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排序方式: 共有295条查询结果,搜索用时 187 毫秒
1.
Sangmin Lee Biao Che Meiling Tai Wanzhao Li Shin-Hyun Kim 《Advanced functional materials》2021,31(42):2105477
Hydrogel shells that compartmentalize the water core from the aqueous surrounding provide molecular selectivity on size and charge in transmembrane transport. It is highly demanding to produce thin hydrogel shells to minimize diffusion length and maximize core volume. Here, internal osmosis in water-in-oil-in-water-in-oil (W/O/W/O) triple-emulsion droplets is used to produce thin hydrogel shells enclosing a large water core. The triple-emulsion droplets are prepared to have an ultrathin middle oil layer using a capillary microfluidic device. The innermost water droplet has a higher osmolarity than the outer water layer containing photopolymerizable hydrogel precursors, which pumps water from the outer layer to the core through the ultrathin oil layer by the osmosis. Therefore, the outer layer gets thinner and hydrogel precursors are enriched while the size of the triple-emulsion droplets remains unchanged. Through photopolymerization of precursors and phase transfer from oil to water, hydrogel shells enclosing water core are produced in the water environment; the oil layer is ruptured for molecular exchange through the shells. The thickness and composition of the hydrogel shells are precisely controllable by the osmotic conditions. The shells show a high permeation rate due to the thinness as well as controlled cut-off threshold of permeation for neutral and charged molecules. 相似文献
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4.
Kwang‐Jea Kim Sangmin Kwon Hyun Kim Patit P. Kundu Yong‐Wook Kim Yong‐Keun Lee Kyu Jong Lee Byung H. Lee Soonja Choe 《应用聚合物科学杂志》2003,87(2):311-321
The mixing cycle‐dependent degree of dispersion and degree of mixing of a calcite (calcium carbonate) agglomerate in high‐density polyethylene (HDPE), low‐density polyethylene (LDPE), and linear low‐density polyethylene (LLDPE) matrices upon stretching was investigated using three different techniques: mechanical property, morphological behavior, and image analyzer analyses. The mechanical properties analyzed in terms of the tensile strength and maximum elongation resulted in that the second mixing was the best for giving a better property for all systems except the LDPE system, which exhibited no significant difference between the second and third mixings. The morphological behavior of the three compounds were different, but no distinctive difference was observed to differentiate the degree of mixing from system to system. The number‐, weight‐, and z + 1‐average diameters of the air hole and the aspect ratio upon the stretching and mixing cycle were calculated to analyze the degree of mixing of the calcite‐filled composites. As a consequence, no difference in the average diameter of the air hole was obtained among the three systems, but the aspect ratios of the air hole varied significantly. Thus, the degree of dispersion and the degree of mixing may be influenced by the average calcite agglomerate size, the average diameter of the air hole, and the aspect ratio upon stretching and mixing cycles. Those factors would be formed by the difference in chemical characteristics upon various microstructures of polyethylene and its molecular weight and molecular weight distribution. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 311–321, 2003 相似文献
5.
Dong-Wan Cho Chul-Min Chon Hyuncheol Yang Yiu Fai Tsang Hocheol Song 《Clean Technologies and Environmental Policy》2018,20(10):2201-2208
In this study, divalent manganese ions [Mn(II)] were substituted a part of divalent iron ions [Fe(II)] present in Fe oxyhydroxides to prepare novel composites (Mn@Feox). The composites were prepared by (1) simultaneous hydrolysis of Fe(II) and Mn(II), and (2) rapid oxidation with H2O2. The resulting Mn@Feox prepared with different molar ratios of Fe and Mn was characterized and evaluated for their abilities to adsorb arsenic species [As(III) and As(V)] in aqueous solution. X-ray diffraction and field emission transmission electron microscope analyses revealed Mn@Feox has a δ-(Fe1?x, Mnx)OOH-like structure with their mineralogical properties resembling those of feroxyhyte (δ-FeOOH). The increase in Mn substitution in Mn@Feox enhanced the oxidative ability to oxidize As(III) to As(V), but it decreased the adsorption capacity for both arsenic species. The optimal Mn/Fe molar ratio that could endow oxidation and magnetic capabilities to the composite without significantly compromising As adsorption capability was determined to be 0.1 (0.1Mn@Feox). The adsorption of As(III) on 0.1Mn@Feox was weakly influenced by pH change while As(V) adsorption showed high dependence on pH, achieving nearly complete removal at pH?<?5.7 but gradual decrease at pH?>?5.7. The adsorption kinetics and isotherms of As(III) and As(V) showed good conformity to pseudo-second-order kinetics model and Freundlich model, respectively. 相似文献
6.
十二烷基磺酸钠溶剂效应的理论研究 总被引:1,自引:1,他引:0
在气相、苯、乙醇和水中,用自洽反应场(self consistent reaction field)模型,在Hartree-Fock(HF)/lanl2dz的水平上对十二烷基磺酸钠的初始构象进行全几何优化、频率计算和NBO分析,研究十二烷基磺酸钠的几何结构、电荷分布和能量性质,并对结果进行比较。结果表明,十二烷基磺酸钠的负电荷主要集中在氧原子上,随着溶剂极性的增加,负电荷由在气相中的相差0.121 84到水中的0.012 14,分布趋于分散;LUMO轨道主要集中在非烷基端,且溶剂极性越大,电子云分布越分散,表面活性越强;偶极矩由气相中的7.346 50 Debye增大到水中的11.157 40 Debye;LUMO的能量由气相中的0.000 47a.u.增加到水中的0.053 67a.u.,使十二烷基磺酸钠跃迁时降低的能量增多,水中的构象更稳定。 相似文献
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8.
Intelligence has been an object of study for a long time. Different architectures try to capture and reproduce these aspects into artificial systems (or agents), but there is still no agreement on how to integrate them into a general framework. With this objective in mind, we propose an architectural methodology based on the idea of intentional configuration of behaviors. Behavior‐producing modules are used as basic control components that are selected and modified dynamically according to the intentions of the agent. These intentions are influenced by the situation perceived, knowledge about the world, and internal variables that monitor the state of the agent. The architectural methodology preserves the emergence of functionality associated with the behavior‐based paradigm in the more abstract levels involved in configuring the behaviors. Validation of this architecture is done using a simulated world for mobile robots, in which the agent must deal with various goals such as managing its energy and its well‐being, finding targets, and acquiring knowledge about its environment. Fuzzy logic, a topologic map learning algorithm, and activation variables with a propagation mechanism are used to implement the architecture for this agent. 相似文献
9.
This paper develops an analysis for predicting the normal stress and interfacial shearing stress distribution along a single reinforcing fibre of a randomly oriented chopped-fibre composite, such as sheet moulding compound (SMC), from a knowledge of the constituent properties and the length-to-diameter ratio of the fibres. The analysis is useful in analysing the tensile strength of SMC, and as a guide to increasing the tensile strength by altering the elastic characteristics. The model is based on a generalized shear-lag analysis. Numerical values of the normal stress and interfacial shearing stress are presented as functions of various parameters. It is observed that the maximum normal stress occurs at the middle of the fibre and the maximum shear stress occurs at the end. The analysis is restricted to loading which does not result in buckling of the fibre; i.e., axial loads on the fibre can be at most only slightly compressive.List of symbols
a
f
Ratio of the fibre length to diameter (aspect ratio, l
f/d
f)
-
E
a
Young's modulus of the composite (defined in Equation 21)
-
E
f
Young's modulus of the fibre material
-
E
m
Young's modulus of the matrix material
-
G
f
Shear modulus of the fibre material
-
G
m
Shear modulus of the matrix material
-
l
Half the length of the matrix sheath which surrounds the fibre
-
l
f
Half of the length of the fibre
-
Q
Defined in Equation 14.
-
R
Ratio of the length of the fibre to the matrix in a representative volume element; a parameter 0R[(1/V
f–1) ]
-
r
a
Radius of the composite body (we assume r
ar
m, r
f)
-
r
f
Radius of the fibre
-
r
m
Radius of the matrix sheath which surrounds the fibre
-
u
a
Displacement of the composite along the fibre direction
-
u
f
Displacement of the fibre along the fibre direction
-
V
f
Fibre volume fraction
- (XYZ)
Co-ordinate system with Z-axis parallel to the direction of the applied load (Fig. 1a)
- (xyz)
Co-ordinate system which is rotated by about the X-axis (Fig. 1a)
- (¯x¯y¯z)
Co-ordinate system which is rotated by about the z-axis (Fig. 1b)
-
Fibre orientation angle measured from the Z-axis
-
m
Engineering shear strain in the matrix
-
Defined in Equation 8
-
Polar angle measured from the x–z plane
-
Defined in Equation 9
-
Applied normal stress
-
a
Normal stress in the composite along the fibre axis
-
f
Normal stress in the fibre along the fibre axis
-
m
Normal stress in the matrix along the fibre axis
-
Shear stress on the fibre—matrix interface 相似文献
10.
Dong Ho Bae Chul Han Kim Seon Young Cho Jung Kyun Hong Chon Liang Tsai 《Journal of Mechanical Science and Technology》2002,16(9):1054-1064
Numerical prediction of welding-induced residual stresses using the finite element method has been a common practice in the
development or refinement of welded product designs. Various researchers have studied several thermal models associated with
the welding process. Among these thermal models, ramp heat input and double-ellipsoid moving source have been investigated.
These heat-source models predict the temperature fields and history with or without accuracy. However, these models can predict
the thermal characteristics of the welding process that influence the formation of the inherent plastic strains, which ultimately
determines the final state of residual stresses in the weldment. The magnitude and distribution of residual stresses are compared.
Although the two models predict similar magnitude of the longitudinal stress, the double-ellipsoid moving source model predicts
wider tensile stress zones than the other one. And, both the ramp heating and moving source models predict the stress results
in reasonable agreement with the experimental data. 相似文献