首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   454篇
  免费   9篇
  国内免费   26篇
林业   15篇
农学   27篇
基础科学   1篇
  32篇
综合类   187篇
农作物   36篇
水产渔业   5篇
畜牧兽医   160篇
园艺   16篇
植物保护   10篇
  2023年   5篇
  2022年   11篇
  2021年   28篇
  2020年   28篇
  2019年   1篇
  2018年   1篇
  2017年   34篇
  2016年   32篇
  2015年   21篇
  2014年   26篇
  2013年   34篇
  2012年   83篇
  2011年   50篇
  2010年   38篇
  2009年   24篇
  2008年   22篇
  2007年   16篇
  2006年   10篇
  2005年   7篇
  2004年   4篇
  2002年   1篇
  2001年   2篇
  2000年   2篇
  1999年   1篇
  1998年   1篇
  1996年   1篇
  1995年   1篇
  1994年   1篇
  1993年   1篇
  1990年   1篇
  1988年   1篇
  1984年   1篇
排序方式: 共有489条查询结果,搜索用时 17 毫秒
1.
旨在探究宿主蛋白程序性细胞死亡因子10(programmed cell death factor 10,PDCD10)通过抑制Ⅰ型干扰素表达进而促进口蹄疫病毒(foot-and-mouth disease virus,FMDV)的复制。首先,本研究验证了过表达和沉默PDCD10对FMDV复制的影响,接着利用双荧光素酶报告系统探究PDCD10对Ⅰ型干扰素信号通路活化的影响,最后,利用实时荧光定量PCR探究PDCD10对Ⅰ型干扰素通路下游刺激基因(IFN-stimulated genes,ISGs)转录的影响。结果表明,过表达PDCD10显著促进FMDV的复制,沉默PDCD10显著抑制FMDV的复制。与对照相比,过表达PDCD10后感染仙台病毒(Sendai virus,SeV)的细胞培养液上清液显著促进FMDV复制,进一步,PDCD10显著抑制SeV诱导的IFN-β启动子以及NF-κB的激活且呈剂量依赖性,并且PDCD10负调控Ⅰ型干扰素通路信号分子转录,最后还发现PDCD10负调控Ⅰ型干扰素下游ISGs转录。本研究结果为深入探究PDCD10在抗病毒天然免疫中的作用积累了资料。  相似文献   
2.
为探讨辐射对胡麻种子的诱变作用,以800 Gy、1000 Gy和1200 Gy 3种不同剂量的60Co-γ射线对6个胡麻品种(系)的种子进行辐射处理,观察其对胡麻种子萌发、农艺性状和品质性状的影响,并确定胡麻的最佳辐射剂量。结果表明,60Co-γ射线辐射胡麻种子以后,种子的发芽势、发芽率、株高、工艺长度、每果粒数、千粒重、含油率、亚油酸、油酸和棕榈酸含量均比对照降低,有效分茎数、有效分枝数、单株果数、木酚素、亚麻酸和硬脂酸含量均比对照高。且随辐射剂量的增加,发芽势、发芽率和木酚素含量逐渐下降,根长、苗高、平均单株鲜重、油酸含量先降低再升高,株高、工艺长度、有效分枝数、单株果数、千粒重、亚麻酸、硬脂酸和棕榈酸含量先升高后降低,有效分茎数、单株果数、每果粒数、不实果数、含油率和亚油酸含量均随处理浓度的增高而升高。拐点均出现在1000 Gy,且存在明显的品种间差异。胡麻种子的最佳辐射剂量理论值为1029 Gy。用60Co-γ射线处理胡麻种子,出现超亲材料的几率约为10%~21%,且木酚素含量出现超亲材料的几率最大,其次是亚麻酸含量,最后是含油率。高剂量(1200 Gy)有利于含油率和亚麻酸的变异,而低剂量(800 Gy)有利于木酚素的变异。研究结果为胡麻辐射育种和种质创新提供了理论依据。  相似文献   
3.
用不同剂量60Co-γ射线对益母草、蒲公英、车前、紫苏种子进行辐照处理,测定这4种药用植物种子的发芽率、发芽势、发芽指数等指标,了解60Co-γ射线辐照对其种子萌发的影响,为这4种药用植物的新品种选育提供参考。结果表明,60Co-γ射线对4种药用植物种子具有较强的诱发突变能力,辐照剂量与种子发芽率、发芽势、发芽指数、活力指数、苗高、苗鲜重均呈负相关,其中与苗高的相关性达极显著水平。益母草和蒲公英种子的半致死剂量大于400 Gy,车前种子的半致死剂量在300~400 Gy之间,紫苏种子的半致死剂量在50~100 Gy之间。  相似文献   
4.
通过富集方式和干燥方法的单因素实验,最陡爬坡试验和响应面设计,优化辣木鲜叶γ-氨基丁酸(γ-aminobutyric acid,GABA)的富集工艺。建立的辣木鲜叶中GABA最适富集条件为辣木鲜叶在45℃下,真空处理34 h,然后50℃干燥。该条件处理的辣木GABA含量为(19.70±0.16)mg/g,是对照的2.63倍。  相似文献   
5.
γ-Oryzanol is a main oleophilic component in rice bran oil and has been well recognized as a good dietary supplement for human health, as well as having uses in industrial materials. japonica-type rice cultivars generally showed significantly higher contents of total γ-oryzanol in brown rice compared with indica-type cultivars, although within-group variation was significant. The objective of this study was to explore quantitative trait loci (QTLs) responsible for the difference in the γ-oryzanol content between japonica-type and indica-type rice cultivars, using recombinant inbred lines (RILs), backcross inbred lines (BILs), and corresponding chromosome segment substitution lines (CSSLs) derived from crosses between japonica-type and indica-type. Results from RILs and BILs showed that eight QTLs were detected with R2 from .09 to .16. Nine candidate regions for QTL were also suggested from corresponding CSSLs. These QTLs from RILs and BILs and the candidate regions from CSSLs were not overlapped, although one QTLs was mapped near the boundaries of the respective candidate region. At four QTLs and three candidate regions, alleles or segments from japonica-type caused higher contents than those from indica-type. On the other hand, at the other four QTLs and six candidate regions, alleles or segments from indica-type caused higher contents than those from japonica-type, which is a reverse result to the parental differences. This result strongly suggested that alleles with increasing effects on γ-oryzanol content could be accumulated not only from japonica-type but also from indica-type, leading to a potential for increase in γ-oryzanol content in future breeding programs.  相似文献   
6.
γ-戊内酯是以木质纤维素生物质为原料制备的一种潜力巨大的平台化合物,它既可转化为高密度燃料、相关高分子材料以及其他高价值化学品,也可作为绿色溶剂促进木质生物质向其他高值方向转化。在化石能源日益紧俏、环境问题日益严重的今天,对γ-戊内酯进行深入研究显得尤为重要。但在实际生产中,仍存在产量低、除杂难等经济环保类问题需要解决。基于γ-戊内酯研究的最新进展,从γ-戊内酯的制备与应用两方面进行了论述,综述了生物质催化生产γ-戊内酯的研究进展,说明不同底物生产γ-戊内酯的理论基础与优缺点,并以贵金属和非贵金属催化剂为界,分类讨论了多种用于合成γ-戊内酯的催化剂。最后,结合γ-戊内酯在纤维素生物质转化应用方面的进展情况,探索了γ-戊内酯与其他相关有机物之间的制备关系,为γ-戊内酯的进一步开发利用提供了思路。  相似文献   
7.
[目的]γ-氨基丁酸(GABA)可增强作物品质和抗逆性,但其效果是否受植株根系耐盐性的影响尚不明确。因此,研究添加外源GABA对不同耐盐性番茄嫁接苗的生理调节机制及生长的影响,为小分子氨基酸在蔬菜生产中的应用提供理论依据。[方法]以耐盐性较强的砧用番茄‘OZ-006’为砧木、对盐分较敏感的‘中杂9号’为接穗形成的嫁接苗(RS)为材料,以‘中杂9号’自嫁接苗(SS)为对照材料,进行无土营养液栽培试验。以Hoagland营养液为基础,以调节NaCl浓度至175 mmol/L形成的盐胁迫条件作为对照(CK),在CK基础上设置添加5 mmol/L GABA处理(+G)。从处理后3天起,测定了幼苗生长、Na+积累、氨基酸含量及活性氧代谢指标。[结果]随着NaCl胁迫时间的延长,SS和RS幼苗均显著受到盐胁迫伤害,但RS幼苗盐害指数及Na+含量显著低于SS幼苗,其生长速率、叶绿素含量及氨基酸含量显著高于SS幼苗,其O2·-和MDA含量显著低于SS幼苗,表现为耐盐性显著高于SS幼苗。添加外源GABA后,SS和RS幼苗的鲜重、生长速率、叶绿素及氨基酸(GABA、谷氨酸和脯氨酸)含量、抗氧化酶(SOD、POD和CAT)活性均显著提高,根系和叶片内Na+含量、O2·-产生速率及MDA含量均显著降低,且SS幼苗耐盐性提高的效果大于RS幼苗。[结论]盐胁迫显著影响番茄幼苗的生长,尤其对耐盐性弱的品种生长抑制更加显著。γ-氨基丁酸(GABA)可有效提高番茄嫁接苗的耐盐性,主要原因在于GABA为幼苗提供了氮素营养,促进了盐胁迫下植物的生长和叶绿素的合成,同时GABA诱导细胞内多种氨基酸含量上升,叶片渗透调节能力增强,从而抑制了Na+过量积累,缓解了细胞内活性氧积累带来的膜伤害。此外,GABA添加对耐盐性弱的番茄嫁接苗耐盐性的提升效果比对耐盐性强的番茄嫁接苗更加明显。因此,在盐胁迫条件下,施用外源小分子氨基酸(如GABA)可能是提高作物耐盐能力的有效措施。  相似文献   
8.
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   
9.
IntroductionCystic echinococcosis (CE) is a chronic zoonotic disease caused by the larval stage of Echinococcus granulosus (E. granulosus), which affects domestic and wild carnivores as the definitive host and ungulates as intermediate hosts. In intermediate hosts, both Th1 and Th2 cells are involved in the immune responses to an echinoccocal infection. This study aimed to investigate production of IL-4, IL-10, and IFN-γ cytokines in peripheral blood mononuclear cells (PBMCs) of CE patients before and after surgical treatment.MethodsTo evaluate cytokine production in response to E. granulosus antigens, we investigated IL-4, IL-10, and IFN-γ production in PBMCs of 20 CE patients in response to hydatid cyst fluid antigen (HCF-Ag) before and after surgical treatment using ELISA.ResultsThe mean IL-4 production from HCF-Ag stimulated PBMCs was significantly decreased (p < 0.05), while IFN-γ was significantly increased in HCF-Ag stimulated PBMCs in patients after surgery (p = 0.005).Furthermore, our results showed that there is no significant difference between IL-10 production in patients before and after treatment (p = 0.562).ConclusionsOur data Indicated production of IL-4 in cultured PBMCs of CE patients stimulated with HCF-Ag was decreased significantly. While, production of IFN-γ was increased significantly in responses to HCF Ag after surgery. We concluded that the evaluation of IL-4 and IFN-γ in HCF-Ag stimulated PBMCs of CE patients should be considered as a useful marker in the follow up of patients with cystic echinococcosis.  相似文献   
10.
旨在研究复方术苦芩提取液对腹泻小鼠小肠上皮内淋巴细胞(intestinal intraepithelial lymphocyte,iIELs)及十二指肠INF-γ、IL-4 mRNA转录的影响。将72只小鼠随机分为6个组,分别为空白组、感染组、阳性药物组(黄芪多糖口服液,浓度为1.2 mg·mL-1)和药物Ⅰ、Ⅱ、Ⅲ组(复方术苦芩提取液,生药浓度分别为0.1、1和10 mg·mL-1)。除空白组外,小鼠连续给药7 d[灌胃0.5 mL·(次·d)-1]后腹腔注射5×107 CFU大肠杆菌,并将感染组小鼠出现腹泻时设定为试验0 h。于试验6 h和4 d时各处死6只小鼠,制作小肠病理切片并计数iIELs数量,qRT-PCR分析十二指肠段INF-γ、IL-4 mRNA水平。结果显示:阳性药物组和药物Ⅰ、Ⅱ、Ⅲ组对腹泻小鼠的保护率分别为66.7%、50.0%、66.7%、75.0%。试验6 h时,与空白组相比,感染组小鼠iIELs数量增加,十二指肠INF-γ mRNA水平降低、IL-4 mRNA水平增高,差异均极显著(P<0.01);与感染组相比,阳性药物组和药物Ⅰ、Ⅱ、Ⅲ组小鼠iIELs数量减少,阳性药物组和药物Ⅲ组小鼠十二指肠INF-γ mRNA水平增高、IL-4 mRNA水平降低。试验4 d时,与空白组相比,感染组小鼠十二指肠和回肠的iIELs数量增加,空肠iIELs数量减少,其十二指肠INF-γ、IL-4 mRNA水平增高,差异均极显著(P<0.01);与感染组相比,阳性药物组和药物Ⅰ、Ⅱ、Ⅲ组小鼠十二指肠和回肠的iIELs数量(Ⅰ组十二指肠除外)均减少,空肠iIELs数量增加,阳性药物组和药物Ⅲ组十二指肠段INF-γ、IL-4 mRNA水平均降低。结果表明,复方术苦芩提取液通过调控小鼠小肠iIELs数量,平衡十二指肠INF-γ/IL-4 mRNA转录,达到对小鼠腹泻的保护作用。  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号