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   675篇
  免费   48篇
  国内免费   59篇
林业   73篇
农学   45篇
基础科学   12篇
  78篇
综合类   90篇
农作物   62篇
水产渔业   125篇
畜牧兽医   203篇
园艺   24篇
植物保护   70篇
  2024年   1篇
  2023年   11篇
  2022年   16篇
  2021年   30篇
  2020年   18篇
  2019年   16篇
  2018年   31篇
  2017年   30篇
  2016年   26篇
  2015年   14篇
  2014年   23篇
  2013年   48篇
  2012年   42篇
  2011年   42篇
  2010年   43篇
  2009年   31篇
  2008年   41篇
  2007年   32篇
  2006年   20篇
  2005年   19篇
  2004年   16篇
  2003年   42篇
  2002年   63篇
  2001年   53篇
  2000年   35篇
  1999年   14篇
  1998年   7篇
  1997年   4篇
  1996年   3篇
  1995年   2篇
  1992年   1篇
  1989年   3篇
  1988年   2篇
  1987年   1篇
  1982年   1篇
  1965年   1篇
排序方式: 共有782条查询结果,搜索用时 15 毫秒
751.
茶树水分胁迫与干旱研究现状   总被引:2,自引:0,他引:2  
本文对茶树水分胁迫和干旱的国内外研究现状进行了回顾,涉及光合作用、激素代谢、脯氨酸含量、酶活性、无机营养元素、茶树生长和产量品质方面的内容。对茶树抗旱性和水分胁迫进一步研究提供了良好的基础,并对进一步研究趋势进行了探讨。  相似文献   
752.
753.
Fig mosaic virus (FMV), which was described recently, is the only characterized causal agent of fig mosaic disease (FMD). It has six RNA segments and belongs to the Bunyaviridae family. In order to determine the genetic diversity of Turkish FMV isolates, the most common fig cultivars showing FMD symptoms were collected from different fig-growing provinces of Turkey. Nucleoprotein (Np) and Glycoprotein (Gp) gene-specific primers of FMV were used for RT-PCR analysis. According to RT-PCR results, 71 of 90 samples from 20 different cultivars and unknown fig seedlings were found to be infected by FMV. Among them, 41 isolates were sequenced and subjected to phylogenetic analyses based on the partial Gp and Np sequences at the amino acid level by the neighbor-joining method. The isolates showed more than 80% identity with reference FMV isolates (Acc. nos. FM991954.1 and FM864225.2). Based on phylogenetic analysis, the sequences clustered into two main groups for Np and Gp regions. Significant relationships between FMV isolates based on geographic origin and cultivars were not observed.  相似文献   
754.
California privet (Ligustrum ovalifolium Hassk.) plants exhibiting leaf yellowing, witches’ broom, dieback and decline symptoms were observed for two years (2010–2011) in three gardens at Adana region (Turkey). DNA isolated from symptomatic and healthy plants was used to amplify 16S rDNA fragments by direct and nested-PCR. Phytoplasmas were detected in 21 symptomatic plants, out of 30 samples collected, whilst no PCR amplifications were obtained from asymptomatic plants. BLAST analysis of the 16S rDNA showed that the phytoplasma found in L. ovalifolium from Turkey, denoted as Turkish Ligustrum witches’ broom phytoplasma (TuLiWB), most closely resembled members of group 16SrII (peanut witches’ broom group) and shared up to 92 % sequence identity. Based on in silico 16S rDNA RFLP analysis and automated calculation of the pattern similarity coefficient, TuLiWB showed molecular characteristics different from all previously described phytoplasma species to represent a new taxon. Similar indication also emerged from the phylogenetic tree which allocated it in a novel discrete subclade within the phytoplasma clade. This is the first report on the presence of a phytoplasma affecting L. ovalifolium and whether this novel phytoplasma is the same agent reported as a mycoplasma-like organism (MLO) and associated with witches’ broom disease of Ligustrum in Korea (1989) is yet to be determined.  相似文献   
755.
多功能夹心肥料块养分释放特性研究   总被引:1,自引:1,他引:0  
通过室内模拟淋溶实验,对3种多功能夹心肥料块淋溶液中N、P、K进行测定分析。结果表明:(1)多功能夹心肥料块养分N、K累积淋溶曲线均呈"S"型变化,养分P呈持续平缓上升变化;(2)多功能夹心肥料块养分N、P、K淋溶速度明显低于对照处理,其N、K释放高峰期比对照迟缓,P与对照相当;(3)3种肥料块外包被对N、P、K素的缓释作用分别为树叶>牛粪>草炭、牛粪=树叶>草炭、树叶>牛粪>草炭。  相似文献   
756.
通过2年的马铃薯新品种引进与栽培模式试验及生产实践,渭源县北部山区除了大面积种植的陇薯10号、陇薯7号外,晚熟品种青薯9号、定薯3号、陇薯14号、定薯4号、陇薯9号、青薯10号、陇薯15号、L1036-34(拟登记陇薯22号)适宜该区域种植;熟性偏早的冀张薯12号、L12141-6(拟登记陇薯20号)可作为错峰收获品种应用。栽培模式采用机械覆膜垄作放苗、机械覆膜人工点播、机械播种膜上覆土、机械露地起垄播种等种植技术。  相似文献   
757.
九优2117是用荃9311A作母本、雅恢2117作父本杂交选育而成的籼型三系杂交水稻品种,2018年通过国家审定,审定编号:国审稻20186016。2018-2020年北京金色丰度种业科技有限公司在四川省平坝丘陵稻区、重庆市(武陵山区除外)海拔800m以下地区对九优2117进行种植、观察和总结,其株叶形态好,叶片直立,分蘖好,丰产性好、抗性强、米质优,深受种植户的好评。  相似文献   
758.
Bulut  Sancar  Çağlar  Özcan  Öztürk  Ali 《Gesunde Pflanzen》2022,74(2):291-301

In this study, effects of different sowing dates and seeding rates on N uptake efficiency (NUE), N translocation efficiency (NTE), agronomic efficiency (AE), physiological efficiency (PE), water use efficiency for grain yield (WUEg) and water use efficiency for biomass (WUEb) of facultative wheat were investigated. As the average of cropping year, sowing dates and seeding rates, N uptake efficiency (NUE), N translocation efficiency (NTE), agronomic efficiency (AE), physiological efficiency (PE), water use efficiency for grain yield (WUEg) and water use efficiency for biomass (WUEb) values were respectively obtained as 1.17?kg Nuptake/kg Napplied, 68.5%, 36.9?kg grain/kg Napplied, 31.2?kg grain/kg Nuptake, 5.19?kg ha?1 mm?1 and 18.04?kg ha?1 mm?1.

Nitrogen and water use efficiencies decreased with delayed sowing dates and increased with increasing seeding rates. It is possible to maintain a high wheat yield, nitrogen and water use efficiency by increasing plant density through winter sowing. It was concluded based on present findings that sowing date and seeding rates had significant effects on nitrogen and water use efficiencies and winter sowing should be practiced as not to cause yield losses and high seeding rates (575 seeds m?2) yielded greater nitrogen-water use efficiencies.

  相似文献   
759.
模拟酸雨对中药基质土壤微生物的影响   总被引:5,自引:1,他引:5  
用不同pH值(2.5~5)的模拟酸雨处理中药植株白术、元胡、贝母及其基质土壤,测定土壤中微生物的数量。结果表明,各处理pH的模拟酸雨都能抑制细菌、放线菌的生长,其数量随着酸雨pH的降低而不断减少;真菌的数量随酸雨pH的降低呈现先升高后下降的趋势,当pH为2.5时,真菌的含量最低。  相似文献   
760.
通过对合肥市房地产价格现状的调查与分析,本文认为合肥房地产价格总体呈上涨的趋势,但增幅上可能趋缓;只有政府各单位部门多方面的努力和合作,才会使合肥房价更加合理,房产市场更加有序。  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