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1.
The application of MS-MS for the analysis of long-chain carboxylic acids and their esters has proved enormously successful but expensive. It is discussed mainly on basis of results obtained with different instruments with lesser attention to principles of the method, which have been adequately reviewed elsewhere. The use of electrospray ionization (ESI) has greatly increased the sensitivity of the method and has permitted assay of total lipid extracts. The combination of HPLC with electrospray and single quadrupole mass spectrometry, LC-ESI-CID-MS, rivals the triple quadrupole MS-MS application in many instances at considerably lower cost. However, LC-ESI-MS-MS remains the most desirable system at the present time for lipid ester analyses. 相似文献
2.
Comparative study of the molecular species of chloropropanediol diesters and triacylglycerols in milk fat 总被引:1,自引:0,他引:1
In an effort to establish the origin of the fatty acid esters of 3-chloropropanediol, which recently have been isolated in
small amounts from goat milk, we compared the molecular species composition of the chlorohydrin diesters and of goat milk
triacylglycerols. The chloropropanediol diesters were found to be composed of molecular species containing C10−C18 fatty acids and corresponded closely in carbon number to those calculated for the long chain sn-1,2-diacyl-glycerol moieties
of goat milk triacylglycerols. The molecular species of goat milk total triacylglycerols contained C4−C18 fatty acids. It is suggested that triacylglycerols and chloropropanediol diesters are derived from the same pool of long
chain fatty acids. A molecular distillate of bovine milk fat did not contain chloropropanediol diesters, while the available
samples of human milk fat were shown to contain alkyldiacylglycerols as the major components of a neutral lipid fraction corresponding
in polarity to the chloropropanediol diesters. 相似文献
3.
This paper reviews recent examples of the application of combined high temperature gas-liquid chromatography (GLC) and reversed
phase high pressure liquid chromatography (HPLC) with electron impact and chemical ionization mass spectrometry for structural
studies of natural diacyl and triacylglycerols. It was concluded that the combination of reversed phase HPLC with direct liquid
inlet chemical ionization mass spectrometry provides the most complete resolution and most reliable identification of natural
acylglycerols, far exceeding the capabilities of either technique alone. The LC/MS method is suitable for quantitative analysis
following appropriate calibration of the total or fragment ion response. 相似文献
4.
We have prepared Schiff base adducts of the core aldehydes of phosphatidylcholine and aminophospholipids, free amino acids,
and myoglobin. The Schiff bases of the ethanolamine and serine glycerophospholipids were obtained by reacting sn-1-palmitoyl(stearoyl)-2-[9-oxo]nonanoyl-glycerophosphocholine (PC-Ald) with a twofold excess of the aminophospholipid in
chloroform/methanol 2∶1 (vol/vol) for 18 h at room temperature. The Schiff bases of the amino acids and myoglobin were obtained
by reacting the aldehyde with an excess of isoleucine, valine, lysine, methyl ester lysine and myoglobin in aqueous methanol
for 18 h at room temperature. Prior to isolation, the Schiff bases were reduced with sodium cyanoborohydride in methanol for
30 min at 4°C. The reaction products were characterized by normal-phase high-performance liquid chromatography and on-line
mass spectrometry with electrospray ionization. The amino acids and aminophospholipids yielded single adducts. A double adduct
was obtained for myoglobin, which theoretically could have accepted up to 23 PC-Ald groups. The yields of the products ranged
from 12 to 44% for the aminophospholipids and from 15–57% for the amino acids, while the Schiff base of the myoglobin was
estimated at 5% level. The new compounds are used as reference standards for the detection of high molecular weight Schiff
bases in lipid extracts of natural products.
Based on presentation at the AOCS Annual Meeting & Expo in Indianapolis, Indiana, April 28–May 1, 1996. 相似文献
5.
The triglycerides of the fat globules of sheep and goat milk were isolated and separated into short and long chain lengths
by silicic acid column chromatography. The short chain lengths comprised major triglycerides with 34–44 acyl carbon atoms
and accounted for nearly 50% of the total milk fat. The long chain lengths contained major triglycerides with 40–54 acyl carbons.
Stereospecific analyses of the short chain triglyceride fraction showed that of the 20–23 moles per cent of C4−C8 fatty acids present, at least 95% were specifically attached to the glycerol molecule in the position corresponding to carbon
3 ofsn-glycerol. The distribution of the other fatty acids (C10 or greater) did not show such marked specificity for either the 1 or the 2 position. Although individual triglycerides were
not identified, the specific placement of the fatty acids could best the accounted for by assuming a common pool of long chain
1,2-diglycerides which served as precursors of the bulk of both short and long chain triglycerides during milk fat synthesis.
Presented in part at the AOCS Meeting, New York, October 1968. 相似文献
6.
Normal-phase HPLC resolution of sn-1,2(2,3)- and x-1,3-DAG generated by partial Grignard degradation from natural TAG was carried out with both (R)-(−) and (S)-(+)-1-(1-naphthyl)ethylurethane derivatives. The diastereomeric sn-1,2- and sn-2,3-DAG derivatives were resolved using two Supelcosil LC-Si (5 μm, 25 cm × 4.6 mm i.d.) columns in series and an isocratic
elution with 0.37% isopropanol in hexane at a flow rate of 0.7 mL/min. The DAG were detected by UV absorption at 280 nm and
were identified by electrospray ionization MS in the positive ion mode following postcolumn addition of chloroform/methanol/30%
ammonium hydroxide (75∶24.5∶0.5, by vol) at 0.6 mL/min. Application of the method to a stereospecific analysis of the molecular
species of TAG of rat VLDL showed that the TAG composition of VLDL circulating under basal conditions differs markedly from
that of VLDL secreted by the liver during inhibition of serum lipases. The inhibition of serum lipases resulted in a significant
proportional decrease in 16∶0 and PUFA and an increase in 18∶0 and oligoenoic FA in the sn-1-position, whereas the FA compositions in the sn-2- and sn-3-positions were much less affected. 相似文献
7.
Fat-laden mucosal cells were isolated by flotation from fed male rats after digesting scrapings of washed jejunum with collagenase
in bicarbonate buffer. About 50–60 million cells were obtained per preparation, which were 95–100% viable as assessed by Trypan
Blue. The isolated cells were capable of effective incorporation of labeled fatty acids and glucose into triglycerides and
phospholipids, and of labeled leucine and glucosamine into the protein envelope of the released chylomicrons. The secretion
of the labeled protein paralleled the release of the labeled fat, both of which were linear with the concentration of the
albumin in the incubation mixture. About 80% of the total fat of the cell was released as chylomicrons within 30 min when
incubated in the presence of albumin-bicarbonate buffer. Injection of puromycin 24 hr prior to harvesting of cells led to
a complete inhibition of chylomicron release. Addition of puromycin to the incubation medium gave 50–80% inhibition of release.
No inhibition of release of chylomicrons resulted from a treatment with ethionine. The released chylomicrons were separated
from the cells by Millipore filtration.
Presented in part at the AOCS Meeting, Chicago, September 1970. 相似文献
8.
In this study, the effect of temperature on the stereoselectivity of phospholipase D (PLD) toward the two primary hydroxyl
groups of glycerol in the transphosphatidylation reaction of phosphatidylcholine to phosphatidylglycerol (PtdGro) was investigated.
For this purpose, PLD from bacteria (Streptomyces septatus TH-2, S. halstedii subsp. scabies K6, and Actinomadura sp.) and cabbage were tested. At the reaction temperatures employed (0–60°C), the proportions of the two PtdGro diastereomers,
namely, 1,2-dioleoyl-sn-glycero-3-phospho-3′-sn-glycerol (R,R configuration) and 1,2-dioleoyl-sn-glycero-3-phosphol-1′-sn-glycerol (R,S configuration), which were produced with PLD from Streptomyces TH-2 and Actinomadura sp., changed gradually from 50% R,R and 50% R,S at 50–60°C to 70% R,R and 30% R,S at O°C. These alterations suggested that the stereoselectivity of the bacterial PLD toward the two primary hydroxyl groups
of prochiral glycerol was significantly influenced by reaction temperature. PLD from Streptomyces K6 showed relatively little effect of temperature on stereoselectivity, giving 65–69% R,R in the temperature range of 60–10°C examined. The plots of In ([R,R]/[R,S]) vs. 1/T gave good linear fits for these three bacterial PLD. No temperature effect was observed for cabbage PLD, which gave an almost
equimolar mixture of the R,R and R,S diastereomers in the range from 0 to 40°C. The temperature-dependent change in enantiomeric selectivity of the bacterial
PLD promises potentially profitable commercial exploitation. 相似文献
9.
We identified and quantified the hydroperoxides, hydroxides, epoxides, isoprostanes, and core aldehydes of the major phospholipids
as the main components of the oxophospholipids (a total of 5–25 pmol/μmol phosphatidylcholine) in a comparative study of human
atheroma from selected stages of lesion development. The developmental stages examined included fatty streak, fibrous plaque,
necrotic core, and calcified tissue. The lipid analyses were performed by normal-phase HPLC with on-line electrospray MS using
conventional total lipid extracts. There was great variability in the proportions of the various oxidation products and a
lack of a general trend. Specifically, the early oxidation products (hydroperoxides and epoxides) of the glycerophosphocholines
were found at the advanced stages of the plaques in nearly the same relative abundance as the more advanced oxidation products
(core aldehydes and acids). The anticipated linear accumulation of the more stable oxidation products with progressive development
of the atherosclerotic plaque was not apparent. It is therefore suggested that lipid infiltration and/or local peroxidation
is a continuous process characterized by the formation and destruction of both early and advanced products of lipid oxidation
at all times. The process of lipid deposition appears to have been subject to both enzymatic and chemical modification of
the normal tissue lipids. Clearly, the appearance of new and disproportionate old lipid species excludes randomness in any
accumulation of oxidized LDL lipids in atheroma. 相似文献
10.
A sensitive and accurate method for detection and quantitation of deuterated fatty acids in the presence of large amounts
of unlabeled fatty acids is described using mass fragmentography in combination with the preparation of tertiarybutyldimethylsilyl
esters (t-BDMS). The method has been applied to determination of deuterated stearic, oleic, elaidic and linoleic acids in human plasma
lipoproteins following duodenal perfusion with a micellar mixture of acids. Over a concentration range of 10–1000 ng/ml, the
average coefficient of variation for the linoleate was 3% and for the oleate (elaidate) ester was 2%. 相似文献