全文获取类型
收费全文 | 27467篇 |
免费 | 1804篇 |
国内免费 | 280篇 |
专业分类
电工技术 | 529篇 |
综合类 | 357篇 |
化学工业 | 5849篇 |
金属工艺 | 1110篇 |
机械仪表 | 1752篇 |
建筑科学 | 968篇 |
矿业工程 | 159篇 |
能源动力 | 1053篇 |
轻工业 | 2260篇 |
水利工程 | 211篇 |
石油天然气 | 252篇 |
武器工业 | 31篇 |
无线电 | 4355篇 |
一般工业技术 | 5393篇 |
冶金工业 | 1822篇 |
原子能技术 | 397篇 |
自动化技术 | 3053篇 |
出版年
2024年 | 26篇 |
2023年 | 341篇 |
2022年 | 463篇 |
2021年 | 875篇 |
2020年 | 634篇 |
2019年 | 639篇 |
2018年 | 869篇 |
2017年 | 867篇 |
2016年 | 956篇 |
2015年 | 847篇 |
2014年 | 1261篇 |
2013年 | 1732篇 |
2012年 | 1831篇 |
2011年 | 2197篇 |
2010年 | 1640篇 |
2009年 | 1719篇 |
2008年 | 1547篇 |
2007年 | 1233篇 |
2006年 | 1129篇 |
2005年 | 968篇 |
2004年 | 830篇 |
2003年 | 738篇 |
2002年 | 771篇 |
2001年 | 645篇 |
2000年 | 572篇 |
1999年 | 579篇 |
1998年 | 834篇 |
1997年 | 495篇 |
1996年 | 495篇 |
1995年 | 308篇 |
1994年 | 224篇 |
1993年 | 191篇 |
1992年 | 145篇 |
1991年 | 133篇 |
1990年 | 99篇 |
1989年 | 110篇 |
1988年 | 83篇 |
1987年 | 73篇 |
1986年 | 63篇 |
1985年 | 53篇 |
1984年 | 42篇 |
1983年 | 33篇 |
1982年 | 33篇 |
1981年 | 29篇 |
1980年 | 32篇 |
1979年 | 17篇 |
1977年 | 28篇 |
1976年 | 42篇 |
1975年 | 17篇 |
1974年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
991.
Yoonsang Park Hossein Daneshpajooh Timo Scholehwar Eberhard Hennig Kenji Uchino 《Journal of the European Ceramic Society》2021,41(12):5900-5908
The IEEE standard to determine physical parameters of piezoceramics has been utilized for decades by many researchers, yet it omits presence of important loss factors and possesses serious deficits that restrict accurate parameter determination. To resolve these issues, the partial electrode (PE) method was previously proposed, though the focus has been merely made on development of the method itself. In this study, we provide method simplification and more detailed analysis. The omission of unnecessary samples greatly boosts experiment and analysis process. To prove that the PE method is reliable, possible causes of errors were investigated; it is shown that they were either negligibly small or can be resolved with proper calibration. Furthermore, Applicability of PE method to various types of piezoceramic materials and compatibility with impedance analyzers are shown. Finally, PE method is proved to be reliable and can be alternative to IEEE Standard on Piezoelectricity. 相似文献
992.
Chul Soon Yong Mi-Kyung Lee Young-Joon Park Kyung-Hwan Kong Jing Ji Xuan Ji-Hyun Kim 《Drug development and industrial pharmacy》2013,39(7):615-622
To improve the oral bioavailability of poorly water-soluble ibuprofen with poloxamer and menthol, the effects of menthol and poloxamer 188 on the aqueous solubility of ibuprofen were investigated. The dissolution and pharmacokinetic study of ibuprofen delivered by the ibuprofen-loaded preparations composed of poloxamer 188 and menthol were then performed. In the absence of poloxamer, the solubility of ibuprofen increased until the ratio of menthol to ibuprofen increased from 0:10 to 4:6 followed by an abrupt decrease in solubility above the ratio of 4:6, indicating that four parts menthol formed eutectic mixture with six parts ibuprofen. In the presence of poloxamer, the solutions with the same ratio of menthol to ibuprofen showed an abrupt increase in the solubility of ibuprofen. The poloxamer gel with menthol/ibuprofen ratio of 1:9 and higher than 15% poloxamer 188 showed the maximum solubility of ibuprofen, 1.2 mg/mL. The simultaneous addition of menthol and poloxamer 188 significantly improved the dissolution rates of ibuprofen from aqueous solution due to the ibuprofen solubility-improving effect of menthol in the presence of poloxamer. Furthermore, the ibuprofen-loaded preparation with menthol and poloxamer 188 gave significantly higher initial plasma concentrations, Cmax, and AUC of ibuprofen than did the preparation without menthol and poloxamer 188, indicating that the simultaneous addition of menthol and poloxamer 188 could improve the oral bioavailability of ibuprofen in rats. In modern pain management it is always desirable for the ibuprofen-loaded preparation with poloxamer 188 and menthol to show a rapid onset of action with a minimal phase of lag time to feel the decreased pain. From an industry point of view, it is more desirable for a formulation to be fast acting, easy to use, and cost effective. Thus, the ibuprofen-loaded preparation with poloxamer 188 and menthol was a more effective oral dosage form for poorly water-soluble ibuprofen. 相似文献
993.
994.
This paper proposes a new extended Process to Product Modeling (xPPM) method for integrated and seamless information delivery manual (IDM) and model view definition (MVD) development. Current IDM development typically uses Business Process Modeling Notation (BPMN) to represent a process map (PM). Exchange requirements (ERs) and functional parts (FPs) specify the information required when information is exchanged between different activities. A set of information requirements, specifically defined as a subset of Industry Foundation Classes (IFC), is called an MVD. Currently however, PMs, ERs, FPs, and MVDs are developed as separate documents through independent development steps. Moreover, even though ERs and FPs are designed to be reused, tracking and reusing the ERs and FPs developed by others is practically impossible. The xPPM method is proposed to provide a tight connection between PMs, ERs, FPs, and MVDs and to improve the reusability of predefined ERs and FPs. The theoretical framework is based on the approach of the Georgia Tech Process to Product Modeling (GTPPM) to suit the IDM development process. An xPPM tool is developed, and the validity of xPPM is analyzed through the reproduction of existing IDMs and MVDs. The benefits and limitations of xPPM and lessons from the applicability tests are discussed. 相似文献
995.
Jong-Seok Park Youn-Mook Lim Min-Ho Youn Hui-Jeong Gwon Young-Chang Nho 《Korean Journal of Chemical Engineering》2012,29(7):931-934
We prepared biodegradable polycaprolactone/cuttlebone scaffold composite by salt leaching process. In the first step, a co-continuous blend of biodegradable materials, polycaprolactone (PCL) and cuttlebone (CB), and an amount of sodium chloride salt particles were mixed using a stirrer. Next, the extraction of mineral salts using de-ionized distilled water was performed using a biodegradable PCL/CB scaffold with fully interconnected pores. Finally, the durable morphology of the scaffolds was fabricated by freeze-drying process at ?53 °C for 24 hrs in a vacuum. In addition, the quadrilateral pres ranged from about 250 to 300 ??m in diameter. Scanning electron microscopy (SEM) and mercury intrusion porosimeter techniques were carried out to characterize the pore morphology. By increasing the CB and sodium chloride salt particle content, the number of interconnected pores, material properties, and pore morphology were dramatically changed. The average compressive strengths (load at 50% strain) of the different porous PCL/CB scaffolds were found to decrease from 133 to about 79 (load at 50% strain, gf) with an increase in porosity. The values of the porosity increased as the sodium chloride salt volume fraction increased 相似文献
996.
Despite the wider introduction of the buy online and pick up in-store (BOPS) service by retailers, research on BOPS is still sparse, especially those from the consumer perspective. This paper employs the scenario-based factorial survey method to investigate how the perceived characteristics of innovation and the perceived risk of online shopping influence the consumers’ intention to use BOPS while also considering the moderating effects of situational factors (location convenience) and product type (involvement). Our findings indicated that the consumer perceptions of relative advantage, complexity, compatibility, and risks involved in online shopping are important antecedents to intention to use BOPS, and that these relationships were significantly moderated by locational convenience and product involvement. The implications of the findings and suggestions for future research are discussed in detail. 相似文献
997.
Korean rice varieties, ‘Druryechanbyeo’ and ‘Boramchanbyeo’, were developed to get higher yields and to be used in rice products.
The rice grains were dried and milled into rice flours after first going through the soaking process. The properties and qualities
of cupcakes made with dry-milled rice flours were compared with cupcakes made with commercial dry-milled rice flours (CDRF).
The newly developed rice flours (NDRF) had higher apparent amylose content, water binding capacity, swelling power, and peak
viscosities, but had lower damaged-starch content, gelatinization temperature, and final and setback viscosities than CDRF.
The specific gravity of batter, and hardness and springiness of cupcakes were lower in NDRF than in CDRF. The cake textures
from ‘Boramchan’ NDRF were more preferable than those from ‘Druyechan’ NDRF. The specific volume and overall quality of cupcake
were correlated positively with amylose content and water binding capacity, but negatively with damaged starch of rice flours. 相似文献
998.
In this paper, we present a method for reconstructing a surface mesh animation sequence from point cloud animation data. We mainly focus on the articulated body of a subject — the motion of which can be roughly described by its internal skeletal structure. The point cloud data is assumed to be captured independently without any inter‐frame correspondence information. Using a template model that resembles the given subject, our basic idea for reconstructing the mesh animation is to deform the template model to fit to the point cloud (on a frame‐by‐frame basis) while maintaining inter‐frame coherence. We first estimate the skeletal motion from the point cloud data. After applying the skeletal motion to the template surface, we refine it to fit to the point cloud data. We demonstrate the viability of the method by applying it to reconstruct a fast dancing motion 相似文献
999.
1000.
Jeom Yong Choi Si Woo Hwang Kyung-Tae Park 《Metallurgical and Materials Transactions A》2013,44(2):597-601
Extended ductility over 70 pct was realized in duplex stainless steel by implementing twinning-induced plasticity (TWIP). The steel also exhibited the tensile strength over 800 MPa. The steel chemistry was designed so that the stacking fault energy of austenite was high enough to induce TWIP during deformation. After the initial decrease, the strain hardening rate increased at high tensile strains above ~30 pct. The microstructures of austenite at such high strains were manifested by well-developed primary twins and nanotwins between them, which effectively block dislocation motion. This observation ensures that extended ductility and high strength of a newly designed duplex stainless steel are originated from TWIP in austenite. 相似文献