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1.
烤烟氨基酸含量变化规律研究   总被引:17,自引:1,他引:16  
研究不同生育时期、品种、施肥量、叶位以及烘烤前后烟叶氨基酸含量的变化规律。结果表明,旺长期的氨基酸含量较高,进入成熟期后含量急剧下降。烟叶烘烤后,除胱氨酸、蛋氨酸和赖氨酸的含量降低外,其余14种氨基酸及氨的含量均升高。其中,升幅最大的为脯氨酸,烤后与烤前之比为4.50;相反,降幅最大的是蛋氨酸,烤后与烤前之比为0.34。上二棚叶的氨基酸含量高于或接近腰叶。不同耐肥品种间差异较大的氨基酸是脯氨酸和天门冬氨酸,并且以耐肥性强的品种高于耐肥性弱的品种。氨基酸含量与施肥量呈正相关,增幅较大的为谷氨酸、天门冬氨酸和脯氨酸。烤烟叶片氨基酸、天门冬氨酸和脯氨酸。烤烟叶片氨基酸含量变异较大的是脯氨酸、谷氨酸和天门冬氨酸,可作为烟株氮素营养状况与品种耐肥性的生理指标。  相似文献
2.
大理烟区土壤肥力现状与演变趋势   总被引:15,自引:0,他引:15  
在大理州典型的连片烟田作了调查访问,并采集了506个耕层土样进行系统化验、统计分析并与1983年的相应资料做比较。结果发现大理州植烟土壤肥力的主要指标有蜕化的趋势:土壤有机质平均2.77%,有下降趋势;pH平均值6.5,呈酸化趋势;碱解氮平均137.7mg/kg,呈上升趋势;速效磷平均29.7mg/kg,老烟区已累积偏高,且呈继续上升趋势,对烟叶生产不利;速效钾平均183.1mg/kg,总体较高也有上升趋势,但不平衡也有偏低的;交换性镁平均139.5mg/kg,约一半土壤偏低;速效硼0.31mg/kg,普遍缺乏或偏低;有效钼平均0.24mg/kg,约1/3缺乏;速效硫、钙、锰、铁、铜含量偏高,而含氯量偏低。烤烟施肥应减氮减磷稳钾,普遍施硼,因土施镁。在土壤pH<5.5时,应适施石灰,调节酸度。有机无机相结合,适当改变氮肥形态防止土壤进一步酸化,实施科学施肥确保植烟土壤可持续利用。  相似文献
3.
纸页匀度的一种表征方法   总被引:14,自引:2,他引:12  
通过光吸收方法测量纸页局部定量,得到定量在纸页平面的二维分布函数,通过傅立叶变换到纸页局部定量变化的几何分布特征和幅度分布特征,并以此为基础构成表征纸页均匀的特征参数-不均匀指数。对6种不同生产厂的新闻纸样品的分析结果表明,该方法可用于纸页的匀度特征的表征。  相似文献
4.
5.
食用油加热过程中反式脂肪酸的形成和变化   总被引:8,自引:3,他引:5  
对花生油、大豆油、菜籽油、玉米油和葵花籽油分别进行加热试验,采用气相色谱法测定其不同加热温度和不同加热时间脂肪酸组成,分析研究食用油中反式脂肪酸形成和变化特点及其影响因素。结果表明食用油加热至300℃时,其反式脂肪酸含量是未加热时的2倍以上;随着加热温度的升高或加热时间的延长,食用油中反式脂肪酸种类和含量都增加。加热温度、加热时间和食用油中脂肪酸组成均是影响反式脂肪酸形成和变化的因素;而反式脂肪酸受影响的程度因其种类的不同而变化。  相似文献
6.
三倍体毛白杨化学成分径向变异的研究   总被引:7,自引:0,他引:7  
为了择优选用最佳品系和确定最佳工艺成熟期,为浆纸性能评价作初步的探索,本文对9个三倍体无性系和1个二倍体无性系胸高处的化学成分按年轮进行了测定和研究,结果显示了毛白杨各化学成分在径向的变异规律为:苯醇抽出物含量在径向从髓心向外是逐渐降低的,个别无性系在最外层有反常的升高;木素含量在径向从髓心向外是成直线下降的;α-纤维素含量在约第7年达到最大值,之后有的无性系保持恒定,有的略有下降;综纤维素含量在径向随年轮的变化不大,基本上保持一条直线,与普通的二倍体毛白杨相比,三倍体毛白杨无性系的木素含量低,α-纤维素含量和综纤维素含量均较高。  相似文献
7.
烤烟叶片石油醚提物质量分数的遗传变异及稳定性分析   总被引:7,自引:0,他引:7  
以遗传基础差异较大的6个烤烟品种为亲本材料,按Griffing双列杂交试验方法2配制了15个杂交(F1代)组合,将总计21个烤烟基因型分别在商丘、郑州和信阳3地安排试验,对烤烟叶片石油醚提物质量分数的遗传变异、配合力效应和稳定性进行了分析.结果表明:1)石油醚提物质量分数在不同基因型间、叶片部位间和地点间均存在着广泛的变异.不同供试亲本相比较,以K326石油醚提物质量分数最高,中烟90次之,潘园黄最低;不同叶片部位相比较,石油醚提物质量分数表现为上部叶>中部叶>下部叶;不同供试地点相比较,石油醚提物质量分数表现为信阳>商丘>郑州.石油醚提物质量分数的广义遗传率较高,狭义遗传率偏低,该性状在遗传上受基因的加性效应和非加性效应共同控制,其中非加性作用大于加性作用.2)不同亲本石油醚提物质量分数的一般配合力效应大小因基因型和环境而异,K326的一般配合力效应较大,潘园黄的一般配合力效应较小.3)不同品种的石油醚提物质量分数对环境反应的敏感性不同,K326的稳定性较好,其次是中烟90,RG17则为具有特殊适应性的品种.  相似文献
8.
Conjugated linoleic acid (CLA) is a fatty acid with numerous putative health benefits and is a natural component of ruminant-derived food products. An intermediate in rumen biohydrogenation is cis-9, trans-11 CLA, the major CLA isomer in milk fat. However, the major source of cis-9, trans-11 CLA in milk is endogenous synthesis by delta 9-desaturase conversion of trans-11 C18:1, another rumen biohydrogenation intermediate. The desaturase indices serve as a proxy for delta 9-desaturase activity and are calculated from the ratios of fatty acid pairs that represent product/substrate for this enzyme. This study analyzed individual animal variation in milk fat content of cis-9, trans-11 CLA and in desaturase indices in milk fat. Thirty lactating Holstein cows were allocated to one of three treatment groups: one received a standard total mixed ration, one received a diet that produced an elevated milk fat content of CLA, and a third treatment group was alternated between these diets at 3-wk intervals over the 12-wk study. There was a two- to threefold variation among individuals on the same diet for both milk fat content of CLA and desaturase indices in milk fat. This hierarchy was maintained to a large extent over the 12-wk study even in the variable treatment group that alternated between the two diets. Within the variable diet treatment, some animals consistently had a substantial response in milk fat content of CLA to dietary shifts, whereas other cows had little or no response. We conclude that while diet is a major determinant of the CLA content in milk fat, individual animal differences also have a substantial effect. The variation among individuals includes differences related to both rumen biohydrogenation and delta 9-desaturase activity in the mammary gland.  相似文献
9.
Sources of variation in milk urea nitrogen in Ohio dairy herds   总被引:6,自引:0,他引:6  
The purpose of this study was to estimate the amount of variation in milk urea nitrogen (MUN) concentrations attributable to test-day, individual cow, and herd effects and to describe factors associated with MUN measurements in Ohio dairy herds. The data came from 24 Holstein herds, half of which were classified as low producing (LP) [rolling herd average (RHA) milk production < 7,258 kg] and half as high producing (HP) herds (RHA production > 10,433 kg). MUN concentration was measured from cow's monthly test-day milk samples. The data were analyzed using multilevel modeling technique in MLwiN, separately for LP and HP herds. The unadjusted mean MUN was 13.9 mg/dl for the HP herds and 11.3 mg/dl for the LP herds. The variance structure was different between the two groups. Most of the variability was found at test-day level in the LP herds, but at herd level in HP herds. MUN was lowest during the first month of lactation, and also season was associated with MUN in both groups. Test-day milk yield, milk fat percentage, and SCC were associated with MUN in the HP herds. With significant explanatory variables in the model, proportionally more of the variation was explained at herd level and less at test day level in both groups. Lower variability in MUN between test days in the HP herds may indicate more consistent day-to-day feeding and management within a herd. The great variability between test days should be considered when interpreting MUN and samples should be collected at the same time of the day to minimize day-to-day variability.  相似文献
10.
The connective tissues of fish.   总被引:5,自引:1,他引:4  
'Gaping' is a phenomenon in which the connective tissues of fish fillets fail to hold the blocks of muscle together. Slits appear across the surface of the muscle which cannot then be mechanically skinned, or, in the case of smoked salmon fillets, sliced.
Seasonal increases in the gaping of salmon fillets coincide with a fall in the postmortem pH of the flesh, occurring in June-July.
Extensive gaping can be caused by fish entering rigor mortis at too high a temperature. In trout, this temperature is considerably higher than in gadoids, suggesting that gaping from high-temperature rigor may in practice be fairly rare in salmonids.
The thermal denaturation temperature ( T D) of acid-soluble collagen isolated from the turbot farmed in warmed water does not differ significantly from that of the connective tissues of those reared at normal temperatures. This observation is discussed in relation to gaping.  相似文献
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