全文获取类型
收费全文 | 296篇 |
免费 | 5篇 |
国内免费 | 1篇 |
专业分类
化学 | 148篇 |
力学 | 29篇 |
数学 | 35篇 |
物理学 | 90篇 |
出版年
2022年 | 5篇 |
2019年 | 4篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 7篇 |
2015年 | 3篇 |
2014年 | 13篇 |
2013年 | 7篇 |
2012年 | 9篇 |
2011年 | 19篇 |
2010年 | 11篇 |
2009年 | 5篇 |
2008年 | 12篇 |
2007年 | 6篇 |
2006年 | 7篇 |
2005年 | 8篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 4篇 |
2000年 | 7篇 |
1999年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 4篇 |
1994年 | 3篇 |
1993年 | 4篇 |
1991年 | 2篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 5篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 7篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 11篇 |
1974年 | 4篇 |
1973年 | 8篇 |
1972年 | 4篇 |
1971年 | 6篇 |
1970年 | 5篇 |
1969年 | 4篇 |
1966年 | 2篇 |
排序方式: 共有302条查询结果,搜索用时 15 毫秒
1.
S. A. Klimin M. N. Popova E. P. Chukalina B. Z. Malkin A. R. Zakirov E. Antic-Fidancev Ph. Goldner P. Aschehoug G. Dhalenne 《Physics of the Solid State》2005,47(8):1425-1430
The absorption spectra of Yb2Ti2O7 single crystals and the luminescence and luminescence excitation spectra of Y2Ti2O7: Yb (1%) polycrystals were studied in the temperature range 4.2–300 K. The spectra were analyzed in terms of the crystal-field
theory and the exchange-charge model. Based on the set of crystal-field parameters found for Yb2Ti2O7, analogous sets of parameters were determined for other rare-earth titanates and proved to be in reasonable agreement with
all available experimental data.
__________
Translated from Fizika Tverdogo Tela, Vol. 47, No. 8, 2005, pp. 1376–1380.
Original Russian Text Copyright ? 2005 by Klimin, Popova, Chukalina, Malkin, Zakirov, Antic-Fidancev, Goldner, Aschehoug,
Dhalenne. 相似文献
2.
E. D. Skakovskii S. V. Rykov L. Yu. Tychinskaya Ya. N. Malkin 《Russian Chemical Bulletin》1987,36(8):1753-1755
Conclusions Negative polarization of the protons of aniline and other compounds is observed upon the photoexcitation of aniline solutions. This effect is a consequence of optical nuclear polarization in short-lived donor-acceptor complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1890–1892, August, 1987. 相似文献
3.
Light-dependent oxygen uptake was observed and studied in thylakoids from early greening barley in comparison to oxygen uptake in chlorophyll solutions and in thylakoids from fully green leaves. Substantial oxygen uptake was observed in chlorophyll solutions supplemented with tryptophan, histidine, ascorbic acid or linoleic acid. This uptake was diminished by adding azide, beta-carotene and alpha-tocopherol, which are specific singlet-oxygen quenchers. Illuminated thylakoids from greening barley also exhibited marked oxygen uptake that, likewise, was strongly quenched by azide. In comparison, azide was found not to affect oxygen uptake that is associated with the methyl viologen-catalyzed Mehler reaction. It is reasoned that in the first two cases the oxygen uptake arises from chlorophyll-photosensitized activation of oxygen to the singlet state and its consumption by exogenous or endogenous substrates. In greening, we propose that disorganized chlorophyll photo-sensitizes the oxygen uptake. 相似文献
4.
5.
6.
Conclusions The photodissociation quantum yields were determined for a series of phenols in nonpolar media and the increase in quantum yield with increasing excitation energy was shown to be a function of competition of internal intercombinational conversion process.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 438–441, February, 1987. 相似文献
7.
Knaggs S Malkin H Osborn HM Williams NA Yaqoob P 《Organic & biomolecular chemistry》2005,3(21):4002-4010
Two novel tyrosinase mediated drug delivery pathways have been investigated for the selective delivery of cytotoxic units to melanocytes from urea and thiourea prodrugs. The synthesis of these prodrugs is reported, as well as oximetry data that illustrate that the targets are substrates for tyrosinase. The stability of each of the prodrugs in (i) phosphate buffer and (ii) bovine serum is discussed, and the urea prodrugs are identified as lead candidates for further studies. Finally, HPLC studies and preliminary cytotoxicity studies in a melanotic and an amelanotic cell line, that illustrate the feasibility of the approach, are presented. 相似文献
8.
Unraveling σ and π Effects on Magnetic Anisotropy in cis‐NiA4B2 Complexes: Magnetization,HF‐HFEPR Studies,First‐Principles Calculations,and Orbital Modeling
下载免费PDF全文
Dr. Gaëlle Charron Dr. Elena Malkin Dr. Guillaume Rogez Dr. Luke J. Batchelor Dr. Sandra Mazerat Dr. Régis Guillot Dr. Nathalie Guihéry Dr. Anne‐Laure Barra Dr. Talal Mallah Dr. Hélène Bolvin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(47):16850-16862
By using complementary experimental techniques and first‐principles theoretical calculations, magnetic anisotropy in a series of five hexacoordinated nickel(II) complexes possessing a symmetry close to C2v, has been investigated. Four complexes have the general formula [Ni(bpy)X2]n+ (bpy=2,2′‐bipyridine; X2=bpy ( 1 ), (NCS?)2 ( 2 ), C2O42? ( 3 ), NO3? ( 4 )). In the fifth complex, [Ni(HIM2‐py)2(NO3)]+ ( 5 ; HIM2‐py=2‐(2‐pyridyl)‐4,4,5,5‐tetramethyl‐4,5‐dihydro‐1H‐imidazolyl‐1‐hydroxy), which was reported previously, the two bpy bidentate ligands were replaced by HIM2‐py. Analysis of the high‐field, high‐frequency electronic paramagnetic resonance (HF‐HFEPR) spectra and magnetization data leads to the determination of the spin Hamiltonian parameters. The D parameter, corresponding to the axial magnetic anisotropy, was negative (Ising type) for the five compounds and ranged from ?1 to ?10 cm?1. First‐principles SO‐CASPT2 calculations have been performed to estimate these parameters and rationalize the experimental values. From calculations, the easy axis of magnetization is in two different directions for complexes 2 and 3 , on one hand, and 4 and 5 , on the other hand. A new method is proposed to calculate the g tensor for systems with S=1. The spin Hamiltonian parameters (D (axial), E (rhombic), and gi) are rationalized in terms of ordering of the 3 d orbitals. According to this orbital model, it can be shown that 1) the large magnetic anisotropy of 4 and 5 arises from splitting of the eg‐like orbitals and is due to the difference in the σ‐donor strength of NO3? and bpy or HIM2‐py, whereas the difference in anisotropy between the two compounds is due to splitting of the t2g‐like orbitals; and 2) the anisotropy of complexes 1 – 3 arises from the small splitting of the t2g‐like orbitals. The direction of the anisotropy axis can be rationalized by the proposed orbital model. 相似文献
9.
Optics and Spectroscopy - Heterogeneity of aqueous solutions of polythymidylic acid (poly-T) at room temperature is established by luminescence and absorption spectroscopy. It is found that there... 相似文献
10.
Unusual rheological effects have been revealed during the deformation of polyacrylonitrile (PAN) solutions in DMSO. The effects are observed during the study of rheological properties in a wide range of PAN concentrations and are explained by the structuring occurring at low polymer concentrations. At concentrations of at most 0.1%, the solutions exhibit the behavior of soft gels, which are characterized by yield stresses and frequency-independent storage moduli. As concentration is increased, both effects gradually vanish and the solutions are almost transformed into Newtonian liquids. The results have been explained by the formation of a supramolecular spatial structure at low polymer concentrations. As concentration is increased, the role of structuring is suppressed by the formation of a network of intermacromolecular entanglements. The ability of dilute PAN solutions to exist in two states, i.e., with destroyed structuring and in the form of a physical polymer gel, leads to stress self-oscillations and thixotropic effects. The addition of a precipitant (water) to the PAN-DMSO solutions leads to the formation of a gel throughout the concentration range. 相似文献