全文获取类型
收费全文 | 7843篇 |
免费 | 625篇 |
国内免费 | 373篇 |
专业分类
电工技术 | 91篇 |
综合类 | 729篇 |
化学工业 | 1174篇 |
金属工艺 | 840篇 |
机械仪表 | 135篇 |
建筑科学 | 1905篇 |
矿业工程 | 468篇 |
能源动力 | 173篇 |
轻工业 | 69篇 |
水利工程 | 883篇 |
石油天然气 | 1802篇 |
武器工业 | 13篇 |
无线电 | 32篇 |
一般工业技术 | 220篇 |
冶金工业 | 228篇 |
原子能技术 | 26篇 |
自动化技术 | 53篇 |
出版年
2024年 | 31篇 |
2023年 | 85篇 |
2022年 | 200篇 |
2021年 | 263篇 |
2020年 | 238篇 |
2019年 | 184篇 |
2018年 | 197篇 |
2017年 | 215篇 |
2016年 | 259篇 |
2015年 | 244篇 |
2014年 | 417篇 |
2013年 | 389篇 |
2012年 | 572篇 |
2011年 | 548篇 |
2010年 | 392篇 |
2009年 | 414篇 |
2008年 | 400篇 |
2007年 | 496篇 |
2006年 | 540篇 |
2005年 | 445篇 |
2004年 | 368篇 |
2003年 | 350篇 |
2002年 | 283篇 |
2001年 | 233篇 |
2000年 | 195篇 |
1999年 | 163篇 |
1998年 | 127篇 |
1997年 | 109篇 |
1996年 | 73篇 |
1995年 | 82篇 |
1994年 | 72篇 |
1993年 | 45篇 |
1992年 | 49篇 |
1991年 | 26篇 |
1990年 | 36篇 |
1989年 | 21篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1980年 | 4篇 |
1979年 | 10篇 |
排序方式: 共有8841条查询结果,搜索用时 15 毫秒
1.
2.
The methanol‐to‐olefins reaction (MTO) was studied in a small‐scale fluidized‐bed reactor over synthesized silicoaluminophosphate (SAPO‐34) catalysts. Mesoporous nanocrystalline SAPO‐34 molecular sieves were synthesized hydrothermally by ultrasonic and microwave‐assisted aging processes in the presence of hexadecyltrimethylammonium bromide (CTAB) and tetradecyldimethyl(3‐trimethoxysilylpropyl)ammonium chloride (TPOAC) as surfactant agents. The Box‐Behnken experimental design method was applied to determine the optimum operating parameters of this process conducted in the fluidized‐bed reactor. The optimum conditions in terms of reaction temperature, ratio of inlet gas velocity to minimum fluidizing velocity, and MeOH weight fraction were evaluated. 相似文献
3.
《Ceramics International》2022,48(8):10506-10515
The search for materials and methods capable of reducing human impacts on the environment is of utmost importance nowadays. This study's primary purpose was to analyze the technical feasibility of ceramic composites production utilizing Fundão Dam's Iron Ore Tailings (IOT), Blast Furnace Slag (BFS) from charcoal, and Foundry Sand (FS) as partial substitutes for the traditional raw materials – sand and clay – for application in building industry materials. The composites were molded in rectangular specimens and fired at temperatures of 900, 950, 1000, 1050, and 1200 °C. The developed materials were analyzed and characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Thermogravimetry (TGA), and Differential Thermal Analysis (DTA). The obtained materials had flexural strength modulus of up to 12.19 MPa, water absorption ranging from 2 to 22%, linear shrinkage ranging from 0.02 to 6.50%, and apparent density ranging from 2.03 to 1.63 g/cm3. The study of the internal structure formation process revealed the formation of amorphous structures in the composites. The results demonstrated that these waste materials may be jointly used in construction materials, contributing to the reduction of natural resource extraction, besides enabling their correct disposal, minimizing environmental impacts, and improving the life quality of the surrounding communities. 相似文献
4.
A hybrid fluidized-bed bioreactor for water purification was proposed and analyzed. It is a novel type of bioreactor characterized by hitherto unknown stationary and dynamic features. Steady-state characteristics of this hybrid bioreactor with external liquid circulation are presented. A quantitative analysis of steady-state properties of the bioreactor was performed with the aid of an original mathematical model developed for a double-substrate aerobic microbiological process. A steady-state analysis of aerobic processes characterized by different oxygen demand was performed. The effect of essential parameters was evaluated, including carbonaceous substrate concentration in the feed stream to the apparatus, aeration intensity, total residence time of a liquid in the bioreactor, and height of the bed of fine carrier particles. 相似文献
5.
6.
7.
琼东南盆地深水区经历了断陷、断拗和拗陷3大构造演化和沉积充填阶段,主要发育4种沉积体系,相应地形成了4类主要储层:1)陵三段扇三角洲或滨海相砂岩储层;2)三亚、梅山组滨浅海相砂岩储层;3)三亚—莺黄组低位体储层;4)梅山组台地边缘礁滩灰岩储层。平面上,储层发育具有明显的分带性,可划分为:北部浅水陆架滨岸砂岩、三角洲砂岩储层发育带;中央坳陷低位体储层发育带;南部永乐隆起区碳酸盐岩储层发育带。深水区主要位于后2个带,每个带储层发育的控制因素不同,可以进一步划分为多个储层发育区。每个储层发育区存在多套储盖组合,每套储盖组合在多个储层区中发育。其中台地灰岩储层可能成为南部隆起区具有重要意义的勘探层系。 相似文献
8.
9.