全文获取类型
收费全文 | 22976篇 |
免费 | 3260篇 |
国内免费 | 1576篇 |
专业分类
电工技术 | 3953篇 |
技术理论 | 2篇 |
综合类 | 1819篇 |
化学工业 | 4614篇 |
金属工艺 | 1924篇 |
机械仪表 | 1381篇 |
建筑科学 | 792篇 |
矿业工程 | 221篇 |
能源动力 | 1906篇 |
轻工业 | 605篇 |
水利工程 | 183篇 |
石油天然气 | 248篇 |
武器工业 | 172篇 |
无线电 | 2522篇 |
一般工业技术 | 3347篇 |
冶金工业 | 581篇 |
原子能技术 | 226篇 |
自动化技术 | 3316篇 |
出版年
2024年 | 151篇 |
2023年 | 574篇 |
2022年 | 753篇 |
2021年 | 963篇 |
2020年 | 1097篇 |
2019年 | 990篇 |
2018年 | 835篇 |
2017年 | 1064篇 |
2016年 | 976篇 |
2015年 | 994篇 |
2014年 | 1379篇 |
2013年 | 1487篇 |
2012年 | 1511篇 |
2011年 | 1917篇 |
2010年 | 1404篇 |
2009年 | 1401篇 |
2008年 | 1382篇 |
2007年 | 1588篇 |
2006年 | 1328篇 |
2005年 | 1066篇 |
2004年 | 879篇 |
2003年 | 710篇 |
2002年 | 618篇 |
2001年 | 515篇 |
2000年 | 428篇 |
1999年 | 342篇 |
1998年 | 284篇 |
1997年 | 240篇 |
1996年 | 177篇 |
1995年 | 156篇 |
1994年 | 159篇 |
1993年 | 109篇 |
1992年 | 72篇 |
1991年 | 65篇 |
1990年 | 46篇 |
1989年 | 39篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 13篇 |
1985年 | 17篇 |
1984年 | 11篇 |
1983年 | 8篇 |
1982年 | 4篇 |
1981年 | 5篇 |
1980年 | 8篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1964年 | 1篇 |
1959年 | 1篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
A novel phosphorus‐ and silica‐containing hybrid (DPS) was synthesized by the reaction between diethyl phosphate (DEP) and polyhedral oligomeric siloxanes (POS) formed by hydrolysis condensation of 3‐glycidoxypropyltrimethoxysilane (GPTMS). The novel phosphorus‐ and silica‐containing hybrid was characterized by the flourier transform infrared spectroscope (FT‐IR), silicon nuclear magnetic resonance, and gel permeation chromatography (GPC). Then, the determination of the activation of the reaction between epoxy resin and phosphorus‐, and silica‐containing hybrids was studied by differential scanning calorimeter (DSC). In the presence of catalyst, the activation energies of the curing reaction were 63.3 and 66.7 kJ/mol calculated by Kissinger model and Ozawa model respectively. The thermal and flame retardant properties of the cured epoxy modified by DPS were determined by differential scanning calorimeter (DSC), thermal gravimetric analysis (TGA), and limited oxygen index (LOI). The results revealed that those properties were improved in comparison with unmodified epoxy resin. In addition, scanning electron microscopy (SEM) was used to investigate the morphology of the cured epoxy resin modified by DPS. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
992.
A study on the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide batteries 下载免费PDF全文
Masoud Sabzi Saeid Mersagh Dezfuli 《International Journal of Applied Ceramic Technology》2018,15(6):1446-1458
In this study, the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide batteries have been investigated. For this purpose, firstly four silver oxide electrodes containing 5, 10, 15, and 20 wt% carbon powder were produced by powder metallurgy method. For the next step, all four silver oxide electrodes were sintered at 500°C for 10 minutes. Afterward and in order to investigate the microstructure, phase and elemental analysis of the electrodes were carried out using Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), X‐ray Diffraction (XRD), and Energy Dispersive Spectroscopy (EDS), respectively. Moreover, in order to investigate the effect of compositing silver oxide nanoparticles by carbon on the electrochemical behavior and electronic properties of zinc‐silver oxide, electrochemical tests (potentiodynamic polarization and electrochemical impedance spectroscopy) and electric discharge test in 1.4 wt%KOH electrolyte were carried out respectively. The microstructural observations revealed that increasing carbon content in the silver oxide electrodes results in increasing the apparent porosities in these electrodes. Investigating the phase and elemental analysis results showed that by increasing the content of carbon in the silver oxide electrode, the amount of Ag2O and AgO phases in this electrode reduces and also the extent of pure silver formation increases. Investigations on the results of electrochemical tests showed that increasing carbon content results in the reduction of corrosion resistance in silver oxide electrodes. Moreover, the results of electric discharge test revealed that the silver oxide electrode containing 10wt% carbon yields the highest energy efficiency in the zinc‐silver oxide batteries. 相似文献
993.
选用纳米金属Cu和碳素材料石墨烯纳米片(GnPs)为改性剂分别添加至十四酸(MA)中,制备出Cu质量分数为1%、2%、3%和4%的Cu/MA混合相变蓄热材料及GnPs质量分数为1%、2%和3%的GnPs/MA混合相变蓄热材料,并对混合相变材料性能进行表征。结果表明:Cu/MA固态和液态热导率随Cu质量分数增加呈线性提高,1%(质量)GnPs/MA固态热导率较纯MA显著提高101.51%,随GnPs质量分数增加,热导率增幅减缓;FT-IR谱图表明Cu与MA及GnPs与MA间的混合均为物理作用;DSC结果显示添加Cu或GnPs可降低MA的过冷度和相变潜热,且随质量分数增加,相变潜热逐渐降低;4%(质量)Cu/MA和3%(质量)GnPs/MA放热时间相比于纯MA分别减少了23.4%和38.7%;4%(质量)Cu/MA和3%(质量)GnPs/MA在经历300次快速热循环试验后,晶体结构和相变温度基本保持不变,相变潜热分别降至168 J·g-1和181 J·g-1左右,仍满足蓄放热要求,两种材料均具有良好的热循环稳定性。 相似文献
994.
The relatively low capacitance of negative electrodes, as compared to the capacitance of advanced positive electrodes, poses a serious problem, since this limits the development of asymmetric supercapacitor (SC) devices with a large voltage window and enhanced power-energy characteristics. We fabricate negative SC electrodes with a high capacitance that match the capacitance of advanced positive electrodes at similar active mass loadings, as high as 37?mg?cm?2. Cyclic voltammetry, impedance spectroscopy, galvanostatic charge-discharge data and the power-energy characteristics of the asymmetric SC device exhibit good electrochemical performance for a voltage window of 1.6?V. Our approach involves the development and application of particle extraction through liquid-liquid interface (PELLI) methods, new extraction mechanisms and efficient extractors to synthesize α-FeOOH and β-FeOOH electrode materials. The use of PELLI allows agglomerate-free processing of powders, which facilitates their efficient mixing with multiwalled carbon nanotubes (MWCNT) and allows improved electrolyte access to the particle surface. Experiments to determine the properties of FeOOH-MWCNT composites provided insight into the influence of the electrode material and the structure of extractor molecules on the composite properties. The highest capacitance of 5.86?F?cm?2 for negative electrodes and low impedance were achieved using α-FeOOH-MWCNT composites and a 16-phosphonohexadecanoic acid (PHDA) extractor. This extractor allows adsorption on particles, not only at the liquid-liquid interface, but also in the bulk aqueous phase and can potentially be used as a capping agent for particle synthesis and as an extractor in the PELLI method. 相似文献
995.
Yaşar K. Recepoğlu İdil Yılmaz-Ipek Müşerref Arda Mithat Yüksel Kazuharu Yoshizuka 《分离科学与技术》2018,53(6):856-862
Direct release of geothermal waters to the environment may cause some damages to some plants because they contain toxic species such as boron, arsenic, fluoride etc. along with valuable minerals including lithium. In this study, a hybrid process combining adsorption and membrane filtration was used to separate boron and lithium simultaneously from geothermal water. According to the results obtained, separation efficiencies for lithium and boron from geothermal water were 100% and 83% using boron selective ion exchange resin Dowex XUS-43594.00 and lithium selective λ-MnO2 adsorbent, respectively. The kinetic data of lithium and boron adsorption have been evaluated using pseudo-first order and pseudo-second-order kinetic models. 相似文献
996.
997.
As a family of functional inorganic clusters, polyoxometalates (POMs) were introduced into hybrid self-assemblies with the assistance of the supramolecular interaction with diverse organic cationic molecules, which reinforced both the processibility and functionality of the POMs. This method not only improved the surface properties of the POMs, but also provided excellent amphiphilic building blocks for the construction of advanced self-assembled nanostructures. In this review, we summarize the fundamental aspects of surfactant-encapsulated POMs (SEPs) and the most recent progress in potential applications of SEPs and the related POM-containing systems (hybrids composed of POMs and polymers and other cationic molecules beyond surfactants). The functionalization of such organic/inorganic hybrids in self-assembled systems is also described. Furthermore, perspectives regarding self-assemblies and possible applications of POM complexes with synergetic interactions between organic and inorganic components are outlined. 相似文献
998.
Serena Berardi Mauro Carraro Andrea Sartorel Gloria Modugno Marcella Bonchio 《Israel journal of chemistry》2011,51(2):259-274
Organic–inorganic hybrids based on polyoxometalate scaffolds(POMs) are a unique class of molecular metal-oxides featuring a composite surface, whereby the merging of complementary domains stimulates new functions and enhances performances. The interaction between the organic and inorganic components can be designed via covalent and/or non-covalent strategies, yielding novel molecular systems with key applications in catalysis and materials science. Selected examples of such a rewarding approach will be illustrated, including the synthesis of tailored POM-based catalysts, and their application in homogeneous systems and on electrocatalytic surfaces for water splitting and renewable energy production. 相似文献
999.
Polyacrylate/silica hybrid latexes (PAES) with high silicon contents (up to 21%) were prepared by directly mixing colloidal silica with polyacrylate emulsion (PAE) modified by a silane coupling agent. Sol–gel-derived organic/inorganic thin films were obtained by addition of hydrophilic co-solvents to PAES and subsequent drying at room temperature. The effects of co-solvents and γ-methacryloxypropyltrimethoxysilane (KH570) content on the properties of PAES films were investigated. Dynamic light scattering (DLS) data indicated that the average diameter of PAES (96 nm) was slightly larger than that of PAE (89 nm). TEM photo revealed that colloidal silica particles were dispersed uniformly around polyacrylate particles and that some of the colloidal silica particles were adsorbed on the surface of PAE particles. The data of crosslinking degree and FT-IR spectra confirmed that the chemical structure of the PAES changed to form Si–O–Si-polymer crosslinking networks during the film formation. AFM photos, contact angle for water, and XPS analysis showed that the polyacrylate/inorganic hybrid films with high silicon contents were formed by the co-solvent-mediated, sol–gel method and that the Si-based polymers were uniformly distributed on the surface of the dried films. TGA data demonstrated that the PAES films display much better thermal stability than the PAE counterpart. 相似文献
1000.
Upendra A. Joshi James R. Darwent Humphrey H. P. Yiu Matthew J. Rosseinsky 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2011,86(8):1018-1023
BACKGROUND: This research investigated the effect of platinum (Pt) on the reactivity of tungsten oxide (WO3) for the visible light photocatalytic oxidation of dyes. RESULTS: Nanocrystalline tungsten oxide (WO3) photocatalysts were synthesised by a sol‐gel process and employed for the photocatalytic degradation of Methyl Orange under visible light. For comparison commercial bulk WO3 materials were also studied for the same reaction. These materials were fully characterised using X‐ray diffraction (XRD), UV‐visible diffuse reflection spectroscopy and transmission electron microscopy (TEM). The photocatalytic oxidation of iso‐propanol was used as a model reaction to follow the concomitant reduction of molecular oxygen. No reactions occured in the absence of platinum, which is an essential co‐catalyst for the multi‐electron reduction of oxygen. The platinised WO3 catalysts were stable for multiple oxidation–reduction cycles. The results from the catalytic activity measurements showed that platinised nanocrystalline WO3 is a superior oxidation photocatalyst when compared with bulk WO3. Methyl Orange was completely decolourised in 4 h. CONCLUSIONS: The enhanced performance of nanocrystalline Pt‐WO3 is attributed to improved charge separation in the nanosized photocatalyst. Platinum is an essential co‐catalyst to reduce oxygen. This photocatalyst could be applied to the treatment of organic pollutants in wastewater, with the advantage of using visible light compared with the widely studied TiO2, which requires UV light. Copyright © 2011 Society of Chemical Industry 相似文献