全文获取类型
收费全文 | 608篇 |
免费 | 13篇 |
专业分类
电工技术 | 32篇 |
化学工业 | 124篇 |
金属工艺 | 9篇 |
机械仪表 | 7篇 |
能源动力 | 20篇 |
轻工业 | 42篇 |
无线电 | 64篇 |
一般工业技术 | 85篇 |
冶金工业 | 185篇 |
原子能技术 | 23篇 |
自动化技术 | 30篇 |
出版年
2023年 | 3篇 |
2022年 | 10篇 |
2021年 | 8篇 |
2020年 | 7篇 |
2019年 | 3篇 |
2018年 | 10篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 14篇 |
2013年 | 23篇 |
2012年 | 20篇 |
2011年 | 21篇 |
2010年 | 15篇 |
2009年 | 18篇 |
2008年 | 24篇 |
2007年 | 20篇 |
2006年 | 12篇 |
2005年 | 18篇 |
2004年 | 11篇 |
2003年 | 18篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 16篇 |
1998年 | 65篇 |
1997年 | 42篇 |
1996年 | 34篇 |
1995年 | 20篇 |
1994年 | 20篇 |
1993年 | 12篇 |
1991年 | 6篇 |
1990年 | 6篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 2篇 |
1982年 | 4篇 |
1981年 | 3篇 |
1980年 | 8篇 |
1979年 | 5篇 |
1978年 | 2篇 |
1977年 | 6篇 |
1976年 | 8篇 |
1975年 | 4篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有621条查询结果,搜索用时 15 毫秒
11.
Teruya Tanaka Junichi. H. Kaneko Yoshimi Kasugai Masaki Katagiri Hiroshi Takeuchi Takeo Nishitani Toshiyuki Iida 《Diamond and Related Materials》2005,14(11-12):2031
Radiation tolerance of a type IIa synthetic diamond detector was examined from irradiation of mono-energetic 14 MeV neutrons. Measurements of I–V (current–voltage) characteristics and energy spectrum for 5.486 MeV alpha particles were performed after neutron irradiation. In the I–V characteristics measurement, enhancement of rectification was observed after neutron irradiation of up to 2.0 × 1012 n/cm2. Concurrently with the enhancement of rectification, significant decrease in signal amplitude was observed in energy spectrum measurement for alpha particles. It is considered that these changes were due to increase in the concentration of defects acting as shallow energy levels in the forbidden band. For neutron irradiation of higher than 1.6 × 1013 n/cm2, weakening of the rectification characteristics and recovery of the signal amplitude were observed. These changes imply that deep energy levels, which were also considered to be introduced by defects, were dominant and weakened the effects of the shallow energy levels. Increase in the concentration of the deep trapping levels resulted in gradual decrease of the signal amplitude and degradation in the energy resolution. The peak for the alpha particles was obtained up to 5.5 × 1013 n/cm2. 相似文献
12.
Takamichi Iida Roderick Guthrie Nagendra Tripathi 《Metallurgical and Materials Transactions B》2006,37(4):559-564
By combining the modified Stokes-Einstein formula with the authors’ model for the melting-point viscosity, the authors present
a model for accurate predictions of self-diffusivity of liquid metallic elements. The model is expressed in terms of well-known
physical quantities and has been applied to various liquid metallic elements for which experimental data are available. The
results of calculations show that agreement with experimental data is excellent; the uncertainties in the calculations of
the self-diffusivities in various liquid metallic elements are equal to the uncertainties associated with experimental measurements.
Also, the authors propose an expression for the temperature dependence of self-diffusivity in liquid metallic elements in
terms of melting-point temperature. Using the model, self-diffusivity data are predicted for liquid iron, cobalt, nickel,
titanium, aluminum, magnesium, silicon, and so forth. 相似文献
13.
Makoto Iida Masao Gotoh Hitoshi Yokono Yasushi Miyano 《Polymer Engineering and Science》1986,26(10):701-707
Flexural properties of moldings made by Reaction Injection Molding (RIM), which are structural foams consisting of high density skin and low density core, were investigated by three-point bending tests. Two failure modes were observed in bending tests of the moldings made by RIM, and they are classified as follows according to the density ratio of skin layer to core layer: the opposite side of the skin layer to which load was subjected failed by tensile stress: and the same side of the skin layer to which load was subjected failed by compressive stress, causing wrinkling or buckling. Then the conventional composite beam theory was applied to the former failure mode and Hoff s buckling theory to the latter, and equations were derived to predict the flexural properties of the structural foams, which involved buckling from the flexural properties of solid construction. In addition, it has been shown that there exists a density distribution that maximizes the flexural strength of the moldings made by RIM with a given overall density. The results obtained here should be useful to the optimum structural design of moldings made by RIM. 相似文献
14.
A novel current source inverter system interconnected to the single‐phase grid is proposed. It has the same construction as the conventional three‐phase current source inverter that is interconnected to the single‐phase three‐wire distribution system. Though the proposed circuit has no output transformer, it can be equivalently performed as the single‐phase double cascade inverter by diverting the pole transformer in the utility system. By controlling the appropriate scheme, the output currents can be obtained as the five‐level waveforms and their distortions can be decreased sufficiently. It is applied to the interactive electric energy storage system with batteries and the basic discharging characteristics are discussed experimentally. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 50–61, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10380 相似文献
15.
The behavior of a premixed flame propagating from a chamber into a narrow channel at a high speed was examined using high speed and instantaneous schlieren photography, ion current measurement with electrostatic probes, and temperature measurement with an optical method. From detailed measurements of flames passing through the channel, flame extinguishment in the channel, no matter whether transient or not, was found to occur due to quenching of the reacting gas by rapid turbulent mixing with cold fresh mixture at the downstream of the contraction region and by heat transfer to the cold channel walls. Extinguishment must occur when these heat losses exceed the heat released by the chemical reaction of the flowing mixture. 相似文献
16.
Helicobacter pylori infection of the gastric mucosal surface was investigated in patients with hamartomatous fundic polyps or hyperplastic polyps and in patients without endoscopic evidence of disease (healthy subjects). Presence of H. pylori infection was determined by culture, histologic examination, and the endoscopic phenol red test. Adherence of H. pylori was evaluated with scanning electron microscopic examination of antral biopsy specimens. Both prevalence of H. pylori infection (P < 0.001) and H. pylori adherence (P < 0.05) were less in patients with hamartomatous fundic polyps than in healthy subjects and patients with hyperplastic polyps. However, the percentages of plasma cells in gastric mucosa that contained IgA and of gastric epithelial cells that expressed Lewis b did not differ significantly among the three groups. These findings suggest that defense mechanisms against the attachment of H. pylori other than IgA or Lewis b antigen are present in patients with hamartomarous fundic polyps. 相似文献
17.
Cationic chitosan (CT) and anionic dextran sulfate (Dex) were layer-by-layer (LbL) assembled from aqueous solutions containing
1 M NaCl on a quartz crystal microbalance (QCM) substrate, and the original films ((CT-Dex)3-CT)) were end-capped with LbL assembly from CT solutions containing 1 M NaCl and Dex solutions without NaCl. The enzymatic
degradation of films by chitosanase was quantitatively analyzed by QCM in terms of numbers of end-capping steps. The degradation
of films end-capped with (Dex-CT)3 was considerably prolonged when compared to those end-capped with other end-capping steps. A mechanism for the prolonged
degradation was proposed by quantitative QCM data and zeta potential results. 相似文献
18.
Antioxidant for fats and oils from canary seed: Sterol and triterpene alcohol esters of caffeic acid
Several kinds of seeds used as bird feed were extracted successively with hexane, ether and methanol. In the antioxidant test
with extracts, the ether extract from canary seeds showed the highest activity. The antioxidant fraction separated from it
by thin layer chromatography showed excellent activity for lard and sardine oil. The effective components were identified
by gas chromatography and gas chromatography-mass spectrometry of the hydrolyzed products as the esters of caffeic acid with
cycloartenol, gramisterol, sitosterol and campesterol with the minor amounts of 24-methylenecycloartanol, obtusifoliol, brassicasterol
and Δ7-stigmastenol. 相似文献
19.
Lida T Nakamori R Yabuta R Yada S Takagi Y Mano N Ikegawa S Goto J Nambara T 《Lipids》2002,37(1):101-110
A facile and efficient synthesis of the carboxyl-linked glucosides of bile acids is described. Direct esterification of unprotected
bile acids with 2,3,4,6-tetra-O-benzyl-d-glucopyranose in pyridine in the presence of 2-chloro-1,3,5-trinitrobenzene as a coupling agent afforded a mixture of the
α- and β-anomers (ca. 1∶3) of the 1-O-acyl-d-glucoside benzyl ethers of bile acids, which was separated effectively on a C18 reversedphase chromatography column (isolated yields of α- and β-anomers are 4–9% and 12–19%, respectively). Subsequent hydrogenolysis
of the α- and β-acyl glucoside benzyl ethers on a 10% Pd−C catalyst in acetic acid/methanol/EtOAc (1∶2∶2, by vol) at 35°C
under atmospheric pressure gave the corresponding free esters in good yields (79–89%). Chemical specificities such as facile
hydrolysis and transesterification of the acyl glucosides in various solvents were also discussed. 相似文献
20.
The glass transition behavior of emulsion-polymerized poly(methyl methacrylate) and polystyrene films containing sodium laurylsulfate as emulsifier was studied by measurements of dynamic mechanical properties and thermal depolarization current. The film specimens of the emulsion-polymerized polymers were prepared by casting from their benzene solutions. The glass transition temperatures of the emulsion-polymerized films are higher than those of the bulk-polymerized films. The higher glass transition temperature of the emulsion-polymerized films is attributed to the colloidal properties of sodium laurylsulfate in the process of the film formation. The restriction of the molecular chains in the emulsion-polymerized films is attributed to the interaction between the hydrophobic groups of sodium laurylsulfate and the polymer molecules. 相似文献