全文获取类型
收费全文 | 4032篇 |
免费 | 291篇 |
国内免费 | 2篇 |
专业分类
林业 | 330篇 |
农学 | 154篇 |
基础科学 | 22篇 |
1044篇 | |
综合类 | 277篇 |
农作物 | 176篇 |
水产渔业 | 354篇 |
畜牧兽医 | 1584篇 |
园艺 | 68篇 |
植物保护 | 316篇 |
出版年
2023年 | 65篇 |
2022年 | 43篇 |
2021年 | 114篇 |
2020年 | 124篇 |
2019年 | 58篇 |
2018年 | 131篇 |
2017年 | 143篇 |
2016年 | 183篇 |
2015年 | 145篇 |
2014年 | 187篇 |
2013年 | 304篇 |
2012年 | 358篇 |
2011年 | 302篇 |
2010年 | 147篇 |
2009年 | 94篇 |
2008年 | 267篇 |
2007年 | 254篇 |
2006年 | 249篇 |
2005年 | 217篇 |
2004年 | 184篇 |
2003年 | 187篇 |
2002年 | 142篇 |
2001年 | 94篇 |
2000年 | 76篇 |
1999年 | 40篇 |
1998年 | 21篇 |
1997年 | 18篇 |
1996年 | 9篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 16篇 |
1992年 | 10篇 |
1991年 | 7篇 |
1990年 | 7篇 |
1989年 | 8篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1981年 | 7篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1976年 | 4篇 |
1974年 | 5篇 |
1969年 | 4篇 |
1968年 | 5篇 |
1954年 | 2篇 |
1953年 | 3篇 |
1937年 | 2篇 |
排序方式: 共有4325条查询结果,搜索用时 360 毫秒
991.
992.
Queiroz PV Monteiro GR Macedo VP Rocha MA Batista LM Queiroz JW Jerônimo SM Ximenes MF 《Research in veterinary science》2009,86(2):267-273
The purpose of this study was to determine the clinical and laboratory profiles of canine leishmaniasis in two distinct areas. Dogs from urban and rural areas were examined. The population studied in the metropolitan area included 54 dogs. Of these, 20 (37%) animals did not present with any signs suggestive of visceral leishmaniasis (VL). Among these, only eight were confirmed negative by ELISA (rK39 and CE) and 12 dogs, clinically negative for leishmaniasis, were seropositive by ELISA (rK39 and CE). Thinness, conjunctivitis and onychogryphosis were the most frequent clinical signs in the urban areas, followed by crusty lesions, alopecia, ulcerated lesions, hyperkeratosis and exfoliation. In the metropolitan area human VL cases occurred mainly in 1991, 1992, 1999 and 2000. In the rural areas the ELISA rK39 test detected a seroprevalence of 11.3% and ELISA CE (Leishmania crude extract) of 20.6%. Thirty-nine dogs were examined 6 months after the first visit. Serological exams using rK39 antigen showed seroconversion of only one dog, whereas Leishmania CE showed seroconversion of 13 (33.4%) dogs. In this rural environment 83.3% of the positive dogs were asymptomatic. Lutzomyia intermedia and Lu. longipalpis were the most predominant sandfly vector species. Amastigotes were identified in spleen and liver fragments of symptomatic necropsied animals. PCR amplification of DNA isolated from promastigote culture indicated that the species was Leishmania chagasi. This finding suggests that delayed diagnosis and euthanasia of potentially infectious animals may occur with an increased transmission risk to sandflies and subsequently to humans. 相似文献
993.
Prieto C Vázquez A Núñez JI Alvarez E Simarro I Castro JM 《Veterinary journal (London, England : 1997)》2009,180(3):363-370
The aim of the present study was to establish the degree of diversity of porcine reproductive and respiratory virus (PRRSV) isolates that circulate in the same geographical area in different years. Nucleotide sequences of open reading frame (ORF) 5 were determined for 28 Spanish field PRRSV isolates from different years and three European-type modified live virus vaccines. Sequences were aligned using Clustal W software and a phylogenetic tree constructed using the neighbour joining method. The results of pairwise homology comparisons of nucleotide and deduced amino acid sequences of these PRRSV isolates indicate a tendency for heterogeneity to increase with time. The study of the phylogenetic tree revealed that Spanish PRRSV isolates constitute two well-defined clades and a group of unrelated sequences. The observed heterogeneity does not appear to be due to temporal evolution exclusively. Early and recent isolates group themselves into different clusters independently of the time of isolation, indicating the co-circulation of different variants and the maintenance of variants of the original isolates in the field. 相似文献
994.
Maia C Ramada J Cristóvão JM Gonçalves L Campino L 《Veterinary journal (London, England : 1997)》2009,179(1):142-144
Serology, bone marrow (BM)-, lymph node (LN)- and whole blood-polymerase chain reaction (PCR) were evaluated as potential reference tests for the diagnosis of canine leishmaniasis. A high degree of agreement (91.0%) was observed between Leishmania cultures and serology or BM/LN-PCR. In the light of these results as well as the access to biological test material and the cost of each method, LN-PCR is recommended for the diagnosis or therapeutic control of canine leishmaniasis, but BM-PCR is a suitable alternative in dogs without detectable adenomegaly. For large-scale epidemiological field studies, antibody detection is appropriate and whole blood-PCR can be used to complement the serological results. 相似文献
995.
996.
Marta Amat Xavier Manteca Valentina M. Mariotti José Luís Ruiz de la Torre Jaume Fatjó 《Journal of Veterinary Behavior: Clinical Applications and Research》2009,4(3):111-117
A high percentage of aggression problems and a tendency to display noninhibited aggression in the English cocker spaniel (ECS) have been suggested by many authors. The authors of this paper designed a retrospective study to analyze the aggressive behavior of 145 ECSs presented for aggression problems to the Animal Behavior Service at the Barcelona School of Veterinary Medicine's veterinary teaching hospital. Aggressive ECSs were compared with a population of dogs of the same breed presented for a behavior problem other than aggression and with a population of aggressive dogs of other breeds. The most common forms of aggression in the ECS were owner-directed aggression (67.6%), aggression toward unfamiliar people (18.4%), aggression toward unfamiliar dogs (10.1%), and aggression toward family dogs (3.3%).Owner-directed aggression was more common in the ECS than in other breeds, although in similar contexts. In the ECS, the golden coat color was more common in the aggressive dogs than in nonaggressive dogs. ECSs showed impulsive aggression more frequently than aggressive dogs of other breeds. The aim of the study was to analyze cases of aggressive ECSs seen in a referral practice. 相似文献
997.
Fatima Maria de Souza Moreira Teotonio Soares de Carvalho José Oswaldo Siqueira 《Biology and Fertility of Soils》2010,46(8):771-779
The aim of this study was to evaluate the effects of lime, fertilizers, mycorrhizal fungi, and selected rhizobia strains on the growth of four woody legume species, Albizia lebbeck (L.) Benth., Enterolobium contortisiliquum (Vell.) Morong., Leucaena leucocephala (Lam.) de Wit, and Sesbania virgata (Cav.) Pers. in a low-fertility soil. The experiment was conducted under greenhouse condition in plastic pots (4 kg). Eight treatments and eight replicates per treatment were performed in a completely randomized design. The treatments were: (1) complete treatment (C) (NPK fertilization?+?micronutrients?+?liming?+?MR that is inoculation with mycorrhizal fungi and rhizobia); (2) C minus N (C???N that is as C without the addition of N); (3) C???N???M (as C???N without inoculation with arbuscular mycorrhizal fungi (AMF)); (4) C???N??R (as C???N without inoculation of rhizobia); (5) C???N???liming (as C???N without liming); (6) C???N???micro (as C???N without addition of micronutrients); (7) C???N???P (as C???N without addition of P); (8) control without fertilization, liming, and without inoculation with AMF and rhizobia. After 4 months of growth, we determined the yield of individual plants, nodulation, mycorrhizal colonization, and nutrient contents. Phosphorus was the most limiting nutrient for plant growth, followed by nitrogen. L. leucocephala and S. virgata had the most robust response to the addition of micronutrients and liming, showing an increase in nutrient content, plant height, and root and shoot dry matter. When compared to the single inoculation, the dual inoculation increased growth of all plants, except that of A. lebbeck, which did not respond to either rhizobia or mycorrhizal fungi inoculation. 相似文献
998.
Hamidreza Nooryazdan Hervé Serieys Roberto Baciliéri Jacques David André Bervillé 《Genetic Resources and Crop Evolution》2010,57(1):27-39
Seventy-seven wild sunflower accessions from USA were compared in France (Mauguio) for 13 quantitative characters using multivariate
methods, including clustering, principal component and canonical discriminate analyzes to assess the patterns of morphological
and climatic variation. Geographic and climatic data from their sampled sites such as latitude, longitude, elevation, rain
fall, temperature, number of rain fall days, temperature range, and sunniness were also analyzed and we sought for correlations
of climatic variables and morphological traits. Climatic data clustered the accessions into four groups. Principal component
analysis was used to summarize the characteristic habits of annual wild sunflower sampled sites in terms of geography and
climates, thus we characterized the ecogeographical profiles of wild sunflowers. As we studied the traits in a common environment
we speculated whether local adaptation patterns are sustained by our data. Indeed traits shared by accessions that belong
to climatic clusters are suggested to be due to local adaptation. 相似文献
999.
The growth and reproduction of Eudrilus eugeniae were evaluated in four animal species wastes under laboratory conditions. Two hatchlings were introduced in 100 g of each animal waste i.e. cow, sheep, pig, and chicken after 15 days of pre-composting. Biomass gain, mortality, sexual maturity, and cocoons production were monitored periodically for 21 weeks. No mortality was observed in any waste. The maximum weight gain per worm and the highest growth rate per worm per week were obtained in chicken waste. Net biomass gain per worm were 1.01 ± 0.52 g, 1.318 ± 0.07 g, 0.87 ± 0.1 g, and 1.69 ± 0.15 g respectively for cow, sheep, pig, and chicken wastes. The highest number of cocoons produced per worm per day was obtained in chicken waste followed in decreasing order by sheep, cow, and pig waste. The mean number of cocoons produced per worm per day in chicken waste was 40.87% greater than these produced per day in pig waste.Among the four animal species, chicken, sheep, and cow were the most favourable wastes for the growth and reproduction of E. eugeniae, and hence can be recommended as feed materials in large scale vermicomposting facilities. 相似文献
1000.
André Costa da Silva Paulo Estev?o de Souza José Eduardo Brasil Pereira Pinto Bruno Marques da Silva Douglas Carvalho Amaral Eudes de Arruda Carvalho 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(4):865-871
The objective of the work was to evaluate the effect of essential oils as a preventive treatment to control Asian soybean rust. Initially the fungitoxic effect of the essential oils of Hyptis marrubioides, Aloysia gratissima and Cordia verbenacea was tested on the urediniospores of Phakopsora pachyrhizi, through in vitro tests. The in vivo test was set up in a greenhouse, using cultivar MGBR-46. The treatments consisted of the three oils at different concentrations, a fungicide based on pyraclostrobin + epoxyconazole and a control. To verify the potential of the essential oils in preventive treatment, inoculation was conducted at 0, 6, 12 and 24?h intervals, after application of the treatments. All treatments inhibited 100% of Phakopsora pachyrhizi germination. In the in vivo test, it was observed that all of the oils were efficient in controlling soybean rust, by preventive treatment, mainly at the higher concentrations. Efficiency of the oils was reduced with the increase of the interval between the application of the treatments and the onset of the pathogen. The essential oils, at the tested dosages, were not as efficient as the pyraclostrobin + epoxyconazole based fungicide. 相似文献