全文获取类型
收费全文 | 20138篇 |
免费 | 1620篇 |
国内免费 | 826篇 |
专业分类
电工技术 | 418篇 |
综合类 | 1237篇 |
化学工业 | 4619篇 |
金属工艺 | 3153篇 |
机械仪表 | 659篇 |
建筑科学 | 1056篇 |
矿业工程 | 865篇 |
能源动力 | 212篇 |
轻工业 | 2442篇 |
水利工程 | 118篇 |
石油天然气 | 254篇 |
武器工业 | 368篇 |
无线电 | 551篇 |
一般工业技术 | 2851篇 |
冶金工业 | 3537篇 |
原子能技术 | 147篇 |
自动化技术 | 97篇 |
出版年
2024年 | 45篇 |
2023年 | 347篇 |
2022年 | 538篇 |
2021年 | 633篇 |
2020年 | 645篇 |
2019年 | 511篇 |
2018年 | 510篇 |
2017年 | 627篇 |
2016年 | 595篇 |
2015年 | 613篇 |
2014年 | 942篇 |
2013年 | 954篇 |
2012年 | 1186篇 |
2011年 | 1292篇 |
2010年 | 1013篇 |
2009年 | 990篇 |
2008年 | 852篇 |
2007年 | 1343篇 |
2006年 | 1315篇 |
2005年 | 1212篇 |
2004年 | 1057篇 |
2003年 | 918篇 |
2002年 | 791篇 |
2001年 | 682篇 |
2000年 | 594篇 |
1999年 | 465篇 |
1998年 | 409篇 |
1997年 | 323篇 |
1996年 | 262篇 |
1995年 | 214篇 |
1994年 | 212篇 |
1993年 | 149篇 |
1992年 | 107篇 |
1991年 | 54篇 |
1990年 | 44篇 |
1989年 | 54篇 |
1988年 | 18篇 |
1987年 | 14篇 |
1986年 | 8篇 |
1985年 | 9篇 |
1984年 | 3篇 |
1983年 | 3篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 2篇 |
1951年 | 2篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
101.
Two-step sintering behavior of titanium-doped Y2O3 ceramics with monodispersed sub-micrometer powder
Two-step sintering of titanium-doped Y2O3 was carried out using monodispersed sub-micrometer powder. The effect of titanium dopant concentration on the sinterability and kinetic window of constant grain-size sintering were examined. The titanium doping improves the sinterability of the Y2O3 powder, which broadens the sintering kinetic window and lowers sintering temperature. The Vickers hardness was also enhanced as the doping concentration of titanium was increased, assuming the same grain size. 相似文献
102.
Yang Wen Huey Ayu Shazwani Zulkipli Husnul Azan Tajarudin Rabeta Mohd Salleh 《Journal of Food Processing and Preservation》2021,45(10):e15831
This study was aimed to investigate the potential use of pre-treated cuttlebone powder (CBP) as an alternative calcium source by evaluating the physicochemical properties of CBP pre-treated with distilled water (CBP1), 1% acetic acid (CBP2), and 2% sodium hydroxide (NaOH) solutions (CBP3). Proximate analysis revealed ash as the major component of all samples. The presence of phenols, flavonoids, alkaloids, and glycosides were detected but tannins appeared to be absent in cuttlebones. Mineral analysis indicated that CBP was rich in calcium, which means the material may be considered as a potential calcium source for food products or calcium supplements. The bulk density of CBP2 was significantly lower (p < .05) than those of CBP1 and CBP3, and the water holding capacity (WHC) of CBP1 was significantly higher (p < .05) than those of CBP2 and CBP3. The high bulk density, water and oil holding capacities of CBP demonstrated its potential use as a functional food ingredient. 相似文献
103.
《International Journal of Hydrogen Energy》2021,46(80):40014-40021
Perovskite La0.6Sr0.4Co0.2Fe0.8O3+δ (LSCF) as a promising cathode material possessed overwhelming electronic conduction along with certain ionic conductivity. Its strong electron conduction capability hinder the application of pure-phase LSCF as electrolyte in semiconductor membrane fuel cell (SMFC). In order to constrain the electron transport and take advantage of the decent ion conduction of LSCF, a thin layer of γ-Al2O3 with insulating property was added as an electron barrier layer and combine with LSCF to form a two-layer structure electrolyte. Through adjusting the weight ratio of LSCF/γ-Al2O3 to optimize the thickness of double layers, an open circuit voltage of 0.98 V and a maximum power density of 690 mW/cm2 was received at 550 °C. At the same time, SEM, EIS and other characterization technology had proven that the LSCF/γ-Al2O3 bi-layer electrolyte can work efficiently at low temperature. The advantage of this work is the application of double-layer (γ-Al2O3/LSCF) structure electrolyte to instead of mixed material electrolyte in low-temperature solid oxide fuel cells. Structural innovation and the using of insulating materials provided clues for the further development of SMFC. 相似文献
104.
Jingming Ning Gary G. Hou Jingjing Sun Zhengzhu Zhang Xaiochun Wan 《International Journal of Food Science & Technology》2019,54(2):576-582
The effects of green tea powder (GTP) on the properties of hard red winter (HRW) flour and Chinese steamed bread were investigated. GTP was blended with HRW flour at levels of 0.00, 1.00, 2.00, 3.00 and 4.00 g GTP/100 g wheat flour. With the addition of GTP, the maximum torque of flour became stronger. The resilience and degree of green colour of steamed bread increased, while hardness and chewiness decreased, with the addition of GTP. The addition of 1.00% GTP did not significantly affect the specific volume, but remarkably influenced the hardness and resilience of steamed bread. In steamed bread formulated with GTP, the antioxidant activity was 0.84 mm TE per g at 1.00% of GTP and increased with GTP levels. The steamed bread had a pleasant flavour, and the degree of overall liking of steamed bread increased with GTP levels to the maximum used in this work. 相似文献
105.
《Advanced Powder Technology》2021,32(10):3447-3455
The features of changes in the morphology, structural-phase state and microhardness of 3Ni-Al powder mixture after different duration of high-energy ball-milling have been studied. Three main stages of the evolution of the structural-phase state were revealed, which, corresponding to different duration of treatment, differ in the morphology of the powder mixture, distribution of components, phase compositions and the nature of changes in microhardness. It was found that under high-energy ball-milling conditions, the synthesis of intermetallic Ni3Al and NiAl phases begins at much lower temperatures compared to the phase diagram. It is shown that an increase in the duration of high-energy ball-milling is accompanied by a transformation of the phase composition, the features of which determine the level of strengthening of the powder mixture studied. 相似文献
106.
The paper presents the results obtained for the effect of ball milling of Ti–Ni powder, which is close in composition to the equiatomic one, on electrochemical hydrogenation. It is shown that the average size of the powder particles measured by BET and laser diffraction methods is found to reduce during milling, while the average size of the powder particles measured by SEM changes to attain its minimum within 30-s milling due to destruction and subsequent aggregation of particles. The powder in its initial state consists of a mixture of TiNi (austenite, martensite), Ti2Ni, and TiNi3 phases, and after ball milling, an X-ray amorphous phase is formed. The CDD size of the TiNi phase (austenite) reduces from 25 to 4 nm. It is found that the lattice parameters of the TiNi (austenite) and Ni3Ti phases do not change during electrochemical hydrogenation, whereas the crystal lattice parameter of the Ti2Ni phase increases, which indicates the predominant interaction of hydrogen with the Ti2Ni phase. The lattice parameter of the Ti2Ni based phase corresponds to Ti2NiH0.5 and Ti2NiH0.8 hydrides depending on the milling time and hydrogenation time. It is found that there is an “incubation period” of hydrogenation of the Ti2Ni phase, which attains 90 min. 相似文献
107.
108.
Satoshi Nogami Katsuhiko Minoura Nao Kiminami Yui Kitaura Hiromasa Uchiyama Kazunori Kadota Yuichi Tozuka 《Advanced Powder Technology》2021,32(5):1750-1756
Although curcumin is considered to have various therapeutic effects, its use as a functional food or supplement is restricted owing to its low water solubility and bioavailability. To increase the solubility of curcumin in water, the use of polyvinylpyrrolidone (PVP) and vinylpyrrolidone-vinyl acetate copolymers with a pyrrolidone skeleton was noted to be promising. In particular, the bi-component formulations of curcumin/PVP prepared through spray drying exhibited an amorphous state in powder X-ray diffraction observations and temporally increased the apparent solubility of curcumin to over 5000 times that of untreated curcumin; nevertheless, after 24 h, the solubility decreased owing to the unstable supersaturated state of curcumin. The addition of α-cyclodextrin (α-CyD) in the bi-component curcumin/PVP formulation helped maintain the supersaturated state of curcumin, whereas the addition of β- and γ-CyD led to the collapse of the supersaturated state. The addition of α-CyD can likely help inhibit the nucleation and crystal growth of curcumin, through the interaction among the solubilized units of curcumin/PVP and α-CyD. 相似文献
109.
目前Ti6Al4V合金粉体的生产方法主要有雾化法、机械合金法和氢化脱氢法,它们都以Kroll法生产海绵钛为基础。使用钛的氧化物作为原料的熔盐电解法和金属热还原法仍处于研究阶段。本文依据变价金属Ti和V的氧化物在还原过程中逐级还原的特性,提出使用金属氧化物(TiO2, V2O5)作为原料的多级深度还原法制备Ti6Al4V合金粉体的新思路。首先计算了TiO2-V2O5-Mg-Ca体系的吉布斯自由能变,结果表明先进行镁热自蔓延反应,后进行钙热深度还原反应制备Ti6Al4V合金粉体在热力学上具备可行性。然后通过实验进行了的验证。镁热自蔓延反应产物酸浸后除去MgO可得到氧含量为15.84%的多孔Ti-Al-V-O前驱体。配入金属Ca后进行深度脱氧可得到低氧Ti6Al4V合金粉体(Al: 6.2wt.%, V: 3.64wt.%, O: 0.24wt.%, Mg: 0.01wt.%, Ca: < 0.01wt.%)。 相似文献
110.
《Ceramics International》2022,48(10):14192-14200
In this study, mold powder slurries with high solid loading and low viscosity were prepared during the ball-milling process for improving the homogeneity and mechanical properties of granules after spray-drying. The effect of ball-milling parameters, such as solid loading, binder/dispersant content, and ball-milling time, on the flowability, dispersibility, stability, and rheological behavior of mold powder slurries was systematically investigated by rheology observation and sedimentation tests. As these parameters varied, the slurry exhibited the shear-thinning behavior of a non-Newtonian fluid with a shear rate range of 0–50 s?1, which was adequately described by the Herschel-Bulkley model. The optimal parameters that optimized the flowability, dispersibility, and stability of the slurry, along with its rheological behavior, were chosen as follows: solid loading, 60 wt%; modified sodium carboxymethyl cellulose binder content, 1.0 wt%; sodium tripolyphosphate dispersant content, 0.5 wt%; ball-milling time, 60 min. 相似文献