全文获取类型
收费全文 | 6117篇 |
免费 | 523篇 |
国内免费 | 530篇 |
专业分类
林业 | 136篇 |
农学 | 178篇 |
基础科学 | 285篇 |
781篇 | |
综合类 | 2387篇 |
农作物 | 119篇 |
水产渔业 | 309篇 |
畜牧兽医 | 2750篇 |
园艺 | 54篇 |
植物保护 | 171篇 |
出版年
2024年 | 90篇 |
2023年 | 155篇 |
2022年 | 200篇 |
2021年 | 350篇 |
2020年 | 283篇 |
2019年 | 346篇 |
2018年 | 160篇 |
2017年 | 251篇 |
2016年 | 270篇 |
2015年 | 246篇 |
2014年 | 317篇 |
2013年 | 380篇 |
2012年 | 440篇 |
2011年 | 410篇 |
2010年 | 313篇 |
2009年 | 357篇 |
2008年 | 280篇 |
2007年 | 378篇 |
2006年 | 284篇 |
2005年 | 249篇 |
2004年 | 203篇 |
2003年 | 176篇 |
2002年 | 143篇 |
2001年 | 129篇 |
2000年 | 113篇 |
1999年 | 94篇 |
1998年 | 64篇 |
1997年 | 61篇 |
1996年 | 51篇 |
1995年 | 52篇 |
1994年 | 49篇 |
1993年 | 45篇 |
1992年 | 42篇 |
1991年 | 35篇 |
1990年 | 33篇 |
1989年 | 34篇 |
1988年 | 21篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 2篇 |
1982年 | 5篇 |
1980年 | 2篇 |
1979年 | 7篇 |
1978年 | 5篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 8篇 |
1973年 | 2篇 |
1956年 | 5篇 |
排序方式: 共有7170条查询结果,搜索用时 15 毫秒
11.
在非洲猪瘟防控新形势下,各猪场都高度重视生物安全,对生物安全风险防范工作提出了新的要求。在这种情况下,过去生猪保险查勘定损中的一些传统做法已经不能适应新形势,出现了猪场封闭式管理和查勘定损工作相冲突,病死猪理赔监督不到位、死亡原因不明、处理不及时以及部分查勘员生物安全意识淡薄等现象。对此,有关部门和机构应加强生物安全培训,采用网络和电子化等手段变革传统工作方式,在保险机构和畜牧兽医部门间加强联动和信息共享,把查勘定损、无害化处理和疫病监测溯源工作有机结合,把生物安全风险降到最低。 相似文献
12.
13.
14.
研究Na+,K+-ATP酶与小型猪复合麻醉剂全麻作用的关系,以判断该酶是否为该制剂作用的靶位之一.试验选取84只SD大鼠,先随机抽取12只为对照组,其余随机均分为高剂量小型猪复合麻醉剂组(腹腔注射(ip) 7.5 mg/kg)和低剂量小型猪复合麻醉剂组(5mg/kg),每个剂量组又随机均分为麻醉组、恢复Ⅰ组和恢复Ⅱ组等3个亚组.对照组注射生理盐水10 mL/kg,5 min后断头取材;麻醉组、恢复Ⅰ组和恢复Ⅱ组分别在翻正反射消失即刻、翻正反射恢复即刻和大鼠可直线爬行后断头取材.迅速分离双侧大脑皮层、海马、小脑、脑干、丘脑,立即液氮冷冻.制备脑粗突触体,采用比色法测定Na+,K+-ATP酶活性.结果表明:2个剂量麻醉组大脑皮层、脑干和丘脑突触体Na+,K+-ATP酶活性受到明显抑制(P<0.01或P<0.05),高剂量组小脑该酶也发生明显变化(P<0.05).在恢复期上述脑区的该酶活性呈现不同程度恢复,与对照组相比,差异不显著(P>0.05),海马在2剂量组未发生明显的变化.小型猪复合麻醉剂的全麻作用与抑制小脑和丘脑突触体Na+,K+-ATP酶活性相关,说明此酶可能是小型猪复合麻醉剂全麻作用的靶位之一. 相似文献
15.
The fine structure of the pig cornea in normal conditions and after being used in a perfusion apparatus, for 4 h, is described. Earlier reports on the normal morphology of the pig cornea were partly not confirmed. Thus the number of cell layers in the epithelium was found to be 19-23 (a basal cell layer, 4–5 polyhedral cell layers and 14–17 squamous cell layers) compared to earlier reported 6–9 layers.The mean thickness of normal and perfused corneas were 722 μm and 752 μm respectively. Normal corneas had a hydration level of 77.2 % and after perfusion 78.5 %. The normal morphology and morphological changes due to exposure to perfusion were studied by light and electron microscopy. The differences observed between normal and perfused corneas have to be considered limited, and restricted mainly to the anterior squamous epithelium and the endothelium.Taken together our results indicate that the corneas used in the apparatus still had functional integrity. 相似文献
16.
17.
Shima E. Abdalla Akebe L.K. Abia Daniel G. Amoako Keith Perrett Linda A. Bester Sabiha Y. Essack 《The Onderstepoort journal of veterinary research》2022,89(1)
BackgroundDiarrheagenic E. coli (DEC) strains are a major cause of diarrheal diseases in both developed and developing countries. Healthy asymptomatic animals may be reservoirs of zoonotic DEC, which may enter the food chain via the weak points in hygiene practices.AimWe investigated the prevalence of DEC along the pig production continuum from farm-to-fork.MethodsA total of 417 samples were collected from specific points along the pig production system, that is, farm, transport, abattoir and food. E. coli was isolated and enumerated using Colilert. Ten isolates from each Quanti-tray were selected randomly and phenotypically identified using eosin methylene blue agar selective media. Real-time polymerase chain reaction (PCR) was used to confirm the species and to classify them into the various diarrheagenic pathotypes. Antimicrobial susceptibility was determined against a panel of 20 antibiotics using the Kirby-Bauer disk diffusion method and EUCAST guideline.ResultsThe final sample size consisted of 1044 isolates, of which 45.40% (474/1044) were DEC and 73% (762/1044) were multidrug-resistant. Enteroinvasive E. coli (EIEC) was the most predominant DEC at all the sampling sites.ConclusionThe presence of DEC in food animal production environments and food of animal origin could serve as reservoirs for transmitting these bacteria to humans, especially in occupationally exposed workers and via food. Adherence to good hygienic practices along the pig production continuum is essential for mitigating the risk of transmission and infection, and ensuring food safety. 相似文献
18.
The Rwandan farmers, faced with a perpetual land shortage, have evolved certain intensive systems of organic agriculture. These systems, particularly the homestead (compound) farming, involve the combination of food, fodder and tree crops. to a certain extent these systems can satisfy the multiple needs of the subsistence farmers living under several risks and constraints. However, they cannot cope with the expanding food demand of the rapidly increasing population. Some multipurpose, low-input technologies and agroforestry approaches have been designed to improve the productivity of these traditional systems; these include inter/mixed cropping systems and rotations, alley cropping with leguminous trees and shrubs, use of planted fallow, planting tree legumes on anti-erosive lines, mixed farming,community forestry and woodlots, and tree planting on farm/field boundaries. The essential aspects of these technologies are briefly discussed.ISAR-IITA FSR PROJECT, B.P. 629, Kigali RwandaISAR-Swiss Intercooperation, c/o Forestry Department, B.P. 617, Butare, Rwanda 相似文献
19.
Kerstin Müller Elisabeth Müller Ruth Klein Leo Brunnberg 《Veterinary clinical pathology / American Society for Veterinary Clinical Pathology》2009,38(4):507-510
Background: Guinea pigs (Cavia porcellus) are often presented as patients in veterinary practice. Nevertheless, only limited information is available about endocrine diseases or thyroxine reference values for the species. Objective: The aim of this study was to determine serum thyroxine concentrations in a well‐defined population of clinically healthy pet guinea pigs. Methods: Between October 2007 and July 2008, serum samples were collected from 40 clinically healthy guinea pigs of different sexes, ages, and breeds that were presented to our clinic for a general health check or for castration. Pregnant females were excluded from the study. Thyroxine concentration was measured using a chemiluminescence test (Immulite 2000 Canine Total T4). Results: Thyroxine concentrations ranged from 14.2 to 66.9 nmol/L (1.1–5.2 μg/dL) with a median value of 27.0 nmol/L (2.1 μg/dL). Females (n=16) had significantly (P=.039; Mann–Whitney U‐test) lower thyroxine values than castrated males (n=8), whereas no differences were found between females and intact males (n=16) or between intact and castrated males. No significant correlation was found between thyroxine concentration and age. Conclusion: This is the first report of serum thyroxine reference values for a well‐defined population of healthy pet guinea pigs as measured by a chemiluminescence assay. The results were higher than those previously reported for this species and emphasize the importance of using appropriate reference intervals for the diagnosis of hyperthyroidism. 相似文献
20.
榆次区在社会主义新农村建设中,一是做到了领导到位、资金到位、帮扶到位、督查到位;二是充分发挥区域比较优势,将具有地方特色和市场潜力的产品和产业作为发展重点,集中精力定位主导产业;三是不断提升农业服务体系功能,使其成为推进农业产业化水平的"保护伞"和"助推器";四是突出打造亮点工程、精品工程,整体带动新农村建设的发展;五是着力改善农村生产、生活、生态、社会环境,整体推动新农村建设。通过上述措施,使农业主导产业壮大提升,农村村容村貌大为改观,农民收入稳步持续提高,全区新农村建设呈现出又好又快发展的良好态势。 相似文献