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排序方式: 共有307条查询结果,搜索用时 15 毫秒
121.
Ultrafine Ru nanoparticles are successfully deposited on MCM-41 by using a simple liquid impregnationreduction method, and further investigated for catalytic hydrolysis of ammonia borane and methylamine borane. Among all the catalysts tested, 1.12 wt% Ru/MCM-41 exhibits the highest catalytic activity, with turnover frequency value of 288 min-1. 相似文献
122.
Iron‐Catalyzed Dehydropolymerization: A Convenient Route to Poly(phosphinoboranes) with Molecular‐Weight Control 下载免费PDF全文
Dr. André Schäfer Dr. Titel Jurca Joshua Turner Dr. James R. Vance Dr. Kajin Lee Dr. Van An Du Dr. Mairi F. Haddow Dr. George R. Whittell Prof. Dr. Ian Manners 《Angewandte Chemie (International ed. in English)》2015,54(16):4836-4841
The catalyst loading is the key to control the molecular weight of the polymer in the iron‐catalyzed dehydropolymerization of phosphine–borane adducts. Studies showed that the reaction proceeds through a chain‐growth coordination–insertion mechanism. 相似文献
123.
Nanostructured Ni2P as a Robust Catalyst for the Hydrolytic Dehydrogenation of Ammonia–Borane 下载免费PDF全文
Cheng‐Yun Peng Lei Kang Shuang Cao Prof. Dr. Yong Chen Prof. Dr. Zhe‐Shuai Lin Prof. Dr. Wen‐Fu Fu 《Angewandte Chemie (International ed. in English)》2015,54(52):15725-15729
Ammonia–borane (AB) is a promising chemical hydrogen‐storage material. However, the development of real‐time, efficient, controllable, and safe methods for hydrogen release under mild conditions is a challenge in the large‐scale use of hydrogen as a long‐term solution for future energy security. A new class of low‐cost catalytic system is presented that uses nanostructured Ni2P as catalyst, which exhibits excellent catalytic activity and high sustainability toward hydrolysis of ammonia–borane with the initial turnover frequency of 40.4 mol(H2) mol(Ni2P)?1 min?1 under air atmosphere and at ambient temperature. This value is higher than those reported for noble‐metal‐free catalysts, and the obtained Arrhenius activation energy (Ea=44.6 kJ mol?1) for the hydrolysis reaction is comparable to Ru‐based bimetallic catalysts. A clearly mechanistic analysis of the hydrolytic reaction of AB based on experimental results and a density functional theory calculation is presented. 相似文献
124.
Dong Wook Kim Dr. Seewon Joung Dr. Jeung Gon Kim Prof. Dr. Sukbok Chang 《Angewandte Chemie (International ed. in English)》2015,54(49):14805-14809
The first example of metal‐free hydrosilylation polymerization between dienes and disilanes is developed by using a borane catalyst, B(C6F5)3 to replace precious transition‐metal‐based systems. Under the easy‐to‐handle and mild conditions, a step‐growth polymerization of two readily available diene and disilane units was achieved with high degrees of polymerization. Various combinations of dienes and disilanes produced polycarbosilanes with a broad range of structures and properties. 相似文献
125.
Zhenpin Lu Luca Schweighauser Dr. Heike Hausmann Prof. Dr. Hermann A. Wegner 《Angewandte Chemie (International ed. in English)》2015,54(51):15556-15559
The storage of energy in a safe and environmentally benign way is one of the main challenges of today’s society. Ammonia–borane (AB=NH3BH3) has been proposed as a possible candidate for the chemical storage of hydrogen. However, the efficient release of hydrogen is still an active field of research. Herein, we present a metal‐free bis(borane) Lewis acid catalyst that promotes the evolution of up to 2.5 equivalents of H2 per AB molecule. The catalyst can be reused multiple times without loss of activity. The moderate temperature of 60 °C allows for controlling the supply of H2 on demand simply by heating and cooling. Mechanistic studies give preliminary insights into the kinetics and mechanism of the catalytic reaction. 相似文献
126.
(2-Amino-3-cyano-4H-chromen-4-yl) phosphonic acid diethyl esters are prepared via a single-step multi-component reaction of structurally diverse salicylaldehydes with malononitrile and triethyl phosphite using a catalytic amount of potassium phosphate in ethanol at ambient temperature. Use of potassium phosphate as an inexpensive catalyst makes the protocol more economical. Mild reaction conditions, simple work-up procedure are the added advantages of the present method. 相似文献
127.
Without a catalyst ketones and aldehydes were reacted in THF with ammonia borane (AB) to proceed hydroboration forming alkyl borates. Mechanistic studies revealed that dissociation of ammonia from AB occurred before the hydroboration step. When methanol was used as the solvent, metal free methanolysis of AB would take place with the ketone/aldehyde being directly hydrogenated by the MeOH·BH3 complex. 相似文献
128.
An efficient method was developed for the nickel-catalyzed phosphonylation of aryl triflates with triethyl phosphite, in which KBr as an additive promoted the SN2 catalytic step. To the best of our knowledge, this is the first example of nickel-catalyzed Arbuzov reactions of aryl triflates. Most of the substrates showed good reactivity under this catalytic system. 相似文献
129.
130.
Shyamapada BanerjeeP. Srishylam S. Rajendra PrasadMichael T. Migawa Eric E. SwayzeYogesh S. Sanghvi 《Tetrahedron letters》2012,53(35):4669-4672
A convenient single-step synthesis of several 2,7-dimethyl-9-phenylxanthen-9-ol (DMPx-OH) analogs has been accomplished using a Friedel-Crafts reaction. Treatment of various DMPx-OH with unprotected 2′-O-methoxyethyl-ribonucleosides (MOE) in the presence of B(C6F5)3, as a Lewis Acid catalyst, furnished 5′-O-protected derivatives of 2′-MOE-ribonucleosides in good yields. The deprotection of the DMPx groups was accomplished by acid hydrolysis under very mild conditions. Among the five DMPx analogs synthesized, the 2,7-dimethyl-9-(4-nitrophenyl)xanthene-9-yl group furnished crystalline products enabling non-chromatographic isolation of 5′-O-protetced nucleosides. 相似文献