全文获取类型
收费全文 | 2038篇 |
免费 | 100篇 |
国内免费 | 12篇 |
专业分类
林业 | 168篇 |
农学 | 107篇 |
基础科学 | 25篇 |
520篇 | |
综合类 | 162篇 |
农作物 | 93篇 |
水产渔业 | 150篇 |
畜牧兽医 | 736篇 |
园艺 | 47篇 |
植物保护 | 142篇 |
出版年
2024年 | 6篇 |
2023年 | 7篇 |
2022年 | 24篇 |
2021年 | 39篇 |
2020年 | 60篇 |
2019年 | 56篇 |
2018年 | 64篇 |
2017年 | 64篇 |
2016年 | 73篇 |
2015年 | 51篇 |
2014年 | 84篇 |
2013年 | 128篇 |
2012年 | 122篇 |
2011年 | 141篇 |
2010年 | 104篇 |
2009年 | 103篇 |
2008年 | 145篇 |
2007年 | 127篇 |
2006年 | 102篇 |
2005年 | 91篇 |
2004年 | 91篇 |
2003年 | 83篇 |
2002年 | 102篇 |
2001年 | 34篇 |
2000年 | 19篇 |
1999年 | 16篇 |
1998年 | 17篇 |
1997年 | 14篇 |
1996年 | 15篇 |
1995年 | 27篇 |
1994年 | 10篇 |
1993年 | 12篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1985年 | 13篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1976年 | 4篇 |
1974年 | 3篇 |
1971年 | 4篇 |
排序方式: 共有2150条查询结果,搜索用时 0 毫秒
31.
Lena Steng?rde Madeleine Tr?vén Ulf Emanuelson Kjell Holtenius Jan Hultgren Rauni Niskanen 《Acta veterinaria Scandinavica》2008,50(1):31
Background
Body condition score and blood profiles have been used to monitor management and herd health in dairy cows. The aim of this study was to examine BCS and extended metabolic profiles, reflecting both energy metabolism and liver status around calving in high-producing herds with a high incidence of abomasal displacement and ketosis and to evaluate if such profiles can be used at herd level to pinpoint specific herd problems.Methods
Body condition score and metabolic profiles around calving in five high-producing herds with high incidences of abomasal displacement and ketosis were assessed using linear mixed models (94 cows, 326 examinations). Cows were examined and blood sampled every three weeks from four weeks ante partum (ap) to nine weeks postpartum (pp). Blood parameters studied were glucose, fructosamine, non-esterified fatty acids (NEFA), insulin, β-hydroxybutyrate, aspartate aminotransferase, glutamate dehydrogenase, haptoglobin and cholesterol.Results
All herds had overconditioned dry cows that lost body condition substantially the first 4–6 weeks pp. Two herds had elevated levels of NEFA ap and three herds had elevated levels pp. One herd had low levels of insulin ap and low levels of cholesterol pp. Haptoglobin was detected pp in all herds and its usefulness is discussed.Conclusion
NEFA was the parameter that most closely reflected the body condition losses while these losses were not seen in glucose and fructosamine levels. Insulin and cholesterol were potentially useful in herd profiles but need further investigation. Increased glutamate dehydrogenase suggested liver cell damage in all herds. 相似文献32.
Berghoff N Suchodolski JS Steiner JM 《Veterinary journal (London, England : 1997)》2012,191(3):306-311
The aim of this study was to evaluate the association between serum methylmalonic acid (MMA), a proposed marker of cellular cobalamin deficiency, and serum cobalamin concentrations in dogs. Serum samples from 555 dogs were grouped according to their serum cobalamin concentrations (<150 ng/L to 1000 ng/L). Additionally, serum samples were collected from 43 healthy dogs to calculate a reference interval for canine serum MMA. MMA was measured using a GC/MS method. Groups were compared using a Kruskal-Wallis test with Dunn's post test. Proportions of dogs above the upper limit of the reference interval were calculated and a χ2-test for trend was performed to evaluate the association between serum cobalamin and MMA concentrations. The reference interval for serum MMA was calculated to be 414.7-1192.5 nmol/L. Dogs with serum cobalamin concentrations <251 ng/L had significantly higher MMA concentrations (P<0.05) and the χ2-test for trend showed a trend for increasing serum MMA concentrations with decreasing serum cobalamin concentrations (P<0.0001). Additionally, a number of dogs with normal serum cobalamin concentrations had increased serum MMA concentrations, suggesting that some of these dogs may have cobalamin deficiency on a cellular level. Further studies are warranted to determine if these dogs should receive cobalamin supplementation. 相似文献
33.
34.
35.
Robert J Brosnan Bruno H Pypendop Chalon R Majewski‐Tiedeken Yael Shilo‐Benjamini Jan E Ilkiw 《Veterinary anaesthesia and analgesia》2013,40(2):225-228
ObjectiveTo test whether naltrexone, an opioid receptor antagonist, affects the minimum alveolar concentration (MAC) of isoflurane in cats, a species that is relatively resistant to the general anesthetic sparing effects of most opioids.Study designRandomized, crossover, placebo-controlled, blinded experimental design.AnimalsSix healthy adult cats weighing 4.9 ± 0.7 kg.MethodsThe cats were studied twice. In the first study, baseline isoflurane MAC was measured in duplicate. The drug (saline control or 0.6 mg kg?1 naltrexone) was administered IV every 40–60 minutes, and isoflurane MAC was re-measured. In the second study, cats received the second drug treatment using identical methods 2 weeks later.ResultsIsoflurane MAC was 2.03 ± 0.12% and was unchanged from baseline following saline or naltrexone administration.Conclusion and clinical relevanceMinimum alveolar concentration was unaffected by naltrexone. Because MAC in cats is unaffected by at least some mu-opioid agonists and antagonists, spinal neurons that are directly modulated by mu-opioid receptors in this species cannot be the neuroanatomic sites responsible for immobility from inhaled anesthetics. 相似文献
36.
Transmissible spongiform encephalopathies (TSEs) or prion diseases are unique disorders that are not caused by infectious micro-organisms (bacteria or fungi), viruses or parasites, but rather seem to be the result of an infectious protein. TSEs are comprised of fatal neurodegenerative disorders affecting both human and animals. Prion diseases cause sponge-like degeneration of neuronal tissue and include (among others) Creutzfeldt–Jacob disease in humans, bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep. TSEs are characterized by the formation and accumulation of transmissible (infectious) disease-associated protease-resistant prion protein (PrPSc), mainly in tissues of the central nervous system. The exact molecular processes behind the conversion of PrPC into PrPSc are not clearly understood. Correlations between prion protein polymorphisms and disease have been found, however in what way these polymorphisms influence the conversion processes remains an enigma; is stabilization or destabilization of the prion protein the basis for a higher conversion propensity? Apart from the disease-associated polymorphisms of the prion protein, the molecular processes underlying conversion are not understood. There are some notions as to which regions of the prion protein are involved in refolding of PrPC into PrPSc and where the most drastic structural changes take place. Direct interactions between PrPC molecules and/or PrPSc are likely at the basis of conversion, however which specific amino acid domains are involved and to what extent these domains contribute to conversion resistance/sensitivity of the prion protein or the species barrier is still unknown. 相似文献
37.
Anki Roxström Erling Strandberg Britt Berglund Ulf Emanuelson Jan Philipsson 《Acta Agriculturae Scandinavica, Section A - Animal Sciences》2013,63(1):7-14
The main objective of this study was to estimate genetic correlations between fertility and production traits in first, second and third lactations as well as between fertility traits measured in the same way at different ages. The fertility traits studied were: number of inseminations per service period, number of treatments for reproductive disturbances, interval between first and last inseminations, interval between calving and first insemination, and interval between calving and last insemination. Early milk production was measured as the average of the energy-corrected milk yield at the second and third monthly testdays in a lactation. The number of records was approximately 450 000, 350 000, 180 000 and 75 000 in the heifer period, first, second, and third lactations, respectively. A linear, trivariate model that included the effects of herd-year, year, month, age and sire of the cow was applied. To reduce the effect of ongoing selection, 305-days kg protein production in first lactation was included as a variate in all of the analyses. Correlations between the herd-year effects indicated that factors of herd-year level conducive to increased production had a tendency to increase the number of inseminations as well as the number of reproductive treatments, although there was an earlier start and termination of the insemination period. Genetic correlations between fertility traits and production were in the range of 0.2-0.4, all of them unfavourable and higher at later parities. The genetic correlations between fertility traits in the heifer period and the same traits in first lactation were 0.7. Genetic correlations between the first and second lactation varied between 0.7 and 0.9, and between the second and third lactation they were all 0.9 or higher. In conclusion, fertility and production traits need to be selected for simultaneously if fertility is going to be maintained along further genetic improvement on production, and such selection should include fertility results from lactating cows. 相似文献
38.
Janusz A Madej Jan P Madej Piotr Dziegiel Bartosz Pula Marcin Nowak 《Acta veterinaria Scandinavica》2013,55(1):73
Background
The study aimed at examining hypoxia-inducible factor (HIF)1α expression in adenocarcinomas and adenomas in bitches in regard to tumour malignancy grade, proliferation, apoptosis and vascularisation. Therefore, paraffin sections of 15 adenomas and 64 adenocarcinomas sampled from 79 dogs aged 6 to 16 years were analysed.Results
A significantly higher HIF-1α expression was noted in adenocarcinomas in comparison to adenomas (P < 0.0004). Moreover, HIF-1α expression in adenocarcinomas correlated positively with tumour malignancy grade (r = 0.59, P < 0.05), Ki-67 antigen expression (r = 0.43; P < 0.0005), TUNEL-positive cells (r = 0.62, P < 0001) and tumour vascularity measured by quantification of vessels characterized by the expression of von Willebrand Factor (r = 0.57, P < 0.05).Conclusion
Results of this study indicate a similar biological role of HIF-1α in dogs and in humans, which may confirm suitability of the animal model in investigations on progression of tumours in humans. 相似文献39.
Hygienic and ecological risks connected with utilization of animal manures and biosolids in agriculture 总被引:2,自引:0,他引:2
In recent years the fate of human and animal pathogen microorganisms as a potential pollutant of the environment has been paid increased attention. Substantial quantities of these compounds and their metabolites are excreted, flushed down the drain, discarded as waste, or left over in animal feedlots. After passing to the sewer, several of these compounds are not adequately eliminated by the methods that are currently used in sewage treatment. Substantial quantities of biosolids and livestock manure end up on agricultural land. Effective sanitation of the environment, particularly of some of its special parts, which can be a source of spreading of diseases, plays an important role in prevention of infectious diseases. In this respect special attention should be paid to the disinfection of infected farm animal excrements. Sanitation of excrements should, on the one hand, ensure effective inhibition of infectious agents and, on the other hand, comply with the requirement of preserving the composition of the manure so it can be used in agricultural production. 相似文献
40.
Joeke Nijboer Marcus Clauss Moniek Olsthoorn Wendy Noordermeer Tjalling R Huisman Celine Verheyen Jan van der Kuilen W Streich Jürgen Anton C Beynen 《Journal of zoo and wildlife medicine》2006,37(3):366-372
A high intake of easily fermentable carbohydrates and a low intake of fiber material are generally regarded as major factors affecting the health of captive langurs. The effect on fecal consistency of excluding fruits and vegetables from the diet was evaluated in Javan langurs (Trachypithecus auratus auratus). Cross-over trials were carried out at Rotterdam Zoo and at the Apenheul Zoo, The Netherlands. During the first and third dietary period, the langurs were fed their usual diet, which contained fruits, vegetables, langur pellets, and browse. During the second period, the vegetables and fruits were excluded from the diet and the diet essentially consisted of pellets and browse. Feces consistency was scored using a fecal score chart developed for langurs. During the second feeding period the feces consistency improved significantly in animals at both zoos. Across all trials, a firmer feces consistency was correlated with an increase in dietary cell wall (measured as neutral detergent fiber) and a decrease in dietary water. It is suggested that the combined decrease in the intake of soluble sugars, the increase of fiber intake, and a lower amount of dietary water in the diet resulted in more solid stools. The results indicate that a dietary neutral detergent fiber content of approximately 46% in dry matter will result in a feces consistency indicative of undisturbed gut function. 相似文献