全文获取类型
收费全文 | 2715篇 |
免费 | 25篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 88篇 |
综合类 | 3篇 |
化学工业 | 511篇 |
金属工艺 | 94篇 |
机械仪表 | 77篇 |
建筑科学 | 35篇 |
能源动力 | 141篇 |
轻工业 | 126篇 |
水利工程 | 10篇 |
石油天然气 | 6篇 |
无线电 | 351篇 |
一般工业技术 | 445篇 |
冶金工业 | 669篇 |
原子能技术 | 45篇 |
自动化技术 | 150篇 |
出版年
2023年 | 12篇 |
2021年 | 40篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 17篇 |
2017年 | 23篇 |
2016年 | 31篇 |
2015年 | 28篇 |
2014年 | 47篇 |
2013年 | 116篇 |
2012年 | 71篇 |
2011年 | 107篇 |
2010年 | 91篇 |
2009年 | 88篇 |
2008年 | 100篇 |
2007年 | 98篇 |
2006年 | 75篇 |
2005年 | 59篇 |
2004年 | 62篇 |
2003年 | 102篇 |
2002年 | 71篇 |
2001年 | 63篇 |
2000年 | 44篇 |
1999年 | 82篇 |
1998年 | 313篇 |
1997年 | 176篇 |
1996年 | 111篇 |
1995年 | 70篇 |
1994年 | 84篇 |
1993年 | 71篇 |
1992年 | 38篇 |
1991年 | 34篇 |
1990年 | 45篇 |
1989年 | 33篇 |
1988年 | 23篇 |
1987年 | 26篇 |
1986年 | 25篇 |
1985年 | 31篇 |
1984年 | 23篇 |
1983年 | 31篇 |
1982年 | 16篇 |
1981年 | 14篇 |
1980年 | 23篇 |
1979年 | 13篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 21篇 |
1975年 | 10篇 |
1974年 | 10篇 |
1972年 | 6篇 |
排序方式: 共有2751条查询结果,搜索用时 265 毫秒
61.
Blending a crosslinked high‐density polyethylene (xHDPE) enhances melt strength and strain hardening behavior in elongational viscosity of high‐density polyethylene (HDPE) to a great degree. Gel fraction of xHDPE has a stronger effect on the strain hardening than sol fraction, although sol fraction also enhances the strain hardening to some degree. Further, the xHDPE crosslinked by peroxide in a compression mold exhibits more pronounced effect than xHDPE by radiation, which is attributed to the difference in the amount of the gel fraction. The xHDPE, which enhances the strain hardening, has sparse crosslink points in the network. Moreover, it was found from linear viscoelastic measurements, such as oscillatory modulus and relaxation modulus, that the xHDPE is characterized as a critical gel, which was also supported by the result of tensile testing. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 73–78, 2002 相似文献
62.
S. Yamaguchi Y. W. Leong T. Tsujii M. Mizoguchi U. S. Ishiaku H. Hamada 《应用聚合物科学杂志》2005,98(1):294-301
A previous study has shown that the adhesion between the film and substrate of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate was evident with the increases in barrel temperature and injection holding pressure. In this second part of the research work, the crystallinity at the interfacial region (i.e., region between the film and the injected substrate) was extensively studied using FTIR imaging, polarized light microscopy, and DSC in an attempt to determine the level of influence that crystallinity has on the interface and bulk mechanical properties. Consequently, a more thorough and clearer picture of the influence of the inserted film on the interfacial crystallinity and subsequently the substrate mechanical properties, such as peel strength and impact strength, has been revealed. The initial proposition that crystallinity could enhance film–substrate interfacial bonding has been confirmed, judging from the higher peel strength with increasing crystallinity at the interfacial region. Nevertheless, the change in crystallinity was not only confined to the interfacial region. With the film acting as heat‐transfer inhibitor between the injected resin and the mold wall, the total crystal structure of the substrate was substantially altered, which subsequently affected the bulk mechanical properties. The lower impact strength of film‐insert injection‐molded samples compared to that of samples without film inserts provided evidence of how the film could impart inferior properties to the substrate. The difference in cooling rate between the substrate and film might also cause other defects such as warpage and/or residual stress build‐up within the product. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 294–301, 2005 相似文献
63.
Tamotsu Tanaka Kouji Ikita Tetsuji Ashida Yoshiaki Motoyama Yasunori Yamaguchi Kiyoshi Satouchi 《Lipids》1996,31(11):1173-1178
The effects of growth temperature on the fatty acid compositions of the phosphatidylcholine (PC), phosphatidylethanolamine
(PE), and total lipid (TL) fractions of the free-living nematodeCaenorhabditis elegans were investigated. A reduction in growth temperature from 25 to 15°C caused the proportions of eicosapentaenoic acid (20∶5n-3)
to increase from 23.6 to 32.5% in the PC, from 7.4 to 10.8% in the PE, and from 12.9 to 19.9% in the TL fractions. Conversely,
the levels of dihomo-γ-linolenic acid (20∶3n-6) and arachidonic acid (20∶4n-6) in these phospholipid fractions and the TL
fraction both decreased with decreasing growth temperature. Analysis of the positional distribution of fatty acids in the
PC fraction revealed that the change in the composition of C20 polyunsaturated fatty acid was obvious in positionsn-2. Lowering the growth temperature induced an increase in the level of the diacyl subclass of PE from 58% at 25°C to 71%
at 15°C, with a concomitant decrease in the levels of the alkylacyl and alkenylacyl subclass of PE ofC. elegans. These changes observed in the phospholipids ofC. elegans might be one mechanism for adaptation to low temperature. Lipids 31, 1173–1178 (1996). 相似文献
64.
Shingo Hirano Masaru Yoshinaka Ken Hirota Osamu Yamaguchi 《Journal of the American Ceramic Society》1996,79(1):171-176
In the ZrO2 -Cr2 O3 system, metastable t -ZrO2 solid solutions containing up to 11 mol% Cr2 O3 crystallize at low temperatures from amorphous materials prepared by the hydrazine method. The lattice parameter c decreases linearly from 0.5149 to 0.5077 nm with increased Cr2 O3 content, whereas the lattice parameter a is a constant value ( a = 0.5077 nm) regardless of the starting composition. At higher temperatures, transformation (decomposition) of the solid solutions proceeds in the following way: t (ss)→ t (ss) + m + Cr2 O3 → m + Cr2 O3 . Above 11 mol% Cr2 O3 addition, c-ZrO2 phases are formed in the presence of Cr2 O3 . The t -ZrO2 solid solution powders have been characterized for particle size, shape, and surface area. They consist of very fine particles (15–30 nm) showing thin platelike morphology. Dense ZrO2 (3Y)-Cr2 O3 composite ceramics (∼99.7% of theoretical) with an average grain size of 0.3 μm have been fabricated by hot isostatic pressing for 2 h at 1400°C and 196 MPa. Their fracture toughness increases with increased Cr2 O3 content. The highest K Ic value of 9.5 MPa·;m1/2 is achieved in the composite ceramics containing 10 mol% Cr2 O3 . 相似文献
65.
Masaaki Takehisa Hiromasa Watanabe Hirondo Kurihara Kouichi Yamaguchi Hayato Nakajima Toshiaki Yagi Terutaka Watanabe Takanobu Sugo Takeshi Suwa Shinsaku Maruyama Atsuro Kodama Takeo Shimada Yoshio Maruyama Masamichi Tohei Takeshi Wada Sueo Machi 《应用聚合物科学杂志》1979,24(8):1831-1844
Radiation-induced polymerization of ethylene using aqueous tert-butyl alcohol as medium was carried out in a large-scale pilot plant with a 50-liter central source-type reactor at a pressure of 105 to 395 kg/cm2, temperature of 30° to 80°C, mean dose rate of 4.5 × 104 to 1.9 × 105 rads/hr, ethylene feed rate of 5.5 to 23.5 kg/hr, and medium feed rate of 21 to 102 l./hr. The space–time yield and molecular weight of the polymer were in the range of 4.7 to 16.8 g/l.-hr and 1.3 × 104 to 8.9 × 104, respectively. The space–time yield and molecular weight increased with mean residence time at 30°C, whereas at 80°C they became almost independent of the time. The space–time yield increased with pressure and dose rate, slightly decreased with temperature, and was maximum at ethylene molar fraction of 0.5. The polymer molecular weight increased with pressure and ethylene molar fraction, and decreased with dose rate and temperature. The total amount of deposited polymer on the reactor wall, source case wall, and scraping blades was usually less than 1 kg, which was negligibly small for the analysis of polymerization. Continuous discharge of the polymer slurry and production of fine-powder polyethylene were successfully carried out. In the central source-type reactor, a dose rate of 1.9 × 105 rads/hr was obtained with a 60Co source of ca. 12 kCi. 相似文献
66.
Y. Nakama Y. Shiojima Y. Takeshita M. Yamaguchi 《Journal of the American Oil Chemists' Society》1997,74(7):803-808
The formation of a complex, composed of lauroamphoglycinate (LG), oleic acid (OA) and water, was investigated, and this system
was applied to emulsification. The complex was formed in the water-rich area (more than 90% in this system) at a molar ratio
of OA to LG from 1 to 3, where two-phase systems of water and the complex existed. The interaction between LG and OA, both
in the aqueous solution and at the interface of liquid paraffin dissolving the OA and LG solution, was studied by pH measurements
and interfacial tension measurements, respectively. The results implied that LG and OA were linked stoichiometrically, both
in aqueous solution and at the interface, and formed complexes. X-ray diffraction patterns and the strong hydrophobicity showed
that the equimolar complex composed of LG, OA, and water was a liquid crystal with a reversed hexagonal structure. The reversed
hexagonal liquid crystal was capable of solubilizing a certain amount of liquid paraffin in its alkyl group parts while maintaining
its hexagonal structure. These results suggest the possibility to prepare a W/O-type emulsion by using the liquid crystal
formed by LG, OA, partial liquid paraffin, and water as the continuous phase. The authors could obtain a stable W/O emulsion
without coalescence of the water droplets that contained a substantial amount of water (approximately 90%). Furthermore, various
types of emulsions, O/W, W/O, W/O/W, could be prepared by changing the ratio of LG and OA. 相似文献
67.
The formation of lead tantalates in the PbO-rich region is studied using the powders prepared by the simultaneous hydrolysis of lead and tantalum alkoxides. Cubic 3PbO · 2Ta2O5 solid solutions crystallize at low temperatures from amorphous materials between 60 and 75 mol% PbO. The lattice parameter,a, increases linearly from 1.0545 to 1.0705 nm with increasing PbO. At higher temperatures the solid solutions above 66.67 mol% PbO are transformed into those of rhombohedral 2PbO · Ta2O5. Rhombohedral 5PbO · 2Ta2O5 is formed at 850 to 900 °C by transformation of 2PbO·Ta2O5 solid solution corresponding to 71.43 mol% PbO. The existence of previously reported 3PbO·Ta2O5 is not confirmed. 相似文献
68.
Panitha Phulkerd Atsuro Yamazaki Shohei Iwasaki Masayuki Yamaguchi 《Polymer Engineering and Science》2021,61(2):367-378
In this study, polypropylene (PP) films containing the β nucleating agent, N,N′-dicyclohexyl-2,6-naphthalenedicarboxamide, were prepared using PP with three different molecular weights (low, medium, and high) by extrusion process with T-shaped die. The structure and morphology of the films were studied after stretching. It was found that a unique molecular orientation, in which both the c-axis and crystalline lamellae were oriented perpendicular to the flow direction, was formed in all undrawn film samples, irrespective of the molecular weights of the PP. In the PP sheets stretched in the machine direction, the low-molecular-weight sample containing the nucleating agent exhibited brittle properties owing to a lack of tie chains in the stretching direction. In contrast, cavitation was prominent in the medium (M-PP)- and high (H-PP)-molecular-weight samples. Notably, M-PP containing the nucleating agent, with a high degree of molecular orientation, promoted the formation of a large number of voids. In H-PP containing the nucleating agent, the presence of numerous tie chains inhibited cavitation, resulting in fewer voids. The experimental results demonstrated the influence of the molecular weight on the void structure, which will be useful in the field of microporous membranes. 相似文献
69.
M. A. Hassan N. Takakura K. Yamaguchi 《International Journal of Machine Tools and Manufacture》2003,43(6):637-646
A new process on friction aided deep drawing has been developed in which a metal blank-holder divided into eight fan-shaped segments is used instead of an elastomer ring used in the Maslennikov process. This blank holding device consists of four drawing segments and four small wedges, which can move radially in- and out-wards under a certain blank-holding pressure. The drawing process can be efficiently performed using an assistant punch, which partially supports the deformation of the blank as well as improving the shape and dimensional accuracy of the drawn cup. Deep drawing experiments have been done using soft aluminum sheets of 0.5 and 1.0 mm in thickness to understand the main features of the proposed drawing process. Theoretical analyses based on the energy and slab methods have also been conducted to study the effect of main process parameters on the minimum blank holding pressure required for the onset of deformation, and to obtain the other optimum working conditions. The possibility of the new process has been confirmed by producing deep and successful cups with a drawing ratio of 4.0, although the number of drawing operations is still high. 相似文献
70.
Titanium carbide nano-fiber was synthesized by self-propagating high temperature synthesis (SHS) method. The final products
after the SHS reaction were titanium carbide containing excess carbon and metallic titanium, which were removed by additional
leaching process. TEM observation revealed that the average diameter is about 20 nm. Neutron diffraction analysis was carried
out to study non-stoichiometric number of the titanium carbide. The non-stoichiometric numbers of the titanium carbide were
0.89–0.94. The Rietveld refinement of each patterns converged to good agreement (÷2=0.49–1.34). The formation mechanism of
the carbide is related to a liquid-solid reaction including the preferential diffusion process of carbon atom into liquid
titanium.
This article is based on a presentation made in the 2002 Korea-US symposium on the “Phase Transformations of Nano-Materials,”
organized as a special program of the 2002 Annual Meeting of the Korean Institute of Metals and Materials, held at Yonsei
University, Seoul, Korea on October 25–26, 2002. 相似文献