全文获取类型
收费全文 | 610篇 |
免费 | 7篇 |
国内免费 | 3篇 |
专业分类
化学 | 425篇 |
晶体学 | 8篇 |
力学 | 16篇 |
数学 | 49篇 |
物理学 | 122篇 |
出版年
2023年 | 5篇 |
2022年 | 6篇 |
2021年 | 16篇 |
2020年 | 25篇 |
2019年 | 24篇 |
2018年 | 27篇 |
2017年 | 17篇 |
2016年 | 28篇 |
2015年 | 10篇 |
2014年 | 23篇 |
2013年 | 30篇 |
2012年 | 27篇 |
2011年 | 32篇 |
2010年 | 20篇 |
2009年 | 17篇 |
2008年 | 27篇 |
2007年 | 25篇 |
2006年 | 21篇 |
2005年 | 20篇 |
2004年 | 17篇 |
2003年 | 22篇 |
2002年 | 25篇 |
2001年 | 15篇 |
2000年 | 5篇 |
1999年 | 8篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 9篇 |
1984年 | 5篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1973年 | 7篇 |
1972年 | 4篇 |
1971年 | 3篇 |
1969年 | 4篇 |
1967年 | 10篇 |
排序方式: 共有620条查询结果,搜索用时 31 毫秒
61.
M. A. Krivov E. V. Malisova M. P. Nikiforova A. N. Starikov S. S. Khludkov Yu. A. Grigor'ev O. L. Egorova V. B. Osvenskii 《Russian Physics Journal》1987,30(9):721-725
The temperature dependence of the charge carrier concentration and mobility in n-type GaAs monocrystals doped jointly by Ge and isovalent In and Sb impurities is investigated. The observable charge carrier concentration and mobility changes in the GaAs:Ge:In and GaAs:Ge:Sb are compared with the corresponding characteristics in GaAs:Ge, and the change in properties along the ingots can be explained by the Ge impurity redistribution in the gallium and arsenic sublattices in the presence of an isovalent impurity.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 3–8, September, 1987. 相似文献
62.
V. A. Bershtein L. M. Egorova P. N. Yakushev P. Pissis P. Sysel L. Brozova 《Journal of Polymer Science.Polymer Physics》2002,40(10):1056-1069
Molecular motion and thermal stability in two series of nanophase‐separated polyimide–silica (PI–SiO2) hybrid materials with chemically bound components were studied. The hybrids were synthesized from p‐aminophenyltrimethoxysilane‐terminated poly(amic acid)s as PI precursors and tetramethoxysilane as a silica precursor via a sol–gel process. The hybrids differed in their PI chemical structure and chain length (number‐average molecular weight = 5.000, 7.500, or 10.000) and in their SiO2 content, which ranged from 0 to 50 wt %. Differential scanning calorimetry, laser‐interferometric creep rate spectroscopy, and thermally stimulated depolarization current techniques were used for studying the dynamics from 100 to 650 K and from 10?3 to 10?2 Hz. Comparative thermogravimetric measurements were also carried out from 300 to 900 K. Silica nano‐ or submicrodomains that formed affected PI dynamics in two opposite directions. Because of the loosening of the molecular packing of PI chains confined to nanometer‐scale spaces between silica constraints, an enhancement of small‐scale motion, mostly at temperatures below the β‐relaxation region, occurred. However, a partial or total suppression of segmental motion could be observed above the β‐relaxation temperature, drastically so for the shortest PI chains at elevated silica contents and within or close to the glass‐transition range, because of the covalent anchoring of chain ends to silica domains. Large changes in thermal stability, including a 2.5‐fold increase in the apparent activation energy of degradation, were observed in the hybrids studied. A greater than 100 °C rise in long‐term thermal stability could be predicted for some hybrids with respect to pure PI. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1056–1069, 2002 相似文献
63.
64.
65.
A. V. Chistyakov P. A. Zharova M. A. Gubanov S. A. Nikolaev T. B. Egorova A. E. Gekhman M. V. Tsodikov 《Kinetics and Catalysis》2017,58(6):741-748
The results of a study on the activity and operational stability of an Au–Pd/MFI/Al2O3 catalyst in the reaction of ethanol conversion into a gasoline fraction of hydrocarbons are reported. In the presence of the Au–Pd/MFI/Al2O3 catalyst, ethanol was almost completely converted into an alkane–aromatic fraction of C3–C11 hydrocarbons at 300°C in an atmosphere of Ar; the yield of this fraction was as high as 90% on a feed carbon basis. It was established that, in the presence of the bimetallic Au–Pd catalyst, the yield of the target fraction increased by 10%, as compared with that on a monometallic Au-containing sample. The Au–Pd/MFI/Al2O3 catalyst exhibited much higher stability in a long-term experiment in comparison with the previously tested pilot sample of Pd–Zn/MFI/Al2O3. After a 40-h operation, the yield of the target fraction of C3+ hydrocarbons in the presence of the Au–Pd/MFI/Al2O3 catalyst decreased by 15%. The treatment of the catalyst with hydrogen led to the complete restoration of its activity. The structure of the Au–Pd active constituents was studied by transmission electron microscopy X-ray photoelectron spectroscopy. methods of the and microscopy. 相似文献
66.
Iryna V. Mineyeva 《Tetrahedron letters》2010,51(14):1836-7854
(S)-4-Methyl-3,6-dihydro-2H-pyran-2-carbaldehyde (3), the common intermediate in the syntheses of the C17-C27 subunit of laulimalide (4) and (+)-faranal (5), the trail pheromone of the pharaoh ant, Monomorium pharaonis, were obtained via transformation of methyl 3-bromomethyl-3-butenoate (1) into allylstannane 2 and subsequent allylation of (benzyloxy)acetaldehyde (6) in accordance with the Keck procedure as the key steps. 相似文献
67.
V. S. Grinev O. A. Amal’chieva A. Yu. Egorova E. V. Lyubun’ 《Russian Journal of Organic Chemistry》2010,46(9):1378-1382
Based on reactions of 5-substituted 3H-furan-2-ones or 4-oxocarboxylic acids with 1,2-binucleophiles of aromatic and aliphatic series methods were developed for
the synthesis of tricyclic structures containing a pyrrolidine fragment fused with imidazolidine or oxazolidine ring. The
pathways of the reactions are considered. It was demonstrated that the nature of the substrate did not affect the reaction
direction, but changed the scheme of the interaction. The structures of compounds obtained for the first time were proved
using IR and 1H NMR spectra. 相似文献
68.
Sharutin V. V. Sharutina O. K. Egorova I. V. Ettenko E. N. 《Russian Journal of General Chemistry》2001,71(8):1236-1237
Reactions of triphenylbismuth with sodium salts, acids, alkalies, and zinc are studied. In the first three cases Bi-O bond cleavage takes place, while zinc reduces the starting bismuth compounds to triphenylbismuth. 相似文献
69.
Yu. V. Khlebnikova L. Yu. Egorova D. P. Rodionov V. A. Kazantsev 《Technical Physics》2017,62(11):1667-1674
The structure of martensite in the In95.42Cd4.58 alloy has been studied by metallography, X-ray diffraction, dilatometry, and transmission electron microscopy. It has been shown that a massive structure built of colonies of tetragonal lamellar plates divided by a twin boundary {101}FCT is formed in the alloy under cooling below the martensite FCC → FCT transition temperature. The alloy recrystallizes after a cycle of FCT → FCC → FCT transitions with a decrease in the grain size by several times compared with the initial structure such fashion that the size of massifs and individual martensite lamella in the massif correlates with the change in the size of the alloy grain. Using thermal cycling, it has been revealed that the alloy tends to stabilize the high-temperature phase. 相似文献
70.
Chernorukov N. G. Suleimanov E. V. Egorova O. A. Kir'yanov K. V. 《Russian Journal of General Chemistry》2003,73(2):180-182
The standard enthalpies of formation of uranophosphates MI
I(PUO6)2·nH2O (MI
I = Mn, Fe, Co, Ni, Cu, Zn, Cd) are determined. The standard enthalpies of the synthesis and dehydration of these compounds are calculated and analyzed. 相似文献