全文获取类型
收费全文 | 9065篇 |
免费 | 658篇 |
国内免费 | 139篇 |
专业分类
电工技术 | 149篇 |
综合类 | 367篇 |
化学工业 | 4089篇 |
金属工艺 | 98篇 |
机械仪表 | 138篇 |
建筑科学 | 317篇 |
矿业工程 | 120篇 |
能源动力 | 326篇 |
轻工业 | 3145篇 |
水利工程 | 73篇 |
石油天然气 | 91篇 |
武器工业 | 14篇 |
无线电 | 57篇 |
一般工业技术 | 564篇 |
冶金工业 | 221篇 |
原子能技术 | 25篇 |
自动化技术 | 68篇 |
出版年
2024年 | 70篇 |
2023年 | 126篇 |
2022年 | 190篇 |
2021年 | 236篇 |
2020年 | 316篇 |
2019年 | 281篇 |
2018年 | 328篇 |
2017年 | 441篇 |
2016年 | 385篇 |
2015年 | 319篇 |
2014年 | 490篇 |
2013年 | 1557篇 |
2012年 | 518篇 |
2011年 | 539篇 |
2010年 | 347篇 |
2009年 | 337篇 |
2008年 | 311篇 |
2007年 | 401篇 |
2006年 | 430篇 |
2005年 | 344篇 |
2004年 | 294篇 |
2003年 | 248篇 |
2002年 | 213篇 |
2001年 | 222篇 |
2000年 | 157篇 |
1999年 | 149篇 |
1998年 | 124篇 |
1997年 | 115篇 |
1996年 | 78篇 |
1995年 | 65篇 |
1994年 | 45篇 |
1993年 | 47篇 |
1992年 | 35篇 |
1991年 | 18篇 |
1990年 | 22篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1981年 | 1篇 |
1980年 | 5篇 |
1951年 | 1篇 |
排序方式: 共有9862条查询结果,搜索用时 15 毫秒
31.
Carbon Aerogels as Electrode Material in Supercapacitors 总被引:5,自引:0,他引:5
U. Fischer R. Saliger V. Bock R. Petricevic J. Fricke 《Journal of Porous Materials》1997,4(4):281-285
Due to their large specific surface area and their high electrical conductivity carbon aerogels are promising materials for electrodes in electrochemical double-layer capacitors (supercapacitor). The carbon aerogels were made via pyrolysis of resorcinol formaldehyde aerogels. The latter were prepared by supercritical and subcritical drying as well. The important findings of our investigation were, that the highest capacities of 46 F/cm3 were measured for samples with a density of about 800 kg/m3 pyrolyzed at 800°C. Also it was shown that RF-gels with molar resorcinol/catalyst ratios 1000 or higher can be dried subcritically without cracking or significant shrinkage. Carbon aerogels derived from these RF-aerogels have a small mesopore surface area, however an especially large micropore area. They provide electrical capacities which are most suitable for their use in supercapacitors. 相似文献
32.
33.
大冶硫酸四系列干吸塔结构特点 总被引:1,自引:0,他引:1
以干燥塔为例,介绍大冶公司硫酸四系列干吸塔的结构特点。除捕沫层简体及出气管为316L不锈钢外,其余塔体均为碳钢内衬瓷砖结构。塔底为球形底,中心排酸。采用槽管式分酸器,分酸点密度为43个/m^2,设可调闸板以保证各槽酸量均匀;闸板外设置带孔板的分布板,以消除进口酸的冲击,保证槽内酸液面平稳。比较了该塔与常规塔的不同之处,强调了设备节点的优化设计。 相似文献
34.
干燥、粉碎一体化装置 总被引:6,自引:0,他引:6
本文对干燥、粉碎一体化装置的典型设备惰性粒子流化床干燥器进行剖析,介绍应用情况,并作了经济性评价。 相似文献
35.
自然状态下岩土体中的三相组成处于动态变化之中,对土体热传导性能的准确测试造成困难,通过热导率脱湿曲线(TCDC)可间接获取土体的传热性能。为此,以桂林红黏土为研究对象,采用压力板仪和KD2 Pro土壤热特性分析仪,研究了红黏土在脱湿过程中热导率的变化规律。试验结果表明:在进气值之前,土体饱和度不变,3种干密度的土体热导率都有小幅度增加,此阶段主要与吸力变化引起的土体密实度变化有关;当吸力超过进气值后,热导率随饱和度减小逐渐减小,此阶段含水率为影响热导率的主要因素。基于热导率试验结果,采用Lu模型和William模型对红黏土脱湿过程中热导率变化曲线进行拟合,整体上2模型对试验结果拟合较好,可以用于红黏土脱湿过程中热导率变化的模拟。 相似文献
36.
37.
This study aimed to investigate the mechanical properties of concrete containing solid–liquid phase-change material (PCM) and focused on two key factors. First, a systematic study on the mechanical performance of PCM-modified concretes was conducted, including compressive, elastic modulus, and shrinkage tests. Second, because PCM provides high latent heat during the solid–liquid phase change, the effects of the solid phase and liquid phase on the mechanical properties of concrete were also explored. Results of this study showed that the solid–liquid phase of PCM affected the mechanical properties of concrete. For example, the compressive strength of 10% PCM concrete in solid phase (23 °C) and liquid phase (40 °C) at 28 days was 29.30 and 19.57 MPa, respectively. In addition, with increasing PCM content, the mechanical properties were degraded. For example, 10, 20, and 30% of PCM content lowered the compressive strength by 35.4, 58.4, and 74.3%, respectively. Therefore, concrete with PCM may not be suitable for structural elements. However, PCM is an important solution for optimizing energy consumption in modern buildings. It can absorb or emit large amounts of heat to store or release thermal energy. These properties can be used to control building temperatures resulting in energy saving and carbon reduction. 相似文献
38.
39.
针对混流式粮食干燥塔生产过程中,物理化学变化复杂,温度变化呈现的非线性和滞后性,难以准确检测的问题,提出了一种基于信息熵的温度预测方法;首先分别采用支持向量机和灰色预测独立建立第一降速段的温度模型;利用加权方法对两种模型进行集成,最后利用信息熵算法,对加权因子进行优化,提升模型的预测精度;运行结果表明干燥后的稻谷含水量与设定值误差从原来的±24.7%,降低至8.5%,验证本方法在实际生产中的有效性。 相似文献
40.
《Advanced Powder Technology》2023,34(10):104187
Layered lithium-nickel-manganese-cobalt oxide (NMC) cathode materials are widely used in Li-ion batteries that require high energy densities, such as those used in plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). Here we studied the synthesis of NMC622 particles by spray pyrolysis, which is a simple one-step process for production of spherical particles. However, synthesising NMC powder using spray pyrolysis has a tendency to produce hollow NMC particles. To gain insight into the mechanism behind the formation of the hollow particles, one dimensional numerical simulation of the physical and chemical phenomena taking place during spray drying were carried out. The effects of several process parameters, including drying air temperature, drying air mass flow rate, and liquid feed mass flow rate, on the evaporation and particle formation process were studied. The increased evaporation rate at higher temperatures was found to result in crust formation on the droplet surface during the particle formation, and thus, in lower solid volume fractions in the dried particles. However, by optimizing the process parameters production of solid NMC622 sulphate particles by spray drying was achieved. The produced NMC622 sulphate particles were then oxidised and lithiated in air at 850 °C via the conventional thermal treatment process. Four lithium precursors, LiOH, Li2CO3, Li2SO4 and LiNO3, were tested for the lithiation of the oxidized NMC particles. The degree of lithiation and the crystalline phase of the powders were determined using ICP-OES and XRD, respectively. 相似文献