全文获取类型
收费全文 | 375篇 |
免费 | 20篇 |
国内免费 | 73篇 |
专业分类
化学 | 431篇 |
晶体学 | 7篇 |
综合类 | 2篇 |
物理学 | 28篇 |
出版年
2023年 | 6篇 |
2022年 | 11篇 |
2021年 | 8篇 |
2020年 | 14篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 13篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 47篇 |
2012年 | 30篇 |
2011年 | 19篇 |
2010年 | 14篇 |
2009年 | 23篇 |
2008年 | 20篇 |
2007年 | 24篇 |
2006年 | 18篇 |
2005年 | 19篇 |
2004年 | 21篇 |
2003年 | 21篇 |
2002年 | 9篇 |
2001年 | 11篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1998年 | 4篇 |
1997年 | 7篇 |
1996年 | 3篇 |
1995年 | 8篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1967年 | 1篇 |
排序方式: 共有468条查询结果,搜索用时 234 毫秒
51.
合成了九种不同摩尔比的苯基苯甲酰甲基亚砜高氯酸镝、铥异核配合物,通过元素分析、稀土滴定确定其组成为(DyxTmy)L5(ClO4)3·2H2O(x∶y=1.000∶0.000,0.999∶0.001,0.995∶0.005,0.990∶0.010,0.900∶0.100,0.800∶0.200,0.700∶0.300,0.600∶0.400,0.500∶0.500,L=C6H5SOCH2COC6H5).红外光谱及摩尔电导表明,配体通过亚砜基上的氧原子与稀土离子配位,羰基氧不参与配位,三个ClO4-均在外界不参与配位.荧光光谱表明:当Tm3 的掺入量在0.001~0.300 mol之间时,对Dy3 的荧光有极强的敏化作用,且当Tm3 的掺入量为0.010 mol时,敏化强度最大,可使Dy3 荧光强度增加246%. 相似文献
52.
S. G. Kokoreva L. V. Shirshova N. V. Kir'yakov Yu. M. Shul'ga I. P. Lavrent'ev 《Russian Chemical Bulletin》2000,49(10):1722-1725
The products of interaction of components in the donor-acceptor electron-transport (DAET) DMSO−HBr system and their complex
formation with the metallic palladium surface were studied. H2O and Me2S (main reaction products) and CO, CS2, C2H6, MeBr, H, and CH4 (minor reaction products) were found in the gas phase by mass spectrometry (MS). The samples of metallic palladium treated
with the DAET system with a components ratio corresponding to the minimum and maximum rates of metal dissolution were studied
by the methods of thermoprogrammed desorption with MS detection (TPD-MS) and XPS. According to the TPD-MS data, two forms
of Me2S are present on the metal surface, whereas the XPS method detected two complexes with the molecular compositions PdIIBr4S1.26 and PdIIBr3.86S1.42. The addition of an aqueous solution of NaOH to the system results in the formation of HCOONa, which indicates that compounds
(CH2O, HCOOH) capable of reducing the palladium complexes are present in the DAET system.
Published inIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1740–1743, October, 2000. 相似文献
53.
Enzo Cadoni Massimiliano Arca Claudia Fattuoni Maria G. Cabiddu Salvatore Cabiddu 《Tetrahedron》2008,64(27):6349-6357
The sulfinyl carbanion derived from 2,3-dihydro-1-benzothiophene-1-oxide and its lithium salt has been investigated by DFT calculations. The lithium carbanion was treated with aldehydes and imines to give chiral hydroxy and amino derivatives, with high stereoselectivity at the carbon α to the sulfoxide group (trans diastereoisomers), but with low diastereoselectivity at the hydroxyl or amine group. DFT calculations were used to rationalize the different stereochemical behavior of cyclic and acyclic lithiated sulfoxides in the reaction with aldehydes and azomethines. 相似文献
54.
Some novel functionalized indeno[1,2-b]furans were synthesized from the reaction of indandione/indanone and aldehydes at room temperature followed by the reaction of the Knoevenagel condendensed intermediate with 4-hydroxycoumarins in the presence of iodine as catalyst in dimethyl sulfoxide (DMSO) under thermal conditions. The reaction involved in a condensation and Michael addition followed by lactone ring opening and intramolecular cyclization process to afford the product in high yield in easy work-up procedure. 相似文献
55.
Condensation of levoglucosenone with the carbanion ofrac-allyl phenyl sulfoxide, in contrast with reactions of this anion with the majority of other unsaturated ketones, proceeds
without regio- or enantioselectivity to give a (1.0–1.8): 1 mixture of products of both 1,2- and 1,4-γ-addition of the allylic
residue. Each product is a (1.2–1.6): 1 mixture of epimers at the asymmetric sulfur atom.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 157–159, January, 1999. 相似文献
56.
Guysolladi 《中国化学会会志》1990,37(6):525-533
The total synthesis of lasiodiplodin via optically active sulfoxides and the preparation of polyenes through low valent titanium reagents are described. 相似文献
57.
《Angewandte Chemie (International ed. in English)》2017,56(1):409-412
Heteroaromatic sulfoxides are a frequent structural motif in natural products, drugs, catalysts, and materials. We report a metal‐free visible‐light‐accelerated synthesis of heteroaromatic sulfoxides from sulfinamides and peroxodisulfate. The reaction proceeds at room temperature with blue‐light irradiation and allows the C−H sulfinylation of electron‐rich heteroarenes, such as pyrroles and indoles. An electrophilic aromatic substitution mechanism is proposed based on the substrate scope, substitution selectivity, and competition experiments with different nucleophiles. 相似文献
58.
Prof. Dr. Hideki Yorimitsu 《Chemical record (New York, N.Y.)》2017,17(11):1156-1167
A new class of Pummerer chemistry has emerged as a powerful tool in organic synthesis. The new technology consists of a beautiful cascade of an interrupted Pummerer reaction and the subsequent [3,3] sigmatropic rearrangement. The interrupted Pummerer reactions of alkenyl or aryl sulfoxides with unsaturated nucleophiles such as allylic silanes, ketones, and phenols provide sulfonium intermediates, which are ready to undergo smooth charge‐accelerated [3,3] sigmatropic rearrangement with excellent to exclusive regioselectivity. Some of the transformations proceed with transient loss of aromaticity. The reactions afforded five‐membered heterocycles, benzofurans, and biaryls of importance, depending on the sulfoxides and nucleophiles used. The reactions are unique and game‐changing because they are efficient, robust, redox‐neutral, regioselective, and metal‐free, which perfectly fits the need of modern organic synthesis. This chemistry also underscores the synthetic potential of organosulfur chemistry. 相似文献
59.
Molecular dynamics simulations of charged and neutral solutes in dimethyl sulfoxide (DMSO)-chloroform mixtures reveal pronounced nonideality in the solute diffusion with changes of composition of the mixtures. The diffusion coefficient of the anionic solute first decreases, passes through a minimum at DMSO mole fraction of about 0.50, and then increases to reach its value for pure DMSO. The diffusion coefficients of the cationic and neutral solutes are found to decrease with increase in DMSO content of the solvent mixture. The extent of nonideality in the diffusion and orientational relaxation of solvent molecules is found to be somewhat stronger than that in diffusion of the anionic solute in these mixtures. We have also calculated the relaxation of hydrogen bonds formed between DMSO and chloroform molecules. The lifetimes of DMSO-chloroform hydrogen bonds are found to increase monotonically with increase in DMSO concentration. The average number of hydrogen bonds and their average energies are also computed. It is found that an increase in DMSO concentration causes a decrease in the number of DMSO-chloroform hydrogen bonds per DMSO or chloroform molecules but increases the strength of these hydrogen bonds. 相似文献
60.