全文获取类型
收费全文 | 235757篇 |
免费 | 14000篇 |
国内免费 | 659篇 |
专业分类
林业 | 23306篇 |
农学 | 13952篇 |
基础科学 | 2952篇 |
41517篇 | |
综合类 | 15973篇 |
农作物 | 17160篇 |
水产渔业 | 16501篇 |
畜牧兽医 | 89593篇 |
园艺 | 6230篇 |
植物保护 | 23232篇 |
出版年
2021年 | 2454篇 |
2020年 | 2826篇 |
2019年 | 3622篇 |
2018年 | 3874篇 |
2017年 | 4196篇 |
2016年 | 4688篇 |
2015年 | 4283篇 |
2014年 | 5617篇 |
2013年 | 16224篇 |
2012年 | 5792篇 |
2011年 | 7601篇 |
2010年 | 7179篇 |
2009年 | 7760篇 |
2008年 | 6932篇 |
2007年 | 6014篇 |
2006年 | 6694篇 |
2005年 | 5913篇 |
2004年 | 5772篇 |
2003年 | 5511篇 |
2002年 | 4877篇 |
2001年 | 5666篇 |
2000年 | 5269篇 |
1999年 | 5009篇 |
1998年 | 4089篇 |
1997年 | 4131篇 |
1996年 | 3876篇 |
1995年 | 4395篇 |
1994年 | 3786篇 |
1993年 | 3511篇 |
1992年 | 3963篇 |
1991年 | 4224篇 |
1990年 | 3914篇 |
1989年 | 3845篇 |
1988年 | 3404篇 |
1987年 | 3450篇 |
1986年 | 3254篇 |
1985年 | 3616篇 |
1984年 | 3432篇 |
1983年 | 3199篇 |
1982年 | 2722篇 |
1981年 | 2644篇 |
1980年 | 2605篇 |
1979年 | 2927篇 |
1978年 | 2630篇 |
1977年 | 2447篇 |
1976年 | 2320篇 |
1975年 | 2130篇 |
1974年 | 2235篇 |
1973年 | 2180篇 |
1971年 | 1926篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
Ana M. Casas Carlota R. Gazulla Arantxa Monteagudo Carlos P. Cantalapiedra Marian Moralejo M. Pilar Gracia Francisco J. Ciudad William T.B. Thomas José L. Molina-Cano Scott Boden Bruno Contreras-Moreira Ernesto Igartua 《作物学报(英文版)》2021,(4):862-872
Response to vernalization and photoperiod are the main determinants controlling the time to flowering in temperate cereals. While the individual genes that dete... 相似文献
962.
963.
964.
Juan A. García Mauricio A. Navarro Karina Fresneda Francisco A. Uzal 《Journal of veterinary diagnostic investigation》2022,34(3):421
Tyzzer disease (TD) is caused by Clostridium piliforme, a gram-negative and obligate intracellular bacterium. The disease occurs in multiple species. A triad of lesions, namely colitis, hepatitis, and myocarditis, is described in cases of TD in some species, such as rats and mice. We carried out a retrospective analysis of 25 equine cases with a diagnosis of TD; 24 of 25 cases occurred in foals <45 d old; the remaining foal was 90 d old. There were 12 males and 12 females; no sex information was available for one foal. The affected breeds were Quarter Horse, Thoroughbred, Arabian, Paint, and Hanoverian. Most of the cases (19 of 25) occurred in the spring. There were 9 cases of sudden death; the remaining animals had diarrhea, fever, distended abdomen, depression, weakness, non-responsiveness, and/or recumbency. Gross findings included icterus, hepatomegaly with acinar pattern, serosal hemorrhages, pulmonary edema, and/or fluid content in small and large intestine. Microscopically, all foals had severe, multifocal, necrotizing hepatitis. Necrotizing lymphohistiocytic colitis was observed in 10 of 25 foals, and multifocal necrotizing myocarditis was found in 8 of 25. Gram-negative, Steiner-positive, intracytoplasmic filamentous bacteria were observed in hepatocytes, enterocytes, and myocardiocytes, respectively. PCR detected C. piliforme DNA in the liver (24 of 24), colon (20 of 24), and heart (5 of 25). Our results indicate that necrotic hepatitis is the hallmark of TD in horses; the so-called triad of lesions is not a consistent characteristic of the disease in this species. 相似文献
965.
Rebecca Windsor Samuel Stewart Jessica Schmidt Mario Mosqueda Ignazio Piras Stefan M. Keller Briana Steinmetz Dori L. Borjesson Matthew Huentelman Chand Khanna 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2022,36(4):1382
BackgroundNecrotizing meningoencephalitis (NME) in the pug dogs is a fatal neuroinflammatory disease associated with rapid progression and poor response to conventional immunosuppressive therapy. Diagnosis is typically made after severe neurological abnormalities have manifested.Hypothesis/ObjectivePug dogs at genetic risk for NME might manifest neurological abnormalities before developing pathognomonic clinical signs of NME.AnimalsThirty‐six pug dogs less than 4 years of age asymptomatic for NME.MethodsProspective observational cohort study with germline genome‐wide genotyping. Neurological examinations were performed 4 weeks apart to document reproducible findings of central nervous system disease. Magnetic resonance imaging, cerebrospinal fluid analysis, and testing for infectious diseases were performed in all pugs with reproducible abnormalities detected on neurological examination.ResultsThe overall risk allele frequency in this cohort was 40%; 5 (14%) dogs were high risk, 19 (53%) dogs were medium risk, and 12 (33%) dogs were low genetic risk for NME. Reproducible abnormalities detected on neurological examination were identified in 8/24 (33%) genetically at‐risk dogs and 0/12 (0%) low risk dogs. Clinical abnormalities included multifocal spinal pain in 8/8, reduced menace response in 5/8, and lateralizing postural reaction deficits in 5/8 pugs. There was a strong association between genotype risk and the presence of this clinical phenotype (P = .03).Conclusions and Clinical ImportanceOur findings suggest the presence of a novel early clinical phenotype of NME in apparently asymptomatic genetically at‐risk pugs which might be used to plan early diagnostic and therapeutic clinical trials. 相似文献
966.
以AA肉鸡和皖江黄鸡(公鸡)为对象,探讨了日粮中添加150 mg/kg、250 mg/kg、350 mg/kg的姜黄素对其体脂沉积的影响及作用机理。结果显示,添加250 mg/kg、350 mg/kg姜黄素显著地降低了AA肉鸡和皖江黄鸡腹脂率(P〈0.05)、肝脂率(P〈0.05),皮下脂肪厚度(P〈0.05);腹脂中激素敏感脂酶活性增强(P〈0.05),苹果酸脱氢酶活性降低(P〈0.05);肝脏中PPARαmRNA水平呈增加的趋势(P〉0.05),PPARγ和MDH mRNA水平呈降低的趋势(P〉0.05)。上述结果提示姜黄素可能通过调控PPARα、PPARγ、MDHmRNA表达来影响肉鸡脂肪的沉积。 相似文献
967.
968.
969.
Utilization of organic nitrogen (N) is an important aspect of plant N assimilation and has potential application in sustainable agriculture. The aim of this study was to investigate the plant growth, C and N accumulation in leaves and roots of tomato seedlings in response to inorganic (NH4^+-N, NO3^-N) and organic nitrogen (Gly-N). Different forms of nitrogen (NH4^+-N, NO3^--N, Gly-N) were supplied to two tomato cultivars (Shenfen 918 and Huying 932) using a hydroponics system. The plant dry biomass, chlorophyll content, root activity, total carbon and nitrogen content in roots and leaves, and total N absorption, etc. were assayed during the cultivation. Our results showed that no significant differences in plant height, dry biomass, and total N content were found within the first 16 d among three treatments; however, significant differences in treatments on 24 d and 32 d were observed, and the order was NO3^--N 〉 Gly-N 〉 NH4^+-N. Significant differences were also observed between the two tomato cultivars. Chlorophyll contents in the two cultivars were significantly increased by the Gly-N treatment, and root activity showed a significant decrease in NHa^+-N treatment. Tomato leaf total carbon content was slightly affected by different N forms; however, total carbon in root and total nitrogen in root and leaf were promoted significantly by inorganic and organic N. Among the applied N forms, the increasing effects of the NH4^+-N treatment were larger than that of the Gly-N. In a word, different N resources resulted in different physiological effects in tomatoes. Organic nitrogen (e.g., Gly-N) can be a proper resource of plant N nutrition. Tomatoes of different genotypes had different responses under organic nitrogen (e.g., Gly-N) supplies. 相似文献
970.