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   446篇
  免费   29篇
林业   31篇
农学   22篇
  129篇
综合类   19篇
农作物   24篇
水产渔业   11篇
畜牧兽医   192篇
园艺   11篇
植物保护   36篇
  2023年   2篇
  2022年   2篇
  2021年   18篇
  2020年   22篇
  2019年   15篇
  2018年   14篇
  2017年   22篇
  2016年   23篇
  2015年   24篇
  2014年   21篇
  2013年   41篇
  2012年   43篇
  2011年   28篇
  2010年   25篇
  2009年   15篇
  2008年   31篇
  2007年   24篇
  2006年   21篇
  2005年   17篇
  2004年   12篇
  2003年   10篇
  2002年   13篇
  2001年   4篇
  2000年   5篇
  1999年   3篇
  1998年   1篇
  1997年   1篇
  1995年   4篇
  1994年   2篇
  1993年   2篇
  1992年   2篇
  1991年   3篇
  1988年   1篇
  1986年   1篇
  1983年   1篇
  1982年   1篇
  1980年   1篇
排序方式: 共有475条查询结果,搜索用时 234 毫秒
101.
Composts are considered to be one of the best soil amendments. However, the effects of composts with added polymeric materials on soil physical,hydraulic, and micromorphological properties have not been widely discussed. Changes in soil physical properties influence the numerous services that soils provide. We studied the impacts of composts with the addition of three different polymers(F1–F3) produced from polyethylene and thermoplastic corn starch on the physical, hydraulic, and micromorphological properties of two soils, a Cambic Phaeozem and a Luvic Phaeozem. Applying composts with polymers had limited or no significant effect on soil bulk density and porosity, but increased the field water capacity by 18%–82% and 3%–6% and the plant-available water content by 15%–23% and 4%–17% for the Cambic Phaeozem and Luvic Phaeozem, respectively. The application of composts with polymers had a greater effect on the Cambic Phaeozem than on the Luvic Phaeozem. It was suggested that the use of modified composts led to changes in soil physical properties and micromorphological features and this effect was dependent on the compost application rate. Composts made with the addition of composite synthetic and natural material-derived polymers during composting were found to be a composite mixture that can be successfully used in agriculture.  相似文献   
102.
Primers for the PCR amplification of homologous genes encoding polyketide coronafacic acid and coronafacic ligase in the cells of Pectobacterium atrosepticum SCRI1043 (BX950851) were developed to study the presence of these genes in the genome of Pectobacterium sp. and Dickeya sp. Coronafacic ligase catalyses the formation of coronatine from polyketide coronafacic acid and coronamic acid. Coronatine is a toxin produced by Pseudomonas syringae and is one of the major virulence factors in this bacterium. This study using several strains of P. atrosepticum, P. carotovorum subsp. carotovorum and Dickeya sp. isolated in different countries, indicated that all strains of P. atrosepticum possess genes coding coronafacic acid (cfa gene cluster) and coronafacic ligase (cfl). However, these genes were present only in the genome of five out of 50 tested P. carotovorum subsp. carotovorum strains and two out of 34 strains of Dickeya sp. tested. The PCR products homologous to the sequence of cfa7 and cfl gene fragments were sequenced in order to check the level of homology between genes of P. atrosepticum, P. carotovorum subsp. carotovorum and Dickeya sp. The sequences of the gene fragments amplified from all P. atrosepticum strains were almost identical (100% and 99.97%, respectively). The homology of the sequences obtained for P. atrosepticum and sequences of five P. carotovorum subsp. carotovorum and two Dickeya sp. was lower, between 89.69% to 95.00% for the cfl gene fragment, and about 94% for the cfa7 gene fragment.  相似文献   
103.
A 5-year old, neutered, male, domestic sable ferret presented 24 hours after escaping outside and sustaining unknown trauma. Physical examination findings included tachycardia, tachypnea, and hind limb paresis in a laterally recumbent patient. Radiographs, laboratory evaluation, and abdominocentesis revealed the presence of hemoperitoneum, blunt hepatic trauma, pneumothorax, and a small abdominal hernia. The ferret was treated with resuscitative fluids, thoracocentesis, abdominal counterpressure, and blood transfusion. This is the first case report of multi-systemic trauma in a ferret. The ferret made a complete recovery and was discharged to the referring veterinarian three days after presentation. (Vet. Emerg. Crit. Care, 10:13–18, 2000)  相似文献   
104.
105.
A Lesser Malayan mousedeer (Tragulus javanicus), persistently infected with noncytopathogenic bovine viral diarrhea virus (BVDV) type 1f, was experimentally superinfected with a cytopathogenic isolate of BVDV type 1c, which antigenically partially matched the endogenous strain. Within the observational period of 125 days after superinfection, the animal did not demonstrate any clinical signs of the disease and/or significant changes in blood values. Neutralizing antibodies were detected at 35 and 42 days postinfection. The isolate causing the superinfection was found in feces, nasal swabs, and saliva starting from day 29 and at various times postchallenge. Macroscopic or histologic examination did not reveal mucosal disease-like lesions, despite the detection of the cytopathogenic isolate in the salivary gland, rumen, abomasum, kidney, and superficial prescapular lymph node. Results indicate that the cytopathogenic BVDV strain, which was used in the superinfection, persisted in the viremic animal without causing disease within the observation period.  相似文献   
106.
The clinical, neuropathologic, and magnetic resonance (MR) imaging features in four cats with necrosis of the hippocampus and piriform lobe are described. All cats had acute generalized seizures and behavioral changes including aggression, salivation, polyphagia, and disorientation. Routine hematologic, serum chemistry, and cerebrospinal fluid analyses were normal. MR imaging abnormalities were restricted to the area of the hippocampus and piriform lobe. The lesions were T2-hyperintense, T1-hypointense, and were characterized by various degrees of contrast enhancement. Lesions were consistent with necrotizing encephalitis. Two cats were euthanized and underwent postmortem examination within a week after MR imaging due to the lack of response to antiepileptic drug therapy and progressive neuropathy. The remaining two cats lived for about four months and were then euthanized because of persistent behavioral and neurologic signs; only one of these cats underwent postmortem examination with histopathologic examination. Histopathological findings were typical of severe, diffuse, bilateral symmetric necrosis, and degeneration of neurons in the hippocampus and piriform lobe, but an etiologic agent was not apparent. This apparently unique feline syndrome, now reported in Switzerland and Italy, has no known cause at this time.  相似文献   
107.
The aim of the study was to evaluate the influence of inulin supply to high‐fat diet rich in saturated fatty acids (SFA) on pork quality and profile of sarcoplasmic protein in drip loss. At 50 days of age, twenty cross‐bred pigs (gilts) were randomly allotted to four groups: the control (C) group fed a standard diet, and three experimental (D1, D2 and D3) groups fed a high‐fat diet rich in SFA. Moreover, pigs from the groups D2 and D3 consumed an extra inulin supply (7% of daily feed intake) from 85 to 120 days of age (for 5 weeks) and from 50 to 120 days of age (for 10 weeks) respectively. The addition of inulin to the diet reduced meaty odour and flavour significantly, improved tenderness and overall sensory quality of pork and additionally influenced ultimate pH, L* colour parameter, lactate level and protein content in meat. The diets also affected the profile of sarcoplasmic proteins. Significant effects were observed for the following enzymes—PK/PGI (pyruvate kinase/phosphoglucose isomerase) and ALD (aldolase), which are related to the intensity of post‐mortem glycolysis. Presented data indicate that long‐term inulin supply to high‐fat diet has a positive effect on technological and sensory quality as well as protein profile of pork.  相似文献   
108.
109.
Exposure to mercuric chloride (HgCl2; 5 mg kg?1 body weight; i.p.) induced oxidative stress in mice and substantially increased lipid peroxidation (LPO) and oxidized glutathione (GSSG) levels, decreased the level of reduced glutathione (GSH) and various antioxidant enzymes in liver and also increased the activities of liver marker enzymes in serum. Therapy with propolis extract, a resinous wax‐like beehive product (200 mg kg?1 orally, after mercury administration), for 3 days inhibited LPO and the formation of GSSG and increased the level of GSH in the liver. Release of serum transaminases, alkaline phosphatase, lactate dehydrogenase and γ‐glutamyl transpeptidase were significantly restored after propolis treatment. The activities of antioxidant enzymes, that is, superoxide dismutase, catalase, glutathione‐S‐transferase and glucose‐6‐phosphate dehydrogenase, were also concomitantly restored towards normal levels after propolis administration. These observations clearly demonstrate that propolis treatment augments antioxidant defense against mercury‐induced toxicity and provide evidence that propolis has therapeutic potential as a hepatoprotective agent.  相似文献   
110.
A case of diffuse leptomeningeal oligodendrogliomatosis affecting the brain and spinal cord of a dog is presented. A 7.5‐year old, male neutered Staffordshire bull terrier presented for evaluation of a chronic history of tetraparesis and seizures, with a multifocal neuroanatomical localization was determined. Extra‐axial intradural lesions with an atypical presentation of a dural tail sign were seen on MRI. Histologically, the lesions were consistent with leptomeningeal oligodendrogliomatosis. To the authors’ knowledge, a dural tail sign has not previously been reported as an MRI characteristic of diffuse leptomeningeal oligodendrogliomatosis in dogs.  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