全文获取类型
收费全文 | 11935篇 |
免费 | 336篇 |
国内免费 | 212篇 |
专业分类
电工技术 | 268篇 |
技术理论 | 1篇 |
综合类 | 505篇 |
化学工业 | 2817篇 |
金属工艺 | 481篇 |
机械仪表 | 745篇 |
建筑科学 | 239篇 |
矿业工程 | 403篇 |
能源动力 | 1519篇 |
轻工业 | 651篇 |
水利工程 | 78篇 |
石油天然气 | 2409篇 |
武器工业 | 70篇 |
无线电 | 225篇 |
一般工业技术 | 963篇 |
冶金工业 | 408篇 |
原子能技术 | 147篇 |
自动化技术 | 554篇 |
出版年
2024年 | 10篇 |
2023年 | 142篇 |
2022年 | 218篇 |
2021年 | 269篇 |
2020年 | 306篇 |
2019年 | 272篇 |
2018年 | 306篇 |
2017年 | 285篇 |
2016年 | 275篇 |
2015年 | 288篇 |
2014年 | 554篇 |
2013年 | 688篇 |
2012年 | 636篇 |
2011年 | 963篇 |
2010年 | 611篇 |
2009年 | 604篇 |
2008年 | 555篇 |
2007年 | 594篇 |
2006年 | 550篇 |
2005年 | 619篇 |
2004年 | 536篇 |
2003年 | 483篇 |
2002年 | 351篇 |
2001年 | 318篇 |
2000年 | 302篇 |
1999年 | 320篇 |
1998年 | 278篇 |
1997年 | 222篇 |
1996年 | 193篇 |
1995年 | 179篇 |
1994年 | 117篇 |
1993年 | 73篇 |
1992年 | 75篇 |
1991年 | 57篇 |
1990年 | 41篇 |
1989年 | 30篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 18篇 |
1985年 | 12篇 |
1984年 | 12篇 |
1983年 | 16篇 |
1982年 | 9篇 |
1981年 | 22篇 |
1980年 | 9篇 |
1979年 | 5篇 |
1978年 | 5篇 |
1977年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
《Ceramics International》2019,45(15):18838-18843
A gas exfoliation strategy for controllable preparation of boron nitride (BN) nanosheets with few-layered structure were reported. The green exfoliation process provides the BN nanosheets remarkable increment of adsorption capacities to organic contaminants, which is ascribed to better exposure of active sites originating from the larger surface area and thinner layer. Moreover, the prepared BN also exhibits outstanding recyclability. 相似文献
72.
《Ceramics International》2022,48(20):29659-29668
A simple strategy for synthesizing porous Co3O4 nanostructures through a hydrothermal process with subsequent thermal decomposition of the obtained Co(CO3)0·35Cl0·20(OH)1.10 precursors was introduced. To understand the growth mechanism of the Co(CO3)0·35Cl0·20(OH)1.10 precursors and realize morphology control of the resultant Co3O4 nanomaterials, a series of controlled experiments were carried out by varying CO(NH2)2 dosages, hydrothermal temperatures and time. The Co3O4 nanorods obtained under optimized synthesis conditions demonstrated porous structural features, which were constructed by well-connected nanograins, leaving many pores composed of the space between nanograins. The ethanol-sensing behaviors of these Co3O4 nanostructures were evaluated, showing the highest response (19.581) and a short response and recovery time (1 s/10 s) to 100 ppm ethanol. Moreover, the Co3O4 sensor demonstrated excellent anti-interference ability toward several interfering gases such as methanol, benzene hexane, and dichloromethane. The stability of the Co3O4 sensor was further confirmed by 14 days of continuous testing. Compared with previously reported works, this Co3O4 sensor still demonstrated outstanding gas sensing properties due to its unique advantages such as 1D porous nanostructures, high BET surface area, abundant oxygen vacancies, and active cobalt sites. 相似文献
73.
Marisa De Sousa Duarte Matthieu Rolland Corinne Sagnard Didier Suire Frederic Flacher Olivier Delpoux Charles P. Lienemann 《化学工程与技术》2019,42(3):655-660
A 3‐MPa, 350 °C fixed‐bed reactor was designed to follow‐up gas‐liquid‐solid reactions on a millimetric size heterogeneous catalyst with Raman spectroscopy. The transparent reactor is a quartz cylinder enclosed in a Joule effect heated stainless‐steel tube. A methodology to determine how to focus the microscope for liquid and solid phase characterization is presented. The setup was validated by performing diesel hydrodesulfurization on a CoMo/alumina extrudate catalyst with a conversion very close to expected values along with the acquisition of Raman spectra of the solid catalyst showing an evolution of the catalyst phase during sulfidation. 相似文献
74.
Lei Meng Ping Zhou Ying Yan Dongming Guo 《International Journal of Hydrogen Energy》2021,46(29):15965-15975
The compressive deformation of gas diffusion layer (GDL), which is highly nonlinear and related to the loading history, affects the performance of PEM fuel cell stacks. However, linear elastic models are widely used. In this study, a new nonlinear constitutive model is proposed to describe the compression properties. Macroscopic studies reveal that GDL has different mechanical properties during the first and repeated compression stages. Besides, the tangent modulus has a significant linear relationship with stress. The constitutive model can be rebuilt using the micro-mechanical theory of fiber assemblies by considering the bending of carbon fibers. Furthermore, a prediction method is proposed to describe cyclic compression behavior. The prediction results fit well with the test results with an average and maximum relative error of less than 5.30% and 18.13%, respectively. These conclusions are beneficial to the design of GDL with specific mechanical properties and the real-time analysis of PEM fuel cell. 相似文献
75.
《International Journal of Hydrogen Energy》2021,46(69):34463-34468
To solve the problem of measuring the combustion temperature of hydrogen gas, an improved two-colour pyrometer with suspended tungsten powder was developed and calibrated by a tungsten halogen lamp. The characteristic temperature parameters of the premixed 30% H2/70% air flame, including temperature distribution, proportion, maximum value, minimum value, and average value, could be measured and calculated using the improved two-colour pyrometer method and a python code. The temperature measuring results of H2-air mixture obtained by this technique were compared with that of thermocouples and previous studies. The results verified its feasibility to measure the flame temperature structure of H2 combustion. Future work concerning the influential factors of the improved two-colour pyrometer was also mentioned. 相似文献
76.
针对带扩张段构型的发动机燃烧室,采用欧拉-拉格朗日仿真方法研究喷注方式、喷孔参数及隔离段燃烧室构型的改变对于射流雾化效果的影响,用以更好地指导发动机设计.结果表明,在保证发动机总体流量不变的条件下,喷孔孔径减小或者喷孔总数量减少使得液气动量通量比增大,有利于同时增大单孔射流穿透深度以及液滴展向宽度.贫燃工况下如当量比为0.7条件下,射流流量减小,混合效果可能变差.而在发动机结构设计方面,隔离段到燃烧室的过渡设计不宜采用大转角,15°转角是相对较为理想的设计方案.采用小角度突扩构型设计比渐扩构型更容易找到相对好的点火位置. 相似文献
77.
Gas‐liquid‐liquid slug flow in a capillary reactor is a promising new concept that allows one to incorporate gas‐liquid reaction, liquid‐liquid extraction, and facile catalyst separation in a single unit. In order to assess the performance of a gas‐liquid‐liquid slug flow reactor, it is necessary to predict the slug velocity and pressure drop to ascertain residence times and reaction rates. New empirical models for velocity and pressure drop were developed based on existing models for two‐phase gas‐liquid and liquid‐liquid slug flows, and these were validated experimentally. 相似文献
78.
Muhammad Zia ul Mustafa Hilmi bin Mukhtar Nik Abdul Hadi Md Nordin Hafiz Abdul Mannan Rizwan Nasir Nabilah Fazil 《化学工程与技术》2019,42(12):2580-2593
Flue gas emissions and the harmful effects of these gases urge to separate and capture these unwanted gases. Ionic liquids due to negligible vapor pressure, thermal stability, and wide electrochemical stability have expanded its application in gas separations. A comprehensive overview of the recent developments and applications of ionic liquid membranes (ILMs) for gas separation is given. The three general classifications of ILMs, such as supported ionic liquid membranes (SILMs), ionic liquid polymeric membranes (ILPMs), and ionic liquid mixed‐matrix membranes (ILMMMs) along with their applications, for the separation of various mixed gases systems is discussed in detail. Furthermore, issues, challenges, computational study, and future perspectives for ILMs are also considered. 相似文献
79.
《Journal of the European Ceramic Society》2019,39(2-3):508-513
Content, evolution and diffusion characteristics of water and gases in fine-crystalline spinel MgAl2O4 were studied by kinetic thermodesoption mass spectrometry. Water is the main volatile component by quantity in the spinel structure. From the spinel crystals with an average size of 0.52 μm, water is released in vacuum in three temperature ranges: at 100–200 °C due to desorption from micropores, at 300–600 °C due to near-surface dehydroxylation and at 500–800 °C due to diffusion of water from the crystal bulk. The content of structural water, diffusively released from the crystals, is about 3000 ppm. The coefficients and activation energy of diffusion of water from spinel crystals in the range 500–700 °C were calculated. This allows us to estimate at any temperature the degassing time of the spinel with a certain degree of dispersion and ceramics made of it, and thereby promote the production of high-quality ceramics. 相似文献
80.
《International Journal of Hydrogen Energy》2021,46(59):30442-30454
In a proton exchange membrane fuel cell (PEMFC), effective GDL surface water elimination is significant to water management. This paper used the volume-of-fluid method (VOF) method to carry out simulation research on transferring liquid water in the flow channel with a hydrophilic pipe. The findings indicated that compared with a straight channel, a hydrophilic pipe structure could effectively remove water from the gas diffusion surface (GDL) and reduce the surface water coverage of the GDL. With the increase in the diameter and height of the pipe structure, the GDL surface's water coverage first increased and then decreased, and it was less with the pipe structure than with the direct flow channel. The removal rate of water on the GDL surface was accelerated. The spacing of hydrophilic pipes has a significant impact on the transportation of water. As the spacing increases, the removal rate of water on the GDL surface slowed. A hydrophilic pipe structure with a diameter of 75 μm, a height of 400 μm, and spacing of 300 μm has good water removal performance on the GDL surface. This research work proposes a new internal structure design of the flow channel, which has specific implications for removing water on the GDL surface. 相似文献