全文获取类型
收费全文 | 633篇 |
免费 | 20篇 |
专业分类
化学 | 541篇 |
晶体学 | 5篇 |
力学 | 4篇 |
数学 | 25篇 |
物理学 | 78篇 |
出版年
2023年 | 4篇 |
2022年 | 38篇 |
2021年 | 33篇 |
2020年 | 15篇 |
2019年 | 30篇 |
2018年 | 28篇 |
2017年 | 24篇 |
2016年 | 20篇 |
2015年 | 22篇 |
2014年 | 19篇 |
2013年 | 35篇 |
2012年 | 37篇 |
2011年 | 32篇 |
2010年 | 30篇 |
2009年 | 23篇 |
2008年 | 26篇 |
2007年 | 22篇 |
2006年 | 24篇 |
2005年 | 20篇 |
2004年 | 8篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 6篇 |
2000年 | 10篇 |
1999年 | 9篇 |
1998年 | 3篇 |
1997年 | 6篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 2篇 |
1992年 | 4篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 2篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 6篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 2篇 |
1969年 | 5篇 |
排序方式: 共有653条查询结果,搜索用时 15 毫秒
71.
Capturing C90 Isomers as CF3 Derivatives: C90(30)(CF3)14, C90(35)(CF3)16/18, and C90(45)(CF3)16/18 下载免费PDF全文
High‐temperature trifluoromethylation of a C90 isomeric mixture with CF3I followed by HPLC separation of C90(CF3)n isomers resulted in the isolation of several individual C90(CF3)14?18 compounds. Single crystal X‐ray diffraction with the use of synchrotron radiation resulted in the structure determination of C90(30)(CF3)14, C90(35)(CF3)16/18, and C90(45)(CF3)16/18. Their addition patterns are discussed and compared with the known isomers C90(30)(CF3)18 and C90(35)(CF3)14, respectively. The presence of the most stable C90 isomer, C90(45), in the fullerene soot has been confirmed for the first time. 相似文献
72.
73.
74.
75.
B. A. Izmaylov V. A. Vasnev V. I. Bregadze E. N. Rodlovskaya G. D. Markova 《Russian Chemical Bulletin》2017,66(5):899-902
New 1,7-bis(trialkoxysilylpropyl)-m-carboranedicarboxamides were synthesized by the reaction of 3-aminopropyltrialkoxysilanes with either m-carboranedicarboxylic acid chloride in the presence of Et3N or m-carboranedicarboxylic acid in the presence of N,N´-carbonyl-diimidazole. The synthesized compounds are colorless liquids soluble in benzene, toluene, tetrahydrofuran, diethyl ether, and chloroform and insoluble in water. Structures of the synthesized compounds were established by IR and NMR spectroscopy and confirmed by elemental analysis. The synthesized compounds are interesting starting materials for produc-tion of heat-resistant silicon carborane polymers and metal-carborane-silicon polymers. 相似文献
76.
M.?V.?Markova L.?N.?Sobenina I.?A.?Ushakov A.?V.?Ivanov B.?A.?TrofimovEmail author 《Russian Journal of Organic Chemistry》2017,53(2):184-191
Aminomethylation of 2-methyl(aryl)-, 2-aryl-3-alkylpyrroles, 4,5,6,7-tetrahydroindole and its 1-vinyl- and 1-benzyl-substituted derivatives with a mixture of 5% water-ethanol solution of formaldehyde and cyclic amine (pyrrolidine, piperazine, and morpholine) without catalyst at room temperature leads to the formation of the corresponding 2-aminomethylpyrroles and 2-aminomethyl-4,5,6,7-tetrahydroindoles in up to 92% yields. In reaction of 1-vinyl-4,5,6,7-tetrahydroindole with formaldehyde water solution and piperazine in a 60% yield 1,4-bis(1-vinyl-4,5,6,7-tetrahydroindol-2-yl)piperazine was obtained, a promising bifunctional monomer and a building block for the synthesis of new indole derivatives, in particular, of biologically active polymers. In the reaction of 2-methylpyrrole and 4,5,6,7-tetrahydroindole with formaldehyde and morpholine along with the С2-aminomethylation the 1-hydroxymethylation of the pyrrole ring was observed. 相似文献
77.
Georgi Chernev Nadezhda Rangelova Petar Djambazki Sanchi Nenkova Isabel Salvado Maria Fernandes Aiying Wu Lyudmila Kabaivanova 《Journal of Sol-Gel Science and Technology》2011,58(3):619-624
The purpose of the present work is the sol–gel synthesis, structure characterization and potential application of hybrid biomaterials
based on silica precursor (MTES) and natural polymers such as gelatin or pectin. The structure formation in the biomaterials
was investigated by XRD, FTIR, BET and AFM. The results showed that all studied hybrid biomaterials have an amorphous structure.
The FT-IR spectra of the obtained materials with MTES showed chemical bonds at 2,975, 1,255, 880 and 690 cm−1 due to the presence of Si–O–R (CH3 and C2H5) and Si–C bonds. In the samples synthesized with TEOS the inorganic and organic components interact by hydrogen bonding,
Van der Waals or electrostatic forces. Surface area of investigated samples decreases with increasing of the natural polymers
content. The structure evolution was studied by AFM and roughness analysis. Depending on the chemical composition a different
design and size of particles and their aggregates on the surface structure were established. The hybrid biomaterials were
used for immobilization of bacterial cells and applied in the biodegradation of the toxic compound 4-chlorobutyronitrile,
possible constituent of waste water effluents in a laboratory glass bioreactor. Optimization of the process at different temperatures
was carried out. 相似文献
78.
Oleg S. Radchenko Elena N. Sigida Nadezhda N. Balaneva Pavel S. Dmitrenok Vyacheslav L. Novikov 《Journal of heterocyclic chemistry》2011,48(1):209-214
Unusual course of the reaction was revealed on the oxidation of functionally substituted acridine containing the activated methyl groups by well‐known oxidants, such as selenous acid and selenium(IV) oxide. Treatment of 2‐methoxy‐4,9‐dimethyl‐1‐nitroacridine ( 5 ) with an excess of H2SeO3 in boiling ethanol gave a mixture of the normal reaction products, 2‐methoxy‐4‐methyl‐1‐nitro‐9‐formylacridine ( 11 ) (isolated yield 29%) and 2‐methoxy‐4‐methyl‐1‐nitroacridine‐9‐carboxylic acid ( 12 ) (36%), together with an abnormal product, 3‐methoxy‐5‐methyl‐1H‐selenopheno[2,3,4‐k,l]acridine‐1‐one ( 13 ) (21%), which is the first example of a new seleno‐containing ring system. With the use of SeO2 the yield of selenolactone 13 was much lower. J. Heterocyclic Chem., 2011. 相似文献
79.
Ivan V. Smolyaninov Natalia A. Antonova Susanna A. Smolyaninova Nadezhda T. Berberova 《Journal of organometallic chemistry》2011,696(13):2611-2620
The radical scavenging effect of the substituted catecholates (1-3, 6) and o-amidophenolates (4, 5) of triphenylantimony(V) in reactions with DPPH• radical and in a process of oleic acid peroxidation was studied in details. Complexes 1-6 show the high activity in radical scavenging reactions with DPPH• radical leading to disappearance of radical species. Complexes were demonstrated to be high-efficient inhibitors of chain-radical process of the peroxidation of oleic acid as well as the effective destructors of the formed hydroperoxides. It was found that the effectiveness of complexes studied in the inhibition of the peroxidation of oleic acid depends on the first oxidation potential of complex. 相似文献
80.
The work is devoted to the study of the complementarity of the electronic structures of the ligands and SARS-CoV-2 RNA-dependent RNA polymerase. The research methodology was based on determining of 3D maps of electron densities of complexes using an original quantum free-orbital AlteQ approach. We observed a positive relationship between the parameters of the electronic structure of the enzyme and ligands. A complementarity factor of the enzyme-ligand complexes has been proposed. The console applications of the AlteQ complementarity assessment for Windows and Linux (alteq_map_enzyme_ligand_4_win.exe and alteq_map_enzyme_ligand_4_linux) are available for free at the ChemoSophia webpage. 相似文献