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141.
Laura I. Pera 《Journal of fluorine chemistry》2007,128(11):1425-1428
Fluoride (F−) is the predominant chemical form of F in serum and bone, during administration of NaF as cariostatic agent or in the treatment of osteoporosis. In the treatment with sodium monofluorophosphate (MFP), F−, F bound to proteins by acid-labile linkage and non-volatile covalently bound F are detected. Only F− is detectable with the ion-selective electrode. This paper describes a method for the measurement of non-volatile covalently bound F with the ion-selective electrode, which has a detection limit of 0.8 ± 0.6 nmol, within-run standard deviation of 7 nmol and a between-run standard deviation of 13 nmol at 100 nmol F and has a linear behaviour above 1 nmol. This paper also reports a methodology for the potentiometric measurement of F−, acid-labile F and covalently bound F in biological samples. 相似文献
142.
萃取光度法测定痕量氟的改进 总被引:2,自引:0,他引:2
本文提出一种新的测定痕量氟的萃取光度法,采用N,N-二甲苯胺作萃取剂,证实异戊醇进入萃取的多元络合物组成,以六偏酸钠和乙酰丙酮可消除多量铁、铝的干扰,生物样品则宜用过氧化氢及过氧化钠高压分解。本法可检测多种水样中10^-9级的氟,相对标准偏差〈2%。 相似文献
143.
Structures of LiCaAlF6 and LiSrAlF6 at 120 and 300 K by synchrotron X-ray single-crystal diffraction
Satoru Kuze Nobuo Ishizawa Nobuhiro Kodama Brian Henderson 《Journal of solid state chemistry》2004,177(10):3505-3513
The low-temperature structures of the colquiriite-type fluorides LiCaAlF6 and LiSrAlF6 have been investigated by single crystal X-ray diffraction. Molecular orbital calculations were also carried out using cluster models based on the obtained structures. The crystallographic c-axis at 120 K in LiSrAlF6 became slightly elongated with respect to the 300 K lattice and the structure became more distorted. In contrast, there was uniform lattice parameter contraction in LiCaAlF6 and the structure changed minimally between 300 and 120 K. These structural variations support other studies of temperature dependent optical properties reported in the literature. 相似文献
144.
Sergiy S. Mikhailichenko Vadim M. Timoshenko Yuriy G. Shermolovich Fabienne Grellepois 《Journal of fluorine chemistry》2007,128(7):703-709
Reactions of N-alkyl- or N-aryl(perfluoroalkyl)thiocarboxamides with alkyl lithium reagents are described. Trifluorothioacetamides are converted into the corresponding lithium salts. Compounds bearing a long polyfluorinated chain terminated by a CHF2 group and compounds containing an N-alkyl substituent with a proton adjacent to nitrogen react further via a multi-step reaction sequence involving HF elimination and then vinylic fluorine substitution and/or SN′ type fluorine substitution. These transformations led to unsaturated N-monosubstituted polyfluorinated thioamides. 相似文献
145.
Three novel uranyl complexes with organic phosphine oxide ligands and bridging fluorides have been synthesised and structurally characterised. In [ UO2(μ-F)(TPPO)3 2][BF4]2 · nC6H14, 1, and [ UO2(-μF)(TBPO)3 2][BF4]2 2, (where TPPO and TBPO are triphenylphosphine oxide and tri-n-butylphosphine oxide, respectively) two UO2 2+ moieties are bridged by two fluorides with three additional terminal PO donor ligands coordinated to each uranium centre. The dicationic complexes are both charge balanced by two uncoordinated tetrafluoroborate anions. In the related structure, [UO2(μ-F)(F)(DPPMO2)]2 · 2MeOH (3), terminal fluoride is also coordinated to both uranyl centres (where DPPMO2 = bis(diphenylphosphine oxide)methane). All three complexes were prepared during attempted syntheses of complexes with tetrafluoroborate directly coordinated to uranium. It is clear from these results that the fluorophilicity of UO2 2+ causes the abstraction of fluoride from [BF4]−, with the weakly coordinating anion only present as a counter cation in 1 and 2, and absent completely in 3. 相似文献
146.
Mohamed Ali Saada Annie Hémon-Ribaud Marc Leblanc 《Journal of fluorine chemistry》2005,126(8):1246-1251
Using tris(2-aminoethyl)amine [(C2H4NH2)3N] (tren) as a template, two new tantalum fluorides are obtained by slow evaporation of solutions: [H4tren](TaF7)2·H2O (I) and [H4tren](TaF7)2 (II). The structure determinations are performed by single crystal X-ray technique. Structures of I and II are built up from isolated TaF7 distorted monocapped trigonal prisms or pentagonal bipyramids; charge balance is achieved by tetraprotonated [H4tren]4+ cations which possess a “scorpion” configuration. In I and II, TaF7 polyhedra, connected by hydrogen bonds with water molecules in I, lie in corrugated layers; hydrogen bond networks ensure the cohesion between these layers and [H4tren]4+cations. 相似文献
147.
Thoralf Krahl 《Journal of fluorine chemistry》2006,127(6):663-678
Aluminium chlorofluoride, ACF, (AlClxF3−x, x ≈ 0.05-0.25) is an amorphous solid Lewis acid with an extraordinary acid strength that was patented by DuPont in 1992. It reaches the acidity of antimony pentafluoride, SbF5, and, in some cases, even exceeds it.In this review, an overview of known structural data of ACF and the corresponding bromine compound, ABF, is presented, together with additional unpublished data. This includes a discussion of soft chemistry synthesis, structure of bulk and surface, and Lewis acidities of molecular and solid group 13 halides. The order of Lewis acidity of gaseous halides is established to be AlF3(g) < AlCl3(g) < AlBr3(g) ≈ AlI3(g) and AlX3(g) > GaX3(g) > InX3(g) (X = F, Cl, Br, I).ACF and ABF are highly distorted solids. Different spectroscopic bulk methods show that the heavy halogen, chlorine or bromine, is a necessary perturbation that generates “disorder”. Highly Lewis acidic centres have been detected by several methods on the surface of ACF and ABF, which are responsible for the high catalytic reactivity observed in many reactions.The data gained on ACF and ABF show that many published data about heterogeneously catalysed fluorine-halogen exchange reactions in presence of aluminium chloride and bromide must be treated critically. In general, ACF and ABF are the active species. 相似文献
148.
在氟铝酸盐玻璃组分中加入适量声子能量低的重金属氧化物TeO
2,得到一种新的氧氟化物玻璃。该材料具有良好的成玻璃性能,适合制作大尺寸红外窗口镜。研究了TeO2含量对玻璃特征温度、阿贝数和红外透过性能的影响。同时测试了这种玻璃的抗DF激光能力,结果表明: TeO
2含量为15%的玻璃,DF激光破坏阈值达14.95 kW·cm-2。分析显示,由于玻璃基质的多声子吸收,对激光能量的吸收而引起的热冲击是导致玻璃破坏的主要原因。进一步降低玻璃中水分,可以提高玻璃抗激光破坏性能。 相似文献
149.
150.
Kx(MgxIn1–x)F3 (x = 0.38) is monoclinic, pseudo tetragonal: a = 12.781(2) Å, b = 12.787(2) Å, c = 7.930(1) Å, β = 90,00(1)°, Z = 20. The crystal structure was solved in the space group P21/a (No. 14), subgroup of the tetragonal space group P4/mbm (No. 127), from X‐ray single crystal data using 4302 unique reflections (1770 with Fo/σ(Fo) > 4). The final observed R factor is 0.053. Kx(MgxIn1–x)F3 has the Magnéli‐bronze structural type, which consists in a tridimensional framework of mixed [(MgxIn1–x)F6] octahedra linked together by corners. The potassium ions are mainly located in large almost fully occupied 15‐coordinated sites and in practically empty 12‐coordinated cavities. 相似文献