全文获取类型
收费全文 | 4236篇 |
免费 | 204篇 |
国内免费 | 14篇 |
专业分类
林业 | 271篇 |
农学 | 151篇 |
基础科学 | 40篇 |
816篇 | |
综合类 | 682篇 |
农作物 | 239篇 |
水产渔业 | 396篇 |
畜牧兽医 | 1395篇 |
园艺 | 139篇 |
植物保护 | 325篇 |
出版年
2023年 | 36篇 |
2022年 | 26篇 |
2021年 | 88篇 |
2020年 | 95篇 |
2019年 | 106篇 |
2018年 | 91篇 |
2017年 | 86篇 |
2016年 | 94篇 |
2015年 | 67篇 |
2014年 | 103篇 |
2013年 | 189篇 |
2012年 | 245篇 |
2011年 | 288篇 |
2010年 | 184篇 |
2009年 | 145篇 |
2008年 | 240篇 |
2007年 | 260篇 |
2006年 | 237篇 |
2005年 | 235篇 |
2004年 | 227篇 |
2003年 | 222篇 |
2002年 | 200篇 |
2001年 | 57篇 |
2000年 | 52篇 |
1999年 | 54篇 |
1998年 | 36篇 |
1997年 | 30篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 34篇 |
1993年 | 48篇 |
1992年 | 32篇 |
1991年 | 43篇 |
1990年 | 30篇 |
1989年 | 39篇 |
1988年 | 33篇 |
1987年 | 23篇 |
1986年 | 33篇 |
1985年 | 30篇 |
1984年 | 34篇 |
1983年 | 24篇 |
1982年 | 14篇 |
1981年 | 19篇 |
1979年 | 14篇 |
1978年 | 14篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 17篇 |
1974年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有4454条查询结果,搜索用时 0 毫秒
101.
102.
103.
104.
105.
106.
Amprolium, a coccidiostat added to poultry feed, occurs in excreta at concentrations of 204 μ g?1 and investigations were made of the effect of this quantity of amprolium on the biochemistry of soil to which manure had been applied.Greenhouse experiments showed that 0.8 μg g?1 amprolium was found in soil pots 80 days after treatment with manure at the equivalent of 56.1 t ha?1 and was detectable 20 days following treatment at the equivalent of 11.2 t ha?1.Laboratory experiments indicated that amprolium was differentially adsorbed to two complexing media, soil and manure. Since amprolium was a constituent of treated manure, it was expected that the amprolium manure-soil system would offer various sites for adsorption of amprolium. Mixing amprolium with soil and with soil plus untreated manure yielded approximately the same effect on amprolium adsorption based on recoveries in water solution, and as methanol extractable. However, total recovery of amprolium from treated manure added to soil was only a fraction of the above, indicating the high complexing capacity of the manure.No effect on soil respiration was observed by either pure amprolium or amprolium as a constituent of treated manure. The higher rate of manure application caused greater respiration due to the presence of more readily oxidizable organic matter, but the respiration pattern attributed to the manure component was not unlike the respiration pattern of the Guelph loam soil. 相似文献
107.
During a period of immobilization of nitrate-15N and mineralization of organic N in a sandy-loam, changes were recorded in: (a) the concentration of an added carbon source, glucose-14C: (b) evolution of 14CO2: (c) bacterial populations; (d) distribution and concentration of newly-synthesized, acid-soluble, amino acid-15N; and (e) distribution and activities of several oxidative and hydrolytic enzyme systems.Added glucose-14C was rapidly metabolized by the soil microflora. After 1.5 day's incubation, when only 3.6 per cent of the added glucose was present, 68 per cent of the 14C remained in the soil-microbial system. During this period there was a marked increase in viable bacterial numbers and an almost complete immobilization of nitrate-15N. On continued incubation, microbial metabolites were oxidized at decreasing rates, the more rapid phase corresponding to a period of net decline in the viable bacterial population.Soil was fractionated by a relatively mild procedure into components containing: (a) extractable proteins; (b) extractable amino acids and peptides; (c) particulate material containing microbial cells, cell debris and material bound to larger soil particles; and (d) microbial metabolites mainly bound to soil colloids. Although the total, acid-soluble, amino acid-15N remained relatively constant for about 50 days, there were marked changes in their concentration in different fractions, especially in the extracts and in the fraction containing fine colloidal material. However, the relatively large decline in labelled, acid-soluble, amino acid-15N occurred during the active phase of oxidation of microbial metabolites when little net mineralization of labelled compounds occurred.Increases in enzymic activities generally coincided with increased viable bacterial populations although there were some exceptions, notably casein and benzoyl arginine amide-hydrolysing enzymes. The stabilities of the newly-formed enzymes varied markedly. The greatest relative changes in activity occurred with the casein-hydrolysing enzymes. Their activity reached a maximal value after the main flush of bacterial growth, was short-lived and was to a large extent extractable. The formation and disappearance of this extracellular proteolytic activity coincided approximately with that of a secondary peak of extractable, newly-synthesized, protein-15N. In general however, changes in enzymic activity could not be identified with changes of protein-15N concentrations of the different fractions. 相似文献
108.
Dr. Paul Münchberg 《Journal of pest science》1949,22(8):116-119
Ohne Zusammenfassung 相似文献
109.
110.