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   373篇
  免费   33篇
  国内免费   16篇
林业   11篇
农学   5篇
基础科学   2篇
  2篇
综合类   136篇
农作物   35篇
水产渔业   1篇
畜牧兽医   191篇
园艺   25篇
植物保护   14篇
  2024年   1篇
  2023年   1篇
  2022年   8篇
  2021年   16篇
  2020年   10篇
  2019年   13篇
  2018年   8篇
  2017年   14篇
  2016年   32篇
  2015年   24篇
  2014年   20篇
  2013年   25篇
  2012年   41篇
  2011年   45篇
  2010年   24篇
  2009年   23篇
  2008年   14篇
  2007年   10篇
  2006年   14篇
  2005年   10篇
  2004年   8篇
  2003年   7篇
  2002年   4篇
  2001年   4篇
  2000年   7篇
  1999年   3篇
  1998年   3篇
  1997年   2篇
  1996年   3篇
  1995年   2篇
  1994年   5篇
  1992年   2篇
  1991年   3篇
  1990年   2篇
  1989年   3篇
  1988年   1篇
  1987年   3篇
  1986年   1篇
  1985年   4篇
  1984年   1篇
  1983年   1篇
排序方式: 共有422条查询结果,搜索用时 15 毫秒
1.
AIM:To investigate the mechanism of depression and its development, and to study the expression of brain-derived neurotrophic factor (BDNF) in the hippocampus and prefrontal cortex of Wistar-Kyoto (WKY) rats treated with Jieyuwan. METHODS:Adult male WKY rats were used as an animal model of endogenous depression. Wistar rats of the same strain were selected as control group. WKY rats were randomly divided into model group, citalopram group and Jieyuwan group. After intragastric administration for 21 d, the changes of depression-like behaviors were observed by sucrose preference test and forced swimming test. Immunofluorescence and Western blot were used to detect the expression of BDNF in the hippocampus and prefrontal cortex. RESULTS:WKY rats showed significant depression-like behaviors, and the expression of BDNF was significantly decreased in the hippocampus and prefrontal cortex (P<0.01). The reduction of neuronal axons in hippocampus was also observed. After drug treatment, the depression-like behaviors of WKY rats were significantly attenuated, and the expression of BDNF and the number of axons were increased (P<0.01). CONCLUSION:Jieyuwan effectively attenuates the depression-like behaviors of WKY rats, and BDNF is a key factor in its antidepressant effect. Our findings further confirm the involvement of BDNF in the development of depression.  相似文献   
2.
Urban Norway rat (Rattus norvegicus) populations can carry the bacteria methicillin‐resistant Staphylococcus aureus (MRSA). There are numerous knowledge gaps in the epidemiology of MRSA in these populations that limit understanding of its ecology in urban environments. For example, fecal shedding of MRSA, which may increase environmental contamination, has been reported in other species; however, it is unknown whether Norway rats carry the bacteria rectally. Furthermore, while intermittent MRSA shedding has been shown in other species and may dictate when the risk of transmission is highest, duration of carriage has not been examined for Norway rats. Previous work has shown that lethal animal‐control methods may increase the level of pathogens within reservoir populations, possibly by disrupting ecological patterns. However, the impact of rodent‐control on potentially environmentally acquired pathogens like MRSA has not been tested. Using capture‐mark‐recapture methods in an inner‐city neighborhood in Vancouver, Canada, we show that rats intermittently carry MRSA both in the rectum and oropharynx. By assessing the prevalence of MRSA before and after enacting a pest‐control intervention, we report that kill‐trapping had no impact on the prevalence of carriage of this environmentally‐acquired agent.  相似文献   
3.
Undernutrition induces an increase of the oxidative stress that can predispose offspring to various diseases in adulthood through epigenetic reprogramming. The aim of this study was to evaluate the effects of intergenerational undernutrition on protein oxidation and antioxidant defence response on liver, heart and brain of the second‐generation neonates (F2) of undernourished rats. For this purpose, both parents in parental (F0) and first generation (F1) were fed with a low‐nutrient diet. Body mass and length decreased (p < 0.05) in F0, F1 and F2 being the F1 males who exhibited a greater mass loss. A decrease in plasma albumin concentration was observed in F2 neonates (p < 0.05) and also a mass loss of liver, heart and brain (p < 0.05), although proportionally to body length reduction. Undernutrition increased levels of protein oxidation in liver and heart (p < 0.05) but not in brain (p > 0.05) while catalase activity increased only in brain (p < 0.05). In summary, intergenerational undernutrition modifies the antioxidant status through an organ‐specific response, on F2 neonate rats, where the brain increased catalase activity to prevent a severe oxidative damage and support the vital functions of this key organ to maintain vital functions.  相似文献   
4.
目的 探讨加味生脉补心丹(以下简称BXD)对自发性非肥胖2型糖尿病Goto-kakisaki (GK)大鼠心肌损伤的保护作用。方法 8~9周龄雄性Wistar大鼠8只作为空白组,另将40只糖尿病模型GK大鼠按随机数字表将大鼠分为5组,分别为:模型组、西药组(格列齐特缓释片组)、BXD低剂量组、BXD中剂量组、BXD高剂量组。各组大鼠按治疗方法给药10周后处死,腹主动脉采血检测空腹血糖(FPG)、糖化血红蛋白(HbAlc)、超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)、丙二醛(MDA),取左心室行心肌组织HE染色、PAS染色观察病理改变,免疫组化测定心肌凋亡相关蛋白Bax、Bcl-2的表达。结果 与空白组比较,模型组FPG、HbAlc显著升高(P<0.01),SOD、GSH-Px均显著降低(P<0.01),MDA显著升高(P<0.01);HE染色可见心肌组织水肿坏死、纤维溶解断裂;PAS染色可见大量糖原物质沉积;免疫组化示心肌组织Bax表达增多、Bcl-2表达减少(P<0.01)。与模型组比较,BXD低剂量组FPG降低(P<0.05),西药组和BXD中、高剂量组FPG均显著降低(P<0.01);西药组HbAlc显著降低(P<0.01),BXD高剂量组HbAlc降低(P<0.05);西药组与BXD高剂量组SOD、GSH-Px均显著升高(P<0.01)、MDA含量均降低(P<0.05);西药组、BXD高剂量组Bax表达显著减少(P<0.01),西药组及BXD中剂量组、高剂量组Bcl-2表达显著增多(P<0.01)。结论 BXD对GK大鼠心肌损伤具有保护作用,其机制可能是通过增强抗氧化能力、抑制心肌细胞凋亡,从而起到心肌保护作用。  相似文献   
5.
李雪  张玮琛 《勤云标准版测试》2019,39(11):1331-1335
目的 探讨加味大柴胡汤在临床上辅助治疗老年阻塞性黄疸的理论机制。方法 通过结扎胆总管的外科手术方法建立阻塞性黄疸老年大鼠模型,实验分为假手术组、模型组、加味大柴胡汤组,予以相应干预,分3、7、10 d共3个时间段,每组10只SPF级老年SD大鼠,在各时间段取老年大鼠肝组织及心脏血,检测AST、ALT及TBA;采用钙离子试剂盒检测老年鼠肝组织匀浆钙离子浓度;采用Western Blot法检测老年鼠肝组织TRPC1蛋白的表达,采用Tunel法观察肝细胞凋亡情况。结果 造模成功后各时间点模型组、加味大柴胡汤组与假手术组比较,ALT、AST、TBA和Ca2+浓度均升高,且模型组上升更明显(P<0.01),模型组、加味大柴胡汤组的TRPC1的蛋白含量也均高于假手术组(P<0.01),且加味大柴胡汤组肝细胞的凋亡率低于模型组(P<0.01)。结论 梗阻性黄疸老年大鼠TRPC1表达明显升高,加味大柴胡汤下调TRPC1的表达,可能是其降低钙超载,减少肝细胞凋亡的机制之一。  相似文献   
6.
Rat‐associated zoonoses transmitted through faeces or urine are of particular concern for public health because environmental exposure in homes and businesses may be frequent and undetected. To identify times and locations with greater public health risks from rats, we investigated whether rat characteristics, environmental features, socioeconomic factors, or season could predict rat infection risk across diverse urban neighbourhoods. In partnership with a pest management company, we sampled rats in 13 community areas along an income gradient in Chicago, a large city where concern about rats has increased in recent years. We collected kidneys for Leptospira spp. testing and colon contents for aerobic bacteria such as Salmonella spp. and Escherichia coli. Of 202 sampled rats, 5% carried Leptospira spp. and 22% carried E. coli. Rats were significantly more likely to carry Leptospira spp. on blocks with more standing water complaints in higher‐income neighbourhoods (OR = 6.74, 95% CI: 1.54–29.39). Rats were significantly more likely to carry E. coli on blocks with more food vendors (OR = 9.94, 2.27–43.50) particularly in low‐income neighbourhoods (OR = 0.26, 0.09–0.82) and in the spring (OR = 15.96, 2.90–88.62). We detected a high diversity of E. coli serovars but none contained major virulence factors. These associations between environmental features related to sanitation and infection risk in rats support transmission through water for Leptospira spp. and faecal–oral transmission for E. coli. We also found opposing relationships between zoonotic infection risk and income for these two pathogens. Thus, our results highlight the importance of sanitation for predicting zoonotic disease risks and including diverse urban areas in pathogen surveillance to mitigate public health risks from rats.  相似文献   
7.
目的比较观察过氧化氢和甲醛对SPF级大鼠和小鼠繁殖室内表面、台面以及空气的消毒效果,选择消毒效果良好的消毒剂。方法采用空气落下菌检测法和表面细菌拭子检测法,对过氧化氢和甲醛熏蒸SPF级大鼠和小鼠繁殖室的消毒效果进行检测观察。结果SPF级大鼠和小鼠繁殖室分别经过氧化氢和甲醛熏蒸消毒后,进行空气落下菌的检测,过氧化氢和甲醛对大鼠繁殖室和小鼠繁殖室空气的杀菌率分别为100%、97.5%和100%、100%;将墙壁、地面和笼架表面的菌落数进行检测,过氧化氢和甲醛对大鼠繁殖室墙壁、地面和笼架的杀菌率分别为100%、99%、100%和95%、100%、99%,对小鼠繁殖室墙壁、地面和笼架的杀菌率均为100%。结论过氧化氢蒸汽消毒是比较理想的消毒方法,很好地控制了SPF级大鼠和小鼠繁殖室环境微生物,安全性高且消毒效果明显。  相似文献   
8.
本试验旨在建立阿司匹林诱导的大鼠肠道损伤模型。试验采用单因素试验设计,选用6周龄SD大鼠18只,经过7 d的适应性饲养后随机分为3个组,每组6只,单笼饲喂。模型1组和模型2组阿司匹林的灌胃剂量分别为50和200 mg/kg,空白对照组灌胃等量生理盐水,持续灌胃14 d。结果表明:与空白对照组相比,灌服50 mg/kg阿司匹林显著降低了大鼠的体增重、血清白细胞介素-2(IL⁃2)含量、肠道黏膜分泌性免疫球蛋白A(sIgA)含量、肠道绒毛高度和绒毛高度与隐窝深度的比值(P<0.05),但对肝脏指数、脾脏指数和血清溶菌酶(LZM)活性没有显著影响(P>0.05);灌服200 mg/kg阿司匹林显著降低了大鼠的体增重、肝脏指数、血清IL⁃2含量与LZM活性、肠道黏膜sIgA含量、肠道绒毛高度和隐窝深度及二者的比值(P<0.05)。在本试验条件下,采用200 mg/kg剂量的阿司匹林连续灌胃14 d可以成功建立大鼠的肠道损伤模型。  相似文献   
9.
目的观察5年生种植人参食用对成年大鼠糖脂代谢及下丘脑-垂体-甲状腺轴功能变化的影响,探讨人参食用对机体内分泌系统功能的调节作用。方法正常成年Wistar大鼠随机分为10组,即:对照组,5年生种植人参原粉小、中、大剂量(0.25、0.5、1.0g生药/kg)组,5年生种植人参水提物小、中、大剂量(0.25、0.5、1.0g生药/kg)组,5年生种植人参醇提物小、中、大剂量(0.25、0.5、1.0g生药/kg)组,每组14只。各组大鼠连续灌胃给药3个月,观察糖脂代谢及下丘脑-垂体-甲状腺轴功能变化。结果与对照组比较,人参醇提物中、大剂量组可使正常成年大鼠血糖明显降低(P0.05或P0.01),人参原粉及人参醇提物中、大剂量组均可使正常成年大鼠TG明显降低(P0.05或P0.01),人参水提物中剂量组可使正常成年大鼠T4明显降低(P0.05),人参原粉、人参水提物及人参醇提物各剂量组对正常成年大鼠甲状腺脏器系数及血清中CHO、TSH、T3含量均无明显影响(P0.05)。结论人参醇提物对正常成年大鼠具有糖脂代谢调节作用;人参原粉及人参水提物对正常成年大鼠的糖脂代谢及下丘脑-垂体-甲状腺轴无明显影响。  相似文献   
10.
【目的】探讨阴地厥提取物(Scepteridium ternatumextract,STE)对运动训练大鼠心、肝、肾、脑、股四头肌等组织抗氧化水平的影响。【方法】将24只SD雄性大鼠随机分为安静对照组、运动对照组及运动+STE组,后2组大鼠进行7周的大强度跑台耐力训练,安静对照组自由活动不进行跑台训练,运动+STE组大鼠每天灌胃STE100mg/kg,其他2组灌服相同体积的生理盐水,每周最后1天测各组大鼠的体质量。第8周第1天取运动对照组和运动+STE组大鼠心、肝、肾、脑、股四头肌等组织样品,匀浆后分别测试各组大鼠不同组织总抗氧化能力(T-AOC)及超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-Px)活性和丙二醛(MDA)、还原型谷胱甘肽(GSH)含量。【结果】运动+STE组和运动对照组大鼠体质量与安静对照组比较均呈下降的趋势,其中运动+STE组大鼠体质量变化无显著性差异(P0.05),而运动对照组大鼠体质量变化有显著性差异(P0.05)。运动+STE组大鼠各组织T-AOC、SOD、CAT、GSH-Px活性和GSH含量显著或极显著高于运动对照组。运动+STE组大鼠各组织(除脑组织外)MDA含量显著低于运动对照组(P0.05),而高于安静对照组。【结论】阴地厥提取物可以改善长时间大强度耐力运动大鼠心、肝、肾、脑、股四头肌等组织的抗氧化水平,维持各组织抗氧酶活性和GSH含量,降低脂质过氧化反应,减少MDA的生成。  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