全文获取类型
收费全文 | 668篇 |
免费 | 55篇 |
国内免费 | 1篇 |
专业分类
林业 | 88篇 |
农学 | 33篇 |
基础科学 | 4篇 |
126篇 | |
综合类 | 42篇 |
农作物 | 38篇 |
水产渔业 | 86篇 |
畜牧兽医 | 190篇 |
园艺 | 20篇 |
植物保护 | 97篇 |
出版年
2024年 | 1篇 |
2023年 | 12篇 |
2022年 | 15篇 |
2021年 | 43篇 |
2020年 | 37篇 |
2019年 | 30篇 |
2018年 | 34篇 |
2017年 | 32篇 |
2016年 | 38篇 |
2015年 | 31篇 |
2014年 | 32篇 |
2013年 | 41篇 |
2012年 | 48篇 |
2011年 | 64篇 |
2010年 | 27篇 |
2009年 | 30篇 |
2008年 | 41篇 |
2007年 | 25篇 |
2006年 | 26篇 |
2005年 | 28篇 |
2004年 | 20篇 |
2003年 | 24篇 |
2002年 | 23篇 |
2001年 | 3篇 |
2000年 | 5篇 |
1999年 | 4篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1990年 | 1篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1975年 | 1篇 |
排序方式: 共有724条查询结果,搜索用时 15 毫秒
71.
The median effective dosage (ED50) of propofol for induction of anesthesia was determined in 25 dogs premedicated with acepromazine, 0.05 mg/kg of body weight, and in 35 unpremedicated dogs. The ED50 was found to be 2.2 mg/kg in premedicated dogs and was 3.8 mg/kg in unpremedicated dogs. The mean +/- SD total dosage of propofol required to induce anesthesia in premedicated animals was 2.8 +/- 0.5 mg/kg and was 4.7 +/- 1.3 mg/kg in unpremedicated animals. Signs of excitement were observed in 5 of the unpremedicated dogs, but in none of those that were premedicated. 相似文献
72.
Terrell SP Sundeep Chandra AM Pablo LS Lewis DD 《Journal of the American Animal Hospital Association》2004,40(4):345-348
A 3-year-old, German shepherd dog died suddenly during cemented total hip arthroplasty. Gross necropsy findings included severe pulmonary edema and congestion as well as congestion of the liver and kidneys. Acute pulmonary embolism was suspected as the cause of death. Microscopic examination of hematoxylin and eosin-stained, formalin-fixed, and oil red O-stained frozen tissue sections confirmed the presence of large numbers of fat globules in blood vessels in the lungs, liver, and kidneys. Fat embolism during total hip arthroplasty is a common surgical complication in humans, but it is uncommon in veterinary cases and is rarely a cause of death. 相似文献
73.
Addie DD Kennedy LJ Ryvar R Willoughby K Gaskell RM Ollier WE Nart P Radford AD 《Journal of Feline Medicine and Surgery》2004,6(2):59-62
There are four outcomes to feline coronavirus (FCoV) infection: the development of feline infectious peritonitis (FIP, which is immune-mediated), subclinical infection, development of healthy lifelong carriers and a small minority of cats who resist infection (Addie and Jarrett, Veterinary Record 148 (2001) 649). Examination of the FCoV genome has shown that the same strain of virus can produce different clinical manifestations, suggesting that host genetic factors may also play a role in the outcome of infection. FIP is most prevalent amongst pedigree cats, although how much of this is due to them living in large groups (leading to higher virus challenge and stress which predisposes to FIP) and how much is due to genetic susceptibility is not known. If host genetics could be shown to play a role in disease, it may allow the detection of cats with a susceptibility to FIP and the development of increased population resistance through selective breeding. The feline leucocyte antigen (FLA) complex contains many genes that are central to the control of the immune response. In this preliminary study, we used clonal sequence analysis or reference strand conformational analysis (RSCA) to analyse the class II FLA-DRB of 25 cats for which the outcome of FCoV exposure was known. Individual cats were shown to have between two and six FLA-DRB alleles. There was no statistically significant association between the number of alleles and the outcome of FCoV infection. No particular allele appeared to be associated with either the development of FIP, resistance to FCoV, or the carrier status. However, the analysis was complicated by apparent breed variation in FLA-DRB and the small number of individuals in this study. 相似文献
74.
Guchu E Díaz-Maroto MC Díaz-Maroto IJ Vila-Lameiro P Pérez-Coello MS 《Journal of agricultural and food chemistry》2006,54(8):3062-3066
The influence of the species and geographical origin on the volatile composition of wood samples from 80 Spanish oaks (55 Quercus petraea Liebl. and 25 Quercus robur L.) has been studied. Oak volatile components were isolated by simultaneous distillation-extraction and analyzed by gas chromatography-mass spectrometry. cis- and trans-beta-methyl-gamma-octalactones were the main constituents, the cis stereoisomer being predominant. Other important volatile components were furfural, 5-methylfurfural, guaiacol, eugenol, vanillin, or syringaldehyde. The main differences were established between species, Quercus petraea being significantly richer in volatile compounds than Quercus robur; however, the variability found among trees was high. Differences among geographical provenances were much less important than those found between species. 相似文献
75.
Martínez J Segura P García D Aduriz G Ibabe JC Peris B Corpa JM 《Veterinary journal (London, England : 1997)》2006,172(2):382-385
A seven-year-old female Indian python (Python molurus) weighing about 35kg was euthanased after several clinical episodes of stomatitis, pneumonia, ophthalmitis and dystocia over a period of four years. The animal had been maintained in a terrarium in a circus truck at an adequate temperature. During shows, however, the snake was considered to be exposed to stressful conditions for several hours at a time at low temperatures and with noise and bright lights. A post-mortem examination indicated ulcerative stomatitis, osteomyelitis, severe pneumonia and numerous granulomata and multifocal necrosis in stomach and spleen. Corynebacterium macginleyi was isolated in pure culture from the ulcerative stomatitis, and mixed with Stenotrophomonas maltophilia from the lungs and spleen. The findings indicated that the snake had died from a septicaemic process caused by C. macginleyi, probably originating from the stomatitis. The role of S. maltophilia as a secondary agent is discussed. The stress of the circus show and poor husbandry may have predisposed the animal to infection and septicaemia. This is the first report of C. macginleyi causing disease in a snake. 相似文献
76.
77.
Carlos Gutiérrez-Gutiérrez Carolina Cantalapiedra-Navarrete Wilfrida Decraemer Nicola Vovlas Tom Prior Juan E. Palomares Rius Pablo Castillo 《European journal of plant pathology / European Foundation for Plant Pathology》2012,134(3):561-597
During nematode surveys in southern Spain and Italy 14 populations of Xiphinema species tentatively identified as Xiphinema americanum-group were detected. Morphological and morphometrical studies identified three new species and six known Xiphinema americanum-group species, viz.: Xiphinema parabrevicolle n. sp., Xiphinema parapachydermum n. sp., Xiphinema paratenuicutis n. sp., Xiphinema duriense, Xiphinema incertum, Xiphinema opisthohysterum, Xiphinema pachtaicum, Xiphinema rivesi, and Xiphinema santos. The Xiphinema americanum-group is the most difficult Xiphinema species group for diagnosis since the morphology is very conservative and morphometric characters often overlap. This group includes vectors of several important plant pathogenic viruses that cause significant damage to a wide range of agricultural crops. Molecular characterisation of these species using D2-D3 expansion regions of 28S rRNA, 18S rRNA, ITS1-rRNA and the protein-coding mitochondrial gene, cytochrome oxidase c subunit 1 was carried out and maximum likelihood and Bayesian inference analysis were used to reconstruct phylogenetic relationships among these species and with other Xiphinema americanum-group species. 相似文献
78.
Phenological and water-use patterns underlying maximum growing season length at the highest elevations: implications under climate change 总被引:1,自引:0,他引:1
Consequences of climate change on tree phenology are readily observable, but little is known about the variations in phenological sensitivity to drought between populations within a species. In this study, we compare the phenological sensitivity to temperature and water availability in Abies pinsapo Boiss., a drought-sensitive Mediterranean fir, across its altitudinal distribution gradient. Twig growth and needle fall were related to temperature, precipitation and plant water status on a daily scale. Stands located at the top edge of the distributional range showed the most favourable water balance, maximum growth rates and little summer defoliation. Towards higher elevations, the observed delay in budburst date due to lower spring temperatures was overcome by a stronger delay in growth cessation date due to the later onset of strong water-deficit conditions in the summer. This explains an extended growing season and the greatest mean growth at the highest elevation. Conversely, lower predawn xylem water potentials and early partial stomatal closure and growth cessation were found in low-elevation A. pinsapo trees. An earlier and higher summer peak of A. pinsapo litterfall was also observed at these water-limited sites. Our results illustrate the ecophysiological background of the ongoing altitudinal shifts reported for this relict tree species under current climatic conditions. 相似文献
79.
Although some ELISA tests using cytoplasmic or outer membrane antigens of Brucella have been developed to improve the diagnosis of canine brucellosis, the performance of these assays has not been compared. In the present study three ELISA tests using lipopolysaccharide (LPS)-free cytoplasmic proteins (CPs) of Brucella abortus, the lumazine synthase (LS) of Brucella spp. or a hot-saline (HS) extract of Brucella canis containing outer membrane antigens were used to test sera from dogs with suspected or confirmed brucellosis (n=36) and from dogs with pathological conditions other than brucellosis (n=212). In the first group the proportion of positive results was 92, 92 and 81% for the ELISAs with HS, CP and LS, respectively, and 94% of the samples were positive by at least one ELISA test. Three dogs that were negative by agglutination (2ME-RSAT) had a positive result by at least one ELISA, and this discrepancy was attributed to the lower analytical sensitivity of agglutination tests. This hypothesis was confirmed by a serological follow-up of seven dogs recently infected with B. canis in three of which the illness was diagnosed earlier by one or more ELISA tests than by 2ME-RSAT. Among dogs having pathological conditions other than brucellosis, specificities were 94.3, 96.7 and 96.7% for the ELISAs with HS, CP and LS, respectively. This study shows that HS-ELISA and CP-ELISA are highly specific and sensitive for the diagnosis of canine brucellosis and can detect the infection by B. canis shortly after the exposure to the pathogen. 相似文献
80.
Gilberto Solano-Surez Luciano S Caixeta Alexander Masic Diego Manríquez Luciana Hatamoto-Zervoudakis Sushil Paudyal Ana Velasquez-Munoz Juan Velez Pablo J Pinedo 《Journal of animal science》2021,99(9)
The main objective of this study was to evaluate the effect of peripartal administration of a commercially available nonspecific immune stimulant (mycobacterium cell wall fraction; MCWF [Amplimune, NovaVive Inc., Napanee, ON, Canada]) on the incidence of disease during early lactation and subsequent fertility of dairy cows. A second objective was to characterize the dynamics of circulating white blood cells (WBC) and metabolic markers following treatment administration. Cows in an United States Department of Agriculture (USDA) organic-certified dairy herd were blocked by parity and, based on sequential calving dates, randomly assigned to receive two injections (5 mL s.c.) of either a placebo (saline solution) as a control (CON; n = 71) or MCWF (n = 65) at enrollment (7 d before expected calving) and within 24 h after calving. Blood samples were collected from a subsample of the study population (MCWF = 16; CON = 18) for WBC count at enrollment, at day 2 post enrollment, and at days 1, 3, 7, and 14 after calving. Serum fatty acids, beta-hydroxybutyrate, and Ca concentrations were determined at days 1 and 7 postpartum (MCWF = 21; CON = 21). Main outcome variables included incidence risk of peripartal and early lactation health disorders and pregnancy at first artificial insemination (AI), at 100, and at 150 days in milk (DIM). In addition, the average daily milk yield up to 90 DIM and death and live culling before 305 DIM were compared. Treatment effects were assessed using multivariable logistic regression, time-to-event analyses, and repeated measures analysis of variance (ANOVA). A treatment effect on the incidence risk of some of the health disorders in the study was established. Incidence risk of metritis and clinical mastitis <28 DIM was smaller in MCWF than in CON cows (36.9% vs. 50.7% and 6.3% vs. 19.7%, respectively). On the contrary, the incidence risk of respiratory disease <28 DIM was smaller in CON (0%) than in MCWF (7.7%). Reproductive performance of multiparous cows was affected by MCWF administration: pregnancy at first AI and pregnancy at 100 and 150 DIM were greater in MCWF than in CON (35.6% vs. 19.2%; 51.1% vs. 25.0%; and 64.4% vs. 40.4%, respectively). Overall, median intervals from calving to pregnancy were 90 vs. 121 d in MCWF and CON cows, respectively. No treatment effects on the dynamics of circulating WBC or in postpartum metabolic status were established. No differences for milk yield or for the proportion of cows that survived up to 305 DIM were determined, although cows in MCWF left the herd earlier than cows in CON. In conclusion, incidence risks of metritis and mastitis in early lactation were smaller in cows receiving MCWF, whereas the incidence risk of respiratory disease was smaller in CON. Fertility significantly improved in MCWF compared with CON cows. As this study was performed in an organic-certified dairy, specific health and reproductive management practices may affect the external validity of the current findings. 相似文献