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991.
Overcoming the Unexpected Functional Inversion of a PqsR Antagonist in Pseudomonas aeruginosa: An In Vivo Potent Antivirulence Agent Targeting pqs Quorum Sensing 下载免费PDF全文
Cenbin Lu Christine K. Maurer Benjamin Kirsch Dr. Anke Steinbach Prof. Dr. Rolf W. Hartmann 《Angewandte Chemie (International ed. in English)》2014,53(4):1109-1112
The virulence regulator PqsR of Pseudomonas aeruginosa is considered as an attractive target for attenuating the bacterial pathogenicity without eliciting resistance. However, despite efforts and desires, no promising PqsR antagonist has been discovered thus far. Now, a surprising functionality change of a highly affine PqsR antagonist in P. aeruginosa is revealed, which is mediated by a bacterial signal molecule synthase and responsible for low cellular potency. Blockade of the susceptible position led to the discovery of the first antivirulence compound that is potent in vivo and targets PqsR, thus providing a proof of concept for this novel antivirulence therapy. 相似文献
992.
Inside Cover: Identification and X‐ray Co‐crystal Structure of a Small‐Molecule Activator of LFA‐1‐ICAM‐1 Binding (Angew. Chem. Int. Ed. 17/2014) 下载免费PDF全文
993.
Artificial Iono‐ and Photosensitive Membranes Based on an Amphiphilic Aza‐Crown‐Substituted Hemicyanine 下载免费PDF全文
Dr. Pinar Batat Dr. Christine Grauby‐Heywang Dr. Sophiya Selektor Daria Silantyeva Prof. Vladimir Arslanov Dr. Nathan McClenaghan Dr. Gediminas Jonusauskas 《Chemphyschem》2014,15(13):2823-2833
Artificial iono‐ and photosensitive membranes based on an amphiphilic aza‐crown‐substituted hemicyanine are assembled on liquid and solid supports and their aggregation behaviour, which is influenced by the binding of metal cations and surface density, is studied. The photoinduced charge‐transfer properties of an analogous non‐amphiphilic hemicyanine in solution are also demonstrated. An asymmetric sandwich dimer model is proposed and existence of such dimers in solution is evidenced by transient absorption and fluorescence anisotropy experiments. Changes in absorption and emission spectra, as well as compression isotherms of the amphiphile observed in the presence of cations, are discussed in terms of 2D molecular reorganisation. Surface‐pressure‐controlled reversible excimer formation at the air–water interphase and excimer‐type emission of Langmuir–Blodgett films in the presence of cations are demonstrated and are discussed on the basis of fibre‐optic fluorimetry and fluorescence microscopy results. 相似文献
994.
Christine Artner Matthias Czakler Prof. Dr. Ulrich Schubert 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(2):493-498
Mixed‐metal clusters have been obtained from the reaction of titanium alkoxides with either strontium or lead acetate and methacrylic acid. The structures of the clusters are derived from the metallacycle Ti8O8(methacrylate)16. The Sr and Pb atoms in Sr2Ti8O8X2(OOCMe)2(methacrylate)16 (X: acetate or OiPr) and Pb2Ti8O8(OBu)2X2(methacrylate)16(BuOH)2 (X: acetate or methacrylate) occupy the central cavity of the Ti8O8 ring. In addition to the crown‐ether‐like coordination of the ring oxygen atoms to the Sr or Pb atoms, bridging carboxylate ligands support the coordination of the latter atoms. In the compound Pb2Ti6O5(OiPr)3X(methacrylate)14 (X: OiPr or methacrylate), the lead atoms are coordinated by a fragment of the Ti8O8(methacrylate)16 metallacycle. 相似文献
995.
Tuning the Guest‐Binding Ability of a Helically Folded Capsule by In Situ Modification of the Aromatic Oligoamide Backbone 下载免费PDF全文
Dr. Guillaume Lautrette Dr. Christophe Aube Dr. Yann Ferrand Dr. Muriel Pipelier Dr. Virginie Blot Dr. Christine Thobie Dr. Brice Kauffmann Prof. Didier Dubreuil Dr. Ivan Huc 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1547-1553
Starting from a previously described aromatic oligoamide helically folded capsule that binds tartaric acid with high affinity and diastereoselectivity, we demonstrate the feasibility of the direct in situ modification of the helix backbone, which results in a conformational change that reduces its affinity for guests by two orders of magnitude. Specifically, ring contraction of the central pyridazine unit into a pyrrole in the full helical sequence was investigated by using electrochemical and chemical processes. The sequence containing the pyrrole was synthesized independently in a convergent manner to ascertain its structure. The conformation of the pyrrolic folded capsule was elucidated in the solid state by X‐ray crystallography and in solution by using 1H and 13C NMR spectroscopy. Solution studies revealed an unanticipated solvent‐dependent equilibrium between the anti–anti and syn–syn conformations of the pyrrole ring with respect to its two adjacent pyridine units. Titrations of the pyrrole‐containing sequence monitored by 1H NMR spectroscopy confirmed the expected drop in affinity for tartaric acid and malic acid that arises from the conformation change in the backbone that follows the replacement of the pyridazine by a pyrrole. The reduction of the pyridazine to a pyrrole was characterized by cyclic voltammetry both on the entire sequence and on a shorter precursor. The lower cathodic potential of the precursor made its preparative‐scale electroreduction possible. Direct in situ modification of the pyridazine within the entire capsule sequence was achieved chemically by using zinc in acetic acid. 相似文献
996.
Tunable Trimers: Using Temperature and Pressure to Control Luminescent Emission in Gold(I) Pyrazolate‐Based Trimers 下载免费PDF全文
Dr. Christopher H. Woodall Dr. Sara Fuertes Dr. Christine M. Beavers Lauren E. Hatcher Andrew Parlett Dr. Helena J. Shepherd Dr. Jeppe Christensen Dr. Simon J. Teat Mourad Intissar Dr. Alexandre Rodrigue‐Witchel Dr. Yan Suffren Prof. Christian Reber Christopher H. Hendon Dr. Davide Tiana Prof. Aron Walsh Prof. Paul R. Raithby 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(51):16933-16942
A systematic investigation into the relationship between the solid‐state luminescence and the intermolecular Au???Au interactions in a series of pyrazolate‐based gold(I) trimers; tris(μ2‐pyrazolato‐N,N′)‐tri‐gold(I) ( 1 ), tris(μ2‐3,4,5‐ trimethylpyrazolato‐N,N′)‐tri‐gold(I) ( 2 ), tris(μ2‐3‐methyl‐5‐phenylpyrazolato‐N,N′)‐tri‐gold(I) ( 3 ) and tris(μ2‐3,5‐diphenylpyrazolato‐N,N′)‐tri‐gold(I) ( 4 ) has been carried out using variable temperature and high pressure X‐ray crystallography, solid‐state emission spectroscopy, Raman spectroscopy and computational techniques. Single‐crystal X‐ray studies show that there is a significant reduction in the intertrimer Au???Au distances both with decreasing temperature and increasing pressure. In the four complexes, the reduction in temperature from 293 to 100 K is accompanied by a reduction in the shortest intermolecular Au???Au contacts of between 0.04 and 0.08 Å. The solid‐state luminescent emission spectra of 1 and 2 display a red shift with decreasing temperature or increasing pressure. Compound 3 does not emit under ambient conditions but displays increasingly red‐shifted luminescence upon cooling or compression. Compound 4 remains emissionless, consistent with the absence of intermolecular Au???Au interactions. The largest pressure induced shift in emission is observed in 2 with a red shift of approximately 630 cm?1 per GPa between ambient and 3.80 GPa. The shifts in all the complexes can be correlated with changes in Au???Au distance observed by diffraction. 相似文献
997.
DMAP‐BODIPY Alkynes: A Convenient Tool for Labeling Biomolecules for Bimodal PET–Optical Imaging 下载免费PDF全文
Dr. Bertrand Brizet Dr. Victor Goncalves Dr. Claire Bernhard Prof. Pierre D. Harvey Prof. Franck Denat Dr. Christine Goze 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(40):12933-12944
Several new boron dipyrromethene/N,N‐dimethylaminopyridine (BODIPY‐DMAP) assemblies were synthesized as precursors for bimodal imaging probes (optical imaging, OI/positron emission tomography, PET). The photophysical properties of the new compounds were also studied. The first proof‐of‐concept was obtained with the preparation of several new BODIPY‐labeled bombesins and evaluation of the affinity for bombesin receptors by using a competition binding assay. Fluorination reactions were investigated on DMAP‐BODIPY precursors as well as on DMAP‐BODIPY‐labeled bombesins. Chemical modifications on the BODIPY core were also performed to obtain luminescent dyes emitting in the therapeutic window (650–900 nm), suitable for in vivo imaging, making these compounds promising precursors for PET/optical dual‐modality imaging agents. 相似文献
998.
Engineering the Donor Selectivity of D‐Fructose‐6‐Phosphate Aldolase for Biocatalytic Asymmetric Cross‐Aldol Additions of Glycolaldehyde 下载免费PDF全文
Dr. Anna Szekrenyi Anna Soler Dr. Xavier Garrabou Dr. Christine Guérard‐Hélaine Dr. Teodor Parella Dr. Jesús Joglar Prof. Dr. Marielle Lemaire Dr. Jordi Bujons Prof. Dr. Pere Clapés 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(39):12572-12583
D ‐Fructose‐6‐phosphate aldolase (FSA) is a unique catalyst for asymmetric cross‐aldol additions of glycolaldehyde. A combination of a structure‐guided approach of saturation mutagenesis, site‐directed mutagenesis, and computational modeling was applied to construct a set of FSA variants that improved the catalytic efficiency towards glycolaldehyde dimerization up to 1800‐fold. A combination of mutations in positions L107, A129, and A165 provided a toolbox of FSA variants that expand the synthetic possibilities towards the preparation of aldose‐like carbohydrate compounds. The new FSA variants were applied as highly efficient catalysts for cross‐aldol additions of glycolaldehyde to N‐carbobenzyloxyaminoaldehydes to furnish between 80–98 % aldol adduct under optimized reaction conditions. Donor competition experiments showed high selectivity for glycolaldehyde relative to dihydroxyacetone or hydroxyacetone. These results demonstrate the exceptional malleability of the active site in FSA, which can be remodeled to accept a wide spectrum of donor and acceptor substrates with high efficiency and selectivity. 相似文献
999.
Dr. J. Alberto Rodríguez‐Velamazán Dr. Oscar Fabelo Dr. Christine M. Beavers Dr. Eva Natividad Dr. Marco Evangelisti Dr. Olivier Roubeau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(26):7956-7961
FeII(Metz)6](FeIIIBr4)2 (Metz=1‐methyltetrazole) is one of the rare systems combining spin‐crossover and long‐range magnetic ordering. A joint neutron and X‐ray diffraction and magnetometry study allows determining its collinear antiferromagnetic structure, and shows an increase of the Néel temperature from 2.4 K at ambient pressure, to 3.9 K at 0.95 GPa. Applied pressure also enables a full high‐spin to low‐spin switch at ambient temperature. 相似文献
1000.
Michael?E.?RybakEmail author Ching-I?Pao Christine?M.?Pfeiffer 《Analytical and bioanalytical chemistry》2014,406(3):771-784
We have developed and validated a high-performance liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for determining urine caffeine and 14 caffeine metabolites suitable for estimating caffeine exposure and metabolic phenotyping in population studies. Sample preparation consisted solely of a series of simple reagent treatments at room temperature. Stable isotope-labeled analogs were used as internal standards for all analytes. We developed rapid LC-MS/MS separations for both positive and negative ion mode electrospray ionizations to maximize measurement sensitivity. Limits of detection were 0.05–0.1 μmol/L depending on the analytes. Method imprecision, based on total coefficients of variation, was generally <7 % when analyte concentration was >1 μmol/L. Analyte recoveries were typically within 10 % of being quantitative (100 %), and good agreement was observed among analytes measured across different MS/MS transitions. We applied this method to the analysis of a convenience set of human urine samples (n?=?115) and were able to detect a majority of the analytes in ≥99 % of samples as well as calculate caffeine metabolite phenotyping ratios for cytochrome P450 1A2 and N-acetyltransferase 2. Whereas existing LC-MS/MS methods are limited in number of caffeine metabolites for which they are validated, or are designed for studies in which purposely elevated caffeine levels are expected, our method is the first of its kind designed specifically for the rapid, sensitive, accurate, and precise measurement of urine caffeine and caffeine metabolites at concentrations relevant to population studies. 相似文献