全文获取类型
收费全文 | 5958篇 |
免费 | 992篇 |
国内免费 | 71篇 |
专业分类
电工技术 | 76篇 |
综合类 | 257篇 |
化学工业 | 3874篇 |
金属工艺 | 43篇 |
机械仪表 | 87篇 |
建筑科学 | 164篇 |
矿业工程 | 11篇 |
能源动力 | 327篇 |
轻工业 | 606篇 |
水利工程 | 21篇 |
石油天然气 | 46篇 |
武器工业 | 4篇 |
无线电 | 295篇 |
一般工业技术 | 1049篇 |
冶金工业 | 36篇 |
原子能技术 | 42篇 |
自动化技术 | 83篇 |
出版年
2024年 | 34篇 |
2023年 | 164篇 |
2022年 | 122篇 |
2021年 | 321篇 |
2020年 | 309篇 |
2019年 | 285篇 |
2018年 | 273篇 |
2017年 | 288篇 |
2016年 | 277篇 |
2015年 | 304篇 |
2014年 | 333篇 |
2013年 | 334篇 |
2012年 | 486篇 |
2011年 | 401篇 |
2010年 | 312篇 |
2009年 | 278篇 |
2008年 | 279篇 |
2007年 | 307篇 |
2006年 | 291篇 |
2005年 | 276篇 |
2004年 | 210篇 |
2003年 | 205篇 |
2002年 | 168篇 |
2001年 | 117篇 |
2000年 | 97篇 |
1999年 | 98篇 |
1998年 | 81篇 |
1997年 | 81篇 |
1996年 | 51篇 |
1995年 | 45篇 |
1994年 | 39篇 |
1993年 | 37篇 |
1992年 | 30篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 5篇 |
1988年 | 11篇 |
1987年 | 6篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 6篇 |
1983年 | 1篇 |
1982年 | 4篇 |
1981年 | 1篇 |
1979年 | 1篇 |
1951年 | 7篇 |
排序方式: 共有7021条查询结果,搜索用时 0 毫秒
101.
102.
103.
A novel wearable sensor system was developed for monitoring respiration and pulse using polyvinylidene fluoride (PVDF) piezoelectric films as sensor materials. Due to the different signal intensity between respiration and pulse, a “double-sided arch” structure and a “thin-shell” structure were designed and fabricated as substrates for the respiratory sensor and pulse sensor, respectively. These sensors installed on belts can be easily tied on the chest, abdomen, or wrist for comfortable fit. In order to obtain clear respiratory and pulse signals from the sensor patch, some high-quality signal processing modules were designed. The digital signals were transmitted to a computer via Bluetooth and displayed by LabVIEW software. The fundamental principle and functional verification of the developed sensor system were described in this study. By comparing the sensor signals from the proposed structure with those of flat structure, it can be concluded that the proposed sensor is more sensitive and stable than its flat counterpart. In addition, the whole sensor system has the features of ease of use and comfortable to wear. All these make the proposed sensor system a promising sensing device for respiration and pulse real time monitoring. 相似文献
104.
The selective separation of carbon dioxide (CO2) from a wet gaseous mixture of CO2/H2 through facilitated transport membranes containing immobilized aqueous solutions of monoethanolamine (MEA), diethanolamine (DEA), ethylenediamine (EDA) and monoprotonated ethylenediamine (EDAH+) and their blends was experimentally investigated. The effect of CO2 partial pressure, amine concentration, feed side pressure and amine species on the CO2 and H2 permeances were studied. The CO2 permeability through amine solution membranes decreased with increasing CO2 feed partial pressure but the H2 permeance was almost independent of the H2 partial pressure. A comparison of experimental results showed that single or blended amines with low viscosity and a moderate equilibrium constant, i.e., large forward and reverse reaction rate of CO2‐amine, are suitable for effective separation of CO2. The permeability of CO2 generally increased with an increase in amine concentration, although this increase may be compromised by the salting out effect and decrease in diffusivities of species. The results obtained indicated that CO2 permeance across a variety of amines are in the order of DEA (2 M) > MD (2 M) > MD (1 M) > MEA (2 M) > MEA (4 M) > MD (4 M) > DEA (1 M) > DEA (4 M) > MEA (1 M) for various concentrations of MEA + DEA blend and are in the order of EDAH+ (2 M) > DEA (2 M) > MH (2 M) > DH (2 M) > ED (2 M) > EDA (2 M) > MEA (2 M) for various blends of amine. 相似文献
105.
A series of sulfonated copolyimides (SPIs) with hydrophilic segment length of 20–60 based on 4,4′‐sulfide‐bis(naphthalic anhydride) (SBNA) have been successfully synthesized to improve hydrolytic stability and proton conductivity. The SPI membranes were cast from their m‐cresol solutions, and they were characterized by determining the water uptake, water swelling ratio, mechanical properties, hydrolytic stability, oxidative stability, and proton conductivity. It was found that the water uptake of SPI membranes was low and decreased as the hydrophilic segment length increased, which led to good dimensional stability. In addition, the SPI membranes with low ion‐exchange capacity (IEC) value displayed excellent hydrolytic stability and retained good mechanical properties even after harsh hydrolysis testing, in which the block SPI with hydrophilic segment length of 40 had the best hydrolytic stability, while those with high IEC value showed an apparent decrease. All of the block SPI membranes show better conductivity than the random ones at the temperature range from 30 to 70°C. Interestingly, the proton conductivities of random SPI membranes were higher than that of corresponding block ones at 90°C. The block SPI with hydrophilic segment length of 40 gave the highest proton conductivity as the temperature increased among the block SPIs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41501. 相似文献
106.
Various types of synthetic polymeric membranes have been fabricated for separation purposes in industry/laboratory. Zeolite is ceramic-based material and well known for its antiwear resistance and high mechanical strength. Mixed matrix membranes are the latest membrane technology constituting inorganic nanoparticle phase and organic polymer phase. The review represents various types and applications of zeolite-reinforced polymeric membranes. Consequently, fabrication procedure and working principle of zeolite-reinforced mixed matrix (polyimide, polysulfone, polycarbonate) membranes have been discussed. The significant relevance of polymer/zeolite membranes is in water purification, medical, catalytic, and gas separation industries. Improvement in polymeric membrane properties has been observed through incorporation of zeolite filler. 相似文献
107.
108.
Ye Yuan Yurui Pan Menglong Sheng Guangyu Xing Ming Wang Jixiao Wang Zhi Wang 《中国化学工程学报》2022,50(10):168-176
Membrane technology features inspiring excellence from numerous separation technologies for CO2 capture from post-combustion gas. Polyvinylamine (PVAm)-based facilitated transport membranes show significantly high separation performance, which has been proven promising for industrial scale-up. However, commercialized PVAm with low molecular weight and excessive crystallinity is not available to prepare high-performance membranes. Herein, the synthesis process of PVAm was optimized by regulating polymerization and acidic hydrolytic conditions. The membranes based on PVAm with a molecular weight of 154 kDa and crystallinity of 11.37% display high CO2 permeance of 726 GPU and CO2/N2 selectivity of 55 at a feed gas pressure of 0.50 MPa. Furthermore, we established a PVAm synthesis reactor with an annual PVAm solution (1%(mass)) capacity of over 7000 kg and realized the scaled-up manufacture of both PVAm and composite membranes. 相似文献
109.
Perfluorosulfonated ionomers membranes: Melt‐processing and characterization for ion exchange applications 下载免费PDF全文
Perflurosulfonated ionomers membranes with different ionic‐exchange capacity were successfully fabricated via melt‐extruding and casting of their –SO2F precursors. A systematical investigation of the thermal stability, crystallinity, and rheological properties of the precursors was performed to secure their optimized processing conditions. The tensile properties of acid‐form membranes are found to increase with base‐hydrolysis time, where a tensile strength of 38.2 MPa is readily obtained after 24 h's base‐hydrolysis. The content of –SO2F or –SO3H containing side‐chains plays an important role in the thermal stability, rheological, and mechanical properties of the precursor or the acid‐form membranes. The strong ionic interactions, attributed to the –SO3H groups, lead to decreased crystallinity and tensile strength for different IEC membranes. The acid‐form membranes exhibit good proton conductivity and low methanol crossover in comparison with reference Nafion membrane. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39944. 相似文献
110.
Catherine Lefranc-Millot Dominique Vercaigne-Marko Pascal Dhulster Bertrand Fertin Bernard Quinque Didier Guillochon 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1996,66(1):79-85
A method for the production of bovine colostral F(ab′)2 fragments at pilot-plant scale was developed. Optimum yield of immunoglobulins in colostral whey was obtained after rennet treatment of first milking colostrum. Pepsin digestion was carried out directly on the colostral whey at pH 3·8 for 4 h, which led to the complete digestion of immunoglobulins into F(ab′)2 fragments. Elimination of β-lactoglobulin, the main immunogenic protein, was achieved by anion exchange on Duolite A560 at pH 6·0. The preparation was diafiltered with a 5000 Da membrane and the retentate spray-dried. The powder obtained contained approximately 34% F(ab′)2 fragments, with an antibody activity three times higher than the initial colostrum. 相似文献