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   731篇
  免费   59篇
  国内免费   36篇
林业   81篇
农学   49篇
基础科学   34篇
  38篇
综合类   258篇
农作物   52篇
水产渔业   21篇
畜牧兽医   267篇
园艺   18篇
植物保护   8篇
  2024年   10篇
  2023年   17篇
  2022年   25篇
  2021年   33篇
  2020年   25篇
  2019年   49篇
  2018年   21篇
  2017年   34篇
  2016年   42篇
  2015年   39篇
  2014年   32篇
  2013年   49篇
  2012年   48篇
  2011年   62篇
  2010年   32篇
  2009年   45篇
  2008年   46篇
  2007年   34篇
  2006年   25篇
  2005年   25篇
  2004年   22篇
  2003年   16篇
  2002年   14篇
  2001年   13篇
  2000年   4篇
  1999年   7篇
  1998年   8篇
  1997年   7篇
  1996年   6篇
  1995年   8篇
  1994年   4篇
  1993年   10篇
  1992年   2篇
  1991年   1篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   2篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有826条查询结果,搜索用时 31 毫秒
801.
Glycemic index of grain amaranth, wheat and rice preparations was studied in noninsulin dependent diabetic subjects. Diets containing 50 g carbohydrate equivalent were given and post-prandial blood glucose estimated at different intervals. Glycemic index calculated for different experimental diets showed that GI of amaranth-wheat composite flour diet (25∶75) was the least (65.6%) followed by wheat diet (65.7%), rice diet (69.2%), amaranth-wheat flour 50∶50 (75.5%), and popped amaranth in milk (97.3%). Therefore 25∶75 combination of amaranth and wheat, wheat and rice can be considered low GI food, 50∶50 grain amaranth and wheat medium GI food and popped amaranth and milk combination high GI food.  相似文献   
802.
Samh seeds obtained from Al-Jouf area were ground into flour analyzed and used as a replacement for wheat in the ratio of 10, 20 and 30% for bread and 30, 60 100% for cookies. The rheological effect of the Samh flour on Saudi wheat flour was also studied. The bread and cookies obtained were evaluated physically and by sensory evaluation. The results obtained indicated that samh flour has high protein content and could be used as a replacement for wheat flour upto 30% without adversely affecting the bread specific volume much. Samh flour has improved the cookies appearance specially the colour (chocolate colour) and spreading ratio. The results also revealed that it is possible to make cookies from 100% samh flour. Due to the high protein content of the samh seeds the nutritional value of the bread and cookies made with samh flour will be improved. The results of the sensory evaluation of the bread and cookies indicated that the bread made with samh flour upto 30% has similar characters except for the crumb color and the overall acceptability which were rated as significantly inferior. The sensory evaluation of the cookies showed that the cookies made with samh flour upto 100% were significantly superior (p<0.05) to the cookies made with 100% wheat flour (control).  相似文献   
803.
Three types of rice cultivars (indica, japonica and hybrid rice) with four levels of amylose were selected for assessing variability in starch digestibility. A vitro enzymatic starch digestion method was applied to estimate the glycemic index in vivo based on the kinetics of starch hydrolysis in vitro. The results indicated that significant differences in term of glycemic response were observed in three types of rice. Amylose content had an obviously impact on the estimated glycemic score (EGS) value and resistant starch (RS) content. The contents of RS were increased with the increasing amylose in the same type of rice. Japonica rice was significantly lower in RS content compared to indica rice and hybrid rice with similar amylose. The high amylose rice cultivar ZF201, which was characterized by low major RVA parameters, i.e. peak viscosity (PKV), hot paste viscosity (HPV) and cool paste viscosity (CPV), were obviously higher in RS content and lower in EGS. The retrogradation of cooked rice led to a reduction of HI and EGS of all varieties. Starch hydrolysis tends to be more quick and complete for the waxy and low amylose rice than for the intermediate and high amylose rice.  相似文献   
804.
Objective   To describe and evaluate the use of Alfaxan-CD ® as an intravenous anaesthetic in young cats.
Design   Thirty-five Domestic Short-hair cats aged from 3 to 12 months were admitted into the University Veterinary Teaching Hospital-Sydney for elective surgery. Anaesthesia was induced with Alfaxan-CD® and maintained with isoflurane: 22 cats received no premedication and 13 cats received acepromazine (0.03 mg/kg) and butorphanol (0.3 mg/kg) subcutaneously 30 min prior to induction.
Qualitative and quantitative data for induction and recovery were recorded. Physiological parameters were recorded at 0, 2 and 5 min post induction, and every 5 min thereafter until the end of the procedure.
Results   Intravenous injection of Alfaxan-CD® resulted in rapid induction of anaesthesia with a mean time to intubation of 122 s. The mean dose of Alfaxan-CD® used was 4.2 mg/kg in unpremedicated cats and 2.7 mg/kg in premedicated cats. All cats maintained a heart rate above 95 beats/min. No cat developed hypoxaemia. Hypercapnoea was detected in 4 cats and hypotension was observed in 18 cats. Time to extubation ranged from 1 to 9 min. The mean time to sternal recumbency for premedicated cats was 11 min; 77% of premedicated cats and 23% of unpremedicated cats had a recovery score of 1 or 2.
Conclusion   Alfaxan-CD® is an effective anaesthetic agent in young healthy cats, providing a smooth induction and rapid recovery. Cats that were premedicated with acepromazine and butorphanol prior to induction with Alfaxan-CD® had better recovery scores than those that were not premedicated.  相似文献   
805.
806.
Summary A multi-trait (MT) random regression (RR) test day (TD) model has been developed for genetic evaluation of somatic cell scores for Australian dairy cattle, where first, second and third lactations were considered as three different but correlated traits. The model includes herd-test-day, year-season, age at calving, heterosis and lactation curves modelled with Legendre polynomials as fixed effects, and random genetic and permanent environmental effects modelled with Legendre polynomials. Residual variance varied across the lactation trajectory. The genetic parameters were estimated using asreml . The heritability estimates ranged from 0.05 to 0.16. The genetic correlations between lactations and between test days within lactations were consistent with most of the published results. Preconditioned conjugate gradient algorithm with iteration on data was implemented for solving the system of equations. For reliability approximation, the method of Tier and Meyer was used. The genetic evaluation system was validated with Interbull validation method III by comparing proofs from a complete evaluation with those from an evaluation based on a data set excluding the most recent 4 years. The genetic trend estimate was in the allowed range and correlations between the two sets of proofs were very high. Additionally, the RR model was compared to the previous test day model. The correlations of proofs between both models were high (0.97) for bulls with high reliabilities. The correlations of bulls decreased with increasing incompleteness of daughter performance information. The correlations between the breeding values from two consecutive runs were high ranging from 0.97 to 0.99. The MT RR TD model was able to make effective use of available information on young bulls and cows, and could offer an opportunity to breeders to utilize estimated breeding values for first and later lactations.  相似文献   
807.
The objective of this study was to estimate variance and covariance components, in Iranian Cashmere goats, for birth weight (BWT) and weaning weight (WWT) performances of kids and total weight of kids weaned (TWW) per doe joined at first (TWW1), second (TWW2) and third (TWW3) parities by REML procedures using univariate and multivariate animal models. The analysis was based on 2313 records of kids and 940 records of does. Through ignoring or including maternal additive genetic or maternal permanent environmental effects, four different models were fitted for BWT and WWT performances. For TWW performances only two models (without or with service sire effect) were used. Models were compared using likelihood ratio test. Direct additive genetic and maternal permanent environmental effects had significant influence on BWT and WWT performances. These effects accounted for 9.4% and 15.6%, and 13.9% and 6.7% of phenotypic variation, respectively. No significant effect of service sire was observed on TWW. The estimates of heritabilities were 0.072, 0.109 and 0.082 for TWW1, TWW2 and TWW3, respectively. Direct genetic correlations among all performances were positive and low (for BWT with TWW) to high (for BWT with WWT and WWT with TWW). The corresponding estimates for phenotypic and residual correlations were moderate and lower than genetic correlations. The high genetic correlation among WWT and TWW suggests that direct selection on TWW1 or indirect selection on WWT would increase total weight of kids weaned per doe joined.  相似文献   
808.
为探讨雨生红球藻(Haematococcus pluvialis)对七彩神仙鱼(Symphysodon haraldi)增色效果以及对机体抗氧化力的影响,分别用添加0(对照组)、3.33、6.66、9.99、13.32和16.65 g/kg雨生红球藻(折算成虾青素添加量分别为0、100、200、300、400和500 mg/kg饲料)的饲料饲喂七彩神仙鱼6周,测定七彩神仙鱼皮肤、鳍条、肌肉和肝脏中的虾青素含量、体表的三刺激值和肝脏总抗氧化能力(T-AOC)和谷胱甘肽(GSH)含量。结果显示:饲料中添加雨生红球藻可以显著提高七彩神仙鱼的增重率,当添加量为9.99 g/kg其增重率最大。七彩神仙鱼皮肤、鳍条、肌肉和肝脏虾青素含量随着雨生红球藻添加量的增加而升高,当雨生红球藻添加量超过6.66 g/kg,各组织中虾青素的含量趋于稳定。随着雨生红球藻添加量增加,皮肤L*值(亮度)下降、而a*值(红度)和b*值(黄度)升高,皮肤中虾青素含量与三刺激值间的相关性均达到高度相关,并与a*值的相关性最高。随着雨生红球藻添加量的增加,七彩神仙鱼肝脏的T-AOC和GSH的含量也逐渐升高。结果表明,在饲料中添加雨生红球藻可提高七彩神仙鱼的增重率,提高七彩神仙鱼皮肤虾青素含量,改善七彩神仙鱼体色,增强机体的抗氧化能力;雨生红球藻的添加量建议为6.66~9.99 g/kg(虾青素含量为200~300 mg/kg)。  相似文献   
809.
采用反相高效液相色谱法,对海带"东方7号"3—7月的游离氨基酸和总氨基酸含量及氨基酸组成情况进行分析,并对总氨基酸中必需氨基酸进行评分。结果显示,3—7月,游离氨基酸的含量为9.78~37.59mg/g,在3—6月呈线性增加,7月略有降低;游离氨基酸的组成主要以呈味氨基酸为主(91.82%~98.53%),其中谷氨酸含量在游离氨基酸的季节变化中起决定性作用。总氨基酸的含量占海带质量的6.71%~9.38%,最大值出现在5月;总氨基酸的组成中,必需氨基酸含量随生长时间呈降低趋势,占总氨基酸含量的19.97%~42.94%。必需氨基酸评分最大值出现在5月,为68分。  相似文献   
810.
瞿若频  吴永常  张琳 《玉米科学》2024,32(2):168-175
基于黑龙江、辽宁、河北和山东4个省的372组调研数据,运用倾向得分匹配法和随机前沿模型得到玉米种植农户生产效率模型,依据最大似然检测判断不同规模玉米种植户的生产效率模型,分别估算农户生产效率模型和生产效率水平。结果表明,匹配前的大规模农户效率高于小规模农户,匹配后结果相反。以研究结论为基础,本文为难以改变或不愿意改变玉米种植面积的农户提供效率水平提升的参考依据和建议。  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