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   260篇
  免费   35篇
  国内免费   29篇
林业   20篇
农学   9篇
基础科学   1篇
  17篇
综合类   72篇
农作物   9篇
水产渔业   6篇
畜牧兽医   175篇
园艺   4篇
植物保护   11篇
  2024年   1篇
  2023年   6篇
  2022年   12篇
  2021年   10篇
  2020年   8篇
  2019年   16篇
  2018年   21篇
  2017年   26篇
  2016年   13篇
  2015年   13篇
  2014年   9篇
  2013年   18篇
  2012年   13篇
  2011年   10篇
  2010年   11篇
  2009年   17篇
  2008年   10篇
  2007年   20篇
  2006年   10篇
  2005年   14篇
  2004年   5篇
  2003年   13篇
  2002年   8篇
  2001年   5篇
  2000年   3篇
  1999年   2篇
  1998年   8篇
  1997年   3篇
  1996年   3篇
  1995年   2篇
  1994年   1篇
  1993年   4篇
  1992年   3篇
  1990年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1956年   1篇
排序方式: 共有324条查询结果,搜索用时 15 毫秒
111.
【目的】研究蓝刺头花絮水提物的降血糖作用。【方法】采用煎煮法制备蓝刺头花絮水提物。使用四氧嘧啶诱导糖尿病小鼠模型,并随机分为4组,每组10只,蓝刺头高、中、低剂量组小鼠每天分别灌胃1.00,0.50和0.25g/mL的蓝刺头花絮水提物,对照组灌等量蒸馏水,于试验0,7,14和21d测定糖尿病小鼠空腹血糖、体质量;21d测定小鼠口服糖耐量、肝糖原、血清胰岛素、胰高血糖素及肾上腺素的含量。【结果】蓝刺头花絮水提物能够显著降低糖尿病小鼠的空腹血糖,改善糖尿病小鼠的口服糖耐量,升高肝糖原及血清胰岛素水平,极显著降低血清肾上腺素含量,对体质量和血清胰高血糖素含量无显著影响。【结论】蓝刺头花絮水提物能够降低糖尿病小鼠的血糖水平,且呈剂量依赖关系。  相似文献   
112.
113.
腐殖酸液浸苗对匙叶翼首草产量和品质的影响   总被引:1,自引:0,他引:1  
基于腐殖酸液肥在烤烟、冬小麦等农作物及辣椒等蔬菜生产的良好表现,为了拓宽该肥料的使用范围,采用单因素随机区组设计,研究了腐殖酸液肥浸苗对匙叶翼首草产量和品质的影响。结果表明:匙叶翼首草用不同浓度的腐殖酸液肥浸苗后移栽可以显著提高其产量,且0.6%腐殖酸溶液浸苗处理产量最高,较对照增产25.06%,还可以显著提高匙叶翼首草中的糖含量,同时降低灰分含量。腐殖酸液浓度增大到0.8%时不但产量降低,而且匙叶翼首草的品质也降低了。  相似文献   
114.
Hydromorphone (H) may be an effective analgesic agent in cats, but fear of negative behavioral side‐effects associated with opioids is cited as a reason for avoiding this class of analgesics in cats. This study was designed to assess onset and duration of antinociception using an established feline thermal threshold model in cats, given an accepted clinical dose of 0.1 mg kg?1 of H. In addition, cats were observed for changes in behavior and other side‐effects. Six adult cats from an established colony (four spayed females and two castrated males, 4.7–7.0 kg) received 0.1 mg kg?1 H IV following establishment of baseline thermal threshold (TT) values. TT was tested at 15 minutes post‐injection, then at every 30–60 minutes for 12 hours. Side‐effects and behavior changes were recorded for 12 hours. Changes in TT over time were analyzed using a one‐way anova ; a p‐value <0.05 was considered significant. TT increased from a pre‐treatment value of (mean ± SD) 40.9 ± 1.65 °C to instrument cutout (55.5 °C) within 30 minutes for 5/6 cats. Mean TT was significantly elevated above baseline from 15 to 450 minutes after treatment. There was a significant increase in skin temperature from 15 to 300 minutes with peak increase of 1.55 °C at 135 minutes. Side‐effects included mydriasis (6/6) and nausea (4/6), characterized by licking, foaming, and gagging. Mydriasis occurred within 10–30 seconds of injection and persisted for 5–7 hours. Nausea was noted within 2 minutes of injection and persisted for 30–90 minutes; no vomiting occurred. Commonly observed behavioral changes included ventral tail curl (6/6 cats, onset 5–45 minutes, duration 4–5 hours) and euphoria (5/6 cats, onset <6 minutes for 4/6, duration 1–6 hours). 2/6 cats were profoundly sedate. Three cats showed signs of dysphoria with or without increased motor activity with variable onset and duration. Dysphoric behavior included staring, pacing, vocalizing, and sudden movements. 3/6 cats exhibited both euphoria and dysphoria at different times during the study. At no time were cats difficult to restrain or work with. Return to baseline behavior occurred 7–8.5 hours post‐injection. Mydriasis did not correlate closely with antinociception. Signs of sedation and euphoria corresponded with onset of antinociception, but not duration. Tail curl signs correlated with antinociception. In this model, H proved to be a rapid acting, potent, analgesic with a long (7.5 hours) duration of action. The most common behavioral changes noted were ventral tail curl, euphoria, and sedation. Mydriasis and nausea were noted as side‐effects.  相似文献   
115.
116.
117.
Experiments were conducted with 270 Abore Acre male broilers to study the influence of dietary chlortetracycline (CTC) on the bursal, thymus and spleen weight index and T, B cell proliferation and antibody responses of broilers. Results show that 50mg/kg CTC had no significant inhibitory effect on thymus and spleen weight index, and T, B cell proliferation of broilers at 21 days old. 150mg/kg CTC had significant inhibitory effect on bursal, thymus and spleen, and T, B cell proliferation (P<0.05). Dietary CTC had a direct inhibitory effect on lymphocyte proliferation in vitro. 50mg/kg and 150mg/kg CTC had a significant inhibitory effect on the antibody responses to BSA (P<0.01). Results demonstrated that subtherapeutic and long term CTC had significant inhibitory effects on immune organs and antibody response. The immunosuppressant effect became higher when the level of CTC increased. 150mg/kg CTC increased the growth rate of broilers significantly.  相似文献   
118.
本文旨在研究以葡萄糖氧化酶和酵母硒为主要成分的混合添加剂,在规模化养殖条件下,对肉鸡生产性能、免疫器官指数和血清蛋白指标的影响。将5 000只1日龄爱拔益加(AA)肉鸡,随机分为2个组,分别为对照组和试验组,每个组设4个重复,每个重复625只鸡。对照组饲喂玉米-豆粕基础饲粮,试验组饲喂基础饲粮+0.2%混合添加剂(葡萄糖氧化酶和酵母硒)。试验期为42 d。结果表明,1)生产性能:在肉鸡不同日龄阶段(1~21日龄、22~42日龄和1~42日龄),试验组的平均日采食量(ADFI)、平均日增重(ADG)均显著高于对照组(P0.05),ADFI分别提高了2.58%、1.55%和1.83%,ADG分别提高了1.67%、6.93%和6.66%;试验组料重比(F/G)显著低于对照组(P0.05),分别降低了3.36%、5.13%和4.44%。在肉鸡生长全期(1~42日龄),试验组肉鸡死亡率显著低于对照组(P0.05)。2)屠宰性能:21日龄试验组肉鸡屠宰率、全净膛率、半净膛率显著高于对照组(P0.05),分别提高2.35%、4.11%和3.23%,42日龄肉鸡屠宰指标在试验组与对照组之间无显著差异(P0.05)。3)免疫器官指数:21日龄时,试验组肉鸡法氏囊指数显著高于对照组(P0.05),脾脏指数和胸腺指数在2组之间无显著差异(P0.05);42日龄时,试验组肉鸡胸腺指数显著高于对照组(P0.05),脾脏指数和法氏囊指数略有提高(P0.05)。4)血清指标:21日龄时,试验组肉鸡血清总蛋白含量显著高于对照组(P0.05);42日龄时,试验组肉鸡血清球蛋白含量显著高于对照组(P0.05)。在肉鸡21、42日龄时,试验组血清尿素氮含量显著低于对照组(P0.05)。综上,肉鸡饲粮使用含葡萄糖氧化酶和酵母硒的混合添加剂,能够提高肉鸡生产性能,降低死亡率,提高免疫器官指数和降低血清尿素氮含量。  相似文献   
119.
基于内蒙古草原牧区2011~2013年两个积雪季的国产卫星FY-3B双极化亮温数据,通过使用2012年MODIS的MCD12Q1土地覆盖类型产品数据提取内蒙古牧区草地植被类型,同时使用与FY-3B数据同期的MOD10A1日积雪覆盖产品剔除研究区内无积雪覆盖的像元,进而得到内蒙古草原牧区有积雪覆盖区域的FY-3B影像各像元的亮温数据。将亮温数据与研究区内相应的野外固定实验站观测数据及呼伦贝尔市的7个气象站点雪深观测数据建立回归拟合关系,初步建立了基于FY-3B亮温数据的适合于内蒙古草原牧区的雪深反演模型,模型参数拟合决定系数R2为0.59。使用2012年研究区雪深观测值检验模型,均方根误差为3.12cm,平均相对误差为18%,表明所建立的雪深反演模型能够较好地估算和识别内蒙古草原牧区雪深的空间分布特征。  相似文献   
120.
Background: Metabolic profile was initially designed as a presymptomatic diagnostic aid based on statistical analyses of blood metabolites to provide an early warning of certain types of metabolic disorder. However, there is little metabolic profile data available about Korean Hanwoo cows. Therefore, this study aimed to determine the reference intervals of metabolic profile for Korean Hanwoo cows.Methods: Healthy animals(2,205) were selected and divided into early(day 1 to 95), middle(day 96 to 190) and late(day 191 to 285) period according to their gestating period. Metabolic profile including total protein(TP), albumin(Alb), urea(UREA), glucose(Glu), total cholesterol(T-Cho), long-chain fatty acid(LCFA), aspartate aminotransferase(AST),gamma-glutamyl transpeptidase(GGT), creatinine(Crea), calcium(Ca), inorganic phosphorous(i P) and magnesium(Mg)were analyzed using a TBA-40 FR automatic biochemical analyzer. The data of Korean Hanwoo cows were then compared to those of the Japanese Wagyu cows.Results: Most of the data of the Korean Hanwoo cows were relatively higher than those of Japanese Wagyu cows, with the exception of Glu and GGT. This may indicate that the nutritional level of feed for the Korean Hanwoo cows was higher than that of the Japanese Wagyu cows because of the different feeding system. In particular, relatively higher levels of UREA and LCFA were observed in the Korean Hanwoo cows, and this may also contribute to the low reproduction efficiency.Conclusions: These findings may provide some theoretical basis for understanding the reproductive and feeding situation of Korean Hanwoo cows.  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