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   440篇
  免费   102篇
  国内免费   25篇
林业   6篇
农学   59篇
基础科学   13篇
  9篇
综合类   256篇
农作物   102篇
水产渔业   6篇
畜牧兽医   22篇
园艺   9篇
植物保护   85篇
  2025年   13篇
  2024年   8篇
  2023年   5篇
  2022年   9篇
  2021年   18篇
  2020年   22篇
  2019年   14篇
  2018年   11篇
  2017年   9篇
  2016年   19篇
  2015年   14篇
  2014年   41篇
  2013年   24篇
  2012年   33篇
  2011年   31篇
  2010年   35篇
  2009年   34篇
  2008年   34篇
  2007年   17篇
  2006年   27篇
  2005年   13篇
  2004年   17篇
  2003年   13篇
  2002年   9篇
  2001年   12篇
  2000年   12篇
  1999年   4篇
  1998年   8篇
  1997年   7篇
  1996年   10篇
  1995年   9篇
  1994年   10篇
  1993年   4篇
  1992年   8篇
  1991年   4篇
  1990年   1篇
  1989年   5篇
  1988年   3篇
排序方式: 共有567条查询结果,搜索用时 15 毫秒
1.
Iridophores are iridescent cutaneous pigment cells found in reptiles, fish, and amphibians. Neoplasms of iridophores are rarely reported, and little is known about their behaviour, metastatic potential, and prognostic indicators. This paper reports details of the clinical course and pathological findings of metastatic iridophoroma in a veiled chameleon (Chamaeleo calyptratus) and red-barred dragon (Ctenophorus vadnappa). The veiled chameleon presented with a subcutaneous mass on the right lateral elbow and was diagnosed as an iridophoroma on fine needle aspiration. It was otherwise clinically normal. Within 35 days of excision, multiple secondary skin masses developed which were often non-pigmented and required microscopic examination to identify them as iridophoroma metastases. There were in total 54 days between the first detection of the primary mass and end stage, extensive cutaneous and visceral metastatic disease, and there had been no detectable primary mass during routine clinical examination 128 days prior to death. The red-barred dragon presented with a white sub-mandibular mass. While undergoing an excisional biopsy the animal expired, post-mortem examination revealed a cutaneous malignant iridophoroma with tumour cell clusters seen in pulmonary arterial vessels, suggesting that surgical handling of iridophoroma could precipitate the release of circulating tumour cell clusters. This is the first iridophoroma described in a red-barred dragon and the second report of a malignant iridophoroma in a veiled chameleon. Timely detection and careful excision of lizard iridophoroma may be an important factor in clinical outcome.  相似文献   
2.
    
ABSTRACT

Sugarcane smut, caused by Sporisorium scitamineum, is one of the most important sugarcane diseases in Japan. Wild sugarcane, Saccharum spontaneum, is known to be a key breeding material to obtain high-yielding clones. In this study, we sought to identify Japanese wild sugarcane accessions with high resistance to smut. Thirty wild sugarcanes and three sugarcane cultivars were tested by the pinprick method. The results of the inoculation tests aided in identifying wild sugarcanes with high resistance to smut disease, namely JW90, Iriomote8, and Iriomote15. After screening the germplasm, progeny distribution of smut resistance from the inoculation test and dry matter productivity in the smut disease-free field were compared. The highly resistant wild sugarcane accession had a much better impact on progeny distribution of smut resistance compared with the susceptible accession. No relationship was found between smut resistance and dry matter productivity in both populations.  相似文献   
3.
4.
A major component rice varietv of Xiangwanxian 9 (a late Indica variety) with 13.1%, 15.6% and 18.3% of the moisture was respectively mixed with three ad-ditive varieties in 13% of moisture at ration of 7:3 for processing assorted rices. Head rice recovery of the treatments was determined 24 hours later. Analysis indicated sig-nificant differences exist in the effects produced by the component varieties, their moistures and the component variety moisture.  相似文献   
5.
We investigated the optimal timing of simeconazole (RS-2-(4-fluorophenyl)-1-(1H-1,2,4-triazol-1-yl)-3-trimethylsilylpropan-2-ol) application for controlling rice kernel smut in field trials in Miyagi Prefecture, Japan, using formulations of simeconazole (1.5% granules). The field tests revealed that a submerged application of simeconazole granules (450–600 g ai/ha) at 1–5 weeks before heading was highly effective against kernel smut, with treatments 1–2 weeks before heading being the most effective. Submerged application of the fungicide at 2–5 weeks before heading was also highly effective against false smut, with treatment 3 weeks before heading being the most effective. These periods overlap the timing for optimal application of simeconazole to control rice sheath blight and ear blight. Consequently, we concluded that treatment with simeconazole 2–3 weeks before heading can be a useful tool for controlling all four diseases.  相似文献   
6.
7.
(1)采用针刺接种、催芽接种和浸渍接种等3种接种方式对13个甘蔗品种进行抗黑穗病能力的评价,结果表明:品种间对黑穗病的抗性存在着真实的遗传差异;浸渍接种可使品种的形态学抗性和生理生化抗性得到充分体现,客观而真实地反映品种的抗病性;针刺接种或催芽接种可越过形态学障碍而直接检查品种生理生化的抗性反应。(2)采用浸渍接种法测定8个甘蔗品种在整个发病生长季产生黑穗病株的发展动态,从累积的丛感染率和感染率的发展曲线分析表明:黑穗病鞭子在整个生长季的发生,明显有3个稳定的发展水平,丛感染率虽能较好地反映品种的初侵染,而茎感染率则更适于检测再侵染的状况,更加准确地评价品种的抗病性;茎感染率的发展曲线采用模拟是适宜的,其中K值作为品种抗病性鉴定指标以评价甘蔗品种抗黑穗病的育种潜力是可行的;采用病情流行总量作为品种抗病性鉴定指标比其他流行学参数(如Ymax.Yo.P.r)可能会更合理些,与K值的评价效果取得了一致性。  相似文献   
8.
人工培养条件下稻曲病菌厚垣孢子产生因素初探   总被引:1,自引:0,他引:1  
本文通过对稻曲病菌在不同培养基、不同营养条件(碳源和氮源)、不同pH值、不同温度和光照及不同代数的菌株在PSA上产孢能力的研究,初步明确,PSA是适宜的产孢培养基;2~3代菌株最易产孢;NH4CI和KNO3对厚垣孢子产生有一定的作用;适宜产孢的温度为15~25℃,但15℃和20℃培养时间较长;培养基适宜的pH值是5~7,以pH6为最佳;光照对厚垣孢子的产生数量及时间都有很大的影响,光暗交替是适宜的培养条件。  相似文献   
9.
张志光 《排灌机械》2004,22(3):34-36,46
为使井灌用户能更加科学地选用井泵,降低抽水费用,提高泵站装置效率,阐述了井泵选型的步骤及井泵工作点校核的方法,探讨了井泵在选型时应考虑的因素,给出了求取机井最优涌水量和井泵扬程的简易方法。  相似文献   
10.
从气候条件、播种时间、玉米品种、种植密度、秸秆还田、化学防治、栽培方式7个方面系统地分析了滨州市玉米丝黑穗病大发生的原因。根据滨州市的实际情况,提出了以推广抗病品种和应用玉米种衣剂包衣为主的综合防治方法,以促进该地区玉米生产。  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