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51.
Z. Vivian Feng Ian L. Gunsolus Tian A. Qiu Katie R. Hurley Lyle H. Nyberg Hilena Frew Kyle P. Johnson Ariane M. Vartanian Lisa M. Jacob Samuel E. Lohse Marco D. Torelli Robert J. Hamers Catherine J. Murphy Christy L. Haynes 《Chemical science》2015,6(9):5186-5196
Although nanomaterials facilitate significant technological advancement in our society, their potential impacts on the environment are yet to be fully understood. In this study, two environmentally relevant bacteria, Shewanella oneidensis and Bacillus subtilis, have been used as model organisms to elucidate the molecular interactions between these bacterial classes and Au nanoparticles (AuNPs) with well-controlled and well-characterized surface chemistries: anionic 3-mercaptopropionic acid (MPA), cationic 3-mercaptopropylamine (MPNH2), and the cationic polyelectrolyte poly(allylamine hydrochloride) (PAH). The data demonstrate that cationic, especially polyelectrolyte-wrapped AuNPs, were more toxic to both the Gram-negative and Gram-positive bacteria. The levels of toxicity observed were closely related to the percentage of cells with AuNPs associated with the cell surface as measured in situ using flow cytometry. The NP concentration-dependent binding profiles were drastically different for the two bacteria strains, suggesting the critical role of bacterial cell surface chemistry in determining nanoparticle association, and thereby, biological impact. 相似文献
52.
Katie M. Lewis Jennifer Kelley LeRoy PetersonJr. Mark D. Smith Rachel C. Severance Shae A. Vaughn Hans-Conrad zur Loye 《Journal of chemical crystallography》2010,40(10):867-871
Abstract
A new iodobismuthate of formula [BiI2(terpy)2][BiI4(terpy)] (terpy = 2,2′:6′,2′′-terpyridine), was prepared solvothermally in an ethanolic mixture composed of bismuth (III) iodide, terpy, and ruthenium (III) iodide. The compound crystallizes in the space group P [`1] \bar{1} , with Z = 2, a = 9.8491(4) ?, b = 15.4181(7) ?, c = 17.5323(8) ?, α = 89.8140(10)°, β = 80.4160(10)°, γ = 77.9020(10)°. Single-crystal X-ray analysis reveals that the compound is composed of a [BiI2(terpy)2]+ cation and a [BiI4(terpy)]− anion. It is an uncommon example where an iodobismuthate cation and anion are simultaneously incorporated into the same crystal structure. 相似文献53.
Harry J. Sterling Michael P. Daly Geoffrey K. Feld Katie L. Thoren Alexander F. Kintzer Bryan A. Krantz Evan R. Williams 《Journal of the American Society for Mass Spectrometry》2010,21(10):1762-1774
The effects of two supercharging reagents, m-nitrobenzyl alcohol (m-NBA) and sulfolane, on the charge-state distributions and conformations of myoglobin ions formed by electrospray ionization
were investigated. Addition of 0.4% m-NBA to aqueous ammonium acetate solutions of myoglobin results in an increase in the maximum charge state from 9+ to 19+,
and an increase in the average charge state from 7.9+ to 11.7+, compared with solutions without m-NBA. The extent of supercharging with sulfolane on a per mole basis is lower than that with m-NBA, but comparable charging was obtained at higher concentration. Arrival time distributions obtained from traveling wave
ion mobility spectrometry show that the higher charge state ions that are formed with these supercharging reagents are significantly
more unfolded than lower charge state ions. Results from circular dichroism spectroscopy show that sulfolane can act as chemical
denaturant, destabilizing myoglobin by ∼1.5 kcal/mol/M at 25 °C. Because these supercharging reagents have low vapor pressures,
aqueous droplets are preferentially enriched in these reagents as evaporation occurs. Less evaporative cooling will occur
after the droplets are substantially enriched in the low volatility supercharging reagent, and the droplet temperature should
be higher compared with when these reagents are not present. Protein unfolding induced by chemical and/or thermal denaturation
in the electrospray droplet appears to be the primary origin of the enhanced charging observed for noncovalent protein complexes
formed from aqueous solutions that contain these supercharging reagents, although other factors almost certainly influence
the extent of charging as well. 相似文献
54.
Bunyakul N Edwards KA Promptmas C Baeumner AJ 《Analytical and bioanalytical chemistry》2009,393(1):177-186
Fluorescence and electrochemical microfluidic biosensors were developed for the detection of cholera toxin subunit B (CTB)
as a model analyte. The microfluidic devices were made from polydimethylsiloxane (PDMS) using soft lithography from silicon
templates. The polymer channels were sealed with a glass plate and packaged in a polymethylmethacrylate housing that provided
leakproof sealing and a connection to a syringe pump. In the electrochemical format, an interdigitated ultramicroelectrode
array (IDUA) was patterned onto the glass slide using photolithography, gold evaporation and lift-off processes. For CTB recognition,
CTB-specific antibodies were immobilized onto superparamagnetic beads and ganglioside GM1 was incorporated into liposomes. The fluorescence dye sulforhodamine B (SRB) and the electroactive compounds potassium hexacyanoferrate
(II)/hexacyanoferrate (III) were used as detection markers that were encapsulated inside the liposomes for the fluorescence
and electrochemical detection formats, respectively. Initial optimization experiments were carried out by applying the superparamagnetic
beads in microtiter plate assays and SRB liposomes before they were transferred to the microfluidic systems. The limits of
detection (LoD) of both assay formats for CTB were found to be 6.6 and 1.0 ng mL−1 for the fluorescence and electrochemical formats, respectively. Changing the detection system was very easy, requiring only
the synthesis of different marker-encapsulating liposomes, as well as the exchange of the detection unit. It was found that,
in addition to a lower LoD, the electrochemical format assay showed advantages over the fluorescence format in terms of flexibility
and reliability of signal recording. 相似文献
55.
56.
Malatesti N Hudson R Smith K Savoie H Rix K Welham K Boyle RW 《Photochemistry and photobiology》2006,82(3):746-749
Two boron complexes of 5-phenyldipyrromethenes bearing isothiocyanate groups on the phenyl ring have been synthesized for the first time. The utility of these new fluorescence probes for labeling biologically relevant proteins is demonstrated on two monoclonal antibodies that bind to antigens overexpressed on cancer cells. Spectral comparison of the two structures reveals significant photophysical differences, including bathochromically shifted excitation and emission bands, increased molar absorptivity and a large increase in fluorescence quantum yield of approximately 10 times. Differences in photophysical parameters are linked to hindered rotation of the phenyl ring in one of the probes. 相似文献
57.
58.
A concise total synthesis of 7-demethylpiericidin A1 has been completed. The synthesis features a titanium(II)-mediated cyclization of a (silyloxy)enyne as the key step and proceeds in nine steps from tiglic aldehyde. 相似文献
59.
Baber RA Clarke ML Heslop KM Marr AC Orpen AG Pringle PG Ward A Zambrano-Williams DE 《Dalton transactions (Cambridge, England : 2003)》2005,(6):1079-1085
The cage phosphines 1,3,5,7-tetramethyl-6-phenyl-2,4,8-trioxa-6-phosphaadamantane (1a) and 1,3,5,7-tetraethyl-6-phenyl-2,4,8,trioxa-6-phosphaadamantane (1b) have been made by the acid catalysed addition of PhPH(2) to the appropriate beta-diketones; the acid used (HCl, H(3)PO(4) or H(2)SO(4)) and its concentration affect the rate and selectivity of these condensation reactions. Phosphines 1a and 1b react with [PdCl(2)(NCPh)(2)] to form complexes trans-[PdCl(2)(1a)(2)](2a) and trans-[PdCl(2)(1b)(2)](2b) as mixtures of rac and meso diastereoisomers. The platinum(II) chemistry is more complicated and when 1a or 1b is added to [PtCl(2)(cod)], equilibrium mixtures of trans-[PtCl(2)L(2)] and [Pt(2)Cl(4)L(2)](L = or ) are formed in CH(2)Cl(2) solution. Meso/rac mixtures of trans-[MCl(CO)(1a)(2)] M = Ir (6a) or Rh (7a) are formed upon treatment of MCl(3).nH(2)O with an excess of 1a and the anionic cobalt complex [NHEt(3)][CoCl(3)(1a)](9) was isolated from the product formed by CoCl(2).6H(2)O and 1a. The nu(CO) values from the IR spectra of 6a and 7a suggest that 1a resembles a phosphonite in its bonding to Rh and Ir. Crystal structures of meso-2a, meso-2b, rac-6a and 9 are reported and in each case a small intracage C-P-C angle of ca. 94 degrees is observed; this may partly explain the bonding characteristics of ligands 1a and 1b. The cone angles for 1a and 1b are similar and large (ca. 200 degrees). Rhodium complexes of ligands 1a and 1b are hydroformylation catalysts with similarly high activity to catalysts derived from phosphites. The catalysts derived from 1a and 1b gave unusually low linear selectivity in the hydroformylation of hexenes. This feature has been further exploited in quaternary-selective hydroformylations of unsaturated esters; catalysts derived from 1a give better yields and regioselectivities than any previously reported catalyst. 相似文献
60.
Basra S De Vries JG Hyett DJ Harrison G Heslop KM Orpen AG Pringle PG Von Der Luehe K 《Dalton transactions (Cambridge, England : 2003)》2004,(12):1901-1905
The unsymmetrical, optically active ligands 1,2-C(6)H(4)(PPh(2))((R,R)-2,5-dimethylphospholanyl) and the new 1,1'-Fe(C(5)H(4))(2)(PPh(2))((R,R)-2,5-dimethylphospholanyl) form complexes of the type [PtCl(2)(diphos)] and [Rh(diphos)(diene)][BF(4)]. The crystal structure of reveals that only one quadrant is blocked. Asymmetric hydrogenation of acrylic esters and enamides using and as catalysts show that the phenylene-backboned diphosphine gives a more efficient catalyst in terms of asymmetric induction than the more flexible ferrocene-backboned diphosphine. The best results, which were obtained with and enamide substrates, exceeded those obtained with Duphos catalysts. The rate of hydrogenation of the enamides with was 10 times faster than with [Rh(Duphos)(diene)][BF(4)]. A quadrant diagram can be used to predict the configuration of the major product, provided it is assumed to be derived from the less sterically congested intermediate. 相似文献