全文获取类型
收费全文 | 444篇 |
免费 | 41篇 |
专业分类
林业 | 15篇 |
农学 | 9篇 |
32篇 | |
综合类 | 76篇 |
农作物 | 15篇 |
水产渔业 | 109篇 |
畜牧兽医 | 198篇 |
园艺 | 5篇 |
植物保护 | 26篇 |
出版年
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 14篇 |
2017年 | 11篇 |
2016年 | 8篇 |
2015年 | 5篇 |
2014年 | 3篇 |
2013年 | 17篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 7篇 |
2009年 | 8篇 |
2008年 | 13篇 |
2007年 | 15篇 |
2006年 | 20篇 |
2005年 | 13篇 |
2004年 | 15篇 |
2003年 | 17篇 |
2002年 | 11篇 |
2001年 | 9篇 |
2000年 | 8篇 |
1999年 | 6篇 |
1998年 | 14篇 |
1996年 | 6篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 17篇 |
1988年 | 15篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 7篇 |
1984年 | 8篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 5篇 |
1973年 | 5篇 |
1972年 | 10篇 |
1971年 | 6篇 |
1970年 | 8篇 |
1969年 | 3篇 |
1968年 | 4篇 |
1963年 | 3篇 |
排序方式: 共有485条查询结果,搜索用时 312 毫秒
121.
The paper describes the use of fertilizers on grassland in England and Wales, as shown by surveys of fertilizer practice carried out during 1957–60.
About a third of the total consumption of N and K and almost half the total consumption of P is on grassland. Fertilizer use on leys has increased rapidly in recent years and the overall average rate of application is now of the order of 0·3 cwt N, P2 O5 and K2 O per acre per annum; permanent grass receives about half as much P and very much less N and K than the leys.
Generally speaking, consumption of N and K per acre of grassland was higher in arable districts than in livestock-farming areas, and on dairy farms than on rearing and feeding farms. However, rearing and feeding farms received more P per acre of grass (in particular, more basic slag) than arable farms. Little farmyard manure was used on grassland in the arable districts, whereas in the dairy counties of the western half of England and in Wales it formed a substantial part of the total plant nutrients supplied to grassland, particularly on fields mown for hay.
The paper also gives information on types of fertilizers used and the timing of fertilizer applications to grassland. All but about a fifth of the nitrogen used on grassland was applied between February and April. 相似文献
About a third of the total consumption of N and K and almost half the total consumption of P is on grassland. Fertilizer use on leys has increased rapidly in recent years and the overall average rate of application is now of the order of 0·3 cwt N, P
Generally speaking, consumption of N and K per acre of grassland was higher in arable districts than in livestock-farming areas, and on dairy farms than on rearing and feeding farms. However, rearing and feeding farms received more P per acre of grass (in particular, more basic slag) than arable farms. Little farmyard manure was used on grassland in the arable districts, whereas in the dairy counties of the western half of England and in Wales it formed a substantial part of the total plant nutrients supplied to grassland, particularly on fields mown for hay.
The paper also gives information on types of fertilizers used and the timing of fertilizer applications to grassland. All but about a fifth of the nitrogen used on grassland was applied between February and April. 相似文献
122.
Common water quality variables in nine, inland low‐salinity shrimp ponds in Alabama exhibited wide variation in concentrations among ponds and over time. Shrimp performance also varied considerably among ponds in 2008 as follows: survival, 16–128%; production, 928–5950 kg/ha; feed conversion ratio (FCR), 1.18–2.89. Measured water quality variables were not at concentrations high enough to be lethal to shrimp; but water temperature, dissolved oxygen, carbon dioxide, total ammonia nitrogen, calcium, and magnesium were occasionally outside optimum ranges for shrimp production and may have stressed shrimp. Survival and production both were positively correlated (P < 0.05) with increasing concentrations of methyl orange alkalinity, total alkalinity, and calcium hardness. Negative correlations (P < 0.05) between production and higher pH and water temperature may have resulted from lower water temperature and pH during final days of the crop in ponds harvested in October rather than from an actual effect of temperature and pH on growth. Nevertheless, those variables that were outside optimal ranges or correlated with shrimp survival or growth should be further investigated to ascertain whether or not excursions outside optimum ranges are harmful and to determine if observed correlations are causal. 相似文献
123.
Campbell GK Mun J Boyd M Medley P Leanhardt AE Marcassa LG Pritchard DE Ketterle W 《Science (New York, N.Y.)》2006,313(5787):649-652
Microwave spectroscopy was used to probe the superfluid-Mott insulator transition of a Bose-Einstein condensate in a three-dimensional optical lattice. By using density-dependent transition frequency shifts, we were able to spectroscopically distinguish sites with different occupation numbers and to directly image sites with occupation numbers from one to five, revealing the shell structure of the Mott insulator phase. We used this spectroscopy to determine the onsite interaction and lifetime for individual shells. 相似文献
124.
IL Boyd 《Science (New York, N.Y.)》2012,337(6092):306-307
125.
Water from 48 channel catfish Ictalurus punctatus ponds at Auburn and Greensboro, Alabama, USA, usually contained less than 1,000 total coliform and 200 fecal coliform bacteria per 100 mL. There were no sources of human fecal matter to ponds. Also, the fecal coliform: fecal streptococci ratio was less than 1.0 and typical of fecal contamination by warm-blooded animals other than humans. The abundance of coliforms was greater in spring and summer than in fall and winter in catfish ponds and sportfish ponds at Auburn, Alabama. In spite of high organic matter inputs in feed, catfish ponds had no greater abundance of coliforms than sportfish ponds. 相似文献
126.
Dr. A. E. W. Boyd 《Potato Research》1965,8(3):173-179
127.
B. Terence Grayson Sarah L. Boyd Alan J. Sampson Jeremy N. Drummond David Walter 《Pest management science》1995,45(2):153-160
Metconazole, (1RS, 5RS; 1RS, 5SR)-5-(4-chlorobenzyl)-2,2-dimethyl-1-(1H-1,2,4-triazol-1-ylmethyl)cyclopentanol, is a highly active fungicide, in particular controlling seed-borne and foliar diseases of cereals, such as wheat (Triticum aestivum L.) and barley (Hordeum vulgare L.). In order to maximize its foliar activity, an experimental survey of some types of surfactants and an emulsifiable oil was undertaken. Two types of metconazole formulation were investigated using a biological assay involving the therapeutic control of two diseases (Erysiphe graminis DC f. sp. tritici Marchal and Leptosphaeria nodorum Muell.) of wheat. Enhancements of activity by ?Genapol’? C12/C14 alcohol ethoxylates of an emulsifiable concentrate (ECM) formulation of metconazole were approximately three- to four-fold. For its, initially, less active suspension concentrate (SCM) formulation, enhancements were around 35-fold, so that with these adjuvants the two formulations were of similar activity. The enhancement ability of these ?Genapol’? surfactants was optimal at lower (5–10 moles) ethylene oxide content. These analogues induced marginally better enhancements of activity than members of a range of nonylphenol ethoxylates (?Arkopal’?), and emulsifiable paraffinic/naphthenic oil (HVI 60E) and a castor oil ethoxylate (?Atlas’? G1281) but were equivalent to a similar series of alcohol ethoxylates (?Dobanol’?) from another source. Varying the alkyl chain length between C9-C11 and C14-C15 in the ?Dobanol’? series had little effect on their high enhancements of metconazole activity. It was determined from trials varying the application rate of the best alcohol ethoxylates that application rates of 1–1.5 kg ha?1 were required for maximum activity. This implied the use of high adjuvant/metconazole ratios in one-pack adjuvant-containing formulations. A range of soluble liquid (SL) formulations were prepared with either ?Dobanol’? 23–6.5 or ?Dobanol’? 91-6/metconazole ratios varying from 5:1 to 15:1. There were found to be highly active and were recommended for field testing. 相似文献
128.
Liu J Boyd CK Kobayashi Y Chase CC Hammond AC Olson TA Elsasser TH Lucy MC 《Domestic animal endocrinology》1999,17(4):421-437
Mutations within the growth hormone receptor (GHR) gene that lead to an inactivated or truncated GHR protein cause abnormal growth and small adult size in a variety of species (Laron dwarfism). We studied a line of miniature Bos indicus cattle that have phenotypic (small mature size) and endocrine (increased blood growth hormone and decreased blood insulin-like growth factor-I concentrations) similarities to Laron dwarfs. Liver mRNA from miniature and control cattle was used to amplify a cDNA within the coding region of the GHR. The miniature cattle had GHR mRNA size (determined by Northern blot) and cDNA sequence that were similar to control cattle and, therefore, were unlike most Laron dwarf genotypes in which the GHR gene is mutated. Amounts of mRNA from liver as well as muscle (superficial neck and longissimus) were analyzed by ribonuclease protection assay for IGF-I, total GHR, GHR 1A (inducible, liver-specific GHR mRNA), and GHR 1B (constitutive GHR mRNA). Four control and five miniature bulls were tested. As expected, liver IGF-I mRNA was decreased in the miniature cattle (approximately 12% of control; P < 0.01). The amount of the total GHR as well as GHR 1A mRNA were also decreased in liver (17% and 19% of control, respectively; P < 0.01). Other GHR mRNA, including GHR 1B mRNA, were similar for miniature and control cattle. In muscle, there was a tendency (P < 0.10) for decreased IGF-I mRNA and increased GHR mRNA in miniature compared with control cattle. In summary, a novel phenotype for Laron dwarfism in Bos indicus cattle was associated with underexpression of GHR 1A mRNA, but not other GHR mRNA variants in liver. In addition to decreased GHR 1A mRNA, the miniature cattle had decreased liver IGF-I mRNA. Full expression of GHR 1A in liver, therefore, may be required for full liver IGF-I expression and normal growth. 相似文献
129.
Dickie AM Doust R Cromarty L Johnson VS Sullivan M Boyd JS 《Research in veterinary science》2003,75(2):121-126
A procedure for imaging the canine tympanic bulla, external ear canal and adjacent structures using currently available ultrasound equipment was established. Lateral and ventral transducer positions were identified for this purpose and a 6.5 MHz curvilinear transducer was considered to be optimal. The sonographic appearance of these structures in cadavers and live dogs unaffected by ear disease is documented. Fluid was introduced into the tympanic bullae of the cadavers and its presence could be identified through the bony wall of the bulla. The ability of ultrasound to differentiate between gas and fluid within the bulla has important clinical implications as this is a common occurrence in dogs with middle ear disease. Ultrasound has several advantages over other imaging modalities and the examination procedure was well tolerated by unsedated dogs. 相似文献
130.
The objective of this study was to determine whether laboratory testing currently available is able to provide prognostic information in canine pancreatitis. A prospective study of dogs with naturally occurring pancreatitis was undertaken. Twenty-two cases with histologically confirmed pancreatic inflammation were included in the study. Each dog had routine haematology parameters, serum biochemistry (including lipase and amylase), serum trypsin-like immunoreactivity and trypsinogen activation peptides (TAP) in urine and plasma measured. Twelve of the dogs were classified as having severe disease. These dogs had statistically significant increases in urinary TAP-creatinine ratio (UTCR) measurement, serum lipase, serum phosphate and serum creatinine concentrations. Additionally dogs with severe pancreatitis had significantly decreased urine specific gravity levels. The most sensitive and specific test to assess the severity of pancreatitis was the measurement of UTCR. 相似文献