全文获取类型
收费全文 | 7365篇 |
免费 | 414篇 |
国内免费 | 1036篇 |
专业分类
林业 | 675篇 |
农学 | 614篇 |
基础科学 | 769篇 |
1982篇 | |
综合类 | 3072篇 |
农作物 | 363篇 |
水产渔业 | 79篇 |
畜牧兽医 | 388篇 |
园艺 | 141篇 |
植物保护 | 732篇 |
出版年
2024年 | 64篇 |
2023年 | 194篇 |
2022年 | 269篇 |
2021年 | 292篇 |
2020年 | 312篇 |
2019年 | 342篇 |
2018年 | 268篇 |
2017年 | 305篇 |
2016年 | 352篇 |
2015年 | 292篇 |
2014年 | 381篇 |
2013年 | 534篇 |
2012年 | 533篇 |
2011年 | 538篇 |
2010年 | 412篇 |
2009年 | 401篇 |
2008年 | 325篇 |
2007年 | 406篇 |
2006年 | 340篇 |
2005年 | 340篇 |
2004年 | 214篇 |
2003年 | 210篇 |
2002年 | 160篇 |
2001年 | 147篇 |
2000年 | 142篇 |
1999年 | 122篇 |
1998年 | 129篇 |
1997年 | 115篇 |
1996年 | 95篇 |
1995年 | 87篇 |
1994年 | 72篇 |
1993年 | 86篇 |
1992年 | 70篇 |
1991年 | 54篇 |
1990年 | 65篇 |
1989年 | 44篇 |
1988年 | 25篇 |
1987年 | 31篇 |
1986年 | 17篇 |
1985年 | 4篇 |
1984年 | 5篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1963年 | 1篇 |
1962年 | 1篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有8815条查询结果,搜索用时 734 毫秒
91.
92.
93.
泡桐属(Paulownia)分类管见 总被引:7,自引:0,他引:7
陈志远 《华中农业大学学报》1986,(3)
自泡桐属(Paulownia)在1835年建立以来,至1938年,中外研究者先后发表的新种达18种、3变种,嗣后又相继发表了若干新种,经胡秀英和《中国植物志》分别归为六种和七种一变种。到目前为止,又相继发表了不少新种和变种,泡桐属共有26种7变种(包括异名)。本文根据历史文献和近年来调查研究所获得的标本、资料,对泡桐属分类中存在的异名处理和种与变种废、留欠妥以及泡桐属的归科问题,提出了自己的意见。 相似文献
94.
95.
96.
97.
Erin E Grabarczyk Russell F Mizell III Jeremy K Greene Gary A Herzog P Glynn Tillman Ted E Cottrell 《Journal of insect science (Online)》2022,22(1)
Stink bugs (Hemiptera: Pentatomidae) are ubiquitous, cryptic, phytophagous pests that are found in many crops. In agroecosystems, individuals disperse from adjacent noncrop hosts and tend to aggregate or cluster within fields. In this study, we characterized the distribution of Euschistus servus (Say) and Euschistus tristigmus (Say) (Hemiptera: Pentatomidae) over 2 yr at three southeastern United States farmscapes. Stink bugs were captured in pheromone-baited traps, and Spatial Analysis by Distance Indices (SADIE) used to identify the location of significant aggregations by habitat type and season. Euschistus servus adults were more likely to be captured in pecan orchards, cotton, other crops, or unmanaged habitats than in woodland habitats. Significant aggregations of E. servus were detected in a variety of habitats including pecan, corn, cotton, peanut, and tobacco, as well as fallow and hay fields, pastures, and hedgerows. Fewer adult E. tristigmus were captured than E. servus adults, and E. tristigmus adults were typically trapped and aggregated in woodland habitats. The resulting data provide an important understanding regarding the seasonal movement and relative abundance levels of stink bug populations, which are critical to the development of integrated pest management strategies. 相似文献
98.
Impact of cash crop cultivation on household income and migration decisions: Evidence from low-income regions in China
下载免费PDF全文
![点击此处可从《农业科学学报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
This study examines the impact of cash crop cultivation on household income and migration decisions, using survey data collected from low-income regions in China. Given farmers decide themselves whether to cultivate cash crops, an endogenous treatment regression model that accounts for potential selection bias issue is used to analyze the data. The empirical results show that cash crop cultivation exerts a positive and statistically significant impact on household income, but it does not affect household migration decisions significantly. The disaggregated analyses reveal that cash crop cultivation significantly increases farm income but decreases off-farm income. 相似文献
99.
Mondal Satyen Jamil Hasan M. Ahmed Tofayel Giashuddin Miah M. C. Sta Cruz Pompe M. Ismail Abdel 《水稻科学》2020,27(6):515-528
Rice (Oryza sativa) plants acquired excess photosynthates in the form of nonstructural carbohydrates (NSCs) in their stems and grain. Despite keen interest in rice NSC, the dynamics of NSC accumulation, translocation and re-accumulation have not yet been well investigated. AG1 and AG2 QTLs associated with flooding tolerance through catalyzing starch into soluble sugar in germinating seeds. Here we conducted three experiments, greenhouse and field to lay the groundwork for large-scale diversity studies on grain NSC and some agronomic traits under direct-seeded rice (DSR) system, using elite lines incorporating AG1, AG2 and AG1-AG2 QTLs into the popular varieties PSB Rc82 and Ciherang-Sub1 along with the donors Kho Hlan On (AG1) and Ma-Zhan Red (AG2). In germinating seedlings, soluble sugars increased, while starch concentration decreased gradually especially in the tolerant checks and AG1-AG2 introgression lines under flooded soil. Soluble sugar accumulation in stem started to increase from the vegetative stage and peaked at the panicle initiation stage then gradually decreased towards the maturity stage. But Sub1-AG lines had higher sugar and starch concentrations at different growth stages than other genotypes in wet season 2016 and dry season 2017. Plant survival rate was positively correlated with the stem NSC at the early vegetative stage (21 days after sowing), and stem NSC was positively associated with plant height at different growth stages. Among the tested seeding rate, the most suitable seeding rate, 4 g/m2 with shallow burial depth (0.5 cm), resulted in better seedling establishment, relatively higher seedling vigor index and higher leaf area index under flooding in DSR system. Introgression of AG1-AG2 QTLs had no any negative impact on nonstructural carbohydrate, germination rate, and growth and biomass production. 相似文献
100.
野茼蒿黄脉病毒的田间寄主范围及其基因多样性特征 总被引:1,自引:0,他引:1
为明确野茼蒿黄脉病毒(Crassocephalum yellow vein virus,CraYVV)的田间寄主范围及其群体基因结构特征,分别采用克隆和测序技术对采自云南省西双版纳傣族州、红河哈尼族彝族自治州的7种杂草和2种作物进行CraYVV的分离和鉴定,并通过生物信息学软件对分离到的CraYVV进行基因组结构、重组及基因遗传结构分析。结果显示,在赛葵、龙葵、臭牡丹、水茄、豨莶、野茼蒿和一点红7种杂草以及茄子和草莓2种作物中均分离到CraYVV,共获得20条CraYVV全长序列;CraYVV所有分离物分属2个株系,将其命名为YJ株系和JH株系;JH株系具有地理隔离特征,与YJ株系存在一定的遗传距离;重组分析显示,CraYVV是由烟草曲茎病毒(tobacco curly shoot virus,TbCSV)和云南烟草曲叶病毒(tobacco leaf curl Yunnan virus,TbLCYnV)重组产生;遗传结构分析显示,CraYVV中C1基因变异最显著,其次是C4基因和基因间隔区。表明CraYVV能侵染5科9种杂草和作物,具有较广的寄主范围,且菜豆金色花叶病毒属病毒能够侵染草莓、CraYVV能够侵染茄子,显示来源于杂草的菜豆金色花叶病毒属病毒在自然条件下能够侵染作物。 相似文献