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71.
Cyclic Phosphidostannate(III) Anions [Sn12P24]36– in Sr3[Sn2P4] The metallic lustrous, air sensitive compound Sr3[Sn2P4] was prepared from melts of mixtures of the elements. Sr3[Sn2P4] crystallizes in the orthorhombic system, space group Cmca (a = 2510,4(9), b = 1259,3(6), c = 1869,3(8), Z = 24). In the anionic partial structure six moieties [Sn2P6] isostructural to Si2Cl6 are linked by each four common P-ligands forming cyclic units [Sn12P24]36–. The strontium cations are octahedrally coordinated by P. The arrangement can be described as a distorted cubic close packing of P3– in which in an ordered manner 3/4 of the octahedral vacancies are occupied by Sr2+ and 1/4 by Sn2-dumbbells. 相似文献
72.
Sarkar B Kaim W Klein A Schwederski B Fiedler J Duboc-Toia C Lahiri GK 《Inorganic chemistry》2003,42(20):6172-6174
The Ru(2)(III,II) mixed-valent state is strongly stabilized in [(bpy)(2)Ru(mu-bttz)Ru(bpy)(2)](5+) (3(5+), bttz = 3,6-bis(2-thienyl)-1,2,4,5-tetrazine, as evident from lowered oxidation potentials and isolability, a strongly increased comproportionation constant K(c) = 10(16.6), and a high-energy intervalence charge transfer band at 10100 cm(-1). Curiously, no such effects were observed for the diosmium(III,II) analogue, whereas the related systems [(bpy)(2)M(mu-bmptz)M(bpy)(2)](5+), bmptz = 3,6-bis(4-methyl-2-pyridyl)-1,2,4,5-tetrazine, exhibit conventional behavior, i.e., a slightly higher K(c) value of the Os(2)(III,II) analogue. EPR signals were observed at 4 K for 3(5+) but not for the other mixed-valent species, and high-frequency (285 GHz) EPR was employed to study the diruthenium(II) radical complexes 2(3+) and 3(3+). 相似文献
73.
Jacqueline Grewe Adelheid Hagenbach Brigitte Stromburg Roger Alberto Ezequiel Vazquez‐Lopez Ulrich Abram 《无机化学与普通化学杂志》2003,629(2):303-311
Novel rhenium(I) tricarbonyl complexes have been prepared by reactions of (Et4N)2[Re(CO)3Br3] with acetylpyridine benzoylhydrazone, Hapbhyd, di(2‐pyridyl)ketone benzoylhydrazone, Hpy2bhyd, bis(2‐pyridine)ketone, py2CO, and pyridinealdehyde terephtalaldehydebishydrazone, pytehyd. The ligands remain protonated when no supporting base is added and the following complexes have been isolated: [Re(CO)3Br(Hapbhyd)], [Re(CO)3Br(Hpy2bhyd‐py, hyd)], [Re(CO)3Br(Hpy2bhyd‐py1, py2)], [Re(CO)3Br(py2CO‐N, N)] and [Re(CO)3Br(pytehyd)]. Addition of triethyl amine results in deprotonation of Hapbhyd and the formation of [Re(CO)3(OH2)(apbhyd)], whereas Hpy2bhyd is hydrolysed and a rhenium complex with the monoanionic bis(2‐pyridyl)hydroxymethanolato ligand, {py2C(OH)O}‐, is formed. The same compound, [Re(CO)3{py2C(OH)O}], is obtained when triethyl amine and water are added to a mixture of (Et4N)2[Re(CO)3Br3] and py2CO. The air‐stable products have been studied by spectroscopic methods and X‐ray crystallography. 相似文献
74.
Pnictogenidostannates(IV) with Discrete Tetrahedral Anions: New Representatives (E1)4(E2)2[Sn(E15)4] (with E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) of the Na6[ZnO4] Type and the Superstructure Variant of K4Sr2[SnAs4] The silvery to dark metallic lustrous compounds (E1)4(E2)2[Sn(E15)4] (E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) were prepared from melts of stoichiometric mixtures of the elements. They crystallize in the Na6[ZnO4]‐type structure (hexagonal, space group: P63mc, Z = 2; Na4Ca2[SnP4]: a = 938.94(7), c = 710.09(8) pm; K4Sr2[SnAs4]: a = 1045.0(2), c = 767.0(1) pm; K4Ba2[SnP4]: a = 1029.1(6), c = 780.2(4) pm; K4Ba2[SnAs4]: a = 1051.3(1), c = 795.79(7) pm; K4Ba2[SnSb4]: a = 1116.9(2), c = 829.2(1) pm; K4Ba2[SnBi4]: a = 1139.5(2), c = 832.0(2) pm). The anionic partial structure consists of tetrahedra [Sn(E15)4]8– orientated all in the same direction along [001]. In the cationic partial structure one of the two cation positions is occupied statistically by alkali and alkaline earth metal atoms. Up to now only for K4Sr2[SnAs4] a second modification could be isolated, forming a superstructure type with three times the unit cell volume (hexagonal, space group: P63cm, Z = 6; a = 1801.3(2), c = 767.00(9) pm) and an ordered cationic partial structure. 相似文献
75.
Brigitte Defoort David Defoort Xavier Coqueret 《Macromolecular theory and simulations》2000,9(9):725-734
The thermal effects taking place during the electron beam‐induced polymerization of acrylate type formulations were numerically simulated on the basis of the general heat equation applied to a one‐dimensional system. The nature, the dimensions and the environment of the polymerizing medium were defined for representing the actual conditions of kinetic experiments performed with a 175 kV laboratory accelerator and FTIR monitoring. The modeled system was constituted of a polymerizable composition coated onto a NaCl plate, initially at 20°C in gaseous nitrogen at the same constant temperature, with or without a PET film covering the reactive layer. Polymerization profiles describing the progress of the reaction as a function of dose were modeled on a phenomenological basis from actual data obtained by discontinuous FTIR monitoring of typical epoxy acrylate or polyurethane acrylate compositions. The influence of the reactive layer thickness (10/100 μm), dose rate (10–110 kGy·s–1), maximum polymerization heat (200–400 J·g–1) on the temperature‐time variations was examined for continuous irradiation. In spite of the relatively small thickness of the reactive layer, significant temperature rise is simulated when heat production is large and fast compared to energy dissipation at the reactive layer boundaries. The obtained data substantiate the fact that upon fractionated EB‐treatment with small dose increments (down to 0.6 kGy per pass) at low dose rate (down to 10 kGy·s–1) the heat release can be considered weak and without noticeable influence on the conversion data processed for a detailed kinetic analysis. For example, a maximal temperature rise of 6°C was calculated for a fractionated irradiation of 2 kGy increments at 19 kGy·s–1 applied to a polymerizable formulation releasing a maximum enthalpy of 300 J·g–1. 相似文献
76.
Wex B Kaafarani BR Danilov EO Neckers DC 《The journal of physical chemistry. A》2006,110(51):13754-13758
Six aromatic compounds with embedded thiophenes differing in the number of rings (2-5) and thiophene orientation along the long axis of the molecule (syn, anti) were investigated. Photophysical properties, steady-state absorption, fluorescence, phosphorescence, lifetimes, quantum yields, and a comprehensive time-resolved spectroscopic analysis (femtosecond and nanosecond transient absorption spectroscopy) have been studied as a function of molecular structure. 相似文献
77.
78.
Christina Haberhauer-Troyer Marizela Delic Brigitte Gasser Diethard Mattanovich Stephan Hann Gunda Koellensperger 《Analytical and bioanalytical chemistry》2013,405(6):2031-2039
A novel method for the simultaneous quantification of both glutathione (GSH) and its oxidized form glutathione disulfide (GSSG) by hydrophilic interaction chromatography–MS/MS has been developed and is critically discussed. Internal standardization based on isotopically labeled standards for both analytes is an absolute prerequisite for accurate quantification of this redox pair. Hence, a highly efficient and selective miniaturized procedure for the synthesis of isotopically labeled GSSG from commercially available glutathione-(glycine-13C2,15N) was established using H2O2 as oxidant and NaI as catalyst. Moreover, a tool is presented to monitor and hence uncover artifactual GSSG formation due to oxidation of GSH during sample preparation, which is the main source of systematic error in GSSG analysis. For this purpose, we propose to monitor the oxidation product formed by reaction of naturally occurring GSH with the isotopically labeled GSH used as internal standard. For the determination of GSH/GSSG ratios in yeast, different extraction methods based on (1) hot extraction with aqueous, acidic, or organic solvents, (2) mechanical cell lysis, and (3) extraction at subambient temperature were investigated in terms of recovery, extraction efficiency, and artifactual formation of GSSG. Total combined uncertainties of as low as 25–30 % (coverage factor?=?2) for the determination of GSH/GSSG ratios without derivatization were made possible by the addition of the internal standards early in the analytical procedure (before extraction) and immediate analysis of the analytes. 相似文献
79.
80.