全文获取类型
收费全文 | 399篇 |
免费 | 30篇 |
国内免费 | 8篇 |
专业分类
化学 | 258篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 56篇 |
物理学 | 103篇 |
出版年
2023年 | 2篇 |
2022年 | 11篇 |
2021年 | 17篇 |
2020年 | 22篇 |
2019年 | 28篇 |
2018年 | 36篇 |
2017年 | 16篇 |
2016年 | 27篇 |
2015年 | 17篇 |
2014年 | 35篇 |
2013年 | 59篇 |
2012年 | 30篇 |
2011年 | 14篇 |
2010年 | 15篇 |
2009年 | 15篇 |
2008年 | 12篇 |
2007年 | 19篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 2篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 1篇 |
2000年 | 2篇 |
1998年 | 1篇 |
1997年 | 5篇 |
1988年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1977年 | 3篇 |
1973年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
1967年 | 1篇 |
排序方式: 共有437条查询结果,搜索用时 15 毫秒
371.
372.
373.
Soraia Meghdadi Mahsa Kiani Farzaneh Fadaei Tirani Maryam Bagheri Kurt Job Schenk 《Journal of Coordination Chemistry》2017,70(14):2409-2424
Two carboxamide ligands, H2bqbenzo {3,4-bis(2-quinolinecarboxamido)benzophenone} and H2bqb {N,N′-bis[(2-quinolinecarboxamide)-1,2-benzene]}, have been prepared using tetrabutylammonium bromide as an environmentally benign reaction medium. Two new Pd(II) complexes, [PdII(bqbenzo)] (1) and [PdII(bqb)] (2), have been synthesized, characterized, and their structures determined by single crystal X-ray diffraction. The di-anionic ligands, bqbenzo2? and bqb2?, are coordinated via two Namide atoms and the nitrogens of the two quinoline rings, with Pd?Namide < Pd–Nquinoline bond lengths. The geometry around palladium(II) in both complexes is distorted square planar. The electrochemical behaviors of the ligands and their Pd(II) complexes have been investigated by cyclic voltammetry in DMF. An irreversible PdII/I reduction is observed at ?1.06 V for 1 and at ?1.177 V for 2, indicating the influence of the R substituent on the central phenyl ring of carboxamide ligands on the PdII/I reduction potential. The ligands and palladium complexes were also screened for in vitro antibacterial activity. The Pd(II) complexes show strong biological activity against S.typhi and E.coli as Gram ?ve and B.cereus and S.aureus as Gram +ve bacteria comparable to the antibiotic penicillin. The antibacterial results also reveal that coordination of Pd(II) significantly improves the activity. 相似文献
374.
Mahsa Asadniaye Fardjahromi Majid Moghadam Shahram Tangestaninejad Valiollah Mirkhani Iraj Mohammadpoor-Baltork 《Journal of the Iranian Chemical Society》2017,14(6):1317-1323
In this paper, we present an efficient and practical method for oxidation of alcohols to their corresponding carbonyl compounds catalyzed by [Mn(salophen)@nSTD]. This catalyst was synthesized, and characterized by FT-IR, UV–Vis, TGA, SEM and TEM. The results of experiments proved that this catalyst has excellent selectivity and high activity in the oxidation of different primary and secondary alcohols to their corresponding aldehyde and ketone at room temperature. The effects of important factors in the oxidation of alcohols such as kind of oxidant, solvent and amount of catalyst were investigated in the oxidation of 4-chlorobenzyl alcohol. This catalyst shows high stability and reusability after six catalytic runs. 相似文献
375.
Peyman Salehi Mahdi Ayyari Morteza Bararjanian Samad Nejad Ebrahimi Atousa Aliahmadi 《Journal of the Iranian Chemical Society》2014,11(3):607-613
A series of novel 2,3-dihydroquinazolin-4(1H)-ones was synthesized by a three-component reaction between dehydroabietylamine (DHA) diterpene, isatoic anhydride and different aromatic aldehydes in the presence of a catalytic amount of p-toluenesulfonic acid (13 mol%). Diastereomeric products were separated by preparative thin-layer chromatography and their structures were characterized by 1H and 13C NMR, HMQC, IR and HR-ESI-MS. Antioxidant activities of the synthesized compounds were assessed by two different methods including DPPH and β-carotene-linoleic acid bleaching assays. Antibacterial activities of the compounds were also evaluated against two Gram-positive and one Gram-negative bacterial strains and in the case of Bacillus cereus a considerable inhibitory effect (MIC 4–16 μg/ml) was observed. 相似文献
376.
Aliakbar Dehno Khalaji Mahsa Nikookar Debasis Das 《Journal of Thermal Analysis and Calorimetry》2014,115(1):409-417
Asymmetric bidentate Schiff base ligand (HL) and its cobalt(III), nickel(II), and copper(II) complexes have been synthesized (where L = 2-[(4-methoxy-2-nitrophenyl)iminomethyl]phenol). The ligand and its metal complexes have been characterized by elemental analyses (CHN) and FTIR spectroscopy. Thermogravimetric analyses of the compounds reveal their thermal stabilities along with their thermal decomposition pattern. In addition, the complexes have been used for the preparation of corresponding metal oxide nanoparticles by controlled aerobic thermal decomposed at 500 °C. The FTIR pattern of the obtained solids receals the formation of the metal oxides nanoparticles. 相似文献
377.
A Facile and One‐pot Synthetic Route to Functionalized Ethyl 3‐(Alkanoyl)‐2‐(alkyl imino)‐2,3‐dihydrothiazole‐4‐carboxylate Derivatives under Mild,Solventand Catalyst‐free Conditions
下载免费PDF全文
![点击此处可从《中国化学会会志》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A new one‐pot, four‐component synthetic rout is reported for the preparation of functionalized N‐acyl‐2alkylimino‐2,3‐dihydrothiazole derivatives from the reaction between acid chlorides, ammonium thiocyanate, primary alkylamines, and ethyl bromopyruvate under mild, solvent‐ and catalyst‐free conditions at room temperature. This completely green and efficient straight forward procedure led to the desired products in good to high yields without any need to catalyst or solvent assistance and no by product was observed in all the reactions 相似文献
378.
An efficient and green method for the synthesis of phthalide [isobenzofuran-1(3H)-one] fused pyrazoles via the catalyst-free condensation reaction of 2-formylbenzoic acid, hydrazine hydrate, and acetylenic esters in water is reported. Reaction of 2-formylbenzoic acid with 6-amino-uracils or cyclic 1,3-diketones resulted in the formation of phthalide-fused pyrimidine or cyclic 1,3-diketone derivatives. 相似文献
379.
Novel species of soluble thermally stable poly(keto ether ether amide)s: preparation,characterization, and properties
下载免费PDF全文
![点击此处可从《先进技术聚合物》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Elahe Sabbaghian Shahram Mehdipour‐Ataei Seyedmehrdad Jalilian Mahshid Esfahanizadeh Ali Mohammad Salehi Fardin Khodabakhshi Elham Jalalian 《先进技术聚合物》2015,26(1):1-9
A new diamine containing one keto and four ether groups was prepared through a three‐step reaction: first, hydroquinone was reacted with 1‐fluoro‐4‐nitrobenzene and 4‐(4‐nitrophenoxy) phenol was obtained. The next step was reduction of nitro group to amino group in which 4‐(4‐aminophenoxy) phenol was prepared. In the final step, the new diamine named as bis(4‐(4‐(4‐aminophenoxy)phenoxy)phenyl) methanone was synthesized through reaction of the later compound with 4,4′‐difluoro benzophenone. All prepared materials were fully characterized by spectroscopic methods and elemental analysis. Novel species of poly(keto ether ether amide)s were synthesized via polymerization reaction of the diamine with different diacid chlorides including terephthaloyl chloride, isophthaloyl chloride, and adipoyl chloride. All polyamides were characterized, and their properties such as thermal behavior, thermal stability, solubility, viscosity, water uptake, and crystallinity were investigated and compared together. The glass transition temperatures of the polymers were about 204–232°C, and their 10% weight losses were in the range of 396–448°C. Polymers showed high thermal stability and enhanced solubility that mainly resulted from incorporation of the diamine structure containing keto, ether, and aromatic units into polyamide backbones. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
380.
Karimian Somaye Ranjbar Sara Dadfar Mahsa Khoshneviszadeh Mahsima Gholampour Maryam Sakhteman Amirhossein Khoshneviszadeh Mehdi 《Molecular diversity》2021,25(4):2339-2349
Molecular Diversity - A series of ethyl 2-amino-4H-benzo[h]chromene-3-carboxylate derivatives, having phenyl ring with diverse substituents at C4 position of 4H-benzochromene nucleus, were... 相似文献