全文获取类型
收费全文 | 113604篇 |
免费 | 11057篇 |
国内免费 | 5060篇 |
专业分类
电工技术 | 5194篇 |
技术理论 | 1篇 |
综合类 | 8967篇 |
化学工业 | 21590篇 |
金属工艺 | 10413篇 |
机械仪表 | 8398篇 |
建筑科学 | 11813篇 |
矿业工程 | 3626篇 |
能源动力 | 3785篇 |
轻工业 | 10055篇 |
水利工程 | 3004篇 |
石油天然气 | 4272篇 |
武器工业 | 1011篇 |
无线电 | 6895篇 |
一般工业技术 | 15810篇 |
冶金工业 | 5583篇 |
原子能技术 | 1251篇 |
自动化技术 | 8053篇 |
出版年
2024年 | 180篇 |
2023年 | 1915篇 |
2022年 | 3448篇 |
2021年 | 5041篇 |
2020年 | 3724篇 |
2019年 | 3452篇 |
2018年 | 3514篇 |
2017年 | 3576篇 |
2016年 | 4472篇 |
2015年 | 5261篇 |
2014年 | 6932篇 |
2013年 | 7461篇 |
2012年 | 7680篇 |
2011年 | 7708篇 |
2010年 | 5698篇 |
2009年 | 6119篇 |
2008年 | 5747篇 |
2007年 | 7813篇 |
2006年 | 7485篇 |
2005年 | 6258篇 |
2004年 | 4682篇 |
2003年 | 4172篇 |
2002年 | 3137篇 |
2001年 | 2312篇 |
2000年 | 1963篇 |
1999年 | 1501篇 |
1998年 | 1173篇 |
1997年 | 1014篇 |
1996年 | 1026篇 |
1995年 | 844篇 |
1994年 | 749篇 |
1993年 | 568篇 |
1992年 | 504篇 |
1991年 | 406篇 |
1990年 | 393篇 |
1989年 | 275篇 |
1988年 | 197篇 |
1987年 | 161篇 |
1986年 | 124篇 |
1985年 | 120篇 |
1984年 | 125篇 |
1983年 | 63篇 |
1982年 | 88篇 |
1981年 | 78篇 |
1980年 | 87篇 |
1979年 | 41篇 |
1978年 | 33篇 |
1977年 | 29篇 |
1964年 | 34篇 |
1962年 | 64篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
《Advanced Powder Technology》2022,33(8):103664
Powder transport systems are ubiquitous in various industries, where they can encounter single powder flow, two-phase flow with solids carried by gas or liquid, and gas–solid–liquid three-phase flow. System geometry, operating conditions, and particle properties have significant impacts on the flow behavior, making it difficult to achieve good transportation of granular materials. Compared to experimental trials and theoretical studies, the numerical approach provides unparalleled advantages over the investigation and prediction of detailed flow behavior, of which the discrete element method (DEM) can precisely capture complex particle-scale information and attract a plethora of research interests. This is the first study to review recent progress in the DEM and coupled DEM with computational fluid dynamics for extensive powder transport systems, including single-particle, gas–solid/solid–liquid, and gas–solid–liquid flows. Some important aspects (i.e., powder electrification during pneumatic conveying, pipe bend erosion, non-spherical particle transport) that have not been well summarized previously are given special attention, as is the application in some new-rising fields (ocean mining, hydraulic fracturing, and gas/oil production). Studies involving important large-scale computation methods, such as the coarse grained DEM, graphical processing unit-based technique, and periodic boundary condition, are also introduced to provide insight for industrial application. This review study conducts a comprehensive survey of the DEM studies in powder transport systems. 相似文献
2.
《Advanced Powder Technology》2022,33(11):103833
Eliminating the gold preg-robbing effect of carbonaceous matter in carbonaceous gold ores is crucial for gold leaching. In this study, suspension oxidation roasting was proposed to accelerate the decarbonization of carbonaceous gold ore. The characteristics of oxidation reaction process and gas release were analyzed by TG-DTA-FTIR. The phase transformation and microstructure evolution of samples during roasting were analyzed by XRD, SEM and BET. The results show that the gold preg-robbing effect was eliminated after the gasification of carbonaceous matter, and the CaO generated by decomposition of carbonates can effectively capture the SO2. After roasting for 75 min at 650 °C in a 20% O2 atmosphere, the total carbon removal rate reached 99.42%, the distribution of exposed gold increased from 28.85% to 77.10% and the gold leaching efficiency increased from 4.55% to 84.83%. In addition, about 70% sulfur was mainly fixed in the roasted products in the form of sulfate. Therefore, the suspension oxidation roasting process is an efficient and clean pretreatment method for carbonaceous gold ores. 相似文献
3.
《International Journal of Hydrogen Energy》2022,47(95):40407-40414
The present work addresses the potentialities of Pt–Ru nanoparticles deposited on a graphene oxide (RGO) and TiO2 composite support towards electrochemical oxidation of ethanol in acidic media relevant for fuel cell applications. To immobilize platinum–ruthenium bimetallic nanoparticles on to an RGO-TiO2 nanohybrid support a simple solution-phase chemical reduction method is utilized. An examination using electron microscopy and energy dispersive X-ray spectroscopy (EDS) indicated that Pt–Ru particles of 4–8 nm in diameter are dispersed on RGO-TiO2 composite support. The corresponding Pt–Ru/RGO-TiO2 nanocomposite electrocatalyst was studied for the electrochemical oxidation of ethanol in acidic media. Compared to the commercial Pt–Ru/C and Pt/C catalysts, Pt–Ru/RGO-TiO2 nanocomposite yields higher mass-specific activity of about 1.4 and 3.2 times, respectively towards ethanol oxidation reaction (EOR). The synergistic boosting provided by RGO-TiO2 composite support and Pt–Ru ensemble together contributed to the observed higher EOR activity and stability to Pt–Ru/RGO-TiO2 nanocomposite compared with other in-house synthesized Pt–Ru/RGO, Pt/RGO and commercial Pt–Ru/C and Pt/C electrocatalysts. Further optimization of RGO-TiO2 composite support provides opportunity to deposit many other types of metallic nanoparticles onto it for fuel cell electrocatalysis applications. 相似文献
4.
《International Journal of Hydrogen Energy》2022,47(61):25595-25607
Electrolysis of water for producing hydrogen instead of traditional fossil fuels is one of the most promising methods to alleviate environmental pollution and energy crisis. In this work, Fe and F ion co-doped Ni3S2 nanoarrays grown on Ni foam substrate were prepared by typical hydrothermal and sulfuration processes for the first time. Density functional theory (DFT) calculation demonstrate that the adsorption energy of the material to water is greatly enhanced due to the doping of F and Fe, which is conducive to the formation of intermediate species and the improvement of electrochemical performance of the electrode. The adsorption energy of anions (F and S) and cations (Fe and Ni) to water in each material was also calculated, and the results showed that F ion showed the most optimal adsorption energy of water, which proved that the doping of F and Fe was beneficial to improve the electrochemical performance of the electrode. It is worth noting that the surface of Fe–F–Ni3S2 material will undergo reconstruction during the process of water oxidation reaction and urea oxidation reaction, and amorphous oxides or hydroxides in situ would be formed on the surface of electrode, which are the real active species. 相似文献
5.
Hanna Seprina br Sembring Koo Bok Chin 《International Journal of Food Science & Technology》2022,57(4):2424-2434
Effects of different drying methods and different addition levels of eggplant (EP) on product quality of low-fat patties (LFPs) were investigated during storage. EP was dried in an oven dryer at 60 °C or a freeze dryer at −50 °C. LFPs were prepared by replacing with 1.5% soy protein isolate (SPI). Six treatments were used in this study: (1) control (CTL), without addition of EP; (2) reference (REF), 0.1% ascorbic acid; (3) O1, 0.25% oven-dried (OD) EP; (4) O2, 0.5% ODEP; (5) F1, 0.25% freeze-dried (FD) EP; and (6) F2, 0.5% FDEP. Redness (a*) and lightness (L*) values in LFPs added with EP were lower than those of others (p < 0.05) and decreased with increasing storage time. Yellowness (b*) values of cooked patties were increased during storage time (p < 0.05), with control having the highest value. The addition of EP or ascorbic acid into LFPs lowered microbial counts than control (p < 0.05). Thiobarbituric acid reactive substances (TBARS) was increased during storage, with REF having the lowest value, and patties added with EP had lower TBARS values than control during storage. Volatile basic nitrogen (VBN, mg%) contents of all patties also increased during storage time with O2 and F2 having lower values than control. Therefore, EP might have potential as a natural antioxidant in meat products during storage. 相似文献
6.
Donghai Xu Peng Feng Yang Wang Wanpeng Yang Yu Wang Shaoyan Sun 《American Institute of Chemical Engineers》2022,68(2):e17472
Corrosion and salt deposition problems severely restrict the industrialization of supercritical water oxidation. Transpiring wall reactor can effectively weaken these two problems by a protective water film. In this work, methanol was selected as organic matter, and the influences of vital structural parameters on water film properties and organic matter removal were studied via numerical simulation. The results indicate that higher than 99% of methanol conversion could be obtained and hardly affected by transpiration water layer, transpiring wall porosity and inner diameter. Increasing layer and porosity reduced reactor center temperature, but inner diameter's influence was lower relatively. Water film temperature reduced but coverage rate raised as layer, porosity, and inner diameter increased. Notably, the whole reactor was in supercritical state and coverage rate was only approximately 85% in the case of one layer. Increasing reactor length affected slightly the volume of the upper supercritical zone but enlarged the subcritical zone. 相似文献
7.
益生菌可在肠道定植从而发挥抗炎或抗氧化活性,有利于宿主肠道健康。本实验研究了从新疆传统发酵乳制品中分离得到的8?株植物乳杆菌对大肠杆菌侵袭和过氧化氢刺激肠上皮细胞HT-29的保护作用。结果表明:在8?株植物乳杆菌中,植物乳杆菌35具有最高的黏附能力。植物乳杆菌35可通过取代、竞争、排阻的方式抑制大肠杆菌对HT-29细胞的黏附,抑制率分别为42.60%、59.17%、60.19%。植物乳杆菌35及其多糖可抑制大肠杆菌刺激HT-29细胞产生白细胞介素-8;同时保护HT-29细胞免受过氧化氢的损伤,增加超氧化物歧化酶、谷胱甘肽过氧化物酶活力水平并降低丙二醛含量。结论:植物乳杆菌35及其粗胞外多糖具有抑制大肠杆菌O157诱导的炎症性肠病的潜力。 相似文献
8.
针对页岩油储层矿物组分复杂多样、矿物体积含量模型不统一、矿物组分准确定量评价困难等问题,以济阳坳陷陆相页岩油储层的岩心X衍射全岩矿物岩心分析和薄片鉴定等实验资料为基础,引入有机骨架,构建页岩油储层“双骨架”矿物组分岩石物理体积模型,在经过储层三孔隙度校正之后,采用最小二乘法-奇异值分解最优化反演方法计算页岩油储层有机骨架和无机骨架矿物组分体积含量。研究表明,采用最优化反演方法计算得到的矿物体积含量与X衍射测量结果相关性达到0.60以上,并在实际井中得到验证应用。研究成果可为页岩油储层精细评价提供有力支撑。 相似文献
9.
目的:探讨姜黄素的主要肠道代谢物四氢姜黄素(tetrahydrocurcumin,THC)对血小板活化和聚集的影响及其可能的分子机制。方法:在体外实验中,用不同浓度的THC(0、0.5、1、10 μmol/L)提前与健康人纯化血小板共同孵育40 min,然后加入凝血酶激活血小板2 min,用流式细胞术测定血小板表面CD62P和CD63的表达量,用酶联免疫吸附法测定血小板释放血小板因子-4(platelet factor-4,PF4)和趋化因子配体-5(chemokine ligand 5,CCL5)水平,用血小板聚集仪检测血小板释放ATP水平和血小板最大聚集率,用Western blot蛋白免疫印迹法检测血小板磷酸肌醇-3-激酶(phosphoinositide 3-kinase,PI3K)和Akt蛋白的磷酸化水平。结果:与模型组(血小板悬液中加入0.05%二甲基亚砜)相比,THC能抑制凝血酶诱导的血小板表面CD62P和CD63的表达,抑制PF4、CCL5和ATP的释放,降低血小板最大聚集率,下调PI3K和Akt蛋白的磷酸化水平,且呈浓度依赖效应,其中10 μmol/L的浓度下作用效果显著(P<0.01、P<0.001)。PI3K的特异性激动剂740 Y-P可部分逆转THC对PF4和CCL5释放和血小板聚集的抑制作用(P<0.05、P<0.01)。结论:THC具有显著抑制血小板活化和聚集的作用,其机制可能是THC可下调PI3K/Akt介导的信号通路。 相似文献