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   564篇
  免费   60篇
林业   24篇
农学   11篇
基础科学   3篇
  88篇
综合类   61篇
农作物   20篇
水产渔业   34篇
畜牧兽医   319篇
园艺   13篇
植物保护   51篇
  2023年   9篇
  2022年   16篇
  2021年   30篇
  2020年   33篇
  2019年   36篇
  2018年   28篇
  2017年   22篇
  2016年   26篇
  2015年   20篇
  2014年   15篇
  2013年   28篇
  2012年   45篇
  2011年   48篇
  2010年   30篇
  2009年   19篇
  2008年   35篇
  2007年   26篇
  2006年   21篇
  2005年   20篇
  2004年   23篇
  2003年   14篇
  2002年   14篇
  2001年   6篇
  1999年   5篇
  1998年   2篇
  1997年   3篇
  1993年   3篇
  1992年   3篇
  1991年   1篇
  1990年   5篇
  1989年   2篇
  1988年   3篇
  1987年   2篇
  1986年   1篇
  1985年   4篇
  1984年   2篇
  1981年   1篇
  1980年   3篇
  1975年   1篇
  1974年   2篇
  1973年   2篇
  1969年   1篇
  1967年   2篇
  1966年   1篇
  1958年   1篇
  1950年   1篇
  1939年   1篇
  1926年   1篇
  1903年   2篇
  1900年   1篇
排序方式: 共有624条查询结果,搜索用时 125 毫秒
131.
Ultrasonography and radiography are commonly used for staging of lymphoma in horses, however there is little published information on imaging characteristics for horses with confirmed disease. The purpose of this retrospective, case series study was to describe ultrasonographic and radiographic findings for a group of horses with a confirmed diagnosis of lymphoma. A total of 13 horses were sampled. Lymphadenopathy (8/13), peritoneal effusion (6/13), splenic (6/13), and hepatic (5/13) lesions were the most frequently identified. The predominant splenic and hepatic ultrasonographic lesions were hypoechoic nodules, organomegaly, and changes in echogenicity. Digestive tract lesions were detected in three horses and these included focal thickening and decreased echogenicity of the small (2/13) and large intestinal (2/13) wall. Thoracic lesions were predominantly pleural effusion (4/13), lymphadenopathy (4/13), and lung parenchymal changes (3/13). Enlarged lymph nodes were detected radiographically (4/13) and/or ultrasonographically (2/13) in the thorax and ultrasonographically in the abdomen (7/13) and in the caudal cervical region (4/13). Findings supported the use of abdominal and thoracic ultrasonography for lymphoma staging in horses. Ultrasound landmarks for localizing cecal and caudal deep cervical lymph nodes were also provided.  相似文献   
132.
133.
134.
135.
136.
137.
138.
The myxozoan parasite Tetracapsuloides bryosalmonae is the causative agent of proliferative kidney disease (PKD), a highly damaging disease of cultured salmonid fish. Within this study, phylactolaemate bryozoans were collected from a river known to be endemic for PKD and subsequently cultured in the laboratory. Sequential developmental stages of T. bryosalmonae were studied by light microscopy within the living bryozoan colonies, allowing the identification of stages attached to host peritoneum, consistent with previous molecular evidence of cryptic stages. Infection resulted in the production of large numbers of spores, which were released from the bryozoans. Experimental exposure of rainbow trout (Oncorhynchus mykiss) to medium in which infected bryozoans were cultured resulted in clinical PKD. Rainbow trout were exposed to known numbers of T. bryosalmonae spores collected by micromanipulation, which had been released from mature spore sacs within colonies of the bryozoan Fredericella sultana. Exposure to one spore was sufficient to lead to development of PKD. These findings indicate that small numbers of bryozoans are capable of releasing sufficient spores to infect large numbers of fish, having implications for future control methods for PKD in salmonid farming.  相似文献   
139.
The precise manipulation of a propagating wave using phase control is a fundamental building block of optical systems. The wavefront of a light beam propagating across an interface can be modified arbitrarily by introducing abrupt phase changes. We experimentally demonstrated unparalleled wavefront control in a broadband optical wavelength range from 1.0 to 1.9 micrometers. This is accomplished by using an extremely thin plasmonic layer (~λ/50) consisting of an optical nanoantenna array that provides subwavelength phase manipulation on light propagating across the interface. Anomalous light-bending phenomena, including negative angles of refraction and reflection, are observed in the operational wavelength range.  相似文献   
140.
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