首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   545篇
  免费   15篇
林业   60篇
农学   8篇
  111篇
综合类   37篇
农作物   3篇
水产渔业   13篇
畜牧兽医   289篇
园艺   18篇
植物保护   21篇
  2024年   1篇
  2023年   5篇
  2022年   5篇
  2021年   9篇
  2020年   11篇
  2019年   17篇
  2018年   16篇
  2017年   9篇
  2016年   12篇
  2015年   14篇
  2014年   22篇
  2013年   33篇
  2012年   36篇
  2011年   44篇
  2010年   22篇
  2009年   30篇
  2008年   37篇
  2007年   49篇
  2006年   35篇
  2005年   33篇
  2004年   31篇
  2003年   26篇
  2002年   16篇
  2001年   8篇
  2000年   8篇
  1999年   2篇
  1998年   4篇
  1996年   1篇
  1995年   5篇
  1994年   1篇
  1993年   1篇
  1992年   2篇
  1991年   2篇
  1990年   2篇
  1989年   4篇
  1988年   4篇
  1986年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有560条查询结果,搜索用时 0 毫秒
31.
ObjectiveTo characterize the cardiorespiratory and electrocardiographic effects of the combined administration of phenylbutazone and romifidine.Study designProspective four-period, four-treatment, blinded, randomized, crossover trial.AnimalsFive, healthy, mixed breed horses.MethodsPrior to treatment administration, a catheter was introduced into the intra-thoracic cranial vena cava via the jugular vein and a subcutaneously located carotid artery was catheterised. All treatments were administered intravenously (IV) and consisted of saline placebo (PLC), phenylbutazone (PBZ, 4.4 mg kg?1) romifidine (ROM, 80 μg kg?1) and a combination of phenylbutazone (4.4 mg kg?1) and romifidine (80 μg kg?1). There was at least a 1 week washout period between treatments. Heart rate (HR), respiratory rate (fR), systolic (SAP), diastolic (DAP) and mean (MAP) arterial pressures and central venous pressure (CVP) were recorded for baseline (prior to drug administration) and at 5 minute intervals thereafter for 30 minutes. Electrocardiographic abnormalities were recorded. Data were analyzed by anova.ResultsFor the cardiovascular variables there were no statistically significant (p > 0.05) differences between horses treated with ROM and PBZ_ROM. Statistically significant (p < 0.05) differences only occurred between treatments with romifidine (ROM and PBZ_ROM) and without romifidine (PLC and PBZ). Within treatments, for ROM, changes over time were statistically significant (p < 0.05) for HR, SAP, DAP, MAP and CVP. For PBZ_ROM, changes over time were statistically significant (p < 0.05) for CVP. Sino-atrial and atrio-ventricular blocks occurred in horses treated with ROM and PBZ_ROM.Conclusions and clinical relevanceThe combined IV administration of phenylbutazone and romifidine had no statistically significant effect on cardiorespiratory variables. These limited data suggest no evidence why both agents should not be included in a preoperative medication protocol for healthy horses but do not exclude the possibility of interactions occurring in a larger population.  相似文献   
32.

Background

Hereditary ataxias with similar phenotypes were reported in the Smooth-Haired Fox Terrier, the Jack Russell Terrier and the Parson Russell Terrier. However, segregation analyses showed differing inheritance modes in these breeds. Recently, molecular genetic studies on the Russell group of terriers found independent mutations in KCNJ10 and CAPN1, each associated with a specific clinical subtype of inherited ataxia. The aim of this study was to clarify whether or not Smooth-Haired Fox Terriers with hereditary ataxia and dogs of other related breeds harbor either of the same mutations. A sub goal was to update the results of KCNJ10 genotyping in Russell group terriers.

Findings

Three Smooth-Haired Fox Terriers with hereditary ataxia and two Toy Fox Terriers with a similar phenotype were all homozygous for the KCNJ10 mutation. The same mutation was also found in a heterozygous state in clinically unaffected Tenterfield Terriers (n = 5) and, in agreement with previous studies, in Jack Russell Terriers, Parson Russell Terriers, and Russell Terriers.

Conclusions

A KCNJ10 mutation, previously associated with an autosomal recessive spinocerebellar ataxia in Jack Russell Terriers, Parson Russell Terriers, and Russell Terriers segregates in at least three more breeds descended from British hunting terriers. Ataxic members of two of these breeds, the Smooth-Haired Fox Terrier and the Toy Fox Terrier, were homozygous for the mutation, strengthening the likelihood that this genetic defect is indeed the causative mutation for the disease known as “hereditary ataxia” in Fox Terriers and “spinocerebellar ataxia with myokymia, seizures or both” in the Russell group of terriers.  相似文献   
33.
Estrogenic plant compounds from the human diet such as the lignan secoisolariciresinol diglucoside (SDG, 1) can exert biological activity in the human body upon ingestion and bioactivation to enterodiol (END, 5) and enterolactone (ENL, 6). Bioavailability of lignans is influenced by the food matrix and gut microbial action, of which the latter is subject to a large interindividual variation. In this study, the fate of the lignan precursor SDG, present in the lignan macromolecule of flax seed ( Linum usitatissimum), was determined during an artificial stomach and small intestinal digestion and during metabolism by two different enterolignan phenotypes in a TWINSHIME environment (TWIN Simulator of the Human Intestinal Microbial Ecosystem). The lignan macromolecule acted as a delivery system of SDG in the large intestine. SDG was only hydrolyzed into secoisolariciresinol (SECO, 2) through microbial action in the ascending colon, after which it was bioactivated into enterolignans from the transverse colon onward. Single demethylation was a first step in the bioactivation, followed by dehydroxylation. Enterolignan phenotypes remained stable throughout the experimental period. The establishment of END and ENL production equilibria reflected the subdominance of ENL-producing bacteria in the gastrointestinal tract.  相似文献   
34.
Variants of NOD2, an intracellular sensor of bacteria-derived muramyl dipeptide (MDP), increase susceptibility to Crohn's disease (CD). These variants are thought to be defective in activation of nuclear factor kappaB (NF-kappaB) and antibacterial defenses, but CD clinical specimens display elevated NF-kappaB activity. To illuminate the pathophysiological function of NOD2, we introduced such a variant to the mouse Nod2 locus. Mutant mice exhibited elevated NF-kappaB activation in response to MDP and more efficient processing and secretion of the cytokine interleukin-1beta (IL-1beta). These effects are linked to increased susceptibility to bacterial-induced intestinal inflammation and identify NOD2 as a positive regulator of NF-kappaB activation and IL-1beta secretion.  相似文献   
35.
Biotrophic pathogens, such as the related maize pathogenic fungi Ustilago maydis and Sporisorium reilianum, establish an intimate relationship with their hosts by secreting protein effectors. Because secreted effectors interacting with plant proteins should rapidly evolve, we identified variable genomic regions by sequencing the genome of S. reilianum and comparing it with the U. maydis genome. We detected 43 regions of low sequence conservation in otherwise well-conserved syntenic genomes. These regions primarily encode secreted effectors and include previously identified virulence clusters. By deletion analysis in U. maydis, we demonstrate a role in virulence for four previously unknown diversity regions. This highlights the power of comparative genomics of closely related species for identification of virulence determinants.  相似文献   
36.
New tools are needed to detect chronic sub-clinical mastitis, especially in automatic milking systems. Haptoglobin and serum amyloid A (SAA) are the two most sensitive bovine acute phase proteins, and their concentrations increase in milk from cows with clinical mastitis and in milk from cows with experimentally induced chronic sub-clinical Staphylococcus aureus mastitis. The aim of this study was to further evaluate the potential for haptoglobin and SAA in milk as indicators of chronic sub-clinical mastitis. Quarter milk samples were collected from 41 cows with a mean composite milk somatic cell count (CSCC) above 300,000 cells/mL during at least two months prior to sampling. Quarter milk samples were also taken from eleven cows with a mean CSCC below 80,000 cells/mL during at least two previous months. These samples were analysed for haptoglobin, SAA, adenosine triphosphate (ATP) activity and bacterial growth. The samples were grouped according to their ATP, haptoglobin and SAA status. ATP+ samples had ATP > 2 x 10(-10) mol/mL, Hp+ and SAA+ samples had detectable levels of haptoglobin (> or = 0.3 mg/L) and SAA (> or = 0.9 mg/L), respectively. In udder quarter samples from healthy cows, 42 out of 44 samples belonged to the ATP-Hp-SAA- group. Among cows with chronic sub-clinical mastitis, the ATP+Hp+SAA+ group contained 66 out of 164 samples while 44 samples belonged to the ATP+Hp-SAA- group. Detectable levels of haptoglobin and SAA were found in 92 and 80 samples, respectively. Growth of udder pathogens was detected in 28 samples and Staphylococcus aureus was the most common bacteria. In conclusion, haptoglobin and SAA concentrations below the detection limit were considered as good indicators of healthy udder quarters. A substantial variation in haptoglobin and SAA concentrations in milk was observed in udder quarters with chronic sub-clinical mastitis.  相似文献   
37.
A modified version of the model Opus was applied to measurements of soil water dynamics and atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) persistence in a Bruntwood silt loam soil (Haplic Andosol, FAO system) in Hamilton, New Zealand. The modified model, Opus2, is briefly described and parameter estimation for the simulations is discussed. Soil water dynamics were more accurately described by applying measured soil hydraulic properties than by estimating them using pedotransfer functions. A parameter sensitivity analysis revealed that degradation was the most relevant process in simulating pesticide behaviour by Opus2. The Arrhenius equation incorporated in Opus2 did not correctly describe the effect of temperature on degradation rates obtained at 10, 20 and 30 degrees C. However, as the Arrhenius coefficient is a very sensitive parameter and soil temperature variation was relatively narrow in the field, the Arrhenius coefficient was approximated from the laboratory study. The simulation results obtained were superior to modelling at constant temperature. Field measured persistence of atrazine in the topsoil was underpredicted using the half-life determined in the laboratory at 10 degrees C. Modelling with a lag phase followed by accelerated degradation by use of a sigmoidal degradation equation in Opus2 significantly improved the modelling results. Nevertheless, degradation processes in the laboratory under controlled conditions did not accurately represent field dissipation, however well the laboratory degradation data could be described by simple kinetic equations. The study indicates the importance of improving field techniques for measuring degradation, and developing laboratory protocols that yield degradation data that are more representative of pesticide dynamics in field soils.  相似文献   
38.
OBJECTIVE: To determine the effects of racing and nontraining on plasma thyroxine (T4), free thyroxine (fT4), thyroid-stimulating hormone (TSH), and thyroglobulin autoantibody (TgAA) concentrations in sled dogs and compare results with reference ranges established for dogs of other breeds. DESIGN: Cross-sectional study. ANIMALS: 122 sled dogs. PROCEDURE: Plasma thyroid hormone concentrations were measured before dogs began and after they finished or were removed from the Iditarod Trail Sled Dog Race in Alaska and approximately 3 months after the race. RESULTS: Concentrations of T4 and fT4 before the race were less than the reference range for nonsled dogs in 26% and 18% of sled dogs, respectively. Immediately after racing, 92% of sled dogs had plasma T4 concentrations less than the reference range. Three months after the race, 25% of sled dogs had plasma T4 concentrations less than the reference range. For T4, fT4, TSH, and TgAA, significant differences were not detected in samples collected before the race versus 3 months later. CONCLUSIONS AND CLINICAL RELEVANCE: Plasma T4, fT4, and TSH concentrations decreased in dogs that complete a long distance sled dog race. Many clinically normal sled dogs have plasma T4 and fT4 values that are lower than the reference range for nonsled dogs. We suggest that the reference ranges for sled dogs are 5.3 to 40.3 nmol/L and 3.0 to 24.0 pmol/L for plasmaT4 and fT4 concentrations, respectively, and 8.0 to 370 mU/L for TSH.  相似文献   
39.
Brain samples of 849 free-ranging ruminants (654 roe deer, 189 red deer and 6 chamois) from Bavaria were examined for TSE. In this respect, detections of PrPres were carried out by ELISA technique (BioRad) and immunohistochemistry using the monoclonal antibody (mAb) L42. Validation experiments of the ELISA technique for the detection of prionprotein from free-ranging ruminants showed that the examination of brains of wild ruminants lead to lower extinctions than that of bovine brain samples. Due to the fact that brain samples of 2 known CWD positive wapitis showed definite positive results, all samples were analysed by this test. There were no indications on the occurrence of TSE in any of the sample. In addition, immunohistochemical investigations of 10% of all samples did not show PrPres. Due to the large number of samples, the prevalence of TSE in Bavaria can be quoted under 0.5% for roe deer and under 1.5% for red deer with a certainty of 95%.  相似文献   
40.
In this study serological investigations were performed to determine the prevalence of pestiviral infections in sheep in one Federal State of Austria, namely Carinthia. 1527 blood samples from sheep in 147 flocks were collected and tested by Enzyme-linked immunosorbent assay and virus-neutralisation tests for antibodies to ruminant pestiviruses. The estimated flock prevalence was 47.6%, the individual prevalence 16.3%. Significant geographical variations in the flock as well in the individual prevalence were found. The highest prevalence in sheep and in sheep flocks was established in the region Spittal/Drau with 25.9% and 69.7%.The individual and the flock prevalence was significantly higher on farms where cattle or sheep from other farms were present than on farms with no cattle (p < 0.017). All Enzyme-linked immunosorbent assay positive sera were tested for Bovine viral diarrhea virus-1 (strain NADL), Bovine viral diarrhea virus-2 (strain 125) and for Border disease virus (strain MOREDUN) by virus neutralisation tests. Seventy out of 249 positive samples revealed the highest titres (> or = two-fold) to Bovine viral diarrhea virus-1 and 25 to Border disease virus. The remaining positive samples did not show clear results because of cross reactions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号