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   617篇
  免费   48篇
  国内免费   44篇
林业   5篇
农学   16篇
基础科学   2篇
  11篇
综合类   184篇
农作物   28篇
水产渔业   95篇
畜牧兽医   351篇
园艺   12篇
植物保护   5篇
  2024年   2篇
  2023年   9篇
  2022年   16篇
  2021年   26篇
  2020年   21篇
  2019年   26篇
  2018年   20篇
  2017年   41篇
  2016年   30篇
  2015年   27篇
  2014年   28篇
  2013年   40篇
  2012年   42篇
  2011年   47篇
  2010年   30篇
  2009年   36篇
  2008年   20篇
  2007年   27篇
  2006年   39篇
  2005年   22篇
  2004年   16篇
  2003年   23篇
  2002年   18篇
  2001年   16篇
  2000年   13篇
  1999年   9篇
  1998年   8篇
  1997年   9篇
  1996年   7篇
  1995年   5篇
  1994年   10篇
  1993年   2篇
  1992年   6篇
  1991年   4篇
  1990年   4篇
  1989年   3篇
  1988年   2篇
  1987年   2篇
  1986年   1篇
  1984年   1篇
  1978年   1篇
排序方式: 共有709条查询结果,搜索用时 906 毫秒
71.
A lean phenotype has been detected in vitamin D receptor (VDR) knockout mice; however, the gender differences in fat metabolism between male and female mice both with age and in response to a high‐fat diet have not been studied before. The objective of our study was to assess changes in body and fat tissue weight, food intake and serum cholesterol and triglyceride in VDR knockout mice from weaning to adulthood and after a challenge of adult animals with a high‐fat diet. Although VDR knockout mice of both sexes consumed more food than wild‐type and heterozygous littermates, their body weight and the weight of fat depots was lower after 6 months on a diet with 5% crude fat content. When adult animals were challenged with a high‐fat diet containing 21% crude fat content for 8 weeks, VDR knockout mice of both sexes had a significantly higher food intake but gained less weight than their wild‐type littermates. Cholesterol levels were higher after 2 days on the high‐fat diet in both sexes, but in the VDR knockout mice, less cholesterol was detected in the serum after 8 weeks. Wild‐type male mice showed signs of fatty liver disease at the end of the experiment, which was not detected in the other groups. In conclusion, lack of the VDR receptor results in reduced fat accumulation with age and when adult mice are fed a high‐fat diet, despite a higher food intake of VDR knockout mice relative to their wild‐type littermates. These effects can be detected in both sexes. Wild‐type male mice react with the highest weight gain and cholesterol levels of all groups and develop fatty liver disease after 8 weeks on a high‐fat diet, while male VDR knockout mice appear to be protected.  相似文献   
72.
挑选1500只34周龄罗曼粉蛋鸡,随机均分为3个处理组,对照组饲喂基础饲粮,试验组分别饲喂添加了300 mg/kg的五倍子单宁酸(GTA)和没食子酸丙酯(PG)的基础饲粮,预试期1周,正试期8周,探究饲喂GTA和PG对产蛋高峰期蛋鸡的产蛋性能、蛋品质及血液生化指标的影响。结果表明:与对照相比,饲粮添加GTA和PG对蛋鸡产蛋性能无显著影响;饲粮添加GTA能显著改善试验8周时的蛋黄着色,但饲粮添加GTA和PG对蛋白高度、哈氏单位、蛋黄比例、蛋壳强度和蛋壳厚度均无显著影响;饲粮添加GTA能显著降低蛋鸡血浆中总蛋白(TP)、白蛋白(ALB)、球蛋白(GLB)和胆固醇(TC)的含量,有降低葡萄糖(GLU)、甘油三酯(TG)、高密度脂蛋白胆固醇(HDL–C)和低密度脂蛋白胆固醇(LDL–C)水平的趋势;饲粮添加PG能显著降低血浆TP和ALB水平,有降低GLU、GLB、TG、TC和HDL–C水平的趋势;饲粮添加GTA和PG对蛋鸡血清肝损伤指标(谷丙转氨酶、谷草转氨酶、碱性磷酸酶活性)和抗氧化指标(超氧化物歧化酶、谷胱甘肽过氧化物酶、过氧化氢酶活性和丙二醛含量)均无显著影响,但饲粮添加GTA能显著降低血清细胞炎症因子(白细胞介素–1、白细胞介素–6、肿瘤坏死因子–?)水平,饲粮添加PG可提高血清免疫球蛋白Y、M质量浓度。可见,在本研究条件下,饲粮中添加300 mg/kg的GTA和PG对罗曼粉蛋鸡的产蛋性能无显著影响,但GTA能提高蛋黄着色;饲粮添加GTA下调蛋鸡血脂、血浆蛋白及血清炎症因子水平的作用均大于PG的;饲粮添加PG可提升机体的免疫水平。  相似文献   
73.
74.
Alternative sources of lipoproteins in semen extenders could replace animal by-products. We hypothesized that: (1) post-thaw semen parameters and fertility would not be different in coconut water (CW)–treated samples compared with egg yolk (EY)–treated samples and (2) the use of an oxygen scavenger (Oxyrase) would improve post-thaw sperm motility and membrane integrity and decrease lipid peroxidation. Experiment 1: three ejaculates each from five stallions were split into four treatments: EY, CW, egg yolk with Oxyrase, and coconut water with Oxyrase. Computer-assisted sperm analysis measured progressive and total motility, velocity, and linearity. Membrane integrity, apoptosis, and lipid peroxidation were evaluated using propidium iodide, annexin, and BODIPY fluorescent probes, respectively. Samples were cryopreserved, stored in liquid nitrogen, and then thawed to 37°C and analyzed again. Experiment 2: one ejaculate was divided into two aliquots and cryopreserved using either CW or EY. In a crossover design, 12 mares were bred on two consecutive cycles with either EY or CW. Pregnancy evaluations were at 14-day gestation. No differences were detected in sperm parameters between CW and EY (P > .05). Oxyrase did not improve sperm motility parameters in post-thaw samples, nor did it show protective effects for viability or against membrane damage (P > .05). More mares became pregnant using CW than EY (11/12 vs. 6/12, respectively; P = .013). Use of CW is a viable alternative to animal-based products in the cryopreservation of stallion semen.  相似文献   
75.
[目的]在基础日粮的水平上添加中药复方,纯中药全程饲喂,对保育阶段仔猪血清中胆固醇和脂蛋白含量进行测定,为该中药复方对保育阶段仔猪增强机体抵抗力,降低抗生素在畜牧业的应用,形成质量可靠的“无抗”猪肉提供帮助。[方法]试验选用80头(28±2)日龄、体重相近的“杜×长×大”三元杂交断奶仔猪,随机分为4个处理,每个处理2个重复,每个重复10头仔猪。第1组为对照组,饲喂基础日粮,第2、3、4组在饲喂基础日粮的基础上分别添加1.5%、1.0%和0.5%的中药复方,试验期4周。试验结束第2天上午9:00空腹,前腔静脉采血,进行全血血常规指标测定。[结果]与对照组相比,饲料中添加中药复方组保育仔猪血清中脂蛋白脂肪酶含量均有升高,其中,添加0.5%中药复方组与对照组相比差异显著(P<0.05);与对照组相比,饲料中添加中药复方组保育仔猪血清中高密度脂蛋白含量均有升高,其含量随中药复方添加量的减少而逐渐降低,各中药复方添加组与对照组相比差异均不显著(P>0.05);与对照组相比,饲料中添加中药复方组保育仔猪血清中低密度脂蛋白含量均有所下降,其含量随中药复方添加量的减少而逐渐降低,其中,添加0.5%中药复方组与对照组相比差异极显著(P<0.01);与对照组相比,饲料中添加中药复方组保育仔猪血清中三酰甘油含量均有下降,其含量随中药复方添加量的减少而逐渐降低,各中药复方添加组与对照组相比差异均不显著(P>0.05)。[结论]在基础日粮中添加中药复方组保育仔猪血清中脂蛋白脂肪酶含量、高密度脂蛋白含量均有升高;保育仔猪血清中低密度脂蛋白含量、三酰甘油含量均有降低。  相似文献   
76.
This study was conducted to compare the efficacy of diet supplemented with non-microencapsulated lutein (NL) and microencapsulated lutein (ML) in laying hens. A total of 270 Hy-line Brown laying hens (54 weeks old) were allocated to three groups with six replicates of 15 hens and were adapted to a wheat-soybean meal basal diet for two weeks. Next, the control birds were fed the basal diet, and the test birds were fed the basal diet supplemented with 600 mg/kg NL (12 mg/kg available lutein) or 90.1 mg/kg ML (10 mg/kg available lutein) for 35 days. Supplementation of lutein did not affect the productive performance of laying hens, but improved (P<0.05) the yolk color and red/green value (a*), with eggs from the ML group displaying improved color and a* values from the 15th day of the experimental period. The blue/yellow value (b*) for the yolk showed an increase (P<0.05) through both NL and ML supplements. The yolk color of fried and boiled eggs and a* value of the yolk in fried eggs were improved (P<0.05) only through ML supplemented diet. Both NL and ML supplements resulted in lower (P<0.05) lightness and higher (P<0.05) a* values of yolk in boiled eggs, as well as higher (P<0.05) b* values in fried and boiled eggs. Yolk lutein content in fresh, fried, and boiled eggs was increased (P<0.05) in NL and ML groups with the latter being higher. In conclusion, ML improved yolk pigmentation and lutein retention in laying hens better than NL.  相似文献   
77.
胆固醇的代谢,即胆固醇的合成和转化过程,尤其是胆固醇和胆汁酸之间的相互转化是胆固醇降解的主要通路。胆固醇的代谢和调控紊乱,以及高胆固醇血症所引起的如动脉粥样硬化等心血管疾病的研究越来越多,同时治疗这种高胆固醇血症相关疾病的药物也相继发现。论文通过对胆固醇的代谢途径、调控机制、高胆固醇疾病及其治疗药物进行综述,对胆固醇的来源、去路以及该代谢过程中的调控机制进行较为全面的探讨,为与胆固醇相关疾病及其治疗研究提供依据。  相似文献   
78.
为研究蛋鸡日粮中添加亚麻籽对蛋黄中多不饱和脂肪酸富集的影响,根据相关标准,采用人工和系统的检索方法检索相关文章,并用荟萃分析(Meta-analysis)的方法分析计算合并标准均数差(SMD)及95%置信区间(95%CI)。通过检索与筛选,共有8篇文章21个试验被纳入,共包括1390个研究对象。Meta分析的结果显示:蛋黄中亚麻酸(ALA)、二十二碳六烯酸(DHA)、亚油酸(LA)、总n-3多不饱和脂肪酸(n-3PUFA)、花生四烯酸(AA)、总n-6多不饱和脂肪酸(n-6PUFA)、n-6PUFA/n-3PUFA的SMD和95%CI分别为17.51(13.34,21.69)、5.39(4.22,6.55)、0.42(-0.39,1.23)、8.86(7.59,10.14)、-1.62(-2.54,-0.70)、-0.44(-0.97,0.08)和-5.22(-6.62,-3.82);混合线性模型的结果显示:DHA和n-3PUFA的异质性来源为亚麻籽添加剂量,蛋黄中ALA、AA、LA和n-6PUFA/n-3PUFA的异质性来源为亚麻籽的添加剂量和蛋鸡产蛋周龄。由分析结果可知,蛋鸡日粮中添加亚麻籽能显著提高蛋黄中的ALA、DHA及n-3PUFA的含量并能显著降低AA和n-6PUFA/n-3PUFA的水平,且富集水平受到亚麻籽添加剂量和蛋鸡产蛋周龄的影响。  相似文献   
79.
鸡蛋粉是一种良好的蛋白质资源,富含免疫活性物质,在减少动物腹泻、增强机体免疫力方面具有重要功效。本文综述了鸡蛋粉的生产工艺、营养价值以及鸡蛋粉和特异性卵黄抗体在猪生产中的应用现状。  相似文献   
80.
This study was conducted to test the hypothesis that dietary supplementation with anti‐E. coli, chicken egg yolk immunoglobulins (IgY), may affect early weaned piglet (EWP) intestinal functions and enteric micro‐organisms. One hundred and forty‐eight ([Landrace × Yorkshire] × Duroc) piglets, weaned at age day 21, were randomly assigned to receive one of three diets for 14 days. Treatment group one (control group) was fed the base diet. Treatment group two (antibiotics group) was fed the base diet which was supplemented with 100 ppm colistin sulphate and 15 ppm enramycin; treatment group three (IgY group) was fed the base diet which was supplemented with 500 mg/kg anti‐E. coli IgY. The study evaluated the effects on EWPs of IgY on growth, serum biochemical, inflammatory profiles and also digestion content intestinal bacterial populations. Results showed no significant difference in diarrhoea rates between IgY‐fed EWPs and antibiotic‐treated EWPs. Serum biochemical analysis showed that EWPs fed an IgY‐containing diet had both lower (p < 0.05) cholesterol and low‐density lipoprotein compared to antibiotic‐treated EWPs. Escherichia coli populations measured in IgY‐fed EWP ileal contents, compared to the control group, were significantly reduced (p < 0.05). Enterococcus, Lactobacillus, Clostridium and Bifidobacterium populations were unaffected by the IgY treatment. Larger (p < 0.05) Enterococcus populations and lower (p < 0.05) expression levels of heat‐stable enterotoxin b (STb) were observed in IgY‐fed EWP caecal digesta compared to the control group. Enteric Lactobacillus significantly decreased (p < 0.05) in EWPs fed antibiotics while it was unaffected by IgY treatment. Dietary supplementation with anti‐E. coli IgY has the potential to suppress enteric E. coli growth, but not Lactobacillus, Clostridium and Bifidobacterium. This promotes and maintains a healthy EWP intestinal environment. These findings suggest that IgY may be used as an alternative to antibiotics in EWP diets.  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