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1.
Effects of high ester pectin+α-amylase+sucrose (GNFZ), a high ester pectin+sucrose (BIG), xanthan gum (XANTHAN) and hydroxypropylmethylcellulose (HPMC) on wheat dough performance have been studied. Effects of hydrocolloids added singly and in association at different levels, on the investigated rheological, mechanical and thermal parameters have been evaluated by response-surface methodology. Optimum hydrocolloid formulations for white wheat bread are recommended.Positive linear and negative quadratic significant effects of GNFZ were observed on both the gluten index (GI) and the energy of dissociation of the amylose–lipid complex (ΔHx). Optimized dosage of 1.36 g GNFZ/100 g flour, d.b. (maximum of the respective response surface plot) led to maximized values for both GI and ΔHx, described as good indicators and predictors of the quality of fresh and stored formulated breads to be obtained. The strengthening effect of high ester pectin was reinforced by the negative quadratic effect of GNFZ on gluten extensibility, the positive effect of GNFZ/HPMC on the resistance to extension of gluten, and the negative synergistic effect of the pair BIG/HPMC on dough extensibility. XANTHAN when added singly induced desirable increase in dough resistance to extension, and the incorporation of the pair XANTHAN/GNFZ into dough formula is recommended because of the reduction of the induced degree of softening during mixing (farinograph) of GNFZ formulated doughs. A dosage of 0.109 g XANTHAN/100 g flour annulate the softening effect of GNFZ when added at an optimized dose of 1. 36 g GNFZ/100 g flour. Caution should be applied when added XANTHAN in presence of BIG because of the decrease in the extent of amylose–lipid complexation. Addition of HPMC at a level <1/>1 moderate/enhance, respectively, the effect of GNFZ on the resistance to extension of the gluten, and the water binding capability of BIG, and in this respect the incorporation of the cellulose derivative is encouraged at a dose dependent on the required effect.  相似文献
2.
烟蚜与烟蚜茧峰相互关系研究   总被引:2,自引:0,他引:2  
研究结果表明,烟蚜茧蜂对烟蚜呈典型的Holling-Ⅱ型功能反应,参数a=3.698/罩·天.Th=0.0174天;该蜂对烟蚜生长发育和繁殖的影响因被寄生时蚜虫龄期不同而异,而蜂幼虫的发育不受寄生时蚜虫龄期的影响。当1~2龄蚜虫被寄生时,一般不能发育到成蚜期产蚜:从2龄中期起,蚜虫的生殖力和种群内禀增长率rm随着被寄生蚜虫龄期的增大而上升。由此可见,被寄生时蚜虫虫龄大小对蚜茧蜂寄生效果起着决定性的作用,寄生时蚜虫龄期越大,寄生作用越不明显。  相似文献
3.
研究了一类周期捕食与被捕食系统的持久性,其中食饵在斑块环境中扩散.在斑块动力系统具有Beddington-DeAngelis功能反应时,给出了一个捕食者与食饵永久持续生存的充要条件.  相似文献
4.
The functional response of Anisopteromalus calandrae (Howard) parasitizing 4th-instar Rhyzopertha dominica (F.) on wheat was estimated over a range of temperatures and host densities. A functional response equation was used in which a quadratic component that included temperature was substituted for handling time. The instantaneous search rate increased with increasing temperatures. The maximum rate of parasitization was 13 larvae/24 h at 30°C and 35°C. Handling time was lowest at 30°C and highest at 20°C. The ability of A. calandrae to find and parasitize R. dominica over a broad range of temperatures makes it a good candidate for natural control of stored grain pests.  相似文献
5.
The functional response of Theocolax elegans (Westwood) parasitizing the lesser grain borer, Rhyzopertha dominica (F.) was examined over a range of temperatures. A type II functional response equation was fitted to each temperature regime. The parasitization rate was highest at 30°C (20 hosts per day) and was lowest at 20°C (2 hosts per day). Handling time was inversely proportional to temperature, and ranged from 1.6 days at 20°C to 0.05 days at 30°C. Instantaneous search rate also changed with temperature. It was lowest at 20°C and highest at 30°C. A temperature-mediated functional response equation was fitted to the data, in which handling time was a quadratic function of temperature. The equation explained 74% of the variance in parasitization rate. Theocolax elegans has a narrower optimal temperature range than other parasitic stored-product Hymenoptera. Temperatures greater than 32.5°C caused high parasitoid mortality.  相似文献
6.
研究一类具有双密度制约的HollingⅡ类功能反应的捕食系统收获模型,运用微分方程定性稳定性理论分析了模型平衡点的性态,给出了系统极限环不存在的充分条件,利用Pontryagin最大值原理得到系统的最优捕获策略.  相似文献
7.
研究N维情况下具有C—M型功能反应函数的非均匀恒化器竞争模型.应用局部分歧理论,讨论该模型方程组平衡态非负非平凡局部分歧解的存在性及稳定性;依据全局分歧理论,分析该系统全局分歧解的存在性及其性态.说明当选取适当参数时,2种微生物可共存.  相似文献
8.
研究了一类具有双线性密度制约Holling Ⅲ类功能反应的非自治捕食收获系统模型.利用比较原理,得到系统一致持久的充分条件.通过构建Liapunov函数,运用Barbalart引理,得到了对应周期系统存在惟一全局渐近稳定正周期解的充分条件.  相似文献
9.
研究了一类具有B-D功能反应及捕食者和食饵均具有阶段结构的两种群非自治捕食系统,通过微分方程定性与稳定性理论和Brouwer定理,得到了系统的一致持久性和周期系统存在惟一全局渐近稳定的周期解的充分条件  相似文献
10.
研究一类具有双线性密度制约及Beddington-DeAngelis功能反应的捕食系统收获模型.运用微分方程定性稳定性理论讨论系统正平衡点的性态,得到其局部渐近稳定及全局渐近稳定的充分条件,利用Pontryagin最大值原理得到系统的最优收获策略.  相似文献
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