全文获取类型
收费全文 | 397841篇 |
免费 | 4488篇 |
国内免费 | 1793篇 |
专业分类
化学 | 219935篇 |
晶体学 | 6446篇 |
力学 | 16233篇 |
综合类 | 72篇 |
数学 | 42600篇 |
物理学 | 118836篇 |
出版年
2020年 | 3277篇 |
2019年 | 3596篇 |
2018年 | 4446篇 |
2017年 | 4567篇 |
2016年 | 6742篇 |
2015年 | 4373篇 |
2014年 | 6695篇 |
2013年 | 17056篇 |
2012年 | 13366篇 |
2011年 | 16316篇 |
2010年 | 11584篇 |
2009年 | 11436篇 |
2008年 | 15022篇 |
2007年 | 14989篇 |
2006年 | 14056篇 |
2005年 | 12803篇 |
2004年 | 11528篇 |
2003年 | 10392篇 |
2002年 | 10100篇 |
2001年 | 11858篇 |
2000年 | 9049篇 |
1999年 | 6741篇 |
1998年 | 5441篇 |
1997年 | 5364篇 |
1996年 | 5304篇 |
1995年 | 4777篇 |
1994年 | 4774篇 |
1993年 | 4516篇 |
1992年 | 5327篇 |
1991年 | 5287篇 |
1990年 | 5053篇 |
1989年 | 5027篇 |
1988年 | 4962篇 |
1987年 | 4917篇 |
1986年 | 4765篇 |
1985年 | 6244篇 |
1984年 | 6334篇 |
1983年 | 5143篇 |
1982年 | 5431篇 |
1981年 | 5260篇 |
1980年 | 4851篇 |
1979年 | 5351篇 |
1978年 | 5510篇 |
1977年 | 5657篇 |
1976年 | 5489篇 |
1975年 | 5029篇 |
1974年 | 5086篇 |
1973年 | 5107篇 |
1972年 | 3780篇 |
1968年 | 3228篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Devyatkina T. I. Gun'ko Yu. L. Mikhalenko M. G. 《Russian Journal of Applied Chemistry》2001,74(7):1122-1125
The influence exerted by addition of -hydroxynaphthoic acid and combined additive Hg + Pb + -hydroxynaphthoic acid on the corrosion and self-discharge of a porous zinc electrode in alkali solution was studied. 相似文献
992.
Yaroshenko A. P. Savos'kin M. V. Magazinskii A. N. Galushko L. Ya. 《Russian Journal of Applied Chemistry》2004,77(2):192-195
The influence exerted by the particle size and the distribution of sol impurities in the initial graphite, and also by pyrite additives, on the properties of residual graphite hydrosulfates synthesized by oxidation in the CrO3-H2SO4 system was studied. 相似文献
993.
994.
The composition and structure of films formed in etching of nickel in a Ni(NO3)2 solution in the presence of Cl- and NO2
- ions was studied. 相似文献
995.
S. Patzer N.L. Arthur P. Potzinger H.Gg. Wagner 《Journal of photochemistry and photobiology. A, Chemistry》1997,110(3):2543-227
The photolysis of Me6Si2 at 206 nm results in two main decomposition processes: simple Si---Si bond breaking with a quantum yield of Φ = 0.21 ± 0.03, and Me3SiH elimination with the concomitant formation of Me2SiCH2 with Φ = 0.18 ± 0.01. There is also a minor decomposition channel with a very small quantum yield, Φ = (5.6 ± 0.2) × 10−3, which results in the formation of Me4Si and Me2Si. The main fate of the excited Me6Si2 molecule produced during photolysis is stabilization by collisional deactivation. The end products observed indicate that the reaction pathways followed by the main intermediates, Me3Si and Me2SiCH2, are the same as those found in the photolysis of Me4Si (Ahmed et al., J. Photochem. Photobiol. A: Chem. 86 (1995) 33). 相似文献
996.
S. L. Bogza K. I. Kobrakov M. Yu. Zubritskii S. Yu. Suikov V. I. Dulenko 《Chemistry of Heterocyclic Compounds》1997,33(1):74-77
Treatment of N-phenyl-2-(1-R-indol-3-yl)succinimides with acetyl perchlorate leads to acylation of the benzene ring of the indole substituent.L. M. Litvinenko Institute of Physico-Organic and Carbon Chemistry, Ukrainian Academy of Sciences, Donetsk 340114. A. N. Kosygin State Textile Academy, Moscow 117918, GSP-1. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 85–88, January, 1997. 相似文献
997.
I. K. Buchina O. Kh. Kholbekov A. A. Abduvakhabov 《Chemistry of Natural Compounds》1994,30(1):121-123
The synergisic properties of docosa-5Z, 17Z-diene — one of the by-products of the synthesis of the synthetic cotton bollworm pheromone — have been revealed.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. 130–132, January–February, 1994. 相似文献
998.
999.
A carborane-containing stable simple enol — 1-2-isopropyl-o-carboran-I-yl)-1-phenyl2-mesityl-2-lrydroxyctlrylcne — has been synthesized. This enol does not isomerize to the starting ketone or keto-enol mixture even after prolonged heating in benzene in the presence of CF3COOH.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1561–1563, June, 1996. 相似文献
1000.
A paradox was observed in a previous study of the electrophoresis of linear DNA fragments in agarose gels (D. L. Holmes and N. C. Stellwagen, Electrophoresis 1990, 11, 5-15). The pore size of the agarose matrix was more accurately determined if the root-mean-square radius of gyration was used to measure DNA macromolecular size. However, the Ogston equations were obeyed and other gel parameters such as the apparent fiber radius and fiber volume appeared to be better described if the geometric mean radius was used to measure DNA size. This paradox can be resolved if relative mobilities (with respect to the smallest DNA molecule in the data set) are used to construct the Ferguson plots, instead of absolute mobilities. Using relative mobilities and the root-mean-square radius of gyration, the Ogston equations are obeyed and the pore size of the matrix is consistent with values determined by other methods. 相似文献