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541.
Based on the cluster model for wave-like motions of a 2D vertically vibrated granular system we established previously (Chin Phys Lett, 2010, 27: 124501), a generalization of the cluster model for a 3D granular system is presented in this paper. The 3D cluster model proposes frustums of pyramids as clusters of the 3D granular system, and explains wave patterns as the result of the cluster-boundary and cluster-plate collisions. By analyzing the movement of one cluster in a collision period, we derive a basic equation, which relates the internal characteristic parameter to the external driving parameters. The theoretical results reproduce the behaviors of wave patterns as changes in the driving parameters, and the 3D dispersion relation, which agree with the experimental results. 相似文献
542.
To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubrication effect was modeled by reduction of the inter-particle friction coefficient and particle breakage was initiated by decreasing the particle strength.Once the strength of the particles decreased to a threshold value,the particles began to break so that new contacts could be established to transfer the external loads.Numerical simulations successfully reproduced the additional compaction of the material and the intensification of the horizontal stress in addition to the microscopic responses of the granular assemblies.The microscopic interpretation of the earth pressure coefficient at rest and the evolution of the grain number distribution during particle breaking were also investigated. 相似文献
543.
静态颗粒堆的应力分布是目前仍未完全解决的问题,有关文献曾对此提出多种不同的唯象应力关系模型,包括著名的固定主轴模型和新近提出的切应力模型等。本文从颗粒弹性理论的角度分析这些模型作为其近似解的可能性和改善的途径,结果表明它们在堆内部都能较好地满足弹性方程,在靠近自由边界时有明显偏差,但可通过降低侧边界附近的切应力强度的方法加以改善。 相似文献
544.
545.
A solution entropy model was developed for the undercooled binary eutectic alloy systems. As an extension of Taylor and Fidler
et al.’s model, the present model considered the change of phase composition with the increase of undercooling. Furthermore,
the sub-regular solution model and the interaction parameter (I
AB
) were also introduced. In this paper, the extended model is used to calculate the solution entropy for binary eutectic phases
under the undercooled condition, and the application scope of the model is also extended. Not only the growth manner of eutectic
phases, but also the transition of morphologies may be predicted and explained by calculating the solution entropy of eutectic
phases under the non-equilibrium condition with the developed model. Experimental results show that the developed model is
valid for the undercooled Ni-Si and Ni-Sn eutectic alloy systems.
Supported by the National Natural Science Foundation of China (Grant No. 50395103) and Doctorate Foundation of Northwestern
Polytechnical University (Grant No. CX200506) 相似文献
546.
Under the conventional solidification condition, a liquid aluminium alloy can be hardly undercooled because of oxidation.
In this work, rapid solidification of an undercooled liquid Al80.4Cu13.6Si6 ternary eutectic alloy was realized by the glass fluxing method combined with recycled superheating. The relationship between
superheating and undercooling was investigated at a certain cooling rate of the alloy melt. The maximum undercooling is 147
K (0.18T
E). The undercooled ternary eutectic is composed of α(Al) solid solution, (Si) semiconductor and θ(CuAl2) intermetallic compound. In the (Al+Si+θ) ternary eutectic, (Si) faceted phase grows independently, while (Al) and θ non-faceted
phases grow cooperatively in the lamellar mode. When undercooling is small, only (Al) solid solution forms as the leading
phase. Once undercooling exceeds 73 K, (Si) phase nucleates firstly and grows as the primary phase. The alloy microstructure
consists of primary (Al) dendrite, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic at small undercooling, while
at large undercooling primary (Si) block, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic coexist. As undercooling
increases, the volume fraction of primary (Al) dendrite decreases and that of primary (Si) block increases.
Supported by the National Natural Science Foundation of China (Grant Nos. 50121101, 50395105) and the Doctorate Foundation
of Northwestern Polytechnical University (Grant No. CX200419) 相似文献
547.
提出了一种基于现场承载板试验的粒料层非线性弹性参数的反算方法,即根据路面粒料层表面上承载板试验时逐级加载测试的弯沉,应用非线弹性有限元方法和改进的非线性最小二乘法反算粒料层的非线性弹性模型参数,并针对反算过程中的缺陷提出了修正方法.在此基础上研制了粒料层非线性弹性参数反算软件,并将粒料层非线性计算的理论弯沉与现场承载板试验的实测弯沉进行对比,论证了所提反算方法的合理可行性. 相似文献
548.
颗粒材料是土木、水利、交通等大型工程中广泛应用的一种建筑材料,在较大外力作用下会产生颗粒破碎现象,影响到工程的强度和变形要求。天然岩质颗粒材料由于其属性及加载方式等因素的影响,其破碎强度和破坏方式具有离散性和多样性的特征。在近百年曲折发展历程中,可将颗粒破碎问题研究划分为三个阶段:初步探索阶段、破碎现象描述阶段和广泛研究阶段。试验研究作为颗粒破碎问题研究的一种重要方法,可归纳为天然材料试验和人工材料模拟试验两类。通过整理两类研究方式的研究重点,讨论了现有方法存在的局限性,提出了基于颗粒破碎问题可能的研究方向。 相似文献
549.
为了进一步扩展粗糙集的应用范围和灵活性,利用构造性方法研究了双论域粗糙集的不确定性度量,分析了双论域粗糙集不确定性度量与由双论域粗糙集诱导的Pawlak粗糙集的粒度之间的关系.通过比较Pawlak近似空间中粒度的大小,定义了不同信息系统中关系的粗细程度,给出了反映信息系统分类能力的双论域粗糙集信息熵和信息粒度的定义,研究了双论域粗糙集信息熵和信息粒度与信息系统中关系的粗细程度之间的关系.结果表明:双论域粗糙集的信息熵越大,信息系统的不确定性越强,信息系统中关系的区分能力越弱;信息系统的关系越精细,双论域粗糙集的信息熵越小,双论域粗糙集的信息粒度越小. 相似文献
550.
固定化甲烷八叠球菌处理豆制品废水研究 总被引:2,自引:0,他引:2
利用实验室规模的两步厌氧消化器,以厌氧絮状污泥及固定化甲烷八叠球菌对酸化反应器接种,用厌氧颗粒污泥对甲烷化反应器接种处理豆制品废水,试图阐明固定化甲烷八叠球菌在此工艺运转中的作用.反应器的平均水滞留期为111h,最短水滞留期达到了35h.反应器的最高产气率达157L/(L·d),平均产气率为75L/(L·d).运转期间所产气体的平均甲烷含量为702%.在低有机物负荷下,固定化甲烷八叠球菌发挥着很大作用,有较低的出水COD和较高的甲烷含量,但在较高有机物负荷下,与对照无明显差别.其原因是在高有机物负荷和短水滞留期运转条件下,固定化甲烷八叠球菌活性受到抑制. 相似文献