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   8022篇
  免费   396篇
  国内免费   59篇
林业   1225篇
农学   209篇
基础科学   60篇
  1289篇
综合类   750篇
农作物   235篇
水产渔业   354篇
畜牧兽医   3667篇
园艺   217篇
植物保护   471篇
  2023年   52篇
  2022年   73篇
  2021年   95篇
  2020年   138篇
  2019年   74篇
  2018年   209篇
  2017年   173篇
  2016年   209篇
  2015年   190篇
  2014年   166篇
  2013年   416篇
  2012年   379篇
  2011年   374篇
  2010年   241篇
  2009年   158篇
  2008年   323篇
  2007年   360篇
  2006年   331篇
  2005年   273篇
  2004年   259篇
  2003年   240篇
  2002年   222篇
  2001年   153篇
  2000年   158篇
  1999年   114篇
  1992年   100篇
  1991年   112篇
  1990年   131篇
  1989年   139篇
  1988年   117篇
  1987年   98篇
  1986年   105篇
  1985年   95篇
  1984年   96篇
  1983年   74篇
  1979年   102篇
  1978年   70篇
  1977年   61篇
  1976年   49篇
  1975年   66篇
  1974年   82篇
  1973年   93篇
  1972年   68篇
  1971年   82篇
  1970年   76篇
  1969年   84篇
  1968年   65篇
  1967年   65篇
  1966年   49篇
  1965年   56篇
排序方式: 共有8477条查询结果,搜索用时 46 毫秒
51.
Fibrocartilaginous embolization (FCE) of the spinal cord is a common disease in large breed dogs. There are only a few reports about this entity in small breed dogs and it has never been reported in chondrodystrophic breed. For definitive diagnosis histopathologic examination is necessary. Magnetic resonance imaging (MRI) as a potential diagnostic tool for intravitam diagnosis of FCE has been mentioned before, but results have not been reported so far. This report describes the neurological findings and MRI results in three small breed dogs, including a Pekingese dog, with FCE of the spinal cord. The disease was suspected in two animals based upon clinical and MRI-appearance and confirmed in the third by histopathological examination. In all three cases, similar focal intramedullary lesions, consisting of hyperintensive signals on T2-weighted images, were detected. Based on these findings, high-field MRI may be used as an antemortem tool for the diagnosis of FCE. It is also shown that FCE can occur in chondrodystrophic dogs.  相似文献   
52.
Samples of water and sediment were taken from drains, reservoirs and wells from four commercial hardy ornamental nurseries with water recirculation systems. The samples were taken on seven different dates throughout a single year from August 1994 to July 1995. The samples were screened for Phytophthora species using five different methods: direct plating, three bait tests (using lupin seedlings, apples and Rhododendron leaves) and a DAS-ELISA (double-antibody sandwich enzyme-linked immunosorbent-assay) with two antisera. In the nurseries with old water recirculation systems, Phytophthora species were detected in the drains and in the reservoirs. In the nursery with a new recirculation system, the pathogens were only present in the drains. None of the water samples from wells in any of the nurseries were contaminated. Phytophthora species were present in the water as well as in the sediment samples from drains and reservoirs. They were detected in the water recirculation systems irrespective of the season. The number of isolates increased about sevenfold between late summer and spring. At least 12 different Phytophthora species were identified: some isolates were previously unrecorded species. The epidemiology of the pathogens in outdoor water recirculation systems as well as the importance of the results for commercial nurseries is discussed.  相似文献   
53.
In a nematode survey of Tylenchida carried out in groundnut (Arachis hypogaea L.) growing areas in the Mediterranean region of Turkey, 15 species were determined as belonging to ten genera of eight families within the superfamilies Tylenchoidea, Dolichodoroidea, Hoplolaimoidea and Anguinoidea. Each of them constitutes a new record on groundnut in Turkey, andScutylenchus tumensis Skwiercz andPratylenchus brachyurus (Godfrey) are reported for the first time in the nematofauna of Turkey.  相似文献   
54.
55.
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