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131.
Il-Nyoung YoonYoungsun Lee Docki KangJungsik Min Jongok Won Minyoung KimYong Soo Kang Sung-ho KimJeong-Jin Kim 《International Journal of Adhesion and Adhesives》2011,31(2):119-125
Color-stable hydrogenated Bisphenol A (HBA) epoxy adhesives, containing organic-inorganic hybrid nanomaterials, were prepared and their properties investigated. Poly(propylene glycol)bis(2-aminopropyl ether) (D230) was used as the room temperature curing agent, and functional organic-inorganic hybrid nanomaterials, to tailor the adhesives, were prepared by a sol-gel reaction of 3-glycidoxypropyltrimethoxysilane and tetraethoxysilane. The commercial polyhedral oligomeric silsesquioxanes (POSS) having epoxy functional groups were also used. The concentration dependence of different nanomaterials, containing epoxy functional group for HBA/D230 adhesives, was studied. The tensile strength increased with the addition of nanomaterials having glycidyl epoxy group; however, the dependence varied with the size, the number of functional groups, and the amount of the addition. HBA/D230 adhesives containing different amounts of nanomaterials, whose compositions are similar to that of granite, were applied to the Korean granite and the results were compared with those obtained by using commercial adhesives, which have the problem of significant color change and high viscosity. The mechanical properties of HBA/D230 adhesives, containing POSS having glycidyl epoxy group, are found to be similar to those of commercial adhesives. Besides, it has low viscosity and long-term color stability. 相似文献
132.
In this study, cells from the stromal vascular fraction of human subcutaneous tissues were induced to differentiate toward
adipose cells in vitro for 2 weeks. During adipogenic differentiation, we followed the chronological changes in their morphology
with Coherent anti-Stokes Raman scattering (CARS) microscopy and checked the PPAR-γ and UCP-1 expression with RT-PCR. On day
4 after inducing adipogenic differentiation, CARS imaging showed multiple small lipid droplets (LD) distributed peripherally
along the cellular membrane. PPAR-γ began to express at this time and increased until day 14 at a steady rate. On day 7, the
cells appeared as brown adipocytes with numerous small LD throughout the cytoplasm, and the mRNA level of UCP-1 rose abruptly
by 6- to 7-fold. After an additional 7 days, CARS imaging showed the development of a large LD, which is characteristic of
white adipocytes, and the mRNA level of UCP-1 slumped significantly. These results demonstrate the possibility that ADSC pass
through a brown adipocyte-like stage while differentiating into white adipocytes. 相似文献
133.
Surface functionalization of multiwall carbon nanotubes (MWCNTs) was carried out by introducing a ylide group containing anchored
phenol structures. Epoxy nanocomposites filled with modified and pristine carbon nanotubes were prepared, and their mechanical,
electrical, and thermal properties were evaluated. Mechanical properties such as tensile strengths and Young’s moduli of the
epoxy nanocomposites increased significantly with the addition of the modified MWCNTs compared to the pristine MWCNTs, due
to the strong interaction between the modified MWCNTs and the epoxy matrix. Scanning electron microscopy of the fractured
epoxy systems revealed that the functionalized MWCNTs were finely dispersed in the matrix, as opposed to the pristine carbon
nanotubes. The epoxy/functionalized MWCNT nanocomposite had a lower surface electrical resistance than the epoxy/pristine
MWCNT nanocomposite, confirming the effect of functionalization. 相似文献
134.
Yin Fong Yeong Ahmad Zuhairi Abdullah Abdul Latif Ahmad Subhash Bhatia 《Journal of Porous Materials》2011,18(2):147-157
Propylsulfonic acid-functionalized partially crystalline silicalite-1 materials were synthesized via one step co-condensation technique by varying the molar ratio of organosilane source, 3-mercaptopropyltrimethoxysilane (3MP) to tetraethylorthosilicate (TEOS) in the range of 0.05–0.30, and subsequent oxidation of thiol group to propylsulfonic acid using hydrogen peroxide (H2O2). These materials were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and nitrogen adsorption–desorption method. The structure of these materials was determined by Fourier transform infrared spectroscopy (FT-IR) and 29Si and 13C solid state NMR. XRD results show that % crystallinity of the materials decreased with the increase in 3MP concentration in the synthesis mixture. Selected area electron diffraction (SAED) showed the presence of crystalline and amorphous phases in the samples. An amorphous phase was formed when 3MP concentration was 30 mol% of the total silica source. After elimination of the structure directing agent (SDA) by calcination at 420 °C, thermogravimetric analysis (TGA) shows that the structure was thermally stable up to 550 °C. Ammonia temperature-programmed desorption (NH3-TPD) shows that the acid capacity of these materials was in the range of 1.19–1.83 mmol H+/g, which shows that these materials could be used as potential heterogeneous acid catalyst. 相似文献
135.
Jin Ho Bang 《Electrochimica acta》2011,56(24):8674
Hollow graphitic carbon spheres (HGCSs) with a high surface area are produced by the carbonization of hollow polymer spheres obtained by the polymerization of core/shell-structured pyrrole micelles. HGCSs are employed as a carbon support material in a direct methanol fuel cell catalyst, and their effect on the electrocatalytic activity toward methanol oxidation is investigated. Pt catalyst supported on HGCSs shows a better electrocatalytic activity compared to that on Vulcan XC-72, which has been commonly used in fuel cell catalysts. The observed enhancement in the electrocatalytic activity is attributed to the improved electronic conductivity and high surface area of HGCSs. 相似文献
136.
Ho Chul Shin Kyung Wan Nam Won Young Chang Byung Won Cho Won-Sub Yoon Xiao-Qing Yang Kyung Yoon Chung 《Electrochimica acta》2011,(3):1182
The structural changes of LiFePO4 and C-coated LiFePO4 during charging at various C-rates and temperatures are investigated using synchrotron based in situ X-ray diffraction technique. The XRD patterns collected during cycling show the structural evidence of the positive effects of carbon coating on LiFePO4 for the electrochemical performance improvements at different temperatures, especially at low temperatures. At −10 °C, the C-coated LiFePO4 shows comparable capacities with the sample cycled at room temperature when cycled at C/5 rate with a slight shift of the plateau to a higher voltage during charging. The in situ XRD patterns collected simultaneously show a complete phase transformation from triphylite to heterosite. At −20 °C, the C-coated LiFePO4 delivers 55.6% of its theoretical capacities at C/5 rate. However, the plateau in the charging curve becomes sloppy and shifts to a higher voltage. The in situ XRD patterns show that the phase transformation from triphylite to heterosite is not completed when charged to 4.5 V due to the larger polarization when charged at −20 °C. 相似文献
137.
Palraj Kasinathan Dong Won Hwang Uhwang Lee Young Kyu Hwang Jong-San Chang 《Chemical engineering science》2011,(20):4549
Fermentation-derived ammonium lactate was converted into ethyl lactate by decomposition in various organic solvents followed by esterification with ethanol over Amberlyst catalyst. The ammonium lactate was decomposed more efficiently in an organic solvent with high boiling point, where the produced lactic acid was stabilized well as a monomer without oligomerization. However, only the nonreactive phosphate-type solvent such as triethyl phosphate and tributyl phosphate showed a notable ethyl lactate yield in the subsequent esterification reaction compared with dimethyl sulfoxide and N-methyl pyrolidine. The lactic acid yield in ammonium lactate decomposition and the subsequent ethyl lactate yield were also highly dependent on solvent ratio to ammonium lactate, temperature and pressure in ammonium lactate decomposition reaction. The amino acid impurity contained in the fermented ammonium lactate as well as the unreacted ammonium lactate reduced the acid strength of Amberlyst-36, which resulted in the final ethyl lactate yield. 相似文献
138.
Young‐Jung Wee Lebaka Veeranjaneya Reddy Soon‐Do Yoon Hwa‐Won Ryu 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(5):757-762
BACKGROUND: Purification and enzymatic properties of a chitosanase from Bacillus subtilis RKY3 have been investigated to produce a chitooligosaccharide. The enzyme reported was extracellular and constitutive, which was purified by two sequential steps including ammonium sulfate precipitation and ion exchange chromatography. RESULTS: Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis of the purified chitosanase revealed one single band corresponding to a molecular weight of around 24 kDa. The highest chitosanase activity was found to be at pH 6.0 and at 60 °C. Although the mercaptide forming agents such as Hg2+ (10 mmol L?1) and p‐hydroxymercuribenzoic acid (1 mmol L?1, 10 mmol L?1) significantly or totally inhibited the enzyme activity, its activity was enhanced by the presence of 10 mmol L?1 Mn2+. The enzyme showed activity for hydrolysis of soluble chitosan and glycol chitosan, but colloidal chitin, carboxymethyl cellulose, crystalline cellulose, and soluble starch were not hydrolyzed. The analysis of chitosan hydrolysis by thin‐layer chromatography and viscosity variation revealed that the purified enzyme should be endosplitting‐type chitosanase. CONCLUSION: The chitosanase produced by Bacillus subtilis RKY3 was a novel chitosanlytic enzyme with relatively low molecular weight, which is a versatile enzyme for chitosan hydrolysis because it could hydrolyze soluble chitosan into a biofunctional oligosaccharide at a high level. Copyright © 2011 Society of Chemical Industry 相似文献
139.
The effect of repetitive processing on the mechanical properties and fracture toughness of dynamically vulcanized isotactic polypropylene/ethylene‐propylene‐diene rubber blends (TPVs) with and without addition of β‐nucleating agent (β‐NA) was studied. The results showed that the repetitive processing did not cause much loss in the mechanical properties of TPVs, especially for TPVs with β‐NA, and TPVs with β‐NA showed better performance stability than TPVs without β‐NA. Essential work of fracture (EWF) approach was used to study the fracture behavior, and the results showed that the value of we (the specific essential work of fracture) of TPVs without β‐NA showed a significant decrease while that of TPVs with β‐NA almost kept constant after repetitive processing. Differential scanning calorimetry and wide‐angle X‐ray diffraction were used to study the variation of crystalline structures, and the results indicated that the repetitive processing showed no significant influence on the crystalline structures of TPVs, and the β‐NA maintained high‐nucleating efficiency after repetitive processing. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
140.
The mechanical and thermal characteristics and morphology of polyamide 6 (PA6)/isotactic polypropylene (iPP) blends (10/90 w/w) prepared with different processing procedures and incorporated with an aryl amide nucleating agent, a kind of β‐nucleating agent (β‐NA) for iPP, were investigated. The yield strength and flexural modulus of the blends decreased as β‐NA was introduced into the blends, whereas the impact strength and elongation at break improved. The crystalline structures of the blends closely depended on (1) the processing conditions and (2) competition between the β‐nucleating effect of β‐NA and the α‐nucleating effect of PA6 for iPP. Scanning electron microscopy, differential scanning calorimetry, and X‐ray diffraction were adopted to reveal the microstructures of the blends. At a low β‐NA content (<0.1 wt %), the α‐phase iPP dominated the blends, whereas the relative content of the β‐phase iPP increased remarkably when the β‐NA content was not less than 0.1 wt %. The processing conditions also showed profound influences on the supermolecular structures of iPP; this resulted in different mechanical properties of the blends. As for PA6, the crystallization behavior and crystalline structure did not exhibit obvious changes, but PA6 did play an important role in the epitaxial crystallization of iPP on PA6. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献