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排序方式: 共有65条查询结果,搜索用时 15 毫秒
1.
A polarization fluoroimmunoassay for cotinine, a major metabolite of nicotine, has been adapted for fully automated screening of urine samples on the Abbott TDx analyser. The method has sensitivity and specificity suitable for the discrimination of active smokers from non-smokers (including passive smokers) by application of a cut-off at 0.5 mg l-1 of total urinary cotinine. Most active smokers' urine gave results over 1 mg l-1, whereas apparent levels in non-smokers were 0.08 mg l-1 or lower. A result for one sample can be obtained in about 5 min and a throughput of 80 samples h-1 can be maintained for large-scale screening applications. 相似文献
2.
Prasain JK Patel R Kirk M Wilson L Botting N Darley-Usmar VM Barnes S 《Journal of mass spectrometry : JMS》2003,38(7):764-771
Electrospray ionization combined with tandem mass spectrometry was applied to a study of some representative chlorinated and nitrated isoflavones-potential metabolites of isoflavones in inflammatory cells. Upon collision-induced dissociation of deprotonated [M - H](-) ions of these compounds, a number of structurally characteristic product ions were produced. The product ion analysis of 3'- and 8-chlorodaidzein in the tandom mass spectra led to ready differentiation of these isomers. 3-Nitro derivatives of both genistein and daidzein have product ions due to the losses of HNO(2) and two OH groups. Chlorinated derivatives of isoflavones were detected in cell-based experiments and their structures were proposed by comparing the tandem mass spectra of their product ions with those of standards. This work provides a suitable analytical basis to aid the characterization of chlorinated and nitrated metabolites in studies in vivo and in vitro. 相似文献
3.
Miriam Gochin Landon R. Whitby Aaron H. Phillips Dale L. Boger 《Journal of computer-aided molecular design》2013,27(7):569-582
Due to the inherently flexible nature of a protein–protein interaction surface, it is difficult both to inhibit the association with a small molecule, and to predict how it might bind to the surface. In this study, we have examined small molecules that mediate the interaction between a WWI motif on the C-helix of HIV-1 glycoprotein-41 (gp41) and a deep hydrophobic pocket contained in the interior N-helical trimer. Association between these two components of gp41 leads to virus–cell and cell–cell fusion, which could be abrogated in the presence of an inhibitor that binds tightly in the pocket. We have studied a comprehensive combinatorial library of α-helical peptidomimetics, and found that compounds with strongly hydrophobic side chains had the highest affinity. Computational docking studies produced multiple possible binding modes due to the flexibility of both the binding site and the peptidomimetic compounds. We applied a transferred paramagnetic relaxation enhancement experiment to two selected members of the library, and showed that addition of a few experimental constraints enabled definitive identification of unique binding poses. Computational docking results were extremely sensitive to side chain conformations, and slight variations could preclude observation of the experimentally validated poses. Different receptor structures were required for docking simulations to sample the correct pose for the two compounds. The study demonstrated the sensitivity of predicted poses to receptor structure and indicated the importance of experimental verification when docking to a malleable protein–protein interaction surface. 相似文献
4.
5.
Macrocyclic Gd3+ Complexes with Pendant Crown Ethers Designed for Binding Zwitterionic Neurotransmitters 下载免费PDF全文
Dr. Fatima Oukhatar Hervé Meudal Dr. Céline Landon Prof. Dr. Nikos K. Logothetis Prof. Dr. Carlos Platas‐Iglesias Priv.‐Doz. Dr. Goran Angelovski Dr. Éva Tóth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11226-11237
A series of Gd3+ complexes exhibiting a relaxometric response to zwitterionic amino acid neurotransmitters was synthesized. The design concept involves ditopic interactions 1) between a positively charged and coordinatively unsaturated Gd3+ chelate and the carboxylate group of the neurotransmitters and 2) between an azacrown ether appended to the chelate and the amino group of the neurotransmitters. The chelates differ in the nature and length of the linker connecting the cyclen‐type macrocycle that binds the Ln3+ ion and the crown ether. The complexes are monohydrated, but they exhibit high proton relaxivities (up to 7.7 mM ?1 s?1 at 60 MHz, 310 K) due to slow molecular tumbling. The formation of ternary complexes with neurotransmitters was monitored by 1H relaxometric titrations of the Gd3+ complexes and by luminescence measurements on the Eu3+ and Tb3+ analogues at pH 7.4. The remarkable relaxivity decrease (≈80 %) observed on neurotransmitter binding is related to the decrease in the hydration number, as evidenced by luminescence lifetime measurements on the Eu3+ complexes. These complexes show affinity for amino acid neurotransmitters in the millimolar range, which can be suited to imaging concentrations of synaptically released neurotransmitters. They display good selectivity over non‐amino acid neurotransmitters (acetylcholine, serotonin, and noradrenaline) and hydrogenphosphate, but selectivity over hydrogencarbonate was not achieved. 相似文献
6.
Landon M. Kanner 《International Journal of Non》2007,42(2):204-215
This paper is concerned with investigation of the effects of strain-stiffening on the classical limit point instability that is well-known to occur in the inflation of internally pressurized rubber-like spherical thin shells (balloons) and circular cylindrical thin tubes composed of incompressible isotropic non-linearly elastic materials. For a variety of specific strain-energy densities that give rise to strain-stiffening in the stress-stretch response, the inflation pressure versus stretch relations are given explicitly and the non-monotonic character of the inflation curves is examined. While such results are known for constitutive models that exhibit a gradual stiffening (e.g. exponential and power-law models), our primary focus is on materials that undergo severe strain-stiffening in the stress-stretch response. In particular, we consider two phenomenological constitutive models that reflect limiting chain extensibility at the molecular level. It is shown that for materials with sufficiently low extensibility no limit point instability occurs and so stable inflation is then predicted for such materials. Potential applications of the results to the biomechanics of soft tissues are indicated. 相似文献
7.
The gas-phase thermolysis of the guanidinato aluminum amide precursor [Me2NC(NiPr)2]Al(NMe2)2 (1) in the oven temperature range of ambient temperatures to 600 °C has been investigated with matrix-isolation FTIR spectroscopy and time-of-flight mass spectrometry (argon as carrier gas). Precursor 1 fragments above 300 °C to form iPrCNCiPr (2) and monomeric Al(NMe2)3 (3m). Independent thermolysis series with 2 and the aluminum amide dimer 3d, [Al(NMe2)3]2, were conducted and been used to interpret the results of the fragmentation of precursor 1. Compound 3m was present in the thermolysis range of 350–450 °C and has been identified for the first time. Through a comparison of measured FTIR spectra with the calculated spectrum of 3m (D3 point group symmetry; B3LYP/6-31G(d) level of theory) all expected IR bands were found and could be assigned to normal modes. At thermolysis temperatures of ?500 °C signals indicative for H2CNCH3 (4) were found, showing that 3m fragments further at higher temperature. The thermolysis product 2 (iPrCNCiPr) withstands the higher thermolysis temperatures. From our study one can conclude that precursor 1 cleanly delivers the monomeric aluminum alane 3m, which then acts as the reactive material forming species. 相似文献
8.
Isotopologous Organotellurium Probes Reveal Dynamic Hypoxia In Vivo with Cellular Resolution 下载免费PDF全文
Dr. Landon J. Edgar Dr. Ravi N. Vellanki Dr. Trevor D. McKee Dr. David Hedley Prof. Bradly G. Wouters Prof. Mark Nitz 《Angewandte Chemie (International ed. in English)》2016,55(42):13159-13163
Changes in the oxygenation state of microenvironments within solid tumors are associated with the development of aggressive cancer phenotypes. Factors that influence cellular hypoxia have been characterized; however, methods for measuring the dynamics of oxygenation at a cellular level in vivo have been elusive. We report a series of tellurium‐containing isotopologous probes for cellular hypoxia compatible with mass cytometry (MC)—technology that allows for highly parametric interrogation of single cells based on atomic mass spectrometry. Sequential labeling with the isotopologous probes (SLIP) in pancreatic tumor xenograft models revealed changes in cellular oxygenation over time which correlated with the distance from vasculature, the proliferation of cell populations, and proximity to necrosis. SLIP allows for capture of spatial and temporal dynamics in vivo using enzyme activated probes. 相似文献
9.
Arnold L. Rheingold William C. Fultz Thomas B. Brill Shayne J. Landon 《Journal of chemical crystallography》1983,13(5):317-323
The X-ray structure determination of (η 5-C5H5)Co(HNC6H4NH) (Ib) reveals that the compound crystallizes in the monoclinic space groupP21/n witha=12.479(3),b=8.865(2),c=17.817(5) Å, {iβ}=94.70(2)°,V=1964.4(6) Å3,Z=8 (two independent molecules form the asymmetric unit). Least-squares refinement based on 1894 independent observed reflections,I≥2.5σ(I), resulted in a finalR value of 0.054. A pattern of somewhat shortened Co-N bonds (〈av〉 1.83 Å), short C-N bonds (〈av〉 1.34 Å), Co-N-C bond angles consistent with trigonally hybridized N, and a nearly planar metallocyclic ring suggest that some electron delocalization may exist in the ring. This pattern, however, may also be explicable in terms of factors other than delocalization; alternatives are discussed. The structure may best be regarded as a CoI complex containing ano-quinonediimine ligand. 相似文献
10.
A. A. Lamola D. O. Landon I. E. Kochevar L. C. Harber 《Photochemistry and photobiology》1982,35(2):285-290
Abstract— An instrument designed for convenient determination of action spectra for cutaneous photo-responses in man and experimental animals is described. Light from 450 W Xe lamp is dispersed by a concave holographic grating. The spectrum from 244 to 616 nm is projected as a planar strip (2 times 17 cm) intercepted by a grid with 31 ports. The bandwidth at each port is 12 nm and the size of the port increases from about 4 × 4 mm to 6 × 8 mm from the low to high wavelength limits, respectively. Typical fluence rates in quanta m-2 s-1 are 4.0 times 1019 at 298 nm, 16 times 1019 at 394nm and 22 times 1019 at 538 nm. Responses due to delayed erythema in normal skin and to musk ambrette photoallergy and solar urticaria in patients skin have been elicited with this instrument. 相似文献