全文获取类型
收费全文 | 298篇 |
免费 | 24篇 |
国内免费 | 16篇 |
专业分类
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 |
出版年
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 15 毫秒
121.
A greenhouse study was conducted to determine the effect of nitrogen supply (30, 100 or 170 ppm N) and raceme position on the fatty acid composition of oil extracted from erucic acid-free summer rape seed ( Brassica napus cv. Callypso ). The seven fatty acids analyzed for include palmitic, palmitolcic, stearic, oleic, linoleic, linolemc, and eicosenoic acids; of which oleic (59.54–64.84 %) and palmitoleic (0.36–0.4 %) acids were the highest and lowest levels respectively. Generally, N nutrition influenced fatty acid pattern only to a little extent. Palmitic, palmitoleic and stearic acid levels were increased by 170 ppm N, depending on raceme position, but oleic and linolenic acids were unaffected. Similarly, 170 ppm N produced the highest fatty acid levels in seeds on the lower portions of racemes, with the exception of oleic acid. This was also true in the case of the upper portions of racemes, except that 30 ppm N produced the highest levels of oleic and linoleic acids in rape seeds. Under the optimum N supply level (i.e. 100 ppm N), position of raceme on the rape plant did not greatly influence the levels of different fatty acids in lipids. 相似文献
122.
Developing siliquas on the mustard inflorescence were sampled at basal, middle and apical positions and the changes in free sugars and starch in pod wall and seed vis-á-vis oil-filling in the seeds were studied. The dry matter and oil content per seed and pod wall was highest at initial stages in apical followed by mid-development stages in middle and late development stages in basal positions. The oil percentage m the pod wall decreased with the period of siliqua development. The phase of rapid oil filling in the seeds varied from 20 to 40 DAF (days after flowering) in basal to 10 to 30 DAF in middle and 10 to 20 DAF in apical positions. The content of starch and total soluble sugars (% dry weight basis) decreased in the seeds as well as pod walls but showed accumulation on per seed basis with a maximum at 20, 30 and 40 DAF while on pod wall basis, the maxima of total soluble sugars was at 20, 20 and 40 DAF in apical, middle and basal position respectively. In the pool of total soluble sugars, the proportion of non-reducing sugars was predominant. The activity of invertase (EC 3.2.1.26) declined while those of a-amylase (EC 3.2.1.1) and β-amylase (EC 3.2.1.2) showed maximum values in the seeds as well as pod wall during the phase of rapid oil-filling in the seeds. The results suggested that ontogeny and duration of seed development vis-á-vis the environmental conditions played an important role in lipid biosynthesis in mustard seeds. 相似文献
123.
Metabolic response of the gastrointestinal tract and serum parameters of rabbits to diets containing chicory flour rich in inulin 总被引:1,自引:0,他引:1
Juśkiewicz J Asmanskaite L Zduńczyk Z Matusevicius P Wróblewska M Zilinskiene A 《Journal of animal physiology and animal nutrition》2008,92(2):113-120
A 36-day experiment carried out on 54-day-old rabbits addressed the analysis of physiological properties of diets supplemented with chicory roots flour. Twenty-four rabbits were allocated in individual cages to three treatments, in which they were fed each diet with the chicory flour at 0, 25 and 50 g/kg (control, ChF(2.5) and ChF(5) groups respectively). The chicory preparation administered at a higher dose, lowered ileal pH and viscosity, and evoked increased hydration of ileal and caecal digesta, compared to the control treatment (p = 0.05). The ChF(2.5) group was characterized by the highest increase in the bulk of digesta and concentration of protein in the caecum (p < 0.05 vs. control). The lowest colonic pH was found in the ChF(5) group (p = 0.05 vs. control). Compared to the control group, both chicory treatments effectively (p = 0.05) diminished the activity of the potentially harmful bacterial enzymes beta-glucosidase and beta-glucuronidase in the caecal and colonic digesta. The ChF(2.5) group was characterized by a significantly higher volatile fatty acids (VFA) pool size in the caecum, whereas rabbits fed the ChF(5)diet had the highest colonic VFA pool size (p = 0.05 vs. control). The lowest level of triglycerides and total cholesterol, at concurrently the highest proportion of high-density lipoprotein (HDL) fraction in the HDL/total cholesterol profile, were recorded in the plasma of rabbits fed the ChF(5) diet. In conclusion, the chicory flour rich in inulin, exerted positive effects on the rabbit gastrointestinal tract physiology and would be a potential source of functional feed additives. 相似文献
124.
125.
日粮对双向选择血浆极低密度脂蛋白肉鸡生长性能和血脂的影响 总被引:1,自引:0,他引:1
对708只(公,母各半)5~9周龄选择一个世代的高、低脂蛋白(VLDL)系鸡进行不同代谢能水平、粗蛋白水平的两个品系3因子交叉的遗传-营养互作试验,以探讨品系与日粮互作对肉鸡生长性能和血脂的影响。品系、日粮粗蛋白质和代谢能间的互作对9周龄血浆极低密度脂蛋白(VLDL)、甘油三酯及总脂浓度有显著影响(P<0.01),而对血浆胆固醇浓度无明显影响。高VLDL系血浆VLDL浓度(O.D.)有随日粮粗蛋白水平的升高而降低之趋势,而低VLDL系无此规律。高VLDL系血浆总脂浓度随日粮蛋白水平的升高而降低(P<0.0001),而蛋白水平对低VLDL系血浆总脂浓度无明显影响。低VLDL系血浆VLDL浓度(O.D.)随日粮代谢能水平的升高而降低(P<0.0001),而高VLDL系无此规律。高VLDL系血浆甘油三脂浓度随日代谢能水平的升高而升高,而低VLDL系无此规律。高VLDL系血浆总脂浓度随日粮代谢能水平的升高而升高,而代谢能水平对低VLDL系血浆总脂浓度无明显影响。血浆甘油三酯和胆固醇浓度存在品系-性别互作效应(P<0.01,P<0.05);性别与日粮蛋白水平互作对血浆VLDL、胆固醇和总脂浓度均有显著影响(P<0.0 相似文献
126.
高温逆境对菜豆类囊体膜脂的影响 总被引:4,自引:1,他引:3
以耐热性不同的菜豆品种为材料,研究高温胁迫下类囊体膜脂脂肪酸组成及饱和度的变化。结果表明:高温胁迫下,菜豆类囊体膜脂饱和度均提高,但耐热菜豆品种类囊体膜脂饱和度提高幅度远远高于热敏感菜豆品种。本实验在脂肪酸水平上说明耐热菜豆品种较热敏感菜豆品种对高温逆境有较强的耐受性。 相似文献
127.
主要研究了脂类植物硬脂酸、液体石蜡、蔗糖酯对羧甲基纤维素膜的成膜特性的影响。结果表明:硬脂酸能明显降低膜的水蒸汽透过系数,但对膜的机械性能影响不大;ρ=0.003g/mL石蜡不仅可明显提高膜的阻湿性,而且使膜具有最大的抗拉强度;石蜡-硬脂酸联合作用于薄膜可使膜的阻湿性比两者单独作用时均得到显著的提高;蔗糖酯可提高膜的阻湿性,但会降低膜的抗拉强度而使膜具有较大的延伸率。 相似文献
128.
129.
为比较分析不同产地海带的脂肪酸组成,本研究采用溶剂法对海带总脂提取条件进行优化,并通过气相色谱-质谱技术对福州、宁波和青岛3个产地海带的总脂脂肪酸组成进行比较分析。结果表明,二氯甲烷-甲醇法提取海带总脂的效率较高,是海带总脂提取的理想方法;福州、宁波和青岛海带的总脂含量依次为0.75%、0.69%和0.86%,且无显著差异。从海带总脂中共鉴定出30种脂肪酸,以 C16:0、C18:1n-9、C20:4n-6(AA)和C20:5n-3(EPA)为主,且3个产地海带在脂肪酸组成上存在显著差异。福州产地海带中的C20:4n-6和C20:5n-3含量分别为10.12%、6.18%,其中C20:4n-6含量显著高于宁波(9.41%)和青岛(8.77%),C20:5n-3含量显著低于宁波(8.13%)和青岛(9.40%),进而使3个产地海带中的n-3 PUFA、n-6 PUFA、n-3/n-6、EPA+AA和EPA/AA等指标存在显著差异。本研究结果为不同产地海带总脂提取、脂肪酸比较分析及营养评价提供了一定的理论依据。 相似文献
130.
Crop rotation and seasonal effects on fatty acid profiles of neutral and phospholipids extracted from no‐till agricultural soils 下载免费PDF全文
A. E. Ferrari S. Ravnskov J. Larsen T. Tønnersen R. A. Maronna L. G. Wall 《Soil Use and Management》2015,31(1):165-175
Analysis of phospholipids (PLFA) and neutral lipids fatty acids (NLFA) was used to characterize no‐till productive agricultural soils associated with different crop rotation levels, replicated across a 400 km transect in the Argentinean pampas, during two sampling seasons, summer and winter. High rotation (HR) management consisted in maize–wheat–soybean intense rotation including cover crops. Low rotation (LR) management trend to soybean monocultures. Soils from nearby natural environments (NEs) were used as references. Fatty acids concentration in soils (nmol/g) decreased c.a. 50% from summer to winter differentially according to soil treatment being the smallest decrease in HR management 35%. Both PLFA and NLFA profiles showed strong potential to discriminate between different land uses. In winter samples, some rare or unknown fatty acids were relevant for the discrimination of agricultural practices while NLFA 20:0 appears to be a good marker of HR soils despite season or location. The PLFA‐based taxonomic biomarkers for total bacteria, Gram‐negative bacteria and arbuscular mycorrhiza showed a significant trend NE>HR>LR in the winter sampling. HR management was also characterized by high levels of NLFA in winter samples as if high crop rotation improves lipids reserves in soil during winter more than in monocropping soil management. In conclusion, PLFA and particularly NLFA profiles appear to provide useful and complementary information to obtain a footprint of different soil use and managements, improving soil biochemistry characterization tools. 相似文献