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   160篇
  免费   5篇
林业   4篇
农学   5篇
基础科学   1篇
  8篇
综合类   8篇
农作物   79篇
水产渔业   2篇
畜牧兽医   57篇
植物保护   1篇
  2017年   3篇
  2016年   2篇
  2014年   2篇
  2013年   7篇
  2012年   3篇
  2011年   2篇
  2009年   5篇
  2008年   4篇
  2007年   3篇
  2006年   2篇
  2005年   3篇
  2004年   2篇
  2003年   2篇
  2002年   3篇
  1999年   4篇
  1998年   7篇
  1997年   4篇
  1996年   6篇
  1995年   4篇
  1993年   5篇
  1992年   4篇
  1989年   2篇
  1988年   5篇
  1986年   3篇
  1981年   4篇
  1977年   3篇
  1973年   1篇
  1970年   2篇
  1969年   1篇
  1967年   2篇
  1966年   1篇
  1965年   1篇
  1963年   2篇
  1962年   3篇
  1959年   2篇
  1957年   1篇
  1947年   2篇
  1946年   1篇
  1944年   2篇
  1943年   13篇
  1941年   5篇
  1940年   2篇
  1939年   3篇
  1937年   3篇
  1936年   5篇
  1935年   5篇
  1934年   2篇
  1933年   1篇
  1930年   1篇
  1926年   1篇
排序方式: 共有165条查询结果,搜索用时 31 毫秒
51.
52.
53.
An interspecific hybrid ofS. phureja x USW1, a haploid of Katahdin, produced acceptable potato chips when processed directly from 40 F (4.5 C) storage during 3 years of testing. It was crossed with 11 interspecific hybrids. Tubers from these progenies were stored for 5 weeks at 40 F and then chipped immediately for 55 seconds in vegetable oil maintained at 375 F (190 C). Of 645 seedlings tested, chip color was acceptable in 17 and variable in 18. A group of 600 seedlings fromS. tuberosum parents treated comparably produced black-colored chips without exception.  相似文献   
54.
A new coaxial line cell for the determination of dielectric spectra of undisturbed soil samples was developed based on a 1.625‐inch ‐ 50 Ω coaxial system. Undisturbed soil samples were collected from a soil profile of the Taunus region (Germany) and capillary saturated followed by a step‐by‐step de‐watering in a pressure plate apparatus as well as oven‐drying at 40°C. The resultant water contents of the soil samples varied from saturation to air‐dry. Permittivity measurements were performed within a frequency range from 1 MHz to 10 GHz with a vector network analyser technique. Complex effective relative permittivity or electrical conductivity was obtained by combining quasi‐analytical and numerical inversion algorithms as well as the parameterizing of measured full set S‐parameters simultaneously under consideration of a generalized fractional dielectric relaxation model (GDR). The measurement of standard materials shows that the technique provides reliable dielectric spectra up to a restricted upper frequency of 5 GHz. For the soil samples investigated, the real part of complex effective relative permittivity ?r,eff and the real part of complex effective electrical conductivity σeff decreased with increasing matric potential or decreasing water contents. Soil texture and porosity affect the dielectric behaviour at frequencies below 1 GHz. For frequencies above 1 GHz minor texture effects were found. The presence of organic matter decreases ?r,eff and σeff. At 1 GHz, the empirical model of Topp et al. (1980) is in close agreement with the experimentally determined real part of the effective permittivity with RMSEs ranging from 1.21 for the basal periglacial slope deposit and 1.29 for bedrock to 3.93 for the upper periglacial slope deposit (Ah). The comparison of the experimental results with a semi‐empirical dielectric mixing model shows that data, especially for the organic‐free soils, tend to be under‐estimated below 1 GHz. The main advantage of the new method compared with conventional impedance and coaxial methods is the preservation of the natural in‐situ structure and properties such as bulk density of the investigated soil samples.  相似文献   
55.
OBJECTIVE: To compare molecular typing methods for the differentiation of Salmonella enterica serovar Enteritidis phage type (PT) 4 isolates that allowed for the determination of their genetic relatedness. SAMPLE POPULATION: 27 Salmonella Enteritidis PT 4 strains isolated in the United States and Europe. PROCEDURE: Several molecular typing methods were performed to assess their ability to genetically differentiate among Salmonella Enteritidis PT 4 isolates. Results of pulse-field gel electrophoresis (PFGE), repetitive polymerase chain reaction (PCR) assay, 16S rRNA gene sequencing, random amplification of polymorphic DNA (RAPD), PCR-restriction fragment length polymorphism of 16S rRNA, and antimicrobial susceptibility were evaluated. RESULTS: Compared with results for other techniques, results for the RAPD typing method with the RAPD1 primer reveal that it was the most discriminatory fingerprinting technique, and it allowed us to cluster Salmonella Enteritidis PT 4 isolates on the basis of their genetic similarity. CONCLUSIONS AND CLINICAL RELEVANCE: This study revealed the value of RAPD with the RAPD1 primer as a tool for epidemiologic investigations of Salmonella Enteritidis PT 4. It can be used in conjunction with PFGE and phage typing to determine the genetic relatedness of Salmonella Enteritidis isolates involved in outbreaks of disease. A reliable and highly discriminatory method for epidemiologic investigations is critical to allow investigators to identify the source of infections and consequently prevent the spread of Salmonella Enteritidis PT 4.  相似文献   
56.
57.
58.
59.
60.
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