全文获取类型
收费全文 | 608篇 |
免费 | 31篇 |
国内免费 | 23篇 |
专业分类
林业 | 68篇 |
农学 | 172篇 |
17篇 | |
综合类 | 224篇 |
农作物 | 63篇 |
水产渔业 | 23篇 |
畜牧兽医 | 19篇 |
园艺 | 72篇 |
植物保护 | 4篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 11篇 |
2019年 | 24篇 |
2018年 | 13篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 18篇 |
2014年 | 23篇 |
2013年 | 27篇 |
2012年 | 46篇 |
2011年 | 37篇 |
2010年 | 31篇 |
2009年 | 25篇 |
2008年 | 33篇 |
2007年 | 41篇 |
2006年 | 24篇 |
2005年 | 33篇 |
2004年 | 20篇 |
2003年 | 19篇 |
2002年 | 17篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 12篇 |
1997年 | 14篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 11篇 |
1993年 | 8篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 5篇 |
1987年 | 3篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1955年 | 3篇 |
排序方式: 共有662条查询结果,搜索用时 0 毫秒
61.
Immature zygotic embryos of the sunflower inbred line ‘Ha 300’, cultivated on a modified MS medium containing 6-benzyladenine and a high amount of sucrose, regenerated fertile plants via direct somatic embryogenesis. Plant regeneration from immature sunflower embryos is generally characterized by a relatively high experimental variability resulting from the interactions of multiple factors. We present here a study of some of the factors acting on the donor plants and their influence on the capacity to regenerate plants. Repeated experiments during a 2-year period with greenhouse-grown as well as field-grown plants led to the following conclusions: (i) The use of pesticides, unavoidable in the greenhouse, is compatible with routine regeneration of fertile plants, (ii) The plant growth retardants tested were useful for the production of healthy plants in the greenhouse and had no effect on the regeneration capacity. 相似文献
62.
不结球白菜小孢子胚胎发生过程及发育途径研究 总被引:3,自引:0,他引:3
采用FDA荧光染色法对小孢子游离培养的发育过程进行了观察。结果表明:不结球白菜花粉母细胞减数分裂释放出的小孢子发育到单核靠边期及稍后时期染色最深、活力最强。多数游离小孢子培养经历的发育过程与合子胚相似,并且胚胎发育迅速,6~9 d产生大量球型胚,13 d开始出现子叶型胚胎。小孢子胚胎发育途径既有对称分裂并产生胚胎的途径(B途径),也有第1次不对称有丝分裂的方式;第1次不对称分裂后,既有营养细胞单独发育成胚的现象(A途径),也有营养细胞和生殖细胞共同发育成胚的现象(E途径),但未发现生殖细胞单独发育成胚的现象。 相似文献
63.
Nickel (0.13, 0.25, 0.5, 1.0 and 1.5 mg/l) increased the efficiency of somatic embryogenesis in leaf base and mesocotyl derived
calli of Setaria italica. A lower concentration of nickel in the culture media promoted long-term maintenance of embryogenic
calli that regenerated into plantlets. The plants obtained from embryogenic calli grown on Ni-containing medium showed tolerance
to nickel. The growth of embryogenic callus was the maximum at 1.5 mg/l as compared to a lower or a higher concentration of
Ni. Use of nickel may help in the induction of high frequency somatic embryogenesis in Setaria italica.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
64.
Efficient shoot regeneration and somatic embryogenesis from immature cotyledons of Brassica napus L. 总被引:1,自引:0,他引:1
Immature cotyledons of Brassica napus cv.‘Topas’ were used to investigate the effects of various naphthaleneacetic acid and benzylaminopurine concentrations on morphogenesis in vitro. A high efficiency of adventitious shoot regeneration and somatic embryogenesis was achieved on Murashige and Skoog medium supplemented with the above growth regulators. Two types of somatic embryogenesis were obtained, the first directly and the second via a callus stage. 相似文献
65.
[目的]探讨miR396在落叶松体细胞胚胎发生中的功能.以期该研究能为解决体胚发育中子叶畸形胚与生根率低的问题提供新的视角,同时也为进一步揭示体胚发育的分子调控网络做基础铺垫.[方法]构建pre-miR396超表达载体,通过农杆菌介导侵染,将pre-miR396转入落叶松胚性细胞中,筛选稳定抗性细胞系.在DNA与RNA水平上,对抗性细胞系进行的鉴定、检测,同时统计比对其与野生细胞系间发芽率、叶片数目以及生根率的差异.[结果]在抗性细胞系基因组中,扩增出HTP与miR396的特异性片段,且无农杆菌Virg基因片段.RNA表达水平上,抗性系pre-miR396与miR396表达皆增加,而靶基因LaGRFs的表达量下调.统计表明抗性系胚的发芽率、生根率、叶片数目畸形率分别为70.60%、0.60%、37%,而野生型分别为92.50%、10.55%、4%,抗性系胚的发芽率、生根率显著降低(Sig.=0.000),叶片数目畸形率显著增加(Sig.=0.000).[结论]miR396在落叶松体细胞胚胎发生过程中,可能通过负调节靶基因LaGRFs的表达或者通过LaGRFs影响与它相互作用的基因,参与体胚子叶原基细胞代谢,从而影响了子叶与叶片的发育;通过负调节LaGRFs或者其它与根部发育相关的靶基因,影响了根端分生区细胞的活动,参与调控根的发育. 相似文献
66.
67.
The Effect of Carbohydrate Composition and Concentration on Anther Culture Response in Barley (Hordeum vulgare L.) 总被引:5,自引:0,他引:5
Culture medium composition is critical for the successful induction of microspore division in vitro. The present experiments have focused on a relatively neglected area of cell and tissue culture research, namely the carbohydrate component used in the medium. Three spring barley genotypes were cultured on a medium which was modified by replacing sucrose with the following carbohydrates (6 % w/v): maltose, fructose, malt extract, galactose and a glucose (3 % w/v)/fructose (3 % w/v) mixture. Both maltose and malt extract were superior to sucrose in their capacity to induce green plantlet differentiation from microspores. The concentrations of both sucrose and maltose were also varied. Overall the response of anthers on maltose based media was higher than on sucrose based media. Furthermore, a concentration of maltose m the range 6—12 % w/v produced a higher frequency of green plants than a low concentration (1—3 % w/v). The effect of maltose based media on germplasm of direct relevance to barley breeders was also tested. The cultivar ‘Blenheim’ was shown to be very responsive and this genetic factor was transmitted to the F1 hybrid. The frequency of haploid to diploid regenerants was not consistent over genotypes, but in general there were more haploid than diploid regenerants. The implications of these results for barley breeding are discussed. 相似文献
68.
影响葡萄花药愈伤组织产生和分化频率的因素 总被引:9,自引:1,他引:9
葡萄花药培养能产生体细胞胚。体细胞胚的诱导及其频率高低与材料基因型、培养基和培养条件有关。试验结果表明,对花药进行低温和药物处理不能明显地促进体细胞胚胎发生,但通过改进培养基成份,添加AgNO_3和用液-固培养均能促进葡萄花药胚性愈伤组织的产生。供试的14个基因型材料中仅有3个能产生体细胞胚,而体细胞胚仅部分能萌发成正常苗。 相似文献
69.
70.