全文获取类型
收费全文 | 226187篇 |
免费 | 1619篇 |
国内免费 | 543篇 |
专业分类
化学 | 105968篇 |
晶体学 | 3401篇 |
力学 | 10310篇 |
综合类 | 10篇 |
数学 | 21993篇 |
物理学 | 64915篇 |
无线电 | 21752篇 |
出版年
2021年 | 2196篇 |
2020年 | 2275篇 |
2019年 | 2908篇 |
2018年 | 3990篇 |
2017年 | 3982篇 |
2016年 | 5265篇 |
2015年 | 2537篇 |
2014年 | 4747篇 |
2013年 | 9323篇 |
2012年 | 7357篇 |
2011年 | 8639篇 |
2010年 | 7028篇 |
2009年 | 7462篇 |
2008年 | 8610篇 |
2007年 | 8648篇 |
2006年 | 7708篇 |
2005年 | 6925篇 |
2004年 | 6558篇 |
2003年 | 6023篇 |
2002年 | 5972篇 |
2001年 | 6431篇 |
2000年 | 4955篇 |
1999年 | 3895篇 |
1998年 | 3360篇 |
1997年 | 3418篇 |
1996年 | 3088篇 |
1995年 | 2775篇 |
1994年 | 2848篇 |
1993年 | 2746篇 |
1992年 | 3037篇 |
1991年 | 3155篇 |
1990年 | 3081篇 |
1989年 | 3087篇 |
1988年 | 2951篇 |
1987年 | 2791篇 |
1986年 | 2643篇 |
1985年 | 3338篇 |
1984年 | 3350篇 |
1983年 | 2803篇 |
1982年 | 2727篇 |
1981年 | 2666篇 |
1980年 | 2472篇 |
1979年 | 2810篇 |
1978年 | 2778篇 |
1977年 | 2956篇 |
1976年 | 2958篇 |
1975年 | 2743篇 |
1974年 | 2677篇 |
1973年 | 2796篇 |
1972年 | 2138篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
972.
973.
R.R. Adžić D.N. Simić A.R. Despić D.M. Dražić 《Journal of Electroanalytical Chemistry》1975,65(2):587-601
It was demonstrated that some foreign metal monolayers formed by underpotential deposition have pronounced catalytic effects on the oxidation of formic acid on platinum. The explanation of these effects was sought within the framewor of existing data on the formic acid oxidation and the underpotential deposition. It was found that the catalytic effect of foreign metal monolayers originates in the decrease of hydrogen adsorption thus preventing the formation of the main poisoning species COH. At the same time these experiments confirm the previously postulated mechanism of formation of the poisoning species involving adsorbed hydrogen. 相似文献
974.
N. M. Mukhamedshina A. A. Mirsagatova N. M. Bekmukhamedova Kh. M. Khamidova 《Journal of Radioanalytical and Nuclear Chemistry》2005,263(3):641-643
Summary INAA was applied for searching more effective biosorbents for U and Ag among 9 and 47 strains of actinomyces, respectively. Biomasses of strains were tested for the Ag and U sorption capacity from model solution, containing 50 mg/l Ag ions and from technological solution of U-production, containing 7.11 mg/l U ions. The U and Ag samples were irradiated for 5 hours and 20 hours, respectively, at a neutron flux density of 5.3 . 1013 n . cm-2 . s-1. The Ag content was calculated from the gamma-line of radionuclide 110mAg (T1/2 = 250.4d, Eγ= 657.7keV). The U content was calculated from the gamma-lines (228.2 keV, 277.8 keV) of radionuclide 239Np (T1/2 = 2.35 d). The error of U and Ag determination (relative standard deviation) was 2-3%. 相似文献
975.
N. S. Magomedova A. N. Sobolev V. K. Belskii A. M. Koroteev M. P. Koroteev É. E. Nifantiev 《Journal of Structural Chemistry》1994,34(4):627-633
The structures of dioxaphosphepane (I) and dioxaphosphecane (II) salts prepared by hydrolysis of the corresponding bicyclophosphates have been compared. In both cases, hydrolysis occurs with breaking of the P–O bond of the fragment at the secondary carbon atom of bicyclophosphate. In phosphocycles I and II, the endocyclic bond angles O–P–O are 104.2 and 104.9°, and the exocyclic ones are 117.7 and 118.6°, respectively. Conformations of the anions in I and II differ substantially: for I it is a twist conformationC1TC4, and for II a distorted armchair. The data obtained are compared with those found earlier for similar molecules.Moscow State Pedagogical University. Translated fromZhurnal Strukturnoi Khimii, Vol. 34, No. 4, pp. 154–160, July–August, 1993.Translated by T. Yudanova 相似文献
976.
A method is presented for simultaneous separation of traces of toxic and essential elements from soils. The method is based on programmed vacuum-thermic extraction of the elements in an oxidation-reduction medium. Under optimal conditions of temperature and pressure Pb, Zn, Cd, Bi, Tl, As, Sb, Te, Mo, Hg and Re are distilled or sublimated in elementary state or as oxides. A simple quartz apparatus is proposed. The elements extracted from matrix are dissolved in nitric acid and determined by AAS or OES with ICP excitation. 相似文献
977.
978.
979.
Synthesis of 1,7-bis(4′-aminophenylamido)-m-carborane and 1,7-bis(4′-aminophenylcarboxy)-m-carborane
V. V. Korshak L. G. Komarova N. G. Komarova V. V. Vagin G. A. Kats 《Russian Chemical Bulletin》1986,35(12):2554-2555
Conclusion 1,7-Bis(4-aminophenylamido)- and l,7-bis(4-aminophenylcarboxy)-m-carboranes were prepared and characterized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2786–2787, December, 1986. 相似文献
980.
V. P. Kruglenko N. S. Patalakha P. B. Kurapov N. A. Klyuev V. A. Idzikovskii I. I. Grandberg M. V. Povstyanoi 《Chemistry of Heterocyclic Compounds》1985,21(5):587-593
The synthesis has been effected of new representatives of the imidazo[1,2-b]-1,2,4-triazepin-4-ones (-thiones). It has been shown with the aid of IR and UV spectroscopic and mass spectrometric methods that the lactam (thione) form is the predominant one for the compounds synthesized.For Communication 11, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 694–699, May, 1985. 相似文献