全文获取类型
收费全文 | 128533篇 |
免费 | 9942篇 |
国内免费 | 5726篇 |
专业分类
电工技术 | 5431篇 |
技术理论 | 26篇 |
综合类 | 10215篇 |
化学工业 | 18942篇 |
金属工艺 | 9280篇 |
机械仪表 | 10117篇 |
建筑科学 | 12590篇 |
矿业工程 | 6628篇 |
能源动力 | 3322篇 |
轻工业 | 13757篇 |
水利工程 | 3324篇 |
石油天然气 | 5145篇 |
武器工业 | 2591篇 |
无线电 | 12360篇 |
一般工业技术 | 11273篇 |
冶金工业 | 5411篇 |
原子能技术 | 820篇 |
自动化技术 | 12969篇 |
出版年
2024年 | 251篇 |
2023年 | 1676篇 |
2022年 | 2907篇 |
2021年 | 3798篇 |
2020年 | 3986篇 |
2019年 | 2923篇 |
2018年 | 2764篇 |
2017年 | 3734篇 |
2016年 | 4035篇 |
2015年 | 4414篇 |
2014年 | 8933篇 |
2013年 | 7795篇 |
2012年 | 9702篇 |
2011年 | 10146篇 |
2010年 | 7476篇 |
2009年 | 7642篇 |
2008年 | 7001篇 |
2007年 | 8668篇 |
2006年 | 7862篇 |
2005年 | 6691篇 |
2004年 | 5664篇 |
2003年 | 5022篇 |
2002年 | 4218篇 |
2001年 | 3497篇 |
2000年 | 2802篇 |
1999年 | 2212篇 |
1998年 | 1589篇 |
1997年 | 1298篇 |
1996年 | 1162篇 |
1995年 | 917篇 |
1994年 | 751篇 |
1993年 | 582篇 |
1992年 | 461篇 |
1991年 | 316篇 |
1990年 | 307篇 |
1989年 | 208篇 |
1988年 | 190篇 |
1987年 | 94篇 |
1986年 | 117篇 |
1985年 | 86篇 |
1984年 | 79篇 |
1983年 | 55篇 |
1982年 | 53篇 |
1981年 | 25篇 |
1980年 | 31篇 |
1979年 | 19篇 |
1978年 | 6篇 |
1975年 | 4篇 |
1959年 | 9篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
11.
Cellulose nanocrystals (CNCs) are a kind of sustainable nanoparticle from biomass, which are widely used as reinforcing filler and assembly building block for high-performance composites and function materials including biomaterial, optics, and so forth. Here, their unique advantages in material applications were reviewed based on their rod-like morphology, crystalline structure, dimension-related effects, and multi-level order structure. Then, we focused on the molecular engineering of CNCs, including the structure and physicochemical properties of their surface, along with surface modification methods and steric effects. We further discussed the performance-improvement and functionalization methods based on multi-component complex systems, together with the effects of surface molecular engineering on the performance and functions. Meanwhile, methods of optimizing orientation in uniaxial arrays were discussed along with those of enhancing photoluminescence efficiency via surface chemical modification and substance coordination. In the end, we prospected the design, development, and construction methods of new CNCs materials. 相似文献
12.
Callistus Nonso Ude Dominic Okechukwu Onukwuli Jonah Chukwudi Umeuzuegbu Chinemelum Chukwujekwu Chukwuka 《化学工程与技术》2021,44(1):65-76
The heterogeneous catalysis of transesterification of gmelina seed oil to biodiesel is evaluated. The oil was extracted from the seeds with n‐hexane by solvent extraction and characterized to determine its physiochemical properties. Response surface methodology was applied to optimize the effect of process variables on the biodiesel yield. The base‐activated clay catalyst performed as montmorillonite clay with the characteristic property of a Brønsted acid. It has an improved surface area after activation that enhanced its catalytic activity on transesterification reaction. Under optimal conditions, the biodiesel yield was 70.1 %, thus demonstrating that the model predicted well the biodiesel production. 相似文献
13.
纵观当今的发展格局,是科学技术高速发展的时代。随着5G时代的来临,网络技术在各个领域中扮演着越来越重要的角色。特别是在医疗方面,为医院的日常工作奠定了坚实的基础。今天就5G网络技术在医院只能服务中的应用展开谈论。 相似文献
14.
为解决沧州市涉地税源管理手段单一等问题,文中提出以测绘地理信息技术为支撑,通过对多源数据组织管理,建立风险分析指标,采用多种GIS空间分析方法构建了涉地风险税源识别模式并在沧州进行应用。结果表明:该模式能有效识别多种涉地风险,为涉地税源管理提供了支撑。 相似文献
15.
Shi-yuan XU Chu-ming LIU Ying-chun WAN Guang ZENG Yong-hao GAO Shu-nong JIANG 《中国有色金属学会会刊》2021,31(5):1291-1302
The corrosion behaviour of Mg-6Gd-3Y-1Zn-0.3Ag (wt.%) alloy components with different sizes after cooling was investigated. The alloys in the small components (SC) cooled fast, which were composed of α-Mg matrix and coarse long-period stacking ordered (LPSO) phases. The alloys in the large components (LC) cooled slowly, and there were thin lamellar LPSO phases precipitating inside the grains, except for α-Mg matrix and coarse LPSO phases. The hydrogen evolution test revealed that the corrosion rate of LC sample was higher than that of SC sample. Electrochemical impedance spectroscopy (EIS) test showed that the surface film on LC alloys provided worse protection. The corrosion morphologies indicated that the precipitation of the thin lamellar LPSO phases in LC sample caused severe micro-galvanic corrosion, which accelerated the rupture of the surface film. 相似文献
16.
分析近年来RTO装置发生的安全事故,找出了该类环保装置存在的安全风险,并在储罐与污水池废气分类处理、在线废气浓度检测仪与废气切断阀的位置设置、新风稀释及风机控制、阻火器与爆破片、操作压力、储罐呼吸阀后采用非接触废气罩收集、风机材质等方面提出了建议。 相似文献
17.
Naw Rutha PAW Takuma KIMURA Tatsuo ISHIJIMA Yasunori TANAKA Yusuke NAKANO Yoshihiko UESUGI Shiori SUEYASU Shu WATANABE Keitaro NAKAMURA 《等离子体科学和技术》2021,23(10):105505-203
Titanium dioxide (TiO2) nanopowder (P-25;Degussa AG) was treated using dielectric barrier discharge (DBD) in a rotary electrode DBD (RE-DBD) reactor.Its electrical and optical characteristics were investigated during RE-DBD generation.The treated TiO2 nanopowder properties and structures were analyzed using x-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR).After RE-DBD treatment,XRD measurements indicated that the anatase peak theta positions shifted from 25.3° to 25.1°,which can be attributed to the substitution of new functional groups in the TiO2 lattice.The FTIR results show that hydroxyl groups (OH) at 3400 cm-1 increased considerably.The mechanism used to modify the TiO2 nanopowder surface by air DBD treatment was confirmed from optical emission spectrum measurements.Reactive species,such as OH radical,ozone and atomic oxygen can play key roles in hydroxyl formation on the TiO2 nanopowder surface. 相似文献
18.
19.
《International Journal of Hydrogen Energy》2022,47(18):10204-10216
To improve hydrogen production (HP) performance of regular-porous structure (RPS), a columnar RPS with small specific surface area and high superficial area is developed. A numerical simulation model of regular-porous stainless steel structure (RPSSS) is established. Subsequently, heat transfer performance, pressure loss, temperature, methanol concentration, H2 concentration distributions and HP performance of the columnar RPSSS with small specific surface area and high superficial area and the body-centered cubic RPSSS with high specific surface area and small superficial area are compared. Then, temperature, methanol concentration, H2 concentration distributions and HP performance of axial and longitudinal size-enlarged columnar RPSSSs are studied. The results show that compared to the body-centered cubic RPSSS, the columnar RPSSS has higher methanol conversion, larger H2 flow rate and higher CO selectivity. Especially in the condition of 300 °C wall temperature and 12 mL/h methanol-water mixture injection rate (MWMIR), the methanol conversion, H2 flow rate and CO selectivity of the columnar RPSSS are increased by 12.3%, 9.24% and 30%, respectively, indicating that the superficial area of RPSSS is more important for its HP performance compared to its specific surface area. Compared to the longitudinal size-enlarged columnar RPSSS, the axial size-enlarged columnar RPSSS has higher methanol conversion, larger H2 flow rate and higher CO selectivity. This research work provides a new method for the optimization of hydrogen production reaction support (HPRS). 相似文献
20.
以禹州市梁北矿为研究区,利用2018年11月—2020年6月间35景5 m×20 m分辨率Sentinel-1A数据,采用InSAR技术,利用SBAS(短基线集InSAR)雷达干涉测量方法对梁北矿进行地面沉降信息提取解译,并通过实地调查成果认为,采用InSAR技术适合在矿区开展地表变形监测。 相似文献