全文获取类型
收费全文 | 6825篇 |
免费 | 340篇 |
国内免费 | 799篇 |
专业分类
林业 | 904篇 |
农学 | 1136篇 |
基础科学 | 529篇 |
1205篇 | |
综合类 | 1893篇 |
农作物 | 406篇 |
水产渔业 | 312篇 |
畜牧兽医 | 842篇 |
园艺 | 224篇 |
植物保护 | 513篇 |
出版年
2024年 | 15篇 |
2023年 | 37篇 |
2022年 | 167篇 |
2021年 | 263篇 |
2020年 | 244篇 |
2019年 | 247篇 |
2018年 | 166篇 |
2017年 | 224篇 |
2016年 | 209篇 |
2015年 | 291篇 |
2014年 | 268篇 |
2013年 | 347篇 |
2012年 | 423篇 |
2011年 | 439篇 |
2010年 | 423篇 |
2009年 | 420篇 |
2008年 | 365篇 |
2007年 | 359篇 |
2006年 | 420篇 |
2005年 | 409篇 |
2004年 | 202篇 |
2003年 | 146篇 |
2002年 | 115篇 |
2001年 | 133篇 |
2000年 | 151篇 |
1999年 | 212篇 |
1998年 | 167篇 |
1997年 | 153篇 |
1996年 | 128篇 |
1995年 | 114篇 |
1994年 | 105篇 |
1993年 | 106篇 |
1992年 | 102篇 |
1991年 | 70篇 |
1990年 | 79篇 |
1989年 | 74篇 |
1988年 | 54篇 |
1987年 | 38篇 |
1986年 | 24篇 |
1985年 | 16篇 |
1984年 | 10篇 |
1983年 | 5篇 |
1982年 | 12篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
排序方式: 共有7964条查询结果,搜索用时 500 毫秒
991.
992.
993.
为了同时检测禽肾炎病毒(avian nephritis virus,ANV)和鸡细小病毒(chicken parvovirus,ChPV),根据GenBank中ANV的ORF基因和ChPV的NS1基因的保守序列,设计筛选了扩增片段大小分别为511 bp和242 bp的特异性引物,通过反应条件优化、特异性和敏感性试验,建立了一种双重PCR检测方法。该方法最佳引物比例为ANV上下引物各0.4μL(20 mol/L),ChPV上下引物各0.6μL(20 mol/L);最佳退火温度为53.8℃;灵敏度可达到55 fg(ANV)和58 fg(ChPV);对常见鸡病病原体进行检测,结果全为阴性。本研究建立的PCR方法具有特异、敏感、快速、稳定的优点,可用于同时鉴别诊断ANV和ChPV的混合感染。 相似文献
994.
995.
Juzuo Zhang Liqun Xue Ang Nie Qing Yang Xuan Peng Zhilong Chen Lisha Yang Yang Xie Anwen Yuan Junfei Xu 《Reproduction in domestic animals》2020,55(11):1479-1489
Non-infectious prenatal mortality severely affects the porcine industry, with pathological placentation as a likely key reason. Previous studies have demonstrated that peroxisome proliferator-activated receptor gamma (PPARγ) deficiency causes defects in the uteroplacental vasculature and induces embryonic losses in mice. However, its role in porcine placental angiogenesis remains unclear. In the present study, PPARγ expression was investigated in porcine uteroplacental tissues at gestational day (GD) 25, GD40 and GD70 via quantitative polymerase chain reaction (qPCR), Western blot and immunohistochemistry (IHC). Moreover, the roles of PPARγ in porcine placental angiogenesis were investigated using a cell model of porcine umbilical vein endothelial cells (PUVECs) to conduct proliferation, migration and tube formation assays in vitro and a mouse xenograft model to assess capillary formation in vivo. The results showed that PPARγ was mainly located in the glandular epithelium, trophoblast, amniotic chorion epithelium and vascular endothelium, as indicated by the higher expression levels at GD25 and GD40 than at GD70 in endometrium and by higher expression levels at GD40 and GD70 than at GD25 in placenta. Moreover, PPARγ expression was significantly downregulated in placenta with dead foetus. In PUVECs, knocking out PPARγ significantly inhibited proliferation, migration and tube formation in vitro and inhibited capillary formation in mouse xenografts in vivo by blocking S-phase, promoting apoptosis and downregulating the angiogenic factors of VEGF and its receptors. Overall, the spatiotemporal heterogeneity of PPARγ expression in porcine uteroplacental tissue suggests its vital role in endometrial remodelling and placental angiogenesis, and PPARγ regulates placental angiogenesis through VEGF-mediated signalling. 相似文献
996.
分级指数与相对值在奶牛用粗饲料品质评定上的比较研究 总被引:4,自引:2,他引:2
本文在测定江西奶牛养殖常用的6种粗饲料(串叶松香草、桂牧1号杂交象草、矮象草、黑麦草、墨西哥玉米与鸭茅)的常规成分基础上,实测了奶牛对这6种粗饲料的干物质随意采食量(DMI),并采用相关模型计算出这6种粗饲料的分级指数(GI)与相对值(RFV)。分别应用单项指标粗蛋白(CP)、中性洗涤纤维(NDF)、干物质随意采食量(DMI)以及综合指标RFV、GI对试验用6种粗饲料品质的分级进行了比较。研究表明:单一指标都难以正确地评定粗饲料品质,必须使用综合的整体指标。GI是首个将粗饲料的可利用能、CP、NDF与家畜的DMI综合起来考虑的一个粗饲料综合评定指数,对粗饲料的分级比RFV更精确。 相似文献
997.
Wang D Fang L Li T Luo R Xie L Jiang Y Chen H Xiao S 《Veterinary immunology and immunopathology》2008,125(3-4):344-353
The IFN-beta promoter stimulator 1 (IPS-1), also known as MAVS/VISA/Cardif, is an adaptor molecule for the retinoic-acid-inducible protein I (RIG-I) or melanoma-differentiation-associated gene 5 (MDA5) that recognizes intracellular double-stranded RNA (dsRNA) and triggers a signal for producing type I IFN. In the present study, porcine IPS-1 cDNA was cloned, using RT-PCR coupled with rapid amplification of cDNA ends (RACE)-PCR, from porcine peripheral blood mononuclear cells. The open reading frame of porcine IPS-1 consists of 1575bp encoding 524 amino acids. The putative porcine IPS-1 protein contains a N-terminal CARD-like domain, a central proline-rich domain, a C-terminal transmembrane domain, and exhibits similarity to mouse, rat, monkey, human and cattle counterparts, ranging from 59% to 79%. Semi-quantitative RT-PCR showed that porcine IPS-1 mRNA was widely expressed in different tissues. Porcine kidney (PK-15) cells transfected with a DNA construct encoding porcine IPS-1 produced type I IFN, and activated IRF3 and NF-kappaB. Deletion mutant analyses further revealed that both the CARD-like domain and transmembrane domain are essential for these functions. In addition, poly(I:C)-induced porcine IFN-beta promoter activation in PK-15 cells was significantly reduced by siRNA targeting IPS-1, indicating that IPS-1 is an important immunoregulator in the porcine innate immune system. The availability of porcine IPS-1 and establishment of its function in the type I IFN signaling pathway provides a useful molecule for defining its role during the course of pig infectious diseases. 相似文献
998.
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
999.
为建立一种牛支原体(Mycoplasma bovis,MB)和牛病毒性腹泻病毒(Bovine viral diarrhea virus,BVDV)的快速鉴别诊断方法,针对MB的uvr C基因和BVDV的5'端非编码区(5'-UTR)保守基因序列,分别设计两对特异引物,并将三温式PCR扩增程序简化为二个温度梯度,建立了鉴别MB和BVDV的二重二温式PCR方法。该方法能同时扩增MB和BVDV,扩增产物大小分别为412和170 bp。特异性试验结果显示,该方法对参试的所有毒株只扩增MB和BVDV基因组,对其它牛病原体无扩增;敏感性试验结果显示,该方法最低能同时检测到104拷贝的两种目的核酸;干扰性试验结果显示,该方法能同时检测两个模板不同浓度的组合,试验结果不受模板影响。综上,本研究所建立的二重二温式PCR方法特异、敏感、快速、简便,可应用于MB和BVDV临床鉴别诊断和流行病学调查。 相似文献
1000.
犬细小病毒(CPV)自1978年被首次分离到以来,已由CPV-2演化出CPV-2a、CPV-2b和CPV-2c 3种新抗原型。为了解江苏省扬泰地区的CPV分子特征和基因型,2015年5月至2016年12月在扬州和泰州地区宠物医院,根据患病犬临床症状以及CPV快速检测试纸条初步诊断结果,收集可疑病例的肛门棉拭子或粪便作为检测样品,扩增样本中CPV的VP2基因片段并对扩增产物进行测序和分析。结果显示:在48份样品中,4份被鉴定为CPV-2型,24份被鉴定为CPV-2a型,20份被鉴定为CPV-2b型,并未发现CPV-2c型。结果表明,该期间CPV-2a 型与CPV-2b型成为扬泰州地区的优势基因型,需开展这些新基因型的深入研究和防控。 相似文献