全文获取类型
收费全文 | 299780篇 |
免费 | 1360篇 |
国内免费 | 326篇 |
专业分类
化学 | 137661篇 |
晶体学 | 4660篇 |
力学 | 16911篇 |
综合类 | 3篇 |
数学 | 42247篇 |
物理学 | 99984篇 |
出版年
2021年 | 3099篇 |
2020年 | 3418篇 |
2019年 | 4196篇 |
2018年 | 6248篇 |
2017年 | 6470篇 |
2016年 | 7971篇 |
2015年 | 3553篇 |
2014年 | 6907篇 |
2013年 | 12188篇 |
2012年 | 10158篇 |
2011年 | 11865篇 |
2010年 | 10006篇 |
2009年 | 10150篇 |
2008年 | 11489篇 |
2007年 | 11269篇 |
2006年 | 10050篇 |
2005年 | 8644篇 |
2004年 | 8398篇 |
2003年 | 7805篇 |
2002年 | 8086篇 |
2001年 | 7689篇 |
2000年 | 6088篇 |
1999年 | 4506篇 |
1998年 | 4278篇 |
1997年 | 4135篇 |
1996年 | 3744篇 |
1995年 | 3319篇 |
1994年 | 3378篇 |
1993年 | 3394篇 |
1992年 | 3396篇 |
1991年 | 3798篇 |
1990年 | 3800篇 |
1989年 | 3815篇 |
1988年 | 3558篇 |
1987年 | 3648篇 |
1986年 | 3351篇 |
1985年 | 3884篇 |
1984年 | 4110篇 |
1983年 | 3514篇 |
1982年 | 3709篇 |
1981年 | 3389篇 |
1980年 | 3155篇 |
1979年 | 3640篇 |
1978年 | 3714篇 |
1977年 | 3875篇 |
1976年 | 3950篇 |
1975年 | 3697篇 |
1974年 | 3540篇 |
1973年 | 3703篇 |
1972年 | 3193篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
V. V. Ilyasov 《Russian Physics Journal》1997,40(6):574-578
An analysis is made of the thermodynamic stability of the dislocation structure in polycrystalline samples of Fe-C, deformed
under conditions of high rates and hydrostatic pressures, based on experimental and theoretical data concerning the internal
energy and on diffractometer measurements of the broadening of x-ray lines. The method of deformation calorimetry was used
to determine the internal energy in a wide range of deformations. A theoretical model is proposed for estimating the change
in internal energy in deformed alloys. An investigation is made of the dependence of the interdislocation interaction parameter
on the deformation rate for different stressed state-schemes and large plastic deformations. It is shown that the relative
quantity δU/A is correlated in a wide range of deformations with the relative root-mean-square distortions of the crystal lattice of the
deformed solid solution. The mechanisms for the accumulation of energy in deformed solid solutions having a body-centered
cubic lattice are considered.
Don State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 77–83. 相似文献
22.
23.
A simple method is proposed for increasing the accuracy of computation of the eigenvalues of elliptic operators, which does not require high-order accurate schemes.Translated from Vychislitel'naya i Prikladnaya Matematika, No. 63, pp. 63–68, 1987. 相似文献
24.
I. M. Karnaukh A. S. Moskovkin G. V. Ponomarev 《Chemistry of Heterocyclic Compounds》1994,30(1):20-25
The mass spectral behavior of 1, 2-di (mesoetioporphyr inyl-1)- and 1, 2-di (mesooctaethylporphyrlnyl) ethanes and ethylenes, their Cu and Ni complexes, as well as Ni Schiff bases of 1, 2-di (mesooctaethylporphyrinyl)ethane complexes, under ionization by electron impact and bombardment by accelerated atoms, was studied. Peaks of molecular ions, for which the basic decomposition pathways were established on the basis of an analysis of the parent and daughter ions, were observed in the electron impact mass spectra of all these compounds.For Communication 29, see [1].Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 24–29, January, 1994. 相似文献
25.
V. A. Samsonov L. B. Volodarskii V. L. Korolev G. Kh. Khisamutdinov 《Chemistry of Heterocyclic Compounds》1994,30(10):1243-1249
The reaction of 4-aminobenzofurazan with aryldiazonium salts leads to the formation of 4-amino-5-aryl-azobenzofurazans and 5-amino-2-aryl-4-nitroso-2H-benzotriazoles, products of the rearrangement of the initially formed 4-amino-7-(arylazo)benzofurazans. Oxidation of the benzofurazan as well as of the triazole derivatives gives 7-aryl-1,2,3-triazol[4,5-e]benzofurazans. The chemical properties of some of the compounds obtained have been investigated.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1432–1438, October, 1994. Original article submitted July 25, 1994. 相似文献
26.
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
27.
S. V. Litvinenko V. I. Savich L. D. Bobrovnik 《Chemistry of Heterocyclic Compounds》1994,30(3):340-344
We have developed a method for synthesis of N-(3-clzloro-2-quinoxalyl)sulfonamides by reaction of 2,3-dichloroquinoxaline with substituted arylsufonamides. Based on the IR spectra, we have established that in the solid state, the synthesized compounds exist in the form of amide tautomers. Alkylation of these compounds leads to N-metliyl-N-(3-chloro-2-quinoxalyl)arylsulfonamides. We demonstrate the possibility of nucleophilic substitution of the halogen upon treatment with O- and N-nucleophiles. The use of bifunctional nucleophiles leads to condensed quinoxalines.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 3, pp. 387–392, March, 1994. 相似文献
28.
29.
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
30.
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