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Assessment of fractured long bone using ultrasonic guided wave(GW) has gained considerable attention.This paper focuses on using the hybrid boundary element method (HBEM) to analyze the propagation characteristics of ultrasonic GW in fractured long bones. The reflection coefficients(RC) and transmission coefficients(TC) for different depth-to-width ratio(d/w) cracks were numerically calculated and analyzed.It has been shown that the primary output modes,which include the transmission and reflection modes,are the same as the incidence modes.For some cracks,different TC curves always got the local maxima in adjacent frequencies.For different d/w cracks,most of the TC curves had local maxima which are not overlapped.These simulation results are helpful to optimize the modes and frequencies of the incidence GWs for quantitatively evaluating the bone quality and providing the numeral results of the cracks in long cortical bones. 相似文献
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充粘液管材中超声纵向轴对称导波的频散特性分析 总被引:1,自引:0,他引:1
模拟分析充粘液管内径-壁厚比和超声纵向轴对称导波波包宽度的关系。考虑了衰减的情况下,在各传播距离、频厚积和激发脉冲周数上,采用脉冲回波法,分析了导波的频散特性。结果表明:对于特定的材料,当频厚积一定时,充粘液管材中传播的导波特性只与内径-壁厚比有关;各高阶模式的截止频厚积随内径-壁厚比的增大而减小。用L(0,1)模式检测内径-壁厚比在4附近的充粘液管时灵敏度较低;而用L(0,2)模式检测内径-壁厚比在9.2附近的管时灵敏度较低。对于不同内径-壁厚比的充粘液管,检测中应当用不同的纵向轴对称导波模式,所用的激发脉冲周数和频厚积也应当不同。 相似文献
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Daniel A Paterson Jordan P Abberley William TA Harrison John MD Storey 《Liquid crystals》2017,44(1):127-146
ABSTRACTThe synthesis and characterisation of several members of the 1,ω-bis(4-cyanobiphenyl-4′-yl) alkane (CBnCB) and the 1-(4-cyanobiphenyl-4′-yloxy)-ω-(4-cyanobiphenyl-4′-yl) alkane (CBnOCB) homologous series are reported. The new odd members described CB5CB, CB13CB, CB4OCB, CB8OCB and CB10OCB all exhibit twist-bend nematic and nematic phases. The members of these series already reported in literature, CB7CB, CB9CB, CB11CB and CB6OCB, were also prepared in order to allow for a direct comparison of their transitional properties. The properties of these dimers are also compared to those of the corresponding members of the 1,ω-bis(4-cyanobiphenyl-4,-yloxy) alkanes (CBOnOCB). For any given total spacer length, for odd members of these series, the nematic–isotropic transition temperatures and associated entropy changes are greatest for the CBOnOCB dimer and lowest for the CBnCB dimer. These trends are understood in terms of molecular shape. For short spacer lengths, the twist-bend nematic–nematic transition temperature (TNTBN) is higher for the CBnOCB series than for the CBnCB series but this is reversed as the spacer length increases. Of the CBOnOCB dimers, a virtual value of TNTBN was estimated for CBO3OCB and TNTBN was measured for CBO5OCB. These values are considerably lower than those observed for the corresponding members of the CBnCB or CBnOCB series. The dependence of TNTBN on molecular structure is discussed not only in terms of the molecular curvature but also in the ability of the molecules to pack efficiently. As the temperature range of the preceding nematic phase increases, so the twist-bend nematic–nematic transition entropy change decreases and the transition approaches second order for the longer spacers. For comparative purposes, the transitional behaviour of the even-membered dimers CB6CB, CB5OCB and CBO4OCB is reported and differences accounted for in terms of molecular shape. 相似文献
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DS Zhulai SA Bugaychuk GV Klimusheva TA Mirnaya VN Asaula VI Handziuk 《Liquid crystals》2017,44(8):1269-1276
The class of thermotropic ionic liquid crystals (LCs) of the metal alkanoates possesses a number of unique properties, such as intrinsic ionic conductivity, high dissolving ability and ability to form time-stable mesomorphic glasses. These ionic LCs can be used as nanoreactors for the synthesis and stabilisation of different types of nanoparticles (NPs). Thus, some semiconductors, metals and core/shell NPs were chemically synthesised in the thermotropic ionic liquid crystalline phase (smectic A) of the cadmium octanoate (CdC8) and of the cobalt octanoate (CoC8). By applying the scanning electron microscopy, the cadmium and cobalt octanoate composites containing CdS, Au, Ag and core/shell Au/CdS NPs have been studied. NPs’ sizes and dispersion distribution of the NPs’ size in the nanocomposites have been obtained. 相似文献
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J. A. Blanc T. L. M. Langlands J. R. Crooks S. R. Milne-Jones C. A. D'Urso C. A. Stone 《Journal of Radioanalytical and Nuclear Chemistry》1997,219(2):221-230
We are developing a multimedia encyclopedia that provides a framework for students to leam nuclear science. A variety of media formats are used to present concepts, including text, static figures, animations, and video. Two special prsentation formats use dynamically produced simulations to expose students to nuclear science relationships. These media types provide greater interactivity and flexibility than simple animations. Students access information through tutorials, a dictionary of nuclear science terms, biographies of notable scientists, and a timeline of nuclear science history. The tutorial organization emphasizes the interrelationships among topics. We present an overview of the encyclopedia. 相似文献
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A coordination polymer of [Cd{5-(NO2)sal}2(2,2′-bipy)]n(5-(NO2)sal=5-nitrosalicylate, 2,2′-bipy=2,2′-bipyridine) was synthesized by hydrothermal reaction and characterized by elemental analysis, IR and X-ray diffraction single crystal structure analysis. The title complex crystallizes in monoclinic with space group C2/c, a=2.730 8(16) nm, b=1.272 3(5) nm, c=0.674 5(3) nm, β=96.73(2)°, V=2.327(2) nm3, Z=4, R=0.022 2, wR=0.057. The 5-nitrosalicylate anions doubly bridge the Cd(Ⅱ) atoms to form one-dimensional polymeric chain with the repeated eight-membered ring units (Cd-O-C-O)2. The crystal structure is stabilized by intra- and interchain hydrogen bonds interactions. CCDC: 694568. 相似文献