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   10032篇
  免费   536篇
  国内免费   205篇
林业   1500篇
农学   442篇
基础科学   160篇
  1579篇
综合类   1294篇
农作物   329篇
水产渔业   473篇
畜牧兽医   3982篇
园艺   358篇
植物保护   656篇
  2023年   74篇
  2022年   118篇
  2021年   154篇
  2020年   212篇
  2019年   131篇
  2018年   273篇
  2017年   260篇
  2016年   289篇
  2015年   267篇
  2014年   257篇
  2013年   538篇
  2012年   534篇
  2011年   517篇
  2010年   343篇
  2009年   274篇
  2008年   438篇
  2007年   498篇
  2006年   414篇
  2005年   362篇
  2004年   293篇
  2003年   289篇
  2002年   275篇
  2001年   219篇
  2000年   217篇
  1999年   187篇
  1998年   76篇
  1996年   66篇
  1995年   69篇
  1992年   115篇
  1991年   120篇
  1990年   139篇
  1989年   148篇
  1988年   125篇
  1987年   106篇
  1986年   106篇
  1985年   95篇
  1984年   94篇
  1983年   75篇
  1979年   100篇
  1978年   71篇
  1977年   62篇
  1975年   67篇
  1974年   83篇
  1973年   93篇
  1972年   68篇
  1971年   82篇
  1970年   75篇
  1969年   83篇
  1968年   65篇
  1967年   65篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
51.
Five animals in a colony of cynomolgus monkeys (Macaca fascicularis) died or were euthanatized because of alveolar echinococcosis, during a period of 5 years. The remainder of the colony was screened for possible infection with Echinococcus multilocularis, using serology and ultrasonography. A total of 46 animals out of a group of 55 were examined. The presence of anti-Em2 antibodies analyzed with enzyme-linked immunosorbent assay was demonstrated in 3 monkeys. In 2 of these 3 monkeys, multilocular structures compatible with metacestodal cysts in the liver were identified, using ultrasonography. The presence of alveolar echinococcosis was subsequently confirmed at postmortem examination in 1 animal. The other animals are still alive. Two other monkeys were negative in the serological examination but had cystic structures in the liver, which were identified as bile duct cysts at postmortem examination in 1 animal. The other monkey is still alive. These findings suggest that serology for antibodies against the Em2 antigen may represent a useful method in identifying animals that might be infected with E. multilocularis and are therefore at risk of developing fatal alveolar echinococcosis.  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.
袋鼠花的组织培养   总被引:8,自引:0,他引:8  
刘春  穆鼎 《园艺学报》2003,30(1):113-115
 对袋鼠花( Anigozanthos) 组织培养研究表明: 外植体消毒以0. 1 %升汞溶液浸泡, 7~8 min 为宜; 不同浓度激素对其愈伤组织形成、分化以及根的形成有不同的影响, 随着62BA 浓度的增加, 愈伤组织的诱导率有增加的趋势; 生长素与分裂素的比例决定着愈伤组织的分化; 小苗在1/ 2 MS 培养基上生根最好, 6-BA 对其生根有抑制作用。各培养阶段最适培养基: (1) 愈伤, MS + 6-BA 1 mg/L + NAA 0. 1 mg/L +3 %活性炭; (2) 芽诱导, MS + 6-BA 0. 5 mg/L + NAA 0. 5 mg/L ; (3) 生根, 1/ 2 MS + IBA 0. 2 mg/L。  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