全文获取类型
收费全文 | 12292篇 |
免费 | 1732篇 |
国内免费 | 468篇 |
专业分类
电工技术 | 406篇 |
综合类 | 760篇 |
化学工业 | 3196篇 |
金属工艺 | 1860篇 |
机械仪表 | 341篇 |
建筑科学 | 348篇 |
矿业工程 | 1558篇 |
能源动力 | 136篇 |
轻工业 | 420篇 |
水利工程 | 36篇 |
石油天然气 | 229篇 |
武器工业 | 85篇 |
无线电 | 717篇 |
一般工业技术 | 1275篇 |
冶金工业 | 2947篇 |
原子能技术 | 59篇 |
自动化技术 | 119篇 |
出版年
2024年 | 47篇 |
2023年 | 177篇 |
2022年 | 321篇 |
2021年 | 473篇 |
2020年 | 486篇 |
2019年 | 337篇 |
2018年 | 364篇 |
2017年 | 414篇 |
2016年 | 462篇 |
2015年 | 528篇 |
2014年 | 714篇 |
2013年 | 775篇 |
2012年 | 904篇 |
2011年 | 893篇 |
2010年 | 670篇 |
2009年 | 679篇 |
2008年 | 524篇 |
2007年 | 738篇 |
2006年 | 709篇 |
2005年 | 635篇 |
2004年 | 578篇 |
2003年 | 508篇 |
2002年 | 459篇 |
2001年 | 391篇 |
2000年 | 336篇 |
1999年 | 269篇 |
1998年 | 215篇 |
1997年 | 158篇 |
1996年 | 135篇 |
1995年 | 88篇 |
1994年 | 100篇 |
1993年 | 58篇 |
1992年 | 83篇 |
1991年 | 59篇 |
1990年 | 35篇 |
1989年 | 38篇 |
1988年 | 20篇 |
1987年 | 23篇 |
1986年 | 21篇 |
1985年 | 8篇 |
1984年 | 17篇 |
1983年 | 8篇 |
1982年 | 8篇 |
1981年 | 12篇 |
1980年 | 3篇 |
1977年 | 3篇 |
1975年 | 1篇 |
1974年 | 2篇 |
1973年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
131.
132.
Michael Bowker 《Topics in Catalysis》1996,3(3-4):461-468
STM has been combined with molecular beam rate measurements to gain an understanding of the oxidative dehydrogenation of methanol to produce formaldehyde, both at the macroscopic and microscopic level. From this a model of the reaction is developed where the methanol initial reacts at very few active oxygen sites located at the short sides of oxygen islands on the Cu(110) surface. Such sites are very much rarer on a surface which is saturated with 0.5 monolayers of oxygen and the reaction rate is initially very low, but shows autocatalytic behaviour, rising in time as vacancies are created in the oxygen layer. 相似文献
133.
134.
纳米银包覆铜粉体的制备及其导电性能研究 总被引:4,自引:0,他引:4
利用水合肼还原制备出粒径分布均匀的铜纳米粉,并对其表面镀银的方法进行了探索。 相似文献
135.
Three types of anode, Pb–Sb, Pb–Ca–Sn and Pb–Co3O4, for copper electrowinning were investigated. The corrosion resistance, as evaluated by cyclic voltammetric (CV) measurements was higher for Pb–Co3O4 than for Pb–Sb and Pb–Ca–Sn. During prolonged electrowinning under galvanostatic conditions, the anodic reaction on the Pb–Co3O4 anode was depolarized by 0.053 V as compared to Pb–Sb, and by 0.106 V with respect to Pb–Ca–Sn. The composition and structure of the anodic layer were determined by XPS, X-ray and SEM analyses. The surface layer on the three anodes examined was composed mainly of PbSO4, -PbO2 and -PbO2. Different structure of the surface layer was observed: loose and highly spread coral-like structure in the case of Pb–Sb; fibrous structure in the case of Pb–Ca–Sn and dense, fine-grained structure in the case of Pb–Co3O4. 相似文献
136.
Simona Caudo Gabriele Centi Chiara Genovese Siglinda Perathoner 《Topics in Catalysis》2006,40(1-4):207-219
Homogeneous (Cu2+ ions) and heterogeneous (Cu2+-pillared clay) Fenton-like catalysts have been compared in the conversion of p-coumaric acid. The performances of the two classes of catalysts are similar for an analogous amount of copper, but there are
some relevant differences in terms of (i) the presence of an induction time, (ii) the turnover frequency, (iii) the efficiency
in the use of H2O2, (iv) the initial attack of p-coumaric acid (hydroxylation on the aromatic ring or oxidative attack on the double bond of the lateral chain), and (v) the
effect of dissolved oxygen on the removal of total organic carbon (TOC). These differences were interpreted in terms of reaction
network of generation of radical oxygen species and of organics conversion. The possible formation of a surface peroxo adduct
coordinated to a copper binulcear site was also evidenced for the solid heterogeneous catalyst. 相似文献
137.
In Yang Monlin Kuo Deland J. Myers 《Journal of the American Oil Chemists' Society》2006,83(3):239-245
Chromated copper arsenate (CCA), an arsenicbased wood preservative, is toxic to human health and the environment. Although
CCA is stable in seasoned wood, there are potential dangers during CCA manufacture, lumber treatment, and waste disposal.
This research was conducted to study the effectiveness of soy products to replace toxic chromium and arsenic compounds in
wood preservative formulations. Three soy product (Arpro 2100, HM 90, and Supro 760) were used as fixative agents in preservative
solutions containing anhydrous CuSO4 and Na2B4O7·10H2O. The decay resistance of treated wood blocks was measured by a soil-block culture method. Despite the large molecular sizes
of copper-protein and copper-boron-protein complexes, southern pine sapwood was treatable with these preservative formulations.
Wood samples treated with >6 kg°m−3 CuSO4 and 7.5 kg·m−3 soy product, and subsequently leached for 3 d and exposed to the decay fungus Gloeophyllum trabeum (Fr.) Mur., sustained only 0.5% weight loss over 12 wk. Wood samples needed 40 kg·m−3 CuSO4 and 50 kg·m−3 soy protein to resist the copper-tolerant decay fungus Postia placenta (Fr.) M. Lars. & Lomb. These results suggest that soy-based wood preservatives can prevent wood products from fungal attack
and can replace CCA. 相似文献
138.
基于重金属对脲酶的抑制作用,研制了用于测定铜离子的生物传感器。该生物传感器的制备以壳聚糖为载体,将脲酶固定于pH电极表面。由于壳聚糖对Cu2+的富集,该生物传感器展现出高灵敏度。在样品溶液中加入5 mmol/L NaI,可以消除Hg2+和Ag+的干扰,从而实现Cu2+的选择性检测。在0.005~0.5μg/mL的浓度范围内,脲酶活性的抑制率与Cu2+浓度的对数呈良好的线性响应关系,其检出限为0.002μg/mL。将使用后的生物传感器浸泡于0.5 mmol/L的EDTA溶液再生5 min,被Cu2+抑制的脲酶的活性可以得到恢复。 相似文献
139.
通过采用不同品种、不同用量的炭黑及不同品种的软化剂对导电橡胶制品导电性能的影响试验,确立了防静电橡胶条的较佳生产配方。 相似文献
140.