全文获取类型
收费全文 | 2245篇 |
免费 | 184篇 |
国内免费 | 141篇 |
专业分类
林业 | 74篇 |
农学 | 89篇 |
基础科学 | 5篇 |
39篇 | |
综合类 | 528篇 |
农作物 | 88篇 |
水产渔业 | 235篇 |
畜牧兽医 | 1128篇 |
园艺 | 29篇 |
植物保护 | 355篇 |
出版年
2024年 | 16篇 |
2023年 | 32篇 |
2022年 | 69篇 |
2021年 | 94篇 |
2020年 | 114篇 |
2019年 | 121篇 |
2018年 | 71篇 |
2017年 | 93篇 |
2016年 | 102篇 |
2015年 | 96篇 |
2014年 | 105篇 |
2013年 | 125篇 |
2012年 | 134篇 |
2011年 | 151篇 |
2010年 | 116篇 |
2009年 | 112篇 |
2008年 | 94篇 |
2007年 | 111篇 |
2006年 | 98篇 |
2005年 | 74篇 |
2004年 | 67篇 |
2003年 | 48篇 |
2002年 | 63篇 |
2001年 | 63篇 |
2000年 | 44篇 |
1999年 | 30篇 |
1998年 | 37篇 |
1997年 | 39篇 |
1996年 | 24篇 |
1995年 | 25篇 |
1994年 | 26篇 |
1993年 | 18篇 |
1992年 | 19篇 |
1991年 | 28篇 |
1990年 | 19篇 |
1989年 | 17篇 |
1988年 | 16篇 |
1987年 | 9篇 |
1986年 | 7篇 |
1985年 | 8篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1978年 | 5篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1956年 | 4篇 |
1955年 | 1篇 |
排序方式: 共有2570条查询结果,搜索用时 250 毫秒
71.
以BALB/c小鼠为实验动物模型,对actA基因和plcB基因双缺失的产单核细胞李氏杆菌(LM)yzuLM1-2菌株进行感染动力学研究。分别用减毒突变株yzuLM1-2和野生型菌株yzuLM4给BALB/c小鼠静脉注射或灌服,并对脏器中LM的分布动态进行测定。结果显示,在显著高于野生型菌株感染剂量的条件下注射或灌服接种后,减毒突变株组小鼠肝和脾中的LM数量迅速下降,被清除的速度显著快于野生型菌株组。溶血素(LLO)抗体的测定结果显示,减毒突变株菌能和野生型菌同样激发较高水平的抗体。小鼠免疫保护试验结果显示,减毒突变株免疫组对同种血清型LM的攻击具有较好的免疫保护力,可达100%。结果表明,yzuLM1-2突变株侵袭力下降,致病力降低,能激发较高水平的抗体产生,可以作为预防动物李氏杆菌病的候选疫苗菌株,并为用作运送外源保护性抗原的载体提供了材料。 相似文献
72.
73.
The wheat cultivar Kariega expresses complete adult plant resistance against stripe rust, whereas cv. Avocet S is susceptible. Using confocal laser scanning microscopy, initial fungal penetration into flag leaves was identical in both cultivars, with directional germ-tube growth towards stomata that were penetrated without the formation of an appressorium, followed by differentiation of a substomatal vesicle, infection hyphae, haustorial mother cells and haustoria. During the following 4 days, further fungal development occurred more quickly in the resistant than in the susceptible cultivar. However, by 7 days postinoculation (dpi) the situation changed, with exponential growth of the pathogen occurring only in the susceptible line. Induced cellular lignification, a typical defence reaction of cereals, was observed at 4 dpi in the resistant cultivar, and 2 days later lignified tissue completely surrounded the fungal colonies. In the susceptible cultivar, isolated lignified host cells occurred at 6 dpi, and long, unbranched fungal hyphae outgrowing the resistance reaction were observed. 相似文献
74.
Aleš Lebeda Michaela Sedlářová James Lynn David A. C. Pink 《European journal of plant pathology / European Foundation for Plant Pathology》2006,115(4):431-441
Phenotypic and histological responses of cultivated lettuce (Lactuca sativa) and wild relatives L. saligna, L.␣virosa as well as interspecific crosses derived from L. sativa × L. serriola to two races of Bremia lactucae (CS2, CS9) were investigated. With the exception of L. sativa genotypes, all accessions and hybrids expressed incomplete or complete resistance to both pathogen races, with slight differences at seedling and adult plant stages, respectively. Histological features of the interactions (development of pathogen infection structures and host hypersensitive response to attempted infection) were studied on leaf discs 48 h after inoculation. Interactions with similar phenotypic expression of resistance were characterized by significant variation in rate of development of pathogen infection structures and hypersensitive reactions. Differences found within eight Lactuca spp. accessions and hybrids challenged by two distinct pathogen races are interpreted and discussed. 相似文献
75.
猪链球菌2型四川分离株猪体回归试验 总被引:5,自引:3,他引:5
选用35~38日龄的健康断奶仔猪21头,分3组,用2005四川分离株SSsc0501分别经静脉、肌肉注射和口服3种途径感染,进行猪体回归试验。肌肉注射组(含菌0.6×108个/mL)16 h开始出现症状,至36 h全部死亡,发病率、病死率均为100%;静脉注射组(含菌0.2×108个/mL)25 h开始出现症状,48 h内全部死亡,发病率和病死率均为100%;口服攻毒组(含菌2×108个/mL)90 h后开始有发病症状,第9天有1头死亡,发病率75%,病死率33%。从感染病死猪的肝脏、脾脏、肾脏、心血、大脑、脑脊液、淋巴结、肺脏和关节液中均分离到链球菌,经鉴定为试验攻毒的目的菌,表明猪体能够很好地用于猪链球菌2型动物感染模型,同时说明该菌侵害器官广泛,为进一步探讨该病的综合防制提供了重要技术依据。 相似文献
76.
Hlne Amory DVM PhD Dip. ECEIM Daniel Jean DMV MSc PhD Dip. ACVIM R. Leveille DVM Dip. ACVR Robert Higgins DVM MSc DSc Andr Vrins DVM 《Journal of Equine Veterinary Science》2006,26(8):364-369
Retropharyngeal infections in horses normally induce local painful swelling of the retropharyngeal area, which may lead to dyspnea, dysphagia, and systemic manifestations. Differential diagnosis of local painful swelling of the retropharyngeal area includes retropharyngeal lymph node infection, neoplasm, cellulitis, hematoma, guttural pouch empyema, parotiditis, and jugular thrombosis. Apart from Streptococcus equi ssp. equi, other bacteria are rarely reported as a cause of retropharyngeal abscesses. The reason for this might be a lack of specific sampling to identify the causative agent. This work deals with a case of retropharyngeal infection in an 11-year-old Standardbred stallion with acute depression, fever, tachycardia, asymmetric painful swelling in the throat area, ptyalism, and respiratory distress. Endoscopy, radiography, ultrasonography, blood analysis, and cytological examination of a puncture sample taken from the throat mass were consistent with a pyogenic to pyogranulomatous retropharyngeal inflammation. The clinical evolution was initially satisfactory in response to treatment with nonsteroidal anti-inflammatory drugs and antibiotics, but clinical signs relapsed twice, each time a few weeks after cessation of antibiotic therapy. The bacteriologic finding in this case was unusual and consisted of the isolation of a Pasteurella multocida strain that was obtained after the second relapse (ie, 79 days after initial admission), using a brain heart infusion (BHI) medium, and after two successive negative bacteriological cultures performed on day one of clinical signs and at the first relapse of clinical signs, respectively. 相似文献
77.
为初步了解水貂隐孢子虫病的流行情况,作者于2005年11月份用饱和蔗糖溶液漂浮法检查了河北省肃宁县某水貂养殖场的469份粪便样品。结果,8份粪便样品为隐孢子虫阳性,总感染率为1.71%(8/469)。其中,白貂感染率为2.15%(5/233)、灰貂感染率为2.08%(1/48)、黑貂感染率为1.06%(2/188)。所查的8份隐孢子虫阳性样品均来自5~6月龄的水貂,表明幼龄水貂容易感染隐孢子虫病而老龄水貂不易感染。另外,8份阳性样品多数来自雄性水貂,显示水貂的隐孢子虫感染可能存在性别的差异性。根据卵囊形态和大小将水貂隐孢子虫初步鉴定为小球隐孢子虫(Cryptosporidium parvum)。同时,利用所收集的隐孢子虫卵囊进行了小白鼠感染试验,结果表明水貂源隐孢子虫不感染免疫抑制状态下的昆明系小白鼠。 相似文献
78.
79.
B. -H. Li J. -R. Yang X. -L. Dong B. -D. Li X. -M. Xu 《European journal of plant pathology / European Foundation for Plant Pathology》2007,118(3):227-238
A dynamic model, called VenInf, was developed to forecast infection of pear leaves by conidia of Venturia nashicola. By simulating conidial infection processes following a rain event, the model estimates % conidia that successfully infected
leaves at the end of an infection period. The model is mainly derived from logistic models developed from recent laboratory
and glasshouse experimental results on infection of pear seedlings to estimate the rates of infection and mortality. It simulates
the conidial infection process at 5 min intervals using temperature, relative humidity (RH), surface wetness and rainfall
as input. The model was evaluated against pear scab in four unsprayed orchards in China over a 4-year period. In all orchards,
all significant disease increases were associated with infection periods predicted by the model. In one orchard, in 2004 the
incidence of leaf infection remained very low (<3%) during the entire season despite the model forecasting several severe
infection periods. Results of orchard evaluation suggest that the model is able to identify all important potential infection
periods. Thus, further field studies should be carried out to determine whether and how the model can be used in practice
to assist farmers in making decisions on fungicide applications. 相似文献
80.
Localized hemibiotrophy in Colletotrichum: cytological and molecular taxonomic similarities among C. destructivum, C. linicola and C. truncatum 总被引:1,自引:1,他引:1
The infection process of hemibiotrophic isolates of Colletotrichum linicola (from flax, Linum usitatissimum ) and C . truncatum (from broad bean, Vicia faba and lentil, Lens culinaris ) was studied by light microscopy. Host surfaces were penetrated directly leading to a symptomless, biotrophic phase characterized by the elaboration of large multilobed, multiseptate, vesicular primary hyphae that were restricted to the initially infected epidermal cells. Biotrophy lasted for the first 48 h of the host-pathogen interaction and was rapidly succeeded by a necrotrophic phase during which narrow, secondary hyphae invaded the surrounding leaf tissues and water-soaked spreading lesions with sporulating, monosetate acervuli were produced on infected host surfaces. Molecular taxonomic analysis of the nucleotide sequences of the amplified D2 and ITS-2 regions of rDNA revealed very close similarities (97–99%) between these isolates and those of C . destructivum obtained from cowpea ( Vigna unguiculata ) and lucerne ( Medicago sativa ), and also of C . truncatum obtained from pea ( Pisum sativum ). This association was consistent with results from a comparative assessment of some in-planta and in-vitro morphological and growth characteristics of these hemibiotrophic fungi. It was concluded that localized hemibiotrophy is an infection strategy utilized predominantly by a closely-related group of pathogens comprising C . destructivum , C . linicola and C. truncatum , and the formation of multilobed primary hyphae restricted to the first penetrated cell might therefore be a key taxonomic character which correlates consistently with ITS sequence data. 相似文献