全文获取类型
收费全文 | 606篇 |
免费 | 2篇 |
国内免费 | 3篇 |
专业分类
化学 | 273篇 |
晶体学 | 14篇 |
力学 | 30篇 |
数学 | 37篇 |
物理学 | 257篇 |
出版年
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 8篇 |
2019年 | 20篇 |
2018年 | 15篇 |
2017年 | 23篇 |
2016年 | 19篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 22篇 |
2012年 | 17篇 |
2011年 | 36篇 |
2010年 | 22篇 |
2009年 | 22篇 |
2008年 | 28篇 |
2007年 | 24篇 |
2006年 | 15篇 |
2005年 | 5篇 |
2004年 | 13篇 |
2003年 | 14篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 12篇 |
1999年 | 12篇 |
1998年 | 12篇 |
1997年 | 9篇 |
1996年 | 7篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1989年 | 8篇 |
1988年 | 6篇 |
1987年 | 12篇 |
1986年 | 5篇 |
1984年 | 9篇 |
1983年 | 10篇 |
1982年 | 10篇 |
1981年 | 10篇 |
1980年 | 4篇 |
1979年 | 7篇 |
1978年 | 7篇 |
1977年 | 10篇 |
1976年 | 6篇 |
1975年 | 7篇 |
1974年 | 4篇 |
1973年 | 7篇 |
1972年 | 7篇 |
1971年 | 4篇 |
1970年 | 9篇 |
1966年 | 4篇 |
1965年 | 8篇 |
排序方式: 共有611条查询结果,搜索用时 46 毫秒
11.
The kinetics of formation and cleavage of hydrogen bonds in complexes of carboxylic acids with proton acceptors have been studied by PMR spectroscopy over the range –100 to 150°C. The activation parameters of the processes have been measured.
1H –100° ÷–155°C . .相似文献
12.
A. S. Golubev N. D. Chkanikov M. Yu. Antipin Yu. T. Struchkov A. F. Kolomiets A. V. Fokin 《Russian Chemical Bulletin》1992,41(8):1425-1429
Condensation of methyl trifluoropyruvate with 2-(3,4-dimethoxyphenyl)ethylamine, tryptamine, and (D, L)-tryptophan yielded 1-methoxycarbonyl-1-trifluoromethyl-6,7-dimethoxy-1,2,3,4-tetrahydroisoquinoline, 1-methoxycarbonyl-1-trifluoromethyl-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole, and Z-1-methoxycarbonyl-1-trifluoromethyl-3-carboxy-1,2,3,4-tetrahydro-9H-pyrido[3,4-b]indole, respectively. The Z configuration of the latter was determined by x-ray structural analysis.A. N. Nesmayanov Institute of Organoelemental Compounds, Russian Academy of Sciences, 117813 Moscow, Russia. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1831–1836, August, 1992. 相似文献
13.
M. Yu. Zaremski E. G. Drozdova E. S. Garina M. B. Lachinov V. B. Golubev 《Polymer Science Series B》2006,48(5):290-294
The main kinetic and thermodynamic parameters of the pseudoliving radical polymerization of styrene mediated by 4-linoleamido-2,2,6,6-tetramethyl-1-piperidinyloxy have been studied. It has been shown that the introduction of the said substituent into nitroxide leads to a marked reduction in the rate constant of reinitiation that is compensated for by the simultaneous reduction in the rate constant of reversible termination. As a result, the rate of pseudoliving polymerization, the rate of molecular mass growth, and the polydispersity of the polymer appear to be practically the same for processes mediated by both unsubstituted and substituted nitroxides. 相似文献
14.
V. O. Kudyshkin S. Sh. Rashidova A. V. Surdina M. Yu. Zaremski V. B. Golubev 《Polymer Science Series B》2007,49(11-12):297-300
The polymerization of N-vinylpyrrolidone has been studied in the presence of the stable radical 2,2,6,6-tetramethyl-1-piperidinyloxy. It has been shown that at 120°C the polymerization proceeds via the irreversible inhibition mechanism, while, at 60°C, secondary inhibition occurs in the system during the postinduction period. This effect may be used for regulation of the molecular-mass characteristics of polymers. 相似文献
15.
Doklady Mathematics - The problem of controlling oscillations near the equilibrium position of a scleronomic mechanical system with several degrees of freedom is solved. One degree of freedom is... 相似文献
16.
S. F. Bureiko N. S. Golubev G. S. Denisov I. Ya. Lange 《Reaction Kinetics and Catalysis Letters》1977,7(2):139-144
The kinetic isotope effect in proton exchange between methanol and water in CCl4 solution was studied by1H and2H NMR and kinetic IR spectroscopy. The exchange rate increases in the series CD3OH+H2O3OD+H2O3OD+D2O. It has been concluded that the limiting step of the reaction involves the formation of an H-bonded cyclic intermediate.
1H 2H - CCl4. , CD3OH+H2O相似文献3OD+H2O 3OD+D2O. , - -.
17.
18.
The behavior of some 3-nitrovinyl indoles in their reactions with nitrogen-containing nucleophilic reagents is examined. It is shown that hydroxylamine, phenylhydrazine, hydrazine, and semicarbazide react with 3--nitrovinyl indole to give the corresponding oxime, phenylhydrazone, azine, and semicarbazone of indole-3-aldehyde, possibly by decomposition of intermediates formed by the addition of the nucleophilic reagents to the nitrovinyl indole. 3--Nitropropenyl indole and N-methyl-3--nitrovinyl indole react similarly. Only the addition products of phenylhydrazine with N-acetyl-3-nitrovinyl indole and N-acetyl-3--nitropropenyl indole are stable. The reaction conditions and constants of the compounds prepared are given, and explanations are offered for the results obtained.For part XXXV, see [14]. 相似文献
19.
Osipov SN Golubev AS Sewald N Michel T Kolomiets AF Fokin AV Burger K 《The Journal of organic chemistry》1996,61(21):7521-7528
A new method for the preparation of alpha-chlorodifluoromethyl-, alpha-bromodifluoromethyl-, and alpha-difluoromethyl-substituted alpha-hydroxy and alpha-amino acid esters 11, 19-21 is described. The key step of the synthesis is the regioselective alkylation of ketones 5, 7-9 and imines 16-18 with C-nucleophiles. The ketones 7-9 are readily available from 3,3,3-trifluorolactate 1 by a five-step procedure. Subsequent removal of the protecting groups from 19-21 provides the corresponding free amino acids 25, 26, 28. 相似文献
20.
M. I. Krivopustov J. Adam V. Bradnova R. Brandt V. S. Butsev P. I. Golubev V. G. Kalinnikov J. Karachuk B. A. Kulakov E.-J. Langrock G. Modolo M. Ochs R. Odoj A. N. Premyshev V. S. Pronskich Th. Schmidt V. I. Stegailov J. S. Wan V. M. Zupko-Sitnikov 《Journal of Radioanalytical and Nuclear Chemistry》1997,222(1-2):267-270
First experiments on the transmutation of long-lived129I and237Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:129I(n,)130I and237Np(n,)238Np. The isotopes130I (T
1/2-12.36 h) and238Np (T
1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (129I(n,))=(10±2)b and (237Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna. 相似文献