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121.
The magnetic behavior of the ternary borides RE2RuB6 and RE2OsB6 (RE = Y, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) was studied in the temperature range 1.5 K < T < 1100 K. All compounds crystallize with the Y2ReB6-type structure and are characterized by direct RE-RE contacts and the formation of planar infinite two-dimensional rigid boron nets. The magnetic properties reveal a typical Van Vleck paramagnetism of free RE3+-ions at temperatures higher than 200 K with ferromagnetic interaction in the low-temperature range T < 55 K. The ferromagnetic ordering temperatures vary with the De Gennes factor. There is no indication for a magnetic contribution from the Ru(Os)-sublattice. Above 1.8 K none of the samples were found to be superconducting. 相似文献
122.
Dr. Peter Rogl Subhash K. Naik Erwin Rudy 《Monatshefte für Chemie / Chemical Monthly》1977,108(6):1325-1337
The system TiC–HfC–MoC was investigated by means of melting point, differentiothermoanalytical, X-ray diffraction and metallographic techniques on hotpressed as well as melted alloy specimens. A constitutional diagram from 1500°C through the melting range was established.Investigation of the (Hf, Mo)C system (isopleth: HfC0.98–MoC1.0) showed a small miscibility gap within the cubic monocarbide solution () [Tc=1630°C, (HfC)0.45(MoC)0.55]. The miscibility gap interacts with the solvus curve with a monotectoid-like decomposition reaction at 1575°C, (HfC)0.35(MoC)0.65.At temperatures below 1630°C, phase equilibria within TiC–HfC–MoC are characterized by a large miscibility gap connecting the TiC–HfC and HfC–MoC boundary systems. Additions of MoC to TiC–HfC alloys decrease the critical temperature (1780°C); additions of TiC to HfC–MoC alloys raise the critical temperature (1630°C). No maximum type ternary critical point or saddle point was found to occur.Isothermal sections were prepared at 1500°C and 1650°C. At temperatures above 1960°C (-MoC+C-MoC) a complete solid solution (-B 1) is formed within TiC–HfC–MoC. The melting behaviour (liquidus projection of TiC–HfC–MoC) shows flat melting temperatures in the MoC corner but extremely heterogeneous melting near the TiC–HfC boundary.Isothermal sections have been calculated assuming regular solutions.With 5 Figures 相似文献
123.
Peter Rogl 《Monatshefte für Chemie / Chemical Monthly》1979,110(1):235-243
New ternary metal borides with compositionR. E. T
4B4 (R. E.=rare earth metal,T=transition metal) have been synthesized within the systems [La,Ce,Pr,Nd,Sm]–Os–B and [Y, La, Ce, Pr, Nd, Sm, Gd, Tb]–Ir–B. All compounds were found to be crystallizing with NdCo4B4-type structure. Magnetic measurements (80–300 K,Curie-Weiss behaviour,
p
~ 16K and µeff=9.94µB for TbIr4B4) indicate Y andR. E. elements (except Ce) to be trivalent in these compounds. The crystal chemistry of the isotypic series [Y,R. E.] [Os,Ir]4B4 is discussed.
Ternäre Metallboride. [La,Ce,Pr,Nd,Sm] Os4B4 und [Y,La,Ce,Pr,Nd,Sm,Gd,Tb] Ir4B4 mit NdCo4B4-Struktur
Zusammenfassung Es wurden neue Metallboride der ZusammensetzungR. E. T 4B4 (R. E.=Seltenerdmetall,T=Übergangsmetall) innerhalb der Systeme [La,Ce, Pr,Nd,Sm]–Os–B und [Y,La,Ce,Pr,Nd,Sm,Gd,Tb]–Ir–B hergestellt. Alle Verbindungen kristallisieren entsprechend dem NdCo4B4-Typ. Magnetische Messungen (80–300K,Curie-Weiss-Verhalten, p ~ 16K und µeff=9.94µB für TbIr4B4) zeigen an daß Y und dieR. E.-Elemente (ausgenommen Ce) in diesen Verbindungen trivalent sind. Die Kristallchemie der isotypen [Y,R. E.][Os,Ir]4B4-Verbindungen wird diskutiert.相似文献
124.
Jrg Wehner Gerda Horneck 《Journal of photochemistry and photobiology. B, Biology》1995,30(2-3):171-177
The mutational spectra at the lacZ gene, induced either by vacuum UV at 160 nm or UVC at 254 nm in vacuum-dried preparations of Escherichia coli plasmid pUC19 DNA, have been characterized from 72 E. coli-propagated mutants by DNA sequencing. In plasmids irradiated in vacuum, vacuum UV is five times more mutagenic than UVC. In the UV-induced mutants, base substitutions largely predominate, with GC → AT (G, guanine; C, cytosine; A, adenine; T, thymine) transitions being the most abundant type of base change for vacuum UV (61%) and UVC (47%). Most of the GC → AT transitions appear to occur at dipyrimidine sites, which are located at the non-transcribed DNA strand. Some, but not all, hot spots for GC → AT transitions are identical for vacuum UV and UVC. Frameshifts, resulting from a loss of the thymine residue, are specific for UVC (22%), and were not detected after treatent with vacuum UV. They occur predominantly at thymine runs of the transcribed DNA strand. Only a few deletions were detected following irradiation with vacuum UV (7.5%) and UVC (2%); however, their frequency is not enhanced compared with the spontaneous mutation spectrum. The data confirm the important role of base substitution mutations in UV-induced mutagenesis, which is not only valid for the UVC range, but extends towards the vacuum UV range. 相似文献
125.
A. GrytsivD. Kaczorowski A. Leithe-JasperV.H. Tran A. PikulP. Rogl M. PotelH. Noël M. BohnT. Velikanova 《Journal of solid state chemistry》2002,163(1):178-185
Phase equilibria in the silicon-rich part of the system Si-Yb (>60 at.% Si) have been established from DTA, LOM, EMPA, and X-ray diffraction experiments on arc-melted and annealed bulk alloys as well as on single crystals grown from pure gallium or indium metal used as a flux solvent. Phase relations are characterized by the existence of a defect disilicide showing polymorphism. Yb3Si5, the low-temperature modification with Th3Pd5 type, is a line compound at 62.5 at.% Si, stable below 947±7°C. Above this temperature Yb3Si5 transforms into the YbSi2−x (defect AlB2-derivative type) corresponding to a peritectoid equilibrium at 947±7°C: YbSi2−x+YbSi⇔Yb3Si5. YbSi2−x exhibits a small homogeneity region from ∼62.5 at.% to ∼63.5 at.% Si and melts incongruently at 1408±9°C at ∼63 at.% Si. On cooling it decomposes according to a eutectoid reaction at 763±7°C: YbSi2−x⇔Yb3Si5+(Si). The silicon-rich part of the diagram is characterized by a eutectic equilibrium at 1135+7°C and ∼81 at.% Si: L⇔YbSi2−x+(Si). From magnetic susceptibility and electrical resistivity measurements, performed on single-crystalline specimens, Yb3Si5 was found to be an intermediate valent system. 相似文献
126.
O. M. Trokhimenko V. V. Anan’eva V. N. Zaitsev V. I. Gerda A. A. Golub 《Russian Journal of Applied Chemistry》2008,81(3):403-406
Effect of a number of factors (time of contact and mass ratio of phases, acidity and temperature of the medium, concentrations of macrocomponents of geothermal water) on the sorption recovery of iodide ions with 3-(octadecyldimethylammonio)propylsilica and 3-(trimethylammonio)propylsilica from aqueous solutions was studied. Sorption isotherms were discussed. The possibility of using 3-(octadecyldimethylammonio)-propylsilica for recovery of iodide ions from highly mineralized geothermal water was analyzed. 相似文献
127.
P. Rogl 《Monatshefte für Chemie / Chemical Monthly》1973,104(6):1623-1631
YbCo3B2, PrCo2B2 and HoCo2B2 have been prepared from the components. YbCo3B2 belongs to the ordered CaCu5-type structure, PrCo2B2 and HoCo2B2 crystallize with the ordered BaAl4-(ThCr2Si2)-type structure. The crystal chemistry of the isotypic series ofRECo3B2 as well as ofRECo2B2 compounds will be discussed.
Mit 2 Abbildungen
SE=Seltene Erde,RE=Rare Earth. 相似文献
Mit 2 Abbildungen
SE=Seltene Erde,RE=Rare Earth. 相似文献
128.
A solid phase synthesis of substituted quinolin-2(1H)-one-3-carboxylic acids is described. The products are formed in a two-step synthesis in which ortho-aminophenones are first coupled to malonic acid bound to the Wang Resin followed by ring closure via an intramolecular Knoevenagel condensation. 相似文献
129.
The isothermal section for the system Ce–Zn–B has been established at 800 °C using electron microprobe analysis and X-ray powder diffraction. No ternary compounds exist and mutual solid solubilities of binary phases are negligible. In the concentration range of 10.0–10.5 at% Ce two structural modifications have been confirmed: high temperature βCe2Zn17 above ∼750 °C with the Th2Zn17 type (R3?m, a=0.90916(4) nm, c=1.3286(1) nm) and low temperature αCeZn7 (Ce1−xZn5+2x; x∼0.33) up to 750 °C for which we attributed the TbCu7 type (P6/mmm, a=0.52424(2), c=0.44274(1) nm). The crystal structure of CeZn7 was derived from the Rietveld refinement of X-ray powder intensities. Precise data on atom site distribution and positional parameters have been furthermore provided from X-ray single crystal refinements for two compounds, for which crystal structures hitherto have only been derived from X-ray diffraction photographs: Ce3Zn11 (Immm, a=0.45242(2) nm, b=0.88942(3) nm, c=1.34754(4) nm) and Ce3Zn22 (I41/amd; a=0.89363(2) nm, c=2.1804(5) nm). 相似文献
130.
Billion‐Fold Enhancement in Sensitivity of Nuclear Magnetic Resonance Spectroscopy for Magnesium Ions in Solution
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Dr. Alexander Gottberg Dr. Monika Stachura Dr. Magdalena Kowalska Dr. Mark L. Bissell Dr. Vaida Arcisauskaite Prof. Klaus Blaum Alexander Helmke Dr. Karl Johnston Dr. Kim Kreim Prof. Flemming H. Larsen Prof. Rainer Neugart Prof. Gerda Neyens Ronald F. Garcia Ruiz Daniel Szunyogh Prof. Peter W. Thulstrup Dr. Deyan T. Yordanov Prof. Lars Hemmingsen 《Chemphyschem》2014,15(18):3929-3932
β‐nuclear magnetic resonance (NMR) spectroscopy is highly sensitive compared to conventional NMR spectroscopy, and may be applied for several elements across the periodic table. β‐NMR has previously been successfully applied in the fields of nuclear and solid‐state physics. In this work, β‐NMR is applied, for the first time, to record an NMR spectrum for a species in solution. 31Mg β‐NMR spectra are measured for as few as 107 magnesium ions in ionic liquid (EMIM‐Ac) within minutes, as a prototypical test case. Resonances are observed at 3882.9 and 3887.2 kHz in an external field of 0.3 T. The key achievement of the current work is to demonstrate that β‐NMR is applicable for the analysis of species in solution, and thus represents a novel spectroscopic technique for use in general chemistry and potentially in biochemistry. 相似文献