全文获取类型
收费全文 | 353篇 |
免费 | 13篇 |
国内免费 | 9篇 |
专业分类
化学 | 240篇 |
晶体学 | 1篇 |
力学 | 12篇 |
数学 | 21篇 |
物理学 | 101篇 |
出版年
2023年 | 1篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 17篇 |
2019年 | 12篇 |
2018年 | 16篇 |
2017年 | 8篇 |
2016年 | 17篇 |
2015年 | 10篇 |
2014年 | 17篇 |
2013年 | 36篇 |
2012年 | 28篇 |
2011年 | 28篇 |
2010年 | 26篇 |
2009年 | 17篇 |
2008年 | 17篇 |
2007年 | 12篇 |
2006年 | 22篇 |
2005年 | 11篇 |
2004年 | 11篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 1篇 |
2000年 | 1篇 |
1999年 | 4篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1986年 | 1篇 |
1984年 | 3篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1980年 | 4篇 |
排序方式: 共有375条查询结果,搜索用时 0 毫秒
121.
Issa Yavari Ramin Pashazadeh Reza Hosseinpour Ehsan Ghanbari 《Helvetica chimica acta》2013,96(12):2191-2195
An efficient synthesis of alkyl 5‐(alkylimino)‐3‐aryl(alkyl)‐2‐(dicyanomethylene)‐4‐hydroxythiazolidine‐4‐carboxylates, containing polarized C?C bonds, via reaction of malononitrile, arylisothiocyanates, and the Nef‐isocyanide adducts, under basic conditions, is described. 相似文献
122.
Javad Azizian Ramin Miri Mohammad Kazem Mohammadi Fatemeh Sheikholeslami Farahani Javad Hosseini Mohsen Nikpour 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1782-1787
New (pyrimido[4,5-e][1,3,4]thiadiazin-7-yl)hydrazines were synthesized via the cyclocondensation of alkyl-2-phenylhydrazinecarbodithioates as bidentate nucleophiles with 5-bromo-2,4-dichloro-6-methylpyrimidine as an electrophile and further replacement of chlorine atom on the seven number position of pyrimido[4,5-e][1,3,4]thiadiazin by hydrazine in boiling ethanol. 相似文献
123.
A new solid-phase microextraction fiber based on alumina/titania sol-gel-coated on copper wire for headspace sampling of chlorinated organic solvents (chloroform, carbon tetrachloride, trichloroethene, and tetrachloroethene) from urine samples is introduced. The influences of fiber coating composition and microextraction conditions (extraction temperature, extraction time, and ionic strength of the sample matrix) on the fiber performance were investigated. Also, the influence of temperature and time on desorption of analytes from fiber was studied. The proposed fiber has high capacity and demonstrates fast sampling of chlorinated organic solvents from urine samples with high sensitivity. The relative standard deviation (RSD, n=5) for all analytes was below 6.5%. 相似文献
124.
125.
Ramin Ghorbani-Vaghei Ardeshir Khazaei 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6):1169-1173
N-Bromobis(p-toluenesulfonyl)amine (NBBTA) is a novel and efficient reagent for the conversion of oximes to their corresponding carbonyl compounds in good yields under mild conditions. 相似文献
126.
Hemmateenejad B Akhond M Miri R Shamsipur M 《Journal of chemical information and computer sciences》2003,43(4):1328-1334
127.
The complex [Cu(nitroca2ph)2]ClO4, where nitroca2ph is N,N′‐bis(2‐nitrocinnamaldehyde)phenylenediimine, crystallizes in the triclinic space group with a = 13.167(1), b = 13.209(1), c = 14.465(1) Å, α = 83.209(9)°, β = 68.438(2)°, γ = 70.803(2)°, V = 2209.4(3) Å3, Z = 2, Dcalc = 1.527 mg/m3. The coordination polyhedron about the Cu(I) atom is best described as a distorted tetrahedron. 2‐nitroca2en acts as a bidentate ligand coordinating via two N atoms to the copper. The four Cu–N distances are 2.04 (2), 2.038(2), 2.046(2), and 2.062(2) Å. 相似文献
128.
129.
Hosseinzadeh R Maleki R Matin AA Nikkhahi Y 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2008,69(4):1183-1187
Solubilization and interaction of azo-dye light yellow (X6G) at/with cationic surfactants cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC) was investigated spectrophotometricaly. The effect of cationic micelles on solubilization of anionic azo dye in aqueous micellar solutions of cationic surfactants was studied at pH 7 and 25 degrees C. The binding of dye to micelles implied a bathochromic shift in dye absorption spectra that indicates dye-surfactant interaction. The results showed that the solubility of dye increased with increasing surfactant concentration, as a consequence of the association between the dye and the micelles. The binding constants, K(b), were obtained from experimental absorption spectra. By using pseudo-phase model, the partition coefficients between the bulk water and surfactant micelles, K(x), were calculated. Gibbs energies of binding and distribution of dye between the bulk water and surfactant micelles were estimated. The results show favorable solubilization of dye in CTAB micelles. 相似文献
130.