全文获取类型
收费全文 | 232905篇 |
免费 | 2250篇 |
国内免费 | 800篇 |
专业分类
化学 | 116929篇 |
晶体学 | 3999篇 |
力学 | 10761篇 |
综合类 | 1篇 |
数学 | 25512篇 |
物理学 | 78753篇 |
出版年
2020年 | 1790篇 |
2019年 | 2044篇 |
2018年 | 2719篇 |
2017年 | 2651篇 |
2016年 | 3913篇 |
2015年 | 2392篇 |
2014年 | 3967篇 |
2013年 | 10075篇 |
2012年 | 7538篇 |
2011年 | 9404篇 |
2010年 | 6686篇 |
2009年 | 6631篇 |
2008年 | 8703篇 |
2007年 | 8735篇 |
2006年 | 8276篇 |
2005年 | 7494篇 |
2004年 | 6921篇 |
2003年 | 6114篇 |
2002年 | 6065篇 |
2001年 | 7097篇 |
2000年 | 5373篇 |
1999年 | 4244篇 |
1998年 | 3563篇 |
1997年 | 3473篇 |
1996年 | 3295篇 |
1995年 | 3010篇 |
1994年 | 2951篇 |
1993年 | 3043篇 |
1992年 | 3154篇 |
1991年 | 3333篇 |
1990年 | 3085篇 |
1989年 | 3028篇 |
1988年 | 3066篇 |
1987年 | 2955篇 |
1986年 | 2801篇 |
1985年 | 3810篇 |
1984年 | 4006篇 |
1983年 | 3201篇 |
1982年 | 3413篇 |
1981年 | 3340篇 |
1980年 | 3231篇 |
1979年 | 3340篇 |
1978年 | 3423篇 |
1977年 | 3354篇 |
1976年 | 3451篇 |
1975年 | 3145篇 |
1974年 | 3152篇 |
1973年 | 3196篇 |
1972年 | 2237篇 |
1971年 | 1854篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
L. K. Aminov I. N. Kurkin D. A. Lukoyanov K. P. Chernov 《Physics of the Solid State》1997,39(8):1184-1186
Results are reported for measurements of the spin-lattice relaxation times of E′1 centers in quartz glass, produced by neutron irradiation, with the measurements made at two frequencies 9.25 and 24.0 GHz
over a wide temperature interval 1.5–300 K. The experimental data are interpreted on the basis of interaction mechanisms of
the spins with two-level systems with excitation energies ∼6, ∼26, and ∼420 cm−1. A small modification of the existing theory allows us to explain a number of features of the observed temperature and frequency
dependence of the relaxation rate. The results are compared with the data available in the literature on spin-lattice relaxation
of irradiation centers in crystalline quartz and quartz glass.
Fiz. Tverd. Tela (St. Petersburg) 39, 1335–1337 (August 1997) 相似文献
104.
J. E. Fischer E. Werwa P. A. Heiney 《Applied Physics A: Materials Science & Processing》1993,56(3):193-196
We have used both reflection-geometry and grazing-incidence-geometry X-ray scattering to study thin films of C60 evaporated onto mica substrates via a hot-wall technique. The growth mode yields close-packed C60 planes, which are parallel to the substrate surface and which exhibit out-of-plane correlation lengths of 850 Å. In the film plane the C60 is at best pseudo-epitaxial, with a 0.9° distribution of crystallite orientations, a 450 Å in-plane correlation length, and a 3.7% lattice mismatch, better than obtained by other thin film techniques but far from the accepted definition of single crystal thin film epitaxy. 相似文献
105.
I. V. Ukrainets S. G. Taran O. V. Gorokhova P. A. Bezuglyi A. V. Turov 《Chemistry of Heterocyclic Compounds》1994,30(2):204-207
In a solution of DMF, 2-carbethoxymethyl-4H-3,1-benzoxazin-4-one reacts with primarily aromatic amines basically with the formation of the corresponding 2-carbethoxymetlzyl-3-arylquinazolin-4(3H)-ones. Possible mechanisms of these chemical transformations are reported and discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 225–228, February, 1994. Original article submitted June 28, 1993. 相似文献
106.
Molecular n-v complexes of quinoline N-oxides with BF3 have been studied by electronic and IR spectroscopy. In most case the donor centre is the oxygen atom of the N-oxide group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1087–1092, August, 1994. 相似文献
107.
V. D. Orlov Z. Kaluski N. P. Borob'eva E. Figas A. A. Tishchenko F. G. Yaremko 《Chemistry of Heterocyclic Compounds》1994,30(8):964-971
We have measured the PMR spectra of 5, 7-diaryl-1, 4-diazabicyclo[4. ].O]hept-4-enes. We have studied the structure of the 5-(4-nitrophenyl)-7-phenyl derivative by x-ray diffraction. We show that the six-membered heterocycle has the half-chair form. The 6-H and 7-H protons of the aziridine ring are trans, while the 7-aryl is exo relative to the six-membered ring. Introduction of substituents into the aromatic ring has practically no effect on the geometry of the bicycle.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1117–1124, August, 1994.For Communication 11, see [1]. 相似文献
108.
A. Sh. Isamukhamedov N. P. Goncharova A. I. Glushetskova 《Chemistry of Natural Compounds》1994,30(2):170-174
The influence of sunflowerseed and cottonseed oils and also of fractions of normal and oxidized triacylglycerols isolated from them on cytochrome P-450 from rat liver microsomes has been investigated. 相似文献
109.
A. Aitmambetov S. N. Shinkaruk S. P. Bondarenko V. P. Khilya 《Chemistry of Natural Compounds》1994,30(4):453-456
6-Halogeno-1,3-benzodioxane analogs of chalcones have been synthesized by various methods. Flavanone and flavone analogs of silandrin and hydnocarpin have been obtained from them. The structures of the new flavonoids have been shown by their PMR spectra. 相似文献
110.
A. N. Komissarenko T. P. Nadezhina N. F. Komissarenko 《Chemistry of Natural Compounds》1994,30(4):521-522
State Scientific Center for Drugs, Khar'kov. Ukrainian Pharmaceutical Academy, Khar'kov. Botanical Gardem, Russian Academy
of Sciences, St. Petersburg. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 564–565, July–August, 1994. 相似文献