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921.
Dr. Emmanouil Zacharioudakis Poonam Agarwal Dr. Alexandra Bartoli Nathan Abell Lavaniya Kunalingam Dr. Valérie Bergoglio Dr. Blerta Xhemalce Dr. Kyle M. Miller Dr. Raphaël Rodriguez 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6583-6587
Cisplatin derivatives can form various types of DNA lesions (DNA-Pt) and trigger pleiotropic DNA damage responses. Here, we report a strategy to visualize DNA-Pt with high resolution, taking advantage of a novel azide-containing derivative of cisplatin we named APPA, a cellular pre-extraction protocol and the labeling of DNA-Pt by means of click chemistry in cells. Our investigation revealed that pretreating cells with the histone deacetylase (HDAC) inhibitor SAHA led to detectable clusters of DNA-Pt that colocalized with the ubiquitin ligase RAD18 and the replication protein PCNA. Consistent with activation of translesion synthesis (TLS) under these conditions, SAHA and cisplatin cotreatment promoted focal accumulation of the low-fidelity polymerase Polη that also colocalized with PCNA. Remarkably, these cotreatments synergistically triggered mono-ubiquitination of PCNA and apoptosis in a RAD18-dependent manner. Our data provide evidence for a role of chromatin in regulating genome targeting with cisplatin derivatives and associated cellular responses. 相似文献
922.
Pablo Ballester Mickaël Claudel Stéphanie Durot Lucas Kocher Laetitia Schoepff Valérie Heitz 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(43):15339-15348
The synthesis of a zinc(II) porphyrin 1 with four appended triazolyl–pyridine chelates is reported. Complexation of the porphyrin peripheral ligands with AgI ions in a 1:2 binding stoichiometry afforded quantitatively the coordination cage [Ag4( 1 )2]4+. The assembly and disassembly processes of the cage were investigated in solution using UV/Vis spectroscopy. The mathematical analysis of the data obtained in the UV/Vis titration of 1 with AgI confirmed the assembly in CH2Cl2/MeOH (90:10) solution of a species having a 1:2 porphyrin/silver stoichiometry and assigned to it an overall stability constant of 5.0×1026 M ?5. The use of a model system allowed an independent assessment of a microscopic binding constant value (Km) for the interaction between the triazolyl‐pyridine ligand and AgI. The coincidence that existed between the Km values extracted from the model system and the titration of 1 provided an indication of the quality and fit of the data analysis. It also allowed the calculation of the average effective molarity (EM) value for the three intramolecular processes that led to the cage assembly as 2.6 mM . Simulated speciation profiles supported the conclusion that at millimolar concentration and working under strict stoichiometric control of the silver/porphyrin ratio, the cage [Ag4( 1 )2]4+ was the species exclusively assembled in solution. On the other hand, when the concentration of added AgI was approximately 2.6 mM , 50 % of the coordination cage disassembled into open aggregates. 相似文献
923.
Stereospecific Synthesis of α‐ and β‐Hydroxyalkyl P‐Stereogenic Phosphine–Boranes and Functionalized Derivatives: Evidence of the PO Activation in the BH3‐Mediated Reduction
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Sébastien Lemouzy Dr. Duc Hanh Nguyen Valentine Camy Marion Jean Dr. David Gatineau Dr. Laurent Giordano Dr. Jean‐Valère Naubron Dr. Nicolas Vanthuyne Dr. Damien Hérault Prof. Gérard Buono 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15607-15621
Access to hydroxy‐functionalized P‐chiral phosphine–boranes has become an important field in the synthesis of P‐stereogenic compounds used as ligands in asymmetric catalysis. A family of optically pure α and β‐hydroxyalkyl tertiary phosphine–boranes has been prepared by using a three‐step procedure from readily accessible enantiopure adamantylphosphinate, obtained by semi‐preparative HPLC on multigram scale. Firstly, a two‐step one‐pot transformation affords the enantiopure hydroxyalkyl tertiary phosphine oxides in good yields and enantioselectivities. The third step, BH3‐mediated reduction, allows the formation of the desired phosphine–boranes with excellent stereospecifity. The mechanistic study of this reduction provides new evidence to elucidate the crucial role of the pendant hydroxy group and the subsequent activation of the P?O bond by the boron atom. 相似文献
924.
We consider the motion of a three-degree-of-freedom gyro with an electric spring and with zero angular momentum mounted on a fixed base. The gimbal rotation angles are constrained by an elastic ring that is attached to the base and confines a rod attached to the internal gimbal. The equations of motion of the gyro are supplemented with equations allowing for the delay in the response of the gyro feedback circuit. By numerical integration we find a steady-state mode of the gyro motion, in which the rod alternately slides along the ring and moves in the interior of the ring. This motion can be used to check the gyro performance after launching a spacecraft to a near-Earth orbit by comparing the gyro motions in ground tests and on the orbit. 相似文献
925.
Insights into the Mechanism of Extraction of Uranium (VI) from Nitric Acid Solution into an Ionic Liquid by using Tri‐n‐butyl phosphate
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Dr Clotilde Gaillard Dr. Maria Boltoeva Dr. Isabelle Billard Sylvia Georg Valérie Mazan Dr. Ali Ouadi Dr. Dariia Ternova Dr. Christoph Hennig 《Chemphyschem》2015,16(12):2653-2662
We present new results on the liquid–liquid extraction of uranium (VI) from a nitric acid aqueous phase into a tri‐n‐butyl phosphate/1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide (TBP/[C4mim][Tf2N]) phase. The individual solubilities of the ionic‐liquid ions in the upper part of the biphasic system are measured over the whole acidic range and as a function of the TBP concentration. New insights into the extraction mechanism are obtained through the in situ characterization of the extracted uranyl complexes by coupling UV/Vis and extended X‐ray absorption fine structure (EXAFS) spectroscopy. We propose a chemical model to explain uranium (VI) extraction that describes the data through a fit of the uranyl distribution ratio DU. In this model, at low acid concentrations uranium (VI) is extracted as the cationic complex [UO2(TBP)2]2+, by an exchange with one proton and one C4mim+. At high acid concentrations, the extraction proceeds through a cationic exchange between [UO2(NO3)(HNO3)(TBP)2]+ and one C4mim+. As a consequence of this mechanism, the variation of DU as a function of TBP concentration depends on the C4mim+ concentration in the aqueous phase. This explains why noninteger values are often derived by analysis of DU versus [TBP] plots to determine the number of TBP molecules involved in the extraction of uranyl in an ionic‐liquid phase. 相似文献
926.
927.
Valérie Marchal Frédérique Barbier Frédéric Plassard R. Faure Olivier Vittori 《Analytical and bioanalytical chemistry》1999,363(7):710-712
Sodium activated Bentonite, a sodium modified Montmorillonite, was submitted to cadmium sorption from nitrate solutions in
order to simulate a cadmium polluted clay mineral. The remaining cadmium concentration in solution was analyzed at equilibrium
by means of Differential Pulse Polarography (DPP) in order to calculate the cadmium concentration sorbed by the clay. The
cadmium distribution between clay mineral and solution was observed for different concentrations, showing a Freundlich sorption
profile. The clay mineral, previously submitted to the cadmium sorption procedure, was included in a carbon paste in order
to investigate the cadmium content by voltammetric determination. For cadmium detection in Bentonite, a linear response of
the carbon paste electrode (CPE) was observed in the 5 · 10–5– 1.8 · 10–4 mol/g range with good reproducibility.
Received: 23 July 1998 / Revised: 19 November 1998 / Accepted: 26 November 1998 相似文献
928.
Dr. Letícia F. Sosa Dr. Priscilla M. de Souza Dr. Raphaela A. Rafael Dr. Robert Wojcieszak Dr. Eric Marceau Prof. Dr. Sébastien Paul Dr. Valérie Briois Prof. Dr. Fabio B. Noronha Prof. Dr. Fabio S. Toniolo 《ChemCatChem》2024,16(2):e202300890
The hydrodeoxygenation of furfural (FF) over Mo carbides in liquid phase at 200 °C, 30 bar of H2 for 4 h in 2-butanol was investigated. Unsupported and SiO2-supported Mo carbide with different crystallographic phases (β-Mo2C/SiO2 and α-MoC/SiO2), and in the presence of Cu and Ni as promoters were studied. The reactivation treatment under H2 atmosphere of the passivated Mo carbides was investigated by XAS. The results show that Mo is present in different states of oxidation in the passivated catalysts, with more severe oxidation in the bimetallic systems, in which the original carbides are not restored after reactivation. Finally, the product distribution in the HDO of furfural is modified as a function of catalyst oxidation degree. Using the less oxidized Mo carbide (β-Mo2C), a higher yield to 2-methylfuran is obtained, while C10 condensation products are formed for the more oxidized catalysts. 相似文献
929.
Robert Brüll Valérie Grumel Harald Pasch Helgard G. Raubenheimer Ron Sanderson Udo M. Wahner 《Macromolecular Symposia》2002,178(1):81-92
Crystallization analysis fractionation (CRYSTAF) has been introduced for the analysis of the composition of polyolefin blends and the chemical composition distribution of polyolefins. Blends of syndiotactic and isotactic polypropylene (sPP and iPP) and of sPP/High density polyethylene (HDPE) have been fractionated by CRYSTAF and the results been compared to those from DSC. While the blends of sPP and HDPE cannot be separated by DSC a quantitative determination of both components is possible by CRYSTAF over the whole range with the detection limit being 1% on both ends. Furthermore it is demonstrated that the separation of ternary blends of sPP, iPP and HDPE is possible by CRYSTAF. 相似文献
930.
Sauvinet V Parrot S Benturquia N Bravo-Moratón E Renaud B Denoroy L 《Electrophoresis》2003,24(18):3187-3196
gamma-Aminobutyric acid (GABA), glutamate (Glu), and L-aspartate (L-Asp) are three major amino acid neurotransmitters in the central nervous system. In this work, a method for the separation of these three neurotransmitters in brain microdialysis samples using a commercially available capillary electrophoresis (CE) system has been developed. Molecules were tagged on their primary amine function with the fluorogene agent naphthalene-2,3-dicarboxaldehyde (NDA), and, after separation by micellar electrokinetic chromatography, were detected by laser-induced fluorescence using a 442 nm helium-cadmium laser. The separation conditions for the analysis of derivatized neurotransmitters in standard solutions and microdialysates have been optimized, and this method has been validated on both pharmacological and analytical basis. The separation of GABA, Glu, and L-Asp takes less than 10 min by using a 75 mmol/L borate buffer, pH 9.2, containing 70 mmol/L SDS and 10 mmol/L hydroxypropyl-beta-cyclodextrin and + 25 kV voltage. The detection limits were 3, 15 nmol/L and, 5 nmol/L for GABA, Glu, and L-Asp, respectively. Moreover, submicroliter samples can be analyzed. This method allows a simple, rapid and accurate measurement of the three amino acid neurotransmitters for the in vivo brain monitoring using microdialysis sampling. 相似文献