全文获取类型
收费全文 | 9408篇 |
免费 | 1000篇 |
国内免费 | 427篇 |
专业分类
电工技术 | 90篇 |
综合类 | 543篇 |
化学工业 | 4734篇 |
金属工艺 | 301篇 |
机械仪表 | 175篇 |
建筑科学 | 351篇 |
矿业工程 | 341篇 |
能源动力 | 145篇 |
轻工业 | 1632篇 |
水利工程 | 103篇 |
石油天然气 | 395篇 |
武器工业 | 114篇 |
无线电 | 124篇 |
一般工业技术 | 969篇 |
冶金工业 | 667篇 |
原子能技术 | 103篇 |
自动化技术 | 48篇 |
出版年
2024年 | 37篇 |
2023年 | 141篇 |
2022年 | 315篇 |
2021年 | 446篇 |
2020年 | 304篇 |
2019年 | 255篇 |
2018年 | 232篇 |
2017年 | 322篇 |
2016年 | 325篇 |
2015年 | 359篇 |
2014年 | 477篇 |
2013年 | 591篇 |
2012年 | 644篇 |
2011年 | 614篇 |
2010年 | 428篇 |
2009年 | 457篇 |
2008年 | 390篇 |
2007年 | 509篇 |
2006年 | 554篇 |
2005年 | 514篇 |
2004年 | 437篇 |
2003年 | 367篇 |
2002年 | 342篇 |
2001年 | 292篇 |
2000年 | 248篇 |
1999年 | 228篇 |
1998年 | 170篇 |
1997年 | 115篇 |
1996年 | 96篇 |
1995年 | 89篇 |
1994年 | 75篇 |
1993年 | 83篇 |
1992年 | 74篇 |
1991年 | 52篇 |
1990年 | 46篇 |
1989年 | 36篇 |
1988年 | 24篇 |
1987年 | 36篇 |
1986年 | 24篇 |
1985年 | 19篇 |
1984年 | 15篇 |
1983年 | 15篇 |
1982年 | 14篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 2篇 |
1975年 | 4篇 |
1974年 | 1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 78 毫秒
11.
用十六级分离式混合—离心澄清萃取装置,在20-24℃,30-34℃,45-50℃等不同温度下进行了3B槽硝酸羟胺还原反萃钚的实验。结果表明,钚的收率均可达99.9%以上。在20-24℃时,有机相出口级附近几级的钚浓度较高,实验条件一旦波动,有可能造成钚的流失,且钚在萃取设备中有明显的积累。温度升高,14级反萃(停留时间约18min)时,钚的收率基本得到保证。 相似文献
12.
两步法合成双氰胺工艺 总被引:1,自引:0,他引:1
采用两步法由氰氨化钙合成双氰胺,通过正交试验,考察了水解温度、聚合温度、聚合时间对产品收率的影响,确定了最佳的工艺条件:水解温度42℃、聚合温度70℃、聚合时问150 min,此条件下,双氰胺收率可达85.73%。 相似文献
13.
A Oyane M Kasahara N Ichinose Y Yokoyama M Uchida A Ito 《武汉理工大学学报(材料科学英文版)》2005,20(B12):220-222
A synthetic polymer with a laminin-apatite composite layer on its surface would be useful as a percutaneous device. The preparation of such a composite was attempted in the present study using poly( ethylene terephthalate ) (PET) and polyethylene (PE) as the synthetic polymer. PET and PE plates and those pretreated with an oxygen plasma were alternately dipped in calcium and phosphate ion solutions, and then immersed in a metastable calcium phosphate solution supplemented with laminin ( LCP solution ). The PET and PE plates pretreated with an oxygen plasma formed a uniform and continuous layer of a laminin-apatite composite on their surfaces. In contrast, the PET and PE plates that had not been pretreated with an oxygen plasma did not form a continuous layer of a laminin-apatite composite on their surfaces. The hydrophilic functional groups on the PET and PE surfaces introduced by the plasma treatment were responsible for the successful laminin-apatite coruposite coating. 相似文献
14.
QifengShu JiayunZhang 《北京科技大学学报(英文版)》2005,12(3):221-224
Based on recently published experimental data, the Riboud model was modified for viscosity estimation of the slags containing calcium fluoride. The estimated values were in good agreement with measured data. Reasonable estimation can be achieved using the modified Riboud model for mould fluxes and ESR (eletro slag remelting) slags. Especially for ESR slags, the modified Riboud model can provide much more precise values than the original Riboud model. 相似文献
15.
Tomi Gominek Andrej Lubej Ciril Pohar 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(8):939-947
Precipitation of calcium sulfate dihydrate, gypsum, from (i) a pure sulfuric acid/lime suspension and (ii) a waste sulfuric acid/lime suspension in a continuous pilot plant in the temperature range from 40 °C to 80 °C was studied. It was observed that in the case of waste sulfuric acid with a high content of Mg2+ and Fe2+ ions, several hours after the beginning of the precipitation, partial dissolution of the product and modification of the crystals from needle‐ and plate‐like to agglomerated structures occurred. It is suggested that the secondary changes occur due to the increased concentration of Mg2+ and Fe2+ ions in the reactor. Below 60 °C, and above 70 °C plate‐like and needle‐like single crystals respectively were formed. The mean size (d50) of the crystals was found to increase with increasing temperature and decrease with the initial concentration of lime. Gypsum produced between 70 °C and 80 °C is suitable for further processing for construction plaster. In a precipitation process with pure sulfuric acid only single perfect needle‐like crystals occurred. Copyright © 2005 Society of Chemical Industry 相似文献
16.
Pure phase of sillenite structure, Bi12TiO20, was directly synthesized using stoichiometric bismuth (III) nitrate pentahydrate and titanium glycolate by co-precipitation. The influence of pH on the structure of Bi12TiO20 was studied in the pH range of 3–10. The sillenite structure was characterized using XRD and FTIR. The photo-degradation reaction of 4-nitrophenol (4-NP) was used to study photocatalytic activity of Bi12TiO20 as a function of the preparation pH. The rate of decomposition was followed by UV-vis and TOC. The beginning concentration of 4-NP, 44 ppm, decreased to less than 1 ppm within 30 min for all prepared catalysts. It was found that the decomposition rate constant of Bi12TiO20 is six times higher than those of either TiO2 or Bi2O3 under the same conditions. 相似文献
17.
18.
分析了电石法PVC生产链中电石炉烟气及电厂烟气二氧化硫的排放情况,指出利用电石炉烟气中的CO合成氨、再将合成氨用于燃煤电厂烟气的"氨法"脱硫是具有较大应用潜力的循环经济产业链。 相似文献
19.
本文详细分析了解吸塔换热器结堵的原因和对环保装置正常运行的影响,并针对性地提出了防范和处理措施。 相似文献
20.
ABSTRACT Postmortem structural changes in titin and nebulin filaments were investigated by incubating isolated myofibrils in a solution containing 0.1 mM calcium ions and various concentrations of a protease inhibitor. The inhibition curves showed 2 abnormal steps with increases in the concentration of leupeptin or calpastatin domain I. While the amounts of unchanged titin and nebulin were constant in the 1st step, the 2nd occurred at higher protease inhibitor concentrations. These facts indicated that excess amounts of leupeptin and calpastatin domain I caused deterioration in titin and nebulin properties, thus interfering with the binding of calcium ions. We concluded that the severance of titin and nebulin filaments in the 1st step were induced by calcium ions at 0.1 mM. 相似文献