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   969篇
  免费   87篇
  国内免费   74篇
林业   20篇
农学   48篇
基础科学   25篇
  24篇
综合类   262篇
农作物   34篇
水产渔业   165篇
畜牧兽医   468篇
园艺   64篇
植物保护   20篇
  2024年   1篇
  2023年   26篇
  2022年   30篇
  2021年   51篇
  2020年   37篇
  2019年   36篇
  2018年   22篇
  2017年   54篇
  2016年   44篇
  2015年   42篇
  2014年   30篇
  2013年   74篇
  2012年   75篇
  2011年   85篇
  2010年   47篇
  2009年   33篇
  2008年   40篇
  2007年   41篇
  2006年   30篇
  2005年   30篇
  2004年   45篇
  2003年   29篇
  2002年   32篇
  2001年   29篇
  2000年   21篇
  1999年   32篇
  1998年   16篇
  1997年   25篇
  1996年   22篇
  1995年   11篇
  1994年   5篇
  1993年   6篇
  1992年   5篇
  1991年   6篇
  1990年   5篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1984年   2篇
  1981年   1篇
  1980年   3篇
  1979年   1篇
  1978年   1篇
排序方式: 共有1130条查询结果,搜索用时 93 毫秒
21.
根据花生仁的自然属性,分析了花生仁去衣的特点;并应用动态磨削的观点设计了花生仁去衣机构,且对花生仁在机构中运动的受力和去衣过程进行了分析。  相似文献   
22.
贾兰兰  王依依  华跃进  徐虹 《核农学报》2020,34(6):1205-1212
瓣状核酸内切酶(FEN1)是结构特异性5'核酸酶超家族成员,以参与冈崎片段成熟、DNA重组、细胞凋亡DNA片段化和长片段碱基切除修复(LP-BER)而闻名,在生物体的多种代谢途径中发挥作用,对维持不同物种基因组的稳定性发挥着十分重要的作用。FEN1的功能或表达异常会导致生物体内的多个生命过程发生紊乱,如突变率增加、微卫星序列不稳定、DNA降解等,对生物体造成严重危害。因此,FEN1在生物体内的表达必须受到严格、精确、及时的调控。研究表明,翻译后修饰对FEN1蛋白的活性强弱、细胞定位及功能稳定性发挥着重要的调控作用。本文对关于FEN1翻译后修饰调控的相关研究进展进行总结,系统归纳翻译后修饰对FEN1功能的调控和影响,为后续开展FEN1程序性调控研究提供了参考。  相似文献   
23.
皮肤的大面积损伤在兽医临床上较为多见,但现有的治疗手段很难满足动物美观的要求,皮肤扩张技术以其扩张获得的“额外”的皮肤与正常皮肤直接缝合以作修复疤痕组织或皮肤缺损,这样既解决了修复所需要的皮源问题,又可以避免大面积植皮形成的新的瘢痕组织,扩张皮肤克服了植皮色素沉着,与周围皮肤颜色不协调,遗留供区新创面的缺点,成为国内外医学界修复瘢痕广泛应用的新技术,应用前景十分广阔。  相似文献   
24.
大孔树脂分离纯化柚皮黄酮的研究   总被引:16,自引:5,他引:16  
该文以总黄酮含量和总黄酮回收率为考察指标,研究了大孔树脂分离纯化柚皮黄酮的工艺。结果表明:AB-8型树脂对柚皮总黄酮有较好的吸附分离性能,是分离纯化柚皮黄酮的适宜大孔树脂;AB-8型大孔树脂分离纯化柚皮黄酮的最佳工艺条件为:柱体积为160 mL,柚皮提取物上样量为62.5 mg/mL(以湿树脂体积计),先用pH 4的水淋洗,再用30%的乙醇洗脱,洗脱剂用量为2.5~3倍湿树脂体积。AB-8大孔树脂按上述确定的吸附洗脱条件可重复使用3次。柚皮黄酮经上述工艺纯化后总黄酮含量达到39.67%,总黄酮回收率为62.48%。对经AB-8大孔树脂纯化后的柚皮黄酮进行高效液相色谱(HPLC)分析发现,柚皮黄酮主要为黄酮甙类。  相似文献   
25.
为了确定细胞学检查在犬皮肤肥大细胞瘤诊断中的诊断意义,采取细胞学检查和病理组织学检查相结合的方法对2例犬皮肤肥大细胞瘤临床病例进行诊断。结果显示:细胞学检查结果与病理组织学检查结果相符。由此可以得出,在犬皮肤肥大细胞瘤的诊断中,细胞学检查具有一定的诊断价值,为肿瘤的性质及分化程度分级提供参考,为该病临床诊断提供了一种新的辅助方法。  相似文献   
26.
用脂肪酶对罗非鱼鱼皮进行酶法脱脂工艺研究。通过单因素与正交试验确定最适的酶法脱脂工艺为:pH值9,脱脂时间3h,酶添加量2%,料液比1:4,温度40℃,该工艺的脱脂率可达67.5%。通过超声波辅助脱脂研究表明其脱脂率并无明显的提高。  相似文献   
27.
日本鳗鲡腐皮病病原菌的分离及鉴定   总被引:8,自引:3,他引:5  
从患腐皮病的日本鳗鲡(Anguilla japonica)体表溃烂处分离到1株病原菌(322A),对其进行了人工感染实验和生理生化分析,测定了该菌株的16S rRNA基因序列和促旋酶(gyrase)B亚单位gyrB基因序列,并分别构建系统发育树。结果显示:感染实验证实菌株322A具有致病性;生理生化分析鉴定该菌株属于气单胞菌属(Aero-monassp.);16S rRNA基因分析显示,该菌株与气单胞菌属细菌的同源性均在99%~100%,构建的系统树显示,菌株322A与嗜水气单胞菌(A.hydrophila(FJ462702))亲缘关系最近;gyrB基因分析表明,该菌株与A.hydrophila种内序列的相似性为96%~98%,种间序列的相似性为94%~95%,构建的系统树结果显示,该菌株与A.hydrophila(FJ608553、FJ608552、AF208259)聚为一个分支。综合上述实验结果,菌株322A可鉴定为嗜水气单胞菌(A.hydrophila)。  相似文献   
28.
River crab (RC) meal (Procambarus clarkii) and marine crab (MC) meal (Chaceon affinis) were tested as a partial replacement for fish meal in diets for red porgy (Pagrus pagrus), and their effects on growth performance, fish proximate composition and skin colouration were evaluated. Red porgy were fed during 165 days with five diets. High‐quality fish meal diet was used as a control diet (CD). Protein of fish meal in the control was replaced by increasing the dietary levels of protein derived from RC and MC by up to 10% and 20% of each of them (RC10, RC20, MC10 and MC20). Fish fed on MC20 showed the highest values in feed intake, weight gain and growth (%). No differences were found in FCR and protein efficiency ratio among the treatments. Inclusion of both crab meals in diets significantly decreased the lipid content in whole fish compared with the control animals. On the other hand, no differences in muscle composition were found between the diets. Feeding both crab meals resulted in colour improvement compared with that of the control fish, with better hue values for the RC meal group than those for the MC meal group. The crab meals tested in the present study are suitable as a partial replacement for fish meal in diets for the red porgy, with the MC meal improving growth and both crabs meals improving skin colour, with further improvements in skin colour produced in fish‐fed diets containing the RC meal.  相似文献   
29.
A substantial fraction of miRNA* species are conserved in animals and can repress activities of target genes. This study aims to investigate the miRNA* species in duck skin by using Solexa sequencing. We obtained a total of 96 miRNA* species in two skin small RNA libraries and identified 56 miRNA/miRNA* (miR/miR*) pairs. Nucleotide bias of miRNA* indicated that the priority was C>A>U>G for the first nucleotide and U>C>A>G for the last nucleotide. Comparison analyses showed that 3′-U accounted for a higher proportion in the 56 miR/miR* pairs. Among the top 20 expressed miRNA* species, 17 were shared by two libraries and most of the miRNA* species were highly conservative, especially in the “seed region”. miR-199a* were expressed highly in our samples, which was also previously shown abundant in mouse hair follicle. Furthermore, four miRNA* species were predicted to target their genes in signal pathways of feather follicle development and feather morphogenesis despite very low levels.  相似文献   
30.
The optimal concentration of a panel of individual and combined carotenoid sources on skin pigmentation in fancy carp was investigated by nine experimental diets that were formulated and supplemented with astaxanthin at 25 mg kg?1, lutein at 25 and 50 mg kg?1, β‐carotene at 25, 50 and 75 mg kg?1, and lutein combined with β‐carotene at 25 : 25 and 50 : 50 mg kg?1, while a diet without supplemented carotenoid served as a control. The results showed that serum TC of fish fed diets containing supplemented with lutein plus β‐carotene at 25 : 25; 50 : 50 mg kg?1 and lutein 50 mg kg?1 diet were higher than the other treatments (P ≤ 0.05). Serum TC of the respective treatments was 6.2 ± 2.0, 7.8 ± 3.3 and 7.3 ± 1.9 μg mL?1 serum, respectively. Fish fed diets combined with lutein and β‐carotene at 25 : 25, 50 : 50 mg kg?1 and lutein 50 mg kg?1 diet had serum astaxanthin concentrations similar to fish fed the diet with astaxanthin alone at 25 mg kg?1. Serum astaxanthin concentrations was 0.7 ± 0.01, 0.9 ± 0.01, 0.4 ± 0.02 and 1.7 ± 0.18 μg mL?1 serum, respectively. The chromaticity of fish body skin of red and white position was assessed by colourimetry using the CIE L*a*b (CIELAB) system. Pigmentation response of skin redness of fancy carp fed with diets combined with lutein and β‐carotene at 25 : 25, 50 : 50 mg kg?1 and lutein 50 mg kg?1 were higher than other treatments (P ≤ 0.05) but they were similar to fish fed with 25 mg kg?1 astaxanthin diet. The redness (a* values) of fish fed diets with diets combined with lutein and β‐carotene at 25 : 25, 50 : 50 mg kg?1 and lutein 50 mg kg?1 were 28.3 ± 0.53, 29.9 ± 1.38, 28.8 ± 3.95 and 28.5 ± 2.49, respectively. After 3 weeks of feeding the experimental diets, the fish fed on a diet without carotenoid supplement for one week demonstrated that the same three groups still retained their redness and had an overall tendency to improve skin colouring. Finally, concentrations 50 mg kg?1 of lutein, or the combination of lutein and β‐carotene at 25 : 25 mg kg?1 showed the highest efficiency for improving skin pigmentation and redness of skin.  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