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   491篇
  免费   28篇
  国内免费   31篇
林业   20篇
农学   48篇
基础科学   9篇
  8篇
综合类   201篇
农作物   57篇
水产渔业   56篇
畜牧兽医   87篇
园艺   47篇
植物保护   17篇
  2023年   6篇
  2022年   13篇
  2021年   16篇
  2020年   14篇
  2019年   14篇
  2018年   10篇
  2017年   16篇
  2016年   33篇
  2015年   21篇
  2014年   39篇
  2013年   23篇
  2012年   28篇
  2011年   35篇
  2010年   30篇
  2009年   24篇
  2008年   17篇
  2007年   35篇
  2006年   39篇
  2005年   25篇
  2004年   12篇
  2003年   10篇
  2002年   17篇
  2001年   13篇
  2000年   5篇
  1999年   10篇
  1998年   4篇
  1997年   14篇
  1996年   4篇
  1995年   8篇
  1994年   2篇
  1993年   4篇
  1992年   2篇
  1989年   2篇
  1988年   1篇
  1986年   4篇
排序方式: 共有550条查询结果,搜索用时 121 毫秒
1.
We developed an H5/H7 trivalent inactivated vaccine by using Re-11, Re-12, and H7-Re2 vaccine seed viruses, which were generated by reverse genetics and derived their HA genes from A/duck/Guizhou/S4184/2017(H5 N6)(DK/GZ/S4184/17)(a clade 2.3.4.4 d virus), A/chicken/Liaoning/SD007/2017(H5 N1)(CK/LN/SD007/17)(a clade 2.3.2.1 d virus), and A/chicken/Guangxi/SD098/2017(H7 N9)(CK/GX/SD098/17), respectively. The protective efficacy of this novel vaccine and that of the recently used H5/H7 bivalent inactivated vaccine against different H5 and H7 N9 viruses was evaluated in chickens. We found that the H5/H7 bivalent vaccine provided solid protection against the H7 N9 virus CK/GX/SD098/17, but only 50–60% protection against different H5 viruses. In contrast, the novel H5/H7 trivalent vaccine provided complete protection against the H5 and H7 viruses tested. Our study underscores the importance of timely updating of vaccines for avian influenza control.  相似文献   
2.
Despite significant improvements in aquaculture to compensate wild catch, disease organisms have thrived in limiting its national and global potential. Using antibiotics, in a bid to remedy the havoc, has given rise to complications, attracting attention to disease prevention by immune enhancement against diseases. Grouper production has been inhibited for the threats of bacterial infection, particularly of Vibrio origin. Considering the rise in vibriosis cases, improved vaccines are necessary; moreover, recombinant vaccines, the choice for trial in the present experiment have been effective and more specific in improving immunity. The current work deals with grouper immune system enhancement with a recombinant vaccine developed from VirB11 gene in Vibrio harveyi. VirB11 was cloned in V. harveyi for recombinant vaccine development against vibriosis in orange‐spotted grouper (Epinephelus coioides). As indicated by the results, recombinant VirB11 protein showed effectiveness in conferring protection against vibriosis with observable specific antibody response in enzyme‐linked immunosorbent assay (ELISA) analysis; a significant increase (p < 0.05) in antibody levels was observed after a week and after 8 weeks post‐vaccination. From the weeks post‐vaccination, log2 (antibody titres) in the sera of vaccinated groups reached a peak of 14.2 at week 5 in the vaccinated group in comparison with a peak of approximately 5 and 2 in adjuvant and PBS controls. As indicated by the challenge results, 90% relative survival was observed in vaccinated group and 13% relative survival in control group I (adjuvant control). The cumulative performance of protein concludes VirB11 commendable for recombinant vaccine development.  相似文献   
3.
4.
石豆11号是由石家庄市农林科学研究院以化诱446为母本,冀豆4号为父本经有性杂交选育而成。2014-2015年参加河北省夏播大豆区域试验,平均产量3 093.9 kg·hm~(-2),较对照冀豆12增产2.51%。2016年参加河北省夏播大豆生产试验,平均产量3 108.0 kg·hm~(-2),较对照冀豆12增产0.87%。2017年通过河北省农作物品种审定委员会审定,准予推广。石豆11号的主要特点是高蛋白(45.79%)、高产、抗倒伏,适宜在河北省中南部夏播种植。  相似文献   
5.
研究了雄性不育系高粱11A与苏丹草3个杂交组合F1代的生育、产量、光合性能等主要农艺特性及细胞遗传学特性。结果表明,3个杂交组合F1代的生长势和平均株高均明显超过其各自父本苏丹草,继承了苏丹草分蘖能力强和高粱11A抗倒伏的优良特性,生育期126~130 d,穗型呈双亲中间型;F1代花粉可育率均高达93%以上,结实性好,自然结实率62.34%~68.75%,杂交组合间差异不明显;F1代PMCMⅠ的平均染色体构型均为2n=2x=20(10Ⅱ),配对行为较规则,但棒状二价体频率明显高于其3个父本苏丹草和母本高粱11A,原亲本间遗传组成存在一定差异。综合分析植株生长、产量性状、光合性能等指标,得出3个杂交组合F1代的育种潜力依次为:高粱11A×棕壳苏丹草F1≥高粱11A×黑壳苏丹草F1>高粱11A×白壳苏丹草F1。  相似文献   
6.
为了解从湖南省洞庭湖区鸭群中分离的2株 H11N9亚型禽流感病毒变异特点、进化规律及生物学特性,本研究对2株H11N9亚型禽流感病毒的HA、NA序列进行同源性和遗传进化分析,并用2株毒株对SPF鸡进行致病性试验。结果显示,本试验分离到2株 H11N9亚型禽流感毒株的 HA裂解位点均没有多个连续的碱性氨基酸插入,属于低致病性毒株;HA基因的受体结合位点均非常保守,具有典型的禽源性特征;NA基因序列与在周边国家野鸟中分离的H11N9亚型毒株的氨基酸同源性较高;鼻腔接种SPF鸡后,均能使鸡感染并通过喉头或泄殖腔排毒,但感染的鸡均不表现明显的临床症状,并且不能使同居鸡感染排毒。  相似文献   
7.
为揭示类固醇生成相关基因CYP11A1、CYP17A1、CYP19A1在绵羊多羔繁殖中的作用,以不同繁殖力小尾寒羊为研究对象,采用实时荧光定量PCR技术检测CYP11A1、CYP17A1、CYP19A1基因在小尾寒羊大脑、小脑、下丘脑、垂体、子宫、卵巢、输卵管中的表达。结果表明:CYP11A1基因主要在小尾寒羊卵巢、输卵管、子宫内表达;CYP11A1基因在单羔小尾寒羊卵巢的表达极显著低于多羔群体(P0.01),在子宫的表达量极显著高于多羔群体(P0.01);CYP17A1基因主要在小尾寒羊卵巢、输卵管、下丘脑表达;CYP17A1基因在多羔小尾寒羊群体下丘脑、子宫的表达量显著低于单羔群体(P0.05)。CYP19A1基因主要在小尾寒羊卵巢、下丘脑表达。本究结果提示CYP11A1、CYP17A1基因可能参与小尾寒羊多羔性状的调控。  相似文献   
8.
AIM: To establish a method for obtaining specific cells in solid tumor tissue by sorting of CD11b+ myeloid cells in hepatic metastases from colorectal cancer.METHODS: Tumor tissues were prepared into single cell suspension by mechanical method combined with enzyme digestion, and then the CD11b+ myeloid cells were isolated by flow cytometry. The sorted cells were identified by immunocytochemistry. The viability and morphologiy of the sorted cells were evaluated by Giemsa and Typan blue staining. The cell purity was evaluated by flow cytometry.RESULTS: Sufficient numbers of CD11b+ cells with high purity were isolated by sorting with flow cytometry from the single cell suspension prepared by mechanical and enzyme digestion. The purity of the cells was confirmed by statistical analysis (P<0.05). The positive rates of the cells before and after sorting were significantly different (P<0.01). The positive cells were verified by immunocytochemical method. Meanwhile, the sorted cells had complete morphology and good activity.CONCLUSION: The CD11b+ myeloid cells in solid tumor tissue can be isolated by flow cytometry from the machine-enzyme digestion suspension with high purity, good activity and complete morphology.  相似文献   
9.
王龙  王田勇  赫东玉  黄金宝  文辉 《北方水稻》2011,41(6):34-35,43
通过对垦稻11号进行不同插期、不同密度和不同施肥量级的试验,找出其在我场大田生产上推广繁育的合理栽培方法和模式。试验结果表明,垦稻11号的最适宜插秧时间是5月13~23日,插秧规格30 cm×13 cm为宜,每穴3~5苗,施肥量应以处理2为准,N∶P∶K比例为2∶1.05∶0.65。  相似文献   
10.
采用三因素裂区试验设计,研究了种植密度和摘薹对双低油菜宁杂11号、宁油16号的菜薹产量、菜籽产量及净收益等的影响。结果表明:宁杂11号各处理的菜籽产量和净收益均显著高于宁油16号,但菜薹产量略低于宁油16号。随着种植密度提高,宁杂11号的净收益显著增加,但摘薹后净收益增加不大。宁油16号摘薹后净收益大幅度增加。摘薹后油菜生育期推迟、株高降低、总角果数减少、千粒重下降,但角果长度和每角粒数能显著增加。  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