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1.
Fibric acid derivatives are used to treat hyperlipidemia and have wide ranging effects on lipid metabolism. The action of
these compounds on cholesterol esterification, catalyzed by acyl-coenzyme A:cholesterol acyltransferase (ACAT), has been quite
widely studied, but their effect on cholesteryl ester hydrolysis and the enzyme neutral cholesteryl ester hydrolase (nCEH)
has been largely ignored. Male rats were therefore fed for 10 d on a standard chow diet supplemented with either clofibrate
or bezafibrate, to study their effects on plasma lipid levels and hepatic cholesterol metabolism. Plasma triacyglycerols were
not significantly altered by these diets, but bezafibrate significantly lowered plasma cholesterol levels (29.7%,P<0.01). When expressed per unit weight of DNA, both fibrates reduced the hepatic content of triacylglycerol, cholesterol and
cholesteryl esters (40, 18.7, 16.5 and 66.7, 28.6, 34.2% for clofibrate and bezafibrate, respectively). ACAT activity was
significantly reduced by both drugs, but clofibrate (65% inhibition) was more effective than bezafibrate (35% inhibition).
The most dramatic effect of the diets was a marked increase in the activity of both the microsomal and the cytosolic nCEH.
When expressed on a whole liver basis, the effect of bezafibrate on the cytosolic enzyme (13.6-fold increase in activity)
was much greater than that of clofibrate (4.8-fold increase). Increases in the activity of a cytosolic protein that inhibits
the activity of nCEH were also noted, but these changes were relatively small. The results suggest that the activation of
nCEH, in combination with the inhibition in ACAT activity, contributes to a decrease in the cholesteryl ester content of the
liver which may influence the secretion of very low density lipoprotein. 相似文献
2.
The influence of dietary simvastatin, cholestyramine, and the combination of simvastatin plus cholestyramine on hepatic cholesterol
metabolism has been investigated in male rats. Recovery from the effects of the drugs was also investigated by refeeding normal
chow for 24 h. Both drugs, alone and in combination, increased 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activityin vitro, but activity returned toward control values, after drug withdrawal. Acyl-CoA:cholesterol acyltransferase (ACAT) was significantly
reduced (P<0.001) by simvastatin (−75%), cholestyramine (−71%), and by the drug combination (−81%), due both to a decrease in microsomal
cholesterol and to nonsubstrate-dependent modulation of enzyme activity. Refeeding control diet increased ACAT activity but
not to control levels. The enhanced activity arose partly from higher microsomal cholesterol and partly from increases in
total enzyme activity. Cytosolic neutral cholesteryl ester hydrolase (CEH) activity was substantially elevated by simvastatin
(3-fold) and by the drug combination (6-fold), whereas the effect of cholestyramine was smaller (1.5-fold). Normal chow for
24 h only partially returned cytosolic CEH activity to control values. Microsomal CEH activity was increased by simvastatin,
alone and in combination with cholestyramine (1.4 to 1.7-fold), and was also enhanced, in the cholestyramine-treated animals,
following drug withdrawal. Removal of simvastatin did not allow recovery of this enzyme activity, while withdrawal of the
drug combination led to values 29% below controls. The results indicate that in the rat, simvastatin and cholestyramine alter
both ACAT and CEH activity, as well as inhibiting HMG-CoA reductase activity. 相似文献
3.
A cytosolic protein, that is inhibitory to neutral cholesteryl ester hydrolase, has been investigated in the livers of female
rats using microsomes isolated from the mammary gland of lactating rats as an enzyme source. To facilitate comparisons, inhibitory
activity is expressed in terms of the amount (μg) of cytosolic protein required to reduce esterase activity by 50% and is
compared to the hepatic content of both cholesterol and cholesteryl esters. The experiments revealed a sexual difference in
the level of inhibitory activity, with the livers of both suckling and mature male animals containing less of the material
than the corresponding females. Alterations in the physiological status of the females, such as pregnancy and lactation, led
to a decrease in the activity of the protein. This was reversed by blocking lactation with a combination of an antiserum to
rat growth hormone and the anti-prolactin drug, bromcoriptine, but not by premature weaning of the animals. Food withdrawal
for 24 hr also had the effect of increasing inhibitory activity. In general the cholesteryl ester content of the livers correlated
with the level of inhibitory activity. Thus the activity of the cytosolic inhibitor of neutral cholesteryl ester hydrolase
responded to changes in both the hormonal and the nutritional status of the female animal. It is suggested that the presence
of the greater cholesteryl ester hydrolase inhibitory activity in the female liver may help to explain the lower risk of coronary
heart disease in premenopausal females by facilitating increased hepatic storage of the sterol in the form of the ester. 相似文献
4.
Efficacy of tertiary butylhydroquinone on the storage and heat stability of liquid canola shortening 总被引:1,自引:0,他引:1
Z. J. Hawrysh P. J. Shand C. Lin B. Tokarska R. T. Hardin 《Journal of the American Oil Chemists' Society》1990,67(9):585-590
The sensory (odor and flavor) and physicochemical characteristics of tertiary butylhydroquinone (TBHQ) treated and butylated
hydroxyanisole/toluene (BHA/BHT) treated liquid canola shortenings, subjected to accelerated storage (Schaal oven test at
65°C) and deep fat heating (at 185°C), were determined. Data for the Schaal oven test indicate that TBHQ was effective in
retarding oxidative rancidity in liquid canola shortenings. However, addition of the commonly used mixture of BHA/BHT to canola
shortenings resulted in only a slight decrease in oxidation during schaal oven storage. The results obtained from deep fat
heating of canola liquid shortening show that neither TBHQ nor BHA/BHT was effective in enhancing oxidative and thermal stability
of this product. 相似文献
5.
There is an accumulation of the glycolytic enzyme enolase and of cholesteryl esters in macrophages that have been converted
into “foam” cells. In this study, we questioned whether enolase could be involved in this accumulation of cholesteryl esters
by inhibiting the activity of neutral cholesteryl ester hydrolases. Enolase from both yeast and rabbit muscle were incubated
with three different cholesteryl ester hydrolases and were shown to inhibit the hydrolysis of cholesteryl esters. Inhibition
was dependent on the concentration of enolase and appeared to occur through binding of the enolase to the cholesteryl ester.
Nevertheless, the yeast and rabbit muscle enolases differed in their efficiency of inhibition and in their mechanism of action.
Purification of commercial enolase preparations by gel-filtration yielded single proteins with the same inhibitory activities
as the originals, indicating that the inhibition was not due to the presence of an impurity. Partially purified αα-and γγ-isoforms
of the enzyme from rat brain also appear to have inhibitory effects on cholesteryl ester hydrolysis. Negative control of the
hydrolytic phase of the cholesterol/cholesteryl ester cycle may be a secondary function of enolases which correlates with
the accumulation of cholesteryl esters in a number of neuro-degenerative and demyelinating diseases. 相似文献
6.
7.
Textural, Water Holding, and Sensory Properties of Low-fat Pork Bologna with Normal or Waxy Starch Hull-less Barley 总被引:1,自引:0,他引:1
P.J. Shand 《Journal of food science》2000,65(1):101-107
All ultra-low-fat (< 1%) pork bolognas had similar cook yield and composition. Addition of 4% hull-less waxy barley flour or meal to formulations provided the greatest purge control; 4% normal starch barley, wheat flour and potato starch were intermediate; 0.25% kappa-carrageenan or 1% soy protein concentrate had little effect on water holding and texture. Expressible moisture and purge were significantly correlated to moisture content and batter viscosity. Formulations with wheat flour and waxy barley meal were scored the firmest, while bologna with potato starch required the most force to compress. For most sensory properties, barley fractions performed similarly to wheat flour; however, waxy barley provided superior water holding during storage. 相似文献
8.
Zbigniew Pietrasik Jagvinder S. Dhanda Phyllis J. Shand Ronald B. Pegg 《Journal of food science》2006,71(2):S110-S118
The combined effects of injection, packaging (modified atmosphere packaging [MAP] with 70% O2/ 30% CO2 and vacuum packaging [VP]), storage temperature (‐1 °C and +4 °C), and storage time on the color, microbial and oxidative stability of beef and bison longissimus lumborum (LL) steaks were investigated. Beef LL steaks in MAP retained their bright red color longer than bison steaks. Bison steaks developed higher 2‐Thiobarbituric acid reactive substances (TBARS) during storage, and this might have influenced the resulting rapid loss of redness from the bloomed meat. Storage at ‐1 °C in MAP provided greater color stability and a longer storage life for both meat species studied. Injection of salt/phosphate had a beneficial effect on the color stability of steaks during retail display; however, this positive effect was more pronounced for bison steaks compared with those of beef. Steaks stored overnight under MAP before retail display maintained the highest a* values for up to 5 d compared with those stored under vacuum. MAP‐OV steaks generally maintained the highest OMB content for up to 5 d during retail display compared with those stored under vacuum. Nevertheless, OMB levels were significantly (P < 0.05) lower in bison steaks compared with those of beef irrespective of packaging treatments. Injected steaks and those stored at ‐1 °C had significantly (P < 0.05) higher OMB levels compared with non‐injected counterparts and those stored at +4 °C, respectively. MAP is an excellent option for short‐term storage due to its positive effects on meat color, but for longer storage, VP may be necessary. Storing meat under vacuum and then placing it under MAP just before retail display might be another option to increase shelf life. 相似文献
9.
W. A. Shand 《Journal of Materials Science》1968,3(4):344-348
The application of X-ray-stimulated luminescence to the detection of trivalent rare earth impurities in ionic materials is discussed. Characteristic luminescent wavelengths allow the identification of individual rare earths. The lower limit of impurity detectable in the particular case of the fluorides is found to be about 0.01 ppm if no positive identification of the rare earth ion is required. This is increased to 1 ppm when positive identification of the specific impurity is required. The application of the technique to the assessment of single crystals and the appropriate starting material is discussed. 相似文献
10.
Experimental evidence on the rare-earth doping of the IIVI compounds and a knowledge of the rare-earth chalcogenide structures is used to suggest a set of principles with which to predict the ultimate doping limit for the binary and ternary chalcogenides. The validity of these rules is tested by experiment. 相似文献