全文获取类型
收费全文 | 19309篇 |
免费 | 1454篇 |
国内免费 | 1098篇 |
专业分类
电工技术 | 546篇 |
综合类 | 2354篇 |
化学工业 | 2172篇 |
金属工艺 | 4965篇 |
机械仪表 | 1608篇 |
建筑科学 | 990篇 |
矿业工程 | 393篇 |
能源动力 | 205篇 |
轻工业 | 956篇 |
水利工程 | 142篇 |
石油天然气 | 1000篇 |
武器工业 | 253篇 |
无线电 | 1281篇 |
一般工业技术 | 2548篇 |
冶金工业 | 1323篇 |
原子能技术 | 67篇 |
自动化技术 | 1058篇 |
出版年
2024年 | 80篇 |
2023年 | 264篇 |
2022年 | 376篇 |
2021年 | 401篇 |
2020年 | 461篇 |
2019年 | 357篇 |
2018年 | 366篇 |
2017年 | 520篇 |
2016年 | 561篇 |
2015年 | 604篇 |
2014年 | 1111篇 |
2013年 | 904篇 |
2012年 | 1248篇 |
2011年 | 1417篇 |
2010年 | 1228篇 |
2009年 | 1201篇 |
2008年 | 1035篇 |
2007年 | 1356篇 |
2006年 | 1304篇 |
2005年 | 1099篇 |
2004年 | 1005篇 |
2003年 | 948篇 |
2002年 | 797篇 |
2001年 | 666篇 |
2000年 | 544篇 |
1999年 | 380篇 |
1998年 | 265篇 |
1997年 | 270篇 |
1996年 | 260篇 |
1995年 | 160篇 |
1994年 | 149篇 |
1993年 | 81篇 |
1992年 | 95篇 |
1991年 | 62篇 |
1990年 | 45篇 |
1989年 | 47篇 |
1988年 | 26篇 |
1987年 | 19篇 |
1986年 | 7篇 |
1985年 | 13篇 |
1984年 | 21篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1979年 | 11篇 |
1963年 | 6篇 |
1962年 | 7篇 |
1961年 | 7篇 |
1958年 | 9篇 |
1956年 | 5篇 |
1955年 | 10篇 |
排序方式: 共有10000条查询结果,搜索用时 462 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(40):17737-17748
Due to problems such as pores on surface-treated coatings, the corrosion resistance of pure titanium bipolar plates for proton-exchange membrane fuel cells can be further improved by increasing the corrosion resistance of pure titanium by using differential speed-rolling (DSR); however, these materials have not yet reached the standard requirements of bipolar plates (corrosion current density icorr<103 nA·cm?2). In this work, the corrosion resistance of pure titanium was improved by optimizing the DSR process while the strength was maintained. The best corrosion resistance of the DSR pure titanium was achieved when the roller speed ratio was 2, while icorr was 429 nA·cm?2 in a solution of 0.5 M H2SO4 and 2 mg/L HF at room temperature. The formability of the DSR pure titanium for bipolar plates was verified. The optimal holding pressure range was 6.8–7.0 kN. 相似文献
2.
3.
Poly(l ‐lactic acid) (PLLA) is a biodegradable and biocompatible thermoplastic polyester produced from renewable sources, widely used for biomedical devices, in food packaging and in agriculture. It is a semicrystalline polymer, and as such its properties are strongly affected by the developed semicrystalline morphology. As a function of the crystallization temperature, PLLA can form different crystal modifications, namely α′‐crystals below about 120 °C and α‐crystals at higher temperatures. The α′ modification is therefore of special importance as it may be the preferred polymorph developing at processing‐relevant conditions. It is a metastable modification which typically transforms into the more stable α‐crystals on annealing at elevated temperature. The structure, kinetics of formation and thermodynamics of α′‐ and α‐crystals of PLLA are reviewed in this contribution, together with the effect of α′‐/α‐crystal polymorphism on the properties of PLLA. © 2018 Society of Chemical Industry 相似文献
4.
Xuewu Li Lin Zhang Tian Shi Weining Yu Jinhui Shao Xuegang Zhou Yuxing He Binbin Zhang 《工业材料与腐蚀》2021,72(5):951-959
Ti-based amorphous metallic glasses have excellent mechanical, physical, and chemical properties, which is an important development direction and research hotspot of metal composite reinforcement. As a stable, simple, efficient, and large-scale preparation technology of metallic powders, the gas atomization process provides an effective way of preparing amorphous metallic glasses. In this study, the controllable fabrication of a Ti-based amorphous powder, with high efficiency, has been realized by using gas atomization. The scanning electron microscope, energy-dispersive spectrometer, and X-ray diffraction are used to analyze surface morphology, element distribution, and phase structure, respectively. A microhardness tester is used to measure the mechanical property. An electrochemical workstation is used to characterize corrosion behavior. The results show that as-prepared microparticles are more uniform and exhibit good amorphous characteristics. The mechanical test shows that the hardness of amorphous powder is significantly increased as compared with that before preparation, which has the prospect of being an important part of engineering reinforced materials. Further electrochemical measurement shows that the corrosion resistance of the as-prepared sample is also significantly improved. This study has laid a solid foundation for expanding applications of Ti-based metallic glasses, especially in heavy-duty and corrosive domains. 相似文献
5.
构建工程咨询机构BIM技术应用能力评价的指标体系,提出改进的熵权TOPSIS评价模型,以4个典型的工程咨询单位为例,进行BIM技术运用能力评价。研究表明,BIM行业的整体水平已经有了明显的提升,但是区域间的发展还存在一定差距。 相似文献
6.
7.
This paper analyzes the problems existing in the teaching of data structure course, and puts forward the reform from the as-
pects of strengthening basic programming, visualized explanation of abstract theory, combination of C++, Java programming, ratio-
nal use of online platform, and stratification of exercises, aiming at improving students' practical ability, learning interest and self-
confidence. 相似文献
8.
为探究[Zr_(0.73)(Cu_(0.59)Ni_(0.41))_(0.27)]_(87)Al_(13)非晶合金的热塑性成形性能以及绘制其对应的热加工图谱,用Gleeble3500型热模拟压缩实验机对该非晶合金进行不同参数下的热模拟压缩实验。结果表明,合金在压缩过程中变形行为由牛顿流变演变为非牛顿流变;同时,过高或过低的热加工温度均能导致合金晶化;进一步对数据分析得到该合金在不同热塑性成形参数下的功率耗散图与流变失稳图,并绘制出相应的热加工谱图,谱图分析结果表明,该合金在温度为420与430℃、应变速率为10~(-3) s~(-1)时具有较高功率耗散系数且没有失稳区域,因此,合金可选的热塑性加工参数为温度420~430℃,应变速率10~(-3) s~(-1)。 相似文献
9.
The aim of this study was to investigate the structure and corrosion resistance of amorphous, amorphous‐crystalline, and crystalline Mg67Zn29Ca4 alloy for biodegradable applications. This paper presents a preparation method and results of the structural characterization and corrosion resistance analysis of the material. Samples were prepared in the form of 3 mm diameter rods. The structure of the alloy was examined with the use of X‐ray diffractometry and scanning electron microscopy. The thermal properties of the samples were examined with differential scanning calorimetry (DSC). Results of DSC analysis were used to determine heat treatment temperatures, allowing to obtain different fractures of crystalline phase in the material. Corrosion resistance of heat‐treated samples was investigated by immersion tests and electrochemical measurements performed in the simulated body fluid. The X‐ray diffraction results confirmed that the prepared Mg67Zn29Ca4 alloy's structure is fully amorphous. After heat treatment, samples with different fractions of amorphous phase in the structure were obtained. Immersion tests of the samples showed that the structure significantly influenced corrosion resistance in examined materials. It should be pointed out, that certain amounts of crystalline phase in amorphous matrix can greatly improve the corrosion resistance of Mg67Zn29Ca4 alloy. 相似文献
10.
Kazuaki Katagiri Shinya Honda Sayaka Minami Daiki Kimu Shimpei Yamaguchi Takuya Ehiro 《先进材料力学与结构力学》2020,27(18):1541-1550
Abstract The I-shaped cross-sectional beam of CFRP (CFRP I-beam) is usually manufactured by the continuous protrusion method. Carbon fibers can only be arranged in the longitudinal direction. The CFRP I-beam with arbitrary arrangement of carbon fiber was manufactured with applying the electro-activated deposition molding method. The carbon fiber fabric was immersed in the deposition solution and energized, epoxy resin precipitated around carbon fiber and impregnated. The resin-impregnated fabric was installed to the mold, and the CFRP I-beam was fabricated. The CFRP I-beam was subjected to three-point bending tests, and the relationship between load-deflection was simulated by finite-element analysis. 相似文献