全文获取类型
收费全文 | 91578篇 |
免费 | 5499篇 |
国内免费 | 7292篇 |
专业分类
林业 | 8831篇 |
农学 | 6120篇 |
基础科学 | 8374篇 |
16025篇 | |
综合类 | 44195篇 |
农作物 | 3804篇 |
水产渔业 | 2676篇 |
畜牧兽医 | 8481篇 |
园艺 | 2482篇 |
植物保护 | 3381篇 |
出版年
2024年 | 830篇 |
2023年 | 1940篇 |
2022年 | 2874篇 |
2021年 | 3247篇 |
2020年 | 3226篇 |
2019年 | 3723篇 |
2018年 | 2110篇 |
2017年 | 3445篇 |
2016年 | 4392篇 |
2015年 | 3678篇 |
2014年 | 5330篇 |
2013年 | 5231篇 |
2012年 | 7589篇 |
2011年 | 7317篇 |
2010年 | 5717篇 |
2009年 | 5708篇 |
2008年 | 4963篇 |
2007年 | 6004篇 |
2006年 | 4956篇 |
2005年 | 3885篇 |
2004年 | 3151篇 |
2003年 | 2585篇 |
2002年 | 1877篇 |
2001年 | 1705篇 |
2000年 | 1503篇 |
1999年 | 1189篇 |
1998年 | 921篇 |
1997年 | 812篇 |
1996年 | 710篇 |
1995年 | 758篇 |
1994年 | 654篇 |
1993年 | 499篇 |
1992年 | 413篇 |
1991年 | 353篇 |
1990年 | 290篇 |
1989年 | 231篇 |
1988年 | 178篇 |
1987年 | 124篇 |
1986年 | 70篇 |
1985年 | 36篇 |
1984年 | 29篇 |
1983年 | 9篇 |
1982年 | 24篇 |
1981年 | 17篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 14篇 |
1977年 | 5篇 |
1962年 | 8篇 |
1956年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
农业机械化是农业现代化的基础,是现代化的先决条件,发展农业机械化迫切需要加大投入。为此,分析了金华市现阶段农机化投入的现状及存在的问题;提出了通过建立政府、集体、信贷、农户、外资等“多位一体”的投入机制,加大农机化投入,促进农机化事业健康发展的思路。 相似文献
62.
农机服务合作社运作模式初探 总被引:9,自引:2,他引:7
通过后塍农机服务合作社的运作实践和成功经验,总结了农机服务合作社运作的自身特点,提出其发展模式的几点探索意见。 相似文献
63.
Indices of the tomato seedling quality maintenance level after production before field planting were studied through simulated experiments, small--scale operation, indoor analyses and measurements, and field observation. The results showed that under simulated shipping and storage conditions, seedling quality change following different durations (days) of shipping and storage was correlated significantly or even very significantly with certain physiological and morphological indices. With various measured indices following different periods of shipping and storage treatment subjected to multinomial successive regressive correlation analysis, the principal factors influencing seedling quality maintenance level are identified to be chlorophyll content→dry short weight→ leaf freshness index in order of their importance. Significance analysis with multinomial fitted equation indicated that correlations between any one of above three factors and the growth index after field planting reached very significant difference level. 相似文献
64.
65.
66.
Abstract. Anecdotal and circumstantial evidence have suggested that the Olsen test underestimates plant-available phosphorus (P) in basaltic soils in Northern Ireland. Therefore, the ability of this test to predict plant-available P in basaltic (and non-basaltic) soils was investigated by regressing Olsen-P data against herbage P indices calculated from plant tissue test data using the diagnosis and recommendation integrated system. The average Olsen-P concentration for a range of fields situated on basaltic soils was considerably lower than the average Olsen-P concentration for a range of fields situated on non-basaltic soils, and yet mean sward P status, as given by the herbage P indices, was similar for both groups of fields. Herbage P indices were also much better correlated with Olsen-P measurements in non-basaltic soils than in basaltic soils. Furthermore, at low Olsen-P values (≶9mgPL−1 ) some swards on basaltic soils were genuinely deficient in P, while others were sufficient or even in surplus for this nutrient. The results confirm that Olsen-P is inadequate as a predictor of plant-available P in basaltic soils. It is concluded that an alternative soil test is needed to provide a reliable assessment of plant-available P in basaltic soils, to prevent overuse of fertilizer and manure P and to minimize the amounts of P entering local watercourses. 相似文献
67.
SUMMARY: Aoshio is hypoxic milky blue-green seawater observed in some eutrophic bays. Previous studies have shown that colloidal sulfur causes the coloration and that the source of aoshio water is attributed to coastal anoxic bottom water. Occurrences of aoshio have been reported in limited areas of coastal seawater, although hypoxic transparent water seems rather universal. Promotion in auto-oxidation of sulfide by metal ions in seawater was investigated to explain the occurrences of aoshio. Artificial seawater containing 10 μM metal ion was assayed for the sulfide oxidation rate. The velocity constant which represents the oxidation rate within the initial 30 min and the amount of reacted sulfide in 2 h were determined by oxygen monitoring and sulfide quantification, respectively. Fe2+ and Cu2+ enhanced the initial 30 min reaction. Fe2+ , Fe3+ and Ni2+ increased the amount of reacted sulfide in 2 h, forming whitish turbid water. Seawater from a suspected source of aoshio water was also assayed for the auto-oxidation rate of sulfide. The oxidation rate in water from 12 m depth was 13–19 times higher than the artificial seawater without an addition of heavy metal ions. More than 15% of the oxidation rate in 12 m deep seawater was explained by dissolved iron in the seawater. 相似文献
68.
不同方法构建磺胺二甲氧嘧啶免疫抗原的比较研究 总被引:3,自引:0,他引:3
为探讨合成磺胺二甲氧嘧啶(SDM)免疫抗原的有效途径,采用重氮偶合法和戊二醛法分别合成SDM免疫抗原,并对其结构特征、光谱特征和SDM结合比进行比较.结果表明,在合成SDM-BSA中采用重氮偶合法比戊二醛法好. 相似文献
69.
高校公寓文化建设的几点思考 总被引:2,自引:0,他引:2
从校园文化、学风建设、素质教育、思想教育等方面,阐述公寓文化的作用和意义,提出理顺管理机制、发挥学生主体作用、加强制度建设,开展公寓文化活动等几点建议。 相似文献
70.
浅论网络信息污染及其防治对策 总被引:3,自引:0,他引:3
谭文华 《农业图书情报学刊》2004,15(3):69-71,79
简要阐述了网络信息污染的具体表现形式及其带来的危害作用,提出了防治信息污染的对策。 相似文献