全文获取类型
收费全文 | 574篇 |
免费 | 15篇 |
国内免费 | 2篇 |
专业分类
林业 | 49篇 |
农学 | 17篇 |
基础科学 | 3篇 |
49篇 | |
综合类 | 42篇 |
农作物 | 18篇 |
水产渔业 | 9篇 |
畜牧兽医 | 372篇 |
园艺 | 7篇 |
植物保护 | 25篇 |
出版年
2022年 | 4篇 |
2021年 | 4篇 |
2019年 | 7篇 |
2018年 | 9篇 |
2017年 | 4篇 |
2016年 | 3篇 |
2015年 | 8篇 |
2014年 | 10篇 |
2013年 | 29篇 |
2012年 | 28篇 |
2011年 | 33篇 |
2010年 | 11篇 |
2009年 | 16篇 |
2008年 | 36篇 |
2007年 | 34篇 |
2006年 | 27篇 |
2005年 | 29篇 |
2004年 | 24篇 |
2003年 | 28篇 |
2002年 | 25篇 |
2001年 | 22篇 |
2000年 | 13篇 |
1999年 | 17篇 |
1998年 | 3篇 |
1997年 | 4篇 |
1994年 | 6篇 |
1992年 | 10篇 |
1991年 | 5篇 |
1990年 | 10篇 |
1989年 | 5篇 |
1988年 | 6篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 3篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 6篇 |
1977年 | 10篇 |
1974年 | 6篇 |
1970年 | 6篇 |
1967年 | 2篇 |
1966年 | 3篇 |
1958年 | 2篇 |
1941年 | 2篇 |
1934年 | 2篇 |
1867年 | 2篇 |
1866年 | 7篇 |
1865年 | 2篇 |
排序方式: 共有591条查询结果,搜索用时 250 毫秒
571.
The goal of the present paper was to establish criteria for the differentiation of thymic lymphoma and haematoma of the ventral neck in cattle. Four cattle with thymic lymphoma and seven with haematoma of the ventral neck underwent physical, haematological, biochemical and ultrasonographic examinations as well as histological evaluation of a biopsy specimen. All of the animals had firm non-painful swellings, which were no warmer than normal and extended from the pharyngeal region to the thoracic inlet. A diagnosis could not be established based on the results of physical examination and palpation of the swellings. Animals with a haematoma had a shorter history of being ill compared to those with thymic lymphoma. In patients with a haematoma, anaemia was present, the heart rate was elevated and the haematocrit was decreased, but not in cattle with thymic lymphoma. A tentative diagnosis was made on the basis of a macroscopic evaluation of the biopsy samples, which were dark red and firm in cattle with a haematoma. All cases of malignant thymic lymphoma were confirmed by histological examination of a biopsy sample. Ultrasonography did not help to differentiate between haematoma and thymic lymphoma. All animals with thymic lymphoma and three of those with a haematoma were euthanased. The four remaining animals with a haematoma were treated successfully. 相似文献
572.
573.
574.
The clinical signs and pathological lesions, consistent with Bovine Progressive Degenerative Myeloencephalopathy (BPDME), are described in a heifer. The animal was an 18-month-old Braunvieh-/Brown Swiss crossbreed with 50% Brown Swiss. Both the sire as well as the dam were related to the bull "B.". The only neurological signs were a posterior ataxia. Mobility and coordination of the front legs were normal. The CK activity of the cerebrospinal fluid was enhanced. There was a moderate to severe degeneration of the white matter consisting of marked axonal degradation and distension and degradation of myelin sheats in all parts of the spinal cord as well as in the medulla oblongata. The lesions were more severe in the descending than in the ascending tracts. 相似文献
575.
576.
Ueli Braun Colin Schwarzwald Stefanie Ohlerth Sandra Frei Monika Hilbe 《Acta veterinaria Scandinavica》2014,56(1):14
Background
Three Brown Swiss cows with abnormal regurgitation because of a perioesophageal disorder are described.Case presentation
The cows were ill and had poor appetite, salivation and regurgitation of poorly-chewed feed. Collection of rumen juice was successful in one cow, and in another, the tube could be advanced to the level of the 7th intercostal space, and in the third, only saliva could be collected. In one cow, oesophagoscopy revealed a discoloured 10-cm mucosal area with fibrin deposits. Thoracic radiographs were normal. The cows were euthanased and examined postmortem. Cow 1 had a large perioesophageal abscess containing feed material at the level of the thoracic inlet, believed to be the result of a healed oesophageal injury. Cow 2 had an abscess between the oesophagus and trachea 25 cm caudal to the epiglottis with the same presumed aetiology as in cow 1. Cow 3 had a mediastinal carcinoma that enclosed and constricted the oesophagus.Conclusions
Abnormal regurgitation in cattle is usually the result of an oesophageal disorder. Causes of oesophageal disorders vary widely and their identification can be difficult. 相似文献577.
Claudia Gittel Ellen Schulz-Kornas Friederike A. Sandbaumhüter Regula Theurillat Ingrid Vervuert M. Paula Larenza Menzies Wolfgang Thormann Christina Braun 《Veterinary anaesthesia and analgesia》2021,48(2):213-222
ObjectiveTo evaluate the pharmacokinetics and selected pharmacodynamic effects of a commercially available l-methadone/fenpipramide combination administered to isoflurane anaesthetized ponies.Study designProspective single-group interventional study.AnimalsA group of six healthy adult research ponies (four mares, two geldings).MethodsPonies were sedated with intravenous (IV) detomidine (0.02 mg kg–1) and butorphanol (0.01 mg kg–1) for an unrelated study. Additional IV detomidine (0.004 mg kg–1) was administered 85 minutes later, followed by induction of anaesthesia using IV diazepam (0.05 mg kg–1) and ketamine (2.2 mg kg–1). Anaesthesia was maintained with isoflurane in oxygen. Baseline readings were taken after 15 minutes of stable isoflurane anaesthesia. l-Methadone (0.25 mg kg–1) with fenpipramide (0.0125 mg kg–1) was then administered IV. Selected cardiorespiratory variables were recorded every 10 minutes and compared to baseline using the Wilcoxon signed-rank test. Adverse events were recorded. Arterial plasma samples for analysis of plasma concentrations and pharmacokinetics of l-methadone were collected throughout anaesthesia at predetermined time points. Data are shown as mean ± standard deviation or median and interquartile range (p < 0.05).ResultsPlasma concentrations of l-methadone showed a rapid initial distribution phase followed by a slower elimination phase which is best described with a two-compartment model. The terminal half-life was 44.3 ± 18.0 minutes, volume of distribution 0.43 ± 0.12 L kg–1 and plasma clearance 7.77 ± 1.98 mL minute–1 kg–1. Mean arterial blood pressure increased from 85 (±16) at baseline to 100 (±26) 10 minutes after l-methadone/fenpipramide administration (p = 0.031). Heart rate remained constant. In two ponies fasciculations occurred at different time points after l-methadone administration.Conclusions and clinical relevanceAdministration of a l-methadone/fenpipramide combination to isoflurane anaesthetized ponies led to a transient increase in blood pressure without concurrent increases in heart rate. Pharmacokinetics of l-methadone were similar to those reported for conscious horses administered racemic methadone. 相似文献
578.
Joao H.N. Soares Christina Braun Marcela L. Machado Renato L. Oliveira Natalia Henao-Guerrero Sherryl Countermash-Ott Irving C. Allen David C. Grant Antonio Giannella-Neto 《Veterinary anaesthesia and analgesia》2021,48(3):324-333
ObjectivesTo compare pulmonary gas exchange, tissue oxygenation and cardiovascular effects of four levels of end-expiratory pressure: no positive end-expiratory pressure (ZEEP), positive end-expiratory pressure (PEEP) of maximal respiratory system compliance (PEEPmaxCrs), PEEPmaxCrs + 2 cmH2O (PEEPmaxCrs+2), PEEPmaxCrs + 4 cmH2O (PEEPmaxCrs+4), in isoflurane-anesthetized dogs.Study designProspective randomized crossover study.AnimalsA total of seven healthy male Beagle dogs, aged 1 year and weighing 10.2 ± 0.7 kg (mean ± standard deviation).MethodsThe dogs were administered acepromazine and anesthesia was induced with propofol and maintained with isoflurane. Ventilation was controlled for 4 hours with ZEEP, PEEPmaxCrs, PEEPmaxCrs+2 or PEEPmaxCrs+4. Cardiovascular, pulmonary gas exchange and tissue oxygenation data were evaluated at 5, 60, 120, 180 and 240 minutes of ventilation and compared using a mixed-model anova followed by Bonferroni test. p < 0.05 was considered significant.ResultsCardiac index (CI) and mean arterial pressure (MAP) were lower in all PEEP treatments at 5 minutes when compared with ZEEP. CI persisted lower throughout the 4 hours only in PEEPmaxCrs+4 with the lowest CI at 5 minutes (2.15 ± 0.70 versus 3.45 ± 0.94 L minute–1 m–2). At 180 and 240 minutes, MAP was lower in PEEPmaxCrs+4 than in PEEPmaxCrs, with the lowest value at 180 minutes (58 ± 7 versus 67 ± 7 mmHg). Oxygen delivery index (DO2I) was lower in PEEPmaxCrs+4 than in ZEEP at 5, 60, 120 and 180 minutes. Venous admixture was not different among treatments.Conclusion and clinical relevanceThe use of PEEP caused a transient decrease in MAP and CI in lung-healthy dogs anesthetized with isoflurane, which improved after 60 minutes of ventilation in all levels of PEEP except PEEPmaxCrs+4. A clinically significant improvement in arterial oxygenation and DO2I was not observed with PEEPmaxCrs and PEEPmaxCrs+2 in comparison with ZEEP, whereas PEEPmaxCrs+4 decreased DO2I. 相似文献
579.
Although many sequences and linear IgE epitopes of allergenic proteins have been identified and archived in databases, structural and physicochemical discriminators that define their specific properties are lacking. Current bioinformatics tools for predicting the potential allergenicity of a novel protein use methods that were not designed to compare peptides. Novel tools to determine the quantitative sequence and three-dimensional (3D) relationships between IgE epitopes of major allergens from peanut and other foods have been implemented in the Structural Database of Allergenic Proteins (SDAP; http://fermi.utmb.edu/SDAP/). These peptide comparison tools are based on five-dimensional physicochemical property (PCP) vectors. Sequences from SDAP proteins similar in their physicochemical properties to known epitopes of Ara h 1 and Ara h 2 were identified by calculating property distance (PD) values. A 3D model of Ara h 1 was generated to visualize the 3D structure and surface exposure of the epitope regions and peptides with a low PD value to them. Many sequences similar to the known epitopes were identified in related nut allergens, and others were within the sequences of Ara h 1 and Ara h 2. Some of the sequences with low PD values correspond to other known epitopes. Regions with low PD values to one another in Ara h 1 had similar predicted structure, on opposite sides of the internal dimer axis. The PD scale detected epitope pairs that are similar in structure and/or reactivity with patient IgE. The high immunogenicity and IgE reactivity of peanut allergen proteins might be due to the proteins' arrays of similar antigenic regions on opposite sides of a single protein structure. 相似文献
580.