全文获取类型
收费全文 | 226篇 |
免费 | 3篇 |
专业分类
林业 | 1篇 |
农学 | 10篇 |
10篇 | |
综合类 | 21篇 |
农作物 | 4篇 |
水产渔业 | 8篇 |
畜牧兽医 | 155篇 |
植物保护 | 20篇 |
出版年
2020年 | 2篇 |
2016年 | 3篇 |
2014年 | 2篇 |
2013年 | 7篇 |
2012年 | 4篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 8篇 |
2008年 | 5篇 |
2007年 | 4篇 |
2006年 | 8篇 |
2005年 | 2篇 |
2002年 | 4篇 |
2001年 | 2篇 |
1999年 | 6篇 |
1998年 | 23篇 |
1997年 | 8篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 5篇 |
1993年 | 5篇 |
1992年 | 5篇 |
1991年 | 14篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 11篇 |
1984年 | 5篇 |
1983年 | 3篇 |
1981年 | 2篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1963年 | 2篇 |
1960年 | 1篇 |
1958年 | 2篇 |
1957年 | 4篇 |
1956年 | 2篇 |
1955年 | 1篇 |
1954年 | 3篇 |
1953年 | 2篇 |
1952年 | 1篇 |
1951年 | 2篇 |
1949年 | 1篇 |
1946年 | 1篇 |
排序方式: 共有229条查询结果,搜索用时 140 毫秒
1.
Blood samples from 331 greyhounds in the Hunter Valley and nearby coastal areas of New South Wales were examined for microfilariae using a filtration technique. Species were identified by histochemical staining; 10.9% of the greyhounds were infected with Dirofilaria immitis and 3.6% with Dipetalonema reconditum. The prevalence of infection of both species was significantly greater in summer than in winter (p = less than 0.05). Infection with D. immitis was correlated with differences in age, sex, bodyweight and coat colour, and a reported lack of stamina and the presence of a cough. No significant association was found. Diethylcarbamazine citrate was used for prophylaxis in 8.8% of all the greyhounds examined. 相似文献
2.
MAYUMI L. ARIMITSU JOHN F. PIATT MICHAEL A. LITZOW ALISA A. ABOOKIRE MARC D. ROMANO and MARTIN D. ROBARDS 《Fisheries Oceanography》2008,17(2):137-146
Pacific capelin (Mallotus villosus) populations declined dramatically in the Northeastern Pacific following ocean warming after the regime shift of 1977, but little is known about the cause of the decline or the functional relationships between capelin and their environment. We assessed the distribution and abundance of spawning, non‐spawning adult and larval capelin in Glacier Bay, an estuarine fjord system in southeastern Alaska. We used principal components analysis to analyze midwater trawl and beach seine data collected between 1999 and 2004 with respect to oceanographic data and other measures of physical habitat including proximity to tidewater glaciers and potential spawning habitat. Both spawning and non‐spawning adult Pacific capelin were more likely to occur in areas closest to tidewater glaciers, and those areas were distinguished by lower temperature, higher turbidity, higher dissolved oxygen and lower chlorophyll a levels when compared with other areas of the bay. The distribution of larval Pacific capelin was not sensitive to glacial influence. Pre‐spawning females collected farther from tidewater glaciers were at a lower maturity state than those sampled closer to tidewater glaciers, and the geographic variation in the onset of spawning is likely the result of differences in the marine habitat among sub‐areas of Glacier Bay. Proximity to cold water in Glacier Bay may have provided a refuge for capelin during the recent warm years in the Gulf of Alaska. 相似文献
3.
4.
Abstract. Samples of water, sediment and fish were collected from six commercial channel catfish, Ictalurus punctalus (Rafinesque), ponds from May to October and analysed for muddy-odour producing compounds. Three episodes of off-flavour in the fish occurred in late summer. The episodes were of 2–3 months' duration and correlated with the levels of 2-methylisoborneol in water, sediment and fish. Oscillatoria agardliii was the dominant phytoplankton in ponds with off-flavour fish. Other known muddy odour-producing compounds such as geosmin, 2-isopropyl-3-mcthoxypyrazinc, 2-isobutyl-3-methoxypyrazine and 2-isobutyl-6-methoxypyrazinc were not detected in the water sediment or at concentrations greater than 5·0 ng/l. 相似文献
5.
Seeds of four winter wheat cultivars, Slejpner, Galahad, Avalon and Penman, were sown at depths ranging from 6–75 mm in soil in pots, and isoproturon or chlorotoluron was then applied to the soil surface. For chlorotoluron-treated plants (both pre- and post-emergence) the dose required to produce a 50% effect (ED50) was unaffected by depth of planting. In contrast, for isoproturon applied pre-emergence, the ED50 for both Avalon and Slejpner was strongly affected by sowing depth. Although chlorotoluron was much more active in a second experiment when applied post-emergence to Slejpner wheat, the ED50 for both herbicides increased with greater depth of sowing. Protection of wheat from isoproturon damage by deeper planting was enhanced if the adsorption capacity of the soil was raised from Kd 0.5 to 2.0 by incorporation of activated charcoal in the soil. Isoproturon entry into plants (as measured by the effect on rate of photosynthesis) was slower in those that had been sown deeper and were growing in more adsorptive soils, but there was no obvious relationship between these observations and isoproturon distribution in the soil profile. In nutrient culture the four wheat cultivars responded similarly to a range of doses of isoproturon. The chlorotoluron-sensitive cultivars, Slejpner and Galahad, were damaged by much lower doses of chlorotoluron than were Avalon and Penman. Bromus sterilis L. responded similarly to wheat with regard to its interaction with isoproturon and planting depth. Alopecurus myosuroides Huds., however, was less damaged by isoproturon when the zone above the seed was protected from the herbicide by growing the shoot through a plastic straw. 相似文献
6.
D'après les essais effectués en 1984 et 1985, un traitement hivernal à la deltaméthrine (2,5 g m.a. ha-1 ) est efficace contre Thaumetopoea pityocampa. Ces interventions réalisées en forêt par hélicoptère (ULV à 31 ha-1 ) et dans les conditions normales de la pratique montrent que l'incidence sur la faune auxiliaire est particulièrement réduite en période hivernale. 相似文献
7.
Competition between vegetative plants of wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) 总被引:1,自引:0,他引:1
Competition between wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) was studied in two experiments; a replacement series model and a technique for separation of root and shoot systems. Wild oat and wheat in association resulted in a relative yield total very close to unity showing that the two species were‘crowding for the same space’(or competing for the same resources) and were‘mutually exclusive'. Wild oat was more competitive than wheat, as shown by its aggressivity relative to wheat, relative yields, shoot dry weights and other plant attributes. The greater competitive ability of wild oat was predominantly due to its greater root competitive ability, while the two species had similar shoot competitive ability. Root competition had a much greater effect on the relative performance of the two species than did shoot competition. The effects of root and shoot competition were additive. 相似文献
8.
A simulation of herbicide use based on weed spatial distribution 总被引:3,自引:0,他引:3
Intensive field surveys were conducted to deter mine the spatial distribution of composite broad leaf and grass weed seedlings in seven maize and five soybean fields in eastern Nebraska in 1992. Farmer fields where herbicides were applied in a 38-cm band over 76-cm spaced rows were chosen for this study. Weed populations were measured in the interrow and in the band-treated intrarow. Spatial maps constructed for grass or broadleaf weeds revealed that individual species as well as species assemblages are highly aggregated. On average, 30% of the sample area in the 12 fields surveyed was free of broadleaf weeds and 70% free of grass weeds in the interrow area (no her bicide). Where a pre-emergence herbicide was applied (intrarow), 71% of the sample area was free of broadleaf weeds and 94% free of grass weeds. Increasing the threshold to some value other than zero resulted in a larger field area not requiring a herbicide application. The results of these distribution studies indicate that herbicide use could be substantially reduced if weed dis tribution maps or real-time plant sensing were available to provide information for intermittent herbicide application systems or refinement of economic thresholds. 相似文献
9.
J. MARTIN 《EPPO Bulletin》1998,28(1-2):177-182
Diagnosis of tobacco rattle tobravirus (TRV) in potato is difficult because of the existence of non-encapsidated NM-type strains, because similar symptoms are caused by potato mop-top furovirus and physiological internal rust spot and because serological tests are inefficient. The aim of this study was first to compare ELISA and PCR tests. The former was found to be ineffective, so only the PCR technique was in a survey of numerous seed-potato lots (200-tuber samples) from different EU countries. A large disparity was found according to geographical origin, with infection levels of German, Dutch and French seed potatoes of 10.3, 8.5 and 0.6%, respectively. There is a real risk that planting tubers with such infection levels will newly contaminate soil. Besides, TRV is not considered in the EU texts on marketing of seed potatoes, so there is no legal recourse if seed-potato lots are found to be TRV-infected. 相似文献
10.
Current distribution of sarcoptic mange in wombats 总被引:2,自引:0,他引:2
Objective To determine the distribution and prevalence of sarcoptic mange in wombats, particularly the common wombat ( Vombatus ursinus ).
Design Questionnaire survey in two parts.
Procedure Questionnaires were distributed to biologists, rangers, animal carers and naturalists. Part 1 of the questionnaire aimed to determine the present distribution of sarcoptic mange in wombats (103 responses). Part 2 invited respondents to assess the prevalence of sarcoptic mange in wombats over a 3 month period (four responses). Information on wombats from 66 localities was received. Each locality represented an area of about 2500 km2 .
Results Mange was observed at 93% of localities surveyed and Sarcoptes scabiei was present in common wombats at 52% of localities. Sarcoptic mange was highly prevalent (22%) in two common wombat populations in Victoria. Anecdotal evidence suggested that mange epizootics are sporadic, cause significant morbidity and mortality and have a substantial effect on local abundance. The respondents did not report sarcoptic mange in either northern hairy-nosed wombats ( Lasiorhinus krefftii ) or southern hairy-nosed wombats ( Lasiorhinus latifrons ).
Conclusions Sarcoptic mange occurs in common wombat populations throughout the range of the common wombat including Tasmania and Flinders Island. While mange epizootics are sporadic, they have the potential to threaten the long-term survival of small, remnant populations. 相似文献
Design Questionnaire survey in two parts.
Procedure Questionnaires were distributed to biologists, rangers, animal carers and naturalists. Part 1 of the questionnaire aimed to determine the present distribution of sarcoptic mange in wombats (103 responses). Part 2 invited respondents to assess the prevalence of sarcoptic mange in wombats over a 3 month period (four responses). Information on wombats from 66 localities was received. Each locality represented an area of about 2500 km
Results Mange was observed at 93% of localities surveyed and Sarcoptes scabiei was present in common wombats at 52% of localities. Sarcoptic mange was highly prevalent (22%) in two common wombat populations in Victoria. Anecdotal evidence suggested that mange epizootics are sporadic, cause significant morbidity and mortality and have a substantial effect on local abundance. The respondents did not report sarcoptic mange in either northern hairy-nosed wombats ( Lasiorhinus krefftii ) or southern hairy-nosed wombats ( Lasiorhinus latifrons ).
Conclusions Sarcoptic mange occurs in common wombat populations throughout the range of the common wombat including Tasmania and Flinders Island. While mange epizootics are sporadic, they have the potential to threaten the long-term survival of small, remnant populations. 相似文献