全文获取类型
收费全文 | 64643篇 |
免费 | 7209篇 |
国内免费 | 5489篇 |
专业分类
电工技术 | 1585篇 |
技术理论 | 1篇 |
综合类 | 6522篇 |
化学工业 | 14515篇 |
金属工艺 | 6224篇 |
机械仪表 | 1853篇 |
建筑科学 | 12121篇 |
矿业工程 | 2198篇 |
能源动力 | 986篇 |
轻工业 | 6935篇 |
水利工程 | 3804篇 |
石油天然气 | 3267篇 |
武器工业 | 944篇 |
无线电 | 2518篇 |
一般工业技术 | 6934篇 |
冶金工业 | 3940篇 |
原子能技术 | 385篇 |
自动化技术 | 2609篇 |
出版年
2024年 | 144篇 |
2023年 | 846篇 |
2022年 | 1785篇 |
2021年 | 2204篇 |
2020年 | 2160篇 |
2019年 | 1892篇 |
2018年 | 1886篇 |
2017年 | 2428篇 |
2016年 | 2548篇 |
2015年 | 2731篇 |
2014年 | 3792篇 |
2013年 | 3579篇 |
2012年 | 4675篇 |
2011年 | 4983篇 |
2010年 | 3882篇 |
2009年 | 3988篇 |
2008年 | 3325篇 |
2007年 | 4633篇 |
2006年 | 4198篇 |
2005年 | 3847篇 |
2004年 | 3165篇 |
2003年 | 2675篇 |
2002年 | 2245篇 |
2001年 | 1787篇 |
2000年 | 1492篇 |
1999年 | 1294篇 |
1998年 | 1048篇 |
1997年 | 774篇 |
1996年 | 721篇 |
1995年 | 596篇 |
1994年 | 497篇 |
1993年 | 317篇 |
1992年 | 318篇 |
1991年 | 204篇 |
1990年 | 133篇 |
1989年 | 101篇 |
1988年 | 71篇 |
1987年 | 66篇 |
1986年 | 45篇 |
1985年 | 36篇 |
1984年 | 47篇 |
1983年 | 26篇 |
1982年 | 29篇 |
1981年 | 21篇 |
1980年 | 19篇 |
1979年 | 43篇 |
1971年 | 3篇 |
1959年 | 8篇 |
1957年 | 3篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
21.
Raisa Vieira Homem Divair Doneda Tarso Ledur Kist Janaína Guimarães Venzke Vanuska Lima da Silva Viviani Ruffo de Oliveira 《International Journal of Food Science & Technology》2022,57(3):1508-1516
The objective of this study was to investigate chemical, technological, and sensory quality of tef in products made exclusively with tef flour and tef flour associated with other flours. The selection of the studies and the extraction of information were carried out through research in several databases. Tef flour was used in cakes, cookies, breads, cupcakes, muffins, and extruded snacks. Bread was the most evaluated product with tef flour associated with other flours or exclusively. Most of the outcomes were with tef (5–50%) associated with other flours. Increased levels of fibers, minerals, antioxidant capacity, and flavonoids were noted according to the percentage of tef. Technological characteristics demonstrated that these products showed intermediate final quality, due to the characteristics of volume, specific volume, firmness, and luminosity. Regarding sensory quality, studies that used (5–35%) tef flour associated with other flours were well-accepted. 相似文献
22.
23.
《International Journal of Hydrogen Energy》2022,47(10):6755-6766
Mg-based hydride is a promising hydrogen storage material, but its capacity is hindered by the kinetic properties. In this study, Mg–Mg2Ni–LaHx nanocomposite is formed from the H-induced decomposition of Mg98Ni1·67La0.33 alloy. The hydrogen capacity of 7.19 wt % is reached at 325 °C under 3 MPa H2, attributed to the ultrahigh hydrogenation capacity in Stage I. The hydrogen capacity of 5.59 wt % is achieved at 175 °C under 1 MPa H2. The apparent activation energies for hydrogen absorption and desorption are calculated as 57.99 and 107.26 kJ/mol, which are owing to the modified microstructure with LaHx and Mg2Ni nanophases embedding in eutectic, and tubular nanostructure adjacent to eutectic. The LaH2.49 nanophase can catalyze H2 molecules to dissociate and H atoms to permeate due to its stronger affinity with H atoms. The interfaces of these nanophases provide preferential nucleation sites and alleviate the “blocking effect” together with tubular nanostructure by providing H atoms diffusion paths after the impingement of MgH2 colonies. Therefore, the superior hydrogenation properties are achieved because of the rapid absorption process of Stage I. The efficient synthesis of nano-catalysts and corresponding mechanisms for improving hydrogen storage properties have important reference to related researches. 相似文献
24.
《Advanced Powder Technology》2022,33(11):103627
Naringin (NAR), a major flavanone (FVA) glycoside, is a component of food mainly obtained from grapefruit. We used NAR as a food additive to improve the solubility and permeability of hydrophobic polyphenols used as supplements in the food industry. The spray-dried particles (SDPs) of NAR alone show an amorphous state with a glass transition temperature (Tg) at 93.2 °C. SDPs of hydrophobic polyphenols, such as flavone (FVO), quercetin (QCT), naringenin (NRG), and resveratrol (RVT) were prepared by adding varying amounts of NAR. All SDPs of hydrophobic polyphenols with added NAR were in an amorphous state with a single Tg, but SDPs of hydrophobic polyphenols without added NAR showed diffraction peaks derived from each crystal. The SDPs with NAR could keep an amorphous state after storage at a high humidity condition for one month, except for SDPs of RVT/NAR. SDPs with NAR enhanced the solubility of hydrophobic polyphenols, especially NRG solubility, which was enhanced more than 9 times compared to NRG crystal. The enhanced solubility resulted in the increased membrane permeability of NRG. The antioxidant effect of the hydrophobic NRG was also enhanced by the synergetic effect of NAR. The findings demonstrated that NAR could be used as a food additive to enhance the solubility and membrane permeability of hydrophobic polyphenols. 相似文献
25.
《International Journal of Hydrogen Energy》2022,47(57):24242-24253
As hydrogen refueling stations become increasingly common, it is clear that a high level of economic efficiency and safety is crucial to promoting their use. One way to reduce costs is to use a simple orifice instead of an excess flow valve, which Japanese safety regulations have identified as a safety device. However, there is concern about its effect on refueling time and on risk due to hydrogen leakage. To clarify the effect, we did a study of model-based refueling time evaluation and quantitative risk assessment for a typical refueling station. This study showed that an orifice is an effective alternative safety device. The increase in refueling time was less than 10%, based on simulations using a dynamic physical model of the station. Neither was there a significant difference in the risk between a configuration with excess flow valves and one with an orifice. 相似文献
26.
《Ceramics International》2021,47(22):31713-31723
Continuous carbon-fibre-reinforced Cs-geopolymer composite (Cf/CsGP) were prepared, and its in-situ conversion was investigated during high-temperature treatments. The effect of treatment temperature on the thermal evolution process and mechanical properties of the resulting products were systematically evaluated. The results indicated that the crystallization temperature of Cf/CsGP composite was considerably delayed because the amorphous structure of carbon fibres was not conducive as a nucleation substrate for pollucite derived from the CsGP matrix. Moreover, the integrity of the corresponding resulting products derived from the Cf/CsGP composite were damaged due to thermal shrinkage that occurred during the high-temperature treatment process. When treatment temperature was ≤1200oC, the mechanical properties of the corresponding products exhibited an upward trend, which was ascribed to the improvement of the densification degree of the resulting composite and well interface-bonding state between carbon fibres and pollucite. However, the mechanical properties of the resulting composites decreased with the treatment temperature continued increased from 1200 to 1400oC. This phenomenon was attributed to the impairment of fibre properties caused by interfacial reactions. 相似文献
27.
28.
《Ceramics International》2021,47(22):31319-31328
Manufacturing lightweight aggregate (LWA) at high temperature is an effective way to immobilize heavy metals in solid waste. This work investigated the performance and solidification mechanism of LWA prepared from copper contaminated soil. The volume expansion of LWA could reach a maximum of 28%, and its lowest density accounted of 1.5 g/cm3, which met the standard requirements. Optical microscope and micro-CT test illustrated that the addition of Cu leaded to obvious phase separation in LWA. The Cu leaching result of LWA first increased and then dropped with the temperature. The XRD test found that the main formation phase of Cu in LWA were t-CuFe2O4 and amorphous phase that they had different acid resistance ability. XPS revealed that the main cause of the agglomeration of liquid phase in LWA was the chain broken reaction between Cu and Si–O tetrahedron. SEM-EDS results showed that the distribution of Cu and Si had a strong correlation, which meant that Cu mostly formed amorphous phase. This work showed the uniqueness of Cu in the high temperature immobilization and pointed out the best immobilization target phase. 相似文献
29.
30.