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   186篇
  免费   6篇
  国内免费   17篇
林业   5篇
农学   8篇
基础科学   13篇
  26篇
综合类   99篇
农作物   20篇
水产渔业   8篇
畜牧兽医   15篇
园艺   5篇
植物保护   10篇
  2023年   1篇
  2022年   5篇
  2021年   3篇
  2020年   7篇
  2019年   5篇
  2018年   1篇
  2017年   6篇
  2016年   3篇
  2015年   53篇
  2014年   30篇
  2013年   9篇
  2012年   10篇
  2011年   5篇
  2010年   5篇
  2009年   1篇
  2008年   10篇
  2007年   2篇
  2006年   4篇
  2005年   9篇
  2004年   6篇
  2003年   2篇
  2002年   4篇
  2001年   4篇
  2000年   6篇
  1999年   1篇
  1998年   1篇
  1997年   1篇
  1995年   2篇
  1993年   3篇
  1992年   1篇
  1989年   1篇
  1988年   1篇
  1987年   1篇
  1984年   2篇
  1980年   2篇
  1958年   1篇
  1953年   1篇
排序方式: 共有209条查询结果,搜索用时 31 毫秒
11.
通过近两年在江西省北部的瑞昌市武蛟乡、湖口县武山镇和九江县永安乡试验基地开展棉花与早熟西瓜套作高效栽培试验,结果表明:在丘陵旱地栽2行棉花1行西瓜,棉花的株距45cm,双行间距60cm,密度12345株/hm2,西瓜的株距46cm,密度6000株/hm2,其配置模式效益最佳。其籽棉产量4147.9kg/hm2,西瓜产量为26250kg/hm2,两者产值达113592.5元,h0。  相似文献   
12.
Weedy rice(Oryza sativa f. spontanea), the predominant type of which has a red pericarp, seriously inhibits growth and yield of direct-seeded rice in Jiangsu Province, China. In this study, we randomly selected 10 weedy rice accessions from 10 plots in Jiangsu, and then sequenced the full lengths of their Rc genes(approximately 6.4 kb). In addition, we collected 166 different full-length Rc genes in the Oryza genus from the literature and from GenBank. A collinearity sequence analysis showed that the 10 weedy rice accessions from Jiangsu all had the same wild-type allele of the Rc gene. Single nucleotide polymorphisms indicated that the nucleotide polymorphisms(π = 0.19) and the proportion of segregation sites(θw = 0.28) of the Rc genes in the 10 weedy rice accessions from Jiangsu were higher than those in 56 weedy rice accessions from USA(π = 0.09 and θw = 0.07). Haplotype and phylogenetic analyses showed that the Rc genes of weedy rice accessions from Jiangsu were not revertants of the rc gene found in Asian cultivated rice(O. sativa) varieties with white pericarp. In addition, Rc gene sequences of the rice varieties Lvdao from Lianyungang, Jiangsu and Tangdao from Anhui were more similar to those of cultivated rice than to the weedy rice from Jiangsu. These findings support the continued quarantine of weedy rice and clarify the evolutionary mechanism of the red pericarp found in the weedy rice of Jiangsu.  相似文献   
13.
[目的]仔猪在14日龄接种蓝耳病毒疫苗,25日龄接种猪瘟疫苗,检测接种蓝耳病疫苗和猪瘟疫苗后的免疫合格率。[方法]采用猪繁殖与呼吸综合征病毒和猪瘟病毒ELISA抗体检测试剂盒检测抗体表达量。[结果]猪蓝耳病疫苗免疫3 d后,6.7%免疫个体为抗体阳性,免疫7 d后,26.7%免疫个体为抗体阳性,免疫14 d后,85%免疫个体为抗体阳性,免疫后30 d 100%免疫个体为抗体阳性;猪瘟疫苗免疫3 d后,13%免疫个体为抗体阳性,免疫7 d后,40%免疫个体为抗体阳性,免疫14 d后,58.3%免疫个体为抗体阳性,免疫30 d后,83.3%免疫个体为抗体阳性。[结论]仔猪在蓝耳病疫苗免疫3 d后抗体效价最低,30 d后免疫效果很好,接种猪瘟疫苗3 d后抗体效价最低,仔猪不足以抵抗病毒侵袭,虽然蓝耳病疫苗和猪瘟疫苗接种后30 d,抗体水平都达到了农业部规定的70%的标准,但是猪瘟疫苗免疫效果不能达到100%理想效果。  相似文献   
14.
为了对玉米群体进行合理有效的改良利用,通过改良S1选择法对12个玉米群体改良一轮后进行效果比较分析。结果表明,穗行数、行粒数和百粒重是构成产量的三因素,遗传增益最大的群体为蒙群2,其它依次为蒙群4、蒙群1等7个群体,蒙群3及3个国外引进群体遗传增益为负值;玉米群体在穗部、植株性状以及遗传变异中均存在一定的变化。试验研究得出,蒙群2、蒙群4、中综7号、蒙 C群、蒙 A群产量遗传增益均较大,并在其他农艺性状中改良效果显著,可直接选择优株自交进行选系,而其余7个群体遗传增益小,改良利用潜力不大。  相似文献   
15.
ln this research, the whole contact-type large-scale sow house with fer-mentation bed was designed. The planning area of the entire piggery was 5 700 m2 with workplace and green belts. The sow house was 93 m long and 33 m wide, a total of 3 069 m2, including office area of 60 m2 and aisle area of 107 m2. The fer-mentation bed had an area of 2 902 m2 with length of 88.7 m and width of 27.7 m. lts area accounted for 95% of the total area of sow house. The fermentation mattress had a depth of 80 cm, and had a volume of 2 321 m3, equivalent to 733 t of coconut chaff and rice chaff. On a large fermentation bed, the areas for boars, replacement gilts, pregnant sows, obstetric tables, nursery pigs, etc. were designed. The large-scale sow house with fermentation bed was equipped with the automatic feeding system, automatic sprinkler system, automatic positioning column for preg-nant sows, sows' obstetric table system, fanning wet curtain cooling system, video monitoring system, environmental monitoring (light, temperature, water, humidity, CO2, NH3) and automatic control system. Every farming area was equipped with feeding trough and water trough. The water though was fixed with overflow pipe for removing the extra water. The house could hold 500-head sows. Each sow occu-pied 4.9 m2 of the fermentation bed in average. The designed sow house had a maximum annual output of 10 000 piglets.  相似文献   
16.
The Valencian region, in eastern Spain, is home to ≈3050 vascular plant species, 68 of which are listed under the critically endangered IUCN category. To afford protection to our endangered, rare and endemic flora, a network of small (2-20 ha) statutory reserves has been created by the Regional Wildlife Service. These are termed “micro-reserves” and encompass a large number of individual species and natural habitats. The objective is to monitor long term changes in the plant populations and to carry out active management of the protected plants. In the selection of plots, criteria of distinctiveness and endangerment of plants was followed. Eight years after the onset of this initiative, plant micro-reserves have become an essential tool for the effective protection of the diverse flora of this Mediterranean region.  相似文献   
17.
18.
再论光敏核不育水稻育性转换的光温作用模式   总被引:21,自引:2,他引:21  
  相似文献   
19.
1亲本来源母本Lx9801是从山东省农科院玉米所引进的自交系。Lx9801配合力高,结实性优良,茎秆粗壮,长势强壮,抗逆性等综合性状较好。  相似文献   
20.
将克隆并测序的鸡卵清蛋白基因5′端调控序列和鸡IL-2基因cDNA,以串联方式置于真核表达载体pcDNA3的CM V启动子下游,构建了鸡输卵管定位表达载体pcDNA3-OVP-IL 2。将真核表达载体pcDNA3-IL 2和构建的输卵管定位表达载体pcDNA3-OVP-IL 2分别转染鸡输卵管上皮细胞,激素诱导72 h后,用淋巴细胞转化试验检测细胞培养液中IL-2的表达水平及生物学活性。结果显示,转染细胞均可表达IL-2,且所表达的IL-2有促进T淋巴细胞转化和淋巴母细胞成熟的活性;转染pcDNA3-OVP-IL 2的输卵管上皮细胞表达产物在1∶256稀释水平下仍具有促进T淋巴细胞转化和淋巴母细胞成熟的活性。转染pcDNA3-IL 2载体的输卵管上皮细胞虽有IL-2表达,但水平较低。  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