全文获取类型
收费全文 | 26819篇 |
免费 | 1761篇 |
国内免费 | 2166篇 |
专业分类
林业 | 1458篇 |
农学 | 2476篇 |
基础科学 | 773篇 |
1986篇 | |
综合类 | 10505篇 |
农作物 | 1773篇 |
水产渔业 | 1126篇 |
畜牧兽医 | 5582篇 |
园艺 | 1710篇 |
植物保护 | 3357篇 |
出版年
2024年 | 178篇 |
2023年 | 545篇 |
2022年 | 915篇 |
2021年 | 1027篇 |
2020年 | 1063篇 |
2019年 | 1167篇 |
2018年 | 848篇 |
2017年 | 1190篇 |
2016年 | 1288篇 |
2015年 | 1098篇 |
2014年 | 1420篇 |
2013年 | 1583篇 |
2012年 | 1943篇 |
2011年 | 1798篇 |
2010年 | 1556篇 |
2009年 | 1498篇 |
2008年 | 1301篇 |
2007年 | 1317篇 |
2006年 | 1211篇 |
2005年 | 968篇 |
2004年 | 798篇 |
2003年 | 655篇 |
2002年 | 543篇 |
2001年 | 600篇 |
2000年 | 592篇 |
1999年 | 502篇 |
1998年 | 384篇 |
1997年 | 334篇 |
1996年 | 297篇 |
1995年 | 301篇 |
1994年 | 247篇 |
1993年 | 237篇 |
1992年 | 246篇 |
1991年 | 208篇 |
1990年 | 177篇 |
1989年 | 153篇 |
1988年 | 104篇 |
1987年 | 104篇 |
1986年 | 63篇 |
1985年 | 38篇 |
1984年 | 41篇 |
1983年 | 22篇 |
1982年 | 31篇 |
1981年 | 21篇 |
1980年 | 33篇 |
1979年 | 25篇 |
1978年 | 22篇 |
1977年 | 10篇 |
1976年 | 17篇 |
1955年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
71.
Madhu Aneja Thomas J. Gianfagna Prakash K. Hebbar 《Physiological and Molecular Plant Pathology》2005,67(6):1647
An isolate of Trichoderma harzianum Rifai from an infected cacao pod produces and secretes nonanoic (pelargonic) acid into a liquid culture medium. Nonanoic acid (NA) was very inhibitory to spore germination and mycelial growth of two cacao pathogens, Crinipellis perniciosa Stahel and Moniliophthora roreri Cif. H.C. Evans. It was highly active causing 75% inhibition of spore germination in an in vitro assay at a rate as low as 0.09 μM for M. roreri and 0.92 μM for C. perniciosa. Mycelial growth was comparatively less sensitive to inhibition, but still there was a 75% reduction in growth with 0.62 μM in M. roreri and 151 μM NA in C. perniciosa. In contrast, NA did not affect Trichoderma mycelial growth or spore germination at concentrations that were inhibitory to the pathogens. 6-pentyl-α-pyrone was also produced and secreted into the medium by T. harzianum, however; it was not antagonistic to the cacao pathogens. Although a number of metabolites produced by Trichoderma spp. have been identified in the past, this is the first report of NA production and secretion by any Trichoderma. The results suggest that NA may play a role in the successful use of some Trichoderma spp. isolates in the biocontrol of fungal diseases of plants. 相似文献
72.
Clovis S. Palmer Jennifer A. Saleeba Bruce R. Lyon 《Physiological and Molecular Plant Pathology》2005,67(6):427
A phytotoxic protein that evokes the typical symptoms of Verticillium wilt disease in seedlings of Gossypium hirsutum L. (Upland cotton) was isolated from culture filtrates of Verticillium dahliae. The protein was purified by ammonium sulfate precipitation, Sephadex-G100 fractionation, and native PAGE. The 18.5 kDa protein, designated VD18.5, appears to be a single subunit protein with an isoelectric point between 3 and 5. VD18.5 induces symptoms of leaf dehydration, chlorosis, necrosis and stem discoloration in seedlings of the disease susceptible cotton cultivar Siokra 1–4. The LD50 of VD18.5 on protoplasts of Siokra 1–4 was 18 μg mL−1. VD18.5 had no noticeable effect on Pima S-7, which is a disease resistant cultivar. Phytotoxic activity was partially destroyed at high temperature and was abolished by digestion with proteinase K. Mass spectrometry fingerprinting and protein sequence data from VD18.5 yielded no significant matches when submitted to the Mascot search engine and NCBI non-redundant protein databases, respectively. These results suggest that VD18.5 is a novel protein that may be involved in the development of some of the symptoms associated with Verticillium wilt disease in the cotton plant. 相似文献
73.
74.
75.
Fredrik I. Grünenfelder Dominik Weishaupt Ron Green Frank Steffen 《Veterinary radiology & ultrasound》2005,46(2):91-96
Fibrocartilaginous embolization (FCE) of the spinal cord is a common disease in large breed dogs. There are only a few reports about this entity in small breed dogs and it has never been reported in chondrodystrophic breed. For definitive diagnosis histopathologic examination is necessary. Magnetic resonance imaging (MRI) as a potential diagnostic tool for intravitam diagnosis of FCE has been mentioned before, but results have not been reported so far. This report describes the neurological findings and MRI results in three small breed dogs, including a Pekingese dog, with FCE of the spinal cord. The disease was suspected in two animals based upon clinical and MRI-appearance and confirmed in the third by histopathological examination. In all three cases, similar focal intramedullary lesions, consisting of hyperintensive signals on T2-weighted images, were detected. Based on these findings, high-field MRI may be used as an antemortem tool for the diagnosis of FCE. It is also shown that FCE can occur in chondrodystrophic dogs. 相似文献
76.
77.
78.
79.
中国香瓜与菜瓜地方品种资源白粉病抗性评价 总被引:5,自引:0,他引:5
春秋2个季节在温室利用风媒接种方法对搜集的102份香瓜和14份菜瓜种质资源进行了白粉病抗性评价,结果鉴定出7份香瓜和1份菜瓜高抗白粉病,其病情指数为零,1份菜瓜抗病,其病情指数0.9,表明我国香瓜和菜瓜地方品种资源中蕴涵着潜在的改良甜瓜白粉病抗性的基因资源。 相似文献
80.
Genetic diversity in populations of the fungi Phaeomoniella chlamydospora and Phaeoacremonium aleophilum on grapevine in France 总被引:4,自引:0,他引:4
B. Borie L. Jacquiot I. Jamaux-Despréaux P. Larignon J.-P. Péros † 《Plant pathology》2002,51(1):85-96
Isolates of Phaeomoniella chlamydospora ( Phc ) and Phaeoacremonium aleophilum ( Pha ), two haploid, deuteromycetous fungi, were obtained from vines showing symptoms of esca disease in different localities in two French regions, and within a single vineyard in one of these regions. The population genetic structure was determined in both fungi using random amplified polymorphic DNA (RAPD) analysis. Populations of Phc showed similar levels of diversity at local and regional levels. The most frequent Phc haplotypes were found in every population, and the frequencies of positive alleles of markers were similar across populations. The hypothesis that recombination had occurred was rejected for the full set of samples, but not for the samples reduced to haplotypes, indicating that Phc may be a recombining species. Different features were identified in Pha populations. First, the southern population of Pha appeared more diverse than the south-western populations. Second, genetic differentiation was identified between Pha populations from southern and south-western regions for several RAPDs. Finally, in the southern population of Pha no evidence for recombination was obtained, even by reducing the sample to haplotypes. Within the single vineyard surveyed, several haplotypes of both fungi were recovered and randomly distributed. Thus different infection events appeared to have occurred on a low spatial scale. Data from this study showed that haplotypes of both fungi were distributed over long distances geographically, and that most of the vineyards surveyed were infested by more than one haplotype of Phc and Pha . 相似文献