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41.
Oxidative Conversion of a Europium(II)‐Based T1 Agent into a Europium(III)‐Based paraCEST Agent that can be Detected In Vivo by Magnetic Resonance Imaging 下载免费PDF全文
Dr. Alexander M. Funk Dr. Veronica Clavijo Jordan Prof. A. Dean Sherry Dr. S. James Ratnakar Prof. Zoltan Kovacs 《Angewandte Chemie (International ed. in English)》2016,55(16):5024-5027
The EuII complex of 1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetraacetic acid (DOTA) tetra(glycinate) has a higher reduction potential than most EuII chelates reported to date. The reduced EuII form acts as an efficient water proton T1 relaxation reagent, while the EuIII form acts as a water‐based chemical exchange saturation transfer (CEST) agent. The complex has extremely fast water exchange rate. Oxidation to the corresponding EuIII complex yields a well‐defined signal from the paraCEST agent. The time course of oxidation was studied in vitro and in vivo by T1‐weighted and CEST imaging. 相似文献
42.
Lagerlund O Odell LR Mowbray SL Nilsson MT Krajewski WW Nordqvist A Karlén A Larhed M 《Combinatorial chemistry & high throughput screening》2007,10(9):783-789
A microwave-enhanced, palladium-catalyzed protocol for the alpha-arylation of a protected glycine in neat water is described. This reaction proceeds rapidly, under non-inert conditions, to afford a range of phenylglycine derivatives in moderate to good yields. Based on this alpha-arylation, a number of aryl L-methionine-SR-sulfoximine (MSO) analogues were prepared and evaluated for their Mycobacterium tuberculosis glutamine synthetase (TB-GS) inhibitory activity. 相似文献
43.
44.
Anne P. Vonderheide Brian Boyd Anna Ryberg Ecevit Yilmaz Thomas E. Hieber Peter E. Kauffman Sherry T. Garris Jeffrey N. Morgan 《Journal of chromatography. A》2009,1216(22):4633-4640
Determination of an individual's aggregate dietary ingestion of pesticides entails analysis of a difficult sample matrix. Permethrin-specific molecularly imprinted polymer (MIP) solid-phase extraction cartridges were developed for use as a sample preparation technique for a composite food matrix. Vortexing with acetonitrile and centrifugation were found to provide optimal extraction of the permethrin isomers from the composite foods. The acetonitrile (with 1% acetic acid) was mostly evaporated and the analytes reconstituted in 90:10 water/acetonitrile in preparation for molecularly imprinted solid-phase extraction. Permethrin elution was accomplished with acetonitrile and sample extracts were analyzed by isotope dilution gas chromatography–ion trap mass spectrometry. Quantitation of product ions provided definitive identification of the pesticide isomers. The final method parameters were tested with fortified composite food samples of varying fat content (1%, 5%, and 10%) and recoveries ranged from 99.3% to 126%. Vegetable samples with incurred pesticide levels were also analyzed with the given method and recoveries were acceptable (81.0–95.7%). Method detection limits were demonstrated in the low ppb range. Finally, the applicability of the MIP stationary phase to extract other pyrethroids, specifically cyfluthrin and cypermethrin, was also investigated. 相似文献
45.
Giovannia A. Pereira Laura Ball A. Dean Sherry Joop A. Peters Carlos F. G. C. Geraldes 《Helvetica chimica acta》2009,92(11):2532-2551
The three‐dimensional structures in aqueous solution of the entire series of the Ln3+ complexes [Ln(DOTP*‐Et)]? (formed from the free ligand P,P′,P″,P′′′‐[1,4,7,10‐tetraazacyclododecane‐1,4,7,10‐tetrayltetrakis(methylene)]tetrakis[P‐ethylphosphinic acid] (H4DOTP*‐Et) were studied by NMR techniques to rationalize the parameters governing the relaxivity of the Gd3+ complex and evaluate its potential as MRI contrast agent. From the 1H‐ and 31P‐NMR lanthanide‐induced‐shift (LIS) values, especially of the [Yb(DOTP*‐Et)]? complex, it was concluded that the [Ln(DOTP*‐Et)]? complexes adopt in solution twisted square antiprismatic coordination geometries which change gradually their coordination‐cage structure along the lanthanide series. These complexes have no inner‐sphere‐H2O coordination, and preferentially have the (R,R,R,R) configuration of the P‐atoms in the pendant arms. Self‐association was observed in aqueous solution for the tetraazatetrakisphosphonic acid ester complexes [Ln(DOTP*‐OEt)]? (=[Ln(DOTP‐Et)]?) and [Ln(DOTP*‐OBu)]? (=[Ln(DOTP‐Bu)]?) at and above 5 mM concentration, through analysis of 31P‐NMR, EPR, vapor‐pressure‐osmometry, and luminescence‐spectroscopic data. The presence of the cationic detergent cetylpyridinium chloride (CPC; but not of neutral surfactants) shifts the isomer equilibrium of [Eu(DOTP*‐OBu)]? to the (S,S,S,S) form which selectively binds to the cationic micelle surface. 相似文献
46.
Heather B Bradshaw Neta Rimmerman Sherry Shu-Jung Hu Valery M Benton Jordyn M Stuart Kim Masuda Benjamin F Cravatt David K O'Dell J Michael Walker 《BMC biochemistry》2009,10(1):14-11
Background
N-arachidonoyl glycine (NAGly) is an endogenous signaling lipid with a wide variety of biological activity whose biosynthesis is poorly understood. Two primary biosynthetic pathways have been proposed. One suggests that NAGly is formed via an enzymatically regulated conjugation of arachidonic acid (AA) and glycine. The other suggests that NAGly is an oxidative metabolite of the endogenous cannabinoid, anandamide (AEA), through an alcohol dehydrogenase. Here using both in vitro and in vivo assays measuring metabolites with LC/MS/MS we test the hypothesis that both pathways are present in mammalian cells. 相似文献47.
Biosynthesis of sulfated glycopeptide antibiotics by using the sulfotransferase StaL 总被引:2,自引:0,他引:2
The unique glycopeptide antibiotic A47934, produced by Streptomyces toyocaensis, possesses a nonglycosylated heptapeptide core that is sulfated on the phenolic hydroxyl of the N-terminal 4-hydroxy-L-phenylglycine residue. Genetic and biochemical experiments confirmed that StaL is a sulfotransferase capable of sulfating the predicted crosslinked heptapeptide substrate to produce A47934 both in vivo and in vitro. Incubation of purified His(6)-StaL with various substrates in vitro revealed substrate specificity and yielded two sulfo-glycopeptide antibiotics: sulfo-teicoplanin aglycone and sulfo-teicoplanin. Quantification of the antibacterial activity of desulfo-A47934, A47934, teicoplanin, and sulfo-teicoplanin demonstrated that sulfation slightly increased the minimum inhibitory concentration. This unique modification by sulfation expands glycopeptide diversity with potential application for the development of new antibiotics. 相似文献
48.
Woods M Woessner DE Zhao P Pasha A Yang MY Huang CH Vasalitiy O Morrow JR Sherry AD 《Journal of the American Chemical Society》2006,128(31):10155-10162
Paramagnetic lanthanide(III) complexes that contain hyperfine-shifted exchangeable protons offer considerable advantages over diamagnetic molecules as chemical exchange saturation transfer (CEST) agents for MRI. As part of a program to investigate avenues to improve the sensitivity of such agents, the CEST characteristics of europium(III) macrocyclic complexes having appended hydroxyethyl groups were investigated. The CEST spectrum of the asymmetrical complex, EuCNPHC3+, shows five distinct peaks for each magnetically nonequivalent exchangeable proton in the molecule. The CEST spectra of this complex were fitted to NMR Bloch theory to yield exchange rates between each of six exchanging proton pools (five on the agent plus bulk water). Exchange between the Eu3+-bound hydroxyl protons and bulk water protons was slow in dry acetonitrile but accelerated incrementally upon stepwise addition of water. In pure water, exchange was too fast to observe a CEST effect. The utility of this class of europium(III) complex for CEST imaging applications is ultimately limited by the small chemical shifts induced by the hydroxyl-appended ligands of this type and the resulting small Deltaomega values for the exchangeable hydroxyl protons. 相似文献
49.
Zhao SY 《The Journal of the Acoustical Society of America》2010,128(4):2009-2020
This study concentrates on one of the commonly occurring phonetic variations in English: the stop-like modification of the dental fricative /e/. The variant exhibits a drastic change from the canonical /e/; the manner of articulation is changed from one that is fricative to one that is stop-like. Furthermore, the place of articulation of stop-like /e/ has been a point of uncertainty, leading to confusion between stop-like /e/ and /d/. In this study, acoustic and spectral moment measures were taken from 100 stop-like /e/ and 102 /d/ tokens produced by 59 male and 23 female speakers in the TIMIT corpus. Data analysis indicated that stop-like /e/ is significantly different from /d/ in burst amplitude, burst spectrum shape, burst peak frequency, second formant at following-vowel onset, and spectral moments. Moreover, the acoustic differences from /d/ are consistent with those expected for a dental stop-like /e/. Automatic classification experiments involving these acoustic measures suggested that they are salient in distinguishing stop-like /e/ from /d/. 相似文献
50.
Giuseppe A. Rosi Michael Sherry Matthias Kinzel David E. Rival 《Experiments in fluids》2014,55(5):1-10
We investigate the dynamics of a small number of droplets (N = 1, 2, 3) in microfluidic Hele–Shaw cells. We study the cases N = 1, 2, and 3 droplets and analyze the influence of the side walls. In the course of the study, we observe spontaneous alignment of droplet pairs, pair exchanges, droplet escape, multiple reflections between walls, i.e., a number of phenomena that have not been reported yet. As a whole, using pairwise far-field dipolar interactions between droplets, along with treating the walls as mirrors, allows to reproduce the observations, even though limitations in the predictability of the model are pointed out in a few cases. From a more practical prospective, the work shows that the behavior of elementary droplet assemblies can be put under acceptable experimental control in a wide variety of situations, a feature potentially interesting for self-assembly, mixing, or transport of particles in microfluidic environments. 相似文献