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   252篇
  免费   14篇
  国内免费   5篇
林业   19篇
农学   2篇
  59篇
综合类   50篇
农作物   12篇
水产渔业   22篇
畜牧兽医   46篇
园艺   1篇
植物保护   60篇
  2023年   2篇
  2022年   2篇
  2021年   2篇
  2020年   2篇
  2019年   6篇
  2018年   2篇
  2017年   3篇
  2016年   9篇
  2015年   2篇
  2014年   7篇
  2013年   12篇
  2012年   11篇
  2011年   24篇
  2010年   10篇
  2009年   5篇
  2008年   8篇
  2007年   8篇
  2006年   13篇
  2005年   16篇
  2004年   1篇
  2003年   7篇
  2002年   3篇
  2001年   9篇
  2000年   6篇
  1999年   6篇
  1997年   4篇
  1996年   4篇
  1995年   1篇
  1994年   2篇
  1993年   8篇
  1992年   8篇
  1991年   8篇
  1990年   4篇
  1989年   9篇
  1988年   6篇
  1987年   5篇
  1986年   3篇
  1985年   4篇
  1984年   4篇
  1983年   1篇
  1982年   1篇
  1981年   2篇
  1979年   5篇
  1975年   1篇
  1974年   2篇
  1973年   4篇
  1970年   1篇
  1969年   1篇
  1964年   5篇
  1963年   2篇
排序方式: 共有271条查询结果,搜索用时 0 毫秒
1.
光活化农药的研究与应用   总被引:12,自引:6,他引:12  
结合作者近期的研究工作,对光活化农药的研究现状、作用机理、应用前景及其与新农药创 制的关系进行了综述。  相似文献   
2.
畜产品安全中存在的问题与分析   总被引:1,自引:0,他引:1  
阐述了我国畜产品安全现状,强调了其形势的严峻性和紧迫性,分析了当前存在的主要问题,并提出了改进措施和建议。  相似文献   
3.
Duration of immunity in foxes vaccinated orally with ERA vaccine in a bait.   总被引:2,自引:0,他引:2  
Red foxes (Vulpes vulpes) vaccinated orally with the ERA strain of rabies vaccine in a bait were challenged after 83 mo. Ten of 11 foxes that had seroconverted following vaccination resisted challenge with a virulent rabies virus which produced clinical signs of rabies in 6 of 6 unvaccinated foxes. Five of 11 vaccinated animals retained titers of rabies virus neutralizing antibody throughout the period. Although 6 of 11 had no detectable antibody at the time of challenge, 5 of these 6 resisted challenge and had an anamnestic response, as indicated by elevated titers of antibody when measured at day 77 postchallenge. These results show that foxes can be immunized successfully with a single oral dose of ERA vaccine, probably with protection against a lethal rabies challenge, for at least 7 y.  相似文献   
4.
苦楝果实中化学成分进一步研究及生物活性测定   总被引:19,自引:0,他引:19  
采用生物活性追踪法,从苦楝果实中分离得苦楝新醇(Ⅰ)、苦楝酮(Ⅱ)、苦楝醇(Ⅲ)、苦楝二醇(Ⅳ)、苦楝三醇(Ⅴ)、香草酸(Ⅵ)、香草醛(Ⅶ)和川楝素(Ⅷ),并根据波谱(1R,MS,′H—NMR,~(13)C—NMR)分析和理化常数测定确定其结构.其中Ⅱ、Ⅲ、Ⅳ和Ⅴ的21—H存在差向异构现象.生测结果表明,Ⅱ~Ⅴ和Ⅷ对菜青虫(Pieris rapae)有明显的拒食活性,Ⅷ还表现出明显的胃毒活性;Ⅰ、Ⅳ和Ⅶ仅表现出一定的拒食活性.  相似文献   
5.
CASE DESCRIPTION: A 4-year-old sexually intact female French Bulldog was evaluated because of lethargy, anorexia, and chronic rhinitis-sinusitis. The dog had nasal discharge of 18 months' duration; dorsal rhinotomies were performed 3 months and 2 weeks prior to referral. CLINICAL FINDINGS: On initial evaluation, intraventricular pneumocephalus and sinusitis were diagnosed; CSF analysis revealed high total protein concentration and mononuclear pleocytosis. The dog's condition improved with treatment. Two weeks after discharge, it was treated by a local veterinarian because of upper airway obstruction; 3 days later, the dog was referred because of seizures. Computed tomography revealed a large fluid-filled, left lateral ventricle and a soft tissue mass protruding through a cribriform plate defect. The mass was histologically consistent with brain tissue. Findings of clinicopathologic analyses were unremarkable. Results of cytologic examination of a CSF sample were indicative of septic, suppurative inflammation, and bacteriologic culture of CSF yielded Escherichia coli. TREATMENT AND OUTCOME: Amputation of the herniated olfactory bulb and antimicrobial treatment resolved the septic meningoencephalitis, but neurologic deficits recurred 6 weeks later. Definitive correction of the cribriform plate defect with bone and fascial grafts was attempted. Postoperative rotation of the bone graft resulted in cerebral laceration and hemorrhage, and the dog was euthanized. CLINICAL RELEVANCE: Findings suggest that following dorsal rhinotomy and nasal polypectomy surgery, the dog developed herniation of the left olfactory bulb, intra-ventricular pneumocephalus, and septic meningo-encephalitis because of a cribriform plate defect. Care must be taken to prevent rotation of bone grafts used in cribriform defect repair.  相似文献   
6.
7.
The objective of this research was to conduct a human factors engineering analysis of a grafting robot design using computer-aided 3D simulation technology. A prototype tubing-type grafting robot for fruits and vegetables was the subject of a series of case studies. To facilitate the incorporation of human models into the operating environment of the grafting robot, I-DEAS graphic software was applied to establish individual models of the grafting robot in line with Jack ergonomic analysis. Six human models (95th percentile, 50th percentile, and 5th percentile by height for both males and females) were employed to simulate the operating conditions and working postures in a real operating environment. The lower back and upper limb stresses of the operators were analyzed using the lower back analysis (LBA) and rapid upper limb assessment (RULA) functions in Jack. The experimental results showed that if a leg space is introduced under the robot, the operator can sit closer to the robot, which reduces the operator's level of lower back and upper limbs stress. The proper environmental layout for Taiwanese operators for minimum levels of lower back and upper limb stress are to set the grafting operation at 23.2 cm away from the operator at a height of 85 cm and with 45 cm between the rootstock and scion units.  相似文献   
8.
Natural spawning, early development and larviculture of the ornate goby Istigobius ornatus in captivity were studied for the first time. I. ornatus spawned 46 times from 31 October 2013 to 31 October 2014. Fecundity ranged from 246 to 10,214 eggs per clutch, with an average hatching rate of 77.8% ± 9.9% (M ± SEM). Fertilized eggs (1.31–1.54 × 0.46–0.50 mm in diameter) were adhesive demersal and oval‐shaped. Embryonic development lasted 84 hr at 27.5 ± 0.5°C. Newly hatched larvae [2.12 ± 0.04 mm in total length (TL)] transformed to the juvenile stage completely when TL was 7.79 mm. Effects of different water temperatures (24, 28 and 32°C) and salinities (10, 15, 20, 25, 30, 35 and 40 g/L) on per cent survivals (%) and survival activity indices (SAIs) were tested. Survival was not significantly different under different temperatures; SAIs was significantly higher at 28°C. Larvae showed the significantly higher survival and SAIs at salinities 10–30 g/L than at 35 and 40 g/L. Effect of different prey densities on survival was significantly higher in 7 days post hatch larvae fed 20 and 30 rotifers/ml. These findings could guide future programs in captive breeding technology development and commercial production of other marine ornamental gobies.  相似文献   
9.
 对不同时期感染甜菜花叶病毒(BtMV)的叶片,进行病理变化系列观察。早期侵染(7天前)的细胞质、细胞器均无变化,随着症状发展,风轮状内含体、束状内含体、细胞核卫星体,细胞质泡囊化旁类似病毒的束状结构,20天达到了高峰,风轮状及束状内含体一直持续两个月还存在。田间样品也观察到了典型的风轮状及束状内含体。细胞核卫星体出现很少。侵染后期,细胞质减少,叶绿体比相应健株提前出现淀粉粒,噬锇颗粒等,基粒片层也提前消解,表现细胞提前衰老的特征。此外细胞内还有许多健株没有的泡状结构。一种为旁壁体,可能与细胞壁加厚有关;一种为多重泡体的叠加,可能是液泡的吞噬作用加强与外源物质(BtMV)侵入有关;另外还有一种可能是过氧化物酶体或线粒体在病毒诱导下泡囊化,其作用不清楚。  相似文献   
10.
两种化合物对菜粉蝶幼虫超氧化物歧化酶的影响   总被引:3,自引:0,他引:3  
室内测试了菜粉蝶 Pieris rapae 4 龄幼虫超氧化物歧化酶的活性,并就 α -三噻吩( α -terthienyl)和化合物5[1-苯基-4-(3,4-亚甲基 二氧)苯基-丁二炔]两种化合物对其产生的影响进行了比较研究。结果表明,近紫外光照 (300~400 nm)可增强对幼虫超氧化物歧化酶活体活力( in vivo )和离体活力( in vitro )。经光敏化合物处理后,在紫外光照下,超氧化物歧化酶活体活力基本不受化合物 5的影响,但能被 α -三噻吩抑制;离体情况下,无论光照与否,化 合物5均不影响其活力, α -三噻吩在低剂量下有抑制作用,而在高剂量下则可使其活力 增强,显示了不同的剂量反应关系。表明无论在离体还是活体的情况下,幼虫对 α -三噻吩的光敏性优于化合物5。对两种化合物光敏作用的可能机理进行 了探讨。  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