全文获取类型
收费全文 | 2622篇 |
免费 | 45篇 |
国内免费 | 5篇 |
专业分类
电工技术 | 76篇 |
综合类 | 2篇 |
化学工业 | 461篇 |
金属工艺 | 65篇 |
机械仪表 | 47篇 |
建筑科学 | 37篇 |
能源动力 | 71篇 |
轻工业 | 171篇 |
水利工程 | 6篇 |
石油天然气 | 3篇 |
无线电 | 338篇 |
一般工业技术 | 361篇 |
冶金工业 | 815篇 |
原子能技术 | 65篇 |
自动化技术 | 154篇 |
出版年
2023年 | 7篇 |
2022年 | 18篇 |
2021年 | 35篇 |
2020年 | 19篇 |
2019年 | 17篇 |
2018年 | 30篇 |
2017年 | 15篇 |
2016年 | 24篇 |
2015年 | 26篇 |
2014年 | 33篇 |
2013年 | 102篇 |
2012年 | 56篇 |
2011年 | 77篇 |
2010年 | 72篇 |
2009年 | 56篇 |
2008年 | 94篇 |
2007年 | 65篇 |
2006年 | 72篇 |
2005年 | 73篇 |
2004年 | 81篇 |
2003年 | 63篇 |
2002年 | 63篇 |
2001年 | 55篇 |
2000年 | 53篇 |
1999年 | 66篇 |
1998年 | 292篇 |
1997年 | 211篇 |
1996年 | 133篇 |
1995年 | 83篇 |
1994年 | 79篇 |
1993年 | 82篇 |
1992年 | 44篇 |
1991年 | 37篇 |
1990年 | 41篇 |
1989年 | 28篇 |
1988年 | 27篇 |
1987年 | 32篇 |
1986年 | 19篇 |
1985年 | 31篇 |
1984年 | 37篇 |
1983年 | 23篇 |
1982年 | 28篇 |
1981年 | 31篇 |
1980年 | 27篇 |
1979年 | 21篇 |
1978年 | 16篇 |
1977年 | 15篇 |
1976年 | 28篇 |
1975年 | 9篇 |
1972年 | 7篇 |
排序方式: 共有2672条查询结果,搜索用时 15 毫秒
81.
The alumina–carbon composite fibers were obtained from poly[(acyloxy)aloxane] (PAA) with 3-ethoxypropanoic (EPA) and m-anisic acids (m-AA) legands. This preceramic polymer can be dissolved in p-xylene-methanol-EPA mixed solvent, and the concentrated solution exhibited an excellent spinnability. During the pyrolysis and sintering processes, aliphatic carboxylate in the side groups was easily decomposed and eliminated. The aromatic carboxylate, however, seems to be converted and migrated to a carbon domain in the alumina matrix into which aloxane repetition was converted. The fibers pyrolyzed up to 800 and 1000°C have electrical conductivities that monotonically increase with increasing temperature. The fiber pyrolyzed up to 1200°C showed the electrical conductivity in a rather complicated manner. 相似文献
82.
Tomoko Okuyama Jun Shirakawa Kazuki Tajima Yoko Ino Heidrun Vethe Yu Togashi Mayu Kyohara Ryota Inoue Daisuke Miyashita Jinghe Li Nozomi Goto Taiga Ichikawa Shingo Yamasaki Haruka Ohnuma Rie Takayanagi Yayoi Kimura Hisashi Hirano Yasuo Terauchi 《International journal of molecular sciences》2020,21(21)
83.
84.
Bo Zhu Jianchun Li Yong He Hideki Yamane Yoshiharu Kimura Haruo Nishida Yoshio Inoue 《应用聚合物科学杂志》2004,91(6):3565-3573
The phase behaviors for the blends of poly(3‐hydroxypropionate) (PHP), poly(L ‐lactide) (PLLA), poly(D ‐lactide) (PDLA), and poly(D,L ‐lactide) (PDLLA) with catechin were investigated by differential scanning calorimetry. In PLLA/catechin, PDLA/catechin, and PDLLA/catechin blends, two glass transitions were detected when the catechin content was ≥40 wt %, whereas in PHP/catechin blends only one glass transition was observed over the whole range of blend compositions. The former and the latter results should reflect the inhomogeneous and the homogeneous nature of the blends, respectively, in the amorphous phase. These different phase behaviors should arise from the differences in the chemical structures between PHP and PLLA/PDLA/PDLLA, which dominates the strength and the number of intermolecular hydrogen‐bonding interactions between the ester carbonyl groups of polyesters and the phenol groups of catechin. As detected by FTIR spectroscopy, in comparison with PHP, the steric hindrance of side‐chain methyl groups of PLLA, PDLA, and PDLLA might restrain the formation of hydrogen bonds between their ester carbonyl groups and the phenol hydroxyl groups of catechin, even weakening the strength of such hydrogen bonds. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3565–3573, 2004 相似文献
85.
T. Natori Y. Takemura H. Harada K. Abe A. Ohashi M. Kimura T. Yamaguchi T. Okubo S. Uemura 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2012,87(10):1466-1472
BACKGROUND: In this study, the inductive effect of salinity on nitrite accumulation in a down‐flow hanging sponge (DHS) reactor, developed as a novel and cost‐effective wastewater treatment process, was evaluated by conducting a long‐term continuous experiment lasting more than 1400 days. RESULTS: The influent salinity was controlled by adding NaCl at concentrations ranging from 0 to 25 g Cl? L?1. The effluent nitrite increased with increases in salinity, i.e. the fraction of nitrite to total nitrogen in the effluent increased from 1.6% at 0 g Cl? L?1 to 87.6% at 25 g Cl? L?1. Fluorescence in situ hybridization (FISH) analysis revealed that as salinity increased, the nitrifying bacterial community in the DHS changed markedly at the species level. In particular, the dominant nitrite‐oxidizing bacteria changed from Nitrospira‐sublineage I at 0 g Cl? L?1 to Nitrobacter spp. at 15 g Cl? L?1. At 25 g Cl? L?1, no nitrite‐oxidizing bacteria were detected. CONCLUSION: Our findings suggest that the DHS reactor is suitable for cost‐effective nitrite production processes and that salinity control using NaCl is an effective method for inducing nitrite accumulation. Copyright © 2012 Society of Chemical Industry 相似文献
86.
Copoly(amide-ethers) containing two types of tertiary amine units were made as antistatic modifiers for poly(ethylene terephthalate) (PET) fibers. The filaments of the copolymers were melt-spun and reacted with three alkylating agents in order to quaternize the tertiary amine into a sulfo-betaine, a carbobetaine, and an ammonium ion. The apparent electric resistivity of the filaments was greatly reduced by this reaction, being in the range of 106 to 108 Ω/cm. However, because these quaternized copolymers incurred decomposition during blend spinning with PET, a blend PET fiber containing one type of copoly(amide-ether) was melt-spun and subjected to quaternization of the amino groups as well as to surface crosslinking with various alkylating and epoxy agents. The quaternized blend fibers obtained showed improved antistatic properties compared with the original blend fiber. Particularly, the fibers crosslinked with epoxy compounds were found to have the best antistatic properties that had ever been attained with this type of modification. The antistatic properties were retained even after dyeing, because both hydrophilic and ionic groups had been effectively immobilized on the surface. Since this quaternization and crosslinking could be conducted on-line with spinning and drawing within a short reaction time, this modification technique is called “spin-finishing method”, which should be superior to the conventional methods in terms of cost performance and productivity. 相似文献
87.
Yoshiyuki Sano Marcekazu Konda Chan Woo Lee Yoshiharu Kimura Takeo Saegusa 《大分子材料与工程》1997,251(1):181-191
A new technique for imparting antistatic properties to poly(ethylene terephthalate) (PET) fiber has been developed. In this technique, blend polyester fibers containing poly(ethylene terephthalate/5-sulfoisophthalate) (SIP-PET) were prepared by blend spinning and then treated with various cationic surfactants in the process of dyeing. The surfactants could effectively be immobilized on the fiber as the counter cations of the sulfonate groups of the 5-sulfoisophthalate (SIP) units and aid the release of static electrons formed in the fiber. Thus, the half-life time (t1/2) of leakage of static charge and the surface resistivity (Rs) of the blend PET fibers became much lower after treating. The best result was obtained with a methylated quaternary ammonium salt of a stearylamine-ethylene oxide (EO) adduct or hydrochloride of a laurylamine-EO adduct as the surfactant of which the number of EO units was around ten. Even after five washing cycles the t1/2 value of the fibers treated with these surfactants was kept lower than 30 s with the Rs value maintained in the order of 1013 Ω cm-2. Therefore, the present technique could be useful for practical production of polyester fibers with “semi-permanent” antistatic properties which can be recovered by re-treatment even if they were lost. 相似文献
88.
Akihiko Ito Jun Endo Teiichi Kimura Takashi Goto 《Surface & coatings technology》2010,204(23):3846-246
Y-Si-O films were prepared by laser chemical vapor deposition (LCVD) with a Nd:YAG laser using TEOS (tetraethyl orthosilicate) and Y(dpm)3 precursors. The effects of laser power (PL), deposition temperature (Tdep) and total chamber pressure (Ptot) on the phase, microstructure and deposition rate of Y-Si-O films were investigated. At PL < 102 W (Tdep < 1140 K), amorphous Y-Si-O films were obtained independent of Ptot. At Ptot = 0.6 kPa, mixture phase films of Y2SiO5 (the X1 phase) and Y2Si2O7 (the α, β, δ and y phases) were obtained at PL = 102 W (Tdep = 1210 K), while single phase X1-Y2SiO5 films were prepared at PL > 139 W (Tdep > 1280 K). Y2Si2O7 mixture phase films were obtained at Ptot = 3.5 kPa and Y2Si2O7 and Y2SiO5 (the X2 phase) mixture phase films were obtained at Ptot = 7.5 kPa independent of Tdep. Amorphous Y-Si-O films showed a dense, glassy microstructure. Faceted columnar grains grew on the Y-Si-O films at Ptot = 0.6 kPa, whereas rounded cauliflower-like grains grew at Ptot = 7.5 kPa. The Rdep increased with increasing PL and Tdep and reached a maximum of 430 μm h−1 at Ptot = 0.6 kPa, PL = 186 W and Tdep = 1310 K. 相似文献
89.
The n-type thermoelectric properties of the half-Heusler compound ZrNiSn can be converted to p-type by the addition of Co and Ir. We found that Co and Ir atoms preferably occupy the vacancy sites instead of substituting at Ni sites. This implies that the phase stability of the compound gradually changes towards that of the Heusler compound Zr(Ni,M)2Sn, where M is Co and/or Ir. The occupation of vacancy sites by Co and Ir atoms leads to a drastic reduction in lattice thermal conductivity owing to the enhancement of phonon scattering by the solid solution effect. 相似文献
90.
Membrane processing of used frying oils 总被引:2,自引:0,他引:2
R. Subramanian K. E. Nandini P. M. Sheila A. G. Gopalakrishna K. S. M. S. Raghavarao M. Nakajima T. Kimura T. Maekawa 《Journal of the American Oil Chemists' Society》2000,77(3):323-328
Studies were conducted with used frying oils in a flat membrane batch cell using five different types of polymeric membranes
to decrease the soluble degradation products. During membrane processing, triglycerides permeated preferentially compared
to the majority of the polar compounds including oxidation products, polymers, and color compounds. Two of the composite membranes,
NTGS-AX and NTGS-2200, selectively rejected polar compounds and oxidation products to the extent of 25–48% and 24–44% respectively.
The reduction in Lovibond color values (5R+Y) was in the range of 83–93%. The viscosity of the used frying oil was reduced
to the extent of 22%. The composite membranes were effective in reducing the soluble impurities, as well as insoluble particulates,
without causing any undesirable changes to the oil. The membrane process appears to improve the life of used frying oils and
does not have the disadvantages associated with the active filtration systems, however, for commercial application the permeate
flux needs to be improved considerably. 相似文献