全文获取类型
收费全文 | 152039篇 |
免费 | 1415篇 |
国内免费 | 413篇 |
专业分类
化学 | 83995篇 |
晶体学 | 2444篇 |
力学 | 6123篇 |
综合类 | 4篇 |
数学 | 13805篇 |
物理学 | 47496篇 |
出版年
2021年 | 1096篇 |
2020年 | 1258篇 |
2019年 | 1324篇 |
2018年 | 1688篇 |
2017年 | 1733篇 |
2016年 | 2628篇 |
2015年 | 1646篇 |
2014年 | 2443篇 |
2013年 | 6257篇 |
2012年 | 5077篇 |
2011年 | 6218篇 |
2010年 | 4301篇 |
2009年 | 4351篇 |
2008年 | 5985篇 |
2007年 | 5771篇 |
2006年 | 5652篇 |
2005年 | 5224篇 |
2004年 | 4726篇 |
2003年 | 4304篇 |
2002年 | 4196篇 |
2001年 | 5656篇 |
2000年 | 4095篇 |
1999年 | 3146篇 |
1998年 | 2149篇 |
1997年 | 2262篇 |
1996年 | 2143篇 |
1995年 | 1972篇 |
1994年 | 1975篇 |
1993年 | 1804篇 |
1992年 | 2291篇 |
1991年 | 2365篇 |
1990年 | 2189篇 |
1989年 | 2156篇 |
1988年 | 2132篇 |
1987年 | 2126篇 |
1986年 | 1949篇 |
1985年 | 2446篇 |
1984年 | 2466篇 |
1983年 | 1953篇 |
1982年 | 1960篇 |
1981年 | 1793篇 |
1980年 | 1783篇 |
1979年 | 2080篇 |
1978年 | 2147篇 |
1977年 | 2100篇 |
1976年 | 2022篇 |
1975年 | 1896篇 |
1974年 | 1881篇 |
1973年 | 1916篇 |
1972年 | 1250篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
221.
The interbranch scattering of X-rays at dislocations is studied experimentally and with the aid of numerical simulations. Narrow beam of a small divergence is used for the study which is made both in the Laue and Bragg case of diffraction. The role of interbranch scattering in the formation of defect contrast in X-ray topography is discussed. 相似文献
222.
N. B. Brandt Zh. T. Ismailov V. A. Kul'bachinskii S. A. Lapin S. M. Chudinov 《Russian Physics Journal》1989,32(11):889-898
A new method is proposed for determining the magnetic characteristics (magnitude and sign of the exchange interaction energy and the average size of clusters of magnetic ions) of dilute solid solutions of semimagnetic semiconductors at low temperatures based on oscillation measurements. The method makes it possible to find the magnetic characteristics of the indicated systems at temperatures between the point of the transition into the spin glass state and the temperature corresponding to the characteristic binding energy of magnetic atoms in clusters, for which standard methods based on the measurement of the magnetic susceptibility are not effective. The method is used to study the character of the exchange interaction in the system of solid solutions Hg1–xMnxSe as a function of their composition as well as under conditions of hydrostatic compression. To this end the oscillations of the magnetoresistance (Shubnikov-de Haas (SH) effect) in single-crystalline samples of Hg1–xMnxSe in the region of compositions 0.001 x 0.23 in magnetic fields H up to 65 kOe at temperatures T = (0.4–20) K and pressures up to 16 kbar were studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 29–39, November, 1989. 相似文献
223.
E. V. Petrova T. I. Izaak D. A. Filonenko A. P. Astashkina V. I. Otmakhov G. G. Volokitin 《Colloid Journal》2007,69(6):777-781
Peculiarities of the extraction of metal ions from aqueous solutions by fibrous polypropylene have been investigated. It has been found that metal ion adsorption proceeds owing to the existence of a gas-liquid-hydrophobic polymer boundary line. The process mechanism has been discussed. 相似文献
224.
Effect of methanol dilution on H-ZSM-5 zeolite deactivation in the process of light olefin formation
A. .A. Cichowlas P. T. Wierzchowski L. W. Zatorski 《Reaction Kinetics and Catalysis Letters》1986,32(2):341-346
Conversion of methanol in the presence of H2O, O2, H2, CO, CO2 and He was studied at 733 K on H-ZSM-5 zeolite. The effect of diluent on the selectivity to light olefins and resistance to coking of H-ZSM-5 were observed. Among the diluents studied only water exerts a promoting effect on prolonged activity of the catalyst. Some explanations of the deactivation process are given.
H2O, O2, H2, CO, CO2 He H-ZSM-5 733K. H-ZSM-5. . .相似文献
225.
Condensation of aryl- and aroylhydrazines and thiosemicarbazide with 2-diphenylphosphinoyloxybenzaldehyde results in formation of the corresponding hydrazones and thiosemicarbazone. The products give rise to conformational equilibrium between rotational and Z,E isomers, which is strongly displaced toward the E,E',Z' isomer and is determined by the nature of substituent in the hydrazine fragment. 相似文献
226.
Institute of the Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh
Soedinenii, No. 6, pp. 899–900, November–December, 1993. 相似文献
227.
Ya. S. Yakhyaev S. N. Khadzhiev T. M. Gairbekov S. E. Spiridonov 《Reaction Kinetics and Catalysis Letters》1986,30(2):263-268
The effect of hydrothermal treatment of decationized superhigh-silica zeolite on the mechanism of n-hexane conversion has been studied. It has been established that thermosteam modification sharply decreases the cracking activity and increases the selectivity to aromatization reactions. Zeolite acidity markedly decreases, but its crystal structure does not become amorphous.
-. . .相似文献
228.
When the cations bound to purple membrane are removed it turns blue, and when this blue membrane is irradiated its color changes to pink. Irradiation of pink membrane leads to the reformation of blue membrane. We have determined that the quantum efficiency for the formation of pink membrane from deionized blue membrane is 1.6 ± 0.6 ± 10 4 at 0o C, pH 5.0. We also found that the quantum efficiency for the back photoconversion, i.e. the formation of blue membrane from pink membrane, is 8.8 ± 1.6 ± 10-3 at 0o C, 55 times greater than that of the forward photoconversion reaction. The extinction coefficients of the pink membrane and blue membrane were determined to be 44 500 ± 670 cm-1 M-1 at 491 nm and 54 760 ± 830 cm-1 M -1 at 603 nm, respectively, assuming light-adapted purple membrane is 63 000 cm-1 M -1 at 568 nm. The quantum efficiency for forming pink membrane from blue membrane is much lower than that for forming the photointermediate of the blue membrane's photocycle. Their relationship is similar to that of light-adaptation and photocycle of the dark-adapted purple membrane. 相似文献
229.
230.