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排序方式: 共有124条查询结果,搜索用时 15 毫秒
1.
Microencapsulation of DNA Within alginate microspheres and crosslinked chitosan membranes for in vivo application 总被引:4,自引:0,他引:4
T. Alexakis D. K. Boadi D. Quong A. Groboillot I. O’Neill D. Poncelet R. J. Neufeld 《Applied biochemistry and biotechnology》1995,50(1):93-106
Calf thymus DNA was microencapsulated within crosslinked chitosan membranes, or immobilized within chitosan-coated alginate
microspheres. Microcapsules were prepared by interfacial polymerization of chitosan, and alginate microspheres formed by emulsification/
internal gelation. Diameters ranged from 20 to 500 Μm, depending on the formulation conditions. Encapsulated DNA was quantifiedin situ by direct spectrophotometry (260 nm) and ethidium bromide fluorimetry, and compared to DNA measurements on the fractions
following disruption and dissolution of the microspheres. Approximately 84% of the DNA was released upon core dissolution
and membrane disruption, with 12% membrane bound. The yield of encapsulation was 96%. Leakage of DNA from intact microspheres/capsules
was not observed. DNA microcapsules and microspheres were recovered intact from rat feces following gavage and gastrointestinal
transit. Higher recoveries (60%) and reduced shrinkage during transit were obtained with the alginate microspheres. DNA was
recovered and purified from the microcapsules and microspheres by chromatography and differential precipitation with ethanol.
This is the first report of microcapsules or microspheres containing biologically active material (DNA) being passed through
the gastrointestinal tract, with the potential for substantial recovery. 相似文献
2.
Alexopoulos T Allen C Anderson EW Areti H Banerjee S Beery PD Biswas NN Bujak A Carmony DD Carter T Cole P Choi Y De Bonte RJ Erwin AR Findeisen C Goshaw AT Gutay LJ Hirsch AS Hojvat C Kenney VP Lindsey CS LoSecco JM McMahon T McManus AP Morgan N Nelson KS Oh SH Piekarz J Porile NT Reeves D Scharenberg RP Stampke SR Stringfellow BC Thompson MA Turkot F Walker WD Wang CH Wesson DK 《Physical review letters》1990,64(9):991-994
3.
Lazarus EA Navratil GA Greenfield CM Strait EJ Austin ME Burrell KH Casper TA Baker DR DeBoo JC Doyle EJ Durst R Ferron JR Forest CB Gohil P Groebner RJ Heidbrink WW Hong R Houlberg WA Howald AW Hsieh C Hyatt AW Jackson GL Kim J Lao LL Lasnier CJ Leonard AW Lohr J La Haye RJ Maingi R Miller RL Murakami M Osborne TH Perkins LJ Petty CC Rettig CL Rhodes TL Rice BW Sabbagh SA Schissel DP Scoville JT Snider RT Staebler GM Stallard BW Stambaugh RD St John HE Stockdale RE Taylor PL Thomas DM 《Physical review letters》1996,77(13):2714-2717
4.
We investigate electromagnetic effects in the framework of chiral perturbation theory. Using a completely independent method, we confirm Urech’s results for the divergences of the one-loop functional in the electromagnetic sector. We perform a one-loop analysis of allP t2 (P=π, K, η) and theK t3 form factors $f_ + ^{K^ + \pi ^o } (0),f_ + ^{K^o \pi ^ - } (0)$ , including a systematic treatment of theO(e 2 p 2) contributions in the mesonic part. We illustrate our results by several numerical estimates. 相似文献
5.
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7.
Alginate beads containing entrapped DNA were produced using both external and internal calcium sources, and coated with chitosan
or poly-l-lysine membranes. The beads were assayed with DNase nuclease to determine formulation conditions offering the highest level
of DNA protection fromnucleic acid hydrolysis, simulating gastrointestinal exposure. A method was developed to extract and
assay intracapsular DNA through a modified agarose electrophoresis system. Both external and internally gelled beads were
permeable to DNase (Mw=31 kDa), indicated by the absence of DNA after nuclease exposure. At low levels of DNase exposure, coated high guluronic
content alginate beads offered a higher level of DNA protection compared with coated beads with low guluronic alginate. No
apparent correlation was found with chitosan membrane molecular weight and degree of deacetylation; however, increasing poly-l-lysine molecular weight appeared to increase DNase exclusion from beads. At elevated levels of DNase exposure, DNA hydrolysis
was evident within all coated beads with the exception of those coated with the highest molecular weight poly-l-lysine (Mw=197.1 kDa), which provided almost total nuclease protection. Optimal combination then for DNA protection from nucleases is
a high guluronic alginate core, coated with high molecular weight poly-l-lysine. 相似文献
8.
Yunyu Yi Ronald Neufeld Selim Kermasha 《Journal of Sol-Gel Science and Technology》2006,38(3):251-259
Entrapment of membrane proteins is a challenging task compared to that involving soluble proteins. Chlorophyllase, a membrane
protein, was successfully entrapped in tetramethoxysilane-derived sol-gel. Pre-gel sol typically consists of an aqueous suspension
of chlorophyllase, precursors including tetramethoxysilane and/or methytrimethoxysilane, and sodium fluoride as catalyst.
To obtain a highly active entrapped enzyme preparation, the effects of various immobilization parameters, including the chemical
compositions of pre-gel sol (water/silane ratio, precursor type and proportions, enzyme loading, sodium fluoride concentration),
and sol-gel process parameters (aging and drying time and approach) have been investigated. Chlorophyllase demonstrated the
highest activity in gel derived from a pre-gel sol with water/silane ratio of 30 and enzyme loading of 0.257 mgprotein/ggel, and showed moderately lower activity in organically modified sol-gel than that in hydrophilic sol-gel. The effects of water/silane
ratio and precursor combinations on the activity of entrapped chlorophyllase were also studied by examining the pore morphology
of gel via nitrogen adsorption-desorption. Longer aging time leads to an entrapped chlorophyllase preparation with higher
activity. Chlorophyllase preparation demonstrated negligible activity after air-drying for 12 h while lyophilized chlorophyllase
preparation demonstrated 8, 4 and 4 times higher activity than air-dried, vacuum-dried and solvent-dried preparations. Chlorophyllase
demonstrated 30% higher activity in the improved sol-gel protocol than that from a non-optimized sol-gel protocol developed
in a previous study. 相似文献
9.
10.
C. H. H. Neufeld C. S. Marvel 《Journal of polymer science. Part A, Polymer chemistry》1967,5(3):537-543
A series of three true polyampholytes with unequivocally alternating acidic and basic groups attached directly to the skeletal backbone of the polymer chain have been prepared. This was accomplished by copolymerizing 3,6-diallyl-2-piperidone with the α,ω-dithiols containing 2-, 4-, and 6-methylene groups. The polymerization was carried out in an emulsion system initiated by 2,2′-azobisisobutyronitrile (AIBN), yielding soluble piperidone-containing polymers with molecular weights in the 20,000–30,000 range. The piperidone rings in the polymers were hydrolyzed by dilute sulfuric acid to yield the desired polyampholytes. Fibers were prepared by wet-spinning formic acid solutions of the polyampholyte into saturated salt solution or by melt-spinning. These fibers were quite elastic. We were unsuccessful in demonstrating that mechanical energy could be attained by the effect of pH on the fibers. Similarly, no pH effect could be elicited in Instron tests. The stress-relaxation curve showed a marked positive force–temperature effect characteristic of rubberlike materials with few crosslinks. In a check of transition temperatures, it was noted that on repeated runs the second-order transition temperature rose markedly, suggesting an irreversible change. Viscometric studies clearly demonstrated polyelectrolyte behavior. X-ray diffraction studies of the polyampholytes showed that maximum crystallinity and orientation occurred in the polymer containing as part of the repeating unit the 1,4-butane dithiol moiety. 相似文献