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71.
The hexaaminecobalt(III) complex [Co(tmptacn)]3+ (tmptacn = 1,4,7-tris(2'-pyridylmethyl)-1,4,7-triazacyclononane) undergoes a novel base-catalyzed N- to C-bonded rearrangement in which a tacn nitrogen is displaced by the alpha-carbon which deprotonates and binds to the metal ion as a carbanion. The X-ray structure establishes the configuration for the regio- and stereoselectively (100%) formed product. The reaction involves both ring expansions and ring contraction. The carbanion is part of a strained four-membered ring. The kinetics are reported for the N- to C-rearrangement, shown to be retentive for the optically resolved (+)-[Co(tmptacn)]3+ reactant, and also the kinetics for a competitive and somewhat faster base-catalyzed racemization reaction of this complex. The reaction is completely but very slowly reversed in acid, also with retention, and in D2O/D+ there is 1:1 D-incorporation into the two sets of inequivalent tacn carbons. Extensive 1D and 2D NMR studies establish mechanistic details, and alternative mechanisms are proposed for the forward and reverse reactions. In neutral solution, there is a competitive oxidation reaction for the reverse C- to N-bonded process, involving the regio- and stereoselective (100%) incorporation of an alpha-OH substituent into the tacn ring. 相似文献
72.
Dr. Maria Gil-Moles Sebastian Türck Dr. Uttara Basu Dr. Andrea Pettenuzzo Dr. Saurav Bhattacharya Ananthu Rajan Xiang Ma Rolf Büssing Jessica Wölker Dr. Hilke Burmeister Henrik Hoffmeister Pia Schneeberg Andre Prause Petra Lippmann Josephine Kusi-Nimarko Dr. Storm Hassell-Hart Dr. Andrew McGown Dr. Daniel Guest Dr. Yan Lin Dr. Anna Notaro Dr. Robin Vinck Dr. Johannes Karges Dr. Kevin Cariou Dr. Kun Peng Dr. Xue Qin Dr. Xing Wang Dr. Joanna Skiba Dr. Łukasz Szczupak Prof. Dr. Konrad Kowalski Prof. Dr. Ulrich Schatzschneider Dr. Catherine Hemmert Prof. Dr. Heinz Gornitzka Prof. Dr. Elena R. Milaeva Dr. Alexey A. Nazarov Prof. Dr. Gilles Gasser Prof. Dr. John Spencer Dr. Luca Ronconi Prof. Dr. Ulrich Kortz Prof. Dr. Jindrich Cinatl Prof. Dr. Denisa Bojkova Prof. Dr. Ingo Ott 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(71):17928-17940
The global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has called for an urgent need for dedicated antiviral therapeutics. Metal complexes are commonly underrepresented in compound libraries that are used for screening in drug discovery campaigns, however, there is growing evidence for their role in medicinal chemistry. Based on previous results, we have selected more than 100 structurally diverse metal complexes for profiling as inhibitors of two relevant SARS-CoV-2 replication mechanisms, namely the interaction of the spike (S) protein with the ACE2 receptor and the papain-like protease PLpro. In addition to many well-established types of mononuclear experimental metallodrugs, the pool of compounds tested was extended to approved metal-based therapeutics such as silver sulfadiazine and thiomersal, as well as polyoxometalates (POMs). Among the mononuclear metal complexes, only a small number of active inhibitors of the S/ACE2 interaction was identified, with titanocene dichloride as the only strong inhibitor. However, among the gold and silver containing complexes many turned out to be very potent inhibitors of PLpro activity. Highly promising activity against both targets was noted for many POMs. Selected complexes were evaluated in antiviral SARS-CoV-2 assays confirming activity for gold complexes with N-heterocyclic carbene (NHC) or dithiocarbamato ligands, a silver NHC complex, titanocene dichloride as well as a POM compound. These studies might provide starting points for the design of metal-based SARS-CoV-2 antiviral agents. 相似文献
73.
Rebecca L. Edwards Paul Griffiths Josephine Bunch Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2012,23(11):1921-1930
We have previously shown that liquid microjunction surface sampling of dried blood spots coupled with high resolution top-down mass spectrometry may be used for screening of common hemoglobin variants HbS, HbC, and HbD. In order to test the robustness of the approach, we have applied the approach to unknown hemoglobin variants. Six neonatal dried blood spot samples that had been identified as variants, but which could not be diagnosed by current screening methods, were analyzed by direct surface sampling top-down mass spectrometry. Both collision-induced dissociation and electron transfer dissociation mass spectrometry were employed. Four of the samples were identified as ??-chain variants: two were heterozygous Hb D-Iran, one was heterozygous Hb Headington, and one was heterozygous Hb J-Baltimore. The fifth sample was identified as the ??-chain variant heterozygous Hb Phnom Penh. Analysis of the sixth sample suggested that it did not in fact contain a variant. Adoption of the approach in the clinic would require speed in both data collection and interpretation. To address that issue, we have compared manual data analysis with freely available data analysis software (ProsightPTM). The results demonstrate the power of top-down proteomics for hemoglobin variant analysis in newborn samples. 相似文献
74.
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76.
Rory T. Steven Alan M. Race Josephine Bunch 《Journal of the American Society for Mass Spectrometry》2013,24(5):801-804
para-Nitroaniline (PNA) is presented as a promising matrix for matrix-assisted laser desorption ionization mass spectrometry imaging (MALDI-MSI) on an intermediate-pressure ion source (~1 Torr) QqTOF instrument using an Nd:YVO4 laser operated at 5 kHz. An imaging study was carried out to determine the utility of PNA at this pressure by analyzing 14 tissue sections. We demonstrate acquisition of high-quality imaging data over a 6-h period in the ion source. In this study, comparisons were made between PNA and α-cyano-4-hydroxycinnamic acid (CHCA) in positive ion mode to demonstrate the utility of PNA in these circumstances. PNA performed as well as or better than CHCA in terms of lipid ion intensities, resulting in lower levels of ion fragmentation and in lower incidences of analyte migration at the edges of the tissue sections when using airspray matrix deposition. 相似文献
77.
New trends in fast and high-resolution liquid chromatography: a critical comparison of existing approaches 总被引:1,自引:0,他引:1
Davy Guillarme Josephine Ruta Serge Rudaz Jean-Luc Veuthey 《Analytical and bioanalytical chemistry》2010,397(3):1069-1082
Recent developments in chromatographic supports and instrumentation for liquid chromatography (LC) are enabling rapid and
highly efficient separations. Various analytical strategies have been proposed, for example the use of silica-based monolithic
supports, elevated mobile phase temperatures, and columns packed with sub-3 μm superficially porous particles (fused core)
or with sub-2 μm porous particles for use in ultra-high-pressure LC (UHPLC). The purpose of this review is to describe and
compare these approaches in terms of throughput and resolving power, using kinetic data gathered for compounds with molecular
weights ranging between 200 and 1300 g mol−1 in isocratic and gradient modes. This study demonstrates that the best analytical strategy should be selected on the basis
of the analytical problem (e.g., isocratic vs. gradient, throughput vs. efficiency) and the properties of the analyte. UHPLC
and fused-core technologies are quite promising for small-molecular-weight compounds, but increasing the mobile phase temperature
is useful for larger molecules, for example peptides. 相似文献
78.
Irving J. Bordwitz Grace B. Bordwitz Ven Shun Li Josephine D. Readio Antonia Lewis Teresa Karcnik 《Journal of inclusion phenomena and macrocyclic chemistry》1990,9(3):227-230
The synthesis ofN-(2-hydroxy-l-phenoxyacetyl)glycylglycine3 from 2-acetoxyphenoxyacetic acid is described. Compound3, a simple model for the carboxy-containing ionophore, Lasalocid, binds cations in methanol in the order: Ca2+ Ba2+ > Sr2+ 2>> Li+ > Na+, K+. 相似文献
79.
Daniel C. Harris Josephine Covino Marian E. Hills Robert W. Schwartz 《Journal of Physics and Chemistry of Solids》1985,46(5):619-624
Calcium sulfide powder containing iron as an impurity was irradiated with 580, 366 or 254 nm light at 77 K. Irradiation enhanced a broad (16 G peak-to-trough) electron paramagnetic resonance (EPR) signal at g = 2.017 and caused six sharp (~1 G) lines to appear in the X-band EPR spectrum at 347, 529, 956, 1963, 3547 and 5376 G. Enrichment of CaS with Fe2+ produced samples with similar photochemistry. It is proposed that irradiation causes the reaction Fe2+ + trap → Fe3+ + trap?, whose products give rise to six sharp EPR lines assigned to Fe3+ and a broad line associated with trap?. Both hyperfine splitting by 57Fe (13 G) and superhyperfine splitting by 33S (11.4 G) are observed in the six line spectrum. The environment of the photo-generated Fe3+ has less than octahedral symmetry. V2+ was observed at octahedral sites in unirradiated CaS for the first time, and is characterized by the EPR parameters g = 1.961 and A (hyperfine coupling) = 74.6 × 10?4 cm?1. EPR signals due to Mn2+ and Cr3+ at octahedral sites and Fe3+ at a low symmetry site were also observed in unirradiated CaS. 相似文献
80.