全文获取类型
收费全文 | 392篇 |
免费 | 45篇 |
国内免费 | 23篇 |
专业分类
林业 | 178篇 |
农学 | 1篇 |
基础科学 | 1篇 |
3篇 | |
综合类 | 129篇 |
农作物 | 1篇 |
水产渔业 | 106篇 |
畜牧兽医 | 10篇 |
园艺 | 1篇 |
植物保护 | 30篇 |
出版年
2024年 | 2篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 1篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 9篇 |
2016年 | 6篇 |
2015年 | 4篇 |
2014年 | 8篇 |
2013年 | 24篇 |
2012年 | 22篇 |
2011年 | 21篇 |
2010年 | 22篇 |
2009年 | 23篇 |
2008年 | 22篇 |
2007年 | 39篇 |
2006年 | 22篇 |
2005年 | 20篇 |
2004年 | 21篇 |
2003年 | 18篇 |
2002年 | 17篇 |
2001年 | 10篇 |
2000年 | 13篇 |
1999年 | 5篇 |
1998年 | 5篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 15篇 |
1994年 | 9篇 |
1993年 | 7篇 |
1992年 | 8篇 |
1991年 | 9篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
排序方式: 共有460条查询结果,搜索用时 125 毫秒
1.
2.
1987~1992年连续6年研究结果表明,白跗平腹小蜂Anastatusalbitarsis对马尾松毛虫Dendrolimuspunctatus、柳杉毛虫Dendrolimuslatipennis、水青蛾Actiasseteneningpoana等13种主要森林害虫卵有较明显的抑制作用。在林间,该蜂对马尾松毛虫第1、2代卵的自然抑制力分别力16.55%和22.29%,对柳杉毛虫越冬代卵的自然抑制力为23.45%;对水青蛾第1、2代卵的抑制力分别力5.49%和2.63%;在林间,人为释放白跗平腹小蜂对第1代马尾松毛虫卵的校正抑制力为33.5%,在室内12.3~28℃范围内,每头雌峰对马尾松毛虫、水青蛾和柞蚕剖腹卵的日破坏数(寄生数)分别力15、18和26粒,一生破坏数分别为56、91和208粒。即使虫卵即将孵化,该峰同样亦能寄生,并羽化出正常的子代白跗平腹小蜂。 相似文献
3.
4.
P. Larignon B. Dubos 《European journal of plant pathology / European Foundation for Plant Pathology》1997,103(2):147-157
Cross sections of woody stems of 309 diseased grapevines collected in France showed two kinds of necrosis typical of esca: a) A central light-colored necrosis of soft consistency, consisting of three zones, preceded by a centrally discolored wood, and b) a sectorial light-colored necrosis composed of two zones preceded by a sectorial brown necrosis. Isolations showed that different microflora was associated with each necrosis. Phaeoacremonium aleophilum and Phaeoacremonium chlamydosporum occurred in the discolored wood and the zones bordering the central decayed wood. Eutypa lata was the main fungus isolated from sectorial brown necrosis and the zones adjoining the decay wood. Phellinus punctatus was isolated from the sectorial and central decayed wood. Stereum hirsutum was present in decayed wood of 15 grapevines with esca symptoms not inhabited by P. punctatus. Wood decay tests and pathogenicity tests showed that S. hirsutum and P. punctatus were responsible for the decayed wood. Phaeoacremonium chlamydosporum and S. hirsutum produced a centrally discolored wood similar to that found in esca-affected vines. Phaeoacremonium aleophilum caused a sectorial brown necrosis of soft texture. From these studies, it was found that esca is a complex disease involving several microorganisms whose role in the process leading to wood degradation is discussed. 相似文献
5.
用模糊综合评判法预测马尾松毛虫幼虫高峰期发生量 总被引:1,自引:0,他引:1
为了提高马尾松毛虫一代、二代幼虫高峰期发生量预报的准确性,为有效防治马尾松毛虫提供科学依据,本文运用模糊综合评判的6个数学模型预测安徽省潜山县马尾松毛虫一代、二代幼虫高峰期的发生量,验证预报1989年、1994年、2002年和2017年一代马尾松毛虫幼虫高峰期发生量,预报结果分别为2级、4级、2级和1级,与实况级别完全吻合,预报结果准确。预报1989年、1994年、2002年和2017年二代马尾松毛虫幼虫高峰期发生量,预报结果依次是4级、5级、2级和1级。同样与实况级别全部相同。预报的准确率为100%,模糊综合评判法是一个运算简便、准确性高的预报方法。 相似文献
6.
浙江省龙泉市植物资源极其丰富,有松木林面积4.66万hm2,马尾松毛虫是为害马尾松林的大敌,防控马尾松毛虫发生为害任务十分艰巨。 相似文献
7.
《Journal Of Applied Aquaculture》2013,25(1-2):95-103
Abstract The passive sock grading method used by commercial channel catfish, Ictalurus punctatus, farmers to grade and reduce the number of under-sized fish delivered to processing plants was assessed on an experimental scale. The assessment was conducted at the Aquaculture Research Station at the University of Arkansas, Pine Bluff in 0.1-ha earthen ponds. A rectangular holding sock was fabricated with dimensions of 0.9 m in width, 2.4 m in length, and 1.2 m in depth. The mesh size of the sock was 4.4 cm and the mesh material was nylon netting, 0.64 cm in diameter. Seventeen groups of channel catfish, were graded, with group weights ranging from approximately 115 to 370 kilograms. Fish were held in the sock for approximately three hours (±0.27 hours). The water temperature during the trials ranged from 7.3°C to 28.7°C. The percent removal of fish less than 0.45 kg during the three-hour holding period ranged from 27.6% to 73.3%. Overall, sock grading efficiency increased with increasing water temperature and at water temperatures above 15°C a greater percentage of fish less than 0.45 kg were not retained in the socks. 相似文献
8.
研究表明:在松林内,14种松毛虫卵寄生蜂中有9种能寄生柞蚕卵。利用柞蚕卵作为马尾松毛虫卵寄生蜂的补充寄主是可行的。补充寄主的林地,卵蜂种群密度比对照提高0.68~1.43倍,而长年补充又比阶段补充增加1.37倍,比对照区增加2倍。林间补充寄主后提高了平腹小蜂和白角小蜂的种群密度。第一代松毛虫卵期总寄生率补充寄主区较对照区提高5.16~28.96%,第二代提高3.62~24.97%;第三代提高8~17.99%。根据卵蜂在不同生态条件下的消长规律,补充寄主的方法应有所不同,在地被物稀少的松林中补充寄主的次数应多一些,而在地被物丰富的松林中,补充寄主的次数可相应减少。 相似文献
9.
10.