文
Dr. Emily C. Nordvang Dr. Elena Borodina Dr. Javier Ruiz‐Martínez Prof. Dr. Rasmus Fehrmann Prof. Dr. Bert M. Weckhuysen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(48):17324-17335
The catalytic activity of large zeolite H‐ZSM‐5 crystals in methanol (MTO) and ethanol‐to‐olefins (ETO) conversions was investigated and, using operando UV/Vis measurements, the catalytic activity and deactivation was correlated with the formation of coke. These findings were related to in situ single crystal UV/Vis and confocal fluorescence micro‐spectroscopy, allowing the observation of the spatiotemporal formation of intermediates and coke species during the MTO and ETO conversions. It was observed that rapid deactivation at elevated temperatures was due to the fast formation of aromatics at the periphery of the H‐ZSM‐5 crystals, which are transformed into more poly‐aromatic coke species at the external surface, preventing the diffusion of reactants and products into and out of the H‐ZSM‐5 crystal. Furthermore, we were able to correlate the operando UV/Vis spectroscopy results observed during catalytic testing with the single crystal in situ results. 相似文献
994.
Jing-Hui Lyu Hua-Lei Hu Jia-Yao Rui Qun-Feng Zhang Jie Cen Wen-Wen Han Qing-Tao Wang Xiao-Kun Chen Zhi-Yan Pan Xiao-Nian Li 《中国化学快报》2017,28(2):482-486
Nitrided hierarchical porous ZSM-5 was synthesized by nitridation of hierarchical porous ZSM-5 with flowing ammonia at elevated temperature. The samples were characterized by XRD, SEM, Nitrogen sorption isotherms, NH3-TPD and Py-IR, and evaluated in alkylation of benzene and methanol. The result indicated that the high specific surface area of parent ZSM-5 was maintained, while the Brönsted acidity was effectively adjusted by nitridation. Moreover, the high suppression of ethylbenzene was observed on nitrided catalyst and this could be attributed to the decrease of Brönsted acidity which suppressed the methanol to olefins reactions. 相似文献
995.
《Electroanalysis》2017,29(12):2896-2905
In this study, immobilized hollow nanospheres of Fe3O4 with Palladium, Platinum and Gold nanoparticles (Fe3O4HNS‐PdPtAuNPs) was synthesized by hydrothermal and chemical reduction methods and characterized by various techniques such as field emission scanning electron microscopy, energy dispersive analysis of X‐rays and elemental mapping images. The electrocatalytic activity of the modified glassy carbon electrode (GCE) with Fe3O4HNS‐PdPtAuNPs (GCE/Fe3O4HNS‐PdPtAuNPs) toward methanol electrooxidation was investigated by cyclic voltammetry and chronoamperometry in 1 M NaOH solution. According to the results, Fe3O4HNS‐PdPtAuNPs catalyst demonstrated the highest efficiency for methanol electrooxidation in comparison with Fe3O4HNS‐PdNPs, Fe3O4HNS‐PtNPs, Fe3O4HNS‐PdAuNPs, Fe3O4HNS‐PtAuNPs and Fe3O4HNS‐PdPtNPs. The value of electron transfer coefficient (α ) and the ratio of current densities (If /Ib ) for methanol oxidation on the Fe3O4HNS‐PdPtAuNPs/GC catalyst were calculated 0.61 and 5.13, respectively. The reaction order was discovered to be 0.98 for CH3OH. A direct methanol fuel cell was developed with the suggested catalyst under several conditions. 相似文献
996.
Regioselective Pd‐Catalyzed Methoxycarbonylation of Alkenes Using both Paraformaldehyde and Methanol as CO Surrogates 下载免费PDF全文
Dr. Qiang Liu Kedong Yuan Dr. Percia‐Beatrice Arockiam Robert Franke Dr. Henri Doucet Dr. Ralf Jackstell Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2015,54(15):4493-4497
In recent years, considerable effort has focused on the development of novel carbonylative transformations using CO surrogates. Consequently, toxic CO gas can be replaced by more convenient inorganic or organic carbonyl compounds. Herein, the first regioselective methoxycarbonylation of alkenes with paraformaldehyde and methanol as CO substitutes is reported. This new procedure is applicable to a series of alkenes in the presence of a palladium catalyst under relatively mild conditions and is highly atom efficient. 相似文献
997.
Dr. Carmen C. Mayorga‐Martinez Prof. Dr. Zdeněk Sofer Prof. Dr. Martin Pumera 《Angewandte Chemie (International ed. in English)》2015,54(48):14317-14320
Black phosphorus is a layered material that is sensitive to the surrounding atmosphere. This is generally considered as a disadvantage, especially when compared to more stable layered compounds, such as graphite or MoS2. This sensitivity is now turned into an advantage. A vapor sensor that is based on layered black phosphorus and uses electrochemical impedance spectroscopy as the detection method is presented; the device selectively detects methanol vapor. The impedance phase measured at a constant frequency is used as a distinctive parameter for the selective quantification of methanol, and increases with the methanol concentration. The low detection limit of 28 ppm is well below the approved exposure limit of 200 ppm. The results are highly reproducible, and the vapor sensor is shown to be very selective in the presence of other vapors and to have long‐term stability. 相似文献
998.
采用浸渍和共沉淀两种方法分别制备了Ba O改性的Pd/CeO2-ZrO2-La2O3-Al2O3催化剂。运用N2吸附-脱附,X射线衍射(XRD),H2程序升温还原(H2-TPR),NH3程序升温脱附(NH3-TPD),透射电子显微镜(TEM)和X射线光电子能谱(XPS)对催化剂进行表征,并考察其对甲醇,CO,C3H8和NO的催化性能。活性测试结果表明,Ba O的引入可明显改善Pd催化剂对甲醇,CO,C3H8和NO的催化活性,且浸渍法最佳,起燃温度(T50)分别降低了43,31,45和35℃。XRD,H2-TPR及XPS结果表明,浸渍法引入Ba O主要通过表面改性方式,强化Pd-Ce界面间的相互作用,改善催化剂的还原性能,进而提高催化剂的低温活性;而共沉淀法则是通过结构改性方式增加CeO2晶格缺陷,加速活性氧物种的流动,Ce3+浓度的增加是促使CO氧化活性显著提高的主要原因。 相似文献
999.
1000.
不同硅铝比Al-ITQ分子筛的甲醇制丙烯反应催化性能 《燃料化学学报》2017,45(11):1349-1355
采用晶种法直接合成了硅铝比(SiO_2/Al_2O_3物质的量比)为137、224和309的三种Al-ITQ-13分子筛,并采用粉末X射线衍射(XRD)、扫描电镜(SEM)、N_2吸附-脱附、固体核磁共振(MAS NMR)和NH_3-程序升温脱附(NH_3-TPD)等分析方法对不同硅铝比分子筛进行了表征,并在固定床微型反应评价装置上,考察了硅铝比对甲醇转化制丙烯反应性能的影响。结果表明,不同硅铝比Al-ITQ-13分子筛呈现出相似的织构性质,酸量及酸强度随着硅铝比的升高逐渐下降。硅铝比对甲醇转化反应的产物分布存在较大的影响;随着硅铝比的升高,氢转移反应和芳构化反应活性降低,使得乙烯选择性下降,而丙烯和丁烯的选择性升高。硅铝比由137提高到309,丙烯的选择性(质量分数)由46.04%增加到55.52%,而丙烯/乙烯比由3.39提高到6.57。 相似文献