全文获取类型
收费全文 | 181800篇 |
免费 | 2694篇 |
国内免费 | 412篇 |
专业分类
化学 | 100089篇 |
晶体学 | 2540篇 |
力学 | 6831篇 |
综合类 | 4篇 |
数学 | 19800篇 |
物理学 | 55642篇 |
出版年
2021年 | 1322篇 |
2020年 | 1646篇 |
2019年 | 1572篇 |
2018年 | 2067篇 |
2017年 | 2096篇 |
2016年 | 3484篇 |
2015年 | 2350篇 |
2014年 | 3249篇 |
2013年 | 7921篇 |
2012年 | 6336篇 |
2011年 | 7724篇 |
2010年 | 5134篇 |
2009年 | 5008篇 |
2008年 | 7430篇 |
2007年 | 7144篇 |
2006年 | 6811篇 |
2005年 | 6249篇 |
2004年 | 5486篇 |
2003年 | 4997篇 |
2002年 | 4803篇 |
2001年 | 6166篇 |
2000年 | 4537篇 |
1999年 | 3463篇 |
1998年 | 2466篇 |
1997年 | 2557篇 |
1996年 | 2538篇 |
1995年 | 2324篇 |
1994年 | 2343篇 |
1993年 | 2248篇 |
1992年 | 2641篇 |
1991年 | 2608篇 |
1990年 | 2472篇 |
1989年 | 2395篇 |
1988年 | 2378篇 |
1987年 | 2387篇 |
1986年 | 2182篇 |
1985年 | 2826篇 |
1984年 | 2809篇 |
1983年 | 2307篇 |
1982年 | 2302篇 |
1981年 | 2160篇 |
1980年 | 2139篇 |
1979年 | 2372篇 |
1978年 | 2480篇 |
1977年 | 2407篇 |
1976年 | 2289篇 |
1975年 | 2158篇 |
1974年 | 2127篇 |
1973年 | 2170篇 |
1972年 | 1368篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
S. A. Gurevich T. A. Zaraiskaya S. G. Konnikov V. M. Mikushkin S. Yu. Nikonov A. A. Sitnikova S. E. Sysoev V. V. Khorenko V. V. Shnitov Yu. S. Gordeev 《Physics of the Solid State》1997,39(10):1691-1695
The concentration and chemical state of copper in the subsurface region of Cu/SiO2 composite films obtained by simultaneous magnetron sputtering from two sources (Cu and SiO2) are determined by x-ray photoelectron spectroscopy (XPS). It is established that copper in the as-grown film is primarily in the form of unoxidized atoms dispersed in a SiO2 matrix. Annealing of the film results in practically no oxidation, but about 70% of the copper atoms condense into metallic clusters with sizes below 10 Å in the subsurface region and about 50 Å in the bulk of the film. The changes in the binding energy of core electrons, and especially in the energies of Auger electrons, are so large in this situation that photoelectron and Auger spectroscopy are efficient methods for monitoring the chemical state of this composite material. 相似文献
82.
Ya. V. Fattakhov M. F. Galyautdinov T. N. L’vova I. B. Khaibullin 《Technical Physics》1997,42(12):1457-1459
The first results regarding the formation of a two-dimensional periodic structure of local melting regions on a silicon surface
upon pulsed light irradiation are presented. The conditions are established, and the mechanism of the formation of such structures
is discussed.
Zh. Tekh. Fiz. 67, 97–99 (December 1997) 相似文献
83.
Whittum D.H. Ebihara K. Hiramatsu S. Kishiro J.-i. Monaka T. Ozaki T. Takayama K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1993,21(1):136-141
Studies of microwave amplification with an in-focused electron beam drawn from an induction injector are reported. A free-electron laser (FEL) operating at 9.4 GHz and employing ion-focusing within the interaction region has achieved power in excess of 30 MW at 9.4 GHz, with a beam energy of 0.8 MeV and current of 0.7 kA. Peak gain is 20 dB/m, with no saturation after 15 wiggler periods. Also reported are the first evolution and detuning data for an ion-channel laser/maser (ICL). Two shortcomings of the prematurely halted ICL studies are poor frequency discrimination and a large axial plasma gradient. Prospects for operation with an upgraded 1.6 MeV accelerator are discussed 相似文献
84.
85.
G. D. Krapivan N. I. Val'ter T. Ya. Kaklyugina V. G. Kul'nevich 《Chemistry of Heterocyclic Compounds》1994,30(3):289-295
Halogen in positions 3 and 5 of the furan ring in ftirfurylidenedioxanediones is readily replaced by dithiocarbonate, dithiocarbatnate, dithiophosphate, thiocyanate, and azide anions, and by thiourea, and secondary and tertiary amines. The conformation of the initial halogen derivative is retained in the substitution products.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 327–334, March, 1994. 相似文献
86.
M. A. Mikhaleva B. M. Bolotin T. A. Kizner E. S. Serebrykova 《Chemistry of Heterocyclic Compounds》1994,30(1):79-81
We have synthesized 5-alkyl(alkoxy)-2-(o-lzydroxy-p-alkoxyphenyl)pyrimidines and considered the effect of the OH group on the inesomorphism. We have found that in binuclear o-hydroxyarylpyrimidines, an ortho OH group forming an intramolecular hydrogen bond increases Tmp, inhibits the appearance of nematic properties, and promotes the appearance of a smectic A.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 30, No. 1, pp. 90–92, January, 1994. 相似文献
87.
Kh. T. Mirzaazimova S. D. Gusakova A. I. Glushenkova 《Chemistry of Natural Compounds》1994,30(5):555-558
The yields and fatty acid compositions of the free lipids and lipids weakly and strongly bound to proteins from seeds of cottonplant varieties resistant and susceptible to verticillium wilt have been determined and the changes in these indices in the seeds of the infected plants have been measured. It has been established that the seeds of healthy plants of the two varieties are similar in the qualitative compositions of the lipids and fatty acids but differ with respect the amounts of lipids in them bound with protein in different ways and with respect to the amounts of the individual fatty acids. The observed changes in the lipid and fatty-acid compositions depend on the degree of resistance of the variety to wilt. 相似文献
88.
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
89.
N. I. Khamidov B. T. Kadyrov N. T. Ul'chenko A. Sh. Isamukhamedov A. I. Glushenkova 《Chemistry of Natural Compounds》1994,30(4):430-433
The phsicochemical indices and the fatty-acid and triacylglycerol compositions of cottonseed and palm oils, of cottonseed
oil hydrogenate, and of compositions based on them have been determined with the aid of IR and UV spectroscopies, GLC analysis,
and chemical transformations. The compositions and amounts of the main classes of lipids in the initial oils and the hydrogenate
have been studied. It has been found that in the process of hydrogenation the amount of oxygenated components falls.
The work was conducted with the financial support of the Uzbek Fund for Fundamental Investigations. 相似文献
90.
N. Sh. Pal'ants R. Sh. Shakirov M. N. Sultankhodzhaev S. T. Akramova 《Chemistry of Natural Compounds》1994,29(5):662-664
The preparation and spectral properties of rhamnose orthoacetates of aconitine and imperialine are described.Tashkent Pharmaceutical Institute. Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 743–746, September–October, 1993. 相似文献