全文获取类型
收费全文 | 2466篇 |
免费 | 479篇 |
国内免费 | 541篇 |
专业分类
化学 | 3065篇 |
晶体学 | 59篇 |
力学 | 50篇 |
综合类 | 24篇 |
数学 | 6篇 |
物理学 | 282篇 |
出版年
2024年 | 2篇 |
2023年 | 32篇 |
2022年 | 61篇 |
2021年 | 88篇 |
2020年 | 120篇 |
2019年 | 115篇 |
2018年 | 78篇 |
2017年 | 94篇 |
2016年 | 157篇 |
2015年 | 157篇 |
2014年 | 164篇 |
2013年 | 287篇 |
2012年 | 198篇 |
2011年 | 212篇 |
2010年 | 149篇 |
2009年 | 162篇 |
2008年 | 162篇 |
2007年 | 164篇 |
2006年 | 181篇 |
2005年 | 153篇 |
2004年 | 130篇 |
2003年 | 124篇 |
2002年 | 87篇 |
2001年 | 66篇 |
2000年 | 38篇 |
1999年 | 38篇 |
1998年 | 42篇 |
1997年 | 44篇 |
1996年 | 36篇 |
1995年 | 31篇 |
1994年 | 23篇 |
1993年 | 21篇 |
1992年 | 15篇 |
1991年 | 7篇 |
1990年 | 14篇 |
1989年 | 10篇 |
1988年 | 10篇 |
1987年 | 1篇 |
1986年 | 4篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 2篇 |
1982年 | 1篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有3486条查询结果,搜索用时 31 毫秒
991.
Li Zhou Chao Gao Prof. Dandan Zhu Weijian Xu Prof. Fanqing Frank Chen Prof. Amit Palkar Dr. Luis Echegoyen Prof. Eric Siu‐Wai Kong Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(6):1389-1396
Facile functionalization of multilayer fullerenes (carbon nano‐onions, CNOs) was carried out by [2+1] cycloaddition of nitrenes. The products were further derivatized by using the “grafting from” strategy of in situ ring‐opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Using one‐step nitrene chemistry with high‐energy reagents, such as azidoethanol and azidoethyl 2‐bromo‐2‐methyl propanoate, in N‐methyl‐2‐pyrrolidone at 160°C for 16 h, hydroxyl and bromide functionalities were introduced onto the surfaces of CNOs. These hydroxyl CNOs (CNO‐OH) and bromic CNOs (CNO‐Br) were extensively characterized by various techniques such as thermal gravimetric analysis (TGA), transmission electron microscopy (TEM), Raman spectroscopy and X‐ray photo electron spectroscopy (XPS). TGA measurements indicated that the surface hydroxyl and bromide group density reached 1.49 and 0.49 mmol g?1, respectively. The as‐functionalized CNOs showed much better solubility in solvents than pristine CNOs. The CNO‐OH were also observed to fluoresce at λ=453 nm in water. The CNO‐OH and CNO‐Br can be conveniently utilized as macroinitiators to conduct surface‐initiated in‐situ polymerizations. Poly(ε‐caprolactone) (PCL, 45wt %) and polystyrene (PS, 60 wt%) were then grafted from surfaces of CNOs through the ROP of ε‐caprolactone with the macroinitiator CNO‐OH and the ATRP of styrene with the macroinitiator CNO‐Br, respectively. The structures and morphology of the resulting products were characterized by 1H NMR, scanning electron microscopy (SEM), TEM, and atomic force microscopy (AFM). The polymer functionalized CNOs have good solubility/dispersibility in common organic solvents. The facile and scalable functionalization approaches can pave the way for the comprehensive investigation of chemistry of CNOs and fabrication of novel CNO‐based nanomaterials and nanodevices. 相似文献
992.
Daniel Pellico Mar Gómez‐Gallego Prof. Pedro Ramírez‐López Dr. María José Mancheño Prof. Miguel A. Sierra Prof. M. Rosario Torres Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(28):6940-6952
The synthesis, isolation, and full characterization of different types of stable, metal‐assembled macrocyclic β‐lactams are reported. By using adequately functionalized bis‐β‐lactams with defined stereochemistry as building blocks, a series of mono‐ and bimetallic Pd and Pt macrocycles has been prepared in good to quantitative yields. These novel structures combine the β‐lactam moiety with transition‐metal fragments with cis‐square‐planar geometry and constitute a new class of metal‐assembled cavities involving molecules with biological relevance as building blocks. By combining the adequate ligands, metallic fragments, and tuning the reaction conditions, different mono‐ and bimetallic macrocyclic β‐lactam cavities can be selectively obtained. Macrocycles with Pt–ethynyl groups are suitable to form host–silver triflate guest complexes in a tweezer fashion. 相似文献
993.
994.
995.
996.
A new inorganic polymer–platinum complex, silicasupported polysilazane–platinum complex, has been prepared and found to be capable of catalyzing the oxygenation of 3-pentanol to 3-pentanone in 100% yield at moderate temperature and under atmospheric oxygen pressure. Water is the best solvent for this reaction. This inorganic polymer complex is very stable in the reaction and can be reused several times without any appreciable change in catalytic activity. 相似文献
997.
An amphiphilic polymer resin‐dispersion of nanoparticles of palladium was designed and prepared with a view toward use for catalysis in water. The amphiphilic polystyrene‐poly(ethylene glycol) (PS‐PEG) resin‐dispersion of nanoparticles of palladium exhibited high catalytic performance in the hydrodechlorination of chloroarenes under aqueous conditions. The amphiphilic resin‐supported nanopalladium and nanoplatinum particles also catalyzed aerobic oxidation of various alcohols including nonactivated aliphatic and alicyclic alcohols, which is one of the most fundamental and important yet immature processes in organic chemistry, in water under an atmospheric pressure of oxygen gas to form aldehydes, ketones, and carboxylic acids to meet green chemical requirements. Viologen polymer‐supported nanopalladium catalyst realized α‐alkylation of ketones with primary alcohols as the alkylating agents. © 2009 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 9: 51–65; 2009: Published online in Wiley InterScience ( www.interscience.wiley.com ) DOI 10.1002/tcr.20165 相似文献
998.
999.
1000.
Masashi Nakamura Dr. Yuto Hanioka Wataru Ouchida Mami Yamada Prof. Dr. Nagahiro Hoshi Prof. Dr. 《Chemphyschem》2009,10(15):2719-2724
Surface structures of shape‐controlled Pt nanoparticles have been estimated using cyclic voltammetry (CV) and infrared reflection absorption spectroscopy (IRAS). Cubic and cuboctahedral Pt nanoparticles are prepared using a capping polymer. These nanoparticles give CVs similar to those of single crystal electrodes of Pt in sulfuric acid solution. The CV of cubic nanoparticles is similar to that of the Pt(510) [=5(100)–(110)] electrode, while the CV of cuboctahedral nanoparticles is reproduced well with the convolution of Pt(766) [=13(111)–(100)] and Pt(17 1 1) [=9(100)–(111)] electrodes. These results suggest that the planes of the cubic and cuboctahedral nanoparticles are composed of step‐terrace and atomically flat terraces, respectively. Adsorbed carbon monoxide (CO) on the shape‐controlled nanoparticles gives the IR bands that are assigned to on‐top and bridged CO. The band of on‐top CO is deconvoluted to two bands: the higher and the lower frequency bands are assigned to the CO on the plane and the edges of the nanoparticles, respectively. On‐top CO adsorbed on the edges is oxidized at more negative potential than that on the planes. Edge sites of the nanoparticles promote CO oxidation. 相似文献