全文获取类型
收费全文 | 318篇 |
免费 | 30篇 |
国内免费 | 36篇 |
专业分类
林业 | 14篇 |
农学 | 19篇 |
23篇 | |
综合类 | 146篇 |
农作物 | 18篇 |
水产渔业 | 77篇 |
畜牧兽医 | 75篇 |
园艺 | 8篇 |
植物保护 | 4篇 |
出版年
2024年 | 1篇 |
2023年 | 5篇 |
2022年 | 12篇 |
2021年 | 6篇 |
2020年 | 14篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 7篇 |
2015年 | 18篇 |
2014年 | 15篇 |
2013年 | 28篇 |
2012年 | 33篇 |
2011年 | 25篇 |
2010年 | 26篇 |
2009年 | 25篇 |
2008年 | 18篇 |
2007年 | 27篇 |
2006年 | 17篇 |
2005年 | 12篇 |
2004年 | 7篇 |
2003年 | 6篇 |
2002年 | 8篇 |
2001年 | 7篇 |
2000年 | 4篇 |
1999年 | 3篇 |
1998年 | 4篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1994年 | 2篇 |
1993年 | 4篇 |
1992年 | 3篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 2篇 |
1984年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有384条查询结果,搜索用时 500 毫秒
241.
采用木薯淀粉和松香为原料,研究了酶法催化松香木薯淀粉酯的合成。通过单因素和响应面法优化了各因素对松香淀粉酯取代度影响,结果表明最佳工艺条件为:松香与淀粉的质量比为3.6∶1,反应时间4.2 h,反应温度48.5℃,固定化脂肪酶用量为15%(以淀粉质量计),此时松香淀粉酯取代度可达0.106。通过FT-IR,XRD和SEM对产物进行表征,产物在1729 cm-1产生CO的伸缩振动,说明松香与淀粉发生了酯化反应形成了松香淀粉酯,并且晶体形貌和结构发生了改变。同时对产物的性能进行了研究,结果表明,与预处理淀粉相比酯化产物的乳化能力和乳化稳定性分别增加了122.26%和134.16%、表面张力和透明度分别降低了46.9%和5.22%。 相似文献
242.
Establishment of Real-Time TaqMan-Fluorescence Quantitative RT-PCR Assay for Detection and Quantification of Porcine Lipoprotein Lipase mRNA 总被引:1,自引:0,他引:1
Porcine lipoprotein lipase (LPL) cDNA was cloned as the standard for real-time quantifying LPL mRNA and the TaqMan-fluorescence quantitative PCR assay for detection was established. The total RNA extracted from Longissimus dorsi of porcine was reverse-transcribed to cDNA. LPL cDNA was ligated with pGM-T vector and transformed into Escherichia coli TOP10. Plasmid DNA extracted from positive clones was verified by PCR amplification and sequenced. LPL was amplified by real-time fluorescence quantitative PCR from the plasmid DNA. The concentration of DNA template purified was detected by analyzing absorbance in 260 nm and then the combined plasmid was diluted to series as standard for fluorescence quantitative PCR (FQ-PCR). The method of LPL mRNA real-time PCR was well established, which detected as low as 103 with the linear range 10^3 to 10^10 copies. The standard curves showed high correlations (R2 = 0.9871). A series of standards for real-time PCR analysis have been constructed successfially, and real-time TaqMan-fluorescence quantitative RT-PCR is reliable to quantitatively evaluate FQ-PCR mRNA in L. dorsi of porcine. 相似文献
243.
本文旨在建立胰脂肪酶实时荧光定量 PCR检测方法的基础上研究纳米氧化铈对蛋鸡胰脂肪酶活性及基因表达的影响。试验选择 26周龄健康商品蛋鸡 384只,随机分为 4组,每组8个重复,每个重复 12只鸡。以玉米 -豆粕型饲粮为基础饲粮,在基础饲粮中分别添加 0(Ⅰ组)、30(Ⅱ组)、60(Ⅲ组)和 90mg/kg(Ⅳ组)的纳米氧化铈,试验期 7周。结果表明:1)本试验建立的胰脂肪酶实时荧光定量 PCR检测方法具有线性关系好,特异性、敏感性、重复性高等特点,可用于检测胰脂肪酶 mRNA表达水平;2)Ⅲ组胰脂肪酶活性显著或极显著高于Ⅰ组和Ⅳ组(P<0.05或 P<0.01),胰脂肪酶 mRNA表达水平显著高于其他各组(P<0.05)。由此得出,饲粮中添加 60mg/kg纳米氧化铈可显著提高蛋鸡胰脂肪酶活性,上调胰脂肪酶 mRNA表达水平。 相似文献
244.
The growth, survival and trypsin, lipase and amylase activities of red drum larvae were measured in two experiments. For the first trial, a group was fed live prey only (L) and another group was fed a combination of a microparticulate diet (MPD) and live food (L-MP). For the second growth trial a group fed the MPD only (MP) and a starvation group (ST) were examined in addition to the L and L-MP treatments. Enzyme activities of live prey were measured to estimate their possible contribution to larval digestion. No significant ( P > 0.05) differences in final size and survival were observed between treatments L and L-MP. Larvae subjected to starvation or fed the MPD diet alone were smaller than treatments fed live prey and did not survive past days 5 and 14, respectively. Trypsin, lipase and amylase activities were detectable at hatching. No significant differences ( P > 0.05) in total enzyme activities among treatments were observed before day 14. Specific activity of trypsin, lipase and amylase peaked on day 3 (prior to first feeding) and subsequently decreased. For trypsin, the percentage of enzyme activity potentially attributable to ingested prey increased with age to a maximum of 17%. For lipase and amylase this fraction was less than 5% throughout the study, except on day 8 (12% and 24%, respectively). The lack of significant differences observed in the activity of digestive enzymes among treatments suggests that dietary regime, availability of prey and possible effects of exogenous enzymes did not significantly influence enzyme activity. Therefore, the lower growth rate observed in the L-MP, MP and starved treatments cannot be attributed to low digestive enzyme production of the enzymes measured. It is more likely that the MPD failed to supply the required nutrients for adequate development. 相似文献
245.
G. I. O. Badifu A. O. Ogunsua 《Plant foods for human nutrition (Dordrecht, Netherlands)》1991,41(1):35-44
The seeds of lesser-known species —Cucumeropsis mannii, Lagenaria sicceraria varities 1 and 2 andTelfairia occidentalis, ofCucurbitaceae family were studied. The protein content ofC. mannii was 36.1% and the varieties 1 and 2 ofL. sicceraria had 32.1% and 33.3% respectively.Telfairia occidentalis had protein content of 33.2%. The fat contents ofC. mannii, L. Sicceraria var. 1 and 2 andT. occidentalis were 44.4%, 44.6%, 46.9% and 42.3% respectively. The crude fibre content for each of the two varieties ofL. sicceraria was 3.6% andT. occidentalis had 5.5%.Cucumeropsis mannii had the lowest (2.4%) fibre content. The carbohydrate contents forL. Sicceraria var. 2,C. mannii, andT. occidentalis were 12.6%, 13.2% and 14.4% respectively.Lagenaria sicceraria var. 1 had the highest value of carbohydrate (15.8%). The species were relatively rich in potassium and magnesium with range of values of 0.56% to 0.68% and 434 ppm to 444 ppm respectively.Cucumeropsis mannii andLagenaria sicceraria var. 2 had relatively high contents of calcium (117 ppm) and iron (109 ppm) respectively. The kernels of these species exhibited lipase activity.Telfairia occidentalis showed the highest degree of lipase activity. 相似文献
246.
247.
248.
现有自深圳海域分离出的真菌31株,其中包括22株丝状真菌和9株酵母菌.对各菌株进行纤维素酶、脂肪酶和漆酶等胞外酶的定性筛选后,进行胞外酶定量分析.结果表明,在定性初筛的培养基生长5d后,大多数菌株呈现出2~3种胞外酶活力的溶解圈,而9个酵母菌菌株都没有检出漆酶活力.在定性测量的结果基础上,挑选出产酶潜力大的2株丝状真菌(PKU F16、PKU F18)和2株酵母菌(PKU Y5、PKU Y8),进行3种胞外酶的定量分析.在各菌株培养4、6、9d时,分别对3种胞外酶活进行测定,结果发现各菌株生产3种胞外酶的定量分析结果与定性分析结果基本吻合,且随着培养时间的增长,菌株的胞外酶活力呈现先增后减的趋势.在第6天,F18和Y8产纤维素酶活力分别高达1.13、1.31 U/min·mL.Y8的脂肪酶活力产量高达21.94 U/min·mL.F18和F16产漆酶活力高达14.61、10.50 U/min· mL. 相似文献
249.
重点对日本鲐鱼片和鱼糜分别用扩展青霉PF868产生的碱性脂肪酶酶解法与漂洗压榨的理化法脱脂工艺效果进行比较,研究结果表明,对鲐鱼片,理化法(残脂率11.01%,按干基计,下同)优于酶解法(残脂率19.48%),而对鱼糜,酶解法(残脂率3.49%)大大优于理化法(残脂率7.52%),筛选出的脂肪酶的适宜酶解条件为pH8.7-9.2,温度32℃,酶液活度40U.mL^-1, 酶液与底物比为5:1,脱脂时间50min,鲐鱼糜在上述酶解条件下,残脂率可达4%以下,而采用理化法脱脂,残脂率只能达到8%左右,无论酶法还是理化法,均难使鲐鱼片残脂率达到10%以下。 相似文献
250.