全文获取类型
收费全文 | 66567篇 |
免费 | 17418篇 |
国内免费 | 28303篇 |
专业分类
林业 | 7352篇 |
农学 | 6650篇 |
基础科学 | 8151篇 |
33964篇 | |
综合类 | 28625篇 |
农作物 | 5938篇 |
水产渔业 | 5869篇 |
畜牧兽医 | 7272篇 |
园艺 | 2364篇 |
植物保护 | 6103篇 |
出版年
2024年 | 978篇 |
2023年 | 1002篇 |
2022年 | 1230篇 |
2021年 | 1085篇 |
2020年 | 2712篇 |
2019年 | 6166篇 |
2018年 | 5974篇 |
2017年 | 6728篇 |
2016年 | 7579篇 |
2015年 | 7595篇 |
2014年 | 6605篇 |
2013年 | 6885篇 |
2012年 | 6672篇 |
2011年 | 5583篇 |
2010年 | 4543篇 |
2009年 | 4071篇 |
2008年 | 3026篇 |
2007年 | 3127篇 |
2006年 | 2805篇 |
2005年 | 2531篇 |
2004年 | 2541篇 |
2003年 | 2270篇 |
2002年 | 1965篇 |
2001年 | 1591篇 |
2000年 | 1326篇 |
1999年 | 1331篇 |
1998年 | 1242篇 |
1997年 | 1243篇 |
1996年 | 1101篇 |
1995年 | 1156篇 |
1994年 | 1145篇 |
1993年 | 904篇 |
1992年 | 923篇 |
1991年 | 776篇 |
1990年 | 598篇 |
1989年 | 590篇 |
1988年 | 530篇 |
1987年 | 388篇 |
1986年 | 397篇 |
1985年 | 211篇 |
1984年 | 196篇 |
1983年 | 190篇 |
1982年 | 190篇 |
1981年 | 230篇 |
1980年 | 192篇 |
1979年 | 150篇 |
1978年 | 130篇 |
1975年 | 109篇 |
1965年 | 137篇 |
1964年 | 140篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
江西省萍乡市某羊场布鲁菌病的流行病学分析 《畜牧与饲料科学》2018,39(11):110-112
江西省萍乡市某山羊场妊娠母羊散发流产,为了分析该羊场流产的发生是否与布鲁菌感染有关,同时掌握该羊场布鲁菌病的流行情况,随机抽样采血共分离得到100份山羊血清,首先使用虎红平板凝集试验进行初步鉴定,然后通过试管凝集试验重新检测阳性血清。结果表明,该羊场布鲁菌病阳性率为20%。由此可以得出,该羊场的布鲁菌病防控工作存在较严重的问题,应制定有效的防治措施,将山羊布鲁菌病的检测纳入日常疾病监测工作中,最终达到净化该病的目的。 相似文献
102.
Treatment of healthy dogs with the butyrophenone derivative, lenperone hydrochloride, at two different doses significantly decreased gastroesophageal sphincter pressure (GESP). No dose-related effect was identified. Individual variation in the response to lenperone hydrochloride was noted which was consistent on a day-to-day basis. Lenperone hydrochloride is unsuitable for chemical restraint of dogs undergoing esophageal manometry because it decreases GESP and because the magnitude of the decrease varies considerably between dogs. 相似文献
103.
Sophie Blani�� J��r��my Mortier Maxence Delverdier St��phane Bertagnoli Christelle Camus-Bouclainville 《Veterinary research》2009,40(1)
Myxoma virus (MYXV), a member of the Poxviridae family, is the agent responsible for myxomatosis, a fatal disease in the European rabbit (Oryctolagus cuniculus). MYXV has a linear double-stranded DNA genome that encodes several factors important for evasion from the host immune system. Among them, four ankyrin (ANK) repeat proteins were identified: M148R, M149R, M150R and M-T5. To date, only M150R and M-T5 were studied and characterized as critical virulence factors. This article presents the first characterization of M148R and M149R. Green Fluorescent Protein (GFP) fusions allowed us to localize them in a viral context. Whereas M149R is only cytoplasmic, interestingly, M148R is in part located in the nucleolus, a unique feature for an ANK repeat poxviral protein. In order to evaluate their implication in viral pathogenicity, targeted M148R, M149R, or both deletions were constructed in the wild type T1 strain of myxoma virus. In vitro infection of rabbit and primate cultured cells as well as primary rabbit cells allowed us to conclude that M148R and M149R are not likely to be implicated in cell tropism or host range functions. However, in vivo experiments revealed that they are virulence factors since after infection of European rabbits with mutant viruses, a delay in the onset of clinical signs, an increase of survival time and a dramatic decrease in mortality rate were observed. Moreover, histological analysis suggests that M148R plays a role in the subversion of host inflammatory response by MYXV. 相似文献
104.
An ontogenetic study was designed on developing rats in uterus of mothers tryptophan deprived at day 1 (exp. 1) and day 14.5 (exp. 2) of conception to verify the supposed determining role of the serotoninergic system (SS) in sexual differentiation in mammals. Tryptophan-free feeding was pursued uninterruptedly in the litter after birth, during lactation and post-natal development. Tryptophan-free pregnant rats were obtained by exclusion of tryptophan sources from chow. In both exp. 1 and exp. 2, the litter showed at birth a significant physical under evolution that worsened, during post-natal development, to a much more marked dwarfism in exp. 1 pups. Growth hormone concentrations in both sexes of dwarf rats were lower than that in the control rats. At 30 days post-natal age, whereas exp. 1 female rats showed a right-timed onset of puberty, no descensus of testes could be observed in male rats of same experiment. Dwarf male rats showed an evident hypotrophy of the whole reproductive apparatus. In histological examination of testes, neither spermatogenesis nor Leydig cells have been observed. Moreover, dwarf female rats showed a pronounced hypotrophy of reproductive organs, but a normal puberal status pattern was evident. In exp. 2, litters showed a less pronounced dwarfism, but a normal right-timed onset of puberty in both male and female rats. Data indicate that role of tryptophan in physical and sexual maturation in both male and female rats is essential. 相似文献
105.
The aim of this study was to determine the developmental anatomy of intrinsic cardiac ganglia with respect to epicardiac ganglionated nerve plexus in the human fetuses at different gestation stages. Twenty fetal hearts were investigated applying a technique of histochemistry for acetylcholinesterase to visualize the epicardiac neural ganglionated plexus with its subsequent examinations on total (non-sectioned) hearts. Most epicardiac ganglia embodied multilayered neurons and were oval in shape, but some ganglia involved neurons lying in one layer or had the irregular appearance because of their extensions along inter-ganglionic nerves. The mean ganglion area of fetuses at gestation stages of 15–40 weeks was 0.03 ± 0.008 mm2 . The largest epicardiac ganglia, reaching in area 0.4 mm2 , were concentrated on the dorsal surface of both atria. The particular fused or "dual" ganglia were identified at the gestation stages of 23–40 weeks, but they composed only 2.3 ± 0.7% of all found epicardiac ganglia. A direct positive correlation was determined between the fetal age and the ganglion area (mm2 ) as well as between the fetal age and the number of inter-ganglionic nerves. The revealed appearance of epicardiac ganglia in the human fetuses at 15–40 weeks of gestation confirms their prenatal development and presumable intrinsic remodelling. 相似文献
106.
107.
108.
109.
110.
2018年8月开始,非洲猪瘟在我国快速多点发生,该病是高度接触性传染性疾病,目前无有效的疫苗和药物控制,各大公司和养殖户开始了猪场生物安全体系的升级改造。两年后我国大部分猪场的成功复产,全国生猪出栏量的大幅提升,证明了生物安全措施巨大效力;同时在严格的生物安全措施下创新了精准剔除、快速复产等操作,进一步证明了生物安全措施的有效作用。文章主要介绍猪场生物安全体系中入口(大门)和出口(后门)最为关键防线处的通道设计,方便所有的生物安全操作能够高效落实,切断病原轻易进出猪场的途径。 相似文献