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21.
Ywu-Jang Fu Shin-Shing Shyu Fu-Hu Su Pih-Chen Yu 《Colloids and surfaces. B, Biointerfaces》2002,25(4)
The water-soluble anti-cancer drug, 5-fluorouracil (5-fluoro-2,4-pyrimidinedione) (5-FU) is encapsulated into biodegradable co-poly (
-lactic/glycolic acid) (PLGA) using the spray drying method for the development of long-lasting controlled release systems. In this study, the effects of both polymeric composition and technological parameters on release profiles of 5-FU were investigated. The degradation of various microspheres was also investigated. The mixture of dichloromethane/chloroform/methanol (1:1:2 v/v) instead of dichloromethane/chloroform (1:1 v/v) resulted in the modification of morphology, while the physical structure of the microsphere varied from a porous PLGA microsphere to a dense PLGA microsphere. The results show that the average diameter was 2 μm and the anti-cancer drug loading of microspheres approached approximately 8% (w/w). In addition, the lactide/glycolide ratio of the polymer is an important parameter for controlling the release profile of the entrapped anticancer drug. Our results indicate that the mixture solvent using the spray drying method was more efficient than emulsification solvent diffusion. 相似文献
22.
Wei‐Lin Su Hsiu‐Ping Huang Wei‐Ting Chen Wen‐Yi Hsu Hsi‐Yen Chang Szu‐Yu Ho Shao‐Pin Wang Shin‐Guang Shyu 《中国化学会会志》2011,58(2):163-173
Carbonyls' 2π orbital populations, [2π], in W(CO)5L {L = PPh3, PPh2Me, PPhMe2} have been determined by NMR spin‐lattice relaxation techniques. Experimental values of axial [2π], compared with those reported for PMe3 and P(OMe)3, reveal that PMe3 is a slightly better π‐acid than PPh3. Through space interactions between carbonyl and phenyl groups are insignificant since values of [2π] do not vary significantly in the series of phosphines, going from PMep3 to PPh3. Natural bond orbital (NBO) studies indicate that π‐accepting capabilities for these phosphines are primarily governed by the nature of P‐C anti‐bonding, σ*P‐C. Compared with PPh3, the better π‐accepting σ*P‐C, as well as the better s‐donating lone‐pair LP(P), in PMe3 can both be explained by the higher extents of rehybridization of the coordinated phosphorus atom. Based on this rehybridization argument, the NBO predicted order of increasing π‐acidic strengths PPh3 < PPh2Me < PPhMe2 < PMe3, which cannot be clearly distinguished by NMR experiments, is ascribed to the same NBO trend of σ‐donating capabilities in a synergistic manner. Effects of coordination on P‐Y (Y = C, O, F) bonding strengths in phosphines (or phosphites) are depending on two conflicting effects: rehybridization of LP(P) and the hyperconjugative‐like dπ → σ*P‐Y back‐donation. 相似文献
23.
24.
2,4′-Bipyridines 4a, 4c, 4d and 3,4′-bipyridines 4b, 4e, 4f, 4g, 4h are obtained in modest yield by the addition of organocuprate reagents derived from bromopyridines 2a-h to N-ethoxycarbonylpyridinium chloride 1 followed by air oxidation. 相似文献
25.
Simultaneous determination of sweeteners and preservatives in preserved fruits by micellar electrokinetic capillary chromatography 总被引:1,自引:0,他引:1
A micellar electrokinetic capillary method for the simultaneous determination of the sweeteners dulcin, aspartame, saccharin, and acesulfame-K and the preservatives sorbic acid; benzoic acid; sodium dehydroacetate; and methyl-, ethyl-, propyl-, isopropyl-, butyl-, and isobutyl-p-hydroxybenzoate in preserved fruits is developed. These additives are ion-paired and extracted using sonication followed by solid-phase extraction from the sample. Separation is achieved using a 57-cm fused-silica capillary with a buffer comprised of 0.05 M sodium deoxycholate, 0.02 M borate-phosphate buffer (pH 8.6), and 5% acetonitrile, and the wavelength for detection is 214 nm. The average recovery rate for all sweeteners and preservatives is approximately 90% with good reproducibility, and the detection limits range from 10 to 25 microg/g. Fifty preserved fruit samples are analyzed for the content of sweeteners and preservatives. The sweeteners found in 28 samples was aspartame (0.17-11.59 g/kg) or saccharin (0.09-5.64 g/kg). Benzoic acid (0.02-1.72 g/kg) and sorbic acid (0.27-1.15 g/kg) were found as preservatives in 29 samples. 相似文献
26.
The reaction mechanism of methanol conversion to hydrocarbons on HZSM-5 zeolite was studied. From the selectivity plots of products in an integral fixed-bed flow reactor, paraffins were classified as primary and secondary stable products, light olefins as primary unstable products, aromatics as primary and secondary unstable or stable products. The results of the 14C-labelled methanol reaction indicated that the C1–C5 surface intermediates generated by dimethyl ether / methanol equilibrium gave paraffins and olefins at 300°C. The concentration of intermediates and adsorbed methanol on ZSM-5 decreased with increasing temperature. The distribution of radioactivity showed that propylene played an important role in the autocatalysis of the reaction. 相似文献
27.
Der‐Shyu Lin 《中国化学会会志》2004,51(6):1279-1286
This research focuses on the UV‐Vis. absorbance spectra of the hybrid organic/inorganic complementary electro‐chromic device (ECD), comprising polyaniline‐poly(styrenesulfonic acid)[PANI‐PSSA] complexes and tungsten oxide (WO3) thin film coupled in combination with a polymer electrolyte poly(2‐acrylamido‐2‐methyl‐propane‐sulphonic acid)[PAMPSA]. PANI‐PSSA microstructure surface images have been studied by AFM. By applying a potential of ?3.0 V across the two external ITO contacts, we are able to modulate the light absorption also in the UV‐Vis region (200–900 nm) wavelength region. For example, the absorption changes from 1.20 to 0.6 at 720 nm. 相似文献
28.
In this paper we prove the following result. Let m1 ≥ m2 ≥ … ≥ m1 be nonnegative integers. A necessary and sufficient condition for the complete graph Kn to be decomposed into stars Sm1, Sm2, …, Sm1 is . © 1996 John Wiley & Sons, Inc. 相似文献
29.
C. P. Chang Y. H. Chen F. L. Shyu R. B. Chen M. F. Lin 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):509-522
The uniaxial-stress effects on the low-energy electronic properties of nanographite ribbons are studied by the tight-binding model. The dependence on the strain, the edge structure, the ribbon width, and the stacking sequence is strong. The strain could induce the alternation of energy dispersions, the destruction of state degeneracy, the variation of energy gap, the semiconductor–metal transition, and the change of special structures in density of states. The effects of strain are important for the AB- and AA-stacked armchair ribbons. However, they are negligible for the AB- and AA-stacked zigzag ribbons. Armchair ribbons could exhibit the semiconductor–metal transition. Such transition is mainly determined by the strain and the ribbon–ribbon interactions. 相似文献
30.
José Jiun-Shian Wu Wei-Pang Chang Hsi-Chien Shih Chen-Tung Yen Bai Chuang Shyu 《BMC neuroscience》2014,15(1):1-17