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   299篇
  免费   15篇
林业   30篇
农学   6篇
基础科学   1篇
  27篇
综合类   59篇
农作物   22篇
水产渔业   17篇
畜牧兽医   137篇
园艺   4篇
植物保护   11篇
  2022年   4篇
  2021年   3篇
  2020年   4篇
  2019年   9篇
  2018年   5篇
  2017年   4篇
  2016年   7篇
  2015年   2篇
  2014年   5篇
  2013年   15篇
  2012年   12篇
  2011年   15篇
  2010年   14篇
  2009年   13篇
  2008年   13篇
  2007年   16篇
  2006年   15篇
  2005年   13篇
  2004年   12篇
  2003年   11篇
  2002年   26篇
  2001年   5篇
  2000年   9篇
  1999年   4篇
  1998年   4篇
  1997年   10篇
  1996年   6篇
  1992年   4篇
  1991年   4篇
  1990年   4篇
  1989年   2篇
  1988年   4篇
  1986年   3篇
  1984年   2篇
  1983年   3篇
  1982年   2篇
  1976年   2篇
  1971年   3篇
  1970年   1篇
  1967年   1篇
  1966年   2篇
  1948年   1篇
  1921年   2篇
  1919年   1篇
  1916年   2篇
  1915年   1篇
  1912年   2篇
  1907年   1篇
  1905年   1篇
  1902年   1篇
排序方式: 共有314条查询结果,搜索用时 406 毫秒
81.
A 6-year-old 41.8-kg (92-lb) sexually intact male German Shepherd Dog used as an attack and pursuit dog by the local police department was examined because of general malaise and sudden onset of ataxia. Abnormal findings included a high WBC count, fever, and ongoing weight loss. Physical examination was unrevealing initially, in part because of the aggressive nature of the dog. Following treatment with antibiotics, an abdominal mass was detected during a second physical examination, and was confirmed radiographically. Subsequent ultrasound examination revealed a walled mass of mixed echogenicity, with areas of detectable fluid movement. A laparotomy was performed to remove the mass, which weighed 2.2 kg (4.5 lb). Histologic findings were consistent with botryomycosis, and Staphylococcus intermedius was isolated on bacteriologic culture. Postoperative treatment consisted of intravenous, intra-abdominal, and oral administration of antibiotics. Diagnosis of botryomycosis requires histologic examination and bacteriologic culture of the lesion. Treatment consists of surgical intervention and administration of antimicrobials. Botryomycosis is a poorly understood and rarely reported disease found in many species. A computer search of the literature failed to reveal any previous reports of intra-abdominal botryomycosis in dogs.  相似文献   
82.
The effects of drying conditions, final moisture content, and degree of milling on the texture of cooked rice varieties, as measured by texture profile analysis, were investigated. Instrumentally measured textural properties were not significantly (α = 0.05) affected by drying conditions, with the exception of cohesiveness. Cohesiveness was lower in rice dried at lower temperatures (18°C or ambient) than in that dried at the higher commercial temperatures. Final moisture content and degree of milling significantly (α = 0.05) affected textural property values for adhesiveness, cohesiveness, hardness, and springiness; their effects were interdependent. The effects of deep milling were more pronounced in the rice dried to 15% moisture than that dried to 12%. In general, textural property values for hardness were higher and those for cohesiveness, adhesiveness, and springiness were lower in regular-milled rice dried to 15% moisture than in that dried to 12%. In contrast, hardness values were lower and cohesiveness, adhesiveness, and springiness values were higher in deep-milled rice dried to 15% moisture than in that dried to 12% moisture. Deep milling resulted in rice with lower hardness values and higher cohesiveness, adhesiveness, and springiness values.  相似文献   
83.
A post-tsunami rehabilitation of cage culture along the Andaman Sea coast of Thailand was carried out in five provinces (Ranong, Phang-nga, Krabi, Trang and Satun) from September 2007 to February 2008. Based on the survey conducted, the money compensated subsequently used to buy materials for cage re-construction and cage repair accounted for 28.1% of the total, and to buy seed, feed and chemicals for culture operations, 15.8%. A surprising finding is that 56.1% of compensated money was used for other purposes. The analysis showed that the quality and quantity of equipment, seeds and feeds invested in aquaculture farms were increased in comparison with the pre-recovery period. Importantly, the farm area, growth rate, amount of product and revenue were improved during the post-tsunami rehabilitation period. Additionally, the area and quality of houses, household consumption, household infrastructures, health care and education were also improved. The satisfaction level of cage farmers in regard to the recovery programs was high (weigh average index = 3.88). The results from this study showed that the net economic profit (NEP) achieved was 41,030.49 baht/crop (33.9 baht = 1 US$) for sea bass culture, while NEP for grouper culture was 59,529.98 baht/crop. The result from the present study indicated that the economic value of cage culture farms was profitable. However, the seed shortage, high cost of trash fish, disease outbreak and marketing were among key problems and constraints encountered. In this study, we also found that the knowledge about fish marketing and culture techniques was poor. Therefore, technical, marketing and financial support are required for the future.  相似文献   
84.
Calves persistently infected (PI) with Bovine viral diarrhea virus (BVDV) represent an important source of infection for susceptible cattle. We evaluated vaccine efficacy using calves PI with noncytopathic BVDV2a for the challenge and compared tests to detect BVDV in acutely or transiently infected calves versus PI calves. Vaccination with 2 doses of modified live virus vaccine containing BVDV1a and BVDV2a protected the calves exposed to the PI calves: neither viremia nor nasal shedding occurred. An immunohistochemistry test on formalin-fixed ear notches and an antigen-capture enzyme-linked immunosorbent assay on fresh notches in phosphate-buffered saline did not detect BVDV antigen in any of the acutely or transiently infected calves, whereas both tests had positive results in all the PI calves.  相似文献   
85.
86.
1. Twenty-three lines of chickens, obtained from grandparent stocks of 4 Australian breeding companies, were analysed to determine the incidence of early embryonic mortality attributable to chromosome abnormalities. The lines included 10 layer strains, consisting of 6 White Leghorn, 2 New Hampshire and 2 Australorp lines, and 13 broiler lines. 2. A total of 10,730 eggs was examined after 3 d incubation; of these 9746 (90.8%) were fertile. Abortive embryonic development was observed in 1379 (14.1%) of the fertile eggs. This consisted of 952 (69.0%) dead and dying embryos, including 646 malformed and 427 (31.0%) membranes without embryos. 3. Early embryonic mortality was found to vary from 9.8 to 26.8% (average 16.4%) in broiler lines and from 8.0 to 27.9% (average 11.9%) in layer lines. 4. Among 898 abortive embryos analysed, 112 had abnormal chromosomes consisting of 27 haploids, 38 haploid-euploids, 24 triploids, 16 diploid-polyploids, 4 aneuploids, 2 tetraploids and 1 translocation. 5. In broilers and layers respectively, chromosome abnormalities were responsible for 4.4 to 28.1% (average 11.8%) and 7.4 to 25.0% (average 13.4%) of the early embryonic mortality. 6. The overall frequency of chromosome abnormalities in all fertile eggs varied from 0.7 to 3.7% for the broiler lines and 0.7 to 3.4% for the layer lines.  相似文献   
87.
88.
Repeated ultrasonographic examinations and collections of blood samples and uterine lumenal swabs between seven and 28 days after calving were used to examine the relative effects of bacterial contamination and involution of the uterus on the concentrations of acute phase proteins in the blood of 26 dairy cows. The severity of bacterial contamination, as determined by the total bacterial growth score, was a significant variable for the concentrations of the acute phase proteins alpha1-acid glycoprotein (P < 0.0001), haptoglobin (P < 0.05) and ceruloplasmin (P < 0.0001). In addition, the concentrations of alpha1-acid glycoprotein and ceruloplasmin were increased in the cows from which Escherichia coli (P < 0.0001) and Arcanobacterium pyogenes (P < 0.05), respectively, were isolated from the uterine lumen. Uterine involution, as determined by the decreasing diameter of the previously gravid uterine horn, was associated with a decrease in the concentrations of alpha1-acid glycoprotein (P < 0.005), haptoglobin (P < 0.05) and ceruloplasmin (P < 0.01). However, the response of the acute phase proteins to bacterial contamination was independent of the day on which the samples were collected, indicating that their concentrations were increased by bacterial contamination in addition to the changes associated with uterine involution.  相似文献   
89.
90.
The black‐lip pearl oyster, Pinctada margaritifera, used for round pearl production in Polynesia, is generally cultured using “ear‐hanging” where they are attached to a rope to form “chaplets.” In other countries, pearl oysters are cultured using panel (pocket) nets that are more expensive than chaplets but afford more protection to cultured oysters. Prior research has shown panel nets produce pearls of higher quality and value, potentially generating higher profits. This study used cost–benefit analysis to compare pearl production using chaplet‐based and panel net‐based culture methods. Whole farm data, including gross revenues and annual production costs, fixed and variable, were analyzed. Average production cost per pearl using panel net‐based culture was USD 22.47 and for chaplet‐based culture was USD 21.55. However, use of panel nets saved around 3,430 hr (USD 6,860) of labor a year, offsetting the greater capital investment. A chaplet‐based pearl farm generated USD 65,738 in annual profits compared to USD 88,774 for a panel net‐based farm. Positive cash flow was achieved 1 year earlier (Year 7) for the panel net‐based farm. This is the first economic analysis of different pearl culture methods for P. margaritifera and evidence of profitability will support further development of the black‐lip pearl industry in the Indo‐Pacific region.  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