全文获取类型
收费全文 | 488篇 |
免费 | 10篇 |
国内免费 | 5篇 |
专业分类
化学 | 316篇 |
晶体学 | 2篇 |
力学 | 13篇 |
数学 | 60篇 |
物理学 | 112篇 |
出版年
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 5篇 |
2017年 | 3篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 13篇 |
2013年 | 12篇 |
2012年 | 24篇 |
2011年 | 25篇 |
2010年 | 11篇 |
2009年 | 10篇 |
2008年 | 21篇 |
2007年 | 18篇 |
2006年 | 24篇 |
2005年 | 29篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 22篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 18篇 |
1998年 | 11篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 3篇 |
1994年 | 3篇 |
1993年 | 9篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 9篇 |
1989年 | 5篇 |
1988年 | 8篇 |
1986年 | 11篇 |
1985年 | 6篇 |
1984年 | 8篇 |
1983年 | 5篇 |
1982年 | 8篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 5篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1973年 | 4篇 |
1971年 | 4篇 |
1969年 | 2篇 |
1968年 | 3篇 |
排序方式: 共有503条查询结果,搜索用时 0 毫秒
101.
102.
Gerard de Leeuw John S. Field Raymond J. Haines Beth McCulloch Elsie Meintjies Christiaan Monberg Gillian M. Olivier Praveen Ramdial Clifford N. Sampson Beate Sigwarth Nick D. Steen Kandasamy G. Moodley 《Journal of organometallic chemistry》1984,275(1):99-111
Reaction of [Fe2(CO)9] with a half molar amount of R2PYPR2 (Y = CH2, R = Ph, Me, OMe or OPri; Y = N(Et), R = OPh, OMe or OCH2; Y = N(Me), R = OPri or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe2(μ-CO)(CO)6{μ-R2PYPR2}]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe2(μ-CO)(C))4{μ-R2PYPR2}2] but under thermal conditions in the formation of the mononuclear species [Fe(CO)3{R2PYPR2}]. Reaction of [Ru3(CO)12] with an equimolar amount of (RO)2PN(R′)P(OR)2 (R′ = Me, R = Pri or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru3(CO)10{μ-(RO)2PN(OR)2}] which reacts further with excess (RO)2PN(R′)P(OR)2 on irradiation with ultraviolet light to afford the dinuclear compound [Ru2(μ-CO)(CO4{μ-(RO)2PN(R′)P(OR)2}2]. The molecular structure of [Ru2(μ-CO)(CO)4{μ-(MeO)2PN(Et)P(OMe)2}2], which has been determined by X-ray crystallography, is described. 相似文献
103.
Ultrafine amorphous alloy particles of (Fe1-x Cox)60B40 with x=0.1, 0.3, 0.5, 0.7, and 0.9 have been prepared by reduction of the metal ions using KBH4 in aqueous solution. electron microscopy shows that the particle size is of the order of 20 nm. Mössbauer spectroscopy has been used to elucidate the magnetic properties of the particles. 相似文献
104.
105.
Samples of two types of natural basalt were equilibrated over a range of oxygen pressures at four different temperatures, and then quenched to room temperature. Except at the lowest temperature, where magnetic crystals formed under the most oxidizing conditions, totally amorphous samples were obtained. The Mössbauer spectra of 45 samples of the quenched basaltic melts were measured at room temperature. The relationship obtained between the oxidation state and oxygen fugacity differs to some extent from those relations previously described in the literature, in not yielding a linear relationship between log(farric/ferrous) and log(fo2). This might indicate a more involved redox process than that described by a simple reaction between oxides and/or the influence of the cation composition in the process of glass formation. An investigation was made of the kinetics of the redox process. For the experimental setup used, redox equilibrium would be reached within three hours. Finally, three naturally quenched basalt glasses were analyzed for comparison; two showed lower oxidation states than previously found in Icelandic rocks. 相似文献
106.
Samples of human faeces from patients suffering from intestinal bleeding have been studied by use of Mössbauer spectroscopy. It is shown that it is possible to follow the degradation of blood in the digestive tract. 相似文献
107.
Morten B. Madsen Steen Mørup Christian J. W. Koch Gertrud Lindemann 《Hyperfine Interactions》1986,29(1-4):1431-1434
The nature of the iron-containing phase in the dental enamel of sump beaver incisors has been studied by use of Mössbauer spectroscopy. All iron atoms are found to be trivalent and to be present in particles exhibiting superparamagnetic relaxation. The iron-containing phase has Mössbauer parameters similar to those of ferritin. 相似文献
108.
109.
The feasibility of using the affinity CE methodologies pre-equilibrium CZE and CE frontal analysis was tested on interaction systems exhibiting rapid on-and-off kinetics. Experimentally, the methodologies differ only with respect to the volume of sample introduced into the capillary. Pre-equilibrium CZE has been considered amendable to interactions with slow on-and-off kinetics only; however, it has recently been applied in studies of interactions with fast on-and-off kinetics. The effect of varying the sample volume introduced hydrodynamically into the capillary on the apparent degree of complexation was studied. For two different binding systems, the fraction of free analyte was found to be overestimated using pre-equilibrium CZE as compared to volumes providing plateau peak conditions as used with frontal analysis. Results indicate that frontal analysis conditions lead to more robust binding assays and thus more reliable data. The validity of data obtained by pre-equilibrium CZE may be low, thus the use of an experimental setup providing plateau peaks is highly recommended. It is suggested that the effect of altering the sample volume on the degree of binding should be investigated as part of method development and validation. 相似文献
110.
Selenomethionine (SeMet) was oxidized by heating an acidic solution with hydrogen peroxide. Samples were taken before and during the oxidation process. The oxidation products were separated by cation exchange chromatography followed by ICP-MS detection to identify the selenium containing compounds as well as electrospray ionization MS detection to determine the masses of the degradation products. Furthermore, the samples were analyzed by 77Se-NMR. The first appearing degradation product was selenomethionine selenoxide, which was converted via the deaminated selenoxide to methane seleninic acid and selenite. 相似文献