全文获取类型
收费全文 | 741篇 |
免费 | 41篇 |
专业分类
林业 | 57篇 |
农学 | 13篇 |
基础科学 | 4篇 |
98篇 | |
综合类 | 122篇 |
农作物 | 15篇 |
水产渔业 | 28篇 |
畜牧兽医 | 386篇 |
园艺 | 5篇 |
植物保护 | 54篇 |
出版年
2020年 | 7篇 |
2019年 | 13篇 |
2018年 | 13篇 |
2017年 | 8篇 |
2016年 | 19篇 |
2015年 | 9篇 |
2014年 | 13篇 |
2013年 | 32篇 |
2012年 | 18篇 |
2011年 | 39篇 |
2010年 | 19篇 |
2009年 | 17篇 |
2008年 | 23篇 |
2007年 | 27篇 |
2006年 | 20篇 |
2005年 | 15篇 |
2004年 | 22篇 |
2003年 | 21篇 |
2002年 | 23篇 |
2001年 | 21篇 |
2000年 | 10篇 |
1999年 | 19篇 |
1998年 | 18篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 14篇 |
1991年 | 13篇 |
1990年 | 16篇 |
1989年 | 15篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 22篇 |
1984年 | 7篇 |
1982年 | 7篇 |
1979年 | 10篇 |
1978年 | 10篇 |
1977年 | 7篇 |
1975年 | 12篇 |
1974年 | 15篇 |
1973年 | 9篇 |
1972年 | 6篇 |
1971年 | 14篇 |
1970年 | 7篇 |
1969年 | 16篇 |
1967年 | 14篇 |
1965年 | 7篇 |
排序方式: 共有782条查询结果,搜索用时 15 毫秒
101.
102.
103.
104.
105.
106.
107.
108.
ABSTRACT Thirteen aphid species were tested for their ability to transmit Pennsylvania isolates of Plum pox virus (PPV) collected in Columbia (PENN-3), Franklin (PENN-4), and York (PENN-7) Counties, PA. Four species, Aphis fabae, A. spiraecola, Brachycaudus persicae, and Myzus persicae, consistently transmitted PPV in preliminary transmission tests. Two species, Metopolophium dirhodum and Rhopalosiphum padi, were occasional inefficient vectors. Toxoptera citricida, from Florida, also was an effective vector but it does not occur in major stone-fruit-growing states. Species not transmitting PPV in parallel tests included Acyrthosiphon pisum, Aphis glycines, Aulacorthum solani, Macrosiphum euphorbiae, Rhopalosiphum maidis, and Sitobion avenae. When given a 3-day probing access period simultaneously on PPV-infected peach seedlings and healthy peach seedlings, Myzus persicae, Aphis spiraecola, A. fabae, and B. persicae transmitted PPV to 63, 31, 38, and 32% of the healthy peach seedlings, respectively. When given a similar probing period on PPV-infected peach fruit and healthy peach seedlings, the same aphid species transmitted PPV to 50, 35, 0, and 0% of seedlings, respectively. Results support the hypothesis of secondary PPV spread by indigenous aphids in Pennsylvania, and suggest that PPV-infected fruit has the potential to function as a virus source for long-distance dispersal. 相似文献
109.
Possible Root Infection of Cercospora beticola in Sugar Beet 总被引:1,自引:0,他引:1
Jessica Vereijssen Hans J.H.M. Schneider Aad A.J. Termorshuizen 《European journal of plant pathology / European Foundation for Plant Pathology》2004,110(1):103-106
A potential primary infection site of the foliar pathogen Cercospora beticola in sugar beet is described. Sugar beet seedlings of the susceptible cv. Auris were grown in a standard soil for 14 days. A monoconidial culture of a C. beticola isolate was grown to produce conidia. In experiment 1, roots were immersed in a conidial suspension of isolate code IRS 00-4, or in tap water (control), for 2 days. After incubation seedlings were potted in a peat – fine river sand mixture and placed at low relative humidity (RH) (<80%) or high RH (100%). Twelve days after infection, seedlings at high RH showed more disease incidence (90%) than seedlings grown at low RH (disease incidence = 25%), whereas no disease symptoms developed in the control seedlings. Cercospora leaf spots (CLSs) developed on the cotyledons, leaves, petioles and stems of the seedlings. In experiment 2, roots were immersed in a conidial suspension of isolate code IRS 00-2 for 5 h. Thirty-four days after infection at high RH, 100% disease incidence was observed in the treated seedlings and one CLS in the control treatment. First indications of leaf spot development were observed as reddish purple discolouration of individual parenchymatic cells. Because splash dispersal and symptoms due to infested soil were excluded, we showed that it is possible to obtain CLS symptoms in sugar beet seedlings when their roots were immersed in conidial suspensions of C. beticola, thus demonstrating that roots can be a primary infection site. 相似文献
110.
Tiemann U Brüssow KP Jonas L Pöhland R Schneider F Dänicke S 《Journal of animal science》2006,84(1):236-245
Feeding experiments with diets containing Fusarium toxin-contaminated wheat were conducted to clarify the pathogenesis of immunological effects of Fusarium toxins to porcine spleen cells. Contaminated diets were fed to 36 Landrace prepubertal gilts for 35 d. Concentrations (as-fed basis) of the indicator toxins deoxynivalenol (DON) and zearalenone (ZON), respectively, were 210 and 4 (control--group I), 3,070 and 88 (group II), 6,100 and 235 (group III), and 9,570 and 358 microg/kg (group IV). No signs of hyperestrogenism or uterotrophic effects were observed because of dietary treatments. The feeding of mycotoxin-contaminated diets did not cause gross pathological findings in the spleens of animals. In vivo, no inhibitory effects were detected on concanavalin A-stimulation of blood lymphocytes; however, the proliferation rate of splenocytes was inhibited (P < 0.05) in pigs fed the diet with the highest DON/ZON concentration. With in vitro studies, lower proliferation rates of blood lymphocytes and splenocytes preexposed to DON were detected. Serum IgA concentrations of pigs in group II were increased (P < 0.05) compared with the baseline value before feeding the DON/ZON diet. The histopathological data indicated elevated (P < 0.05) iron staining in the red pulp of spleens in gilts from groups I to IV after 35 d of feeding. The presence of hemosiderin particles in the spleen sections was confirmed by transmission electron microscopic investigation. Together, the results provide evidence of spleen dysfunction (hemosiderosis) in the absence of clinical signs, especially in pigs fed higher concentrations (groups III and IV) of Fusarium toxin-contaminated wheat. 相似文献