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51.
Kathleen E. Berg Jaclyn A. Adkins Sarah E. Boyle Charles S. Henry 《Electroanalysis》2016,28(4):679-684
Mn concentrations were determined using square‐wave cathodic stripping voltammetry (CSV) with inexpensive, stencil‐printed carbon ink electrodes generated on polypropylene transparency films. Using an optimized pH 5 ammonium acetate buffer and addition of 1,4‐benzoquinone, a detection limit as low as 500 nM (30 ppb) was achieved. Addition of 1,4‐benzoquinone improved peak potential reproducibility and height, while addition of 3.5 % w/w sodium chloride to the background solution approximately doubled the sensitivity (μA/ppm). Tolerance tests with interfering metals were conducted and the method was found to be resilient to chromium(VI), iron(III), magnesium(II), nickel(II), and zinc(II), but susceptible to aluminum(III), copper(II), iron(II), and lead(II) at concentration ratios at or below one. This technique was successfully used to measure Mn levels in yerba mate and green tea samples as an example application. 相似文献
52.
Jha SC Lorch M Lewis RA Archibald SJ Boyle RW 《Organic & biomolecular chemistry》2007,5(12):1970-1974
A calix[4]phyrin-(1,1,1,1) substituted with a 4-isothiocyanatophenyl group has been synthesised and used to attach the macrocycle to a solid support. The NCS group can also be used to further functionalise the calix[4]phyrin-(1,1,1,1) by reaction with amines and amino acids. Stability constants for anion binding by the calix[4]phyrin-(1,1,1,1) are reported and these show a clear ability to differentiate F(-) and HSO(4)(-) from Cl(-), Br(-), I(-) which can be detected by both NMR and UV-visible spectroscopy. 相似文献
53.
Boyle TJ Sewell RM Ottley LA Pratt HD Quintana CJ Bunge SD 《Inorganic chemistry》2007,46(5):1825-1835
The reaction of [Ti(mu-ONep)(ONep)3]2 (ONep = OCH2C(CH3)3) with a series of heterocyclic methanol derivatives [tetrahydrofurfuryl alcohol (H-OTHF), thiophene methanol (H-OTPM), or 2-pyridylcarbinol (H-OPy)-collectively termed H-OR*], led to the isolation of a novel family of OR*-substituted titanium alkoxide precursors. Independent of the initial stoichiometry for the H-OTHF reaction, a monosubstituted, dinuclear species was isolated as [(ONep)3Ti(muc-OTHF)]2 (1). For 1, each Ti was octahedrally (Oh) bound by three terminal ONep ligands, one bidentate bridging OTHF ligand (muc-OTHF), and an oxygen from the other muc-OTHF ligand. For the OTPM derivatives, the product was identified as [(ONep)3Ti(mu-OTPM)]2 (2). For this ligand, the soft S atom does not bind to the Ti but the O atom does act as a bridge between the two trigonal bipyramidal bound Ti metal centers. The OPy system yielded (OPy)2Ti(OR)2 independent of the OR and the stoichiometry used [OR = ONep (3), OCHMe2 (4), OCMe3 (5)]. For 3-5, the two OPy ligands chelate to the Oh-bound Ti metal center with two terminal OR ligands. Compounds 1-5 were fully characterized using a variety of analytical techniques. An initial investigation of the proposed chemical stability of the '(OPy)2Ti' moiety of 3-5 to alcoholysis exchange pathways involving (i) alkyl alcohols, (ii) aryl alcohols, (iii) substituted phenols, (iv) H-OR* derivatives, and (v) silanols proved successful through the isolation of a novel family of structurally characterized (OPy)2Ti(OR')2 (7-24) compounds. 相似文献
54.
Opium samples from four different locations and poppy straw from different plant varieties have been assayed using micellar capillary electrophoresis incorporating a sweeping technique. Individual alkaloids (morphine, codeine, papaverine, noscapine, thebaine, oripavine, reticuline and narceine) were quantitatively determined in the different samples by a validated capillary electrophoresis method. Unsupervised pattern recognition of the opium samples and the poppy straw samples using hierarchical cluster analysis (HCA) and principal component analysis (PCA), showed distinct clusters. Supervised pattern recognition using soft independent modelling of class analogy (SIMCA) was performed to show individual groupings and allow unknown samples to be classified according to the models built using the CZE assay results. 相似文献
55.
Let φ be a one-dimensional surjective cellular automaton map. We prove that if φ is a closing map, then the configurations which are both spatially and temporally periodic are dense. (If φ is not a closing map, then we do not know whether the temporally periodic configurations must be dense.) The results are special cases of results for shifts of finite type, and the proofs use symbolic dynamical techniques. 相似文献
56.
57.
Geert A. Daudey Mengjie Shen Ankush Singhal Patrick van der Est G. J. Agur Sevink Aimee L. Boyle Alexander Kros 《Chemical science》2021,12(41):13782
Biological membrane fusion is a highly specific and coordinated process as a multitude of vesicular fusion events proceed simultaneously in a complex environment with minimal off-target delivery. In this study, we develop a liposomal fusion model system with specific recognition using lipidated derivatives of a set of four de novo designed heterodimeric coiled coil (CC) peptide pairs. Content mixing was only obtained between liposomes functionalized with complementary peptides, demonstrating both fusogenic activity of CC peptides and the specificity of this model system. The diverse peptide fusogens revealed important relationships between the fusogenic efficacy and the peptide characteristics. The fusion efficiency increased from 20% to 70% as affinity between complementary peptides decreased, (from KF ≈ 108 to 104 M−1), and fusion efficiency also increased due to more pronounced asymmetric role-playing of membrane interacting ‘K’ peptides and homodimer-forming ‘E’ peptides. Furthermore, a new and highly fusogenic CC pair (E3/P1K) was discovered, providing an orthogonal peptide triad with the fusogenic CC pairs P2E/P2K and P3E/P3K. This E3/P1k pair was revealed, via molecular dynamics simulations, to have a shifted heptad repeat that can accommodate mismatched asparagine residues. These results will have broad implications not only for the fundamental understanding of CC design and how asparagine residues can be accommodated within the hydrophobic core, but also for drug delivery systems by revealing the necessary interplay of efficient peptide fusogens and enabling the targeted delivery of different carrier vesicles at various peptide-functionalized locations.We developed a liposomal fusion model system with specific recognition using a set of heterodimeric coiled coil peptide pairs. This study unravels important structure–fusogenic efficacy relationships of peptide fusogens. 相似文献
58.
Ahmed El‐Shafei David Hinks Paul D. Boyle Harold S. Freeman 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(8):o569-o571
The title compounds, C18H22Cl2N2O2 and C20H28N2O2, respectively, are isomorphous. The molecules lie at general positions in the unit cell. In each structure, chemically equivalent but crystallographically inequivalent amine N atoms exhibit different degrees of pyramidalization. The structures exhibit weak N—H⋯N hydrogen bonding, which is influenced by the differences in hybridization around the amine N atoms. The torsion angles across the biphenyl linkage for the two compounds are 67.2 (2) and 68.3 (3)°. 相似文献
59.
Bassan P Sachdeva A Kohler A Hughes C Henderson A Boyle J Shanks JH Brown M Clarke NW Gardner P 《The Analyst》2012,137(6):1370-1377
Transmission and transflection infrared microscopy of biological cells and tissue suffer from significant baseline distortions due to scattering effects, predominantly resonant Mie scattering (RMieS). This scattering can also distort peak shapes and apparent peak positions making interpretation difficult and often unreliable. A correction algorithm, the resonant Mie scattering extended multiplicative signal correction (RMieS-EMSC), has been developed that can be used to remove these distortions. The correction algorithm has two key user defined parameters that influence the accuracy of the correction. The first is the number of iterations used to obtain the best outcome. The second is the choice of the initial reference spectrum required for the fitting procedure. The choice of these parameters influences computational time. This is not a major concern when correcting individual spectra or small data sets of a few hundred spectra but becomes much more significant when correcting spectra from infrared images obtained using large focal plane array detectors which may contain tens of thousands of spectra. In this paper we show that, classification of images from tissue can be achieved easily with a few (<10) iterations but a reliable interpretation of the biochemical differences between classes could require more iterations. Regarding the choice of reference spectrum, it is apparent that the more similar it is to the pure absorption spectrum of the sample, the fewer iterations required to obtain an accurate corrected spectrum. Importantly however, we show that using three different non-ideal reference spectra, the same unique correction solution can be obtained. 相似文献
60.
Thomas JA Boyle MP Hunter LW Tiffany JE 《Journal of colloid and interface science》2012,370(1):176-182
Pervaporation membranes were produced comprising a 4:1 sodium-alginate:poly(vinyl-alcohol) polymer blend selective layer with a plasticizing agent (glycerol). Membranes were supported on a poly(acrylonitrile) mesoporous support layer and non-woven fabric base. Pervaporation separation of ethanol/water mixtures was carefully followed as a function of film thickness and time. It was found, contrary to what might be expected from literature, that these films showed increased selectivity and decreased flux as film thickness was reduced. It is argued that the morphology and structure of the polymer blend changes with thickness and that these structural changes define the efficiency of the separation in these conditions. 相似文献