全文获取类型
收费全文 | 84931篇 |
免费 | 3823篇 |
国内免费 | 9316篇 |
专业分类
林业 | 9313篇 |
农学 | 12195篇 |
基础科学 | 7093篇 |
13170篇 | |
综合类 | 28124篇 |
农作物 | 4648篇 |
水产渔业 | 2938篇 |
畜牧兽医 | 11686篇 |
园艺 | 3522篇 |
植物保护 | 5381篇 |
出版年
2024年 | 255篇 |
2023年 | 982篇 |
2022年 | 2373篇 |
2021年 | 3331篇 |
2020年 | 2912篇 |
2019年 | 2941篇 |
2018年 | 2111篇 |
2017年 | 3005篇 |
2016年 | 2782篇 |
2015年 | 3893篇 |
2014年 | 3770篇 |
2013年 | 4511篇 |
2012年 | 5576篇 |
2011年 | 5961篇 |
2010年 | 5925篇 |
2009年 | 5430篇 |
2008年 | 5006篇 |
2007年 | 5143篇 |
2006年 | 4805篇 |
2005年 | 4231篇 |
2004年 | 2054篇 |
2003年 | 1954篇 |
2002年 | 1705篇 |
2001年 | 1699篇 |
2000年 | 1750篇 |
1999年 | 1965篇 |
1998年 | 1714篇 |
1997年 | 1545篇 |
1996年 | 1407篇 |
1995年 | 1268篇 |
1994年 | 1086篇 |
1993年 | 1115篇 |
1992年 | 875篇 |
1991年 | 737篇 |
1990年 | 624篇 |
1989年 | 499篇 |
1988年 | 385篇 |
1987年 | 229篇 |
1986年 | 127篇 |
1985年 | 66篇 |
1984年 | 45篇 |
1983年 | 40篇 |
1982年 | 49篇 |
1981年 | 48篇 |
1980年 | 32篇 |
1979年 | 14篇 |
1965年 | 15篇 |
1964年 | 11篇 |
1963年 | 12篇 |
1956年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
RFamide‐related peptide‐3 (RFRP‐3), the mammalian ortholog of gonadotropin‐inhibiting hormone, has been implicated as a mediator between reproduction and energy balance. This study aimed to investigate the physiological effects of RFRP‐3 on the process of ovarian development in food‐restricted pre‐pubertal ewes. The results showed that food restriction significantly inhibited the ovarian development and follicular growth. The data of qPCR in the hypothalamic–pituitary–ovarian (HPO) axis showed that food restriction not only upregulated RFRP‐3 mRNA expression but also downregulated the mRNA expression of gonadotropin‐releasing‐hormone receptor, follicle‐stimulating hormone receptor and luteinizing hormone receptor (LHR). Immunohistochemistry of RFRP‐3 in the ovaries suggested that RFRP‐3 may regulate the follicular development. These results suggested that the changes of RFRP‐3 in response to food restriction might influence the HPO axis and inhibit ovarian development. 相似文献
122.
Zhang Q Li D Liu X Liu Z Cai X Wu G Qi S Yang S Yan X Shang Y He J Ma J Li J Ma W Han R Liu X Zhang J Xie Q Zhang Z 《Research in veterinary science》2008,85(2):368-371
This study was carried out to investigate the biological characteristics of the foot-and-mouth disease (FMD) virus strain Asia-1 China/2005, which is responsible for the 2005 epidemic in China. The result showed that this strain is not host restricted, and could not only cause FMD in cattle and sheep but also in pigs by either inoculation or direct contact. 相似文献
123.
动物标识及疫病可追溯体系建设,作为2007年中央一号文件《中共中央关于积极发展现代农业、扎实推进社会主义新农村建设若干意见》中的一项重要要求,是一个涉及范围广、技术性强、动用人员多的系统工程。松江作为上海市建立动物标识及疫病可追溯体系建设试点最早区,在 相似文献
124.
为研究夏枯草注射液的抗炎及抗菌作用,用二甲苯、蛋清分别造成小鼠和大鼠炎症模型来考察夏枯草注射液的抗炎作用,通过体外、体内抑菌试验来评价其抗菌作用。结果显示,夏枯草注射液能显著抑制Z-甲苯所致的小鼠耳肿胀和对蛋清致大鼠足跖肿胀,体外抗菌试验表明该注射液对痢疾杆菌、大肠杆菌、肺炎双球菌、溶血性链球菌有较好的抑菌作用,并对腹腔注射肺炎双球菌ATCC27853引起小鼠死亡有保护作用。夏枯草注射液具有抗炎、抗菌作用,可为该药的临床应用与机制研究提供理论依据。 相似文献
125.
家兔胸,腹,盆腔内脏初级传入神经元的分布特点 总被引:5,自引:0,他引:5
应用辣根过氧化物酶(HRP)法和荧光素逆行追踪法,对家兔心、肺、肝、胃、肾、子宫和膀胱的初级传入神经元分布规律进行了研究,结果表明,各内脏的初级传入神经元分布节段范围广泛,又有相对集中的节段;内脏与内脏之间的部分分布节段相互重叠,即使远距离相隔的内脏亦不例外,其中胸8 ̄10节段是胸、腹、盆腔脏器共同重叠节段;各内脏的感觉均经交感和副交感两个途径传入,其中心、肺、肝、肾、子宫以交感途径占优势,胃和膀 相似文献
126.
Li A Bennett D Gibbs C Carmichael S Gibson N Owen M Butterworth SJ Denny HR 《The Journal of small animal practice》2000,41(2):74-79
Between 1977 and 1992, 15 adult dogs were presented to the Universities of Bristol, Glasgow, Liverpool and London with fractures of the radial carpal bone which had occurred without a known episode of violent trauma. Eleven of the dogs were boxers and the other breeds affected were a Pharaoh hound, rottweiler, springer spaniel and a greyhound. The condition was bilateral in three cases. Eleven dogs were treated surgically by cast immobilisation (four cases), fragment removal (one case), lag screw fixation (three cases), pan-carpal arthrodesis (one case) and lag screw reduction followed by pan-carpal arthrodesis (two cases). The remaining four dogs were treated conservatively with rest and tactical use of non-steroidal anti-inflammatory drugs. Follow-up periods ranged from two months to 11 years. Varying degrees of lameness, which tended to be exacerbated by exercise, persisted in all cases. The radial carpal bone appears to have at least three separate centres of ossification which eventually fuse; their planes of fusion correspond approximately to the two main fracture lines. These areas of fusion could be weak points within the radial carpal bone. 相似文献
127.
Shelan Liu Yong Yang Zhifeng Pang Ying Liu Huan Li Jian Cai Zhuoying Wu Yan Luo Yuhuan Tang Lihong Ying Shuwen Qin Ziping Miao Na Zhao Yijuan Chen Jinren Pan Shijian Li Zhao Yu Feng Ling Enfu Chen Zhiping Chen 《Zoonoses and public health》2023,70(1):93-102
A cluster of Chlamydia psittaci (C. psittaci) cases was reported in Zhejiang Province, China, 2019. This study evaluates the extent of the outbreak and determines the source of infection. Real-time PCR and sequencing of the ompA gene of C. psittaci were performed to identify the cases, the domesticated poultry and close contacts. The index patient was a 76-year-old woman with chronic vertigo, and Case 2 was a 64-year-old female farmer with herpes zoster. Both women bought psittaci-infected chickens or ducks from the same mobile street vendor and raised them for 10 days and 23 days before fever onset. There were no direct contact between the two women. C. psittaci test was positive for the two patients, one sick chicken, three healthy ducks and the vendor's chicken cage. Phylogenetic analysis showed that all seven C. psittaci positive samples carried identical ompA genotype A of C. psittaci. Of all of the patients' 148 close contacts, none tested positive for C. psittaci, or developed acute respiratory symptoms. Both patients were discharged after a 4-week hospital stay. In conclusion, the source of this cluster was the poultry infected with C. psittaci, which occasionally cause infections in farmers, but inter-human transmission seems unlikely. 相似文献
128.
This study was designed to investigate the effects of dietary lipid levels on growth performance, lipid deposition and activities of lipid metabolic enzymes in hybrid tilapia (Oreochromis niloticus × O. aureus). Four isonitrogenous (300 g/kg crude protein) experimental diets containing graded levels of lipid (25, 55, 85 and 115 g/kg) were randomly assigned to triplicate groups of 180 juvenile fish. Fish were fed twice daily for 8 weeks. At the end of the experiment, the growth performance and proximate composition of fish were determined. The activities and gene expression of lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) were assessed as well. Fish fed the diets with 55 and 85 g/kg lipid had a significantly (p < 0.05) higher body weight gain than those fed the diets with 25 and 115 g/kg lipid. The whole-body and liver lipid contents were significantly (p < 0.05) elevated with increasing dietary lipid levels. Moreover, the activities and mRNA abundances of LPL and HSL in the liver, dorsal muscle and fat tissues were markedly altered by dietary lipid levels. Our data demonstrate a profound influence of dietary lipid levels on the growth and lipid deposition in hybrid tilapia, which is likely associated with the regulation of lipid metabolic enzymes including LPL and HSL. 相似文献
129.
1. The objectives of the study were to find polymorphic sites and elucidate the association between SNPs in the nuclear receptor coactivator 1 (NCOA1) gene and reproductive traits. 2. SNPs were detected by PCR-SSCP and DNA sequencing. Four SNPs were detected, including T10155007A, T10125838C, G10118492A and G10109315T. Three polymorphisms were associated with total egg production at the age of 300 d and the G10109315T polymorphism was associated with age at first egg. 3. In conclusion, the NCOA1 gene can be used as a molecular marker for reproductive traits in hens. 相似文献
130.
This study was conducted to investigate the pattern of DNA methylation in pronuclearstage mouse embryos derived from vitrified-warmed oocytes.Mouse oocytes at metaphase Ⅱ (MⅡ) stage of meiosis were all... 相似文献