全文获取类型
收费全文 | 3001篇 |
免费 | 68篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 142篇 |
综合类 | 3篇 |
化学工业 | 881篇 |
金属工艺 | 74篇 |
机械仪表 | 113篇 |
建筑科学 | 45篇 |
能源动力 | 146篇 |
轻工业 | 262篇 |
水利工程 | 5篇 |
石油天然气 | 2篇 |
无线电 | 196篇 |
一般工业技术 | 488篇 |
冶金工业 | 396篇 |
原子能技术 | 127篇 |
自动化技术 | 199篇 |
出版年
2023年 | 23篇 |
2022年 | 30篇 |
2021年 | 53篇 |
2020年 | 26篇 |
2019年 | 30篇 |
2018年 | 52篇 |
2017年 | 36篇 |
2016年 | 71篇 |
2015年 | 40篇 |
2014年 | 84篇 |
2013年 | 179篇 |
2012年 | 114篇 |
2011年 | 161篇 |
2010年 | 122篇 |
2009年 | 156篇 |
2008年 | 168篇 |
2007年 | 137篇 |
2006年 | 139篇 |
2005年 | 114篇 |
2004年 | 89篇 |
2003年 | 106篇 |
2002年 | 98篇 |
2001年 | 58篇 |
2000年 | 55篇 |
1999年 | 70篇 |
1998年 | 151篇 |
1997年 | 96篇 |
1996年 | 79篇 |
1995年 | 52篇 |
1994年 | 45篇 |
1993年 | 49篇 |
1992年 | 28篇 |
1991年 | 27篇 |
1990年 | 13篇 |
1989年 | 21篇 |
1988年 | 17篇 |
1987年 | 24篇 |
1986年 | 22篇 |
1985年 | 33篇 |
1984年 | 28篇 |
1983年 | 20篇 |
1982年 | 19篇 |
1981年 | 18篇 |
1980年 | 13篇 |
1979年 | 22篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1976年 | 22篇 |
1973年 | 6篇 |
1972年 | 6篇 |
排序方式: 共有3079条查询结果,搜索用时 15 毫秒
31.
The anodic evolution of chlorine on the massive β-MnO2 doped with various amounts of Pd was investigated in acidic chloride solution. A second-order relation was found between the rate of the chlorine evolution reaction and the number of active Pd sites at the electrode surface. And it was confirmed that, in the relatively low doped electrodes, the active sites are more effectively dispersed on the surface with microscopic homogeneity. From the activation energies, it was also suggested that the reaction mechanism on the MnO2 doped with relatively small amounts of Pd is somewhat different from that on the pure PdO electrode. 相似文献
32.
Tetsuya Tanigami Kanna Kai Koji Tanaka Shuji Matsuzawa 《Journal of Inorganic and Organometallic Polymers》2003,13(4):237-253
Poly[bis(-phenoxyethoxy)phosphazene] [PBPEP] had been shown in our previous paper to be a very useful polymer for investigating the crystallization mechanism of polymers, as the crystallization rate of PBPEP is extraordinarily small when isothermally crystallized from the melt. The crystallization of the low molecular weight oligomers of PBPEP was first studied in comparison to the high molecular weight polymers. The oligomer-rich fraction was obtained by fractionation of the as-polymerized sample, which had a broad molecular weight distribution. The fractions thus obtained were characterized by solution viscometry and size exclusion chromatography. The melting temperature and the growth rate of the spherulite from the melt were investigated by differential scanning calorimetry and optical microscopy. The growth rate was one or two orders of magnitude smaller in the oligomer-rich fraction than in the other high molecular weight fractions. A collapsed spherulite appeared in the oligomer-rich fraction at high crystallization temperatures. It is speculated that in the oligomer-rich fraction there is an excess free energy due to defects in the crystal phase. This defect is considerably larger in the oligomer-rich fraction than in the other fractions because a large quantity of short length chains is present. 相似文献
33.
The diffusion and adsorption of C.I. Direct Yellow 12 and Blue 15 in water-swollen ordinary cellophane sheets were examined at various ionic strengths. The concentration dependence of apparent diffusion coefficients, Dc, for these dyes was obtained from the diffusion profiles in the substrate, which were measured by the use of the cylindrical film roll method. The decrease of apparent porosity with an increase in the amounts of adsorption was observed. To explain the diffusion/adsorption behaviors of these systems, a variable porosity model was proposed and was applied to analyze the concentration dependence of Dc's. The diffusion/adsorption behaviors of these dyes could be quantitatively described by this model at relatively low ionic strengths. At higher ionic strengths and/or lower values of C, i.e., at the large values of Cim/Cm, where the C's are the concentrations of immobilized (suffix im) and mobile (suffix m) species, it needed to introduce the concept of dynamic equilibria which occurred simultaneously with diffusion but deviated from the true equiliblia measured by the adsorption experiments. 相似文献
34.
Prediction of the biologically active sites in eclosion hormone from the silkworm, Bombyx mori 总被引:1,自引:0,他引:1
Kikuchi T; Okamoto M; Geiser M; Schmitz A; Gohda K; Takai M; Morita T; Horii K; Fujita N 《Protein engineering, design & selection : PEDS》1997,10(3):217-222
The structure-activity relationship of eclosion hormone from the silkworm,
Bombyx mori, was analyzed. First, the probable active residues in silkworm
eclosion hormone and also tobacco hornworm eclosion hormone were predicted
by the average distance map method. To examine the contributions of those
residues to the activity of silkworm eclosion hormone, Gly-substituted
mutants for those predicted residues were produced by site-directed
mutagenesis and their activities were evaluated by a bioassay. Finally,
Glu12, Met24 and Phe25 were estimated to be the crucial residues for the
eclosion hormone activity. The possibility of the development of a blocker
of an eclosion hormone receptor on the basis of the present work is also
discussed.
相似文献
35.
A new electrolytic solution based on a mixed solvent of ethylene carbonate (EC) with sulfolane (SL) or -butyrolactone (-BL) has been examined as an electric double layer capacitor. Fundamental properties, such as electrolytic conductivity, viscosity, and thermal stability, were measured for solutions containing quaternary alkylammonium salts as the supporting electrolyte. Maximum conductivities were obtained for the solutions with mixed solvent of 20–40 mol % EC in the EC+-BL system: 1.2–1.3×10–2S cm–1 for EC+-BL dissolving 0.5 M Et4 NBF4 (Et=C2H5). The electrochemical and the thermal stabilities of the solution were dependent on the electrolytic salt as well as the solvent composition. A stable discharge capacitance and a high coulombic efficiency were obtained in a model capacitor using carbon fibre electrodes and the organic electrolyte of EC+-BL/Et4NBF4 (or EC+-BL/Et4NPF6). 相似文献
36.
Koji Makino 《Electrochimica acta》2005,51(5):961-965
The electrodes prepared by a sputtering method were evaluated as the cathodes for direct methanol fuel cells (DMFCs). Pt loading below 0.25 mg cm−2 achieved higher mass activities than that of 0.5 mg cm−2 prepared by the paste method, which was general conventional method. However, an increase in Pt loading reduced the catalyst activity for the oxygen reduction reaction (ORR). This result may suggest an increase in only electrochemically inactive Pt. Pt utilization efficiency can be found about ten times higher at Pt loading of 0.04 mg cm−2. Moreover, addition of Nafion to sputter-deposited Pt cathodes is found possible to improve the catalyst activity for the ORR, but the excess Nafion over the optimum condition reduces the active sites. 相似文献
37.
Masahiko Shimada Ken'ichi Matsushita Shusei Kuratani Taira Okamoto Mjtsue Koizumi Koji Tsukuma Takaaki Tsukidate 《Journal of the American Ceramic Society》1984,67(2):23-C-
The temperature dependence of Young's modulus and internal friction (Q−1 )in alumina, silicon nitride, and partially stabilized zirconia (Y-PSZ) ceramics was studied. Little change in Q−1 was found for alumina, whereas Q−1 for silicon nitride ceramics increased above 700°C. The Q−1 of Y-PSZ increased markedly with increasing temperature up to a peak at ∼200°C. 相似文献
38.
α-Tocopherol was reacted with methyl linoleateperoxyl radicals at 37°C. The peroxyl radicals were generated by the reaction
of methyl linoleate with a free radical initiator, 2,2′-azobis(2,4-dimethylvaleronitrile). The primary products of α-tocopherol with methyl linoleate-peroxyl radicals were isolated by
reversephase and normal-phase high performance liquid chromatography (HPLC), and their structures were characterized by ultraviolet
(UV), infrared (IR),1H and13C nuclear magnetic resonance (NMR) and mass spectrometry (MS). There were four stereoisomers of methyl 13-(8a-peroxy-α-tocopherone)-9(Z),11(E)-octadecadienoate and four stereoisomers of methyl9-(8a-peroxy-α-tocopherone)-10(E),12(Z)-octadecadienoate. 相似文献
39.
Poly(L ‐lactic acid) (PLLA: Mw = 19.4 × 104)/poly(ethylene glycol) (PEG: Mw = 400) blend films were formed by use of a solvent‐cast technique. The properties and structures of these blend films were investigated. The Young's modulus of the PLLA decreased from 1220 to 417 MPa with the addition of PEG 5 wt %, but the elongation at break increased from 19 to 126%. The melting point of PLLA linearly decreased with increases in the PEG content (i.e., pure PLLA: 172.5°C, PLLA/PEG = 60/40 wt %: 159.6°C). The PEG 20 wt % blend film had a porous structure. The pore diameter was 3–5 μm. The alkali hydrolysis rate of this blend film was accelerated due to its porous structure. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 965–970, 2004 相似文献
40.
Lingyun Lyu Takeshi Hanada Naohiro Yamahira Jun Morita Ryota Yamamoto Ken Itomi Takumi Adachi Sho Kubouchi Shin Horiuchi 《应用聚合物科学杂志》2021,138(45):51443
The distribution of nano-sized silica in binary rubber blends is characterized by scanning transmission electron microscopy (STEM) tomography combined with energy dispersive X-ray spectrometry (EDX). 3D distribution of silica is visualized by STEM-EDX tomography with the tilt-series of silicon elemental maps, while the phase-separated morphologies of polyisoprene rubber (IR) and styrene-butadiene rubber (SBR) are visualized by STEM-tomography in high-angle-annular-dark field (HAADF) mode. The combination of STEM-EDX and STEM-HAADF tomography enables us to determine the distribution of silica between the two rubber phases quantitatively even with high contents of silica up to 70 phr (weight parts per hundred rubber). It is found that silica is preferentially distributed in the SBR phase, but it is also distributed in the IR phase when the IR fraction in the total rubber components is higher than 40 wt%. The preferential distribution of silica in the SBR phase improves the dispersion of the IR domains. This is the first use of this technique for a multicomponent polymer system, showing the advantage to characterize the complicated multicomponent polymer composite morphologies. 相似文献