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971.
In the ultrafiltration test of a myoglobin solution through porous membranes of the ABA-type block copolymers composed of polyamide as outer segments and polyoxyethylene (Mn = 1.9–2.0 × 104) as an inner segment, in which the values of weight fraction of the polyamide segments (W) were 0.90, 0.84, 0.82, 0.81, and 0.73, the concentration of the permeate was found to be much higher than that in feed under the pressure difference of 1–2 kg/cm2. Such singularly facilitated permeation was observed also in the test through the dense membranes of the polyamide–polyoxyethylene block copolymer with W of 0.81 and 0.73. On the other hand, neither porous nor dense membranes of the graft copolymer (W = 0.83) having a dextran stock (Mn = 1.8 × 104) and 2.6 pieces of polyamide branches showed similar facilitated permeation, although dextran was soluble in water as well as polyoxyethylene. The apparent interaction of myoglobin with dextran may be stronger than that with polyoxyethylene. © 1994 John Wiley & Sons, Inc. 相似文献
972.
Masaaki Takehisa Sueo Machi Hiromasa Watanabe Takashi Ueno Seiichi Takahashi Ryoji Tsuchiya Kanji Otaguro Isao Motoda Yoshio Takasaka Kazukiyo Miyanaga Waichiro Kawakami Kouichi Yamaguchi Takanobu Sugo Hayato Nakajima Terutaka Watanabe Chuhei Hinachi 《应用聚合物科学杂志》1979,24(3):853-864
Radiation-induced bulk polymerization of ethylene was carried out with use of a pilot plant with a 10 liter reactor at pressures of 225–400 kg/cm2, temperatures of 30–95°C, ethylene feed rates of 5–28 kg/hr, and dose rate of 3.8 × 105 rad/hr. Characteristics of the process are mild polymerization conditions and capability of producing medium density polyethylene in powder form. The spacetime yield and molecular weight of polymer were in the range of 3.5 to 13.1 g/liter hr and 2.2 × 104 to 14 × 104, respectively. The space-time yield increased with mean residence time and 2.4 powders of pressure, and decreased with temperature. Molecular weight changed similarly with the reaction conditions. These results were consistent with those of the bench plant experiment and the scale effect was small. Polymer deposit to the reactor wall limited a period of continuous operation of the plant. The amount of deposited polymer was increased with the square of reaction time. The rate of polymer deposit was proportional to polymer concentration and to the cube of pressure. The polymer deposit cannot be solved in the bulk process. 相似文献
973.
Yasunori Yoshida Takashi Nakano Hidetsugu Tanaka Terunori Fujita 《Israel journal of chemistry》2002,42(4):353-359
This contribution reports the catalytic behavior of bis(pyrrolide-imine)Ti complexes 1 and 2 , [2-(RNCH)-C4H3N]2TiCl2 ( 1 , R = Ph; 2 , R = cyclohexyl), and bis(phenoxy-imine)Ti complex 3 , [2-(Ph-NCH)-3-t Bu-C6H3O]2TiCl2 for the copolymerization of ethylene with propylene, 1-hexene, or norbornene. An inspection of the X-ray structures of complexes 1–3 suggested that complexes 1 and 2 with pyrrolide-imine ligands would provide more space for olefin polymerization than complex 3 with phenoxy-imine ligands. In addition, DFT calculations also showed that active species derived from complexes 1 and 2 possess higher electrophilicity of the Ti center compared to that from complex 3 . Complexes 1 and 2 on activation with methylalumoxane (MAO) had higher affinity for propylene and 1-hexene and incorporated higher amounts of propylene ( 1 ; 30.5 mol%, 2 ; 23.4 mol%) and 1-hexene ( 1 ; 1.9 mol%, 2 ; 1.7 mol%) than complex 3 (propylene; 4.5 mol%, 1-hexene; 0.4 mol%). The incorporation levels of propylene and 1-hexene displayed by complexes 1 and 2 were lower than those for Cp2TiCl2 (propylene; 41.6 mol%, 1-hexene; 5.1 mol%) under identical conditions. In contrast, complexes 1 and 2 exhibited higher incorporation ability for norbornene and produced copolymers with much higher norbornene contents ( 1 ; 32.0 mol%, 2 ; 26.5 mol%) than Cp2TiCl2 (1.2 mol%) under the same conditions. Additionally, complex 3 also promoted higher norbornene incorporation (4.3 mol%) than Cp2TiCl2 and provided a copolymer with extremely narrow molecular weight distribution (Mw/Mn 1.14). A correlation exists between electrophilicity of the Ti center in active species and norbornene incorporation. 相似文献
974.
Takashi Fujikawa Hiroshi Kimura Kazuyuki Kiriyama Kazuhiko Hagiwara 《Catalysis Today》2006,111(3-4):188-193
Cosmo Oil has successfully developed a new CoMo HDS catalyst, C-606A, for production of ultra-low sulfur diesel fuels. This catalyst was prepared by an impregnation method using a solution containing Co, Mo, P, and citric acid on a HY-Al2O3. The resulting catalyst air-dried only without calcination. The HDS activity was measured with straight-run light gas oil feedstocks under industrial hydrotreating conditions. C-606A had a three times higher HDS activity compared with the conventional CoMoP/Al2O3 catalyst. Commercial operation with C-606A has successfully demonstrated high performance. This catalyst has superior activity, which enables <10-ppm sulfur content in products in a commercial hydrotreater designed to produce 500-ppm sulfur diesel fuels. 相似文献
975.
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
976.
The photocatalytic oxidation of CO into CO2 with oxidants such as NO, N2O and O2 proceeded efficiently on a Mo/SiO2 with high Mo dispersion under UV light irradiation. It was found that the reaction rate greatly depended on the kind and concentration of the oxidant. Photoluminescence investigations reveal the close relationship between the reaction rate and the relative concentration of the photo-excited Mo6+-oxide species, i.e. charge transfer–excited–triplet state (Mo5+–O−)*, under steady-state reaction conditions. Moreover, the photocatalytic oxidation of CO with O2 in excess H2 was carried out to test suitability for applications to supplying pure H2. This reaction was seen to proceed efficiently on Mo/SiO2 with a high CO conversion of 100% and CO selectivity of 99% after 180 min under UV light irradiation, showing higher photocatalytic performance than TiO2 (P-25) photocatalyst. UV–vis, XAFS, photoluminescence and FT-IR investigations revealed that the high reactivity of the charge transfer–excited–triplet state (Mo5+–O−)*, with CO as well as the high reactivity of the photoreduced Mo-oxide species (Mo4+-species) with O2 to produce the original Mo-oxide species (Mo6+O2−), played a crucial role in the reactions. 相似文献
977.
Synchronous fluorescence spectra of model polycondensed aromatic hydrocarbon molecules were recorded and used to identify the number of condensed rings in the aromatic molecules. A coal-derived liquid from Yubarishinko coal was initially separated into fractions having different number of condensed aromatic rings, and each fraction was further divided into narrow fractions having different numbers of carbon atoms. These fractions were studied using synchronous fluorescence spectroscopy. Results indicate the potential usefulness of synchronous fluorescence spectroscopy as a method of analysis of complex mixtures as coal-derived liquids despite the limitation of the method that some molecules give only weak peaks. Several components in some fractions were identified by a combination of synchronous fluorescence spectra and conventional excitation and emission fluorescence spectra. 相似文献
978.
Reactive blending has been usually utilized to stabilize morphology and to improve the properties of multi-component polymer blends by generating copolymers in situ at the interface. However, the present study on blends composed of poly(butylene terephthalate) (PBT) and functionalized styrene-acrylonitrile random copolymer (SAN) demonstrates another possibility for this method, i.e. tailoring morphology and thereby controlling the properties of polymer blends. By varying reaction conditions it was demonstrated that blends could be formed having the same ratio of [PBT]/[SAN] but which possessed completely different microstructural forms: a sea-island morphology with and without micelles, a corded dispersed phase morphology, and a highly oriented, layer-like morphology. 相似文献
979.
Preparation and properties of poly(methylmethacrylate)-silica hybrid materials incorporating reactive silica nanoparticles 总被引:1,自引:0,他引:1
In this study, poly(methylmethacrylate) (PMMA)-based hybrid materials were prepared from reactive silica nanoparticles. These nanoparticles were obtained by the reaction of 2-(methacryloyloxy)ethyl isocyanate with colloidal silica dispersed in ethyl acetate, and they were copolymerized in various ratios with methyl methacrylate. Dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and visible spectrometry were performed to evaluate the physical properties of the resulting hybrid materials. The PMMA-silica hybrid copolymers maintained high transparency, and their storage elastic modulus and surface hardness increased with increasing silica content. Moreover, in comparison with PMMA, the hybrid copolymers had greater heat resistance and lower volume contraction. 相似文献
980.
Yutaka Shinoda Michiyuki Yoshida Takashi Akatsu Fumihiro Wakai 《Journal of the American Ceramic Society》2004,87(10):1919-1926
The deformation behavior of boron- and carbon-doped β-silicon carbide (B,C-SiC) with an average grain size of 260 ± 18 nm containing 1 wt% boron was investigated by compression testing at elevated temperatures. Extensive grain growth during deformation was observed. The stress–strain curves were compensated for grain growth by assuming power-law type of dependence on grain size and strain rate. The stress exponent n was ∼1.3 and the grain size exponent p was ∼2.7 at temperatures ranging from 1593° to 1758°C. The apparent activation energy of deformation Q d was ∼760 kJ/mol, which was lower than the activation energy for lattice diffusion of silicon and carbon in SiC and higher than that for grain-boundary diffusion of carbon in SiC. These results suggest that the deformation mechanism of the fine-grained B,C-SiC is grain-boundary sliding accommodated by the grain-boundary diffusion. 相似文献