全文获取类型
收费全文 | 166432篇 |
免费 | 8916篇 |
国内免费 | 124篇 |
专业分类
林业 | 7403篇 |
农学 | 5305篇 |
基础科学 | 973篇 |
20895篇 | |
综合类 | 29078篇 |
农作物 | 6685篇 |
水产渔业 | 8192篇 |
畜牧兽医 | 83795篇 |
园艺 | 2198篇 |
植物保护 | 10948篇 |
出版年
2019年 | 1631篇 |
2018年 | 2411篇 |
2017年 | 2760篇 |
2016年 | 2491篇 |
2015年 | 2115篇 |
2014年 | 2663篇 |
2013年 | 6429篇 |
2012年 | 4960篇 |
2011年 | 6029篇 |
2010年 | 3885篇 |
2009年 | 4024篇 |
2008年 | 5885篇 |
2007年 | 5645篇 |
2006年 | 5263篇 |
2005年 | 4968篇 |
2004年 | 4700篇 |
2003年 | 4820篇 |
2002年 | 4378篇 |
2001年 | 5077篇 |
2000年 | 5110篇 |
1999年 | 4099篇 |
1998年 | 1765篇 |
1997年 | 1700篇 |
1996年 | 1590篇 |
1995年 | 1879篇 |
1994年 | 1697篇 |
1993年 | 1562篇 |
1992年 | 3156篇 |
1991年 | 3314篇 |
1990年 | 3198篇 |
1989年 | 3214篇 |
1988年 | 2950篇 |
1987年 | 2968篇 |
1986年 | 3051篇 |
1985年 | 2931篇 |
1984年 | 2388篇 |
1983年 | 2149篇 |
1982年 | 1465篇 |
1979年 | 2209篇 |
1978年 | 1793篇 |
1977年 | 1508篇 |
1976年 | 1535篇 |
1975年 | 1636篇 |
1974年 | 2007篇 |
1973年 | 1939篇 |
1972年 | 1892篇 |
1971年 | 1821篇 |
1970年 | 1692篇 |
1969年 | 1740篇 |
1967年 | 1527篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
Essential fatty acids supplementation in different-stage atopic dogs fed on a controlled diet 总被引:1,自引:0,他引:1
Abba C Mussa PP Vercelli A Raviri G 《Journal of animal physiology and animal nutrition》2005,89(3-6):203-207
The aim of this trial was to evaluate the effects of polyunsaturated fatty acid (PUFA) supplementation in different-stages atopic dogs fed on a controlled diet. Twenty-two non-seasonal atopic dogs of different breeds and ages were included in the 2-month trial. All the patients were given an essential fatty acid (EFA) supplementation [17 mg/kg eicosapentaenoic acid (EPA) + 5 mg/kg docosahexaenoic acid (DHA) + 35 mg/kg gammalinolenic acid (GLA)], the global (diet + supplementation) omega-6 to omega-3 ratio was 5.5-1. Two groups of dogs were considered: group A 'pre-immunotherapy' (15 cases) included dogs with early stages atopy, which had not been submitted to any treatment yet; group B 'post-immunotherapy' (seven cases) included dogs with chronic atopy immunotherapy non-responsive. Clinical evaluations were performed at the beginning, on day 30 and at the end of the trial. Blood serum fatty acids profile was determined at the beginning and at the end of the study. Better clinical results were obtained in group A, a great difference was found between the two groups on pruritus score. Serum arachidonic acid (AA) was significantly lower at the end of the trial in group A while GLA was significantly higher in group B. We hypothesized that different-stages atopic dogs could have different response to EFA supplementation, maybe because of a different fatty acids metabolism. Early stages cases seem to be more responsive to EFA supplementation. 相似文献
992.
993.
Bersenas AM Mathews KA Allen DG Conlon PD 《American journal of veterinary research》2005,66(3):425-431
OBJECTIVE: To identify the normal gastric acid secretion profile in dogs and determine the degree of gastric acid suppression associated with 4 gastric acid suppressants. ANIMALS: 12 healthy Beagles. PROCEDURE: Intragastric pH was measured continuously for 24-hour periods with a digital recording system placed via a gastrostomy tube. Baseline measurements were obtained when food was withheld and when dogs were fed a standard diet. Dogs were then treated with ranitidine (2 mg/kg, IV, q 12 h), famotidine (0.5 mg/kg, IV, q 12 h), pantoprazole (1 mg/kg, IV, q 24 h), omeprazole (1 mg/kg, PO, q 24 h), or saline solution for 7 days; intragastric pH was recorded on days 0, 2, and 6. Subsequently, the effects of administering famotidine (0.5 mg/kg, IV, q 8 h; 6 dogs) and omeprazole as a suspension (1 mg/kg, PO, q 12 h; 6 dogs) were evaluated. Median 24-hour intragastric pH, percentage of time pH was > or = 3, and percentage of time pH was > or = 4 were determined. RESULTS: Median pH, percentage of time pH was > or = 3, and percentage of time pH was > or = 4 were all significantly higher when food was withheld than when dogs were fed. Famotidine, pantoprazole, and omeprazole significantly suppressed gastric acid secretion, compared with saline solution, as determined on the basis of median 24-hour pH and percentages of time pH was > or = 3 or > or = 4. However, ranitidine did not. Omeprazole suspension suppressed gastric acid secretion. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that in healthy dogs, famotidine, pantoprazole, and omeprazole significantly suppress gastric acid secretion. Twice daily administration of a suspension of omeprazole, was the only regimen tested that approached the potential therapeutic efficacy for acid-related disease when assessed by criteria used for human patients. 相似文献
994.
De Miranda Neto MH Defani MA Fregonesi CE Natali MR Pereira A 《Anatomia, histologia, embryologia》2005,34(3):154-158
Summary In this study we investigated the effect of the acetyl-L-carnitine (ALC) supplementation on the myenteric neurons of the jejunum of rats made diabetic at the age of 105 days by streptozotocin (35 mg/kg body weight). Four groups were used: non-diabetic (C), non-diabetic supplemented with ALC (CC), diabetic (D), diabetic supplemented with ALC (DC). After 15 weeks of diabetes induction the blood was collected by cardiac puncture to evaluate glycaemia and glycated haemoglobin. Next the animals were killed and the jejunum was collected and subjected to whole-mount preparation to evidence the myenteric neurons through the histochemical technique of the NADH-diaphorase. The neuronal counts were made in 80 microscopic fields, in tissue samples of five animals of each group. The profiles of the cell bodies of 1000 neurons per group were analysed. Diabetes induced a significant increase in the area of the cell body and decrease in the number of NADH-diaphorase positive myoenteric neurons. ALC suplementation to the diabetic group promoted smaller hypertrophic effects and less neuronal loss than in the myoenteric neurons of the diabetic rats, and in addition diminished the body weight decrease and reduced the fasting glycaemia. 相似文献
995.
This paper estimates the financial incentive to control paratuberculosis on dairy farms by establishing the level of expenditure that would minimise the total cost of the disease (output losses plus control expenditure). Given the late onset of the clinical signs and the lack of treatments, control was focused on minimising the financial impact of paratuberculosis by adjusting the dairy cow replacement policy. The optimum replacement policies for disease-free herds and infected herds were compared by using dynamic programming. At the standard settings, the disease justified adjusting the culling policy; under constant bioeconomic assumptions, it reduced the expected annuity from milk production under the optimal replacement policy by about 10 per cent (27 pounds sterling per cow annually), a considerably lower figure than for other major endemic diseases that affect dairy cows in the uk. The effect was even less at lower milk prices, suggesting that there is at present little incentive for dairy farmers to put more resources into controlling the disease. However, the incentive could be increased if more information were available about how best to manage the disease under specific farm circumstances. Any effect that paratuberculosis may have on the future demand for milk and hence on milk prices would also be an important consideration. 相似文献
996.
Duchatel JP Todd D Curry A Smyth JA Bustin JC Vindevogel H 《The Veterinary record》2005,157(14):413-415
Nineteen racing pigeons aged from one to five years were examined postmortem. pcr tests showed that the spleens of 16 of them were positive for pigeon circovirus, the livers of six were positive, and blood from one of them was positive for the virus. Five of 44 embryos in embryonated eggs collected from three lofts were positive by pcr, but swabs taken from the crops of 64 adult birds which were feeding one- to 10-day-old squabs in these three lofts were negative for the viral dna. 相似文献
997.
J. M. Alonso G. S. Rosa M. F. Marsiglia A. L. Garcia Alves C. A. Rodrigues M. J. Watanabe J. C. Figueiredo Pantoja C. A. Hussni 《Equine Veterinary Education》2020,32(3):146-149
Epiploic foramen entrapment (EFE) is one of the most common causes of small intestinal strangulation in horses. Cribbing and previous episodes of colic are suggested as risk factors for its occurrence. The aim of this study was to correlate the height, weight, breed, gender and age to the epiploic foramen (EF) length. Forty-three horses were submitted to post-mortem measurement of epiploic foramen with abdominal and thoracic organs positioned in situ. After data collection, linear regression between EF length and the explanatory variables was performed. None of the post-mortem physical variables was associated with EF length, supporting the hypothesis that there is no association between EF length and age, and that increased intra-abdominal pressure is the most important factor predisposing to EFE recurrence. 相似文献
998.
999.
Gunn GJ Saatkamp HW Humphry RW Stott AW 《Preventive veterinary medicine》2005,72(1-2):149-62; discussion 215-9
The objective of this paper is to present a preliminary assessment of variation in the economic impact of bovine viral diarrhoea virus (BVDV) at dairy farm level between a sample of nations within the EU and hence assess differences in pressure to respond to this disease that may be impeding progress in control and hence restricting collective benefits from healthier livestock. We used a questionnaire to obtain national average values of key epidemiological and economic parameters for a typical dairy farm from BVDV experts in the countries concerned. These parameters were converted into assessments of economic impact using a computer simulation model. Uncontrolled output losses for a BVDV-na?ve herd with virus introduced in year 1 of a 10-year epidemic represented 22, 7, 8, 5, 8 and 20% of the BVDV-free annuity for the UK, Northern Portugal, Holland, Norway, Italy and Germany, respectively. Differences between countries will be widened by differences in the risk of acquiring BVDV. These will be much reduced in countries, such as Norway that have a national BVDV eradication programme. Farmers in such countries can therefore justify spending much less on maintaining BVDV-free status than BVDV-free farms in other countries. This result illustrates the paradox that in countries where BVDV prevalence is high, farmers have least to gain from unilateral BVDV eradication because of the high cost of maintaining freedom from the disease. We discuss this issue in the light of increasing recognition at international level of the importance of BVDV control. 相似文献
1000.
2005 Guidelines for the diagnosis, prevention and management of heartworm (Dirofilaria immitis) infection in dogs 总被引:2,自引:0,他引:2