全文获取类型
收费全文 | 773篇 |
免费 | 26篇 |
国内免费 | 67篇 |
专业分类
林业 | 15篇 |
农学 | 90篇 |
基础科学 | 2篇 |
13篇 | |
综合类 | 270篇 |
农作物 | 84篇 |
水产渔业 | 28篇 |
畜牧兽医 | 235篇 |
园艺 | 127篇 |
植物保护 | 2篇 |
出版年
2023年 | 4篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 22篇 |
2019年 | 9篇 |
2018年 | 4篇 |
2017年 | 6篇 |
2016年 | 16篇 |
2015年 | 19篇 |
2014年 | 16篇 |
2013年 | 37篇 |
2012年 | 56篇 |
2011年 | 47篇 |
2010年 | 30篇 |
2009年 | 56篇 |
2008年 | 47篇 |
2007年 | 58篇 |
2006年 | 77篇 |
2005年 | 56篇 |
2004年 | 52篇 |
2003年 | 29篇 |
2002年 | 24篇 |
2001年 | 27篇 |
2000年 | 16篇 |
1999年 | 20篇 |
1998年 | 15篇 |
1997年 | 9篇 |
1996年 | 11篇 |
1995年 | 12篇 |
1994年 | 15篇 |
1993年 | 13篇 |
1992年 | 14篇 |
1991年 | 10篇 |
1990年 | 10篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有866条查询结果,搜索用时 765 毫秒
21.
Production of inter-section hybrids between Primula filchnerae and P. sinensis through ovule culture
Inter-section hybrids were obtained in the reciprocal crosses between Primula filchnerae (2n = 2x = 24) of Sect. Pinnatae and P. sinensis ‘Fanfare’ (2n = 2x = 24) of Sect. Auganthus by rescuing ovules on half-strength (1/2) Murashige and Skoog's (MS) medium supplemented with 50 g l−1 sucrose, 2.5 g l−1 gellan gum, 0.1 mg l−1 α-naphthaleneacetic acid (NAA), 0.1 mg l−1 6-benzyladenine (BA) and 50 mg l−1 gibberellic acid (GA3). In ovule culture, germination occurred with radicle elongation but no plumule was observed. The radicle kept on the initial medium showed root proliferation with callus formation. When the calluses were transferred to (1/2)MS media containing 30 g l−1 sucrose and 3 g l−1 gellan gum, without plant growth regulators (PGRs) or with 1 mg l−1 zeatin and 0.1 mg l−1 NAA, plantlets were regenerated. The plants thus obtained were confirmed to be hybrids through flow cytometry (FCM) and random amplified polymorphic DNA (RAPD) analyses. The hybrid obtained when P. filchnerae was used as the maternal parent was diploid, whereas hexaploid hybrid was obtained when using P. sinensis as the maternal parent. The hexaploid hybrid might be produced through chromosome doubling of a triploid originated from the fertilization of P. sinensis with unreduced pollen of P. filchnerae. 相似文献
22.
杏胚珠培养及幼胚子叶不定芽诱导研究 总被引:2,自引:1,他引:2
以盛花后25、35、50、55、60d的凯特杏胚珠为外植体,研究胚珠培养的适宜条件;选择发育一致的幼胚子叶,研究不定芽的发生条件。结果表明,SH培养基是凯特杏胚珠培养的适宜培养基;盛花后25d的凯特杏胚珠(PF=0),仅采用生长培养不足以发育成可见胚,试验采用诱导方式获得了可见胚,诱导出胚率为80%;以MS为基本培养基,BA与NAA结合诱导能力强;但这种胚小且瘦弱,继续生长培养,利用幼胚子叶诱导不定芽。在幼胚子叶诱导不定芽方面,盛花后25、35d取样的凯特杏胚珠,培养后获得幼胚子叶,诱导不定芽的适宜TDZ质量浓度为1.25mg/L,诱导出芽率分别为85.00%、80.00%;盛花后50、55d取样的材料,适宜TDZ质量浓度为2.50mg/L,出芽率分别为65.00%、60.00%,而盛花后60d取样的材料,适宜TDZ质量浓度为5.0mg/L,出芽率为61.11%,不定芽主要发生在子叶的近轴面、胚轴连接处及子叶近轴端两侧;在相同培养基中,25℃进行21d暗培养,盛花后35、50、55、60d材料出芽率分别为72.22%、65.00%、60.00%、55.56%;4℃下28d暗培养,35、50、55、60d依次为59.09%,71.42%、77.78%、86.36%;对不定芽进行伸长、生根与快繁培养,获得了健康正常的植株。通过以上研究,建立了凯特杏幼胚4级培养体系,即(1)胚珠培养,获得可见胚(1级培养);(2)幼胚生长培养(胚培养),获得了健壮幼胚(2级培养);(3)幼胚子叶再生,获得不定芽(3级培养);(4)不定芽组培苗快繁(4级培养)。 相似文献
23.
送春与多花兰杂种的非共生萌发与快速繁殖 总被引:3,自引:0,他引:3
用地生兰送春和附生兰多花兰进行种间杂交,对杂交种子进行非共生萌发和快速繁殖研究.结果表明:胚龄7个月、0.1 mol/L KOH处理10 min的种子萌发率最高;种子萌发后原球茎的增殖以Z4 (KC+BA 0.4 mg/L+NAA 0.6 mg/L+KT 0.2 mg/L ) 培养基为最好,增殖系数可达到12.8;在原球茎增殖和分化成苗过程中加入活性碳能够有效地防止切口褐化. 相似文献
24.
《Scandinavian Journal of Forest Research》2012,27(3):221-237
In order to enhance cone production in Norway spruce [Picea abies (L.) Karst] seed orchards have been established in more southerly, warmer sites in Norway. This has led to concern and some evidence that seedlings obtained from parent trees grown at warmer sites may not be well adapted if planted in northern regions. Selective events during sexual reproduction in the warmer climate may select for traits not well adapted for cold climates. This study describes ovule and male gametophyte development, fertilization and proembryo and early embryo development under six different temperature regimens of warm or cold, warm-cold or cold-warm, and compares development in relation to temperature sums in degree days (dd) and calendar date. The outside treatment in a cold climate in Norway served as the control, and normal development and few ovule abortions and abnormalities were observed. In no treatments were abnormalities in male gametophyte development observed. In treatments in which trees were kept in the greenhouse throughout the study or moved during the study from the outside to inside the greenhouse, a higher incidence of megagametophyte, egg or embryo abortion was generally observed. 相似文献
25.
26.
枣授粉受精及胚胎发育研究 总被引:5,自引:0,他引:5
The processes about pollination, fertilization and embryo development of Chinese Date ‘Wu-he-zao‘ (ziziphus jujuba) were observed by means of lightmicrocope combining histochemical dyeing and fluorescent technique. The results were summarized as follows:The pollen grains germinated on the stigma at the 4th hour after pollination. On the 5th day after pollination,the primary endosperm nucleus formed, and the zygote formed on the 6th day. The double fertilization of Wu-he-zao was the type premitotic syngamy. The first division of the zygote took place after a dormancy for about 6 - 7 days. The proembryonal development of Wu-he-zao belonged to the Solanad type. The development of the endosperm belonged to the nuclear type. 相似文献
27.
Somatic embryogenesis in Chamaecyparis pisifera Sieb. et Zucc. was initiated from immature seeds collected from the end of June to early July. Mass propagation through adventitious
shoot bud production from somatic embryo culture on Woody Plant (WP) medium and artificial seed production using sodium alginate
was achieved. A high bud forming index value (25.8) was obtained on medium supplemented with 1 μM 6-benzylaminopurine. The conversion rates from artificial seeds under aseptic and nonaseptic conditions were 60%–100% and
10%–12%, respectively. For germplasm conservation, somatic embryos and embryogenic cells were successfully stored at 4°C (medium-term
storage) and in liquid nitrogen for long-term storage.
Received: December 21, 2001 / Accepted: August 1, 2002
Acknowledgments This work was supported in part by the Japan Science and Technology Corporation and in part by a Grant for Research for the
Future Program from the Japan Society for the Promotion of Science.
Correspondence to:E. Maruyama 相似文献
28.
29.
筇竹组培快繁技术 总被引:1,自引:0,他引:1
以筇竹种胚为外植体,MS为基本培养基,通过无菌体系的建立、丛芽诱导增殖、生根培养研究其组培技术,筛选移栽介质。结果表明:在组培无菌条件下,采用体积分数0.5%甲醛(12 h)→体积分数75%酒精(15 min)→体积分数0.1%升汞(8 min)的处理效果较为理想,筇竹种胚污染率为3.33%,萌芽率为86.21%,成活率为83.33%;筛选出MS+2.0 mg·L^-16-BA+0.2 mg·L^-1NAA适合筇竹种胚的丛芽诱导;1/2MS+0.3 mg·L^-1NAA+1.0 mg·L^-1KT+1.0 mg·L^-16-BA适合筇竹分化丛芽增殖;1/2MS+0.3 mg·L^-16-BA+2.0mg·L^-1NAA+0.1 mg·L^-1IBA适合筇竹的生根培养;m(河沙)∶m(珍珠岩)∶m(腐殖土)=1∶1∶2的基质为最佳移栽质量配比。 相似文献
30.
温度和盐度对花鲈胚胎及前期仔鱼发育影响的初步报告 总被引:30,自引:0,他引:30
花鲈(Lateolabrax japonicus)胚胎发育的适宜温度为10~22℃,10℃组中的畸形率偏高,因此最适宜温度为13~22℃。短时期的7℃低温对胚胎发育没有影响;前期仔鱼的适温范围与胚胎的适温范围基本一致。胚胎发育的适宜 盐度为19‰~28‰,以22‰~25‰为最佳;仔鱼对盐度的要求与胚胎期近似。以低盐度和高盐 度相比较,4日龄以后,低盐度似有利于仔鱼存活。 相似文献