全文获取类型
收费全文 | 722篇 |
免费 | 16篇 |
国内免费 | 21篇 |
专业分类
林业 | 18篇 |
农学 | 35篇 |
基础科学 | 4篇 |
75篇 | |
综合类 | 386篇 |
农作物 | 18篇 |
水产渔业 | 11篇 |
畜牧兽医 | 191篇 |
植物保护 | 21篇 |
出版年
2022年 | 6篇 |
2021年 | 3篇 |
2020年 | 7篇 |
2019年 | 9篇 |
2018年 | 21篇 |
2017年 | 21篇 |
2016年 | 18篇 |
2015年 | 19篇 |
2014年 | 12篇 |
2013年 | 6篇 |
2012年 | 49篇 |
2011年 | 69篇 |
2010年 | 34篇 |
2009年 | 30篇 |
2008年 | 48篇 |
2007年 | 58篇 |
2006年 | 40篇 |
2005年 | 33篇 |
2004年 | 32篇 |
2003年 | 39篇 |
2002年 | 20篇 |
2001年 | 11篇 |
2000年 | 19篇 |
1999年 | 12篇 |
1998年 | 13篇 |
1997年 | 4篇 |
1996年 | 4篇 |
1995年 | 4篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 8篇 |
1988年 | 3篇 |
1986年 | 3篇 |
1985年 | 3篇 |
1982年 | 3篇 |
1977年 | 4篇 |
1973年 | 3篇 |
1971年 | 2篇 |
1969年 | 2篇 |
1968年 | 3篇 |
1966年 | 3篇 |
1943年 | 3篇 |
1941年 | 2篇 |
1934年 | 2篇 |
1933年 | 4篇 |
1930年 | 2篇 |
1925年 | 2篇 |
排序方式: 共有759条查询结果,搜索用时 31 毫秒
751.
752.
基因组、转录组、蛋白组、代谢组学技术作为研究生物体受到内外环境扰动后基因、蛋白和小分子等物质的重要手段,被广泛应用于植物学、微生物学、食品安全等领域。综述了单组学技术在研究不同品种、生态环境、胁迫、功能基因、香型、器官条件下的烟草差异变化机理的应用。最后对各组学优缺点进行了分析,介绍了多组学联合分析技术在提升烟叶品质研究中的作用,并对下一步的研究和应用进行了展望,以期为烟草品质的分子机理研究提供借鉴与参考。 相似文献
753.
连续两年采用田间实地调查及室内化验分析的方法,分析了云南曲靖不同县(市)烟区土壤有效镁、速效钾含量状况及其交互作用对烤烟钾、钙、镁含量、化学成分和评吸指标的影响,结果表明:曲靖中海拔红壤烟区土壤有效镁平均含量314.10 mg·kg~(-1),变幅32.64~1 402.00 mg·kg~(-1),会泽烟区有效镁含量高达711.25mg·kg~(-1);速效钾平均含量197.95 mg·kg~(-1),变幅21.63~718.92 mg·kg~(-1),除陆良县外,其他各县(市)土壤速效钾含量均处于中等至高等含量范围。烤烟镁含量随土壤有效镁含量的升高而显著增加,烤烟钾含量随着土壤速效钾含量的升高先降低后显著增加,烤烟钙含量随两者变化不显著;交互作用对烤烟钾、镁、钙含量及K/(Mg+Ca)有显著影响。土壤有效镁、速效钾交互作用对烤烟品质影响较大,在土壤有效镁含量处于中、低水平(100 mg·kg~(-1)),土壤速效钾含量处于适宜及以上水平(150 mg·kg~(-1))时,烟叶品质表现最好。 相似文献
754.
曲靖烟区土壤磷锌互作对烟叶磷锌含量和品质的影响 总被引:3,自引:0,他引:3
利用田间调查采样及室内测定分析方法,分析了云南省曲靖市中海拔红壤烟区648个代表性烟田的土壤有效磷、有效锌含量及其互作对烟叶磷、锌含量和其品质的影响。结果表明:(1)土壤有效磷含量介于0.96~101.28 mg/kg,平均为31.34 mg/kg,35.80%的土样有效磷处于烤烟生长适宜范围(20~40 mg/kg);土壤有效锌含量丰富,介于0.20~23.68 mg/kg,平均为3.01 mg/kg,74.69%的土样有效锌含量处于烤烟生长适宜范围(1~4 mg/kg);(2)烟叶磷含量处于中等偏低水平,平均为1.9 g/kg,95.22%的烟样符合烟叶磷含量一般范围(1.5~6.0 g/kg);烟叶锌含量较高,平均为46.12 mg/kg,94.29%的烟样处于烟叶锌含量一般范围(20~80 mg/kg);(3)烟叶锌含量随土壤有效锌含量的升高而显著增加,随土壤有效磷含量的升高而降低;而烟叶磷含量与土壤有效磷和有效锌含量之间的关系不明显;(4)土壤有效磷和有效锌含量的交互作用对烟叶磷含量无显著影响,但对烟叶锌含量存在极显著影响,高含量的土壤有效磷会拮抗烟株对土壤有效锌的吸收;(5)土壤有效磷对烟叶品质影响较小,而土壤有效锌含量与烟叶化学成分及香气物质含量的相关性较密切。在土壤有效锌含量处于中低(2.0 mg/kg)水平,而土壤磷含量处于中等适宜(20~40 mg/kg)水平时,烟叶品质表现最好。 相似文献
755.
Turkson PK 《Tropical animal health and production》2004,36(5):413-425
A study was designed to identify factors perceived by veterinarians and veterinary technicians as likely to promote private veterinary practice in Ghana. The participatory appraisal approach was used. The response rates were 88% (n = 90), 100% (n = 9) and 86% (n = 200) for government field veterinarians, private veterinarians and government veterinary technicians, respectively. Significant proportions of government field veterinarians (67%, n = 79), and veterinary technicians (64%, n = 167) were willing to go into private practice if the necessary push was given. Factors perceived as likely to motivate them to go into private practice included availability of capital to cover start-up costs; provision of a vehicle; prospect of higher income; availability of loans with low interest rates; availability of credit facilities from suppliers; stable macroeconomic environment with low interest and inflation rates; high pet, poultry and livestock populations at locations earmarked for private practice; leasing of vacant government premises for use as clinic and for accommodation; and enforcement of legislation on private practice, especially that against moonlighting by government veterinarians and technicians. These should be considered and used in the promotion of private veterinary practice in Ghana. 相似文献
756.
Turkson PK 《Tropical animal health and production》2003,35(6):477-490
A cohort study was designed to observe and follow up mortality in lambs and kids in 88 flocks of sheep and goats under the traditional production system in five villages within the coastal savanna zone of Ghana over a 2-year period. The overall mortality rates for kids and lambs were 30.8% and 33.5%, respectively. Significantly higher proportions of kids (80.2%) and lambs (75.6%) up to 3 months of age died compared to kids and lambs from 4 to 12 months of age. The differences in mortality rates, either between male and female kids and lambs or between single-born and multiple-birth kids and lambs, were not significant. The odds ratio (OR) and relative risks (RR) for lambs and kids, on the basis of sex and birth types, were not significant; neither were the values obtained for attributable risk, attributable fraction, population attributable risk and population attributable fraction. The overall mortality rate on the basis of species of animal was not significant. At the village level, significant differences in the proportions of mortality on the basis of sex were seen in two villages. At Akotokyir, more male lambs (54.2%) died compared to females (27.6%), while at Apewosika more female lambs (42.2%) died compared to males (16.7%). The only significant difference in mortality proportions on the basis of birth type at the village level was seen at Apewosika, where more single-born kids died (52.8%) compared to kids born with sibling(s) (28.4%). The significant ORs for mortalities were 3.10 for male lambs at Akotokyir, 3.35 for female lambs at Apewosika and 2.82 for single-born kids at Apewosika. The corresponding RRs were equally significant. On the basis of species, significantly more lambs died at Akotokyir (44.2%) and Kwesimprah (44.7%) compared to kids. The implications of these findings are discussed. 相似文献
757.
由烟草疫霉引发的烟草黑胫病(tobacco black shank,TBS)是烟草生产上最具毁灭性的病害之一。绿原酸(CGA)是广泛存在于自然界中的一种酚类物质,具有抗氧化和抑菌等多种生物活性。试验采用离体培养和叶面喷施的方式研究CGA对烟草疫霉的抑制作用及其对TBS的防治效果。结果表明,与对照相比,100μg/mL CGA可抑制烟草疫霉的生长,菌落直径从7.51cm变为5.95cm,二者差异显著;叶片病斑大小从4.60cm显著降低到1.20cm;抗氧化酶(POD、SOD和CAT)及防御酶(PPO)的活性分别显著提高72.6%、54.6%、155.8%和8.2%。此外,喷施CGA的叶片中可溶性蛋白含量从3.0mg/g显著提高到5.3mg/g;可溶性糖含量从2.7mg/g显著下降到1.5mg/g,脯氨酸含量从192.7µg/g显著下降到150.4µg/g。因此,CGA能直接抑制烟草疫霉的生长,有助于提高烟草对TBS的抗性。 相似文献
758.
为扩展烟草秸秆的利用途径,探究烟草秸秆绿原酸对烟草疫霉的抑菌效果,采用单因素试验和响应面分析法优化烟草秸秆绿原酸微波辅助提取工艺,并通过离体培养探讨烟草秸秆绿原酸对烟草疫霉菌的抑制作用。单因素及响应面结果表明,烟草秸秆绿原酸最佳提取工艺为料液比1∶15(g·mL-1),提取温度50.03℃,乙醇体积分数50%,此时粗提物中绿原酸含量为3.48 mg·g-1;离体条件下,烟草秸秆绿原酸的添加均抑制了疫霉菌的生长,其中175 mg·L-1烟草秸秆绿原酸对菌落直径的抑制效果最为显著,抑菌率高达32%。此外,碘化丙啶(PI)染色结果表明,175 mg·L-1的烟草秸秆绿原酸可通过破坏烟草疫霉菌细胞膜的完整性抑制菌丝生长。研究结果为烟草秸秆有效利用和新型天然植物源杀菌剂开发奠定了基础。 相似文献
759.