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In this study, strength softening models are developed for exploring rainfall-induced landslide mechanism based on Mohr-Coulombstrength theory with both saturation degree and temporal evolution into consideration. According tothe ratio of two time scales available, the model can be classified into three categories, i.e., instant softeningmodel, delay softeningmodel, and couplingsoftening model.Corresponding evolution functions are specified to represent these kinds of softening processes andthen applied to simulate landslide of homogeneous slopes triggered by rainfall, therefrom, usefulconclusions can be drawn in the end. 相似文献
55.
Asphalt materials are used in a variety of applications such as road paving, waterproofing, roofing membranes, adhesive binders, rust proofing and water resistant coatings. There are available in a number of grades distinguished in terms of their softening point and flow resistance. The selection of the proper grade of asphalt for a particular application is governed by the desired flow behaviour. A knowledge of the complete flow curve depicting the variation of melt viscosity with shear rate at the relevant temperatures is necessary not only for proper grade selection, but also for specifying processing conditions for aggregate mixing and spraying. The rheological data are also useful in assessing end use performance. The scientific techniques for generating the rheological data involve the use of expensive, sophisticated instruments. Generation of the necessary flow data using these instruments is beyond the financial and technical means of most processors of asphalt materials. The engineering techniques involving the use of inexpensive vacuum viscometers are relatively easy, but provide a single point viscosity measurement at low shear rate. In the present work, a method is proposed for unifying the viscosity versus shear rate a data at various temperatures for a number of asphalt grades. A master curve has been generated that is independent of the grade of asphalt and the temperature of viscosity measurement. The master curve can be used to generate rheograms at desired temperatures for the asphalt grade of interest, knowing its zero-shear viscosity at that temperature.NCL Communication Number 2914. 相似文献
56.
S.?Mate?i? Mu?ani?Email author M.?Su?eska 《Journal of Thermal Analysis and Calorimetry》2009,96(2):523-529
The ageing of double base rocket propellants (DB rocket propellants), which is a consequence of chemical reactions and physical
processes that take place over time, has significant effect on their relevant properties (e.g. chemical composition, mechanical
properties, ballistic properties, etc.). The changes of relevant properties limit the safe and reliable service life of DB
rocket propellants. This is the reason why numerous research efforts are devoted to finding out reliable methods to measure
the changes caused by ageing, to assess the quality at a given moment of time, and to predict remaining life-time of DB rocket
propellants.
In this work we studied dynamic mechanical properties of DB rocket propellant artificially aged at elevated temperatures,
in order to detect and quantify changes in dynamic mechanical properties caused by the ageing. Dynamic mechanical properties
were studied using dynamic mechanical analyser (DMA).
The results obtained have shown that the ageing causes significant changes of DMA curve’s shape and positions. These changes
are quantified by following some characteristic points on DMA curves (e.g. glass transition temperatures; storage modulus,
loss modulus and tanδ at characteristic temperatures, etc.). It has been found out that the most sensitive parameters to the
ageing process are: storage modulus at viscoelastic and softening region, peak width and height on loss modulus curve, glass
transition and softening temperature, and tanδ at viscoelastic region. 相似文献
57.
The solid state photodimerization reaction ofo-methoxy cinnamic acid is shown to be mediated by a lattice phonon. The phonon participation, in this case, is through a mode
softening and not through strong exciton-phonon coupling as is generally observed. Raman phonon spectroscopy suggests that
the reaction is heterogeneous. Infrared spectroscopy has been used to study the internal vibrations of the reactant and the
product.
Partly presented at the International Laser Science Conference II, 1986 held at Seattle, USA. 相似文献
58.
叶志明 《应用数学和力学(英文版)》1998,19(1):37-43
1.IntroductionBynowfracturemechanicsisuniversallyacknowledgedasthetoolofanalysingtheinveshgationofconcretecracking.Andaftermanyyearsofdevelopmentonnumerousconstitutivemodelsforuniaxial,biaxialandtriaxialmodelsofconcreteundercompressivestresses,andtheirvariousrefinements,researchershavefinallyturnedtheirattentiontothecornerofthestressstraincurveandaregivingmoreattentiontotheeffectofcrackingonthenonlinearresponse.ofconcretestructures.Havingexperimentallyobservedthatthemacroscopicresponseofconcre… 相似文献
59.
提出了适用于纤维增强复合材料应变软化分析的多标量连续损伤模型,并将其应用于含分层裂纹的复合材料层板的后屈曲损伤破坏有限元分析,研究了软化参数对损伤场和应力场的影响。计算结果表明:(1)应变软化使分层尖端的应力奇异性降低或消失。(2)应变软化参数影响极限损伤区的大小及其扩展速度,应力跌落使极限损伤加剧。(3)由于损伤的影响,裂尖的能量释放率受软化参数的影响出现波动,已难反映分层特征,可以根据损伤程度来判断分层的扩展。(4)分层上下表面的纤维方向影响损伤形式及其扩展方向。 相似文献
60.
采用适当分子量的低软化点聚碳硅烷(LPCS)和四甲基二乙烯基二硅氮烷(TMDS)为原料,利用硅氢加成反应合成了高软化点聚碳硅烷(HPCS).研究了该反应的过程与特点,探讨了TMDS加入比例对产物特性的影响及其结构变化与可纺性的关系.结果表明,反应初期首先形成含乙烯基侧基的悬挂式结构,并随着硅氢加成反应完成,在LPCS分子间形成Si—N—Si桥联式结构.通过控制TMDS的加入比例,可以调控桥联反应程度从而控制产物的分子量及软化点.控制TMDS/LPCS质量比为0.08,得到了软化点为244~278℃,Mn=2.5×103,分子量呈双峰分布且具有良好可纺性的聚碳硅烷,适用于制备高性能连续Si C纤维. 相似文献