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   395篇
  免费   21篇
  国内免费   1篇
化学   269篇
晶体学   1篇
力学   17篇
数学   22篇
物理学   58篇
无线电   50篇
  2023年   5篇
  2022年   6篇
  2021年   9篇
  2020年   8篇
  2019年   10篇
  2018年   19篇
  2017年   9篇
  2016年   16篇
  2015年   13篇
  2014年   14篇
  2013年   32篇
  2012年   44篇
  2011年   36篇
  2010年   26篇
  2009年   20篇
  2008年   18篇
  2007年   19篇
  2006年   19篇
  2005年   16篇
  2004年   19篇
  2003年   18篇
  2002年   13篇
  2001年   3篇
  2000年   2篇
  1999年   3篇
  1998年   1篇
  1997年   4篇
  1996年   5篇
  1994年   1篇
  1990年   1篇
  1987年   1篇
  1986年   1篇
  1985年   1篇
  1976年   1篇
  1975年   1篇
  1971年   1篇
  1970年   2篇
排序方式: 共有417条查询结果,搜索用时 984 毫秒
351.
In this paper, a new BIST based test approach to detecting short faults on the communication channels data links in network-on-chip is proposed. The rationale underlying the novelty of the proposed approach is that it is capable of locating the faulty channels while simultaneously performing the testing as well as updating the Routing Tables (RT) in which irregular Mesh-based and fault tolerant NoCs that are using Table-based routing. The proposed approach encompasses TPG and TRA located in the Network Adapter (NA) as well as a Packet Comparing Module (PCM) embedded in the routers. The approach, in addition, with a high scalability leads to 100% Test Coverage (TC) and 82.3% capability of diagnosing faulty channels in NoCs with a high scale. Furthermore, the approach is capable of being performed within one Round (two phase) run with a total time of 70 clocks which is considered as cost-effective compared with the preceding methods. The simulation results demonstrate that the hardware cost of PCM is trivial compared with the hardware of RASoC, HERMES, Æthereal and Vici routers.  相似文献   
352.
Fluorine-18 labeled aromatic amino acids are routinely used as tracers in positron emission tomography (PET) to study in vivo metabolic processes. The most versatile method for the production of such radiotracers is electrophilic fluorination of the aromatic amino acid with [18F]F2, which is most commonly produced by the gas-phase nuclear reaction 18O(p, n)18F. Although [18F]F2 is the major product, considerable amounts of [18F]OF2 (up to 20%) are also produced. Electrophilic fluorination reactions of l-phenylalanine, 3-nitro-l-tyrosine, 4-nitro-dl-phenylalanine, 3,4-dihydroxyphenyl-l-alanine (l-DOPA), 3-O-methyl-l-DOPA, 3,4-dimethoxy-l-phenylalanine, p-tyrosine and o-tyrosine in H2O and of m-tyrosine in anhydrous HF (aHF), CF3SO3H, CF3COOH, CH3COOH, HCOOH and H2O using OF2 were investigated. Although F2 is an efficient fluorinating agent in aHF, electrophilic fluorination reactions using OF2 were shown to be most efficient in less acidic media such as H2O. In addition, and contrary to reports that OF2 and F2 have similar reactivities, m-tyrosine was the only aromatic system studied that was fluorinated by OF2 and this was optimum in H2O for the fluorinated m-tyrosine isomers (total yield, 4.35 ± 0.04%). The presence of [18F]OF2 byproduct has no significant impact on the fluorination of aromatic amino acids investigated in this study and the subsequent production of their corresponding 18F-labeled radiotracers for patient use.  相似文献   
353.
The syntheses of haterumalides NA and NC were accomplished via the macrocyclization of a chlorovinylidene chromium carbenoid onto a pendant aldehyde to generate the C8-C9 bond with the desired stereoisomer as the major product. Utilizing the latter chemistry enables access to both C9 hydroxylated (haterumalides NC and ND) and C9 deoxygenated forms (haterumalides NA, NB, and NE; via deoxygenation of the C9-hydroxyl).  相似文献   
354.
A review of the amphiphilic derivatives of chitin, obtained by covalent grafting of hydrophilic and hydrophobic radicals, is given. It is shown that water-soluble alkylated derivatives of chitin and chitosan, as well as surfactant-polyelectrolyte complexes between oppositely charged surfactants, exhibit interfacial activity, forming structured (gel-like) adsorption layers (AL). Gel formation inside AL of chitin derivatives is characterized by means of interfacial dilational rheometry.  相似文献   
355.
Disaccharides are known to protect sensitive biomolecules against stresses caused by dehydration, both in vivo and in vitro. Here we demonstrate how interfacial accumulation of trehalose can be used to (1) produce rugged supported lipid bilayers capable of near total dehydration; (2) enable spatial patterning of membrane micro-arrays; and (3) form stable bilayers on otherwise lipophobic substrates (e.g., metal transducers) thus affording protecting, patterning, and scaffolding of lipid bilayers.  相似文献   
356.
We introduce a novel method to calculate the local dispersion relation in photonic crystal waveguides, based on the finite-difference time-domain simulation and filter diagonalization method (FDM). In comparison with the spatial Fourier transform method (SFT), the highly local dispersion calculations based on FDM are considerably superior and pronounced. For the first time to our knowledge, the presented numerical technique allows comparing the dispersion in straight and bent waveguides.  相似文献   
357.
Verifying the integrity of digital images and detecting the traces of tampering without using any protecting pre-extracted or pre-embedded information have become an important and hot research field. The popularity of this field and the rapid growth in papers published during the last years have put considerable need on creating a complete bibliography addressing published papers in this area. In this paper, an extensive list of blind methods for detecting image forgery is presented. By the word blind we refer to those methods that use only the image function. An attempt has been made to make this paper complete by listing most of the existing references and by providing a detailed classification group.  相似文献   
358.
Thermolysis of the bicyclic gallium hydrazide [(GaMe2)4(NH? NMe)(NH? NHMe)2] ( 1 ) yielded the unique cage compound [(GaMe)4(GaMe2)4(N2)(NH? NMe)4] ( 2 ). Compound 2 contains a remarkable hydrazinetetraide moiety, [N? N]4?, as the central structural motif which is stabilised by coordination to six gallium atoms.  相似文献   
359.
Abstract

A mild and operationally simple method for the synthesis of thiocyanohydrins is described. Mukaiyama reagent is used as an effective reagent for the solvent-free conversion of epoxides into their corresponding thiocyanohydrins. The reactions were completed in <5 min to give thiocyanohydrins with perfect regioselectivity and isolated yields.  相似文献   
360.
The rate constant of malachite green (MG+) alkaline fading was measured in water–ethanol–2‐propanol ternary mixtures. This reaction was studied under pseudo‐first‐order conditions at 283–303 K. It was observed that the observed reaction rate constants, kobs, were increased in the presence of different weight percentages of ethanol and 2‐propanol. The fundamental rate constants of MG+ fading in these solutions were obtained by using the SESMORTAC model. In each series of experiments, the concentration of one alcohol was kept constant and the concentration of the second one was changed. It was observed that at the constant concentration of one alcohol and variable concentrations of the second one, with an increase in temperature, k2 values decrease according to the trend of hydroxide ion nucleophilic parameter values and k1 values increase. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 441–453, 2011  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