全文获取类型
收费全文 | 32763篇 |
免费 | 1502篇 |
国内免费 | 2515篇 |
专业分类
林业 | 3874篇 |
农学 | 2518篇 |
基础科学 | 4026篇 |
4361篇 | |
综合类 | 15470篇 |
农作物 | 1191篇 |
水产渔业 | 967篇 |
畜牧兽医 | 2265篇 |
园艺 | 954篇 |
植物保护 | 1154篇 |
出版年
2024年 | 202篇 |
2023年 | 583篇 |
2022年 | 881篇 |
2021年 | 946篇 |
2020年 | 925篇 |
2019年 | 1052篇 |
2018年 | 636篇 |
2017年 | 1015篇 |
2016年 | 1341篇 |
2015年 | 1199篇 |
2014年 | 1761篇 |
2013年 | 1661篇 |
2012年 | 2589篇 |
2011年 | 2741篇 |
2010年 | 2097篇 |
2009年 | 2145篇 |
2008年 | 2018篇 |
2007年 | 2359篇 |
2006年 | 1916篇 |
2005年 | 1641篇 |
2004年 | 1190篇 |
2003年 | 1004篇 |
2002年 | 770篇 |
2001年 | 667篇 |
2000年 | 534篇 |
1999年 | 442篇 |
1998年 | 380篇 |
1997年 | 335篇 |
1996年 | 298篇 |
1995年 | 265篇 |
1994年 | 225篇 |
1993年 | 214篇 |
1992年 | 177篇 |
1991年 | 117篇 |
1990年 | 153篇 |
1989年 | 103篇 |
1988年 | 109篇 |
1987年 | 45篇 |
1986年 | 19篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1956年 | 2篇 |
1955年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
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
2.
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
3.
D. Bilalis P. Efthimiadis & G. Karagiannis 《Journal of Agronomy and Crop Science》2001,187(2):121-126
The effect of three herbicides, diclofop-methyl (DM), imazamethabenz-methyl (IM) and fenoxaprop-ethyl (FE), was investigated at the recommended rate (×) and double the recommended rate (2×) in a durum wheat crop. FE had the smallest effect on root system characteristics, while IM had the greatest effect. For all herbicides, the double rate treatment gave a greater statistical reduction than the single rate for root system characteristics. FE had the smallest effect on the activity of aerobic microorganisms, while DM gave the greatest reduction, 10 days after application, and all three herbicides reduced earthworm abundance. DM gave the smallest reduction in the number of tillers and in plant height, while the double rate of IM gave the greatest reduction. For all three herbicides, double the recommended rate resulted in a significant reduction in the weight of 1000 seeds, while no statistically significant deviations were noted at the recommended rate. Finally, the use of all three herbicides resulted in significantly lower statistical yields compared to the sample (control plot), although there were no significant statistical differences among them, for either recommended or double recommended rates. 相似文献
4.
5.
Field experiments were conducted at Tamil Nadu Rice Research Institute, Aduthurai, India, during the wet seasons of 1992 and 1993 to study the effect of full and partial substitution of fertiliser N with green manure N (Sesbania rostrata) on nitrogen uptake, yield attributes and yield of rice. The experiment consisted of eight treatments with two levels of N (100 and 200 kg ha−1 ) and three sources of N application viz., fertilizer, integrated (1:1 fertilizer and green manure N) and green manure N compared to the recommended practice (150 kg fertilizer plus 6.25 t ha−1 (72 kg N) green manure) and a no N control. Nitrogen application markedly increased the N uptake. Combined use of the two N sources at 200 and 222 kg N ha−1 and of single fertilizer N at 200 kg N ha−1 recorded the maximum N uptake, increased the yield attributes such as number of panicles per unit area, weight per panicle, number of total and filled grains per panicle and test weight. At 200 kg N ha−1 full substitution of N by green manure reduced the grain yield but only partial substitution of N by green manure resulted in almost similar yield as single fertilizer N. Thus 200 kg N ha−1 applied in equal proportions of fertilizer and green manure N can be recommended for medium duration rice cultivars. 相似文献
6.
液压技术的应用已成为现代化农业机械的典型标志。为此,介绍了农机液压技术的应用现状;并根据科学技术的发展,简要分析了农机液压技术的发展趋势。 相似文献
7.
8.
本文对会计电算化发展中存在的一些问题提出了对策与建议,并针对财会工作的自身特点,从程序控制和制度控制两个方面阐述了电算化会计信息下的内部控制方法。 相似文献
9.
本文介绍了开发城市地下空间的必然趋势及前景,阐明开发利用城市地下空间,对节省城市用地、节约能源、改善城市交通、减轻城市污染等都有着重要作用。 相似文献
10.