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   98篇
  免费   15篇
  国内免费   9篇
化学   67篇
晶体学   3篇
力学   2篇
综合类   1篇
数学   7篇
物理学   42篇
  2022年   3篇
  2020年   4篇
  2019年   5篇
  2018年   5篇
  2017年   6篇
  2016年   9篇
  2015年   6篇
  2014年   10篇
  2013年   10篇
  2012年   5篇
  2011年   4篇
  2010年   6篇
  2009年   4篇
  2008年   3篇
  2007年   3篇
  2006年   5篇
  2005年   3篇
  2004年   7篇
  2003年   3篇
  2002年   3篇
  2001年   3篇
  2000年   2篇
  1999年   3篇
  1998年   3篇
  1996年   1篇
  1994年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1985年   1篇
  1983年   1篇
排序方式: 共有122条查询结果,搜索用时 812 毫秒
51.
A series of novel 1,2,4-triazole derivatives containing 1,2,3-thiadiazole ring was designed and synthesized. Their structures were confirmed by IR, 1^H NMR, high resolution mass spectrometer(HRMS) and electrospray ionization-mass spectromcter(ESI-MS) combined with melting points and elemental analysis. Preliminary bioassays indi- cate that these compounds exhibit good insecticidal activity against Aphis laburni at 100 μg/mL, especially compound 6b shows mortality of no less than 95%. Most of the compounds show good activities against tobacco mosaic virus(TMV) with different modes in vivo at 100 μg/mL. Compound 6d standed out, showing a good insecticidal activity and very high induction effects against TMV in vivo. Collectively, our data demonstrate a new strategy for insect and virus control.  相似文献   
52.
刘朋  宁英男  周全  毛国梁  牛忠伟 《化学进展》2015,27(10):1425-1434
烟草花叶病毒(tobacco mosaic virus, TMV)是人类最早发现的一种植物病毒。由于其独特的一维棒状结构、在纳米尺度下的单分散特性、良好的生物相容性、易于基因修饰和化学修饰等特点,近年来,TMV在自组装以及制备生物纳米复合材料等领域受到越来越多的关注。本文主要对TMV的结构特点、在自组装领域的研究进展以及在制备生物纳米复合材料的研究现状进行详细介绍并展望了其发展前景。  相似文献   
53.
用微波加热方法制得胶态纳米银,以该纳米银为基底,用激发波长为785 nm的便携式拉曼光谱仪获得了烟草花叶病毒的表面增强拉曼光谱。将获得的烟草花叶病毒的SERS谱与文献对比,TMV的SERS谱的谱峰都来源于蛋白质及核酸,与TMV的核壳结构是一致的。  相似文献   
54.
Three new isolates (1?3) including one new sterol and two new flavonoids together with three known sterols (4?6) were isolated from the leaves of Nicotiana tabacum. Their structures were determined mainly by spectroscopic methods, including extensive 1D and 2D NMR techniques. All compounds were evaluated for their anti-tobacco mosaic virus and cytotoxic activities. The results showed that compounds 2 and 3 exhibited high anti-TMV activity with inhibition rate of 34.2 and 33.4%, respectively, which were roughly equivalent to that of positive control. The cytotoxicities of compounds 1 and 46 against five human tumour cell lines were also tested, and tested compounds showed weak inhibitory activities against some tested human tumour cell lines.  相似文献   
55.
现有的番茄花叶病无损检测方法无法在潜育期内,即显症之前进行早期识别导致施药不及时或者盲目过度施药。设计与试制了红外热成像信息采集系统,主要包括:光箱、红外热成像仪、温度及升降控制器、加热板和升降载物台。该系统能够根据温度起止节点的要求,人为调节拍摄温度。在江苏大学现代农业装备与技术省部共建重点实验室Venlo型温室中进行非抗病性番茄品种辽宁农科院L-402的培育。采用叶面摩擦接种花叶病毒(Tobacccco mosaic virus, ToMV),分为轻度感染组(LI),重度感染组(SI);LI组为磷酸缓冲液稀释500倍后的病毒液接种,SI组为病毒原液接种。对照组(CG)喷施等量磷酸缓冲液。接种10 d后叶片开始出现病斑,证明接种后9 d为番茄花叶病的潜育期。使用红外热成像系统采集了三个组共计144个样本的红外热成像图,计算叶表最大温差(MTD) 以表征潜育期内连续9 d内的叶面温度变化情况。CG组叶片的MTD值差异极小,而接种后叶片MTD值随着病毒侵染时间的推进发生了显著的变化。接种6 d后MTD值差异最大可达1.63 ℃,第7 d开始差异逐步缩小,表明病毒的扩散范围增大导致病叶越来越多的区域被侵染使得整体叶温上升。光谱采集采用两种方法进行,一种是根据热像图的MTD值计算判别出温度突变区域后采集光谱,记为热像采集法(TCM);另一种是不考虑病灶位置,在叶尖、叶中、叶基三个区域分别随机选择一个点采集光谱后求平均值,记为随机采集法(RCM)。TCM确定三个光谱采集点的选择原则是:LI组接种后3,6和9 d的温度突变区域平均MTD值比CG组温度分别高出0.3,0.7和0.5 ℃。SI组接种后3,6和9 d的温度突变区域平均MTD值比CG组温度分别高出0.5,1.2,0.8 ℃。差值达到此标准的病灶位置才定为TCM的可选区域。对所有样本采用支持向量机(SVM)算法建立识别模型。采用主成分分析对2 151个波长点的光谱信息进行压缩,前6个主成分所对应的累积方差贡献率已到达99%。分别对感病3,6和9 d的样本按照2∶1的比例划分校正集和预测集,对预测集样本的病害程度进行识别。两种方法所建立的模型的总识别率分别为92.59%和99.77%。采用TCM建立的光谱识别模型中仅有接种后3 d的一个LI组样本未能识别出来,被误判成CG组样本外,其余组识别率均达到了100%。结果表明近红外光谱法识别番茄花叶病是可行的。采用红外热成像结合近红外光谱法能够建立识别率更高的番茄花叶病潜育期识别模型,克服点源采样随机性,对后续管控流程和突破作物早期精准用药的关键技术探索,建立更为精准的温室智能施药系统提供了新的思路。  相似文献   
56.
铌取代型钨硅杂多酸盐的合成及抗病毒活性研究   总被引:14,自引:4,他引:10  
杂多化合物因具有独特的结构和优异的抗病毒活性[1,2],近年来受到普遍重视,但研究的热点主要集中在抗艾滋病毒(HIV)、疱疹病毒(HSV)、抗肿瘤等方面[3,4],而忽视了对植物病毒防治的研究。  相似文献   
57.
Bitriazolyl acyclonucleosides were synthesized via the Huisgen reaction and then subjected to ammonolysis. The antiviral activity of these nucleosides against tobacco mosaic virus (TMV) was assessed. Like the previously described bitriazolyl compounds, these new bitriazolyl acyclonucleosides were found to show anti-TMV activity. This suggests that the bitriazolyl moieties are important structural features involved in the antiviral activity of these compounds.  相似文献   
58.
A nucleation in a reaction of a gas with a solid state where one of the products is solid (GSR‐S) has been discussed. It was pointed out that the phenomenon observed for nanopowders, i.e. nucleation in sequence of the crystallites sizes, should be valid in case of defected monocrystals. However in such a case the constituents of a monocrystal, i.e. mosaic domains separated by structural defects, should undergo phase transition in sequence of size or, in other words, the time needed for the initiation of a nucleus in the case of a small domain is shorter than in the case of big one. Finally the less defected the crystal is, the bigger domains are, and thus the longer nucleation time is needed.  相似文献   
59.
Focusing planar refractive mosaic lenses based on triangular prism microstructures have been used as an alternative approach for wide‐bandpass monochromatization of high‐energy X‐rays. The strong energy dependence of the refractive index of the lens material leads to an analogous energy dependence of the focal length of the lens. The refractive mosaic lens, in comparison with the refractive lens of continuous parabolic profile, is characterized by a higher aperture because of reduced passive material. In combination with a well defined pinhole aperture in the focal plane, the transmittance of photons of an appropriate energy can be relatively high and photons of deviating energy can be efficiently suppressed. The photon energy can be tuned by translating the pinhole along the optical axis, and the bandwidth changed by selecting appropriate pinhole aperture and beam stop. This method of monochromatization was realised at the ANKA FLUO beamline using a mosaic lens together with a 20 µm pinhole and beam stop. An energy resolution of 2.0% at 16 keV has been achieved.  相似文献   
60.
王新华  王晓坤 《中国光学》2015,8(5):785-793
为了满足工程应用对图像拼接实时性的要求,依据已设计完成的基于同心球透镜与微相机拼接阵列复合结构的十亿像素瞬态成像系统,提出一种基于统一计算设备架构(CUDA)与先验信息相结合的自适应图像拼接并行加速算法。首先,利用高精度四维标定平台对相邻微相机成像重叠区域进行预标定。接着,采用基于CUDA的快速鲁棒特征(SURF)方法检测提取重叠区域图像的候选特征点集。然后,运用基本线性代数运算子程序(CUBLAS)加速基于随机KD-Tree索引的近似最近邻搜索(ANN)算法,用于获取初始匹配点对。最后,提出一种改进的并行渐近式抽样一致性(IPROSAC)算法,用于剔除误匹配点对和空间变换矩阵的参数估计,从而得到拼接图像的空间几何变换关系。实验结果表明,该算法的图像拼接时间为287 ms,与单独采用CPU串行算法相比速度提高了近30倍。  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