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71.
Shinichi Kitade Kazuo Asuka Isamu Akiba Yusuke Sanada Kazuo Sakurai Hiroyasu Masunaga 《Polymer》2013,54(1):246-257
Shear-induced crystallization of a long chain hyper-branched polypropylene (LCB-PP, denoted PP-3) was carried out at a relatively high temperature of 170 °C, close to its melting temperature of 158 °C. Small-angle X-ray scattering (SAXS) showed that the intensity ratio of the normal to the perpendicular to the shear (V/H) was always larger than 1 for PP-3, indicating that shish-like structures were predominately formed and further growth to kebab was suppressed in PP-3. The crystallization behavior of PP-3 can be explained by the nature of PP-3 that there were a large amount of crystallization nuclei due to their branching points, and the point-like precursors formed from these nuclei were arrayed linearly along the shear direction and transformed into thread-like precursors or premature shishs; however, owing to the large amount of branching, further progress in crystallization was suppressed. 相似文献
72.
Kentaro Kuratani Masayasu Uemura Minoru Mizuhata Akihiko Kajinami Shigehito Deki 《Journal of the American Ceramic Society》2005,88(10):2923-2927
We report on the direct deposition of high-quality ZrO2 thin films on various kinds of substrates by the liquid phase deposition method. After reaction for 24 h, thin films formed on various kinds of substrates, and the obtained thin film was comprised of densely packed nano-sized particles. The film annealed at 500°C showed a tetragonal phase at room temperature and this phenomenon has been discussed from the viewpoint of crystallite size effect. The result of optical transmittance measurement revealed that high transparency, more than 70% transmittance, has been achieved for the film after annealing at 900°C. 相似文献
73.
Hajime Arai Masayuki Tsuda Masahiko Hayashi Hideaki Ohtsuka Yoji Sakurai 《Electrochimica acta》2005,50(9):1821-1828
Several polymorphs of layered nickel dioxide were prepared by using the chemical insertion of alkaline ions into Li0.10NiO2. We used aqueous AOH (A = Li, Na, K) solutions as reducing agents. Sodium and potassium insertion resulted in hydrated layered compounds that can be classified as γ-NiOOH with high crystallinity, while lithium insertion occurred without hydration. We discuss the coordination environment around the A+ ions for these inserted compounds. The thermal behavior, analyzed using high temperature (HT) X-ray diffraction (XRD) and thermogravimetric (TG) measurements, indicated that heating the hydrate at 150 °C yielded its dehydrate. The electrode performance of the nickelate was studied in lithium cells. We discuss the effect of interlayer water on cell rechargeability and the similarity between these nickelate and hydrated manganese dioxide (birnessite). 相似文献
74.
Metallic Cu electrode can electrochemically reduce CO2 to CH4, C2H4 and alcohols with high yields as revealed by the present authors. Many workers reported that formation of CH4 and C2H4 rapidly diminishes during electrolysis of CO2 reduction. This paper shows that such deactivation of Cu electrode is reproduced with electrolyte solutions prepared from reagents used by these workers. Deactivated Cu electrodes recovered the electrocatalytic activity for CO2 reduction by anodic polarization at −0.05 V versus she in agreement with the previous reports. Features of the deactivation depend greatly on the individual chemical reagents. Purification of the electrolyte solution by preelectrolysis with a Pt black electrode effectively prevents the deactivation of Cu electrode. Anode stripping voltammetry of Cu electrodes, which were deactivated during electrolysis of CO2 reduction, showed anodic oxidation peaks at ca. −0.1 or −0.56 V versus she. The severer the deactivation of the Cu electrode was, the higher electric charge of the anodic peak was observed. It is presumed that some impurity heavy metal, originally contained in the electrolyte, is deposited on the Cu electrode during the CO2 reduction, poisoning the electrocatalytic activity. On the basis of the potential of the anodic peaks, Fe2+ and Zn2+ are assumed to be the major contaminants, which cause the deactivation of the Cu electrode. Deliberate addition of Fe2+ or Zn2+ to the electrolyte solutions purified by preelectrolysis exactly reproduced the deactivation of a Cu electrode in CO2 reduction. The amount of the deposited Fe or Zn on the electrode was below the monolayer coverage. Electrothermal atomic absorption spectrometry (etaas) showed that Fe originally contained in the electrolyte solution is effectively removed by the preelectrolysis of the solution. Mechanistic difference is discussed between Fe and Zn in the deterioration of the electrocatalytic property of Cu electrode in the CO2 reduction. The concentration of the impurity substances originally contained in the chemical reagents as Fe or Zn is estimated to be far below the standard of the impurity levels guaranteed by the manufacturers. Presence of trimethylamine in the electrolyte solution also severely poisons a Cu electrode in the CO2 reduction. It was concluded that the deactivation of Cu electrode in CO2 reduction is not caused by adsorption of the products or the intermediates produced in CO2 reduction. 相似文献
75.
In order to improve the fracture properties of p, p′-diaminodiphenylmethane-cured epoxy resin, various kinds of aromatic and aliphatic glycidyl compounds were investigated as a modifier at an amount of 30 wt %. Several compounds promoted the fracture toughness. In any glycidyl compounds, however, heat resistance was decreased by the modification. The dynamic mechanical properties of the modified epoxy resins were measured. The crosslinking density ρ was calculated from the theory of rubber elasticity, and the mechanical properties of the resins were discussed in regard to the crosslinking density. Tensile strength was scarcely affected by the crosslinking density. Elongation at break and Izod impact strength increased remarkably with decrease in crosslinking density. The fracture toughness KIc- increased with decrease in crosslinking density except at small ρ. 相似文献
76.
Thermal oxidative degradation behavior of polypropylene (PP) with different tacticities was studied based on the activation energy (ΔE) data obtained by thermogravimetric analysis (TGA). The ΔE value showed a negative proportion to the content of meso pentad fraction (mmmm) in all of isotactic PP (iPP) samples, and that of syndiotactic PP sample considerably deviated from this negative proportion relationship. Since the value of mmmm was directly related to polymer chain conformation, the ΔE value was thought to have close connection with the concentration of 31 helix conformation in the iPPs. The ΔE changes would be caused by the competition between uni- and bimolecular hydroperoxide decomposition, which was controlled by concentration and character of conformations of PPs. 相似文献
77.
Summary As one of a series approaches in using two-component and three-component donor-free Ziegler–Natta catalysts, in this preliminary work, the effects of various preparation and polymerization conditions including catalyst preparation by wet- or dry- grinding, the type of cocatalyst, with or without pretreatment of catalyst by cocatalyst before polymerization, Al/Ti molar ratio and polymerization temperature, etc., on the isospecific nature of active sites of the TiCl3 catalyst were studied through a systematic characterization of the PPs by a combination of GPC, 13C-NMR with TREF method. It was demonstrated that the types of Al-alkyl cocatalysts play the most dominant role in determination of isospecificity of activate sites and its distribution. A plausible mechanism (Scheme 1) regarding the formation of isospecific active sites with different stability in terms of Ti–Al bimetallic complexing depending on the type of cocatalyst had been proposed. Except the catalyst grinding method, other factors eg., pretreatment, temperature, and Al/Ti molar ratio, etc. did not show obvious effects on the isospecific nature of active sites. 相似文献
78.
Summary Conformational analyses using quantum chemical calculations were carried out for 1- to 4-mers of ethylene
oxide (EO) and ethylene imine (EI) oligomer models (EO-x and EI-x, x = 1 - 4) in the liquid phase using
four solvents (permittivity: ε = 2.0 ~80.1). The results were compared against those obtained in
the gaseous phase. The calculations involved either RHF/6-31+G(d,p) or B3LYP/6-31G(d) // SCRF/IPCM,
based on the observed and calculated results for the energy difference between trans-
and cis-dichloroethane. The conformations repeated for a unit of
X-C, C-C and C-X bonds (X: O or N) were examined. For both oligomers, the energies of every conformer
decreased with increasing ε values, and were linear against the Kirkwood function (Kf
= (ε-1)/(2ε+1)). For the EO oligomers, the (ttt)x conformer was most
stable in the gaseous phase. In liquid phases, however, the preference for the gauche-conformation
(gauche preference) of the C-C bonds increased with higher values of ε. In the case of EO-3, the
(tg+t)x conformer was most stable above an ε value
of 8.9, which were in good agreement with those observed for triglyme solutions using NMR analysis.
For the EI oligomers, the (tg+t)x conformer was most
stable in either gaseous or liquid phase, and the gauche preference of the C-C bonds in both phases
were comparable. These results were in good agreement with those observed for di-MEDA solutions using
NMR analysis. It was estimated that such small solvent effects on gauche preferences of the EI oligomers
result in weakening for hydrogen bonds (NH-N) of neighboring imino groups by solvents. 相似文献
79.
Smart sunglasses based on electrochromic polymers are proposed and developed in this study. This article discusses the design, processing, and the optical and electrical performance of a prototype smart sunglasses based on cathodic electrochromic (EC) polymers, which show several merits compared with traditional materials for sunglasses lens as well as other smart window materials. It is a multilayer design of device. The conjugated polymer, poly[3,3‐dimethyl‐3,4‐dihydro‐2H‐thieno [3,4‐b] [1,4]dioxepine] (PProDOT‐Me2), is utilized as the electrochromic working layer. The counter layer of the device is vanadium oxide (V2O5) film, which serves as an ion storage layer. There is also a polymer gel electrolyte acting as the ionic transport layer, sandwiched between the working and counter layers. The characteristics of the prototype device are reported, including transmittance (%T), driving power, response time, open circuit memory, and lifetime. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
80.
The electrooxidation of methanol, ethanol, and 2-propanol was investigated with interdigitated array electrodes (IDAEs). The IDAE oxidizes alcohol at the generator and reduces the reaction intermediates produced by the oxidation process at the collector. Thus, the reaction intermediates can be estimated with the IDAE. The IDAE in the present work was made of sputter deposited Pt and Pt–Ru. The use of Ru free and added electrodes provides information on the effect of Ru addition on the alcohol oxidation. Cyclic voltammetric analyses revealed that Ru addition enhances the oxidation currents and reduces the Eonset of the alcohols. The detectable reaction intermediate at the methanol and ethanol oxidation was proton, while the intermediate species was acetone in 2-propnaol oxidation. 相似文献