全文获取类型
收费全文 | 1116篇 |
免费 | 106篇 |
专业分类
林业 | 78篇 |
农学 | 59篇 |
基础科学 | 4篇 |
230篇 | |
综合类 | 26篇 |
农作物 | 69篇 |
水产渔业 | 130篇 |
畜牧兽医 | 538篇 |
园艺 | 22篇 |
植物保护 | 66篇 |
出版年
2024年 | 3篇 |
2023年 | 21篇 |
2022年 | 36篇 |
2021年 | 70篇 |
2020年 | 77篇 |
2019年 | 83篇 |
2018年 | 60篇 |
2017年 | 60篇 |
2016年 | 65篇 |
2015年 | 58篇 |
2014年 | 50篇 |
2013年 | 53篇 |
2012年 | 88篇 |
2011年 | 76篇 |
2010年 | 53篇 |
2009年 | 36篇 |
2008年 | 53篇 |
2007年 | 62篇 |
2006年 | 39篇 |
2005年 | 23篇 |
2004年 | 30篇 |
2003年 | 34篇 |
2002年 | 24篇 |
2001年 | 19篇 |
2000年 | 22篇 |
1999年 | 8篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1980年 | 1篇 |
排序方式: 共有1222条查询结果,搜索用时 18 毫秒
991.
Paulo Augusto Vianna Barroso Lúcia Vieira Hoffmann Rodolfo Barbosa de Freitas Carlos Eduardo de Araújo Batista Milena Ferreira Alves Uiara Cavalcante Silva Francisco Pereira de Andrade 《Genetic Resources and Crop Evolution》2010,57(3):343-349
Gossypium mustelinum Miers ex Watt is a native from Northeastern Brazil and belongs to the primary gene pool of the cultivated cotton. The unique
places where the species was known to occur were visited to plan ex situ and in situ preservation. Two populations at Caicó became extinct, and only eleven individuals were found. At Jaguarari, although one
population became extinct, a new one was localized with approximately 500 adult plants, where a fence avoided cattle feeding.
The population from Macururé consisted of 28 plants protected from animals by thorns of Bromelia laciniosa Mart. ex Schult. f. Thirteen SSR primer pairs amplified 40 alleles, among which 30% were exclusive of one of the populations.
The genetic differences between populations represented 58.3% of the total genetic variation observed. The high genetic distances
are likely to be caused by geographical isolation as well as by the small number of individuals which contribute to new generations,
and consequential genetic drift. 相似文献
992.
Floudas D Binder M Riley R Barry K Blanchette RA Henrissat B Martínez AT Otillar R Spatafora JW Yadav JS Aerts A Benoit I Boyd A Carlson A Copeland A Coutinho PM de Vries RP Ferreira P Findley K Foster B Gaskell J Glotzer D Górecki P Heitman J Hesse C Hori C Igarashi K Jurgens JA Kallen N Kersten P Kohler A Kües U Kumar TK Kuo A LaButti K Larrondo LF Lindquist E Ling A Lombard V Lucas S Lundell T Martin R McLaughlin DJ Morgenstern I Morin E Murat C Nagy LG Nolan M Ohm RA Patyshakuliyeva A 《Science (New York, N.Y.)》2012,336(6089):1715-1719
Wood is a major pool of organic carbon that is highly resistant to decay, owing largely to the presence of lignin. The only organisms capable of substantial lignin decay are white rot fungi in the Agaricomycetes, which also contains non-lignin-degrading brown rot and ectomycorrhizal species. Comparative analyses of 31 fungal genomes (12 generated for this study) suggest that lignin-degrading peroxidases expanded in the lineage leading to the ancestor of the Agaricomycetes, which is reconstructed as a white rot species, and then contracted in parallel lineages leading to brown rot and mycorrhizal species. Molecular clock analyses suggest that the origin of lignin degradation might have coincided with the sharp decrease in the rate of organic carbon burial around the end of the Carboniferous period. 相似文献
993.
994.
Souza FN Blagitz MG Latorre AO Ramos Sanchez EM Batista CF Weigel RA Renno FP Sucupira MC Della Libera AM 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2012,74(2):221-225
The present study assesses the oxidative burst activity from polymorphonuclear leukocytes (PMNLs) from bovine leukemia virus (BLV)-infected cows. Fifteen clinically healthy cows were divided into serologically positive cows without any hematological alteration, serologically positive animals with persistent lymphocytosis (PL) and healthy serologically negative cows. The oxidative burst activity from the PMNLs was evaluated by flow cytometry using 2',7'-dichlorofluorescein diacetate as a probe. PMNLs from each cow were incubated with heat-killed Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) to stimulate oxidative burst activity. The results of the present work showed no significant difference in the oxidative burst activity without any stimulus and elicited by S. aureus. Conversely, a decrease in the oxidative burst index induced by E. coli in PMNLs was observed in BLV-infected cows. 相似文献
995.
996.
Quinteiro-Filho WM Rodrigues MV Ribeiro A Ferraz-de-Paula V Pinheiro ML Sá LR Ferreira AJ Palermo-Neto J 《Journal of animal science》2012,90(6):1986-1994
Studies on the environmental consequences of stress are relevant for economic and animal welfare reasons. We recently reported that long-term heat stressors (31 ± 1°C and 36 ± 1°C for 10 h/d) applied to broiler chickens (Gallus gallus domesticus) from d 35 to 42 of life increased serum corticosterone concentrations, decreased performance variables and the macrophage oxidative burst, and produced mild, multifocal acute enteritis. Being cognizant of the relevance of acute heat stress on tropical and subtropical poultry production, we designed the current experiment to analyze, from a neuroimmune perspective, the effects of an acute heat stress (31 ± 1°C for 10 h on d 35 of life) on serum corticosterone, performance variables, intestinal histology, and peritoneal macrophage activity in chickens. We demonstrated that the acute heat stress increased serum corticosterone concentrations and mortality and decreased food intake, BW gain, and feed conversion (P < 0.05). We did not find changes in the relative weights of the spleen, thymus, and bursa of Fabricius (P > 0.05). Increases in the basal and the Staphylococcus aureus-induced macrophage oxidative bursts and a decrease in the percentage of macrophages performing phagocytosis were also observed. Finally, mild, multifocal acute enteritis, characterized by the increased presence of lymphocytes and plasmocytes within the lamina propria of the jejunum, was also observed. We found that the stress-induced hypothalamic-pituitary-adrenal axis activation was responsible for the negative effects observed on chicken performance and immune function as well as for the changes in the intestinal mucosa. The data presented here corroborate with those presented in other studies in the field of neuroimmunomodulation and open new avenues for the improvement of broiler chicken welfare and production performance. 相似文献
997.
Carvalho CO Chagas AC Cotinguiba F Furlan M Brito LG Chaves FC Stephan MP Bizzo HR Amarante AF 《Veterinary parasitology》2012,183(3-4):260-268
The indiscriminate use of anthelmintics has resulted in the establishment of parasite resistance. Thus, this study aimed to evaluate the in vitro antiparasitic effect of plant extracts on Haemonchus contortus in sheep and the in vivo effect on Strongyloides venezuelensis in Rattus norvegicus. The plant extracts from Piper tuberculatum, Lippia sidoides, Mentha piperita, Hura crepitans and Carapa guianensis, produced at different research institutions, were chemically analyzed and evaluated through the egg hatch test (EHT) and larval development test (LDT) in H. contortus. P. tuberculatum (150 and 250 mg kg(-1) of body weight) was evaluated for its anthelmintic action on R. norvegicus experimentally infected with S. venezuelensis. In the EHT, the LC(50) and LC(90) of the extracts were respectively as follows: 0.031 and 0.09 mg mL(-1) for P. tuberculatum, 0.04 and 0.13 mg mL(-1) for L. sidoides, 0.037 and 0.10 mg mL(-1) for M. piperita, 2.16 and 17.13 mg mL(-1) for H. crepitans and 2.03 × 10(-6) and 1.22 × 10(-12) mg mL(-1) for C. guianensis. In the LDT, the LC(50) and LC(90) were respectively: 0.02 and 0.031 mg mL(-1) for P. tuberculatum, 0.002 and 0.04 mg mL(-1) for L. sidoides, 0.018 and 0.03 mg mL(-1) for M. piperita, 0.36 and 0.91 mg mL(-1) for H. crepitans and 17.65 and 1890 mg mL(-1) for C. guianensis. The extract of P. tuberculatum showed the following substances: piperamides as (Z)-piplartine, (E)-piplartine, 8,9-dihydropiplartine, piperine, 10,11-dihydropiperine, 5,6 dihydropiperlongumine and pellitorine. The major compounds of the oils were thymol (76.6%) for L. sidoides, menthol (27.5%) for M. piperita and oleic acid (46.8%) for C. guianensis. Regarding the in vivo test, neither dose of P. tuberculatum caused any significant reduction (P>0.05) in worm burden and fecal egg counts compared with the control group. We conclude that the extracts of P. tuberculatum, L. sidoides and M. piperita have effective activity when tested in vitro, but the doses of the extract of P. tuberculatum have no effect when employed in in vivo tests. 相似文献
998.
Vilela VL Feitosa TF Braga FR de Araújo JV Souto DV Santos HE Silva GL Athayde AC 《Veterinary parasitology》2012,188(1-2):127-133
The aim of this study was to test a pellet formulation in a sodium alginate matrix of Duddingtonia flagrans in the biological control of goat gastrointestinal helminths kept in a native pasture in a semi-arid region of Paraíba state, northeastern Brazil. An area of 2.4 ha was divided into three paddocks, where groups of seven goats ware formed. Each group received the following treatments during the months of March to August 2011: D. flagrans group, received 3g of pellets containing D. flagrans (AC001) for each 10 kg/l.w., twice a week; Moxidectin 0.2% group, received 0.2mg/kg of Moxidectin 0.2% orally, every 30 days; Control group, received 3g of pellets without fungi per 10 kg/l.w., twice a week. Each month, a tracer goat was placed in each group for 30 days and then sacrificed and necropsied. The D. flagrans group showed a greater reduction in EPG, increased weight gain, higher rates of packed cell volume and lower parasitic load burden in the tracer goats compared to Moxidectin 0.2% and Control groups. D. flagrans was efficient in controlling goat gastrointestinal helminthiasis in a semi-arid region of northeastern Brazil. 相似文献
999.
Identification of parasites in Puffinus puffinus (Birds, Procellariiformes) from Northeastern Brazil
Cristiane Maria Fernandes de Melo Jaqueline Bianque de Oliveira Ana Célia Rodrigues Athayde Ant?nio Flávio Medeiros Dantas Thais Ferreira Feitosa Vinícius Longo Ribeiro Vilela Danilo José Ayres de Menezes Paulo Guilherme Carniel Wagner 《Veterinary research communications》2012,36(4):235-238
Studies on the parasitic fauna of migratory sea birds of the Puffinus genus are scarce. Therefore, the aim of this study was to identify parasites of 16 specimens of Puffinus puffinus (Procellariiformes, Procellariidae) that died during the period of June 2011 to December 2011 at the Wildlife Screening Center (CETAS) of the Brazilian Institute of Environment and Natural Resources (IBAMA) in Cabedelo, Paraíba. During necropsy, biting lice and/or gastrointestinal helminths were collected in seven (43.7?%) birds. Lice were collected in five (31.2?%) birds, and the species identified were Halipeurus diversus, Trabeculus aviator, Austromenopon paululum), Saemundssonia sp. and Naubates sp. The prevalence of helminths was also 31.2?%. The nematodes species were Seuratia shipleyi and Contracaecum sp., and cestodes were Tetrabothrius sp. This is the first record in Brazil of Naubates sp., Seuratia shipleyi, Contracaecum sp., and Tetrabothrius sp. in Puffinus puffinus. 相似文献
1000.
de Almeida GF Horsted K Thamsborg SM Kyvsgaard NC Ferreira JF Hermansen JE 《Veterinary parasitology》2012,186(3-4):178-187
This work investigated the preventive effect of Artemisia annua L. dried leaves supplied as a botanical coccidiostat to two broiler genotypes reared in a Danish free-range system in a factorial experiment (two genotypes and ± supplement of dried A. annua leaves). The genotypes White Bresse L40, a pure slow-growing line, and Kosmos 8 Ross, a hybrid genotype with medium growing characteristics, were used. Broilers were raised indoor until 29-days-old and kept free of parasites. Twelve groups of 30 randomly selected broilers were placed in the range forming three replicates for each treatment combination. The paddocks were cultivated with a mix of grass and clover. A separate group of broilers was naturally infected with Eimeria spp. oocysts and five animals nominated as "seeders" were introduced to the above mentioned 12 groups, 10 days after its formation, with each group consisting of 35 animals per plot. This infection strategy was meant to imitate the transmission pathway observed at farm level. Ten individual birds from each of the 12 groups, in total 120 animals of mixed sex, were monitored twice weekly for 30 days for oocysts excretion. PCR of pooled faecal samples, oocyst morphology and localization upon necropsy were used to identify the Eimeria species involved in the infection. In general, broilers from both genotypes in the range coped well with a coccidia infection caused by Eimeria acervulina and Eimeria maxima as no clinical symptoms, or deaths, were reported during the experiment. In general, broilers supplemented with A. annua dried leaves showed a significantly (p<0.05) reduced number of excreted oocysts during the infection with no interaction to genotype. Females generally had a significantly higher shedding of oocysts than males (p<0.05). The overall body weight gain and the daily weight gain when infection was subdued showed a three-way interaction among genotype, sex and treatment - accounted mainly for the fact that Kosmos females responded positively to the Artemisia treatment while Kosmos males responded negatively, and only minor differences were found between sexes for the White Bresse genotype. In conclusion, supply of A. annua dried leaves as a botanical coccidiostat significantly reduced oocyst output in free ranged broilers and thus may form part of a strategy to prevent commercial losses. 相似文献