全文获取类型
收费全文 | 14254篇 |
免费 | 1053篇 |
国内免费 | 659篇 |
专业分类
林业 | 704篇 |
农学 | 852篇 |
基础科学 | 170篇 |
545篇 | |
综合类 | 4570篇 |
农作物 | 803篇 |
水产渔业 | 944篇 |
畜牧兽医 | 4857篇 |
园艺 | 675篇 |
植物保护 | 1846篇 |
出版年
2024年 | 282篇 |
2023年 | 300篇 |
2022年 | 457篇 |
2021年 | 554篇 |
2020年 | 573篇 |
2019年 | 616篇 |
2018年 | 402篇 |
2017年 | 521篇 |
2016年 | 544篇 |
2015年 | 551篇 |
2014年 | 736篇 |
2013年 | 746篇 |
2012年 | 897篇 |
2011年 | 887篇 |
2010年 | 763篇 |
2009年 | 751篇 |
2008年 | 691篇 |
2007年 | 697篇 |
2006年 | 665篇 |
2005年 | 524篇 |
2004年 | 479篇 |
2003年 | 378篇 |
2002年 | 300篇 |
2001年 | 355篇 |
2000年 | 359篇 |
1999年 | 299篇 |
1998年 | 207篇 |
1997年 | 166篇 |
1996年 | 158篇 |
1995年 | 170篇 |
1994年 | 137篇 |
1993年 | 133篇 |
1992年 | 148篇 |
1991年 | 100篇 |
1990年 | 81篇 |
1989年 | 76篇 |
1988年 | 47篇 |
1987年 | 48篇 |
1986年 | 25篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 14篇 |
1982年 | 18篇 |
1981年 | 10篇 |
1980年 | 20篇 |
1979年 | 17篇 |
1978年 | 7篇 |
1976年 | 8篇 |
1956年 | 5篇 |
1955年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
191.
AIM: To investigate the effect of flavonoids from stem and leaf of Scutellaria baicalonsis Georgi (SSF) on paired helical filament (PHF) abnormality and the regulatory mechanism of protein phosphatase (PP) in rats' brain induced by okadaic acid (OA). METHODS: Male Sprague-Dawley (SD) rats were microinjected with OA (200 ng/kg) by the lateral ventricle to establish a memory impairment model. Morris water maze was used to screen the memory impairment model. The successful model rats were continuous intragastric infusion (ig) SSF for 36 days. The relative protein expression of PHF, PP1, PP2A-Cα, PP2A-Cβ, PP2CA and PP2CB in the rat cerebral cortex and hippocampus were detected by Western blot. GinKgo biloba leaf flavonoids (GLF) were used as positive control drug. RESULTS: Compared with the sham-operated rats, the relative protein expression of PHF in the cerebral cortex and hippocampus and PP1 in cortex of model rats were significantly increased (P<0.01), and the protein expression of PP2A-Cα, PP2A-Cβ in the cerebral cortex and hippocampus and PP2CB in the hippocampus were decreased (P<0.05), while the relative protein expression of PP2CA and PP2CB in the cortex were significantly increased (P<0.01). SSF reversed the abnormality in the protein expression of PHF, PP2A-Cα and PP2A-Cβ in rat cortex and hippocampus and PP1 in rat cortex induced by OA (P<0.01), which had no significant effect on the relative protein expression of PP2CA and PP2CB. GLF also showed similar results to SSF. CONCLUSION: SSF significantly reduces the abnormal formation of PHF in rats' brain induced by OA, which may be related to the regulation of PP1, PP2A-Cα and PP2A-Cβ expression, but not with PP2CA and PP2CB expression. 相似文献
192.
Tim E. Carpenter Victor L. Coggins Clinton McCarthy Chans S. O’Brien Joshua M. O’Brien Timothy J. Schommer 《Preventive veterinary medicine》2014
Bighorn sheep currently occupy just 30% of their historic distribution, and persist in populations less than 5% as abundant overall as their early 19th century counterparts. Present-day recovery of bighorn sheep populations is in large part limited by periodic outbreaks of respiratory disease, which can be transmitted to bighorn sheep via contact with domestic sheep grazing in their vicinity. In order to assess the viability of bighorn sheep populations on the Payette National Forest (PNF) under several alternative proposals for domestic sheep grazing, we developed a series of interlinked models. Using telemetry and habitat data, we characterized herd home ranges and foray movements of bighorn sheep from their home ranges. Combining foray model movement estimates with known domestic sheep grazing areas (allotments), a Risk of Contact Model estimated bighorn sheep contact rates with domestic sheep allotments. Finally, we used demographic and epidemiologic data to construct population and disease transmission models (Disease Model), which we used to estimate bighorn sheep persistence under each alternative grazing scenario. Depending on the probability of disease transmission following interspecies contact, extirpation probabilities for the seven bighorn sheep herds examined here ranged from 20% to 100%. The Disease Model allowed us to assess the probabilities that varied domestic sheep management scenarios would support persistent populations of free-ranging bighorn sheep. 相似文献
193.
桑树品种对黄化型萎缩病抗病性与过氧化物酶关系的研究 总被引:3,自引:2,他引:3
不同抗黄化型萎缩病能力的桑品种枝皮的过氧化物酶同工酶聚丙烯酰胺凝胶电泳表明,品种间同工酶带差异明显,其酶带数目与桑品种抗病性成正相关。不同抗性品种接种类菌原体(MLO)后,经不同时段过氧化物酶同工酶酶带区和酶带数与未接种的无明显差异,但酶带均有不同程度的加强,且随着接种后经过日数的增多而加强。因此,认为过氧化物酶是桑树抗MLO的机制组分之一。 相似文献
194.
生物农药防治温室秋番茄病毒病效果研究 总被引:1,自引:0,他引:1
为减轻番茄病毒病的发生危害,减少化学农药用量、残留和环境污染,该文采用测报调查、随机区组设计和统计分析等方法,开展了生物农药香菇多糖+赤·吲乙·芸薹(碧护)和宁南霉素+赤·吲乙·芸薹防治番茄病毒病田间药效试验。结果表明:在温室大棚秋季番茄病毒病发生较重情况下,每667m2用0.5%香菇多糖水剂200m L+碧护可湿性粉剂40g、8%宁南霉素水剂60m L+碧护可湿性粉剂40g,7d施药1次,连续施用4次,药后10、17、26、35d,防治效果均在88%、87%、78%和67%以上,且2药剂防治效果差异不显著,香菇多糖+碧护极显著高于盐酸吗啉胍(对照药剂)+碧护,宁南霉素+碧护显著高于盐酸吗啉胍+碧护。因此,香菇多糖+碧护和宁南霉素+碧护不仅可以作为防治病毒病的理想药剂,而且可以作为现代农业示范区、无公害农产品、绿色农产品和有机农产品防治病毒病的理想药剂。 相似文献
195.
四川盆地常见草坪病害与防治 总被引:9,自引:0,他引:9
通过对四川盆地常见的草坪草病害,如:锈病、褐斑病、白粉病等主要草坪病害的症状进行描述,探索草坪病害防治的有效措施,降低草坪草养护管理成本,提高生存环境质量。 相似文献
196.
侵染芝麻的芜菁花叶病毒黄斑黄化株系的初步鉴定 总被引:1,自引:0,他引:1
本文对较为普遍发生的芝麻黄化型病害分离物YS—I进行了初步病原鉴定。该分离物浸染芝麻引起叶片多角型黄斑黄化,植株不能正常开花结实。摩擦接种YS—I能够侵染7科9种植物,局部侵染苋色藜、千日红、蚕豆;系统侵染油菜、百日菊等。该病毒能够由桃蚜以非持久方式进行传播。病毒在芝麻病组织汁液中存活期2天,钝化温度55℃,稀释限点4×10~(-1)。提纯病毒为弯曲线状粒体,大小约为15×810nm。血清学上该病毒与芜菁花叶病毒密切相关,与花生条纹病毒、大豆花叶病毒和黄花叶病毒不相关。在TuMV株系鉴别寄主上,YS—I与引起芝麻矮化坏死的TuMV—Se具有明显不同症状反应。因此,YS—I为芜菁花叶病毒的又一芝麻分离株(TuMy—YS)。 相似文献
197.
本文通过对花生病毒病的病情消长与气候因素的关系研究得出,温度、湿度与病情消长有显著的相关性,且温度、湿度与病情消长有显著的多元回归关系。 相似文献
198.
Shotaro KUBO Morihiro TATENO Yasuaki ICHIKAWA Yasuyuki ENDO 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2015,77(10):1275-1279
Tick-borne diseases are often encountered in canine clinical practice. In the present
study, a molecular epidemiological survey of dogs in Japan was conducted to understand the
prevalence and geographical distribution of Babesia spp.,
Hepatozoon spp., Ehrlichia spp. and
Anaplasma spp. Pathogen-derived DNA in blood samples obtained from 722
dogs with a history of exposure to ticks and/or fleas was examined by PCR. The prevalence
of Babesia gibsoni, Babesia odocoilei-like species,
Hepatozoon canis and Ehrlichia
spp./Anaplasma spp. was 2.4% (16/722), 0.1% (1/722), 2.5% (18/722) and
1.5% (11/722), respectively. While B. gibsoni and
Ehrlichia spp./Anaplasma spp. were detected in the
western part of Japan, H. canis was detected in Tohoku area in addition
to western and central parts of Japan. 相似文献
199.
为了有效防控甘薯茎基部腐烂病的发生,2012-2016年连续5年开展了甘薯茎基部腐烂病的病原菌鉴定、发病规律调查和防控试验。结果表明:引起台州甘薯茎基部腐烂病的病害有甘薯白绢病(Sclerotium rolfsii)、甘薯茎枯病(Rhizoctonia solani)、甘薯茎腐病(Dickeya dadantii),以及以病原菌Fusarium solani引起的甘薯茎基部腐烂病害,而且试验病区甘薯发病是以后者为主,该病害在台州多在6月底7月初始发,8月和9月份雨水多湿度大的情况下盛发,近来危害越来越严重,产量损失达50%以上甚至绝收;不同耕作制、脱毒苗扦插、地膜覆盖和施用有机肥等栽培措施都不能降低发病率和减少薯块产量损失,而推迟甘薯扦插期至6月底可以在一定程度上减轻损失;鉴定筛选到了抗病低代材料YA3008,产量高达38542.5 kg/hm2;筛选到了具有一定防治效果的化学药剂32.5%阿米妙收。综合5年来的试验研究结果认为,防控甘薯茎基部腐烂病的策略、途径应以选育与应用抗病品种为基础,辅之以综合运用其他农业防控和化学防控措施。 相似文献
200.