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   2649篇
  免费   77篇
  国内免费   129篇
林业   182篇
农学   288篇
基础科学   87篇
  246篇
综合类   1212篇
农作物   211篇
水产渔业   41篇
畜牧兽医   198篇
园艺   324篇
植物保护   66篇
  2024年   14篇
  2023年   23篇
  2022年   46篇
  2021年   53篇
  2020年   60篇
  2019年   82篇
  2018年   40篇
  2017年   83篇
  2016年   95篇
  2015年   114篇
  2014年   145篇
  2013年   145篇
  2012年   224篇
  2011年   248篇
  2010年   179篇
  2009年   191篇
  2008年   182篇
  2007年   160篇
  2006年   150篇
  2005年   116篇
  2004年   82篇
  2003年   77篇
  2002年   39篇
  2001年   35篇
  2000年   44篇
  1999年   34篇
  1998年   24篇
  1997年   34篇
  1996年   28篇
  1995年   13篇
  1994年   24篇
  1993年   15篇
  1992年   12篇
  1991年   17篇
  1990年   4篇
  1989年   6篇
  1988年   7篇
  1987年   3篇
  1986年   1篇
  1985年   2篇
  1984年   1篇
  1981年   1篇
  1977年   1篇
  1963年   1篇
排序方式: 共有2855条查询结果,搜索用时 781 毫秒
981.
The present study was carried out with the objective to validate the molecular markers, which have been previously reported to be linked to fertility restorer (Rf) gene(s) for WA-CMS lines of rice. Two mapping populations involving fertility restorer lines for WA-cytoplasm, viz., (i) an F2 population derived from the cross IR58025A/KMR3R consisting of 347 plants and (ii) a BC1F1 population derived from the cross IR62829A/IR10198R//IR62829A consisting of 130 plants were analyzed. Nine SSR and three CAPS markers reported to be linked to Rf genes along with two previously unreported SSR markers were analyzed in the mapping populations. In both the populations studied, the trait of fertility restoration was observed to be under digenic control. Eight SSR markers (RM6100, RM228, RM171, RM216, RM474, RM311, MRG4456 and pRf1&2) showed polymorphism between the parents of the F2 population, while the SSR markers RM6100 and RM474 showed polymorphism between the parents of both the F2 and BC1F1 populations. Only one CAPS marker, RG146FL/RL was polymorphic between the parents of the BC1F1 population. RM6100 was observed to be closely segregating with fertility restoration in both the mapping populations and was located at a distance of ~1.2 cM. The largest phenotypic variation was accounted for the region located between RM311 and RM6100. Using the marker-trait segregation data derived from analysis of both the mapping populations, a local linkage map of the genomic region around Rf-4, a major fertility restoration locus on Chromosome 10 was constructed, and RM6100 was observed to be very close to the gene at a distance of 1.2 cM. The accuracy of the marker RM6100 in predicting fertility restoration was validated in 21 restorers and 18 maintainers. RM6100 amplified the Rf-4 linked allele in a majority of the restorers with a selection accuracy of 94.87%. Through the present study, we have established the usefulness of the marker RM6100 in marker-assisted selection for fertility restoration in segregating populations and identification of restorers while screening rice germplasm for their fertility restoration ability.  相似文献   
982.
There is no information in the literature about the variability of resistance of Chinese Brassica vegetables, pak choi and Chinese cabbage, to the white blister disease caused by Albugo candida (Pers.) Kuntze. A collection of 43 accessions of pak choi and 19 accessions of Chinese cabbage was screened for resistance to the Portuguese A. candida isolate Ac 506 at the cotyledon stage. Different levels of resistance were found among the germplasm tested, ranging from complete resistance to full susceptibility. Most of the accessions were highly susceptible with less than 10% of resistant seedlings, and only four accessions of pak choi, presenting more than 50% resistant seedlings, were considered as new sources or resistance to white blister. Inheritance of resistance at the cotyledon stage was studied in two crosses between the most resistant pak choi accession, BRA 117, and the highly susceptible rapid cycling Brassica rapa line CrGC 1.19. It was proposed that resistance to white blister in pak choi BRA 117 is controlled by two nuclear genes with dominant recessive epistatic gene action.  相似文献   
983.
鸡公山野生木本蔬菜资源调查   总被引:1,自引:0,他引:1  
木本蔬菜绿色食品,营养价值高,开发潜力大。于2008年对鸡公山野生木本蔬菜资源进行调查,结果表明鸡公山有野生木本蔬菜植物34科74种,并对其开发利用提出建议。  相似文献   
984.
介绍了鲜切果蔬的概念、历史、优点、加工工艺及操作技术要点,概述了不同鲜切条件对果蔬生理生化及品质的影响,加工与保鲜过程中微生物污染,褐变机理及营养成分变化等,提出了防止褐变发生及延长保鲜期的具体方法,并探讨了果蔬鲜切和保鲜现状及发展趋势。  相似文献   
985.
果蔬速冻保鲜技术研究进展   总被引:9,自引:1,他引:8  
介绍我国速冻果蔬行业的发展现状。综述了果蔬速冻保鲜技术各工艺环节的应用现状和最新进展,并对速冻果蔬的发展前景作了展望。  相似文献   
986.
高压矩形脉冲电场果蔬预处理微观结构变形机理的研究   总被引:2,自引:0,他引:2  
基于电磁力学理论,结合苹果单细胞模型,研究其性状的变化,获得了HPEF作用果蔬的微观机理。研究显示,HPEF处理果蔬的效果与物料性质有关,不同物料预处理显著程度不同,主要是由于不同物料的细胞参数以及其结构引起力学性质的改变不同;HPEF处理作用强度越大,细胞膜受到的应力也越大。  相似文献   
987.
天门山国家森林公园野生观赏植物资源调查与评价   总被引:1,自引:0,他引:1  
通过对张家界天门山野生观赏植物资源进行了初步调查和统计分析,并根据性质和用途对其进行分类,结合生态类型进行分析,结果表明:该地有野生观赏植物266种,隶属182属,92科,观赏植物资源种类丰富、区系组成古老、生活型多样性、观赏价值较高等特点。为进一步保护与合理开发利用天门山野生观赏植物资源,推动天门山旅游和张家界园林事业的发展,振兴地方的经济,提出了五点建议。  相似文献   
988.
通过野外实地调查及实验室标本鉴定,得知昆嵛山国家森林公园分布有野生豆科植物37种,隶属于20个属。在研究各物种生态习性的基础上,探讨了野生豆科植物在生物制药、工业、农业及水土保持方面的利用价值及开发前景,提出开发建议,力求为开发利用野生豆科植物提供基础资料。  相似文献   
989.
Wild service tree [Sorbus torminalis (L.) Crantz] is a forest tree widespread in Europe, characterized by a scattered distribution. Its hermaphroditic flowers are pollinated by insects, and outcrossing is the prominent mating system, also due to the presence of gametophytic self-incompatibility. Genetic diversity and differentiation of 22 populations from northwestern Italy were investigated by means of variation scored at 53 polymorphic RAPD (Random Amplified Polymorphic DNA) loci. Populations differed in genetic variation, with Shannon diversity index ranging from 0.166 to 0.469. According to Analysis of Molecular Variance (AMOVA), most of the genetic variation was found within populations (61.78%) with a significant proportion of variance attributable to genetic differences between regions (23.60%) and between populations (14.62%). Evidence for isolation by distance was found in the set of populations sampled. The effect of habitat fragmentation on genetic variation was also evaluated. The efficacy of RAPD markers in analysing genetic variation, and the contribution of the results in terms of the preservation of biodiversity are discussed.  相似文献   
990.
野生鸭茅生育特性多样性研究   总被引:2,自引:0,他引:2  
彭燕  张新全  曾兵 《安徽农业科学》2008,36(13):5368-5371
[目的]系统研究野生鸭茅生长发育特性。[方法]对从我国野生鸭茅主要分布区和国外收集的35份野生鸭茅种质的生育特性进行研究。[结果]早熟型在拔节期前后进入生长高峰期,日均增长速度最快为1.93 cm/d,生育期为249 d,营养、生殖生长期分别为199、50 d;缓慢生长型在整个生长期间的生长速度都极为缓慢,在试验区只有营养生长,而无生殖生长;晚熟型在孕穗期生长速度最快,生育期为289 d,营养、生殖生长分别需251和38 d;中熟型介于早、晚熟型之间;早熟型具有营养生长期比中、晚熟型短,而生殖生长期比中、晚熟型长的特点,前者开花~成熟期要比后两者分别长9和13 d;晚熟型成熟期株高显著高于早、中熟型。[结论]野生鸭茅种质生育特性呈现多样性变异。  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