全文获取类型
收费全文 | 4870篇 |
免费 | 177篇 |
国内免费 | 21篇 |
专业分类
电工技术 | 304篇 |
综合类 | 15篇 |
化学工业 | 1588篇 |
金属工艺 | 129篇 |
机械仪表 | 139篇 |
建筑科学 | 125篇 |
矿业工程 | 5篇 |
能源动力 | 232篇 |
轻工业 | 407篇 |
水利工程 | 18篇 |
石油天然气 | 6篇 |
无线电 | 330篇 |
一般工业技术 | 998篇 |
冶金工业 | 201篇 |
原子能技术 | 152篇 |
自动化技术 | 419篇 |
出版年
2023年 | 33篇 |
2022年 | 51篇 |
2021年 | 129篇 |
2020年 | 60篇 |
2019年 | 76篇 |
2018年 | 89篇 |
2017年 | 68篇 |
2016年 | 114篇 |
2015年 | 87篇 |
2014年 | 134篇 |
2013年 | 261篇 |
2012年 | 261篇 |
2011年 | 302篇 |
2010年 | 253篇 |
2009年 | 273篇 |
2008年 | 300篇 |
2007年 | 236篇 |
2006年 | 223篇 |
2005年 | 157篇 |
2004年 | 162篇 |
2003年 | 182篇 |
2002年 | 171篇 |
2001年 | 87篇 |
2000年 | 101篇 |
1999年 | 77篇 |
1998年 | 115篇 |
1997年 | 88篇 |
1996年 | 82篇 |
1995年 | 69篇 |
1994年 | 65篇 |
1993年 | 69篇 |
1992年 | 60篇 |
1991年 | 62篇 |
1990年 | 37篇 |
1989年 | 57篇 |
1988年 | 20篇 |
1987年 | 39篇 |
1986年 | 34篇 |
1985年 | 47篇 |
1984年 | 35篇 |
1983年 | 46篇 |
1982年 | 42篇 |
1981年 | 38篇 |
1980年 | 25篇 |
1979年 | 29篇 |
1978年 | 30篇 |
1977年 | 22篇 |
1976年 | 15篇 |
1975年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有5068条查询结果,搜索用时 15 毫秒
31.
In the case of the wet coal charging process in coke oven chamber, it is known that the coking process is uneven and a local carbonization delay occurs. The reason was investigated through a laboratory-scale experiment and a quantitative estimation. A partial carbonization test in a test coke oven replicated the uneven plastic layer and local carbonization delay. It was revealed that most of the gas generated in the uncarbonized coal layer results from the evaporation of condensed water and that steam can break through the plastic layer in a test coke oven. Moreover, the order estimation implied that steam that generates in the uncarbonized coal layer and breaks through the plastic layer has sufficient heat capacity to cool the heating wall and delay the carbonization. It was also shown that the steam pressure peak measured in a commercial coke oven is much lower than the estimated steam pressure in this study assuming steam not breaking through the plastic layer. The above-mentioned results and quantitative investigation strongly support the ‘steam breaking through the plastic layer’ theory proposed by Dr. Rohde that an uneven carbonization process is caused by vaporized coal moisture breaking through the plastic layer at definite, unforeseeable points, which results in cooling of the wall by the steam flow. 相似文献
32.
Namsin Park Takeyuki Shiraishi Kazuyoshi Kamisugi Yoshitaka Hara Keita Iizuka Takashi Kado Shuzi Hayase 《Journal of Applied Electrochemistry》2008,38(3):371-375
A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (Voc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations. 相似文献
33.
中国政府率先开始了手机充电器的标准化,其目的是让用户更换手机终端后可继续使用原来的充电器,从而通过削减废弃物达到保护环境的目的。 相似文献
34.
Yasuro Ikuma Takashi Shigemura Takashi Hirose 《Journal of the American Ceramic Society》1996,79(10):2533-2538
Anatase-TiO2 cylindrical pellets were microwave sintered and partially transformed to rutile-TiO2 .The rutile concentration profile was determined as a function of location within the pellet. The rutile distribution in the microwavesintered pellets was different from that in pellets sintered by conventional fast firing. Temperature profiles within the pellets were estimated using the irreversible nature of the anatase-rutile transformation. The estimated temperature profile within each pellet was not uniform. In the axial direction, maximum temperature occurred in the middle of the pellet. In the radial direction, maximum temperature occurred at 1 mm below the surface of the cylinder wall. Analysis of the temperature profile indicated that, although heat flow occurred in the microwave-sintered pellet, the temperature profile did not change during a microwave exposure of 5–90 min. 相似文献
35.
A side-chain liquid-crystalline polymer (LCP) was synthesized by the addition of the mesogenic monomer to poly(methyl siloxane) in presence of a Pt-catalyst. When an aqueous solution of 10wt% ethanol was permeated through a LCP membrane by pervaporation at various temperatures, the permeation rate increased with increasing temperature and drastically changed at glass-nematic (Tg) and nematic-isotropic (TNI) transition temperatures of the LCP membrane. The LCP membrane exhibited the waterpermselectivity in the glassy and liquid-crystalline states. The ethanol concentration in the permeate increased with increasing permeation temperature and the LCP membrane changed from the waterpermselectivity to the ethanol-permselectivity around TNI. These results suggested that the permselectivity was influenced by the change of the LCP membrane structure, that is, its state transformation. It was found that a balance of the orientation of mesogenic groups and flexibility of siloxane chains is very important for the permeability and selectivity. 相似文献
36.
37.
38.
Temperature dependences of the soft phonon frequency and the damping constant in Tris-Sarcosine Calcium Chloride (TSCC) single crystal have been investigated between 5K and 100K by using a Fourier-transform far-infrared spectrometer. It has been observed that the soft phonon frequency decreases gradually and the damping constant increases as the transition temperature is approached from below The damping constant varies from 7cm-1 a 90K to less than 0.5cm-1 at 5K. It has been found that the damping constant is approximately proportional to temperature below about 60K. 相似文献
39.
Shionyu-Mitsuyama Clara; Shirai Tsuyoshi; Ishida Hirokazu; Yamane Takashi 《Protein engineering, design & selection : PEDS》2003,16(7):467-478
A computer program system was developed to predict carbohydrate-bindingsites on three-dimensional (3D) protein structures. The programssearch for binding sites by referring to the empirical rulesderived from the known 3D structures of carbohydrateproteincomplexes. A total of 80 non-redundant carbohydrateproteincomplex structures were selected from the Protein Data Bankfor the empirical rule construction. The performance of theprediction system was tested on 50 known complex structuresto determine whether the system could detect the known bindingsites. The known monosaccharide-binding sites were detectedamong the best three predictions in 59% of the cases, whichcovered 69% of the polysaccharide-binding sites in the targetproteins, when the performance was evaluated by the overlapbetween residue patches of predicted and known binding sites. Received April 24, 2003; revised June 2, 2003; accepted June 10, 2003. 相似文献
40.
The effects of vitamin B6 (B6) deficiency on cytokine levels and proportions of lymphocyte subsets in BALB/c mice were investigated. The proportion of lymphocytes from the thymus and spleen of mice given no B6, that were CD4+ CD8- T cells, was larger than in mice given B6, and the ratio of CD8+ to CD4+ T cells in the thymus of mice given no B6 was lower. The concentrations of interleukin-5 and -10 in spleen cells stimulated in vitro with concanavalin A were significantly higher in the mice with B6 deficiency, as was their plasma corticosterone concentrations. These results suggested that B6 is necessary to maintain cytokine levels and lymphoid function in the thymus and spleen of mice. 相似文献