全文获取类型
收费全文 | 1067篇 |
免费 | 10篇 |
专业分类
化学 | 562篇 |
晶体学 | 11篇 |
力学 | 64篇 |
数学 | 71篇 |
物理学 | 341篇 |
无线电 | 28篇 |
出版年
2021年 | 20篇 |
2020年 | 24篇 |
2019年 | 21篇 |
2018年 | 17篇 |
2017年 | 30篇 |
2016年 | 36篇 |
2015年 | 13篇 |
2014年 | 27篇 |
2013年 | 38篇 |
2012年 | 36篇 |
2011年 | 46篇 |
2010年 | 43篇 |
2009年 | 33篇 |
2008年 | 46篇 |
2007年 | 51篇 |
2006年 | 30篇 |
2005年 | 41篇 |
2004年 | 32篇 |
2003年 | 25篇 |
2002年 | 36篇 |
2001年 | 27篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 14篇 |
1993年 | 11篇 |
1992年 | 16篇 |
1991年 | 16篇 |
1990年 | 12篇 |
1989年 | 15篇 |
1988年 | 14篇 |
1987年 | 10篇 |
1986年 | 11篇 |
1985年 | 15篇 |
1982年 | 10篇 |
1980年 | 10篇 |
1978年 | 14篇 |
1976年 | 10篇 |
1975年 | 9篇 |
1974年 | 10篇 |
1973年 | 11篇 |
1972年 | 9篇 |
1971年 | 10篇 |
1970年 | 15篇 |
1969年 | 9篇 |
1968年 | 9篇 |
1967年 | 9篇 |
排序方式: 共有1077条查询结果,搜索用时 656 毫秒
211.
Oleksii M. Antypenko Sergiy I. Kovalenko Oleksandr V. Karpenko Vladyslav O. Nikitin Lyudmyla M. Antypenko 《Helvetica chimica acta》2016,99(8):621-631
Considering the frightening high level of mortality from cancer, studies of anticancer agents are vital nowadays. The 24 thioderivatives of 2‐alkyl(aryl)‐quinazolin‐4(3H)‐thiones and 20 thioderivatives of [1,2,4]triazolo[1,5‐c]quinazoline‐2‐thiones were synthesized and evaluated for preliminary in vitro anticancer activity with subsequent in silico QSAR analysis. The substance 18 had the best results inhibiting growth of eight cancer cell lines: CCRF‐CEM of leukemia; SF‐539, SNB‐75, and U251 of CNS cancer; 786, RXF393, and UO‐31 of renal cancer; and MDA‐MB‐231/ATCC of breast cancer (?31.50 – 47.41% of cell growth) with low procancer effect. Calculated QSAR‐models for CCRF‐CEM of leukemia, T‐47D and HS 578T of breast cancer, and mean cell growth demonstrated good rate of anticancer activity prediction (r2 = 0.7 – 0.8, = 0.5 – 0.7). 相似文献
212.
A. A. Khalatov I. I. Borisov Yu. Ya. Dashevskiy A. S. Kovalenko S. V. Shevtsov 《Thermophysics and Aeromechanics》2014,20(6):713-719
Results of an experimental study of a flat plate film cooling efficiency from a single row of inclined holes embedded in a “shallow” trench are presented. It is shown the cooling efficiency of such a configuration is much greater than that of the traditional configuration of inclined round holes. This provides more uniform surface coverage by the coolant film. The flow external turbulence increases the film cooling efficiency by 5–8%, while the freestream flow acceleration reduces it by 10–15%. 相似文献
213.
K. M. Podurets D. K. Pogorelyi A. A. Kaloyan E. S. Kovalenko V. G. Kohn 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(5):845-848
The synchrotron radiation used in X-ray tomography enables us to vary the recording conditions within wide limits due to the continuous spectrum and the beam’s high brightness and collimation. The possibilities of multimode X-ray tomography at the Mediana station of the Kurchatov synchrotron radiation source, including tomography and microtomography based on white and “pink” beams, imaging with the help of a monochromatic beam, and measurements via axial and refractive phase-contrast methods, are described. The presented results of the reconstruction of different objects have been obtained under different recording conditions. 相似文献
214.
A. V. Grinyuk V. G. Burdukovskaya V. A. Zverev V. N. Kravchenko V. V. Kovalenko A. G. Luchinin A. I. Malekhanov A. T. Trofimov O. I. Trusova I. P. Smirnov A. A. Stromkov A. I. Khil’ko 《Acoustical Physics》2012,58(3):288-300
The possibilities of matching low-frequency underwater sound pulses to the parameters of an oceanic waveguide are considered. The objective is to optimize the system of few-mode tomographic observation in a shallow-water sea. Experimental data are analyzed for two methods of selecting the low-frequency fewmode pulses propagating in a shallow-water sea. The first method excites probe pulses by vertically elongated arrays, with spatial filtering after vertical or horizontal arrays receive the pulses. The second method is based on exciting broadband signals with linear frequency modulation by a single transmitter. The selection of the few-mode signal is performed by time strobing the signals at the output of the matched filter after a horizontal array receives the pulses. The distance between the sound sources and receiving systems varied from 10 to 300 km. 相似文献
215.
Maksimchuk NV Kovalenko KA Fedin VP Kholdeeva OA 《Chemical communications (Cambridge, England)》2012,48(54):6812-6814
Mesoporous metal-organic frameworks Cr- and Fe-MIL-101 are highly efficient, true heterogeneous and recyclable catalysts for solvent-free selective oxidation of cyclohexane with molecular oxygen and/or tert-butyl hydroperoxide under mild conditions. 相似文献
216.
Russian Journal of Applied Chemistry - 相似文献
217.
Nikolai B. Gorev Inna F. Kodzhespirova Yury A. Kovalenko Evgeny N. Privalov Eugenio F. Prokhorov 《Microelectronics Journal》2001,32(12):979-982
The distribution of the electric field in planar film–substrate GaAs structures under backgating is considered. It is shown that backgating can make the film exhibit a long-length region of a low-gradient electric field exceeding the threshold of N-type negative differential mobility, the magnitude of negative differential mobility in this region being high enough. At values of the film doping density and film thickness typical of GaAs transferred-electron devices, this region can be as long as several tens of micrometers. The underlying physical mechanism is discussed. 相似文献
218.
Study of the factors determining the outcome of cycloaddition of isocyanurato-substituted azides to [60]fullerene 总被引:2,自引:0,他引:2
Sinyashin O. G. Romanova I. P. Yusupova G. G. Nafikova A. A. Kovalenko V. I. Azancheev N. M. Fattakhov S. G. Reznik V. S. 《Russian Chemical Bulletin》2001,50(11):2162-2171
The final outcome of cycloaddition of isocyanuratoalkyl azides to C60 depends on the temperature, the thermal stability of azides, the substituents in the isocyanurate ring, and the number of methylene groups in the alkyl radical. The thermal transformations of the monoadducts obtained were studied. 相似文献
219.
Romanova I. P. Yusupova G. G. Fattakhov S. G. Nafikova A. A. Kovalenko V. I. Yanilkin V. V. Kataev V. E. Azancheev N. M. Reznik V. S. Sinyashin O. G. 《Russian Chemical Bulletin》2001,50(3):445-452
N-Isocyanurato-substituted aziridino[1,2][60]fullerenes were synthesized for the first time as the main products by the reaction of isocyanurato-substituted azides with C60. The thermal stability and the electrochemical behavior of the compounds synthesized were studied. 相似文献
220.
Rybachenko V. I. Schroeder G. Chotii K. Yu. Kovalenko V. V. Eitner K. 《Theoretical and Experimental Chemistry》2001,37(4):230-235
We have studied 18 reactions, including four identity reactions, involving transfer of a dimethylcarbamoyl group with N-acylpyridinium bonds to pyridine and its 4-substituted derivatives in acetonitrile solutions at 298 K. The rate constants k
ij varied within the range 0.4 to 10–6 L/mol·s; the equilibrium constants K
ij varied from 107 to 10–5. The rate and equilibrium for exchange of carbamoyl groups are described satisfactorily by the Brönsted equation. We have shown that all the reactions occur according to a forced concerted S
N2 mechanism. The structure of the transition state and its position on the reaction coordinate for identity transfer are considered using a More O'Ferrall-Jencks diagram. 相似文献