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61.
Hiroya Nakata Takayoshi Kiguchi Osamu Hino 《Journal of the American Ceramic Society》2022,105(4):2791-2803
To understand the role of phosphate ester dispersant, we investigated the rheology of a BaTiO slurry. For the model case, a coarse-grain molecular dynamics (CGMD) simulation was performed with the butyral polymer didodecyl hydrogen phosphate (DHP) in the toluene/ethanol solvent. By systematically analyzing the effect of DHP from an atomic-scale first principle and from all-atom MD to microscale CGMD simulation, we investigated how the adsorption of a DHP dispersant on a BaTiO surface affects the microstructure rheology of a BaTiO slurry. The first-principle and all-atom MD simulation suggests that DHP molecules prefer to locate near the BaTiO surface. CGMD simulation shows a reduction in viscosity with an increase in dispersants, suggesting that the dispersant population near the BaTiO surface plays a key role in controlling the rheology of the BaTiO slurry. In this study, we propose an approach for understanding the BaTiO slurry with molecular-level simulations, which would be a useful tool for efficient optimization of slurry preparation. 相似文献
62.
Both confocal Raman microspectroscopy and atomic force microscopy (AFM) have been undertaken to study the crystalline and the morphological aspects of cast PA 6 films at a sub-microscopic scale. The percentages of the different crystalline structures present within PA 6 cast films, i.e. the monoclinic α, the pseudo-hexagonal β, and the monoclinic γ, have been measured by confocal Raman microspectroscopy. In cast films, the prevailing structure is the β one. AFM has been used to characterize the morphology of the PA 6 films. Simultaneously, the deformed state has been considered as well. Our main interest has been to follow the evolution of the percentage of each crystalline structure as a function of the plastic deformation mechanisms which are responsible of the yielding of PA 6 films: shear banding for temperatures T lower than 160 °C and formation of fibrils for 相似文献
63.
Xiaozhen Yang 《Polymer》2004,45(12):4241-4248
The conformational distribution change of amorphous poly(lactic acid) (PLA) induced by deformation has been studied using Raman spectroscopy. Spectroscopic features associated with the rotational isomeric states (ttt, ttg′, tg′t, tg′g′) have been established experimentally and supported by normal coordinate analysis. Deformation induced a significant increase in the most favorable tg′t conformation. Based on the relative intensities of Raman-active skeletal modes, a quantitative method has been developed that can be used to elucidate structural changes in a variety of deformed polymer samples. For biaxially oriented PLA films, the overall tg′t conformation increased from the 76% in undeformed sample to a value as high as 92%. The change in conformational distribution in the amorphous phase follows a different trend (76-88%) as compared to the increase in sample crystallinity (0-43%). A large change in amorphous chain conformation occurred at relatively low draw ratios. In contrast, the large change in the degree of crystallinity occurred at higher draw ratios. 相似文献
64.
High-temperature decomposition of hydrocarbons may lead to the formation of carbon deposits. However in our present studies, we found that the morphology of carbon deposits over MgO supported Fe catalyst during chemical vapor deposition (CVD) process was closely related to the thermodynamic properties and chemical structures of hydrocarbon precursors. Six kinds of hydrocarbons (methane, hexane, cyclohexane, benzene, naphthalene and anthracene) were used as carbon precursors in this study. Methane which has a pretty simple composition and is more chemically stable was favorable for the formation of high-purity single walled carbon nanotubes (SWNTs). For high-molecular weight hydrocarbons, it was found that the chemical structures rather than thermodynamic properties of carbon precursors would play an important role in nanotube formation. Specifically, the CVD processes of aromatic molecules such as benzene, naphthalene and anthracene inclined to the growth of SWNTs. While the cases of aliphatic and cyclic hydrocarbon molecules seemed a little more complicated. Based on different pyrolytic behaviors of carbon precursors and formation mechanism of SWNTs and multi-walled carbon nanotubes (MWNTs), a possible explanation of the difference in CVD products was also proposed. 相似文献
65.
A. Barrera J.A. Montoya M. Viniegra J. Navarrete G. Espinosa A. Vargas P. del Angel G. Prez 《Applied Catalysis A: General》2005,290(1-2):97-109
The catalytic performance of mono- and bimetallic Pd (0.6, 1.0 wt.%)–Pt (0.3 wt.%) catalysts supported on ZrO2 (70, 85 wt.%)–Al2O3 (15, 0 wt.%)–WOx (15 wt.%) prepared by sol–gel was studied in the hydroisomerization of n-hexane. The catalysts were characterized by N2 physisorption, XRD, TPR, XPS, Raman, NMR, and FT-IR of adsorbed pyridine. The preparation of ZrW and ZrAlW mixed oxides by sol–gel favored the high dispersion of WOx and the stabilization of zirconia in the tetragonal phase. The Al incorporation avoided the formation of monoclinic-WO3 bulk phase. The catalysts increased their SBET for about 15% promoted by Al2O3 addition. Various oxidation states of WOx species coexist on the surface of the catalysts after calcination. The structure of the highly dispersed surface WOx species is constituted mainly of isolated monotungstate and two-dimensional mono-oxotungstate species in tetrahedral coordination. The activity of Pd/ZrW catalysts in the hydroisomerization of n-hexane is promoted both with the addition of Al to the ZrW mixed oxide and the addition of Pt to Pd/ZrAlW catalysts. The improvement in the activity of Pd/ZrAlW catalysts is ascribed to a moderated acid strength and acidity, which can be correlated to the coexistence of W6+ and reduced-state WOx species (either W4+ or W0). The addition of Pt to the Pd/ZrAlW catalyst does not modify significantly its acidic character. Selectivity results showed that the catalyst produced 2MP, 3MP and the high octane 2,3-dimethylbutane (2,3-DMB) and 2,2-dimethylbutane (2,2-DMB) isomers. 相似文献
66.
Carbon-encapsulated Fe nanoparticles with size between 5 and 20 nm were synthesized via a picric acid-detonation-induced pyrolysis of ferrocene, which is characterized by a self-heating and extremely fast process. The nanoparticles exhibit well-constructed core-shell structures, with bcc-Fe cores and graphitic shells. The graphitic shells can protect effectively the cores against the attack of HNO3 solution. The formation of the core-shell nanoparticles can be selectively controlled by adjusting the composition of the picric acid-ferrocene mixture, which determines C/Fe atomic ratio of the reaction system. The core-shell nanoparticles are preferably formed at low C/Fe atomic ratios, while tubular structures are formed at high C/Fe ratio. The possible pathway for the carbon-encapsulated Fe nanoparticles formation is discussed briefly. 相似文献
67.
68.
Under the applied high reaction temperatures (900 K) the Ag surface is restructured and a tightly held oxygen species is formed on the surface (O) apart from O atoms dissolved in the bulk (O). Methanol oxidation to formaldehyde proceeds through this O species as demonstrated by application of a variety of spectroscopic techniques. 相似文献
69.
Poly(methylphenylene) (PMeP) films were prepared by direct oxidation of toluene in the mixed electrolytes of boron trifluoride diethyl etherate (BFEE) and trifluoroacetic acid (TFA). The oxidation potential of toluene in pure BFEE was measured to be 1.52 V versus saturated calomel electrode (SCE). This value was much lower than that determined in a neutral medium such as acetonitrile (2.13 V versus SCE). The introduction of TFA into BFEE decreased the oxidation potential of toluene and also improved the properties of as‐formed polymer films. Infrared and Raman spectra confirmed the formation of PMeP films. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 189–195, 2004 相似文献
70.
本文主要介绍了用微波等离子体化学气相沉积法(以下简称MP CVD法)以甲醇-氢气混合气和丙酮-氢气混合气为源气体,分别以单晶硅的(111)面和人造金刚石的(100)面为衬底材料,制备出了面积为20mm×20mm厚为10μm的多晶金刚石膜和面积为1.0mm×1.0mm厚为5μm的单晶金刚石膜。通过试验发现,源气体配比和衬底温度对薄膜质量起决定性作用。另外,衬底在反应腔中的位置对薄膜的生成也有很大影响。单晶金刚石膜制备过程中衬底金刚石的晶体取向与金刚石薄膜的生长及质量有密切的关系。在金刚石的(100),(110)和(111)面上分别获得了单晶金刚石膜和金刚石多晶粒子。选用扫描电镜、显微激光拉曼、反射电子衍射对多晶金刚石膜及单晶金刚石膜的性能进行了测试。 相似文献