首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   298篇
  免费   24篇
  国内免费   16篇
林业   8篇
农学   14篇
  16篇
综合类   55篇
农作物   54篇
水产渔业   129篇
畜牧兽医   53篇
园艺   2篇
植物保护   7篇
  2024年   3篇
  2022年   6篇
  2021年   9篇
  2020年   8篇
  2019年   10篇
  2018年   11篇
  2017年   8篇
  2016年   7篇
  2015年   15篇
  2014年   17篇
  2013年   20篇
  2012年   17篇
  2011年   17篇
  2010年   19篇
  2009年   15篇
  2008年   15篇
  2007年   11篇
  2006年   10篇
  2005年   14篇
  2004年   6篇
  2003年   13篇
  2002年   7篇
  2001年   11篇
  2000年   9篇
  1999年   7篇
  1998年   10篇
  1997年   3篇
  1996年   4篇
  1995年   5篇
  1994年   9篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   5篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
  1980年   1篇
  1975年   1篇
排序方式: 共有338条查询结果,搜索用时 46 毫秒
91.
Free lipids (FL), bound lipids (BL) and total lipids (TL) were determined by the Soxhlet method in whole ground spelt (Triticum aestivum ssp. spelta L.) and hexaploid winter wheat (T. aestivum) samples. Ninety-one samples of spelt and 78 samples of winter wheat were analysed in the present study. The available material is representative of the wide variability found in spelt (true spelt forms compared with spelt wheat hybrid material). The results show that spelt differs from winter wheat by a higher FL and TL content (on average, 1·3 times and 1·2 times respectively). Furthermore, our results demonstrate that FL account for most of the high TL content of spelt as compared to winter wheat. Lipid content is a parameter which allows a distinction between spelt and winter wheat. This could be useful for breeders to classify spelt varieties.  相似文献   
92.
Dried colocasia powder (10% and 20%) was fed to hypercholesterolemic rats for a period of one month to explore the effect on serum lipids and tissue lipids. The results indicated that there was a significant increase in total lipids, total cholesterol, and triglycerides levels in the cholesterol fed rats. Liver cholesterol showed a slight reduction which was non-significant, while an increase in liver triglyceride was observed in rats fed with 10% and 20% colocasia leaves diet with or without cholesterol. All these observations indicate an aggravating effect of colocasia leaves on serum and tissue lipids in cholesterol-fed rats.  相似文献   
93.
The objective of the study was to determine the effects of methionine and cysteine supplementation of soy protein isolate and casein on serum and tissue lipid levels in rats. Sixty male, weanling, Wistar-Kyoto rats were fed two sources of protein (casein or soy protein isolate) and three variations of sulfur-amino acid supplementation (none, methionine, or cysteine). At this level of protein intake (10% by weight), rats fed soy-based diets had similar serum lipid concentrations than rats fed casein-based diets. Choline was not added to the diet in order to be able to assess independent influences of methionine and cysteine on lipid metabolism. Overall, serum lipid values were greater in rats fed proteins supplemented with methionine while the addition of cysteine produced lower lipid levels. Liver lipid concentrations were increased tremendously upon cysteine supplementation of soy protein isolate. Protein quality, as determined by protein efficiency ratio, was improved by supplementation of either sulfur-amino acid; however, methionine had the greatest effect. Results indicate that the sulfur-amino acids influence lipid metabolism in the absence of dietary choline. The mechanism by which this occurs is not known.  相似文献   
94.
The aims of this work were to evaluate the contribution of the free fatty acid (FA) pool to triacylglyceride (TAG) biosynthesis and to try to characterize the mechanism by which FA are assimilated into TAG in the green alga Dunaliella tertiolecta. A time-resolved lipidomic analysis showed that nitrogen (N) deprivation induces a redistribution of total lipidome, particularly of free FA and major polar lipid (PL), in parallel to enhanced accumulation of polyunsaturated TAG. The steady-state concentration of the FA pool, measured by prolonged 14C-bicarbonate pre-labeling, showed that N deprivation induced a 50% decrease in total FA level within the first 24 h and up to 85% after 96 h. The abundance of oleic acid increased from 50 to 70% of total free FA while polyunsaturated FA (PUFA) disappeared under N deprivation. The FA flux, measured by the rate of incorporation of 14C-palmitic acid (PlA), suggests partial suppression of phosphatidylcholine (PC) acyl editing and an enhanced turnover of the FA pool and of total digalactosyl-diacylglycerol (DGDG) during N deprivation. Taken together, these results imply that FA biosynthesis is a major rate-controlling stage in TAG biosynthesis in D. tertiolecta and that acyl transfer through PL such as PC and DGDG is the major FA assimilation pathway into TAG in that alga and possibly in other green microalgae. Increasing the availability of FA could lead to enhanced TAG biosynthesis and to improved production of high-value products from microalgae.  相似文献   
95.
试验旨在观察日粮中添加荞麦蜂花粉多糖对肉仔鸡免疫功能、血脂及抗氧化能力的影响。将200羽1日龄AA肉仔鸡随机分为空白对照组、试验1、2、3组,每组5个重复,每个重复10羽。其中对照组饲喂基础日粮,试验1、2、3组分别在基础日粮中添加500.0、1000.0、1500.0 mg/kg的荞麦蜂花粉多糖。饲养试验期为42 d。结果表明,与对照组相比,试验1、2、3组可显著提高肉仔鸡脾脏指数、胸腺指数与血清IgG含量,能显著升高血清SOD与GSH-Px活性,降低MDA含量(P<0.05)。另外,试验2、3组还可显著提高法氏囊指数与血清IgA、IgM含量,并明显降低血清胆固醇含量(P<0.05)。但各试验组对肉仔鸡生长性能、甘油三酯含量无明显影响(P>0.05)。试验结果表明,基础日粮中添加荞麦蜂花粉多糖,可明显促进肉仔鸡免疫功能,降低血清胆固醇,并明显提高肉仔鸡抗氧化能力。提示荞麦蜂花粉多糖可能是一种较好的纯天然肉仔鸡免疫增强剂与抗氧化剂。  相似文献   
96.
研究羊油、猪油、牛油、马油4种油脂对大鼠血糖、血脂及血液相关因子的影响研究。130只雄性健康SD大鼠随机分为对照组、羊油脂组、猪油脂组、牛油脂组和马油脂组共5组。各油脂组再分为高(2mL/100g体重)、中(1mL/100g体重)、低(0.5mL/100g体重)剂量3个灌胃组,对照组灌胃纯净水(1mL/100g体重)。灌胃56d后,测定各组动物体重、内脏脂肪重量、血糖(GLU)、血脂4项[高密度脂蛋白(HDL-C)、低密度脂蛋白(LDL-C)、胆固醇(TC)、甘油三酯(TG)3的变化以及脂代谢相关血液因子[血浆胰岛素(INS)、瘦素(LEP)、一氧化氮(NO)、超氧化物歧化酶(SOD)和丙二醛(MDA)]的变化。结果表明,与对照相比,4种油脂对大鼠的体重、LEP、NO影响不明显(P〉0.05);4种动物油脂的高剂量组以及猪油脂和马油脂的中剂量组均能显著增加内脏脂肪的重量(P〈0.05);羊油脂中剂量组、马油脂高剂量和中剂量组的GLU值均极显著升高(P〈0.01);羊油脂高剂量组HDL—C水平显著升高(P〈0.05),猪油脂高剂量组HDL—C水平极显著升高(P〈0.01);牛油脂高剂量组LDL—C水平显著升高(P〈0.05);牛油脂和马油脂的各剂量组TC水平均极显著升高(P〈0.01);仅羊油脂高剂量组TG水平显著升高(P〈0.05);马油脂的高、中剂量组的血浆INS水平极显著降低(P〈0.01);羊油脂和猪油脂的各剂量组MDA水平均极显著升高(P〈0.01);牛油脂和马油脂的各剂量组SOD水平均极显著升高(P〈0.01);4种油脂对大鼠的体重、血浆LEP、血浆NO没有明显影响;灌服猪油脂对大鼠GLU水平影响不明显;灌服高剂量羊油脂可明显升高大鼠血液HDL-C和TG水平;猪油脂主要表现为升高HDL-C水平;而牛油脂和马油脂各剂量组则可极显著升高血浆总胆固醇。羊油脂和猪油脂均能升高大鼠的MDA水平;牛油脂和马油脂均能升高大鼠的SOD水平,推测牛油脂和马油脂具有抗氧化的作用。  相似文献   
97.
The wheat Hardness (Ha) locus consists of Puroindoline a (Pina) and Puroindoline b (Pinb) and controls whether wheat is soft or hard textured. PINA and PINB act cooperatively to create grain softness and are associated with increased polar lipids at seed maturity. Here we examined developing seeds varying in PINA or PINB content to identify when polar lipid differences occur. One population carried Wild Type (WT) PINA while varying for the presence of PINB, while the other population carried a WT PINB and segregated for PINA. For the PINB segregating population, polar lipids were maximal on a per mg dry weight basis at 7–14 days after anthesis (DAA) while for PINA segregating population, total polar lipids were maximal at 7–21 DAA. The most abundant polar lipids at maturity were mono- and di- galactosyldiglyceride. No individual polar lipid species were specific to PINA or PINB. The effect of both PINA and PINB increased throughout seed development with greater decreases in the most abundant polar lipids in genotypes lacking either PINA or PINB. The results indicate that PINA and PINB act cooperatively to prevent polar lipid breakdown during seed maturation and that this process is central to the development of grain softness.  相似文献   
98.
Fermentation using native lactic acid bacteria (LAB) was evaluated for its effectiveness in recovering lipids and proteins simultaneously from freshwater fish visceral waste (FVW). Five different LAB isolated from fish processing waste were employed in a fermentation process that involved 10% (w/w) glucose, 2% (w/w) NaCl, and 10% (v/w) LAB. Cultures evaluated included four native isolates (Pediococcus acidilactici NCIM5368, Enterococcus faecalis NCIM5367, Pediococcus acidilactici FM37, and Pediococcus acidilactici MW2) from FVW with E. faecium NCIM5335 as the reference culture. Fermentation with native LAB resulted in recovery of > 90% oil present in the material as against no recovery in case of raw (unfermented) viscera and resulted in > 50% of degree of hydrolysis of proteins. The fatty acid profile of lipids was not affected by the fermentation process. The fermentation liquor, rich in hydrolyzed protein, exhibited antioxidant as well as antagonistic properties against several bacterial pathogens. The results clearly demonstrate the usefulness of fermentation using native isolates for simultaneous recovery of lipids and proteins from fish processing waste. It also asserts the value of fermentation as an eco-friendly method and aids in minimizing disposal/pollution problems associated with these solid wastes.  相似文献   
99.
The effects of diet freezing on the growth, survival and biochemical composition of the diets and juvenile spider crabs (Maja brachydactyla) were studied. Fresh and frozen (at ?20 °C for 21 days) mussels, Mytilus edulis, were used as food. Two experiments were conducted and in each, spider crabs were placed in individual trays. During experiment I, 40 juvenile spider crabs (2 months old) were used. Twenty animals (9 ± 2 mg) were fed fresh mussels, and 20 animals (8 ± 2 mg) were fed frozen mussels. Spider crabs fed fresh mussels grew larger than the ones fed frozen mussels (304.0 ± 118.0 and 70.0 ± 40.1 mg respectively). During experiment II, 16 juvenile spider crabs (5 months old) were used. Eight animals (3.4 ± 0.8 g) were fed fresh mussel and eight animals (4.1 ± 1.3 g) were fed frozen mussel. Spider crabs fed with fresh mussels were larger than the ones fed with frozen mussels (92.5 ± 41.7 and 41.5 ± 17.7 g respectively). There were no significant differences in the protein, amino acids and fatty acid composition between fresh and frozen mussels. The freezing procedure makes mussels less adequate for the culture of 2‐month‐old early juveniles of M. brachydactyla up to 5 months, although they promoted acceptable growth and good survival in older animals (>5 months old).  相似文献   
100.
小麦雄性不育系绒毡层异常代谢与小孢子败育的关系   总被引:1,自引:0,他引:1  
【目的】研究小麦遗传型雄性不育系花药绒毡层降解及营养物质代谢,并揭示其与花粉败育的关系。【方法】以小麦S型1376不育系[(S)-1376(A)]及其保持系[(A)-1376(B)]为试材,在三核期分别用DAPI和KI-I2对花粉粒内淀粉积累进行染色观察;采用半薄切片技术对不育系(S)-1376和保持系1376绒毡层发育过程及多糖、脂类和蛋白等物质积累进行观察和比较;采用软件cellSens Entry和IPP 6.0分别计算图片中小孢子和绒毡层细胞的面积及分析各发育时期图像中的平均光密度值。【结果】与保持系1376比较,(S)-1376花粉粒被KI-I2染成浅黄色,表明三核期其花粉中无淀粉积累,花粉败育彻底;不育系(S)-1376绒毡层较保持系1376绒毡层细胞提前至四分体时期启动细胞程序化死亡(PCD)过程;不育系(S)-1376花粉核发育迟缓,大多发育至单核晚期停止分裂,仅少数可发育至二核期;(S)-1376小孢子在四分体时期和单核早期显著增大;绒毡层细胞在四分体时期也显著大于保持系1376绒毡层细胞。在(S)-1376花粉的发育过程中,除四分体时期外,其余各时期多糖含量(呈红色)均低于保持系对应的各发育时期,不育系(S)-1376绒毡层中多糖在四分体时期多于保持系,在单核早期显著降低。在花粉整个发育过程中,不育系(S)-1376花粉中被染成黑色脂类的含量明显低于保持系,不育系绒毡层中的脂类含量在各个时期也低于保持系。不育系(S)-1376小孢子母细胞四分体时期被染成蓝色的蛋白含量很高,但单核晚期显著降低;在绒毡层细胞中单核早期蛋白含量显著低于保持系,这可能暗示该时期保持系绒毡层开始启动降解。在花粉发育整个过程中保持系1376小孢子母细胞中四分体时期多糖和蛋白的含量都低于不育系(S)-1376,这可能与该时期不育系绒毡层提前降解需要大量的多糖和蛋白有关;单核晚期小孢子中的多糖、脂类和蛋白含量高于不育系,该时期是正常小孢子发育的关键时期,不育系中各种物质供应不足可能是导致花粉败育的主要原因。在二核期和三核期,不育系(S)-1376花粉营养细胞中大液泡不消失,细胞质内含物也不持续增加,淀粉粒、脂类等物质积累终止,最终导致小孢子内没有内含物的积累,呈空壳晶体状。【结论】小麦S型1376A不育系花药绒毡层提前降解所诱发的物质异常代谢,使小孢子在由单核晚期向二核期发育的过程中物质供应不足导致细胞核分裂异常,最终引起花粉败育。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号