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   30篇
  免费   0篇
化学   10篇
数学   10篇
物理学   4篇
无线电   6篇
  2023年   3篇
  2020年   1篇
  2017年   1篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2012年   2篇
  2011年   2篇
  2010年   3篇
  2009年   3篇
  2008年   4篇
  2006年   3篇
  2000年   2篇
  1997年   1篇
  1991年   1篇
排序方式: 共有30条查询结果,搜索用时 203 毫秒
1.
CLIMATIC CHANGE SINCE LITTLE ICE AGE RECORDED BY DUNDE ICE CAP   总被引:21,自引:0,他引:21  
The climatic change since the Little Ice Age recorded in the Dunde Ice Cap is presentedin this paper. There have been three cold periods and three warm periods since 1400AD.Among them, the coldest one was in the 17th century. Many evidences verified the three coldand warm variations recorded in the Dundc Ice Cap. But it was found from the comparison between the Dunde Icc Cap climatic record and thewinter temperature record in Shanghai that there was a temporal dfference in climatic changebetween East China and West China. The general trend is that the cooling and warmingprocesses in West China were earlier than that in East China. In the Dunde Ice Cap, it isnow in an anomalous warm period, while it is not as warm as in Dunde Ice Cap recordaccording to the winter temperature in Shanghai. In addition to the possible cause of temporaldifference in climatic change between West China and East China, another possible cause isthat the greenhouse effect of CO_2 may already be recognizable in the Dunde Ice Cap a  相似文献   
2.
An efficient synthesis of new cap analogs containing aminoallyl linkers such as m7G[5′]pppp[5′]U-aminoallyl and m27,3′OG[5′]pppp[5′]U-aminoallyl is reported. The final cap analog has been isolated with high purity (>99.8%) after ion-exchange column purification.  相似文献   
3.
In this paper we compare different multifactor HJM models with humped volatility structures, to each other and to models with strictly decreasing volatility. All the models are estimated on Euribor and swap rates panel data maximizing the quasi-likelihood function obtained from the Kalman filter. We develop the analysis in two steps: first we study the in-sample properties of the estimated models, then we test the pricing performance on caps. We find the humped volatility specification to greatly improve the model estimation and to provide sufficiently accurate cap prices, although the models has been calibrated on interest rates data and not on cap prices. Moreover, we find the two-factor humped volatility model to outperform the three-factor models in pricing caps.  相似文献   
4.
5.
New monolithic HPLC columns were prepared by γ-radiation-triggered polymerization of hexyl methacrylate and ethylene glycol dimethacrylate monomers in the presence of porogenic solvents. Polymerization was carried out directly within capillary (250-200 μm I.D.) and nano (100-75 μm I.D.) fused-silica tubes yielding highly efficient columns for cap(nano)-LC applications. The columns were applied in the complete separation of core (H2A, H2B, H3, and H4) and linker (H1) histones under gradient elution with UV and/or electrospray ionization (ESI) ion trap mass spectrometry (MS) detections. Large selectivity towards H1, H2A-1, H2A-2, H2B, H3-1, H3-2 and H4 histones and complete separation were obtained within 8 min time windows, using fast gradients and very high linear flow velocities, up to 11 mm/s for high throughput applications. The method developed was the basis of a simple and efficient protocol for the evaluation of post-translational modifications (PTMs) of histones from NCI-H460 human non-small-cell lung cancer (NSCLC) and HCT-116 human colorectal carcinoma cells. The study was extended to monitoring the level of histone acetylation after inhibition of Histone DeACetylase (HDAC) enzymes with suberoylanilide hydroxamic acid (SAHA), the first HDAC inhibitor approved by the FDA for cancer therapy. Attractive features of our cap(nano)-LC/MS approach are the short analysis time, the minute amount of sample required to complete the whole procedure and the stability of the polymethacrylate-based columns. A lab-made software package ClustMass was ad hoc developed and used to elaborate deconvoluted mass spectral data (aligning, averaging, clustering) and calculate the potency of HDAC inhibitors, expressed through a Relative half maximal Inhibitory Concentration parameter, namely R_IC(50) and an averaged acetylation degree.  相似文献   
6.
Olympia Talelli 《代数通讯》2013,41(3):1167-1172
Here we show that a countable group G has periodic cohomology of period q after some steps with the periodicity isomorphisms induced by cup product with an element in H q (G, ?) if and only if G has periodic homology of period q after some steps with the periodicity isomorphisms induced by cap product with an element in H q (G, ?). In [2 Asadollahi , J. , Hajizamani , A. , Salarian , Sh. Periodic flat resolutions and periodicity in group (co)homology. To appear in Forum Mathematicum.  [Google Scholar]] Asadollahi, Hajizamani, and Salarian showed that, if a group G is such that every flat ?G-module has finite projective dimension, then G has periodic cohomology of period q after some steps with the periodicity isomorphisms induced by cup product with an element in H q (G, ?) if and only if G has periodic homology of period q after some steps with the periodicity isomorphisms induced by cap product with an element in H q (G, C), where C is the cotorsion envelope of the trivial ?G-module ?.  相似文献   
7.
文章列举了四个案例,阐述了现行国内印制电路板标准与国外标准之间的差异,以此说明国内电子电路行业标准发展任重而道远。  相似文献   
8.
The Gale transform is an involution on sets of points in a projective space. It plays a crucial role in several different subjects, such as algebraic geometry, optimization, coding theory, etc. Sometimes, in the literature, the Gale transform is used implicitly, without mentioning it as such. In the present paper, we give a short account of the algebraic and geometrical implications that the Gale transform has when it is applied to sets of points in finite projective spaces.  相似文献   
9.
A low resistivity ohmic contact to Si-implanted GaN was achieved using a metal combination of Ti/Al. The effect of a protection cap during post-implantation annealing is investigated, and how it affects the specific contact resistivity (ρc). Relevant differences between the protected (PR) sample with SiO2 and unprotected (UP) sample during the post-implantation annealing were observed after metal alloying at 700 °C. The lower values of ρc have been obtained for UP sample, but with very low reproducibility. In contrast, SiO2 cap layer has demonstrated its relevance in yielding a much more uniformity of a relatively low ρc around 10−5 Ω cm2. Related mechanism for the uniformity in ρc was discussed based on the results obtained from electrical measurements, XRD (X-ray diffraction) analysis, AFM (atomic force microscopy) and SEM (scanning electron microscopy) observations.  相似文献   
10.
Si^+注入GaAs及其退火中SiO2包封的作用   总被引:1,自引:0,他引:1  
对Si^+注入GaAs的前后及其退火的前后用和不用SiO2包封进行了对比实验。包封退火大大提高了注入离子的激活率;在包封退火的情况下,光片注入的要比贯穿注入的载流子分布窄。所以,光片注入后包封退火较实用,它使载流子分布窄,激活率高。  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