全文获取类型
收费全文 | 1283篇 |
免费 | 110篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 14篇 |
综合类 | 4篇 |
化学工业 | 243篇 |
金属工艺 | 59篇 |
机械仪表 | 97篇 |
建筑科学 | 22篇 |
矿业工程 | 1篇 |
能源动力 | 77篇 |
轻工业 | 118篇 |
水利工程 | 4篇 |
无线电 | 240篇 |
一般工业技术 | 271篇 |
冶金工业 | 81篇 |
原子能技术 | 32篇 |
自动化技术 | 136篇 |
出版年
2024年 | 2篇 |
2023年 | 30篇 |
2022年 | 30篇 |
2021年 | 60篇 |
2020年 | 40篇 |
2019年 | 34篇 |
2018年 | 49篇 |
2017年 | 55篇 |
2016年 | 57篇 |
2015年 | 47篇 |
2014年 | 77篇 |
2013年 | 112篇 |
2012年 | 99篇 |
2011年 | 104篇 |
2010年 | 69篇 |
2009年 | 69篇 |
2008年 | 75篇 |
2007年 | 37篇 |
2006年 | 45篇 |
2005年 | 36篇 |
2004年 | 52篇 |
2003年 | 34篇 |
2002年 | 26篇 |
2001年 | 21篇 |
2000年 | 26篇 |
1999年 | 16篇 |
1998年 | 28篇 |
1997年 | 22篇 |
1996年 | 11篇 |
1995年 | 2篇 |
1994年 | 6篇 |
1993年 | 4篇 |
1992年 | 5篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 5篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 1篇 |
1981年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有1399条查询结果,搜索用时 46 毫秒
91.
Digital games appear to motivate players intrinsically. Of various game features, fantasy in particularly plays a crucial role in enhancing motivation and is a key factor in immersion in gameplay. As with its inherent value, fantasy also plays a vital role in distinguishing digital games itself from other media. Despite its significance, fantasy has received little attention, and this concept is still ambiguous to define with any certainty. This study thus aims to create a framework to explore a dimension of fantasy and to develop a scale to measure a state of fantasy in digital games. As a result, four factors were extracted, which were ‘identification’, ‘imagination’, ‘analogy’, and ‘satisfaction’, to account for fantasy state in digital gameplay. Based on these factors, a fantasy scale in digital games (FSDGs) included 16 items was developed. 相似文献
92.
An integral equation model for critical heat flux at subcooled and low quality flow boiling 总被引:1,自引:0,他引:1
A new theoretical model of critical heat flux (CHF) is developed for the flow boiling condition from bubble-detached to low quality range. The CHF condition is postulated to occur when the superheated liquid layer on the heated wall, which is formed under the bubbly layer from the point of the onset of significant void generation, is depleted due to the evaporation along the heated length. The model shows a very promising agreement with the uniformly heated round tube data for both water and refrigerants by simply applying well-known constitutive relationships without any tuning constant for the CHF data. The significance of the proposed model in unifying the existing models is also discussed. 相似文献
93.
Eun Gyo Lee Seung Hui Lee Kyung Mi Park Jung Eun Baek Sun Hee Yeon Jin‐Ki Park Won‐Kyong Chang Joon‐Ki Jung Bong Hyun Chung 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(5):643-649
BACKGROUND: Human erythropoietin (hEPO), a hydrophobic acidic glycoprotein responsible for the regulation of red blood cell production in mammals, is used for the treatment of anemia. In general, the purification of transgenic animal‐derived therapeutic proteins is not easy due to their low titer concentrations and abundant contaminant proteins. For the first time, here the purification and characterization of rhEPO from the milk of transgenic pigs are described. RESULTS: The rhEPO was purified by heparin chromatography, reverse‐phase chromatography, and gel filtration chromatography, resulting in a 16.5% yield and > 98% purity. The rhEPO purified from the milk of transgenic pigs contained less acidic isoforms and was underglycosylated in contrast to CHO‐derived rhEPO. Cell proliferation of the F‐36/EPO‐dependent cell line was proportional to the dose of transgenic pig‐derived rhEPO. CONCLUSION: Transgenic pig‐derived rhEPO with high purity was achieved after three‐step chromatography following two‐step precipitation. The transgenic pig‐derived rhEPO was demonstrated to have comparable potency with CHO‐derived rhEPO. Transgenic pig‐derived rhEPO may not be therapeutically feasible because of different glycosylation, and thus further studies are required to elucidate the effect of this aberrant glycosylation on the biological activity and stability in vivo. Copyright © 2008 Society of Chemical Industry 相似文献
94.
Myung-Sun Kim Kyunggon Kim Su Kyung Oh Gidae Lee Jin-Ock Kim Lan Li Jung-Hyun Park Kwang-Hyun Baek 《International journal of molecular sciences》2021,22(12)
To increase the half-life of growth hormones, we proposed its long-lasting regulation through the ubiquitin-proteasome system (UPS). We identified lysine residues (K67, K141, and K166) that are involved in the ubiquitination of human growth hormone (hGH) using ubiquitination site prediction programs to validate the ubiquitination sites, and then substituted these lysine residues with arginine residues. We identified the most effective substituent (K141R) to prevent ubiquitination and named it AUT-hGH. hGH was expressed and purified in the form of hGH-His, and ubiquitination was first verified at sites containing K141 in the blood stream. Through the study, we propose that AUT-hGH with an increased half-life could be used as a long-lasting hGH in the blood stream. 相似文献
95.
Junggeun Jhin Jong Hyeob Baek Dongjin Byun 《Journal of the Society for Information Display》2008,16(4):535-539
Abstract— The structural, electrical, and optical properties of GaN epilayers grown on various ion‐implanted sapphire(0001) substrates by MOCVD were investigated. GaN or AlN buffer layers and pre‐treatment were indispensably introduced before GaN‐epilayer growth. The ion‐implanted substrate's surface had decreased internal free energies during the growth of the ion‐implanted sapphire(0001) substrates. The crystal and optical properties of the GaN epilayers grown in ion‐implanted sapphire(0001) substrates were improved. Also, an excessively roughened and modified surface caused by ions degraded the GaN epilayers. Not only the ionic radius but also the chemical species of implanted sapphire(0001) substrates improved the properties of the GaN epilayers grown by MOCVD. It is obvious that the ion‐implanted pre‐treatment of sapphire(0001) substrates can be an alternative pre‐treatment procedure for GaN deposition and has the potential to improve the properties of the GaN epilayers on sapphire(0001) substrates. 相似文献
96.
Yong Che Kim Huhn Jun Kim Chang Hee Lee Baek Seok Seong Soon-Chul Kim 《Metals and Materials International》1998,4(6):1101-1109
Textures of metallic uranium rods were measured by neutron diffraction. From experimentally measured single and composite
pole figures, the crystallite orientation distribution function (ODF) was determined by the harmonic method using a computer
program developed for the fiber texture with orthorhombic crystal symmetry. The composite pole figures measured at overlapped
peak positions of the diffraction pattern were assumed to be a linear combination of several neighboring single pole figures.
The calculated results show that the harmonic method based on this conjecture well recovers the experimentally measured composite
pole figures. Anisotropie physical properties such as thermal expansion coefficients and elastic constants due to the texture
were evaluated by numerically averaging the second and fourth rank tensors with the calculated ODF, respectively. 相似文献
97.
Joon-Young Heo Min-Seok Baek Kwang-Jun Euh Kee-Ahn Lee 《Metals and Materials International》2018,24(5):992-1001
This study investigated the microstructure, tensile and fatigue properties of Al–5 wt.%Mg alloy manufactured by twin roll strip casting. Strips cast as a fabricated (F) specimen and a specimen heat treated (O) at 400 °C/5 h were produced and compared. In the F specimen, microstructural observation discovered clustered precipitates in the center area, while in the O specimen precipitates were relatively more evenly distributed. Al, Al6(Mn, Fe), Mg2Al3 and Mg2Si phases were observed. However, most of the Mg2Al3 phase in the heat-treated O specimen was dissolved. A room temperature tensile test measured yield strength of 177.7 MPa, ultimate tensile strength of 286.1 MPa and elongation of 11.1% in the F specimen and 167.7 MPa (YS), 301.5 MPa (UTS) and 24.6% (EL) in the O specimen. A high cycle fatigue test measured a fatigue limit of 145 MPa in the F specimen and 165 MPa in the O specimen, and the O specimen achieved greater fatigue properties in all fatigue stress conditions. The tensile and fatigue fracture surfaces of the above-mentioned specimens were observed, and this study attempted to investigate the tensile and fatigue deformation behavior of strip cast Al–5 wt.%Mg based on the findings. 相似文献
98.
99.
100.
Rectangular plates of the size of 1800 × 600 × 12 mm3 and 1200 × 600 × 12 mm3 were selected for injection molding and injection compression molding, respectively, in order to investigate warpage characteristics of the large‐sized polymer plates with orthogonal stiffener. To determine the mold system and to reduce warpage of the specimen, numerical analyses for injection molding and injection compression molding were performed by using a commercial simulation code. Experiments were performed to verify the suggested mold system and warpage of the specimen. Relatively large warpage of the injection molded product was observed and small warpage of the injection compression molded product was generated. Compression force of the injection compression molding was only 6% of the clamp force of the injection molding. Warpage of the product was reduced significantly by using the injection compression molding. The injection compression molding will be used to substitute expensive and disused wood forms with inexpensive and recyclable polymer plates for concrete casting. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献