全文获取类型
收费全文 | 1483篇 |
免费 | 114篇 |
国内免费 | 170篇 |
专业分类
林业 | 31篇 |
农学 | 153篇 |
基础科学 | 6篇 |
145篇 | |
综合类 | 391篇 |
农作物 | 166篇 |
水产渔业 | 152篇 |
畜牧兽医 | 458篇 |
园艺 | 123篇 |
植物保护 | 142篇 |
出版年
2024年 | 2篇 |
2023年 | 28篇 |
2022年 | 35篇 |
2021年 | 48篇 |
2020年 | 46篇 |
2019年 | 56篇 |
2018年 | 41篇 |
2017年 | 68篇 |
2016年 | 85篇 |
2015年 | 75篇 |
2014年 | 75篇 |
2013年 | 93篇 |
2012年 | 87篇 |
2011年 | 104篇 |
2010年 | 73篇 |
2009年 | 105篇 |
2008年 | 81篇 |
2007年 | 92篇 |
2006年 | 73篇 |
2005年 | 46篇 |
2004年 | 63篇 |
2003年 | 37篇 |
2002年 | 38篇 |
2001年 | 37篇 |
2000年 | 49篇 |
1999年 | 31篇 |
1998年 | 26篇 |
1997年 | 20篇 |
1996年 | 22篇 |
1995年 | 21篇 |
1994年 | 19篇 |
1993年 | 14篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 7篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 2篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1975年 | 2篇 |
1955年 | 1篇 |
排序方式: 共有1767条查询结果,搜索用时 31 毫秒
51.
M Natarajan V Udhayakumar K Krishnaraju V Muthukkaruppan 《Comparative immunology, microbiology and infectious diseases》1985,8(1):9-16
The humoral immune response to crude outer membrane proteins (comp) of S. typhimurium in mice has been characterized. Maximal and quicker antibody response was observed when 50 micrograms of comp was injected intraperitoneally. The comp of smooth C5 strain of S. typhimurium evoked antibody response to both lipopolysaccharide (LPS) and proteins. Absorption of these sera with LPS coated erythrocytes eliminated the antibodies to LPS completely, while the antibody level to protein was left unaltered. The comp from rough mutant (lacking O-specific chain of LPS) of S. typhimurium elicited antibodies to proteins but not to LPS. These results indicate the concomitant production of antibodies to Salmonella outer membrane proteins also. The significance of such antibodies in protection and diagnosis has been discussed. 相似文献
52.
53.
Low temperature is one of the major limiting environmental factors which constitutes the growth, development,productivity and distribution of plants. Over the past several years, the proteins and genes associated with freezing resistance of plants have been widely studied. The recent progress of domestic and foreign research on plant antifreeze proteins and the identification and characterization of plant antifreeze protein genes, especially on expression regulatory mechanism of plant antifreeze proteins are reviewed in this paper. Finally, some unsolved problems and the trend of research in physiological functions and gene expression regulatory mechanism of plant antifreeze proteins are discussed. 相似文献
54.
Dai Huanqin Lu Cunfu* Zhang Hui Zhang Xujia College of Biological Sciences Biotechnology Beijing Forestry University Beijing P. R. China Institute of Biophysics Chinese Academy of Sciences Beijing P. R. China 《中国林学(英文版)》2003,5(4)
Populus euphratica Olive is the only tree species that can grow in the saline land and also survive cold winters in northwest China, and it plays a very important role in stabilizing the vulnerable ecosystem there. A cell suspension culture was initiated from callus derived from plantlets of Populus euphratica. Cold acclimation was induced (LT50 of-17.5 ℃) in cell suspension at 4-5 ℃ in the dark for 30 days and the freezing tolerance increased from LT50 of-12.5 ℃ in nonacclimated cells to LT50 of-17.5 ℃ in cold-acclimated cells. Microvacuolation, cytoplasmic augmentation and accumulation of starch granules were observed in cells that were cold-acclimated by exposure to low temperatures. Several qualitative and quantitative changes in proteins were noted during cold acclimation. Antibodies to carrot extracellular (apoplastic) 36 kD antifreeze protein did not cross react on immunoelectroblots with extracellular proteins in cell suspension culture medium of Populus euphratica, indicating no common epitopes in the carrot 36 kD antifreeze protein and P euphratica extracellular proteins. The relationship of these changes to cold acclimation in Populus euphratica cell cultures was discussed. 相似文献
55.
以日本无刺楤木(Aralia elatavar.inerm is)休眠枝条离体茎段促生芽为试验材料,对芽体内可溶性蛋白、维生素C和可溶性糖含量进行了比较分析。试验分为5个处理组:不同茎段长度的产芽试验、不同茎段直径的产芽试验、不同茎段年龄的产芽试验,相同茎段不同营养条件下的产芽试验和同一茎段不同芽位的产芽试验。结果表明:(1)离体茎段长度为20 cm时,促生芽可溶性蛋白含量和维生素C含量最高,与其他长度处理差异极显著,可溶性糖含量差异不显著。(2)不同培养条件下,芽体内的3种营养成分差异均不显著。(3)不同直径处理组中,芽体内3种营养成分含量均存在极显著差异。直径为5.8 mm时可溶性蛋白和维生纱C含量最高,直径为8.8 mm时可溶性糖含量最高。(4)2年生茎段促生芽的可溶性蛋白、维生素C和可溶性糖含量均高于1年生茎段。(5)同一茎段不同芽位的促生芽,以下位芽3种营养成分含量为最高。 相似文献
56.
《Veterinary immunology and immunopathology》2015,163(1-2):46-56
Our objective was to develop a lipopolysaccharide (LPS) inflammation model in calves to evaluate the acute-phase response with respect to the release of pro-inflammatory cytokines and acute-phase proteins, fever development and sickness behaviour. Fourteen 4-week-old male Holstein Friesian calves were included and randomly assigned to a negative control group (n = 3) and an LPS-challenged group (n = 11). The latter received an intravenous bolus injection of 0.5 μg of LPS/kg body weight. Blood collection and clinical scoring were performed at 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 8, 12, 18, 24, 28, 32, 48, 54 and 72 h post LPS administration (p.a.). In the LPS group, the following clinical signs were observed successively: tachypnoea (on average 18 min p.a.), decubitus (29 min p.a.), general depression (1.75 h p.a.), fever (5 h p.a.) and tachycardia (5 h p.a.). Subsequent to the recovery from respiratory distress, general depression was prominent, which deteriorated when fever increased. One animal did not survive LPS administration, whereas the other animals recovered on average within 6.1 h p.a. Moreover, the challenge significantly increased plasma concentrations of tumour necrosis factor-α, interleukin 6, serum amyloid A and haptoglobin, with peaking levels at 1, 3.5, 24 and 18 h p.a., respectively. The present LPS model was practical and reproducible, caused obvious clinical signs related to endotoxemia and a marked change in the studied inflammatory mediators, making it a suitable model to study the immunomodulatory properties of drugs in future research. 相似文献
57.
Sydney Mukaratirwa Claudio Petterino Alys Bradley 《Journal of toxicologic pathology》2015,28(3):177-180
A single mass was found on the left submandibular salivary gland at necropsy of a 15-month-old male commercially bred laboratory Beagle dog from a control dose group from a repeat toxicity study. Microscopically, the mass was composed of a well-demarcated area of coagulative necrosis surrounded and separated from the normal salivary gland tissue by a thick fibrovascular capsule. Necrosis was admixed with areas of hemorrhage, fibrin, edema, fibrinoid necrosis of the vascular tunica media, and thrombosis of small and large vessels. Within the necrotic tissue, there was marked ductal hyperplasia, and squamous metaplasia of duct and acinar epithelium. The mass was diagnosed as necrotizing sialometaplasia of the submandibular gland. Hyperplastic ductal elements and squamous metaplasia can be mistaken microscopically with squamous cell carcinoma. Therefore, pathologists should be aware of this lesion as to avoid errors in the diagnosis of this benign pathologic condition. 相似文献
58.
Proteomic analysis of pathogen-responsive proteins from maize stem apoplast triggered by Fusarium verticillioides 下载免费PDF全文
During the attack of a pathogen, a variety of defense-associated proteins are released by the host plant in the apoplast to impede the perceived attack. This study utilized the mass spectrometry (LC-MS/MS) and label-free quantification method to analyze the apoplastic fluid (APF) from maize stalk and identified the proteins responsive to the Fusarium verticillioides infection. We have identified 742 proteins, and among these, 119 proteins were differentially accumulated (DAPs), i.e., 35 up-regulated, 18 down-regulated, and 66 proteins were only induced by the pathogen infection. The differentially accumulated proteins were analyzed for their Gene Ontology (GO) and Kyoto Encyclopedia of Gene and Genomes (KEGG) pathway enrichment. The highly enriched Biological Process (BP) term was the L-serine biosynthesis process, whereas the most enriched Molecular Function (MF) term was the cysteine-type endopeptidase inhibitor activity. It was also found that the pathways related to the biosynthesis of amino acid, biosynthesis of secondary metabolites, protein processing in the endoplasmic reticulum, and carbohydrate metabolic pathways were significantly enriched. Moreover, 61 out of 119 differentially accumulated proteins were predicted as secretory proteins. The secretory pathways analysis showed that a greater number of proteins were secreted through the conventional secretion system compared to the unconventional secretion system. The identified secreted proteins were related to a variety of pathways in defense responses including cell redox homeostasis, cell wall modification, signal transduction, carbohydrate metabolism, binding proteins (metal ion binding, RNA binding and heme-binding), maintenance and stabilization of other proteins, indicating a complex response from the plant to the fungal infection. Our data suggested that a number of host proteins belonging to various pathways have been modulated in the apoplastic region. 相似文献
59.
Strategies for further development of aquatic feeds 总被引:4,自引:1,他引:4
ABSTRACT: To date, aquatic feeds have depended heavily on fishmeal and fish oil as their source of protein and lipid. However, the feed industry is encountering shortfalls in the availability of these ingredients because of a decline in the number of fish captured in the wild and the increased human demand for some of the species currently being used for fishmeal and oil production. Therefore, efforts are now being directed in different parts of the world to finding alternative quality ingredients, which ideally are less expensive and readily available for use in practical diets. The data accrued have shown that a large proportion of both fishmeal and fish oil can be replaced by other protein and lipid sources. However, it is emphasized that an optimal essential amino acid balance be maintained and that the n-3 highly unsaturated fatty acid requirement be satisfied when combining economical protein and lipid ingredients. Newly developed feeds should aim at being nutrient-dense in order to reduce the output of solid, P and N waste. This can be done through improving nutrient availability, optimizing the digestible protein to energy balance of the diet, and replacing dietary fishmeal with alternate ingredients. These diets should also be effective for maintaining good health and improving disease resistance in fish through enhancement of immune responses. A wholesome approach to culturing fish would be to use appropriate feeding standards that are aimed not only at improving economic returns but also at developing a lasting cohabitation of sustainable aquaculture and a cleaner environment. Furthermore, in the 2lst century aquaculture would still retain its place as a prominent source of food protein, signifying that fish feed research remains a forceful area in discovering better feeds for the industry. 相似文献
60.
J.I. LEENHOUWERS D. ADJEI-BOATENG J.A.J. VERRETH & J.W. SCHRAMA 《Aquaculture Nutrition》2006,12(2):111-116
The objective of the present study was to investigate if dietary soluble non‐starch polysaccharides (NSP) increase digesta viscosity, reduce nutrient digestibility and increase organ weights in African catfish. The fish (mean weight 80 g) were fed diets supplemented with the soluble NSP guar gum at three levels, 0 g kg?1 (GG0), 40 g kg?1 (GG4) and 80 g kg?1 (GG8). Guar gum inclusion significantly increased digesta viscosity in the proximal (GG0: 1.7 centipoise or cP; GG4: 84.9 cP; GG8: 98.3 cP) and distal (GG0: 1.9 cP; GG4: 109.8 cP; GG8: 66.4 cP) intestine. Apparent digestibility coefficients (ADC) were significantly lower for the GG8 diet than the GG0 diet (dry matter: 52% versus 69%; protein: 77% versus 90%; ash: 41% versus 54%; energy: 60% versus 77%). The ADC of dry matter and energy were significantly lower for the GG4 diet than the GG0 diet. The relative growth rate of metabolic weight (14.5–15.4 g kg?0.8 day?1) and feed conversion ratio (0.8) did not differ between diets. Fish fed the GG8 diet had a significantly higher somatic stomach index than GG0 fish (0.71% versus 0.65% body weight). The intestinal somatic index tended to increase with increasing guar gum supplementation (GG0: 1.08%; GG4: 1.23%; GG8: 1.59%). In conclusion, high digesta viscosities in the guar gum fed fish may explain the observed reduced nutrient digestibilities and increases in digestive organ weights. 相似文献