全文获取类型
收费全文 | 185571篇 |
免费 | 15596篇 |
国内免费 | 10234篇 |
专业分类
电工技术 | 14189篇 |
技术理论 | 6篇 |
综合类 | 20875篇 |
化学工业 | 24645篇 |
金属工艺 | 7381篇 |
机械仪表 | 12077篇 |
建筑科学 | 22169篇 |
矿业工程 | 8532篇 |
能源动力 | 5517篇 |
轻工业 | 11570篇 |
水利工程 | 7564篇 |
石油天然气 | 10773篇 |
武器工业 | 2215篇 |
无线电 | 12148篇 |
一般工业技术 | 20362篇 |
冶金工业 | 7791篇 |
原子能技术 | 2419篇 |
自动化技术 | 21168篇 |
出版年
2024年 | 550篇 |
2023年 | 1740篇 |
2022年 | 3731篇 |
2021年 | 4514篇 |
2020年 | 4929篇 |
2019年 | 4024篇 |
2018年 | 3801篇 |
2017年 | 4998篇 |
2016年 | 5655篇 |
2015年 | 6011篇 |
2014年 | 11096篇 |
2013年 | 9822篇 |
2012年 | 13778篇 |
2011年 | 14079篇 |
2010年 | 11371篇 |
2009年 | 11634篇 |
2008年 | 10401篇 |
2007年 | 13338篇 |
2006年 | 12179篇 |
2005年 | 10643篇 |
2004年 | 8920篇 |
2003年 | 7905篇 |
2002年 | 6467篇 |
2001年 | 5480篇 |
2000年 | 4650篇 |
1999年 | 3858篇 |
1998年 | 3001篇 |
1997年 | 2492篇 |
1996年 | 2057篇 |
1995年 | 1842篇 |
1994年 | 1473篇 |
1993年 | 1069篇 |
1992年 | 924篇 |
1991年 | 646篇 |
1990年 | 500篇 |
1989年 | 507篇 |
1988年 | 377篇 |
1987年 | 211篇 |
1986年 | 167篇 |
1985年 | 78篇 |
1984年 | 74篇 |
1983年 | 42篇 |
1982年 | 50篇 |
1981年 | 63篇 |
1980年 | 33篇 |
1979年 | 39篇 |
1978年 | 18篇 |
1977年 | 17篇 |
1975年 | 16篇 |
1959年 | 31篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
21.
Yu-Xuan Li Ping Li Yu-Zhe Wu Zhen-Liang Xu Ming-Ling Huang 《Ceramics International》2021,47(2):2180-2186
A novel TiO2 thin film was prepared on the ceramic hollow fiber by the sol-gel method using poly(vinylpyrrolidone) (PVP) and polyvinyl alcohol (PVA) as additives. SEM images verified the formation of TiO2 layer with various thickness using different composition of titania sols. The effect of the PVP and PVA contents on the TiO2 sol properties, the separation and the antifouling performance of the ultrafiltration membranes were investigated thoroughly. When the contents of PVP and PVA were 1.0 wt% and 0.8 wt%, respectively, the resultant membrane showed a thickness of 0.55 μm with a pure water flux of 255 L m?2 h?1. In addition, the adherent foulant bovine serum albumin was applied to evaluate the antifouling performance. During the three fouling-recovery cycles, the flux recovery ratio and the flux decay ratio maintained about 99% and 30%. The BSA flux and rejection were still 169 L m?2 h?1 and 96.9% after the cycles, indicating a superior antifouling property. 相似文献
22.
《International Journal of Hydrogen Energy》2022,47(58):24592-24609
Hydrogen is gaining increased attention from industries and policymakers in China. However, most of the current demonstration projects in the country have relied on conventional energy sources, including industrial byproduct hydrogen and grey hydrogen produced from fossil fuels. Moreover, strategies and policy frameworks leading to a shift to green or low-carbon hydrogen have neither been explored in-depth nor been identified clearly in the context of China. This study aims at bridging such gaps. Roadmapping techniques enhanced by the Delphi method and SWOT analysis are used to survey hydrogen energy experts from government bodies, industries, and academia to achieve basic agreement on strategically enabling large-scale green hydrogen demonstrations followed by commercialisation in China. The outcome of two rounds of surveys showed that experts' opinions converged on a strategic roadmap with three stages of development. The corresponding policies needed in each stage are evaluated and selected to form a systemic framework. 相似文献
23.
24.
构建工程咨询机构BIM技术应用能力评价的指标体系,提出改进的熵权TOPSIS评价模型,以4个典型的工程咨询单位为例,进行BIM技术运用能力评价。研究表明,BIM行业的整体水平已经有了明显的提升,但是区域间的发展还存在一定差距。 相似文献
25.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations. 相似文献
26.
27.
28.
反应堆屏蔽计算中经常出现厚屏蔽、小探测器问题,常规蒙特卡罗方法难以有效解决。基于自动重要抽样(AIS)方法,本文提出了小探测器自动重要抽样(SDAIS)方法,并针对小探测器问题,优化了AIS方法的虚粒子赌分裂算法。该方法在自主开发的蒙特卡罗屏蔽程序MCShield上进行了实现。使用NUREG/CR-6115 PWR基准题验证该方法的正确性和计算效率。结果表明,SDAIS方法可有效地解决厚屏蔽小探测器问题,相比AIS方法及传统的重要性方法,计算效率提升1~2个量级。 相似文献
29.
不同给液方式对铜电解过程中有重要的影响,不同的循环方式会影响槽内温度分布、电解液成分及阳极泥沉降等,因此,根据铜电解生产不同情况的需要,分析对比了多种给液方式在贵冶电解车间的应用,总结了这几种给液方式的优缺点和适用条件。 相似文献
30.
A 2D computational fluid dynamics (Eulerian–Eulerian) multiphase flow model coupled with a population balance model (CFD-PBM) was implemented to investigate the fluidization structure in terms of entrance region in an industrial-scale gas phase fluidized bed reactor. The simulation results were compared with the industrial data, and good agreement was observed. Two cases including perforated distributor and complete sparger were applied to examine the flow structure through the bed. The parametric sensitivity analysis of time step, number of node, drag coefficient, and specularity coefficient was carried out. It was found that the results were more sensitive to the drag model. The results showed that the entrance configuration has significant effect on the flow structure. While the dead zones are created in both corners of the distributors, the perforated distributor generates more startup bubbles, heterogeneous flow field, and better gas–solid interaction above the entrance region due to jet formation. 相似文献