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排序方式: 共有875条查询结果,搜索用时 15 毫秒
81.
Kimmo Nurmi Vladimir Ossipov Erkki Haukioja Kalevi Pihlaja 《Journal of chemical ecology》1996,22(11):2023-2040
We studied seasonal and between-tree variation in the composition and content of total and individual low-molecular-weight phenolics (LMWP) in leaves of mountain birch trees (Betula pubescens ssp.tortuosa). The major phenolic compounds were chlorogenic acid, quercetin-3-O--D-glucuronopyranoside, myricetin-3-O-(5-acetyl)-L-rhamnopyranoside, and 1-O-galloyl--D-(2-O-acetyl)-glucopyranose. The content of total phenolics, as well as the sum of individual LMWP, varied only slightly among trees while variation in contents of individual LMWP was large. Concentrations of almost all phenolics decreased during the growing season but pairwise correlations between individual phenolics remained similar over the whole season indicating tree-specific LMWP profiles over the season. Among flavonoids, the between-tree component of variation was 2.6 times as large as the seasonal component, while for variation of nonflavonoids the between-tree component was larger than the seasonal one. To explain the significant correlations within both flavonoid and nonflavonoid compounds, we discuss the biogenesis of LMWP in birch leaves, as well as their ecological role. 相似文献
82.
83.
The response surface methodology was used to evaluate the effects of extraction time, power of ultrasound, liquid to solid ratio, and solvent composition on the quantity and quality (from aspect of antioxidant activity) phenolics of Stachys lavandulifolia. The best extraction time, power of ultrasound, liquid to solid ratio, and solvent composition for both the quality and quantity of phenolics were 14 min, 300 W, 40 (v/w), and 57% methanol, respectively. Only the liquid to solid ratio was effective on the quality of phenolics. Also, the comparison between the ultrasound-assisted extraction and maceration methods showed the suitability of ultrasound-assisted extraction for extracting phenolics from this plant. 相似文献
84.
Wine phenolics—analysis of low molecular weight components by high performance liquid chromatography
Marie-Hlne Salagoïty-Auguste Alain Bertrand 《Journal of the science of food and agriculture》1984,35(11):1241-1247
Low molecular weight phenolic compounds were separated by high performance liquid chromatography on hydrocarbon-bonded reverse phase packings, with a water-methanol elution gradient. Phenolic compounds were extracted from wine with ethyl acetate. A first extraction at pH 7 enabled isolation of neutral molecules (catechins, procyanidins, flavonols, aromatic alcohols); a second extraction at pH 2 was performed to extract phenolic acids. Successive injections of these two extracts in the chromatograph gave the distribution of the different phenolic compounds in the wine under analysis. Analytical data are given for low molecular weight phenolic compounds present in young red Bordeaux wines from different vine cultivars. 相似文献
85.
KATHARINE M. WALL VALERIE M. TAIT KENNETH C. EASTWELL CAROL A. REID THOMAS H.J. BEVERIDGE 《Journal of food science》1996,61(1):92-96
Haze production in aerobically or anaerobically produced Red Delicious apple juice was assessed following heating, aeration, and protein addition. Stored aerobic juice produced haze in 6 wk, but anaerobic juice was haze-free unless oxygen was introduced. Phenolic material was incorporated into haze in both systems. HPLC (detection at 420 nm) of concentrated juice and addition of 100 mg/L BSA suggested the presence in both juices of ‘reactive’ material which could complex and precipitate during storage. Phenolic compounds, heating, and especially oxidation during processing (and storage) appear to be major determinants of ‘haze potential’ in clarified apple juice. 相似文献
86.
The conventional sonicator/shaker bath method for phenolic extraction was compared with a less traditional one using a homogenizer. The homogenizer proved to be both more efficient and consistent in extracting phenolics from tender, as well as tough, leaves. We propose that adoption of the homogenizer technique will increase phenolic yield and efficiency. 相似文献
87.
Danny E Akin Luanne L Rigsby Wayne W Hanna Roger N Gates 《Journal of the science of food and agriculture》1991,56(4):523-538
The tissues in leaf blades, midribs, sheaths and stems of normal (N), 5848, and two brown midrib (bmr) mutants, 5753 and 5778, of pearl millet (Pennisetum glaucum (L) R Br) were examined for structural characteristics related to digestibility. The anatomies of the various plant parts were not substantially different between N and bmr plants. The more rigid, lignified tissues such as vascular bundles in all plant parts and the rind of stems were not digested after incubation for 7 days in N or bmr plants, indicating that modifications in these tissues were not sufficient to affect biodegradation. Modifications in the digestible tissues resulted in faster and more extensive degradation in bmr plants, and these changes appear to be the most significant in relation to biodegradation. The parenchyma of midveins and stems, which occupies c 70 and 60% of the cross-sectional area of these respective parts, were the sites where modification in phenolics resulted in the greatest improvement in digestibility. 相似文献
88.
Helen N. Asemota Max A. Wellington Adewale A. Odutuga Mohammed H. Ahmad 《Journal of the science of food and agriculture》1992,60(3):309-312
The effect of short-term storage on the protein, phosphorus and phenolic content as well as peroxidase and o-diphenolase activities of cut, harvested Jamaican yam (Dioscorea sp) tubers (D rotundata. D alata and D cayenensis) was studied. There was an initial increase in the total phenolic content up to the third week of storage followed by a gradual decrease to the sixth week. Phenolic content was found to be highest in D cayenensis followed by D rotundata and D alata. The activities of peroxidase (EC 1. 11. 1. 7) and o-diphenolase (EC 1. 10.3.1) increased steadily up to the third week of storage and thereafter decreased to the fifth week. The intensity and rapidity of browning in tubers when cut, correlated very closely with the tuber o-diphenolase and phenolic content levels while the onset of rotting correlated with the peroxidase activity levels in the species studied. 相似文献
89.
D. K. Pandey 《Journal of chemical ecology》1994,20(12):3111-3122
Parthenium (Parthenium hysterophorus L.) leaf residue (LP, leaf powder) inhibited salvinia (Salvinia molesta Mitchell) biomass and the number of healthy fronds at 0.25% (w/v) and killed the treated plants at and above 0.75% (w/v) in about 5–15 days, depending on the quantity of the residue. At the lethal dose, the LP caused an abrupt desiccation of above-water plant parts, probably due mainly to root dysfunction. This was concurrent with the loss of dehydrogenase activity in, and an increase in solute leakage from, the roots and loss of chlorophylla, b, and total chlorophyll contents in the fronds, resulting in death of the treated plants. The LP appears inhibitory to salvinia through affecting macromolecules—proteins, lipids, and nucleic acids. The inhibitory activity of LP at the lethal dose suspended in water was completely lost when allowed to stand for 30 days under outdoor conditions and promoted growth of the salvinia plants placed in it. The standard allelochemicals, including those present in parthenium LP, except parthenin andp-hydroxybenzoic acid, did not inhibit growth up to 100 ppm. However, parthenin andp-hydroxybenzoic acid killed salvinia plants at 100 and 50 ppm, respectively. Sincep-hydroxybenzoic acid is unlikely to be present at such a high concentration, parthenin appears to be one of the main allelochemicals responsible for the inhibitory effect of parthenium leaf residue on salvinia.A portion of this work was presented at the International Symposium on Weed Management for Sustainable Agriculture held at C.C.S. Haryana Agricultural University, Hissar, India, November 18–20, 1993. 相似文献
90.
Evaluation of Antioxidant Compounds and Total Sugar Content in a Nectarine [Prunus persica (L.) Batsch] Progeny 总被引:1,自引:0,他引:1
Abidi W Jiménez S Moreno MÁ Gogorcena Y 《International journal of molecular sciences》2011,12(10):6919-6935
Epidemiological studies suggest that consumption of fruit rich in phenolic compounds is associated with health-protective effects due to their antioxidant properties. For these reasons quality evaluation has become an important issue in fruit industry and in breeding programs. Phytochemical traits such as total phenolics, flavonoids, anthocyanins, L-ascorbic acid, sugar content and relative antioxidant capacity (RAC) were analyzed over four years in flesh fruit of an F1 population "Venus" × "Big Top" nectarines. Other traits such as harvesting date, yield, fruit weight, firmness, soluble solids concentration (SSC), pH, titratable acidity (TA) and ripening index (RI) were also determined in the progeny. Results showed high variability among genotypes for all analyzed traits. Total phenolics and flavonoids showed significant positive correlations with RAC implying that both are important antioxidant bioactive compounds in peaches. We found genotypes with enhanced antioxidant capacity and a better performance than progenitors, and in consequence the best marketability. 相似文献