全文获取类型
收费全文 | 2299篇 |
免费 | 122篇 |
国内免费 | 71篇 |
专业分类
电工技术 | 162篇 |
综合类 | 506篇 |
化学工业 | 226篇 |
金属工艺 | 22篇 |
机械仪表 | 41篇 |
建筑科学 | 175篇 |
矿业工程 | 98篇 |
能源动力 | 129篇 |
轻工业 | 328篇 |
水利工程 | 60篇 |
石油天然气 | 107篇 |
武器工业 | 4篇 |
无线电 | 140篇 |
一般工业技术 | 149篇 |
冶金工业 | 125篇 |
原子能技术 | 3篇 |
自动化技术 | 217篇 |
出版年
2024年 | 4篇 |
2023年 | 23篇 |
2022年 | 45篇 |
2021年 | 38篇 |
2020年 | 63篇 |
2019年 | 49篇 |
2018年 | 39篇 |
2017年 | 32篇 |
2016年 | 72篇 |
2015年 | 57篇 |
2014年 | 120篇 |
2013年 | 146篇 |
2012年 | 127篇 |
2011年 | 172篇 |
2010年 | 145篇 |
2009年 | 145篇 |
2008年 | 114篇 |
2007年 | 151篇 |
2006年 | 153篇 |
2005年 | 160篇 |
2004年 | 156篇 |
2003年 | 96篇 |
2002年 | 100篇 |
2001年 | 77篇 |
2000年 | 58篇 |
1999年 | 37篇 |
1998年 | 21篇 |
1997年 | 13篇 |
1996年 | 20篇 |
1995年 | 15篇 |
1994年 | 14篇 |
1993年 | 4篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 2篇 |
1989年 | 5篇 |
1988年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
1984年 | 1篇 |
1981年 | 4篇 |
1979年 | 1篇 |
1973年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有2492条查询结果,搜索用时 0 毫秒
11.
对工业硅生产贸易的目前形势作了较详细分析,并对今后的发展提出了建立行业协会、完善和提高6.3M级工业硅炉,有条件地建设大容量工业硅炉,重视和扩大炭素电极和还原剂煤的应用,提高产品质量扩大产品种,大力开拓市场搞好多方面联合等看法和建议。 相似文献
12.
近2年我国锆铪及锆化学制品雕生产、贸易及研发概况 总被引:1,自引:0,他引:1
介绍了我国近2年来海绵锆、锆铪制品和锆化学品的生产、进出口概况,以及重要研发进展。我国工业级海绵锆产量从2003年的100t增加到2005年的174t,2005年的销售量达到150t;锆粉与锆-铝消气剂等年产量在10t左右;锆材和锆设备年产量在100t以上;锆化学制品品种有10余种,年产量已达到20×104t。锆砂的沸腾氯化工艺、锆铪的MIBK法分离工艺、以电熔ZrO2为原料制取粗ZrCl2工艺和Al-Y复合ZrO2粉的生产工艺等的研发工作,都取得了突破性进展。 相似文献
14.
Yo Jin Kim 《Electrochimica acta》2004,49(19):3227-3234
Palladinized Nafion™ was prepared via ion-exchange and chemical reduction method. Palladium precursors and solvent systems determined the efficiency of the incorporation and distribution of nanoparticles. The tortuous thin Pd film was formed on the surface of membrane when Na+-Nafion™ and water were used. Pd nanoparticles enhanced the water uptake of Nafion™ and reduced its methanol uptake. And dispersed Pd nanoparticles in Nafion™ disturbed the proton conduction and methanol permeation simultaneously in Nafion™ cluster. In order to reduce methanol permeation of Nafion™ and keep its high conductivity, it was more efficient for Pd nanoparticles to distribute near the surface of membrane. Palladinized Nafion™ improved the performance of DMFC single cell operation by reducing the methanol permeation. 相似文献
15.
Optimization of decision rules for hydroelectric operation to reduce both eel mortality and unnecessary turbine shutdown: A search for a win–win solution 下载免费PDF全文
Worldwide populations of freshwater eels have declined with one of the contributing causes related to mortality during passage through hydropower turbines. An inherent trade‐off underlies turbine management where the competing demand for more hydropower comes at the expense of eel survival. A win–win solution exists when an option performs better on all competing demands compared to other options. A predictive model for eel migration based on a recent telemetry study was used to develop decision rules for turbine management in the Shenandoah River system. The performance of alternative decision rules was compared to the status quo policy to search for win–win solutions. Decision rules were defined by the probability of eel movement and were evaluated by the probabilities of false positive and false negative errors. The exact value of the cut‐off probability used in the decision rule will need to be determined through negotiation between stakeholders, but a range of cut‐off probabilities resulted in a win–win situation with both reduced eel mortality and increased turbine operation relative to the current shutdown strategy. Monitoring the implementation is needed to evaluate and update the predictive model and to refine the decision rule. Although the decision is framed for the Shenandoah River system, the analytical approach could be used to develop decision rules for turbine shutdown policy in other areas. 相似文献
16.
为了适应我国“入关”后国内外市场的形势,对化学矿山行业磷、硫、钾矿的国内外有关资料进行了分析研究。认为我国的磷矿和硫铁矿在国际市场上有相当的竞争力,而出口方向应是我国的周边国家和地区,钾矿将长期依靠进口。 相似文献
17.
18.
提出油价临界点概念,解决如何在波动油价下,选择具有一定规模的石油项目.通过油价临界点的应用,石油公司能够准确判断石油项目的投资机会,科学调整石油项目的经营规模,合理把握国际油价波动的影响,为提高项目抗风险能力提供科学依据. 相似文献
19.
The main purpose of this paper is to investigate the optimal replenishment lot size of supplier and optimal production rate of manufacturer under three levels of trade credit policy for supplier–manufacturer–retailer supply chain. The supplier provides a fixed credit period to settle the accounts to the manufacturer, while the manufacturer gives a fixed credit period to settle the account to the retailer and the retailer, in turn, also offers a credit period to each of its customers to settle the accounts. We assume that the supplier supplies the raw material to the manufacturer and sends back the defective raw materials to the outside supplier after completion of inspection at one lot with a sales price. The system always produces good items in the model. Also, we consider the idle times of supplier and manufacturer. Finally, numerical examples are provided to illustrate the behaviour and application of the model with graphical simulation. 相似文献
20.
杨雅娜 《杭州电子科技大学学报》2010,30(6):93-96
近几年我国的IT企业发展迅速。该文基于战略资源整合理论,从动态的角度对IT企业对外投资的区位选择进行分析。将企业对外投资的区位选择与企业自身所具有的战略资源、投资动机结合起来分析,建立区位优势评价模型,通过主客观赋权法得出区位优势评价模型中各指标折权重,并以中兴通讯有限公司为例进行实证分析,根据分析得出结论并对我国IT企业对外投资的区位选择提出建议。 相似文献