全文获取类型
收费全文 | 611篇 |
免费 | 23篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 44篇 |
综合类 | 5篇 |
化学工业 | 215篇 |
金属工艺 | 15篇 |
机械仪表 | 7篇 |
建筑科学 | 36篇 |
能源动力 | 11篇 |
轻工业 | 46篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 29篇 |
一般工业技术 | 138篇 |
冶金工业 | 7篇 |
原子能技术 | 15篇 |
自动化技术 | 74篇 |
出版年
2023年 | 2篇 |
2022年 | 2篇 |
2021年 | 11篇 |
2020年 | 3篇 |
2019年 | 12篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2016年 | 14篇 |
2015年 | 10篇 |
2014年 | 19篇 |
2013年 | 25篇 |
2012年 | 23篇 |
2011年 | 32篇 |
2010年 | 24篇 |
2009年 | 29篇 |
2008年 | 36篇 |
2007年 | 18篇 |
2006年 | 33篇 |
2005年 | 31篇 |
2004年 | 27篇 |
2003年 | 22篇 |
2002年 | 19篇 |
2001年 | 14篇 |
2000年 | 10篇 |
1999年 | 16篇 |
1998年 | 6篇 |
1997年 | 11篇 |
1996年 | 14篇 |
1995年 | 6篇 |
1994年 | 12篇 |
1993年 | 9篇 |
1992年 | 3篇 |
1991年 | 7篇 |
1990年 | 8篇 |
1989年 | 5篇 |
1988年 | 7篇 |
1987年 | 9篇 |
1986年 | 14篇 |
1985年 | 8篇 |
1984年 | 7篇 |
1983年 | 10篇 |
1982年 | 11篇 |
1981年 | 5篇 |
1980年 | 10篇 |
1979年 | 11篇 |
1978年 | 6篇 |
1977年 | 5篇 |
1975年 | 3篇 |
1973年 | 3篇 |
1971年 | 2篇 |
排序方式: 共有645条查询结果,搜索用时 31 毫秒
21.
Takeshi Kikutani J. Radhakrishnan Sadaaki Arikawa Akira Takaku Norimasa Okui Xia Jin Fumio Niwa Yosuke Kudo 《应用聚合物科学杂志》1996,62(11):1913-1924
High-speed bicomponent spinning of poly(ethylene terephthalate)(PET)(core) and poly-propylene (PP) (sheath) was carried out and the structure development in the individual components, PET and PP, was investigated. The orientation and crystallinity development in the PET component was enhanced as compared to that of the single-component spinning while the PP component remained in a low orientation state and had a pseudohexagonal crystal structure even at high take-up speeds. To clarify the mutual interaction between the two components in bicomponent spinning, a semiquantitative numerical simulation was performed. The simulation results obtained using the Newtonian fluid model showed that the solidification stress in the PET component was enhanced while that of the PP component was decreased in comparison with the corresponding single-component spinning. This is due to the difference in the temperature dependence of their elongational viscosity. Simulation with an upper-convected Maxwell model as the constitutive equation suggested that significant stress relaxation of the PP component can occur in the spinline if the PET component solidifies earlier than does PP. Based on the structural characterization results, and the simulation results, it was concluded that the difference in the activation energy of the elongational viscosity and solidification temperature between the two polymers are the main factors influencing the mutual interaction in the bicomponent spinning process. © 1996 John Wiley & Sons, Inc. 相似文献
22.
Chemiluminescence (CL) analysis was used for determining the oxidation layer formed by the irradiation of polypropylene for medical supplies. The depth of the oxidation layer from the surface depended on dose rate and increased with decreasing dose rate. The oxidation occurred remarkably at a region near the surface area of the film where the diffusion of oxygen is more sufficient. On the contrary, there was very little oxidation in the interior portion. The oxidation layers of polypropylene samples irradiated with electron beam showed U-shaped profiles in the cross-section of film as did as a sample irradiated with γ-rays. However, the degree of oxidation by irradiation with electron beam was very small; CL intensity at the surface area was only one-third that for the γ-irradiated samples. 相似文献
23.
Monodispersed spherical β-SiC powder was synthesized by heating spherical gel powder derived from the hydrolysis of a mixture of phenyltriethoxysilane and tetraethyl orthosilicate. The solution was prepared in a beaker and hydrolyzed by NH4 OH without stirring. The monodispersed spherical gel powder of submicrometer size was obtained when the added amount of NH4 OH was greater than 16 moles per mole of silane plus alkoxide, and it became monodispersed spherical β-SiC powder by heat-treating at 1500°C for 4 h in an Ar atmosphere. The SiC content of the powder was 92.6 wt%. 相似文献
24.
The degradability under various conditions of five kinds of radiation-vulcanized natural rubber latex (RVNRL) films was studied. The treatments were leaching in methanol, leaching in 1% ammonia solution, mixing with tris(nonylated phenyl)phosphite (TNP) antioxidant, blending with poly(methyl methacrylate) (PMMA), and grafting with PMMA, Comparisons were made with sulfur-vulcanized natural rubber latex (SVNRL) film. RVNRL films SVNRL film can be kept for a long time when indirectly exposed to sunlight at room temperature. However, the former degraded much more rapidly than did the latter. TNP was found to be very suitable as an antioxidant to prolong the life of RVNRL films under dry conditions. PMMA, either blended or grafted with RVNRL, was ineffective in the prevention of deterioration of RVNRL films. The rapid degradation of RVNRL products could be an advantage over SVNRL products in environmental and wildlife conservation. © 1994 John Wiley & Sons, Inc. 相似文献
25.
Fumio Sanda 《Polymer》2004,45(3):849-854
Polyacetylenes having carboxyl and/or amino groups in the side chain were synthesized by the polymerization of N-(2-propynyloxycarbonyl)-l-alanine (1) and l-alanine N-propargylamide (2) catalyzed with a rhodium cation complex. Poly(10.5-co-20.5) exhibited a larger CD signal than the homopolymers. The polymer mixtures obtained by the polymerization of 1 in the presence of poly(2), and those obtained by the polymerization of 2 in the presence of poly(1) showed specific rotations larger than calculated. The polymerization of propargylamine in the presence of poly(1) did not exhibit significant effect, while the polymer mixtures obtained by the polymerization of propiolic acid in the presence of poly(2) exhibited [α]D of positive sign, although poly(2) alone exhibited [α]D of negative sign. 相似文献
26.
The strength and deformation characteristics of sedimentary soft rock evaluated in relation to several large-scale researc and construction projects in Japan are reviewed.The elastic stiffiness at small non-linearity due to strain and pressure level,and viscous properties are described.The elastic stiffness from triaxial tests using high-quality core samples while measuring stresses and strains accurately is basically the same as the corresponding value from field shear wave velocity.It is necessary to take into account the dependency or stiffness on shear and pressure level,which could be evaluated by relevant laboratory stress-strain tests while referring to results trom relevant field loading tests.Loading rate effects due to the material viscous properties could be simulated by a non-linear three-component model. 相似文献
27.
通过仿生自组装法在室温下制备了纳米碳酸化羟基磷灰石/胶原(nCHAC)复合材料,并采用X射线衍射(XRD)、热分析(TGA)和透射电镜(TEM)进行了观察和分析.结果表明,该材料具有与天然骨相同的纳米尺度和胶原蛋白无机相,含有(2.8~14.7)w%的碳酸化HA成分;其显微结构是矿化的胶原纤维束,类似于天然骨的分级结构.揭示了碳酸化HA和胶原含量不同的复合材料中,具有微小差别的自组装单元.碳酸的百分含量影响矿物的晶体尺寸和胶原纤维的组装.因此,nCHAC复合材料是有前途的硬组织修复用材料,其所具有的特殊性能要归功于生物仿生制备出的nCHAC材料有与天然骨类似的成分和类似的微观结构. 相似文献
28.
Sang Jun Yoon Jae Goo Lee Hideo Tajima Akihiro Yamasaki Fumio Kiyono Tetsuya Nakazato Hiroaki Tao 《Journal of Industrial and Engineering Chemistry》2010,16(3):350-354
Extractions of five kinds of lanthanide metal ions by bis(2-ethylhexyl)phosphoric acid (DEHPA) with [1-Cn-3-methylimidazolium][PF6](Cn = C2, C4) or [1-butyl-4-methylpyridinium][PF6] were carried out under various DEHPA and HNO3 concentrations from 0 to 1 M and under different temperature conditions from 298 to 333 K. These results were compared with those using the conventional organic solvent, hexane, in terms of their distribution coefficient values. Under all of the conditions in this study, the ionic liquid system shows more than three times greater extractability for lanthanide compared to when hexane was used. The distribution coefficient of lanthanide ions decreased as the length of the alkyl chain increased from the ethyl to the butyl. In addition, the imidazolium cation generally shows a higher distribution coefficient compared to the pyridinium cation in an ionic liquid. The concentration ratio of lanthanides and DEHPA resulted in an extraction affinity transition for lanthanides. Also evaluated in this study were issues related to the selectivity associated with the lanthanide mixture and the dependency of the ionic radius during lanthanide extraction. 相似文献
29.
Takashi Matsumura Fumio Iida Takuya Hirose Masahiko Yoshino 《Journal of Materials Processing Technology》2012,212(12):2669-2677
A micro fabrication is presented to manufacture hydrophobic surfaces with micro-scale structures. Hydrophobicity is controlled with the shape and the alignment of micro pillars in the structure. The structures are manufactured in large areas at high production rates in the following processes: (1) the structure is fabricated on a tool by focused ion beam sputtering; (2) the reverse structure is formed on a metal plate by incremental stamping using the structured tool; and (3) the structure is transferred onto plastic plates by molding. A consecutive stamping is also proposed to fabricate several structures on a surface accurately with a structured tool, in which the moving pitch of the structured tool is numerically controlled. The effect of the surface topography on hydrophobicity is discussed with measuring contact angles on the structured surfaces in the water droplet tests. Hydrophobicity on the plastic plate is associated with the solid fraction on the structured surface based on the Cassie–Baxter model. A larger contact angle is observed for a smaller solid fraction of the surface. 相似文献
30.
Yasuhide Shindo Tomo Takeda Fumio Narita Nozomi Saito Shinya Watanabe Kazuaki Sanada 《Composites Science and Technology》2009,69(11-12):1904-1911
The purpose of this research is to characterize the cryogenic delamination growth behavior in woven glass fiber reinforced polymer (GFRP) composite laminates subjected to Mode II fatigue loading. Mode II fatigue delamination tests were performed at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K) using the four-point bend end-notched flexure (4ENF) test method, and the delamination growth rate data for the woven GFRP laminates were obtained. The energy release rate range was determined by the finite element method. Microscopic examinations of the specimen sections and fracture surfaces were also carried out. The present results are discussed to obtain an understanding of the fatigue delamination growth mechanisms in the woven GFRP laminates under Mode II loading at cryogenic temperatures. 相似文献