全文获取类型
收费全文 | 8940篇 |
免费 | 483篇 |
国内免费 | 877篇 |
专业分类
林业 | 770篇 |
农学 | 1194篇 |
基础科学 | 364篇 |
957篇 | |
综合类 | 4107篇 |
农作物 | 943篇 |
水产渔业 | 27篇 |
畜牧兽医 | 484篇 |
园艺 | 415篇 |
植物保护 | 1039篇 |
出版年
2024年 | 44篇 |
2023年 | 163篇 |
2022年 | 311篇 |
2021年 | 326篇 |
2020年 | 326篇 |
2019年 | 344篇 |
2018年 | 287篇 |
2017年 | 456篇 |
2016年 | 502篇 |
2015年 | 373篇 |
2014年 | 495篇 |
2013年 | 598篇 |
2012年 | 725篇 |
2011年 | 579篇 |
2010年 | 516篇 |
2009年 | 530篇 |
2008年 | 425篇 |
2007年 | 451篇 |
2006年 | 371篇 |
2005年 | 282篇 |
2004年 | 228篇 |
2003年 | 173篇 |
2002年 | 157篇 |
2001年 | 175篇 |
2000年 | 171篇 |
1999年 | 157篇 |
1998年 | 121篇 |
1997年 | 125篇 |
1996年 | 97篇 |
1995年 | 112篇 |
1994年 | 78篇 |
1993年 | 86篇 |
1992年 | 86篇 |
1991年 | 86篇 |
1990年 | 76篇 |
1989年 | 60篇 |
1988年 | 41篇 |
1987年 | 45篇 |
1986年 | 27篇 |
1985年 | 16篇 |
1984年 | 16篇 |
1982年 | 10篇 |
1981年 | 6篇 |
1980年 | 11篇 |
1979年 | 3篇 |
1978年 | 11篇 |
1977年 | 5篇 |
1976年 | 7篇 |
1962年 | 2篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
高产棉花太阳辐射能利用率及干物质分配规律研究 总被引:6,自引:0,他引:6
通过对1988~1989年高产棉花栽培试验结果进行分析发现,棉花的太阳辐射利用率在叶面积系数小于2.0时随叶面积系数的增加而线性增加,大于2.0时增加变缓。从生育时间看,7月中旬前太阳辐射利用率指数上升,7月中旬至8月底相对稳定在1.2~1.4克/兆焦左右,9月以后又不同程度线性下降。生长季内子棉太阳辐射经济效率1988和1989年分别为0.14和0.15克/兆焦。收获指数与最大叶面积系数呈显著负相关;盛花期之前棉株各器官之间的同伸关系或明显,盛花期后器官的生长相互间无明显的确定性关系。如能调节密度与叶面积系数的关系,使得既提高5~6月的辐射能利用率,同时使7~8月叶面积系数维持在3.0~3.5的适宜范围内,9~10月群体又不早衰,则有利于获得高产。 相似文献
62.
63.
为持续控制小麦叶锈病及促进小麦的抗叶锈病育种工作,2019—2020年自江苏、浙江和安徽3个省采集自然感叶锈病的小麦病叶,经分离获得小麦叶锈菌单孢分离物,利用43个小麦叶锈病鉴别寄主材料对其致病类型进行鉴定,并对其毒性结构进行分析。结果显示,从170份小麦叶锈菌单孢分离物中共鉴定出67个致病类型,主要致病类型为THS、SHJ、PHS和SHS,出现频率分别为8.8%、7.6%、5.9%和5.9%。江苏、浙江和安徽3个省的单孢分离物对携带抗叶锈基因Lr10、Lr12、Lr22a、Lr22b、Lr29、Lr33、Lr35和Lr36的鉴别寄主材料的苗期毒性频率均超过90.0%,而对携带抗叶锈基因Lr9、Lr24、Lr25、Lr28、Lr38、Lr40、Lr41、Lr42、Lr43和Lr13+3ka的鉴别寄主材料的苗期毒性频率均小于10.0%。卡方检验及Fisher精确检验显示,3个省小麦叶锈菌群体对抗叶锈基因Lr1、Lr2a、Lr3、Lr14b、Lr18、Lr21、Lr26、Lr27+31、Lr32和Lr37的毒力存在显著分化。浙江省小麦叶锈菌群体具有较少的毒性因子(4.73)和毒性值(600... 相似文献
64.
为更好地利用老芒麦(Elymus sibiricus L.)野生资源,本研究从我国青藏高原、西北、华北、东北地区以及国外部分地区共采集了1 723份野生披碱草属种质资源,通过表型特征观测和流式细胞仪检测,共鉴定出了990份野生老芒麦种质,246份垂穗披碱草种质,并测得老芒麦的DNA含量在5.86~7.30 Gb之间,平均DNA含量为6.66 Gb;垂穗披碱草材料的DNA含量在9.50~10.36 Gb之间,平均DNA含量为9.97 Gb。研究结果显示,在西北、华北以及东北地区的部分野生老芒麦材料在苗期基部叶鞘出现了绒毛,分析发现该表型出现的概率与经度和纬度呈极显著正相关关系(P<0.01),与海拔、年年均气温以及年平均降雨量呈极显著负相关关系(P<0.01)。表明老芒麦苗期基部叶鞘绒毛的有无与环境因子之间存在着必然的联系,可能是老芒麦种质应对不同环境类型的适应性机制之一。本研究为老芒麦的形态鉴定提供了新的依据,为老芒麦种质资源挖掘和育种应用提供了材料基础。 相似文献
65.
Three trickle irrigation schedules, two of which were scheduled according to soil water potential ( soil) (tensiometer method) and daily stem contraction (DSC) (dendrometer method) respectively and the other one was a schedule of restricted water supply, were applied to a mature peach orchard.The annual water application based on soil was greater than that based on DSC. However, tree growth, fruit size and leaf water potential (leaf) on the trees in the dendrometer scheduling plot did not differ from those in the tensiometer scheduling plot while the premature fruit drop and fruit bud initiation were greatly different. The restricted water supply treatment limited significantly both tree and fruit growth. In addition, the lower leaf was observed on the trees in this plot.Further study shows that use of the dendrometer method for scheduling irrigation satisfies the water needs of the plant and that the tensiometer method is less accurate.Abbreviations leaf
leaf water potential
- soil
soil water potential
- DSC
daily stem contraction
- LVDT
linear variable displacement transducer
- PET
potential evapotranspiration 相似文献
66.
67.
68.
Robert Jankowiak Piotr Bilański Julita Zając Adrianna Jobczyk Stephen J. Taerum 《Forest Pathology》2023,53(4):e12821
In Poland's pine forests, mistletoe (Viscum album subsp. austriacum) abundance has increased over the past 20 years. This mistletoe infestation has decreased the growth and vigour of Scots pine trees. In this study, we surveyed the culturable fungi from healthy and diseased V. album subsp. austriacum leaves from two stands in Poland. In total, 63 distinct species were identified, 99.8% of which belonged to the phylum Ascomycota. The community compositions of fungi in mistletoe leaves were similar in healthy and diseased leaves as Alternaria alternata, Aureobasidium pullulans, Botryosphaeria visci, Fusarium paeoniae and Microsphaeropsis olivacea were consistently found in leaves of all symptom types. The most frequently isolated fungus from asymptomatic leaves was M. olivacea, followed by A. alternata, A. pullulans and Hypoxylon rubiginosum. In comparison, the most frequently isolated fungi from leaves with rusty-brown necrotic spots were (in decreasing order) M. olivacea, B. visci, F. paeoniae and A. alternata, while the most frequently isolated fungi from leaves with black or dark brown spots were M. olivacea, A. alternata, A. pullulans, Epicoccum layuense and F. paeoniae. This study was the first comprehensive report showing that certain fungal species may be pathogens of V. album subsp. austriacum in Poland. This study was also the first report of F. paeoniae, F. juglandicola, Diaporthe vacuae and Heterotruncatella spartii from V. album, and the first report of D. vacuae and H. spartii in Poland. 相似文献
69.
Edival Ângelo Valverde Zauza Lúcio Mauro da Silva Guimarães Nilza de Lima Pereira Sales Samuel Alves dos Santos Rafael Ferreira Alfenas Acelino Couto Alfenas 《Forest Pathology》2023,53(2):e12806
An outbreak of a new and severe disease was observed in Eucalyptus plantations of Bahia state, Brazil. An Ascomycota fungus has been frequently associated with the main symptoms of the disease namely leaf spot, branch cankers, shoot blight, defoliation, and dieback. Based on morphological characteristics, phylogenetic analysis (ITS and TEF-1α genes), and pathogenicity test on Eucalyptus plants, Pseudoplagiostoma eucalypti was identified as the causal agent of the disease. Although P. eucalytpi has been known from in Brazil since 1998, this is the first report of it causing severe disease and die-back on Eucalyptus spp. and we also record new symptoms associated with the pathogen. 相似文献
70.
柑橘溃疡病(Xanthomonas citri subsp. citri,Xcc)是严重阻碍柑橘产业发展的世界性检疫病害,防控困难,选育抗病品种为防治溃疡病的唯一有效办法。枸橼C-05是柑橘属独特的抗溃疡病种质,为抗性机理和抗病育种提供了种质基础。为了进一步评价枸橼C-05的抗性,另外收集了13份枸橼种质,对其进行溃疡病的离体和活体抗性评价。叶片形态学观察表明,14份枸橼种质存在较大的形态学差异。采用离体与活体注射接种不同浓度的柑橘溃疡病菌,根据叶片的感病症状、病斑周围黄色晕圈大小等典型溃疡病症状,综合评价枸橼类种质的抗病性。结果表明:枸橼种质之间对溃疡病的抗性存在极大差异,溃疡病的抗性评价综合病情指数显示枸橼C-05、园香橼、矮果香橼、美国枸橼、普通枸橼和印度大果综合病情指数较小,表现为极抗病或抗病,其他枸橼种质表现不同程度的感病性;枸橼种质的抗病或感病性与其叶片形态特征无关。枸橼C-05和5个抗病枸橼种质对柑橘溃疡病具有针对性的抗性,这对进一步研究抗病机理和抗病育种具有重要意义。 相似文献