全文获取类型
收费全文 | 270809篇 |
免费 | 2473篇 |
国内免费 | 655篇 |
专业分类
化学 | 144289篇 |
晶体学 | 4195篇 |
力学 | 12009篇 |
综合类 | 9篇 |
数学 | 30138篇 |
物理学 | 83297篇 |
出版年
2019年 | 2333篇 |
2018年 | 3154篇 |
2017年 | 3141篇 |
2016年 | 4540篇 |
2015年 | 2735篇 |
2014年 | 4342篇 |
2013年 | 10843篇 |
2012年 | 8228篇 |
2011年 | 10126篇 |
2010年 | 7189篇 |
2009年 | 6973篇 |
2008年 | 9509篇 |
2007年 | 9714篇 |
2006年 | 9082篇 |
2005年 | 8238篇 |
2004年 | 7575篇 |
2003年 | 6876篇 |
2002年 | 6797篇 |
2001年 | 7379篇 |
2000年 | 5705篇 |
1999年 | 4431篇 |
1998年 | 3907篇 |
1997年 | 3898篇 |
1996年 | 3644篇 |
1995年 | 3361篇 |
1994年 | 3531篇 |
1993年 | 3235篇 |
1992年 | 3699篇 |
1991年 | 3700篇 |
1990年 | 3634篇 |
1989年 | 3489篇 |
1988年 | 3594篇 |
1987年 | 3487篇 |
1986年 | 3304篇 |
1985年 | 4390篇 |
1984年 | 4678篇 |
1983年 | 3902篇 |
1982年 | 4035篇 |
1981年 | 3976篇 |
1980年 | 3936篇 |
1979年 | 3904篇 |
1978年 | 4219篇 |
1977年 | 4136篇 |
1976年 | 4203篇 |
1975年 | 3869篇 |
1974年 | 3926篇 |
1973年 | 4069篇 |
1972年 | 2869篇 |
1971年 | 2385篇 |
1970年 | 2181篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
The electron-impact mass spectra of a number of phenylpropanoids and iridoid glycosides containing a phenylethanoid fragment in their structure have been studied. This has revealed features of the formation of fragments of 4-hydroxyphenylethyl and 3,4-dihydroxyphenylethyl alcohols and also of fragments of phenylethylamine and indolylethylamine derivatives present in the structures of the compounds investigated. 相似文献
142.
143.
D. Kh. Khalikov M. G. Mukhiddinov M. G. Asoev V. A. Degtyarev 《Chemistry of Natural Compounds》1994,30(6):734-738
Some features of the kinetics of the hydrolysis of apple protopectin have been studied on the basis of an analysis of monosaccharide residues of the pectin substances and determinations of characteristic viscosity. It has been shown that the fine regulation of the physicochemical parameters of the hydrolysis of protopectin leads to the formation of pectin substances with different properties. 相似文献
144.
145.
Literature information on the formation, chemical composition, and structural features of lignins of herbaceous plants for
1980–1992 is generalized and analyzed.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Fax (3712) 62
73 48. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 160–177, March–April, 1994. 相似文献
146.
D. N. Dalimov M. B. Gafurov Z. Tilyabaev F. G. Kamaev A. A. Abdugakhabov 《Chemistry of Natural Compounds》1994,30(1):61-64
The synthesis has been effected of alkyl anabasinoprop-2-yl and alkyl piperidinoprop-2-yl methylphosphonothionates. It has been shown by1H,13C and31P NMR spectroscopies that the anabasine derivatives exist in solution as four diastereomeric forms. The kinetics of the interaction of the compounds synthesized with two types of cholinesterases has been studied.A. S. Sadykov Institute of Bioorganic Chemistry, Academy of Sciences of the Republic of Uzbekistan, Tashkent, Fax 627071. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 70–74, January–February, 1994. 相似文献
147.
148.
Chromatographia - An LC-MS method is described for the determination of 4,4′-MDA (4,4′-methylene dianiline) in hydrolysed urine as a biomarker for exposure to 4,4′-MDI... 相似文献
149.
150.
The copolymerization of methyl methacrylate and methacrylic acid in isopropyl alcohol is studied by kinetic, dynamic laser scattering and 13C-NMR methods. Correlations are established between the dependence of the copolymerization rate, the apparent average molecular weight, the diffusion coefficients and the configurational triad composition on the monomer feed. These correlations and the fact that both copolymerization constants are smaller than unity (rMMA = 0.63 ± 0.03; rMA = 0.25 ± 0.05) are in good agreement with the assumption that a comonomer complex takes part in the propagation reaction. A new Markov chain method for the estimation of the configurational triad mole fraction which accounts for the complex participation in a macromolecule formation is developed. Qualitative criteria for evidence the participation of the comonomer complex in copolymerization are proposed using experimental and terminal model calculated mole fractions of the compositional triads and diads. 相似文献