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   1813篇
  免费   148篇
林业   245篇
农学   84篇
基础科学   14篇
  345篇
综合类   116篇
农作物   79篇
水产渔业   190篇
畜牧兽医   654篇
园艺   46篇
植物保护   188篇
  2024年   3篇
  2023年   23篇
  2022年   39篇
  2021年   69篇
  2020年   57篇
  2019年   52篇
  2018年   115篇
  2017年   101篇
  2016年   92篇
  2015年   57篇
  2014年   64篇
  2013年   120篇
  2012年   144篇
  2011年   132篇
  2010年   70篇
  2009年   78篇
  2008年   119篇
  2007年   121篇
  2006年   93篇
  2005年   84篇
  2004年   73篇
  2003年   72篇
  2002年   59篇
  2001年   34篇
  2000年   15篇
  1999年   9篇
  1998年   6篇
  1997年   4篇
  1996年   8篇
  1995年   12篇
  1994年   7篇
  1993年   3篇
  1992年   3篇
  1991年   3篇
  1990年   1篇
  1989年   2篇
  1988年   2篇
  1987年   2篇
  1985年   1篇
  1984年   2篇
  1982年   1篇
  1981年   1篇
  1980年   1篇
  1978年   1篇
  1975年   1篇
  1972年   2篇
  1971年   1篇
  1968年   1篇
  1963年   1篇
排序方式: 共有1961条查询结果,搜索用时 265 毫秒
31.
Cellular and humoral local responses were investigated following repetitive artificial Oestrus ovis infections in lambs. The presence of larvae induced a huge local recruitment of either leucocytes (T and B lymphocytes, macrophages) or granulocytes (eosinophils, mast cells and globule leucocytes). This cellular response was more pronounced in the ethmoid and sinus (development sites of second and third instar larvae) than in the septum or turbinates where first instar larvae migrate. Infected lambs produced Oestrus ovis specific IgG and IgA antibodies in their mucus. This local humoral response was mainly directed against larval salivary gland antigens and not against larval digestive tract antigens. Compared to the control animals, the sinusal mucosa of infected animals was extremely thickened and the epithelium exhibited hyperplasia, metaplasia and eosinophilic exocytosis. The possible roles of these local immune responses in the regulation of O. ovis larvae populations in sheep are discussed.  相似文献   
32.
The objective of this study was to compare the efficacy of oral ketoconazole and terbinafine for reducing population sizes of Malassezia yeasts on canine skin. Twenty-one Basset Hounds were randomised in three groups of seven according to Malassezia populations. Dogs in the first group were treated by oral administration of ketoconazole (Ketofungol) 200 mg, Janssen-Cilag) at 10 mg x kg-1, every 24 h with food, for 3 weeks. Dogs in the second group were treated by oral administration of terbinafine (Lamisil) 250 mg, Novartis) at 30 mg x kg-1, every 24 h with food, for 3 weeks. The seven remaining dogs were used as controls. Malassezia population sizes were assessed by use of contact plates on four cutaneous sites at days 7, 14 and 21. Both ketoconazole and terbinafine were effective in reducing the baseline levels of Malassezia organisms with no significant difference between the two drugs. In further studies, oral terbinafine should be evaluated for the management of canine cases of Malassezia dermatitis.  相似文献   
33.
1. This study was conducted to determine the effects of heat stress on fearfulness, leucocyte components, oxidative stress and lipid peroxidation in two commercial broiler strains, Cobb (C) and Ross (R). 2. At 36 and 37 d of age birds were exposed to 38 +/- 1 degree C for 3 h. Rectal temperatures, duration of tonic immobility (TI), haematocrit values, proportions of leucocyte components (heterophil, lymphocyte, basophil, eosinophil, monocyte), malondialdehyde (MDA) concentrations and antioxidant enzyme activities (CAT, SOD, GPx) of all the birds were determined, before and after heat treatment. 3. Rectal temperatures increased and haematocrit values decreased in birds exposed to heat stress. Heat stress caused a significant increase in heterophil/lymphocyte and in basophil ratios. 4. Exposing birds to heat stress increased duration of TI, suggesting heat-stressed birds tended to be more fearful. 5. Heat stress resulted in a significant Genotype x Treatment interaction for MDA concentration. CAT, SOD and GPx activities; MDA concentrations in heat-stressed R strain birds were greater than in heat-stressed C strain birds.  相似文献   
34.
35.
An epidemiological survey for Theileria annulata infection was conducted in 12 selected villages around Ankara in Central Anatolia, Turkey, during the period April 1990 to January 1993. During the survey, 198 cattle of 30 local breeds, 84 Holstein-Friesian×local breeds and 84 Holstein-Friesian breed were examined for antibodies to T. annulata and the presence of the vector ticks. Four species of Hyalomma ticks were identified: Hyalomma anatolicum anatolicum, Hyalomma anatolicum excavtum, Hyalomma detritum and Hyalomma marginatum marginatum. Salivary gland staining indicated that infected adult ticks of all four species were present and, therefore, were implicated in the transmission of tropical theileriosis in the field. Generally, the Hyalomma infestation rate was low, with the heaviest infestations occurring on the older animals. Young adults and calves had very low infestation rates. Most ticks seen on cattle were adults, very few nymphs were found. The blood smear and serological examination of the 198 cattle conducted in March, before the start of the first disease season, showed that the prevalence of piroplasmosis was 11.1% (22 out of 198) and the seroprevalence of T. annulata was 10.6% (21 out of 198). Forty-three animals were then excluded from the study because they were seropositive and/or harboured piroplasms. Ninety-two seronegative animals showed piroplasmosis (92 out of 155) and 34 seronegative animals became seropositive for T. annulata (34 out of 155) during the three disease seasons. One animal became clinically ill with tropical theileriosis and required treatment. The incidence of cattle showing piroplasmosis and disease in the total study sample was 50.7% and 0.5% per disease season, respectively. The seroconversion rate of new infection with T. annulata in the total study was 14.3% per animal season. The number of cattle showing piroplasmosis was much greater than the number of seropositive cattle, which may indicate the presence of another species of Theileria. The two different management systems encountered in the study were considered to have influenced the tick infestation levels.  相似文献   
36.
OBJECTIVES: To evaluate the effectiveness of transposition of the sacrotuberous ligament (LST) for the treatment of coxofemoral luxation in the dog. STUDY DESIGN: In vivo experimental study. SAMPLE POPULATION: Ten mixed-breed dogs (weighing 12 to 26 kg). METHODS: After general anesthesia, the LST was exposed and released from the sacrum with a sacral bone fragment. Coxofemoral luxation was created by capsulotomy and transection of the ligament of the head of the femur. Suture was passed through 2 small holes in the bone fragment to guide transposition of the LST through a tunnel drilled through the acetabulum and femoral head and neck. The suture material was pulled tight and an interference screw was placed into the femoral tunnel to lock the sacral bone fragment and LST securely in the tunnel. Butorphanol was administered for pain relief and dogs were allowed unrestricted activity. Coxofemoral radiographs were obtained at 15-day intervals. Two dogs were euthanatized for macroscopic and histopathologic examinations at 3 months. RESULTS: Release of the sacral bone was moderately difficult. The transposed ligament and bone fragment were of an appropriate length and were easily and securely fixed by a interference screw method. Visible severe lameness, during the first 7 to 10 days improved to mild lameness within 10 to 21 days. Gait was subjectively normal after 5 weeks. No radiographic abnormalities were observed at any time point. Grossly, the LST was intact and apparently viable and functional. On histopathology, the space in the bone tunnel was filled with new tissue and a hyaline-like layer surrounded the LST. The sacral bone fragment attached to the LST was united with the femoral bone. CONCLUSIONS: Transposition of the LST reduced and stabilized experimentally induced coxofemoral luxation in 10 dogs. Survival of the LST up to 3 months and its adaptation to transposition suggest that this surgical technique could be considered as a permanent treatment option for hip luxations. Transposition and fixation of the LST was easy, but releasing the sacral edge of the LST was difficult because of its deep location and division of the origin into 2 branches in some dogs. CLINICAL RELEVANCE: Results of this experimental study suggest that the technique may be satisfactorily used in dogs with coxofemoral luxation.  相似文献   
37.
Sixty-three Escherichia coli strains isolated from broilers with respiratory problems were examined for virulence factors, hemolysin synthesis ability, motility, hemagglutination capacity, operon pap presence, colicin production, and serum resistance. The capacity to hemagglutinate guinea pig erythrocytes was found in 53 (84.1%) of the samples, but only 30 (47.6%) agglutinated chicken erythrocytes. D-mannose-sensitive hemagglutination against guinea pig erythrocytes was found in 19 (30.2%) samples and against chicken erythrocytes, in 15 (23.8%) samples, whereas the D-mannose-resistant hemagglutination with guinea pig erythrocytes was found in 34 (54%) samples, and 13 of these (20.6%) showed this characteristic against chicken erythrocytes. Operon pap, P fimbria codifier, was detected in 26 samples in a total of 34 D-mannose-resistant samples. Colicin production was observed in 55 (87.3%) of the strains, and 41.8% presented V colicin production. Of the samples analyzed, 56 (88.9%) presented serum resistance, six (9.5%) were intermediate, and only one (1.6%) was sensitive to the action of the complement. The diversity of virulence profiles detected in the samples in this study explains in part the multifactorial characteristics of avian colibacillosis.  相似文献   
38.
A surgical technique is described for transposition of the sacrotuberous ligament to replace the teres ligament in the treatment of coxofemoral luxation in dogs. Ten dogs with coxofemoral luxation were treated using this technique and all animals regained full limb function within two months of surgery. It is suggested that the technique could be employed in dogs suffering from all types of hip luxations.  相似文献   
39.
40.
Clinical, parasitological and biochemical parameters were evaluated in Corriedale and Crioula Lanada sheep after a single experimental infection with Haemonchus contortus. Ten 4-month-old worm-free lambs, of each breed, were infected with 200 L3 H. contortus per kg live weight and four uninfected animals of each breed were used as controls. Every week, the animals were weighed and blood and faecal samples were collected for measurement of packed cell volume (PCV), total serum protein (TSP) and albumin (ALB), and the number of eggs per gram of faeces (EPG), respectively. Twelve weeks after infection, the animals were slaughtered. The worm burden was determined and samples of the abomasal mucosa were processed for determination of the number of eosinophils, mast cells and globule leukocytes. No significant differences in PCV, TSP, ALB, parasite burden or the cell populations of the abomasal mucosa were observed between breeds, but Crioula lambs had a lower EPG count. The comparison of the infected groups with their respective controls revealed significant alterations in PCV, TSP and ALB in the Corriedale lambs and in PCV, TSP, ALB and the density of eosinophils and mast cells in the Crioula lambs.  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