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   728篇
  免费   33篇
  国内免费   71篇
林业   28篇
农学   191篇
  11篇
综合类   282篇
农作物   87篇
畜牧兽医   136篇
园艺   96篇
植物保护   1篇
  2024年   1篇
  2023年   5篇
  2022年   9篇
  2021年   15篇
  2020年   18篇
  2019年   14篇
  2018年   14篇
  2017年   10篇
  2016年   21篇
  2015年   28篇
  2014年   24篇
  2013年   51篇
  2012年   40篇
  2011年   50篇
  2010年   34篇
  2009年   38篇
  2008年   50篇
  2007年   55篇
  2006年   36篇
  2005年   44篇
  2004年   25篇
  2003年   21篇
  2002年   14篇
  2001年   24篇
  2000年   16篇
  1999年   16篇
  1998年   13篇
  1997年   15篇
  1996年   10篇
  1995年   16篇
  1994年   15篇
  1993年   20篇
  1992年   15篇
  1991年   13篇
  1990年   10篇
  1989年   6篇
  1988年   10篇
  1987年   5篇
  1986年   5篇
  1985年   1篇
  1983年   2篇
  1979年   1篇
  1977年   1篇
  1976年   1篇
排序方式: 共有832条查询结果,搜索用时 15 毫秒
51.
短光低温不育水稻新种质的花药培养研究   总被引:4,自引:0,他引:4  
陆燕鹏  万邦惠  陈雄辉 《种子》2001,(1):15-16,19
对短光低温不育水稻进行花药培养的结果表明:不同基因型材料的花培力差异较大;同一材料在不同的基本培养基和激素配比中进行培养的效果不同,对宜DIS,以M8附加2,4-D(2mg/L) NAA(2mg/L) Kt(1.5mg/L)的花培力最高;不同时间段所取的材料花培力差异较大,可能与材料生长所处的最适环境不同有关;适当的通气状况有利于绿苗分化率的提高。  相似文献   
52.
S. Y. Lin  H. Ikehashi 《Euphytica》1993,67(1-2):35-40
Summary A locus for male gamete abortion in hybrids for Japonica and Indica rice was identified with the aid of marker genes Rc and Est-9 on chromosome 7. In an Indica-Japonica cross, AKAMAI 1/IR50, the Indica allele Est-9 2 was transmitted via the male gamete with a ratio of 0.29 instead of the normal 0.5, whereas no segregation distortion was observed for the Rc locus. The recombination value (p) for Est-9 and Rc was estimated to be 0.38 by a least square method after adjusting Mendelian segregation ratios with the male transmission ratios of 0.29 (Tr) for Est-9 2 and 0.71 (1-Tr) for Est-9 1. The recombination value (q) for the new locus for male gamete abortion, ga-11, and Est-9 was estimated to be 0.23 by using 56 F3 lines from F2 plants which were heterozygous for the Est-9 locus. No linkage for Rc and ga-11 was found. Therefore, the two markers and ga-11 were located in the order of ga-11-Est-9-Rc. Using the estimated recombination value (q), the male transmission rate (k) of ga-11 a was estimated to be 0.11 with the F2 data and-0.07 with the F3 line data. Thus, it was apparent that male gametes possessing ga-11 a were frequently aborted in the Indica-Japonica hybrid.  相似文献   
53.
When the flowers are not disturbed, the yield of F1 hybrids of faba beans normally exceeds that in their inbred parents. The basis of this “heterotic autofertility” was investigated by examining flowers for pollination and fertilization throughout the flowering season and assessing the distribution of seeds and pods on mature plants. Six inbred lines and seven of their F1 hybrids were grown without protection from bee visitation, and their autofertility was estimated’ by comparing their fertilization with that of cytoplasmic male-sterile line. The first direct evidence was obtained that heterotic autofertility acts by increasing; the proportion of flowers which were pollinated and fertilized. The autofertility was not perfect, especially in a closed-flower hybrid, as many ovules remained unfertilized. Several factors contributed to the number of seeds per pod in F1 hybrids, being superior to parental means: (1) more ovules per flower, (2) greater fertilization of the basal ovules, (3) reduced abortion of the apical ovules and (4) greater overall maturation ovules.  相似文献   
54.
在花药培养技术上,通过49个组合400个幼穗1200个颖花的研究,提出了依据植株和颖花形态判断花粉发育时期的具体指标;通过低温预处理和双态双层法提高花药力的方法。在花培育种遗传规律的研究上,对株高和叶瘟抗性的结果表明:F2的分布倾向于晚熟、高秆及抗病,即倾向于亲本的显性性状,而H2的分布则均匀对称,其中早熟、矮秆及感病植株的比例较F2高。在选择效率上,花培育成的审定品种的选择效率为0.93%,是同期常规育成审定品种选择效率0.28%的3.32倍。通过上述研究培育出了8个花培新品种,并且在品质、抗性、产量等方面表现突出,成为寒地稻区主栽品种,并讨论了水稻花培育种今后的发展方向。  相似文献   
55.
Pollen characteristics, inheritance and allelism of 23 genetic male-sterile (ms) mutants of rice (Oryza sativa L.) were investigated. Ten of the mutants were induced by ethyl methane sulfonate, one induced by ethyleneimine, seven induced by gamma rays, one induced by streptomycin, one derived from tissue culture and three were spontaneous mutants found in the field. Four pollen abortion types were observed among these ms mutants: 3 no-pollen (NP) type, 6 complete pollen abortion (CPA) type, 13 partial pollen abortion (PPA) type, and 1 stainable pollen abortion (SPA) type. Progeny tests over two years indicated that each of the mutants was inherited as a monogenic recessive. A partial diallel cross among the 23 ms mutants indicated that mutant E2 was allelic to G4, E5 was allelic to E9, N2 was allelic to N3, and that three other mutants, E3, G6 and T1, shared the same ms locus. Gene symbols ms-46 (t) through ms-63 (t) were assigned to these mutants.  相似文献   
56.
Summary When Asiatic lilies are forced during the winter period, additional light is needed to prevent flower bud abscission and flower bud blasting. Growth room experiments showed considerable differences among eight lily cultivars in their response to low light. Among these cultivars, Connecticut King and Enchantment appeared to be the most sensitive to low light conditions while Uncle Sam and Scout were the least sensitive.Analysis of an incomplete diallel cross between nine cultivars showed significant differences in general combining ability (GCA) for flower bud abortion, number of buds, forcing time, plant height and leaf scorch under winter greenhouse conditions. Enchantment had the highest positive GCA for bud abortion, indicating a high sensitivity to low light conditions. Uncle Sam had the lowest GCA. Pirate and Scout appeared to have a high GCA for sensitivity to leaf scorch. Connecticut King was found to be a probable source of cytoplasmic male sterility. The data suggest that male sterility is associated with better response to low light conditions.  相似文献   
57.
通过不同浓度的镰刀菌毒素对离体培养的小麦花药进行胁迫,结果表明,随着胁迫浓度的增加,小麦花药培养效率迅速下降,具体表现在降低培养花药的反应率、愈伤组织诱导率、绿苗分化率及相对培养白苗率四方面。毒素的这种效应,因供试材料基因背景的不同而有一定差异,相对而言,感病品种和含感病基因的杂种花药对毒素较为敏感。  相似文献   
58.
 以ATPase定位研究了红莲型粤泰不育花药和可育花药。结果表明 ,单核中位期可育花粉ATPase定位于覆盖层外侧、柱状层和细胞核 ,单核边位期ATPase定位于覆盖层外侧和细胞核 ;二核期ATPase定位于柱状层、内壁、质膜以及细胞核上 ;三核期ATPase定位于柱状层、内壁、质膜生殖核和营养核的核仁上。单核中位期不育花粉ATPase定位于核仁 ,单核边位期ATPase定位于覆盖层外侧、柱状层、质膜以及细胞核上 ;二核期不育花粉ATPase定位于覆盖层外侧、内壁和核仁。单核中位期可育花药药壁发育良好 ,绒毡层吞噬泡有活跃的ATPase活性 ,单核边位期绒毡层内吞噬泡消失 ,绒毡层内含物减少 ,二核期绒毡层细胞完全解体。单核中位期不育花药药壁发育不良 ,绒毡层内吞噬泡少 ,单核边位期绒毡层出现大量吞噬泡 ,二核期绒毡层存在尚未解体的细胞质和核。大多数不育花药药隔结构及ATPase定位特征与可育花药相似。可能不育花药绒毡层发育迟缓、单核边位期不育花粉细胞质膜活跃的ATPase活性及花粉核异常与花粉败育存在较为密切的关系。  相似文献   
59.
 利用普通光学显微镜和透射电子显微镜研究了新发现的玉米细胞质雄性不育材料WBMs的小孢子败育过程。观察到Mo17cms-WBMs的小孢子在单核花粉中期以前发育正常,部分小孢子从单核花粉晚期质核出现异常,多数小孢子可正常发育到二核花粉期,随后开始崩溃,形成空瘪皱缩的花粉粒。雄性不育材料WBMs胞质的小孢子败育过程与S组唐徐胞质不育材料类似,败育发生晚,绒毡层等体细胞活动正常,属典型的配子体不育类型。  相似文献   
60.
枇杷花药培养诱导愈伤组织的研究   总被引:7,自引:0,他引:7  
陈红  王永清 《安徽农业科学》2007,35(27):8453-8454
为了寻找枇杷花药愈伤组织诱导的最佳条件及配方。以枇杷花药为试验材料,采用完全组合设计研究了温度、蔗糖浓度、激素对花药愈伤组织诱导的影响。低温处理对愈伤组织的形成没有多大影响,随着低温时间的延长,愈伤组织诱导率低于对照;30 g/L蔗糖诱导花药愈伤组织的效果较好,诱导率为62.5%;在附加1 mg/L 2,4-D和2 mg/L 6-BA的MS培养基上,诱导率最高,为90.00%;MS+0.25mg/L6-BA+1 mg/LNAA最有利于愈伤组织的增殖。高浓度的蔗糖不利于愈伤组织的形成。一定浓度的2,4-D和6-BA对枇杷花药愈伤组织的诱导有较大的影响,且2,4-D起着主导作用。  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