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   11335篇
  免费   747篇
  国内免费   870篇
林业   871篇
农学   630篇
基础科学   431篇
  892篇
综合类   5713篇
农作物   787篇
水产渔业   363篇
畜牧兽医   1968篇
园艺   927篇
植物保护   370篇
  2024年   51篇
  2023年   206篇
  2022年   485篇
  2021年   503篇
  2020年   495篇
  2019年   460篇
  2018年   296篇
  2017年   568篇
  2016年   367篇
  2015年   579篇
  2014年   568篇
  2013年   723篇
  2012年   985篇
  2011年   1018篇
  2010年   893篇
  2009年   827篇
  2008年   814篇
  2007年   762篇
  2006年   685篇
  2005年   559篇
  2004年   305篇
  2003年   179篇
  2002年   179篇
  2001年   170篇
  2000年   166篇
  1999年   52篇
  1998年   8篇
  1997年   1篇
  1996年   1篇
  1995年   4篇
  1994年   5篇
  1992年   8篇
  1991年   5篇
  1990年   4篇
  1989年   1篇
  1988年   3篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
  1981年   2篇
  1962年   1篇
  1956年   7篇
  1955年   2篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
AIM: To prepare gfp-bcl-XL-contained recombinant adenovirus(rAd-gfp-bcl-XL).METHODS: Bcl-XL gene was amplified from pEGFP-C3-bcl-XL, subcloned into shuttle plasmid and formed transfer plasmid of pAdTrack-CMV-bcl-XL. Then pAdTrack-CMV-bcl-XL was linealinzed with PmeI and co-transformed into BJ5183 bacteria with adenovirus genomic plasmid of pAdEasy-1. The identified recombinant adenovirus plasmid was digested with PacI and transfected into 293 cells to package recombinant adenovirus particles. The target gene was detected by PCR.RESULTS: There were about 35% positive recombinant bacterial clones after the co-transformation of pAdTrack-CMV-bcl-XL and pAdEasy-1 into BJ5183. Recombinant adenovirus particle were produced and further amplified after the transfection of pAdEasy-1-gfp-bcl-XL into 293 cells. PCR test indicated that the recombinant Ad contained bcl-XL gene. The titer of the purified rAd-gfp-bcl-XL was 6.5×1012 PFU/L. CONCLUSIONS: The homologous recombination in bacteria is a convenient and high efficient method to prepare rAd-gfp-bcl-XL. This affords a good gene transfer vector for the gene therapy in human’s diseases.  相似文献   
32.
AIM: To explore the effects of riboflavin and ascorbic acid on the apoptosis induced by deoxynivalenol(DON) in mouse thymocytes. METHODS: The effects of riboflavin and ascorbic acid on the apoptosis and proliferation inhibition of thymocytes induced by DON in KM mice were studied with animal experiment, DNA agarose gel electrophoresis and flow cytometric DNA content analysis. RESULTS: Apoptosis rate of thymocytes in DON (4 mg/kg) treated group was13.73%±15.3% The percentages of apoptosis in riboflavin (1.25 mg/kg-10mg/kg) and ascorbic acid (25 mg/kg-100mg/kg) pretreated thymocytes groups were significantly lower than that in DON group (P <0.05). The result of DNA agarose gel electrophoresis showed that the characteristic ladder pattern of apoptosis was found in DON-treated thymocytes, but not in control and riboflavin pretreatment and ascorbic acid pretreatment groups The significant differences in proliferation index were not found among DON-treated thymocytes and riboflavin and ascorbic acid-pretreated thymocytes CONCLUSION: Pretreatment with riboflavin and ascorbic acid inhibit apoptosis of mouse thymocytes induced by DON in certain extent and have no effect on proliferation inhibition by DON.  相似文献   
33.
AIM: To probe into the genetic susceptibility of HLA-DRB1 alleles to esophageal neoplasm in Hubei Han Chinese. METHODS: HLA-DRB1 gene polymorphism in 42 patients with esophageal neoplasm and 136 normal control subjects was studied by PCR and sequence. RESULTS: Allele frequency of HLA-DRB1 *0901 allele was significantly higher in esophageal cancer patients than those in normal controls(0.2500 vs 0.1397, P =0.028; the odds ratiO2.053; etiologic fraction 0.1282).There were no association between the rested HLA-DRB1 alleles with patients. CONCLUSION: Individuals carrying HLA-DRB1 *0901 may be susceptible to esophagealo carcinoma, its nucleotide sepuence approachs to the corresponded allele sequence(exoN2)published in GenBank.  相似文献   
34.
达县分葱田甜菜夜蛾发生规律初步研究   总被引:5,自引:2,他引:5  
采用系统调查方法研究了达县地区分葱田甜菜夜蛾的生活史、发生与环境的关系。甜菜夜蛾在达县分葱田1a发生6代,以三至五代为害最重,世代重叠。其数量消长与虫源、夏秋季气候、天敌、栽培管理等因素密切相关。通过调查分析提出本县初始虫源非本地虫源。  相似文献   
35.
红汁乳菇多糖提取最佳工艺研究   总被引:10,自引:0,他引:10  
对红汁乳菇多糖提取、纯化工艺进行了优化研究,结果表明在料液比1:30,浸提温度95%浸提时间2h,pH8.0,可获得最佳提取效果。在醇析浓度为70%,V(氯仿):V(正丁醇)=1:0.2,V(氯仿 正丁醇):V(样品)=1:l时,纯化含量为58%。同时用超声波法对红汁乳菇多糖的提取作了研究,其得率为6.99%,效果较佳。  相似文献   
36.
鸡腿蘑菌丝体的同工酶研究   总被引:7,自引:1,他引:7  
用8种不同培养基配方,培养鸡腿蘑菌丝体,其同工酶分析结果表明,鸡腿蘑菌丝体酯酶(EST)同工酶谱差异明显,过氧化物酶(POD)同工酶谱差异明显。  相似文献   
37.
鸡球虫对机体的致病作用研究进展   总被引:3,自引:0,他引:3  
球虫在鸡体内进行生命活动的同时对鸡体产生不同程度的损害,球虫感染后的致病性和病理学反应是球虫与宿主机体相互作用的结果。本文就鸡球虫致病作用及其对宿主细胞代谢的影响、及影响球虫致病性的因素的研究进展予以综述,对鸡球虫病的防治具有一定的指导意义。  相似文献   
38.
通过在21日龄的肉用仔鸡饲料中添加丝兰属植物提取物(其有效成分为丝兰皂角苷),研究丝兰属植物提取物对降低鸡舍中氨气浓度和提高肉仔鸡生产性能的效果。试验结果表明,试验组鸡舍内氨气平均浓度为4.75mg/L,对照组鸡舍内氨气平均浓度为13.80mgl/L,试验组比对照组鸡舍内氨气平均浓度降低了9.05mg/L,经t检验,两鸡舍内氨气平均浓度差异显著(P<0.05),并且试验组比对照组饲料报酬提高了8.92%。  相似文献   
39.
施肥对黔中地区混播草地牧草生长性能的影响   总被引:2,自引:0,他引:2  
本文研究了氮磷钾不同配比施肥量对黑麦草和紫花苜蓿混播草地牧草生长的影响,结果表明:氮肥促进禾本科牧草叶的生长(P<0.05),增施钾肥对禾草的生长有利;磷能促进豆科牧草根的生长(P<0.05)且豆科牧草株高随着施磷量的增加各处理间差异显著(P<0.05),高氮抑制豆科牧草的生长;最高产量的施肥方式:N:P_2O_5:K_2O为20:30:20,比对照处理的草地产量增加63.92%。  相似文献   
40.
AIM: To investigate the blocking effects of sodium ferulate (SF) on the nonenzymatic glycation and oxidation in kidneys of diabetic rats. METHODS: The diabetic rats induced by streptozotocin (STZ) were treated with SF (110 mg/kg) per day for 8 weeks. The renal weight/body weight, clearance rate of creatinine (Ccr), proteinuria, advanced glycation end products (AGEs) in renal cortex, and the malonyldialdehyde (MDA), fructosamine (FMN), antioxidant enzymes in serum and renal cortex were measured. The pathologic changes of kidneys were also observed. RESULTS: The levels of Ccr, proteinuria, FMN and AGEs in renal cortex, FMN in serum, and renal weight/body weight in diabetic control group were significantly higher than those in normal control group. In the diabetic control group, there was a highter level of MDA and a lower activity of superoxide dismutase (SOD) and catalase (CAT) in serum and renal cortex than those in normal control group. Except for FMN in renal cortex, the abnormalities were significantly ameliorated in the treatment group. The pathologic changes was significant in the diabetic control group, which was significantly ameliorated with the treatment of SF. CONCLUSIONS: SF protects the activity of antioxidant enzymes, clears away oxygen radicals and inhibits the deposit of AGEs in kindey, which may be the mechanisms of protecting effects of SF on kindey in diabetic rats.  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