全文获取类型
收费全文 | 1025篇 |
免费 | 16篇 |
国内免费 | 165篇 |
专业分类
化学 | 1149篇 |
晶体学 | 1篇 |
力学 | 6篇 |
综合类 | 1篇 |
数学 | 3篇 |
物理学 | 46篇 |
出版年
2024年 | 1篇 |
2023年 | 40篇 |
2022年 | 26篇 |
2021年 | 22篇 |
2020年 | 38篇 |
2019年 | 61篇 |
2018年 | 45篇 |
2017年 | 56篇 |
2016年 | 30篇 |
2015年 | 35篇 |
2014年 | 76篇 |
2013年 | 63篇 |
2012年 | 45篇 |
2011年 | 76篇 |
2010年 | 57篇 |
2009年 | 67篇 |
2008年 | 53篇 |
2007年 | 72篇 |
2006年 | 39篇 |
2005年 | 51篇 |
2004年 | 49篇 |
2003年 | 20篇 |
2002年 | 16篇 |
2001年 | 16篇 |
2000年 | 21篇 |
1999年 | 13篇 |
1998年 | 22篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 17篇 |
1994年 | 14篇 |
1993年 | 12篇 |
1992年 | 9篇 |
1990年 | 5篇 |
1989年 | 2篇 |
1988年 | 5篇 |
1986年 | 1篇 |
1982年 | 1篇 |
1981年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有1206条查询结果,搜索用时 0 毫秒
1.
Ti(IV) as TiCl3(O3SCF3) and TiO(O2CCF3)2 are used as efficient catalysts for oxidative coupling of aliphatic, aromatic and heteroaromatic thiols to their disulfides in the presence of NaI under air atmosphere. 相似文献
2.
3.
掺杂SrTiO3体系上甲烷氧化偶联反应的研究—活性氧物种的作用 总被引:1,自引:0,他引:1
本文采用循环氧化还原法,脉冲反应及TPD等实验手段对钙钛矿型氧化物掺杂SrTiO_3体系上甲烷氧化偶联反应中的活性氧物种的作用进行了研究.结果表明,催化剂由于掺杂产生的未被充分还原的氧物种(O~(α-)(0<α<2)是活化甲烷并促使其发生偶联反应的主要的活性中心,而表面晶格氧(O_L~(2-))则主要使甲烷深度氧化;消耗掉的未被充分还原的氧或晶格氧可以在高温下氧气氛中氧化复原.对于掺杂的SrTiO_3样品,体相中的氧在惰性气氛或还原气氛中可以向表面扩散.吸附氧可能不直接与甲烷作用而主要通过催化剂表面活性氧物种(O~(α-)或O_L~(2-))而起作用. 相似文献
4.
脑神经退行性疾病中的有机化学-朊病毒(疯牛病)中的蛋白物理有机化学和自由基化学 总被引:5,自引:0,他引:5
杨池明 《高等学校化学学报》2002,23(2):243-250
通过关于“普里昂”蛋白病毒疾病的已有临床、医学生理、免疫和化学等方面的现象,讨论了朊病毒当中的部分蛋白氧化损伤和蛋白自由基化学本质。 相似文献
5.
The perfluorohexylated 3,4-ethylenedioxythiophene 5 was prepared via Mitsunobu reaction of perfluorohexylatyed diol 2 with diethyl 3,4-dihydroxythiophenedicarboxylate followed by decarboxylation. The polymerization of 5 was conducted with both oxidative chemical and electrochemical polymerizations. The polymers were characterized by cyclic voltammogram, UV, IR, TGA and DSC. 相似文献
6.
Wei Ge ZHANG Ying Hua JIN Ping QI Kai BAO Jin Guang LIN Nai Li WANG Xin Shen YAO 《中国化学快报》2006,17(1):9-11
Erythromycin has been extensively used in the treatment of bacterial infections for over 50 years1. In addition to the antimicrobial effect, the quite unique antiinflammatory activity of the erythromycin derivatives has attracted much attention as new the… 相似文献
7.
Kosuke Katagiri Yukina Yamamoto Yuui Takahata Ryoga Kishibe Naoki Fujimoto 《Tetrahedron letters》2019,60(30):2026-2029
Anthracenyl(diphenyl)phosphine oxide and dianthracenylphenylphosphine oxide as photoactive compounds have been synthesized. Anthracenyl group of these compounds indicate the multi-functional roles such as an emission component, a photodimerization component, and a leaving group. When the light irradiation was performed under an oxygen atmosphere, photo-oxidative PC bond cleavage to leave the antharacenyl group was observed. Moreover, phosphonyl radical was produced and then PP bond formation to form diphosphane was observed. 相似文献
8.
BODIPY dyes are privileged fluorophores that are now widely used in highly diverse research fields. An overview of BODIPY dyes and a summarization of the different synthetic methodologies reported for direct C-H functionalization of the BODIPY framework have been provided. 相似文献
9.
The structural composition of Nordic aquatic reference fulvic acid was investigated using chemical and thermal degradation methods: alkaline CuO oxidation and analytical pyrolysis after tetramethylammonium hydroxide (TMAH) pretreatment. Off-line procedures of the TMAH treatments were carried out under both air and helium atmospheres, with the aim of clarifying the effect of oxygen. Irrespective of the fact that the chemical and thermal degradation methods gave qualitatively quite similar basic products (mainly phenols and phenolic acids together with aromatic and aliphatic carboxylic acids), they also revealed their unique selectivity and efficiency for releasing different kinds of structural constituents. The results verify the formation of additional carboxyl functionality in the CuO oxidation. However, some similar oxidative reactions also appeared to take place during the pretreatment procedures of strongly basic TMAH, especially under an air atmosphere. The use of inert and protective atmosphere during the TMAH pretreatment is therefore recommended for producing more relevant structural information about the complex composition of humic substances. 相似文献
10.