全文获取类型
收费全文 | 397611篇 |
免费 | 3725篇 |
国内免费 | 962篇 |
专业分类
化学 | 210052篇 |
晶体学 | 5769篇 |
力学 | 18400篇 |
综合类 | 15篇 |
数学 | 45609篇 |
物理学 | 122453篇 |
出版年
2019年 | 3244篇 |
2018年 | 5051篇 |
2017年 | 5135篇 |
2016年 | 6848篇 |
2015年 | 4149篇 |
2014年 | 6409篇 |
2013年 | 16185篇 |
2012年 | 12673篇 |
2011年 | 15231篇 |
2010年 | 10719篇 |
2009年 | 10570篇 |
2008年 | 13850篇 |
2007年 | 14073篇 |
2006年 | 13203篇 |
2005年 | 14337篇 |
2004年 | 13136篇 |
2003年 | 11014篇 |
2002年 | 9746篇 |
2001年 | 10628篇 |
2000年 | 8262篇 |
1999年 | 6400篇 |
1998年 | 5585篇 |
1997年 | 5536篇 |
1996年 | 5158篇 |
1995年 | 4799篇 |
1994年 | 4929篇 |
1993年 | 4524篇 |
1992年 | 5204篇 |
1991年 | 5285篇 |
1990年 | 5063篇 |
1989年 | 4958篇 |
1988年 | 4984篇 |
1987年 | 4816篇 |
1986年 | 4578篇 |
1985年 | 6036篇 |
1984年 | 6393篇 |
1983年 | 5335篇 |
1982年 | 5634篇 |
1981年 | 5466篇 |
1980年 | 5380篇 |
1979年 | 5459篇 |
1978年 | 5888篇 |
1977年 | 5708篇 |
1976年 | 5806篇 |
1975年 | 5419篇 |
1974年 | 5520篇 |
1973年 | 5644篇 |
1972年 | 3927篇 |
1971年 | 3371篇 |
1970年 | 3068篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
981.
V. M. Lembrikov V. V. Volkova G. P. Zhavoronkova L. V. Konyakhina 《Russian Journal of Applied Chemistry》2006,79(2):196-200
Data on the equilibrium distribution of phosphoric acid among the aqueous and organic phases in extraction of phosphoric acid with tri-n-butyl phosphate are presented for the system constituted by phosphoric acid produced from the Khibiny concentrate and by the extracting agent from the industrial system for purification of extraction phosphoric acid at 25–50°C. 相似文献
982.
P. K. Sazonov G. A. Artamkina I. P. Beletskaya 《Russian Journal of Organic Chemistry》2006,42(3):438-447
The nucleophilic aromatic and vinyl substitution using diaza-18-crown-6 as nucleophile afforded a number of its N,N’-diaryl-[aryl = 2,4-(NO2)2C6H3, 4-C5F4N, 4-CF3C6F4] and N,N’-dialkenyl-substituted derivatives [alkenyl = PhC(O)CH=CH, MeOCOCH=CH, (EtO2C)2C=C(Ph), etc.]. Arylation of diaza-18-crown-6 with nonactivated aryl bromides, such as 4-Me2NC6H4Br, 4-MeOC6H4Br, C6H5Br, and 4-CF3C6H4Br, was effected under catalysis by palladium complexes. N,N’-Diaryldiaza-18-crowns-6 having electron-acceptor substituents in the aromatic rings turned out to be incapable of forming complexes with metal cations, while their analogs containing electron-donor para-methoxy and para-dimethylamino groups gave complexes with barium perchlorate. 相似文献
983.
Within the framework of fractal analysis and percolation theory, an alternative model of reinforcement of filled polymers
is offered. Practically, this model can be used only to describe the reinforcement of nanocomposites, because, according to
the treatment considered, a pronounced reinforcement can be reached only at ratios of filler particle diameter to the statistical
segment length of about 10 and less. A theoretical calculation showed a good qualitative and quantitative agreement with experiments.
The type of reinforcement mechanism of composites is determined by the type of the space (fractal or Euclidean) in which the
structure of the polymeric matrix is formed.
__________
Translated from Mekhanika Kompozitnykh Materialov, Vol. 42, No. 6, pp. 797–802, November–Decem ber, 2006. 相似文献
984.
B. D. Kabulov K. A. Akhundzhanov F. U. Yunusov O. A. Shpigun S. S. Negmatov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(3):354-356
The hydrolytic polycondensation of tetraethoxysilane in the presence of various polymers (polyacrylonitrile, polycaproamide, and chitosan) as templates was performed with the use of the sol-gel technology to obtain nanohybrid composite polymer-silica sorbents-nanofractals. 相似文献
985.
986.
E. Baggio Saitovitch F. J. Litterst I. Souza Azevedo R. B. Scorzelli 《Hyperfine Interactions》1989,50(1-4):529-535
The Mössbauer spectra of YBa2(Cu1?x Fe x )3O7 at room temperature show several doublets attributed to Fe in Cu(1) sites with different oxygen configurations. Here we present a systematic study performed at 4.2 K forx=0.005, 0.01, 0.03, 0.05, 0.10, 0.15. To obtain information about the magnetic ordered state two samples, withx=0.005 andx=0.15, have been studied at 4.2 K underB ext=5 T. The Mössbauer spectra indicate that the iron moments are polarized forx=0.005, while in the ordered state (x=0.15) they have an antiferromagnetic or spin-glass-like arrangement with high anisotropy. 相似文献
987.
V. G. Baklykov V. N. Charushin O. N. Chupakhin V. N. Drozd 《Chemistry of Heterocyclic Compounds》1987,23(4):465-469
Thiobenzhydrazides undergo cyclization with N-alkyl-quinoxalinium salts to give 5-alkyl-substituted 1,4,4a,5,10,10a-hexahydro-1,3,4-thiadiazino[5,6-b]quinoxalines, which undergo isomerization to 10-alkyl-substituted thiadiazinoquinoxalines when they are heated in ethanol or in the presence of acids.See [1] for Communication 20.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 557–561, April, 1987. 相似文献
988.
989.
990.
In recent years there has emerged significant interest in low pressure radio frequency (rf) glow discharges which are used widely particulary in IC fabrication. Various parameters of the rf glow discharge have been found to be useful for its electrical characterization; however, there is no uniformity and agreement. Extensive experimental investigations on various discharge systems have shown, that the self-bias on the rf driven electrode, the complex conductivity and the breakdown characteristic are preferable parameters of rf discharges. Advantageously the self-bias and the complex conductivity should be presented in dependence on the pressure and the applied rf voltage. The discharge current cannot be measured quite accurately due to currents via leaky capacitors and the deviations from a sinusoidal form of the current due to nonlinearities. 相似文献