全文获取类型
收费全文 | 752篇 |
免费 | 0篇 |
国内免费 | 1篇 |
专业分类
化学 | 369篇 |
晶体学 | 13篇 |
力学 | 15篇 |
数学 | 94篇 |
物理学 | 262篇 |
出版年
2018年 | 9篇 |
2016年 | 10篇 |
2014年 | 9篇 |
2013年 | 29篇 |
2012年 | 11篇 |
2011年 | 11篇 |
2010年 | 15篇 |
2009年 | 20篇 |
2008年 | 16篇 |
2007年 | 17篇 |
2006年 | 30篇 |
2005年 | 10篇 |
2004年 | 13篇 |
2003年 | 23篇 |
2002年 | 15篇 |
2001年 | 12篇 |
2000年 | 17篇 |
1999年 | 11篇 |
1998年 | 15篇 |
1997年 | 11篇 |
1996年 | 13篇 |
1995年 | 9篇 |
1994年 | 12篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1989年 | 8篇 |
1988年 | 14篇 |
1987年 | 14篇 |
1986年 | 25篇 |
1985年 | 21篇 |
1984年 | 18篇 |
1983年 | 15篇 |
1981年 | 11篇 |
1980年 | 9篇 |
1979年 | 14篇 |
1978年 | 10篇 |
1977年 | 15篇 |
1976年 | 27篇 |
1975年 | 19篇 |
1974年 | 13篇 |
1973年 | 14篇 |
1972年 | 15篇 |
1971年 | 14篇 |
1970年 | 9篇 |
1969年 | 18篇 |
1968年 | 11篇 |
1967年 | 6篇 |
1966年 | 6篇 |
1962年 | 6篇 |
排序方式: 共有753条查询结果,搜索用时 15 毫秒
31.
Khankhasaeva S. Ts. Badmaeva S. V. Dashinamzhilova E. Ts. Timofeeva M. N. Burgina E. B. Budneva A. A. Paukshtis E. A. 《Kinetics and Catalysis》2004,45(5):708-713
The effect of modification on the structural, acidic, and catalytic properties of a natural layered aluminosilicate containing 90% montmorillonite was studied. With the use of low-temperature nitrogen adsorption and XRD analysis, it was found that the addition of hydroxo complexes of aluminum prevents the silicate layers of the layered aluminosilicate from closing upon heating and results both in the formation of stable micropores and in a considerable increase in the specific surface area. The acidic properties of the H, Na, and Al forms of the layered aluminosilicate were studied by IR spectroscopy of adsorbed CO molecules and by the indicator method. After modification with hydroxo complexes of aluminum, the number of Lewis acid sites and the accessibility of acidic OH groups to CO adsorption increased. The total number and strength of acid sites increased as the calcination temperature of the layered aluminosilicate was increased. A correlation between catalytic activity in the reaction of acetone dimerization and the number of acid sites in different forms of the layered aluminosilicate was obtained. 相似文献
32.
A. N. Andreyev D. D. Bogdanov V. I. Chepigin A. P. Kabachenko O. N. Malyshev Yu. Ts. Oganessian R. N. Sagajdak G. M. Ter-Akopian A. V. Yeremin F. P. Hessberger S. Hofmann V. Ninov M. Florek S. Saro M. Veselsky 《Zeitschrift für Physik A Hadrons and Nuclei》1992,344(2):225-226
The neutron-deficient isotopes257,258105 were produced in the reaction27Al+236u in 6n and 5n evaporation channels, respectively. The evaporation residues emerging from the target were separated in-flight from the projectiles and from products of different nuclear reactions by the electrostatic separator VASSILISSA [1]. The isotopes were then implanted into position-sensitive silicon detectors and identified using the --correlation method. The measured production cross-section is (5n)=(0.45±0.20)nb atE
P
=154 MeV and (6n)=(0.075±0.055) nb atE
P
=163 MeV. These cross-sections are compared with data measured for the same isotopes in the more symmetrical reaction50Ti+209Bi. 相似文献
33.
V. Angelov V. Rusanov Ts. Bonchev Th. Woike S. Haussühl 《Zeitschrift für Physik B Condensed Matter》1991,83(1):39-44
The recoilless absorption probability factor,f, and recoilless reemission,f, both measured on Na2[Fe(CN)5NO]·2 H2O single crystals using the black filter technique, were found to be different. Unexpectedly, the results found weref>f. In the calculation off, selfabsorption in the scatterer, non-ideality of the black filter and the influence of non-resonant scattering processes have all been taken into account. By varying the scattering geometry for the incoming and outgoing -beam relative to the crystallographic axes only a change in the reemitted valuesf
a, fb, fc could be detected because of the long lifetime of the excited nucleus (10–7 s) relative to the lattice vibration frequencies (1012 Hz). 相似文献
34.
Ts. E. Agadzhanyan G. L. Arutyunyan R. A. Movsesyan 《Chemistry of Heterocyclic Compounds》1998,34(8):979-982
The following heterocyclization reactions have been carried out: heterocyclization of 3,7-diacryloyl-3,7-diazabicyclo[3.3.1]nonane by benzylamine, heterocyclization of 3,7-diacryloyl-, 3,7-bis(-bromopropionyl)-, and 3,7-bis(-chloroethyl)-3,7-diazabicyclo[3.3.1]nonanes by hydrogen sulfide, and heterocyclization of 3,7-bis(bromoacetyl)- and 3,7-diacryloyl-1,3,7-triazabicyclo[3.3.1]nonanes by benzylamine and hydrogen sulfide. New compounds were obtained, based on previously unknown thiadiaza-, triaza-, and tetraazatricyclic systems.For Communication 25, see [1].A. L. Mndzhoyan Institute of Fine Organic Chemistry, National Academy of Sciences of the Republic of Armenia, Erevan 375014. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1133–1136, August, 1998. 相似文献
35.
R. Ts. Gabrielyan A. H. Toneyan O. S. Semerjyan 《Journal of Contemporary Physics (Armenian Academy of Sciences)》2007,42(2):75-81
A scheme of a three-block monolithic X-ray resonator with Si \((04\bar 4,40\bar 4)\)-configuration single crystal for NiKα2 and synchrotron radiation is proposed and realized experimentally. Specialties and advantages of the proposed scheme are given. It is shown that using asymmetric Bragg reflections makes possible to solve one of the basic problems of X-ray resonators, that of the input of radiation into the resonator and creation of the lossless cycle. The technology of fabrication of the resonator is described and the problems of raising the efficiency of its operation are considered. 相似文献
36.
M. Zh. Ovakimyan G. Ts. Gasparyan A. S. Bichakhchyan A. S. Pogosyan F. S. Kinoyan R. A. Tamazyan A. G. Aivazyan 《Russian Journal of General Chemistry》2014,84(6):1126-1129
Buta-1,3-diene-1,4-diylbis(triphenylphosphonium) iodide reacted with alkanethiols at room temperature in the presence of triethylamine to give [4-(alkylsulfanyl)buta-1,3-diene-1-yl]triphenylphosphonium iodides and triphenylphosphine in high yields. Two presumable reaction mechanisms involving ethynylvinyl intermediate (formed via the Hofmann decomposition of the starting diiodide and the initially formed 1,4-adduct with a thiol) were discussed. 相似文献
37.
T. Güzel S. P. Tretyakova T. Akyüz Yu. Ts. Oganessian . Bolcal P. Saritepe N. a
atay N. Kiratli 《Radiation measurements》1997,28(1-6):405-408
The fissionable elements content, particularly uranium, of the Blask Sea sediment samples obtained in 1978 and 1989 as surfacial sediments were determined by neutron radiography using solid state nuclear track detectors (SSNTDs). 相似文献
38.
V. Rusanov Ts. Bonctev S.K. Peneva K.H. Chakarova L.A. Spasov S.L. Petrov 《Journal of solid state chemistry》1984,51(3):336-344
Tin structures with very high values of the isomer shifts (δ = +4.3 ± 0.1 mm/sec and δ = +7 ± 0.4 mm/sec) of the Mo¨ssbauer lines, have been observed not only in thin tin films but also in bulk samples. The samples have been obtained by the reduction of SnCl2 water solutions with Mg, carried out either in the presence of ferromagnetic impurities (Fe, Co, Ni) or in an external magnetic field. The parallel X-ray studies are in accordance with the RHEED observations of thin tin films. The temperature dependence of the Mo¨ssbauer effect on samples rich inα2-Snhas been studied and microcalorimetric measurements on samples containingβ1-Snandα2-Snhave also been performed. 相似文献
39.
In the present paper the solutions of the quantum field problem for the free scalar massless field in two-dimensional space time are constructed. It is shown that the fields obtained cannot vanish at space-like infinity. The latter fact implies the existence of two conserved charge operators. The transformation properties of these solutions under the two-dimensional Lorentz group are examined. 相似文献
40.