全文获取类型
收费全文 | 46823篇 |
免费 | 5084篇 |
国内免费 | 4106篇 |
专业分类
电工技术 | 2279篇 |
技术理论 | 1篇 |
综合类 | 5150篇 |
化学工业 | 7646篇 |
金属工艺 | 4820篇 |
机械仪表 | 5705篇 |
建筑科学 | 4128篇 |
矿业工程 | 2367篇 |
能源动力 | 1285篇 |
轻工业 | 2799篇 |
水利工程 | 1946篇 |
石油天然气 | 3033篇 |
武器工业 | 680篇 |
无线电 | 2085篇 |
一般工业技术 | 4709篇 |
冶金工业 | 1821篇 |
原子能技术 | 299篇 |
自动化技术 | 5260篇 |
出版年
2024年 | 211篇 |
2023年 | 1355篇 |
2022年 | 2357篇 |
2021年 | 2397篇 |
2020年 | 1942篇 |
2019年 | 1535篇 |
2018年 | 1372篇 |
2017年 | 1564篇 |
2016年 | 1691篇 |
2015年 | 1700篇 |
2014年 | 2508篇 |
2013年 | 2263篇 |
2012年 | 3069篇 |
2011年 | 3297篇 |
2010年 | 2558篇 |
2009年 | 2818篇 |
2008年 | 2379篇 |
2007年 | 3184篇 |
2006年 | 2973篇 |
2005年 | 2521篇 |
2004年 | 2007篇 |
2003年 | 1849篇 |
2002年 | 1528篇 |
2001年 | 1259篇 |
2000年 | 1076篇 |
1999年 | 875篇 |
1998年 | 724篇 |
1997年 | 565篇 |
1996年 | 483篇 |
1995年 | 422篇 |
1994年 | 386篇 |
1993年 | 245篇 |
1992年 | 192篇 |
1991年 | 178篇 |
1990年 | 124篇 |
1989年 | 99篇 |
1988年 | 83篇 |
1987年 | 38篇 |
1986年 | 30篇 |
1985年 | 32篇 |
1984年 | 23篇 |
1983年 | 18篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 21篇 |
1979年 | 8篇 |
1976年 | 3篇 |
1975年 | 4篇 |
1959年 | 4篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
991.
《Ceramics International》2017,43(17):14552-14571
Semiconductor photocatalysis is one of most appealing and attractive technologies, which has been directly utilized to harvest solar energy for energy and environmental applications. Titanium dioxide (TiO2) has been proved to be leading semiconductor photocatalyst for the degradation of pollutants. However, it suffers from low photocatalytic activity under visible light activation because of its intrinsic wide band gap. Various strategies have been developed to enhance TiO2 efficiency in the visible light region. Among them TiO2 modification with carbonaceous nanomaterials is very effective route for excellent photocatalytic activity. This critical review aims to present recent progress in the design and synthesis of carbonaceous-TiO2 photocatalysts, covering carbon doping, activated carbon, fullerenes, carbon nanotubes and graphene. Moreover, proposed mechanisms of enhancement, effect of synthesis routes, demonstrations of performance and applications reported in literature are reviewed. Ongoing challenges and possible new directions are outlined. 相似文献
992.
Yu-cheng Lei Xiao-kai Guo Hong-xia Chang Tian-qing Li Qiang Zhu Gang Chen Long-ren Xiao 《钢铁研究学报(英文版)》2017,24(9)
The cavitation erosion of weld joint and base metal of China low activation martensitic(CLAM)steel in liquid lead-bismuth eutectic alloy(LBE)at 550°C was investigated to simulate the cavitation erosion of the first wall and the nuclear main pump impeller in the accelerator driven sub-critical system(ADS).A suit of ultrasonic cavitation facility was self-designed to study the cavitation erosion.By studying the surface micro topography,roughness and mean pit depth of the tested specimens,it was found that some crater clusters and large scale cracks appeared on the tested specimen surface after the formation of numerous single craters,and the base metal exhibited much better cavitation erosion resistance than the weld bead due to the difference in their mechanical properties and microstructures.In addition,by comparing the results of static corrosion and cavitation erosion,it could be concluded that the cavitation erosion and the dissolution and oxidation corrosion in liquid LBE would accelerate mutually. 相似文献
993.
Wenhua Chen Pengju Liu Yuansen Liu Qi Wang 《Polymer-Plastics Technology and Engineering》2017,56(10):1118-1127
The system based on aluminum phosphinate (OP) and melamine polyphosphate was applied in flame-retardant glass fiber-reinforced polyamide 66. From a qualitative and quantitative point of view, the incorporation of OP played a positive role in obtaining the homodisperse of flame-retardant particles throughout the composites. A two-step cooling mode during the degradation process was established to play an effective role in absorbing heat to retard the flame spread rate and provide enough time for barrier generation. In condensed phase, the cross-linked structure formed in residue promoted the construction of the high-quality barrier layer. 相似文献
994.
995.
996.
两亲聚合物对湿法磷酸的助滤性能及机理研究 总被引:1,自引:0,他引:1
以实验室自制单体A、丙烯酰胺(AM)、二甲基二烯丙基氯化铵(DMDAAC)为原料,过硫酸盐氧化还原体系为引发剂,采用水溶液共聚法合成一种用于湿法磷酸助滤的两亲聚合物PADA-10。对所得聚合物的助滤性能进行研究,结果表明:磷酸料浆体系中加入PADA-10后,过滤速度提高了约4.3倍,滤饼水分降低了约10.8%。对PADA-10助滤机理的初步探究结果表明:PADA-10能在一定pH值范围内中和磷石膏表面电荷,使磷石膏微晶絮凝成团,添加PADA-10后滤饼的孔隙率增加;同时,PADA-10能增强磷石膏颗粒的疏水性,使磷酸滤液表面张力降低了5.2 mN/m,磷石膏表面接触角增大了3.4°。 相似文献
997.
《北京印刷学院学报》2012,20(3)
秦朝立国之后,在确立皇权至高无上的基础上,形成了威权式思想教化机制。这一教化机制的形成对于维护秦初的国家统一和社会稳定起到了一定的作用。但当秦始皇病逝之后,威权去除,思想教化机制失灵,由此导致政治思想领域的混乱和天下反叛的并起,其结果就是秦朝的覆亡。 相似文献
998.
陈烨 《湖南工业职业技术学院学报》2012,12(6):45-47
解决中小企业实现持续发展的问题,有助于充分发挥中小企业对经济的促进作用。本文基于湖南省十大重点行业的中小企业调查,从企业内部经营管理着手,探究实现中小企业持续发展管理机制。 相似文献
999.
《Ergonomics》2012,55(12):1657-1670
AbstractWork-related shoulder joint disorders contribute considerably to absenteeism in the workplace. To identify the tasks that are stressful to the shoulder joint, a strain index was formulated based on the concept of concavity compression—a shoulder stabilizing mechanism. The magnitude and direction of the shoulder joint reaction forces were used in formulating the strain index. A two phase experiment was conducted. In Phase 1, participants performed 30 different manual handling tasks. The tasks were categorized into low, medium and high strain tasks based on their strain index values. In Phase 2, out of the 30 tasks, repetitive exertions of three tasks (low, medium and high strain index values) were simulated using three external loads (0.91, 1.81 and 2.72?kg). The muscle activity data recorded from eight shoulder muscles showed that tasks with higher strain index values induced significantly greater activation and muscle fatigue than tasks with lower strain index values.Practitioner Summary: The strain index developed in this study is a conclusive estimation of the concavity compression required for shoulder joint stabilization. It can be used to identify the activities that may contribute to the risks of shoulder disorders. Abbreviation BLS Bureau of the Labor Statistics 相似文献
1000.
裂解炉的操作条件影响着裂解产物分布,究竟采取怎样的操作参数更能实现企业经济效益最大,这是企业生产经营面临的重要课题。介绍了综合利用线性规划模型和裂解机理模型优化裂解炉操作条件、实现企业经济效益最大的方法,列举了工厂实际应用案例,对石化企业生产经营具有参考意义。 相似文献