全文获取类型
收费全文 | 497092篇 |
免费 | 3494篇 |
国内免费 | 1386篇 |
专业分类
化学 | 242829篇 |
晶体学 | 7509篇 |
力学 | 27109篇 |
综合类 | 18篇 |
数学 | 79560篇 |
物理学 | 144947篇 |
出版年
2020年 | 3598篇 |
2019年 | 4245篇 |
2018年 | 15884篇 |
2017年 | 15732篇 |
2016年 | 14038篇 |
2015年 | 5317篇 |
2014年 | 7931篇 |
2013年 | 17844篇 |
2012年 | 16886篇 |
2011年 | 25965篇 |
2010年 | 17379篇 |
2009年 | 17734篇 |
2008年 | 21333篇 |
2007年 | 23459篇 |
2006年 | 14098篇 |
2005年 | 13644篇 |
2004年 | 13059篇 |
2003年 | 12437篇 |
2002年 | 11414篇 |
2001年 | 11776篇 |
2000年 | 9103篇 |
1999年 | 6952篇 |
1998年 | 6107篇 |
1997年 | 6141篇 |
1996年 | 5738篇 |
1995年 | 5180篇 |
1994年 | 5347篇 |
1993年 | 5048篇 |
1992年 | 5700篇 |
1991年 | 5753篇 |
1990年 | 5606篇 |
1989年 | 5526篇 |
1988年 | 5556篇 |
1987年 | 5438篇 |
1986年 | 5189篇 |
1985年 | 6761篇 |
1984年 | 7099篇 |
1983年 | 5915篇 |
1982年 | 5989篇 |
1981年 | 5913篇 |
1980年 | 5704篇 |
1979年 | 5979篇 |
1978年 | 6265篇 |
1977年 | 6308篇 |
1976年 | 6329篇 |
1975年 | 5878篇 |
1974年 | 5882篇 |
1973年 | 6142篇 |
1972年 | 4440篇 |
1971年 | 3867篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
Shahkel'dyan I. V. Melekhina E. K. Atroshchenko Yu. M. Efremov Yu. A. Alifanova E. N. Kopyshev M. V. Troitskii N. A. Subbotin V. A. Nikishina M. B. 《Russian Journal of Organic Chemistry》2003,39(4):589-595
A series of 7-carboxy-3-R-1,5-dinitro-3-azabicyclo[3.3.1]non-6-enes was synthesized by reduction of 3,5-dinitrobenzoic acid with sodium borohydride followed by Mannich reaction with formaldehyde and primary amines. The mechanism of decomposition under electron impact of the 3-azabicyclo[3.3.1]nonane was established. Enthalpies of formation of compounds synthesized were calculated by semiempirical PM3 method. 相似文献
993.
Ten'kovtsev A. V. Trofimov A. E. Dudkina M. M. Lukoshin V. N. 《Russian Journal of Applied Chemistry》2003,76(4):591-594
The influence exerted by the length exerted by the conjugation chain in 4-hydroxybenzylidenealkanones on the generation of the third harmonic by complexes of these chromophores with aliphatic polyamidine was studied. 相似文献
994.
995.
996.
Yarovenko V. N. Kosarev S. A. Zavarzin I. V. Krayushkin M. M. 《Russian Chemical Bulletin》2002,51(8):1504-1509
Carbamoylformhydroxymoyl chlorides were synthesized by the reactions of carbamoylformamide oximes with sodium nitrite in the presence of hydrochloric acid, and their reactivities were examined. 相似文献
997.
Shul'ga Yu. M. Chernushevich I. V. Dzhardimalieva G. I. Roshchupkina O. S. Dodonov A. F. Pomogailo A. D. 《Russian Chemical Bulletin》1994,43(6):983-987
Russian Chemical Bulletin - The monomer [Cr3O(OCOCH=CH2)6]OH was produced by reaction of acrylic acid with fresh chromium hydroxide. This monomer was investigated by a number of physicochemical... 相似文献
998.
A. V. Borovkov Yu. N. Brusil'tsev A. O. Doroshenko 《Theoretical and Experimental Chemistry》1993,28(4):269-273
An investigation was carried out of the spectral-luminescent and acid-base properties at the stage of formation of the hydrogen bond and during the protonation of compounds with annelated aromatic and heterocyclic rings, obtained by introduction of bridging groups -CH=CH- (I), -CH=N- (II) and -CO-N(CH3)-(III) in the 4- and 2-positions of the molecules of 4-substituted derivatives of 2,5-diphenyloxazole. The nature of the reaction center was estabished, and an analysis was carried out of its sensitivity to the electronic influence of the substituents, and the reasons for the observed differences in the properties of compounds of various reaction series are discussed. A comparative analysis of the fluorescent properties of the neutral and protonated forms of the oxazole derivatives studied was made and the conclusion that the generation is possible of laser emission by the protonated forms of compounds of the reaction series (I) was confirmed.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 28, No. 4, pp. 343–349, July–August, 1992. 相似文献
999.
1000.
Burakov VS Lobazov AF Nechaev SV Raikov SN 《Analytical and bioanalytical chemistry》1996,355(3-4):364-366
A polarization variant of an intracavity laser spectrometer based on the competition of beams in an argon ion laser, radiating a number of narrow lines in the 275 to 529 nm spectral range, is proposed and described for the spectral analysis of liquid samples, having broad absorption bands, mainly biomolecules in solutions. By careful optimization of the operating conditions, a procedure has been established that results in a minimal measurable absorbance decreased up to 10(-5) units of optical density. The examined spectrometer provides a wide dynamic range of analysis. A determination of trace contents of amino acids in methanol were carried out. 相似文献