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   9844篇
  免费   530篇
  国内免费   908篇
林业   552篇
农学   551篇
基础科学   443篇
  1026篇
综合类   4681篇
农作物   496篇
水产渔业   399篇
畜牧兽医   1850篇
园艺   781篇
植物保护   503篇
  2024年   96篇
  2023年   255篇
  2022年   571篇
  2021年   511篇
  2020年   462篇
  2019年   427篇
  2018年   328篇
  2017年   488篇
  2016年   342篇
  2015年   462篇
  2014年   501篇
  2013年   604篇
  2012年   756篇
  2011年   854篇
  2010年   812篇
  2009年   705篇
  2008年   718篇
  2007年   578篇
  2006年   464篇
  2005年   414篇
  2004年   273篇
  2003年   162篇
  2002年   157篇
  2001年   133篇
  2000年   135篇
  1999年   56篇
  1998年   2篇
  1997年   1篇
  1995年   1篇
  1994年   1篇
  1992年   1篇
  1990年   1篇
  1987年   1篇
  1986年   1篇
  1981年   4篇
  1962年   2篇
  1956年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
AIM: To examine the effects of L-carnitine on apoptosis and oxidant injury in cultured neonatal rat cardiomyocytes induced by hypoxia/reoxygenation and its possible mechanism. METHODS: The cultured cardiomyocytes were divided into three groups, control, A/R group (anoxia for 120 min, reoxygenation for 240 min) and L-carnitine treatment group, in which cells were exposed to 20 mg/L, 50 mg/L, 100 mg/L, 200 mg/L L-carnitine respectively at 2 h before anoxia. The superoxide dismutase (SOD), succinate dehydrogenase (SDH) activities and malondialdehyde (MDA) content were examined, and the apoptosis was determined by flow of cytometry (FCM). In addition, the ultrastructure was observed by transmission electron microscopy. RESULTS: In A/R group, SOD and SDH activities were lower, the apoptosis rate and MDA content were higher than those in control group (P<0.05). In L-carnitine treatment group, SOD and SDH activities were higher, the apoptosis rate and MDA content were lower than those in A/R group, a L-carnitine concentration-dependent effect was found. Moreover, impairment of myocardial ultrastructure was more severe in A/R group than L-carnitine treatment group. CONCLUSION: L-carnitine can protect cardiomyocytes against hypoxia/reoxygenation-induced injury in a dose-dependent manner.  相似文献   
142.
AIM: To detect the effects of NK cells on the etiology of severe pre-eclampsia. METHODS: The peripheral blood and umbilical blood from severe pre-eclamptic patients and normal late pregnant women were collected. NK cells were seperated in percoll and counted by SAP. The proliferating ability of NK cells was measured by MTT and killing power of NK cells was determined by [51Cr] releasing test. The immunohistochemistry method was used to detect the quantity of NK cells and the expression of HLA-G in placenta of them. RESULTS: (1) Compared with that in normal late pregnant women, the counts of the NK cells in peripheral blood, umbilical blood and decidua of severe pre-eclamptic patients were significantly higher (all P<0.05). (2) Compared with that in normal late pregnant women, proliferating and killing ability of NK cells in peripheral blood and umbilical blood of severe pre-eclamptic patients were significantly higher. (3) The expression of HLA-G protein in placenta of severe pre-eclampsia group was lower than that in normal group (P<0.05). CONCLUSION: The quantity of NK cells in severe pre-eclamptic patients is increased with stronger biologic function. They may be related with the pathogenesis of severe pre-eclampsia.  相似文献   
143.
AIM: To study the effects of intrathymic inoculation of liver specific antigen (LSA) on hepatocyte apoptosis after liver allotransplantation. METHODS: Orthotopic liver transplantation was used in this study. Group Ⅰ: syngenic control (Wistar-to-Wistar); Group Ⅱ: acute rejection (SD-to-Wistar); Group Ⅲ: thymus inoculation of SD rat LSA day 7 before transplantation. The observation of general situation and survival time, hepatocyte apoptosis and LAT expression in liver transplants were used to analyze immune state of animals in different groups. RESULTS: The general situation of group Ⅰ was very well after transplantation. Recipients of groupⅡ lost body weight progressively and all died within day 9 to day 13 post transplantation. As for group Ⅲ, the general situation of recipients was remarkably better than that in group Ⅱ. The positive cells of apoptosis in group Ⅲ detected by TUNEL were not significantly different from that in group Ⅰ, but was significantly lower than that in group Ⅱ. LAT was detected at any time in group Ⅱ with peak expression at day 5 and day 7 post transplantation. In contrast, LAT was not detected in any other groups. CONCLUSION: Intrathymic inoculation of LSA protects hepatocytes from apoptosis after liver allotransplantation.  相似文献   
144.
为了在负对照组 (钙、磷水平各减少 0 .1 % )日粮基础上添加植酸酶对肉鸭生长、钙、磷表观存留率的影响 ,用 64只 1日龄樱桃谷鸭进行试验 ,按体重随机分为 4组 ,代谢期 6天。试验组鸭分别添加植酸酶 30 0和 50 0PU/kg。结果表明 :添加植酸酶显著提高试鸭的日采食量、日增重、钙、磷的表观存留率 ,植酸酶可以部分替代磷酸氢钙  相似文献   
145.
营养因素对家禽免疫具有重要作用。脂肪是家禽必需的重要营养元素之一,不仅是维持家禽正常生长、繁殖、生产不可缺少的组成成分与营养物质,也是调节家禽免疫器官、组织和免疫应答反应不可缺少的物质基础。作者从脂肪的生理营养功能,就其对家禽的免疫器官发育、体液免疫、细胞免疫、非特异性免疫、细胞因子产生的影响等方面进行了综述。为合理配制家禽日粮,提高家禽抵抗疾病的能力提供理论依据。  相似文献   
146.
猪附红细胞体可溶性抗原的分析   总被引:2,自引:0,他引:2  
为了解附红细胞体可溶性抗原的特性,本试验对解离下的猪附红细胞体,经超声波裂解制备粗抗原,再经SephadexG-200分离提纯后,应用对流免疫电泳(CIEP)定位特异性抗原蛋白峰,再进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)及免疫印迹(Westernblot),对猪附红细胞体粗提及纯化的可溶性抗原进行了分析。结果表明,猪附红细胞体可溶性抗原的电泳图谱上有四条蛋白带,其分子量分别为77Ku、62Ku、58Ku、29Ku,其中特异性抗原分子量为58Ku和29Ku。从而为附红细胞体抗原成分的进一步分析及该病的免疫学诊断等研究奠定了基础。  相似文献   
147.
油橄榄种质资源研究进展   总被引:1,自引:0,他引:1  
油橄榄高度杂合,种质资源丰富,其分类学、遗传学关系、系统发生学关系等很模糊。这给品种的培育和基因资源的管理,带来了诸多不便。现就国内外发表的关于由于油橄榄种质资源的研究做一综述。望能为以后油橄榄的种质资源的研究提供参考。  相似文献   
148.
AIM: To investigate the effects of constant magnetic field on apoptosis, secretion and expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) in human umbilical vein endothelial cells (HUVEC), and their adhesion rates with THP-1 monocytes induced by angiotensin Ⅱ (AngⅡ).METHODS: The third passage of cultured HUVEC was used.There were six groups: control group, Ang Ⅱ (10-6 mol/L) group, Ang Ⅱ with 1, 5, 10 or 20 gausses of constant magnetic field group.Samples were collected 24 h after incubation with or without magnetic field.Apoptosis was determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and propidinm iodide staining with flow cytometry.Secretion and expression of ICAM-1 and VCAM-1 were detected by ELISA and immunocytochemistry, respectively.Adhesion rate between HUVEC and THP-1 was measured by counting method.RESULTS: Ang Ⅱ at concentration of 10-6mol/L induced apoptosis in HUVECs (P<0.05 vs control), whereas in 1, 5, 10 and 20 gausses group, apoptosis of HUVECs was significantly lower than that in Ang Ⅱ group (P<0.05).Ang Ⅱ at concentration of 10-6 mol/L significantly increased secretion and expression of ICAM-1 and VCAM-1 (P<0.05 vs control), whereas secretion and expression of ICAM-1 and VCAM-1 in 1, 5, 10 and 20 gausses group significantly decreased, compared with Ang Ⅱ group (P<0.05).The adhesion rates between HUVEC and THP-1 significantly increased 24 h after incubation of HUVEC with Ang Ⅱ (P<0.05 vs control), in contrast, the adhesion rates between HUVEC and THP-1 in 1, 5, 10 and 20 gausses group significantly decreased, compaed with Ang Ⅱ group (P<0.05).CONCLUSIONS: One gauss to 20 gausses of constant magnetic field antagonizes the effects of Ang Ⅱ on HUVEC, decreases apoptosis and expression of ICAM-1 and VCAM-1 in HUVEC, and also decreases the adhesion rates between HUVEC and monocytes induced by Ang Ⅱ.  相似文献   
149.
安业8号是山东省邹平县安业农作物研究所选育的中熟、花皮、大果型一代杂交西瓜新品种。全生育期约100d,果实发育期33d;具有果个大、花皮韧、易坐果、品质优、抗性强、适应范围较广等突出特点。  相似文献   
150.
披碱草野生种质材料芽期耐盐性研究   总被引:2,自引:1,他引:2  
通过对20份来自不同地区的披碱草野生种质材料在0、0.4%、0.6%、0.8%、1.0%浓度盐胁迫下的相对发芽率、相对发芽势、致死浓度等指标的综合评价,筛选出耐盐材料4份(G8、G17、G18、G19),分别来自甘肃古浪县、山西沁源、甘肃古浪县、山西五台山;敏盐材料3份(G2、G3、G5),分别来自北京百花山、北京灵山、新疆吉阜康白杨沟;其他为中等耐盐材料。  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