全文获取类型
收费全文 | 5997篇 |
免费 | 615篇 |
国内免费 | 292篇 |
专业分类
电工技术 | 220篇 |
综合类 | 304篇 |
化学工业 | 2120篇 |
金属工艺 | 1159篇 |
机械仪表 | 150篇 |
建筑科学 | 38篇 |
矿业工程 | 342篇 |
能源动力 | 174篇 |
轻工业 | 70篇 |
水利工程 | 4篇 |
石油天然气 | 331篇 |
武器工业 | 32篇 |
无线电 | 283篇 |
一般工业技术 | 821篇 |
冶金工业 | 777篇 |
原子能技术 | 52篇 |
自动化技术 | 27篇 |
出版年
2024年 | 15篇 |
2023年 | 87篇 |
2022年 | 127篇 |
2021年 | 159篇 |
2020年 | 184篇 |
2019年 | 150篇 |
2018年 | 179篇 |
2017年 | 223篇 |
2016年 | 206篇 |
2015年 | 214篇 |
2014年 | 248篇 |
2013年 | 363篇 |
2012年 | 387篇 |
2011年 | 409篇 |
2010年 | 301篇 |
2009年 | 316篇 |
2008年 | 272篇 |
2007年 | 388篇 |
2006年 | 375篇 |
2005年 | 321篇 |
2004年 | 273篇 |
2003年 | 234篇 |
2002年 | 230篇 |
2001年 | 208篇 |
2000年 | 171篇 |
1999年 | 174篇 |
1998年 | 124篇 |
1997年 | 94篇 |
1996年 | 76篇 |
1995年 | 76篇 |
1994年 | 60篇 |
1993年 | 50篇 |
1992年 | 43篇 |
1991年 | 36篇 |
1990年 | 28篇 |
1989年 | 23篇 |
1988年 | 9篇 |
1987年 | 6篇 |
1986年 | 10篇 |
1985年 | 10篇 |
1984年 | 9篇 |
1983年 | 8篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 3篇 |
1975年 | 4篇 |
1951年 | 1篇 |
排序方式: 共有6904条查询结果,搜索用时 31 毫秒
11.
Weihong Xu Wei You Yaxiu Liu Bingzhe Bai Hongsheng Fang 《北京科技大学学报(英文版)》2005,12(5):410-415
The quantitative effect of Ni content on continuous cooling transformation (CCT) diagrams of novel air-cooled bainite steels was analyzed using artificial neural network models. The results showed that Ni may retard the high- and medium-temperature transformation and martensite transformation. The results conform to the materials science theories. 相似文献
12.
场激活加压燃烧合成WC-Ni复合材料的工艺参数研究 总被引:1,自引:0,他引:1
以钨、碳和镍为原料,在电场激活下,材料的燃烧合成和致密化同时进行,短时间内完成了碳化钨镍复合材料的制备。研究了场激活 加压燃烧合成中的工艺参数,如脉冲电流、能量控制模式、升温速率、最高温度和压力对反应的影响。测量了在反应合成和致密化前后的样品 收缩率。所制备的复合材料的相对密度,490N载荷下Vickers硬度和断裂韧性分别为99.2%,13.965GPa和5.9MP·m1/2。 相似文献
13.
14.
国产活性炭在合成气净化中的应用 总被引:1,自引:0,他引:1
选择国产K01活性炭脱除羰基铁、镍,以达到保护铑催化剂并减少副产物的目的。1年的实际应用结果表明:国产K01活性炭能够替代进口活性炭在合成气净化中应用。 相似文献
15.
Kazi Md. Shorowordi Md. Mohar Ali Bepari 《Journal of Materials Engineering and Performance》2002,11(6):625-630
Carbon (0.13%) steel samples containing about 0.48% molybdenum (Mo) singly and in combination with nickel (Ni) were carburized in a natural Titas gas atmosphere at a temperature of 1223 K (950 °C) and at a pressure of about 0.10 MPa (15 psia) for time periods ranging from 1–4 h followed by slow cooling in the furnace. Their microstructure was studied by optical microscopy. The austenite grain size of the case and the case depths were determined. It was found that Mo and Ni alone and in combination decrease the thickness of the cementite network near the surface of the carburized case of the steels. However, Ni is found to be more effective than Mo in decreasing the thickness of cementite network. Both Mo and Ni enhance the formation of Widmanstätten cementite plates at the grain boundary and within the grains near the surface of the carburized steels. However, Ni alone is more effective than Mo in the formation of Widmanstätten cementite plates. In the presence of Ni, Mo is much more effective in the formation of Widmanstätten cementite plates than Mo in absence of Ni. It was also revealed that both Mo and Ni increased the case depth. Ni is more effective than Mo in increasing the case depth. The combined effect of Mo and Ni is much greater than that of either Mo or Ni alone in increasing case depth. Mo as Mo carbide (Mo2C) particles refined the austenite grain size of the carburized case. Ni in solution was not found to have any effect in restricting grain growth of austenite, but the presence of Ni enhances the austenite grain size refining effect of Mo in the carburized case. 相似文献
16.
Modified (α‐diimine)nickel(II) catalysts are suitable for ethylene oligomerization reactions. Due to the mechanism (“chain running”), the formation of double‐bond isomers and branched olefins can be observed. The obtained oligomer mixtures show a Schulz–Flory distribution. Increasing ethylene pressure favors the selectivity of α‐olefin formation. The same effect can be observed when Lewis bases like thiophene or furane are added to the oligomerization reaction mixture. These results can be related to an interaction of the additives with the catalytic active species during the oligomerization process. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1356–1361, 2003 相似文献
17.
利用燃烧合成工艺原位合成了TiB2-Cu基复合材料,为了改善TiB2陶瓷和Cu基体的润湿性,将金属Ni作为合金化元素加入到TiB2-Cu复合材料。通过XRD,SEM,EPMA和TEM等检测手段对金属Ni的添加对TiB2-Cu基复合材料微观组织的影响进行了研究。结果表明,含Ni复合材料的金属粘结相的面间距比不含Ni时Cu的面间距均有不同程度的减小;Ni加入后,TiB2-Cu-Ni复合材料的组织较TiB2-Cu复合材料更加致密,但陶瓷颗粒尺寸却大于TiB2-Cu复合材料的颗粒尺寸;Ni的加入降低了复合材料的导热率和冷却速度,使得部分TiB2陶瓷颗粒有足够的时间长成棒状,同时造成TiB2陶瓷颗粒间形成更多的烧结颈;Ni的加入也改善了陶瓷与金属粘结相之间的润湿性,使陶瓷相与金属粘结相的界面结合牢固,看不到TiB2-Cu复合材料中界面脱开的现象。金属Ni的添加有利于改善TiB2-Cu基复合材料的微观组织,进而利于复合材料的致密化。 相似文献
18.
Pyrrole was successfully electropolymerized at a copper–nickel electrode in a near-neutral sodium oxalate solution containing Cu2+ cations to generate a homogenous and adherent polypyrrole film. The presence of the Cu2+ ions increased both the rate of the electropolymerization reaction and the adherence of the polymer at the CuNi interface. In the absence of these cations, oxidation of the electrode occurred generating a nickel-rich layer that was not sufficiently conducting, under the electropolymerization conditions employed, to facilitate the electron-transfer reaction and the electropolymerization of pyrrole.These films remained stable and exhibited significant corrosion protection properties in acidified and neutral 0.1 mol dm−3 NaCl solutions even on polarization of the electrodes to high anodic potentials. 相似文献
19.
20.
In this work we investigated the mechanism of the electrochemical intercalation reactions in rf sputtered nickel oxide thin films electrodes by two techniques: mechanical stress change measurements by means of an optical technique and mass changes using an electrochemical quartz microbalance (EQCM). The experiments were performed in alkaline electrolytes containing cations of the first column of the periodic table. Reversible mass and volume changes were observed. In order to explain these experimental results, an exchange reaction is proposed, in which the oxidation process is accompanied by the deinteractional of a relative large number of “light” cations, simultaneously with the intercalation of a smaller number of heaviest cations. 相似文献