全文获取类型
收费全文 | 3875篇 |
免费 | 156篇 |
国内免费 | 224篇 |
专业分类
林业 | 9篇 |
农学 | 1198篇 |
基础科学 | 8篇 |
344篇 | |
综合类 | 1595篇 |
农作物 | 529篇 |
水产渔业 | 3篇 |
畜牧兽医 | 30篇 |
园艺 | 317篇 |
植物保护 | 222篇 |
出版年
2024年 | 5篇 |
2023年 | 41篇 |
2022年 | 86篇 |
2021年 | 106篇 |
2020年 | 96篇 |
2019年 | 134篇 |
2018年 | 115篇 |
2017年 | 112篇 |
2016年 | 137篇 |
2015年 | 130篇 |
2014年 | 160篇 |
2013年 | 178篇 |
2012年 | 241篇 |
2011年 | 271篇 |
2010年 | 190篇 |
2009年 | 184篇 |
2008年 | 193篇 |
2007年 | 230篇 |
2006年 | 183篇 |
2005年 | 196篇 |
2004年 | 139篇 |
2003年 | 121篇 |
2002年 | 103篇 |
2001年 | 97篇 |
2000年 | 58篇 |
1999年 | 79篇 |
1998年 | 68篇 |
1997年 | 58篇 |
1996年 | 57篇 |
1995年 | 45篇 |
1994年 | 52篇 |
1993年 | 63篇 |
1992年 | 52篇 |
1991年 | 47篇 |
1990年 | 55篇 |
1989年 | 46篇 |
1988年 | 25篇 |
1987年 | 24篇 |
1986年 | 17篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 6篇 |
1981年 | 7篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1962年 | 6篇 |
1955年 | 4篇 |
排序方式: 共有4255条查询结果,搜索用时 18 毫秒
101.
通过种子培养方法提高油菜贮藏种质发芽率及成苗率 总被引:1,自引:0,他引:1
以在昆明自然贮藏条件下贮藏了1a-17a的甘蓝型油菜种子为材料,探讨通过种子培养方法来获得比常规方法高的发芽率和成苗率。试验结果表明:通过种子培养方法能有效提高贮藏种质的发芽率和成苗率,发芽率比对照提高0%-25%,成苗率提高0%-25.6%。 相似文献
102.
核不育油菜试管外无性繁殖系数为8~10株/月·苗,远远高于试管繁殖,变异频率低。腋芽在土壤中生根较为适宜的激素浓度为IBM100mg/L或NAA100mg/L,处理时间4~5h,在成都较为适宜的生根时间为10~11月。借腋芽繁殖1~3代的再生植株,不经春化即可开花;继代4~5次后的无性系则需春化才能开花;愈伤组织再生的植株,必须经春化才能开花。经腋芽繁殖的再生植株,其主要农艺性状与供体植株的有性后代无明显差异;而愈伤组织再生植株的整齐度及一些主要农艺性状与供体植株有较大的差异。 相似文献
103.
104.
Summary Effects of temperature and daylength on the bolting of a number of B. campestris accessions were investigated both in the open and in the IVT phytotron. From the results it was concluded that low temperature and genotype are the predominant factors with respect to bolting. Daylength has rather limited influence. One cultivar bolted more than 12 weeks earlier at 10 and 14°C than at 18°C. On the other hand some cultivars did not require vernalization at all.At 14°C and short daylength, depending on genotype, the period of time between sowing and 50% bolting ranged from 8 to 30 weeks. At this temperature the stimulating effect of long day (24 h), depending again on the genotype, ranged from 0 to 4 weeks. The genotypes most resistant to bolting appeared to be the stubble turnips (B. campestris ssp. rapa).In terms of seed(ling) vernalization at 5°C the cold requirement ranged from 0 to more than 3 weeks, depending on the genotype. The required vernalization periods at 5°C can be used as a criterion in screening for resistance to bolting. 相似文献
105.
Summary Interspecific hybrids have been obtained in an otherwise incompatible cross betweenBrassica juncea × Brassica hirta through the in vitro culture of hybrid ovules and ovaries. The best response was observed from ovules and ovaries cultured 10–15 and 5–7 days after pollination respectively on a basal medium supplemented with indoleacetic acid, kinetin and casein hydrolysate. In some cases the basal cut end of the ovaries proliferated to form callus and shoots. The in vitro-derived hybrid seeds varied in their colour, size and shape, and the F1 plants in the field showed a large diversity in their morphological traits. The hybrids were sterile, and had an intermediate number of chromosomes (2n=30). 相似文献
106.
Genetic analyses of agronomic and seed quality traits of doubled haploid population in Brassica napus through microspore culture 总被引:1,自引:0,他引:1
Summary The results showed that the F1 genotype from the cross (Brassica napus cv. Zheshuang 758 × cv. Z-4115) had good response to embryogenesis, and their embryo yield and rate of plant regeneration reached 69.8 embryo/bud and 46.9%, respectively. Characters from the doubled haploid (DH) populations in B. napus were analyzed and it was showed that the means of each agronomic trait were between their parents, but they were nearer to the paternal in 6 agronomic traits (plant height, branch position, number of pods in the main raceme, length of pod, number of pods/plant and number of seeds/pod). The number of genes controlling each agronomic trait was analyzed based on the DH populations. The results showed that the number of genes controlling number of pods in the main raceme was the highest (15.6), and the least number of genes was involved for stem width (only 7.9). According to estimated coefficients of skewness and kurtosis of the traits tested, gene interaction was found to be absent for stem width, plant height, length of main raceme, number of primary and secondary branches, pod density in the main raceme and seed weight/plant. Complementary interaction was also observed in five agronomic traits (number of pods in the main raceme, length of pod, number of pods/plant, number of seeds/pod and 1000-seed weight). A significantly positive correlation was observed between seed yield/plant and four agronomic traits (length of main raceme, length of pod, number of pods/plant and 1000-seed weight). The experiment also showed that the erucic acid, glucosinolate, oil and protein contents of DH populations were 34.23%, 87.09 μmol/g, 44.09% and 42.67%, respectively. The numbers of genes controlling each quality trait were 7.8, 9.7, 9.4 and 8.7, respectively. Partial correlations between the seed quality traits and the agronomic characters of DH populations were analyzed. In this experiment, the partial correlations among seed quality traits were also analyzed and it was found that the oil content had a negative correlation with the other three seed quality traits. 相似文献
107.
108.
甘蓝型油菜小孢子培养胚发生能力的遗传分析 总被引:4,自引:0,他引:4
用 4× 4完全双列杂交研究了甘蓝型油菜小孢子培养胚状体发生能力的遗传规律。结果表明 :多数F1的胚产量与具高胚发生能力的亲本相近 ,部分F1的胚产量与双亲中亲值接近。胚状体发生能力主要由基因的加性效应控制。高胚发生能力由显性核基因控制。广义和狭义遗传力分别为 97 2 %和 81 1%。由Lisandra(高胚发生能 )×Kamikita(低胚发生能 )的F2 群体胚发生数的分离结果得出小孢子胚状体发生能力由具加性效应特点的两个基因位点控制 相似文献
109.
Fifteen lines of Brassica napus were resynthesized via ovule culture through 24 interspecific crosses between four Brassica oleracea and three Brassica campestris accessions. The degree of success in the interspecific crosses was significantly influenced by maternal genotypes. The interspecific hybrid production rate (HPR) varied with combinations from 0 to 76.9%, with a mean HPR of 24.7% for the crosses with B. campestris as the female parent and 6.9% for the crosses with B. oleracea as female parent. Twenty‐four crosses between seven natural and six resynthesized B. napus gave, on average, 10.3 seeds per pod, and ranged from 1.2 to 22.0 seeds per pod, depending on genotypes of both parents. Resynthesized lines of B. napus showed high erucic acid content and variable content of linolenic acid, ranging from 3.4% to 9.9%. The fatty acid composition in hybrid seeds between natural and resynthesized B. napus was dominated by the embryo genotypes; an additive mode was shown for erucic acid and positive over‐dominance for linolenic acid content. 相似文献
110.