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71.
A series of novel hexene‐1–propylene random copolymers with isotactic sequence of propylene was synthesized with a MgCl2‐supported Cr(acac)3 catalyst. The molecular weight distribution of copolymers and homopolymers was considerably narrower than that of typical polyolefins produced by heterogeneous Ziegler–Natta catalysts. The crystallizability of the copolymers having a propylene‐unit content of more than 50 mol % drastically decreased with decreasing propylene‐unit content, and the copolymers with a propylene content of less than 50 mol % were completely amorphous. In the present novel type of random copolymers with crystallizable and noncrystallizable units, a single glass transition was observed between pure polypropylene and polyhexene‐1, and a major component was found to govern the final morphology and the mechanical characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2949–2954, 2004 相似文献
72.
Scanning electron microscopy (SEM) study of the morphologic change of high‐density polyethylene (HDPE) surface grafted with glycidyl methacrylate (GMA) was reported. Radiation‐induced grafting of GMA onto HDPE was carried out in acetone and dichloromethane solution, respectively. The effects of irradiation dose, atmosphere, and swelling time on grafting were investigated. Generally, the extent of grafting increased with irradiation dose, but for the grafting carried out in acetone solution, the extent of grafting initially increased with irradiation dose and then remained almost constant. The extent of grafting was higher in acetone solution than in dichloromethane solution at the same irradiation dose. The extent of grafting in nitrogen was higher than that in air. The successful grafting of GMA onto HDPE was confirmed by weighing and FTIR analysis. SEM investigations showed that the morphologies of the PE samples grafted in acetone solution were quite different to those grafted in dichloromethane. The grafting of GMA carried out in acetone was mainly on HDPE surface and that carried out in dichloromethane was mainly in the bulk of HDPE. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 相似文献
73.
Copolymerization of methacrylic acid (MAA) and ethyl acrylate (EA) was performed by the emulsion polymerization technique in the presence of a mixture of ionic and nonionic emulsifiers, at 85°C, using potassium persulfate as initiator (0.16 wt % of monomer). The molar ratio of MAA : EA varied between 44 : 56 and 54 : 46 in the monomer feed. Copolymers of MAA and EA were synthesized by incorporating diallyl phthalate (DAP) with varying concentrations (0–1.7 mol % of total monomer) in the feed. A copolymer latex of MAA, EA, and DAP was also prepared by the variable feed process. The intrinsic viscosity and gel content were determined. Copolymers were characterized by IR and NMR spectroscopic techniques. The composition of copolymers was determined by 1H‐NMR spectra and sequential distribution from 13C{1H}‐NMR spectra. The pH of the copolymer emulsion varied between 3 and 10 by addition of aqueous ammonia (23% w/w) and its effect on Brookfield viscosity was studied. The effects of copolymer composition, crosslinking agent concentration in the feed, monomer feed process, polymer solid contents, and shear rate on Brookfield viscosity were studied at pH ~ 8. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1430–1441, 2003 相似文献
74.
The tert‐butoxy radical‐facilitated grafting of methyl methacrylate (MMA) onto commercial polypropylene (PP) pellets and fiber was investigated in heterogeneous conditions similar to practical systems. Free‐radical grafting of several other monomers onto PP fiber was also investigated. Also, preliminary data from the grafting of MMA onto poly(ethylene terephthalate) pellets is presented. The PP‐graft‐PMMA residues were detected by solid‐state 13C‐NMR and photoacoustic IR spectroscopy. There was a good correlation between the degree of grafting (DG) determined from these spectroscopic techniques and the results from gravimetric methods. A maximum grafting efficiency of over 50% was found, whereas DG (20%) remained constant at various PP pellet, initiator, and monomer concentrations. However, at relatively low PP fiber concentrations, the DG was 27%; the increase was most likely due to the greater surface area of the fiber. There was also a reduction in DG (14%) at relatively low initiator concentrations. The reaction conditions were altered to favor grafting by the addition of more polymer substrate. When the ratio of tert‐butoxy radicals to PP was decreased, more of the substrate remained unmodified, and empirical calculations showed the formation of grafts with up to 40 monomer units. At high initiator concentrations, calculations showed that the graft residues were 1–2 units long. Therefore, variation of the polymer, initiator, and monomer concentrations was shown to have a significant effect on grafting. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 898–915, 2002 相似文献
75.
A thermally labile polymer, poly(propylene glycol), was modified to obtain PPG having an amino end group. PPG was incorporated into a partially aliphatic polyimide based on an alicyclic dianhydride, and this afforded triblock copolymers containing various amounts of PPG blocks. The thermal properties of the copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the PPG block in the copolymers was carried out at 240°C under various pressures to obtain porous polyimide films. The pores remained during the thermolysis under a reduced pressure of 710 mmHg, whereas they collapsed under (near) atmospheric pressure. The pore size increased as the amount of the PPG block in the copolymers increased. The dielectric constants of the porous polyimides varied from 2.60 to 2.42 with the original copolymer composition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 532–538, 2006 相似文献
76.
Ji-Won Jang Jae-Hyong Park Il-Jin Kim Jae-Hak Sim Seung-gun Yu Dong-Jin Lee Young-Hee Lee Sang-Hui Park Han-Do Kim 《应用聚合物科学杂志》2021,138(6):49788
In this study, a series of thermoresponsive cross-linked copolymer poly [N-isopropylacrylamide(NIPAm)-co-N-isopropylmethacrylamide(NIPMAm)] (P-M series samples: P-M-0, 10, 20, 30, 40, where numbers are co-monomer contents) hydrogels were prepared by free radical polymerization using the main monomer N-isopropylacrylamide (NIPAm), co-monomer N-isopropylmethacrylamide (NIPMAm), cross-linking agent N, N-methylenebisacrylamide, initiator (ammonium persulfate)/catalyst, and solvent water. In addition, a series of samples [P-G series samples: P-G-0, 10, 20, 30, 40, where numbers are co-solvent glycerol content) were prepared using P-M-40 as components and water/co-solvent glycerol as a mixed solvent. The effects of co-monomer NIPMAm and co-solvent glycerol contents on the lower critical solution temperature (LCST)/freezing temperature and light transmittance as function of temperature of the prepared copolymer gels were investigated. The resulting thermoresponsive polymer gels had LCSTs in the range of 17.9 to 38.7°C and freezing points in the range of 6.3 to −38.5°C. These gels are suitable materials for smart windows that are responsive to various environmental conditions. 相似文献
77.
Li-Cheng Jheng I-Hsin Wang Tsung-Han Hsieh Chin-Ting Fan Chi-Hui Hsiao Chien-Pang Wu Ming-Tsong Leu Ting-Yu Chang 《应用聚合物科学杂志》2021,138(13):50096
Poly(ethylene oxide)-b-poly(butadiene-co-acrylonitrile)-b-poly(ethylene oxide) (PEO-b-PBN-b–PEO) triblock copolymers with three different compositions were synthesized from poly(ethylene glycol) methyl ethers and carboxylic acid-terminated poly(butadiene-co-acrylonitrile) (CTBN) by ester coupling reaction at room temperature. The PEO-b-PBN-b-PEO was incorporated into anhydride cured epoxy thermosets to improve the fracture toughness by the formation of either nano-sized spherical micelles or micron-sized vesicles. The polymer chemical structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and gel permeation chromatography. The morphology of PEO-b-PBN-b–PEO within the epoxy thermosets was investigated using a transmission electron microscope, an atomic force microscope, and a scanning electron microscope. Also, we conducted impact testing and plane-strain fracture toughness testing to evaluate the fracture toughness in terms of the impact strength and the critical stress intensity factors (KIC) for the modified epoxy thermosets. The results revealed that all the PEO-b-PBN-b-PEO triblock copolymers are more effective in the toughening of epoxy thermoset compare to CTBN. We found that the 5 wt% PEO-b-PBN-b-PEO modified epoxy thermoset containing micron-sized vesicles exhibited the highest KIC, which was 3.23 times as high as the KIC of pristine epoxy thermoset. Besides, the glass transition temperature remained and the tensile modulus did not reduce remarkably when the amount of PEO-b-PBN-b-PEO added into epoxy was 5 wt%. 相似文献
78.
Sergii Sinelnikov Luydmila Orel Larisa Kobrina Valentyna Boiko Sergii Riabov Volodymir Shtompel Olga Povnitsa Svetlana Zagorodnya 《应用聚合物科学杂志》2021,138(23):50554
Polymer cross-linked matrices based on polyacrylamide (PAA) and β-cyclodextrin-pseudorotaxane have been designed. The structure and properties of the objects synthesized were confirmed and studied by a series of methods, involving ultraviolet-, Fourier transform infrared-spectroscopy, thermal mass spectrometry, DSC, X-ray diffraction analysis (WAXS and SAXS). Desorption kinetics (especially significant slowing of desorption process) of some drugs, like metoprolol succinate and loratadine from obtained polymer matrices is shown to be optimal with 10 wt% β-CD-pseudorotaxane in their structure. 相似文献
79.
In this study, the effects of different spinning methods including traditional wet and dry-jet wet spinning, and newly developed dry-jet gel spinning, on the structures and performances of polyacrylonitrile fibers, as well as the structural evolution during stabilization and carbonization, are compared in detail. The structural differences along radial direction, surface roughness, and chain orientation of carbon fibers are inherited from their precursor fibers, and these factors are determined by spinning technologies and processing conditions. Among all spinning methods, dry-jet gel spinning could prepare fibers with the best chain orientation, the highest tensile properties, and the lowest surface roughness, which would be favorable for achieving higher mechanical performance. Additionally, for the resultant carbon fibers, the surface modification of dry-jet gel spun carbon fibers is easier than dry-jet wet spun carbon fibers, and comparable to wet spun carbon fibers. Overall, dry-jet gel spinning is promising to make carbon fibers with both excellent tensile properties and good interfacial adhesion with epoxy matrix. 相似文献
80.
Hélida V. P. Vieira Priscila F. Oliveira Josane A. Costa Leonardo A. de Oliveira Letícia S. Mota Claudia R. E. Mansur 《应用聚合物科学杂志》2021,138(44):51301
Partially hydrolyzed polyacrylamide (PHPA) is the most widely used polymer in enhanced oil recovery (EOR) applications. However, under conditions of high temperature and salinity, the PHPA molecules become hydrolyzed, causing a drastic reduction of the viscosity of the polymer solution due to the presence of negative charges, making the molecules more susceptible to interactions with cations. In this sense, in order to increase the stability of these polymers, an anionic monomer more resistant to cations such as 2-acrylamido-2-methylpropane sulfonic acid (AMPS) has been incorporated into the HPAM molecules. This work evaluated the thermal stability of a copolymer (acrylamide and AMPS - AN125) and a terpolymer (acrylamide, acrylate, and AMPS-FP5115) in the time course of 360 days. The tests were carried out in typical conditions of Brazilian offshore reservoirs, such as absence of oxygen, high temperature, and high salt concentration. The test method involved measurements of intrinsic viscosity in function of time and determination of the hydrolysis degree of the polymers by elemental analysis. The copolymer AN125 was more stable under the test conditions than the terpolymer FP 5115 due to the presence of a higher concentration of AMPS in the copolymer. The AMPS group was hydrolyzed to AA at a temperature of 100 °C, however, the increase in salt concentration delayed the onset of this degradation. The tests indicated that the presence of a higher AMPS content in the copolymer does not prevent the polymer from undergoing hydrolysis, but delays the polymer precipitation step in the solution. 相似文献