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排序方式: 共有425条查询结果,搜索用时 46 毫秒
81.
Tonya Vitova Radmila Faizova Jorge I. Amaro-Estrada Laurent Maron Tim Pruessmann Thomas Neill Aaron Beck Bianca Schacherl Farzaneh Fadaei Tirani Marinella Mazzanti 《Chemical science》2022,13(37):11038
The stabilization of uranyl(v) (UO21+) by Fe(ii) in natural systems remains an open question in uranium chemistry. Stabilization of UVO21+ by Fe(ii) against disproportionation was also demonstrated in molecular complexes. However, the relation between the Fe(ii) induced stability and the change of the bonding properties have not been elucidated up to date. We demonstrate that U(v) – oaxial bond covalency decreases upon binding to Fe(ii) inducing redirection of electron density from the U(v) – oaxial bond towards the U(v) – equatorial bonds thereby increasing bond covalency. Our results indicate that such increased covalent interaction of U(v) with the equatorial ligands resulting from iron binding lead to higher stability of uranyl(v). For the first time a combination of U M4,5 high energy resolution X-ray absorption near edge structure (HR-XANES) and valence band resonant inelastic X-ray scattering (VB-RIXS) and ab initio multireference CASSCF and DFT based computations were applied to establish the electronic structure of iron-bound uranyl(v).The role of Fe in the increased stability of uranyl(v) is clarified by using state of the art uranium metalorganic chemistry, advanced X-ray spectroscopic approaches and computations. 相似文献
82.
Mohammad B. Haskali Peter D. Roselt Terence J. OBrien Craig A. Hutton Idrish Ali Lucy Vivash Bianca Jupp 《Molecules (Basel, Switzerland)》2022,27(18)
(1) Background: [18F]Flumazenil 1 ([18F]FMZ) is an established positron emission tomography (PET) radiotracer for the imaging of the gamma-aminobutyric acid (GABA) receptor subtype, GABAA in the brain. The production of [18F]FMZ 1 for its clinical use has proven to be challenging, requiring harsh radiochemical conditions, while affording low radiochemical yields. Fully characterized, new methods for the improved production of [18F]FMZ 1 are needed. (2) Methods: We investigate the use of late-stage copper-mediated radiofluorination of aryl stannanes to improve the production of [18F]FMZ 1 that is suitable for clinical use. Mass spectrometry was used to identify the chemical by-products that were produced under the reaction conditions. (3) Results: The radiosynthesis of [18F]FMZ 1 was fully automated using the iPhase FlexLab radiochemistry module, affording a 22.2 ± 2.7% (n = 5) decay-corrected yield after 80 min. [18F]FMZ 1 was obtained with a high radiochemical purity (>98%) and molar activity (247.9 ± 25.9 GBq/µmol). (4) Conclusions: The copper-mediated radiofluorination of the stannyl precursor is an effective strategy for the production of clinically suitable [18F]FMZ 1. 相似文献
83.
Dr. P. Seidler 《Analytical and bioanalytical chemistry》1883,22(1):529-530
84.
Hermann Seidler 《Fresenius' Journal of Analytical Chemistry》1877,16(1):198-199
Ohne Zusammenfassung 相似文献
85.
Alessandro D’Aprano Bianca Sesta Noemi Proietti Vincenzo Mauro 《Journal of solution chemistry》1997,26(6):649-662
Conductivity measurements, focused on the counterion binding of lithium perfluorononanoate (LiPFN) micelles in pure water
and in the presence of poly(vinyl pyrrolidone) (PVP), have been carried out. An abrupt decrease of the conductance of the
LiPFN in pure water, due to the self aggregation of anions and to dynamic linkage of cations on the micellar surface, has
been found. Analysis of the conductometric data indicates that about 50% of the stoichiometric concentration of Li+ interacts with the head groups of the perfluorinated anions involved in micellar assembly. Conductometric data of LiPFN-water-PVP
systems reveals a favorable influence of the PVP on the micellization process modulated by the concentration and by the molecular
weight of the polymer. Analysis of these data shows that in presence of PVP the degree of binding of lithium ion to the micellar
assemblies linked to the polymer is smaller than in pure water. By increasing the amount of surfactant in solution up to the
concentration where the polymer becomes saturated by LiPFN micelles, the binding of lithium ion in the system becomes slightly
greater than that observed in LiPFN-water system. This finding can be interpreted in terms of additional binding of lithium
ion to the polymer chains. Conductivity measurements carried out on LiClO4 and KClO4 in water + PVP support this interpretation. 相似文献
86.
Ribicki Ariane Caroline Chemin Bianca Gurski Van Haandel Viviane Jandira Winiarski João Paulo de Castro Rozada Thiago Pessoa Christiana Andrade Estrada Ruben Auccaise Fiorin Barbara Celânia Fujiwara Sérgio Toshio 《Journal of Sol-Gel Science and Technology》2018,87(1):216-229
Journal of Sol-Gel Science and Technology - A silsesquioxane based on a silica matrix and 4-(aminomethyl)pyridine group was successfully synthesized using the sol–gel process with the... 相似文献
87.
Scrimin P Tecilla P Tonellato U Verzini M Andreini BP Coutant JE Zerilli LF 《The Journal of organic chemistry》1996,61(18):6268-6272
The thermodynamics and kinetics of binding of model tripeptides epsilon-N-acetyl-alpha-N-dansyl-L-Lys-D-Ala-D-Ala (ADLAA) or alpha-N,epsilon-N-diacetyl-L-Lys-D-Ala-D-Ala (AALAA) to teicoplanin (1a) and a series of semisynthetic derivatives with (1b-f) or devoid of (2a-g) the glycidic side arms and modified at the terminal amino acids of the peptide backbone have been studied by fluorescence or UV spectroscopy. The binding process is suggested to occur via a two-step mechanism. The first, fast process is likely governed by an electrostatic interaction between the C- and N-termini of the peptide chain of the substrate and of the antibiotic, respectively, while the second slower one, accounts for the formation of the hydrogen bonds responsible of the major contribution to the overall binding energy. The binding constants with all modified derivatives are smaller than that with native teicoplanin. Larger modification of the overall binding constant are observed when the sugar residues are removed and, to a lower extent, when the N-terminus of the peptide chain is acylated. The kinetic process is very little affected by the modifications introduced. 相似文献
88.
A simple and rapid method was developed for the determination of 20 antibiotics (sulfonamides, tetacyclines, and flumequine) in honey by liquid chromatography tandem mass spectrometry. The proposed method is sensitive (limit of detection 0.5 to 10 ppb for the various antibiotics) and selective. A hydrolysis step ensures the liberation of sugar-bound sulfonamides. The approach has been used to analyze some 300 honey samples. A number of them were found to have exceeded the Swiss limit of 50 ppb. 相似文献
89.
Angelo Albert Francesco Paolo Colonna Maurizio Guerra Bianca F. Bonini Germana Mazzanti Zoltàn Dinya Gian Franco Pedulli 《Journal of organometallic chemistry》1981,221(1):47-55
The radical adducts resulting from the reaction between group IVB organometallic radicals MR3 (M = Si, Ge, Sn; R = alkyl or aryl) and a number of thioketones of the chromone and flavone series have been investigated by ESR spectroscopy. The spectral parameters obtained for these species have been compared with those of similar adducts of the corresponding ketones. Both classes of radicals adopt an orthogonal conformation, and the differences between the former and the latter paramagnetic species can be accounted for by the different electronegativity of oxygen and sulphur. the effects of substitution of the heterocyclic oxygen with a sulphur or selenium atom on the spin density distribution are likewise explained. INDO calculations have been carried out on the model systems CH2XSiH3 (X = O, S). 相似文献
90.
Bruna Bovio
Sandro Calogero
Friedrich E. Wagner
Alfredo Burini
Bianca Rosa Pietroni 《Journal of organometallic chemistry》1994,470(1-2):275-283Reactions of the trinuclear [Au3Rim3] compound (Rim = [μ-1-benzylimidazolato-N3,C2] with several reagents capable of oxidative addition have been investigated by 197Au Mössbauer spectroscopy. The reaction products are either AuI carbene mononuclear and binuclear complexes or trinuclear AuIII and mixed-valence compounds. The X-ray crystal structure of the mixed-valence complex [AuIIIAuI2Rim3I2] has been determined. Two two-coordinate AuI centres show average Au---C and Au---N distances of 2.02(3) and 2.04(2) Å and average C---Au---N angles of 175.0(1.2)°, whereas the four-coordinate AuIII centre gives Au---C and Au---N 1.96(4) and 1.91(3) Å with the C---Au---N angle 170.5(1.6)°, and Au---I average distances 2.598(3) Å, with an I---Au=I angle 175.8(1)°. The Au---Au intramolecular distances [Au(1) Au(2) 3.432(3), Au(1) Au(3) 3.508(3), Au(2) Au(3) 3.464(3) Å] indicate a weak metal-metal interaction. 相似文献