全文获取类型
收费全文 | 306篇 |
免费 | 21篇 |
国内免费 | 39篇 |
专业分类
林业 | 12篇 |
农学 | 75篇 |
基础科学 | 2篇 |
19篇 | |
综合类 | 93篇 |
农作物 | 33篇 |
水产渔业 | 8篇 |
畜牧兽医 | 103篇 |
园艺 | 14篇 |
植物保护 | 7篇 |
出版年
2024年 | 4篇 |
2023年 | 7篇 |
2022年 | 6篇 |
2021年 | 19篇 |
2020年 | 7篇 |
2019年 | 12篇 |
2018年 | 9篇 |
2017年 | 11篇 |
2016年 | 23篇 |
2015年 | 18篇 |
2014年 | 22篇 |
2013年 | 23篇 |
2012年 | 17篇 |
2011年 | 27篇 |
2010年 | 15篇 |
2009年 | 12篇 |
2008年 | 16篇 |
2007年 | 5篇 |
2006年 | 12篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 11篇 |
2002年 | 6篇 |
2001年 | 2篇 |
2000年 | 5篇 |
1999年 | 3篇 |
1998年 | 6篇 |
1997年 | 3篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1983年 | 1篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1962年 | 1篇 |
排序方式: 共有366条查询结果,搜索用时 31 毫秒
11.
以二级相变铁电材料为例,利用推广的Ginzburg-Landau-Devonshire(GLD)理论,研究不均匀结构对梯度铁电薄膜性质的影响.结果表明:退极化场对于两层薄膜中间的极化影响较小,而在薄膜的两端处影响最大;梯度铁电薄膜的平均极化随膜厚按线性规律变化;在接近相变温度时,自发极化消失,梯度铁电薄膜的这一现象与铁电材料的性质相同.在外场不等于零的情况下,得到的梯度铁电薄膜的电滞回线中心对称. 相似文献
12.
本研究以山丹新麦草为材料,通过秋水仙素处理萌动种子、胚芽、二倍体植株幼苗染色体加倍研究,探讨了不同诱变材料的适宜处理浓度和时间,从而比较出最适宜的染色体加倍方法。结果显示:最好的加倍方法是用0.1%的秋水仙素溶液处理二倍体幼苗24h诱变率最高,为62.5%。 相似文献
13.
14.
Efficient production of doubled haploid Brassica napus plants by colchicine treatment of microspores 总被引:7,自引:0,他引:7
Summary The effect of colchicine on isolated microspore cultures of Brassica napus was evaluated in order to combine a positive effect of colchicine on the induction of embryogenesis with the possibility to induce chromosome doubling at an early developmental stage, thus avoiding the production of haploid or chimeric plants. Colchicine was added to the culture medium immediately after isolation of B. napus microspores. The cultures were incubated from 6 to 72 h with various concentrations of colchicine. Samples were taken from the regenerating embryoids after 6 weeks for ploidy determination by flow-cytometry.The highest diploidization rate was obtained after a 24 h treatment of microspores with 50 mg/l colchicine, leading to 80–90% diploid embroids. A concentration of 100 mg/l colchicine applied for the same duration resulted in a lower diploidization rate (76–80%). Treatment durations of 6 h were not long enough to induce a high rate of diploidization, whereas the application of 10 mg/l for 72 h was also very effective.A sample of the plants regenerated from the colchicine treated microspores was transferred to the greenhouse. The plants looked similar to normal diploid rapeseed plants and showed reasonable pod and seed set. Thus, an additional generation for seed increase in the greenhouse is rendered unnecessary. The advantage of applying a minimum volume of colchicine under controlled in vitro conditions means a considerable saving of time and labour in DH-breeding programs. 相似文献
15.
Oryzalin as an Efficient Agent for Chromosome Doubling of Haploid Apple Shoots in vitro 总被引:4,自引:0,他引:4
In an outbreeding species such as apple, haploid plants may be especially useful in breeding programmes for the production of homozygous material. However, methods must be available to induce chromosome doubling in the haploid plants. Two antimitotic agents, colchicine and oryzalin, were compared as regards their efficiency in inducing chromosome doubling of in vitro haploid apple shoots. Three colchicine levels (0.025, 0.25 and 1.25 mM) and three oryzalin levels (5, 15 and 30 μM) were evaluated. Three techniques were also used and compared. Survival rate and chromosome counts were determined. Differences were observed between the two antimitotic agents and between the three techniques. This study demonstrates that oryzalin could be a better choice than colchicine for chromosome doubling on haploid apple shoots in vitro. 相似文献
16.
Colchicine-induced chromosome doubling in Platanus acerifolia and its effect on plant morphology 总被引:1,自引:0,他引:1
We report the production of tetraploid plants of Platanus acerifolia, with the ultimate aim of improving the ornamental qualities of this important urban landscaping tree. Chromosome doubling
was achieved by the application of colchicine to either pre-soaked seed or to the apical meristems of young seedlings. Treatment
of the ungerminated seed was the more efficient method in terms of numbers of tetraploid seedlings (up to 40%, as determined
by chromosome counting of the root-tip nuclei) but this method produced no mature tetraploid plants due to the deleterious
effect of colchicine on subsequent root growth. When colchicine was applied directly to the apical growing tip of cotyledon-stage
seedlings, leaf and stem growth was temporarily affected but the plants eventually recovered. We conducted a preliminary screen
for putative tetraploids based on the observation in other plant species of a correlation of stomatal size and distribution
with ploidy. Plants containing significantly larger stomata and at a lower density across the lower leaf epidermis, were selected
for further analysis by flow cytometry and chromosome counting. These techniques confirmed that, of the 12 putative polyploids,
four were tetraploid, five were mixoploid and three were, in fact, diploid. Morphological differences of the tetraploids included
a more compact growth habit and broader, thicker leaves. These plants are being grown to full maturity in order to test their
potential for use in a breeding programme aimed at producing sterile triploid lines. 相似文献
17.
In cereals, chromosome doubling of microspore-derived haploid plants is a critical step in producing doubled haploid plants.
This investigation was undertaken to study the effect of incorporation of colchicine in the induction medium for anther culture,
and the effect of colchicine on anther culture-derived plants of triticale grown under controlled greenhouse conditions. In
the latter case, chromosome doubling of adult sterile plants derived from anther culture of fourteen triticale populations
was attempted, where androgenetic plants with non-dehiscent anthers were cloned and subjected to the colchicine treatment,
and then grown with the aid of hydroponics. The hydroponic system provided optimal conditions for recovery of the affected
haploids from the toxic effects of colchicine treatment and all colchicine-treated plants survived. A topcross-F1 (TC1F1) population with timopheevii cytoplasm produced the highest percentage of plants with seed-set either due to chromosome doubling
by colchicine (98%) or spontaneous doubling of chromosome number (15%). Colchicine-treated anthers performed inferior than
control in both induction and regeneration phases. One of the key observation of this study was the reversal from reproductive
stage back to the vegetative stage which in turn enabled further cloning of haploid plants under hydroponic conditions once
they were identified as sterile. The one hundred percent survival rate of in vitro-derived plants, 100% survival rate of colchicine treated haploid plants and the high chromosome doubling success rate (X
= 82.3) observed in this study imply that a temperature-controlled greenhouse with an hydroponic system provides an efficient
environment for inducing chromosome doubling of haploid plants in cereals.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
C. Lanaud 《Plant Breeding》1987,99(3):187-195
Ovule and pollen fertility have been studied in doubled haploids of cocoa derived from spontaneous haploids, doubled by colchicine treatment. The two measures of fertility were very variable; occasionally, the levels were as high as those of the parent plant, but most were lower. The low fertility was not improved either by changing pollinators or after grafting. Pollen fertility also varied seasonally more in doubled haploids than in their parents. The lack of differentiation of embryo sacs seemed to be the cause of low values of ovule fertility. Both of these unfavourable characteristics were not observed in the progeny of doubled haploids, The low fertility is described in terms of homozygote depression, forced, on normally allogamous plants, its consequences for the use of doubled haploids in the production of hybrid seeds are discussed. 相似文献
19.
20.
鲢人工雌核二倍体群体的产生及其遗传分析 总被引:3,自引:0,他引:3
选用遗传失活兴国红鲤的精子作为雌核发育激活源 ,成功地诱导了鲢雌核发育并获得 3个自然加倍的雌核发育二倍体群体。鲢的单倍体诱导率最高达 96 .9% ,自然加倍率最高达 0 .4 4 3%。经分析鉴定 ,雌核发育单倍体胚胎具有 2 4条染色体。而鲢的染色体为 4 8,兴国红鲤为 10 0。雌核二倍体鲢都具有 2套完整的母本染色体 (2n =4 8) ,外部形态性状与亲本鲢完全相同。这些结果表明 ,雌核发育后代的遗传物质来源于母本 ,无父本遗传物质参与。 相似文献