首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   105551篇
  免费   11137篇
  国内免费   6081篇
电工技术   7950篇
技术理论   9篇
综合类   7756篇
化学工业   16224篇
金属工艺   6022篇
机械仪表   7070篇
建筑科学   7918篇
矿业工程   3502篇
能源动力   3293篇
轻工业   7602篇
水利工程   2271篇
石油天然气   5734篇
武器工业   1233篇
无线电   13139篇
一般工业技术   11880篇
冶金工业   4505篇
原子能技术   1555篇
自动化技术   15106篇
  2024年   570篇
  2023年   1879篇
  2022年   3573篇
  2021年   5054篇
  2020年   3693篇
  2019年   2948篇
  2018年   3312篇
  2017年   3790篇
  2016年   3457篇
  2015年   4791篇
  2014年   6066篇
  2013年   7198篇
  2012年   8117篇
  2011年   8441篇
  2010年   7399篇
  2009年   7066篇
  2008年   6753篇
  2007年   6422篇
  2006年   5959篇
  2005年   4853篇
  2004年   3432篇
  2003年   2692篇
  2002年   2629篇
  2001年   2187篇
  2000年   1932篇
  1999年   1693篇
  1998年   1338篇
  1997年   1086篇
  1996年   1002篇
  1995年   798篇
  1994年   639篇
  1993年   417篇
  1992年   351篇
  1991年   256篇
  1990年   219篇
  1989年   173篇
  1988年   134篇
  1987年   70篇
  1986年   71篇
  1985年   46篇
  1984年   42篇
  1983年   29篇
  1982年   33篇
  1981年   23篇
  1980年   23篇
  1979年   18篇
  1978年   9篇
  1977年   11篇
  1976年   25篇
  1959年   10篇
排序方式: 共有10000条查询结果,搜索用时 276 毫秒
51.
Microwave lignite drying with assistance of biomass-derived char was addressed and effect of bio-char on drying rate and energy consumption was investigated in this work. Effective diffusion coefficient and activation energy for the drying process were also analyzed. The results indicated the drying process was largely dependent on the variation of sample temperature. Bio-char originated from pine wood was most favorable for lignite drying, considering its better promoting effect and advanced security. There existed an optimal bio-char addition ratio for drying process at different power. The corresponding optimal ratio was 10% at 231?W and 15% at 385?W, at which the biggest drying rate and the least energy consumption were reached. It was compared lignite drying initiated at 385?W was better for energy conservation. Effective diffusivity was improved and activation energy was simultaneously reduced, with the addition of bio-char. The minimum activation energy was 15.54?W?·?g?1, which was gained at bio-char addition ratio of 10%. The results revealed the effect of bio-char on depressing activation energy could rival that of metal-based additives. The drying process with assistance of microwave and bio-char could present technical and economical benefits on lignite upgrading.  相似文献   
52.
53.
Journal of Mechanical Science and Technology - Real-time monitoring and rapid evaluation of bearing operating conditions, especially for the reliability evaluation and remaining useful life (RUL)...  相似文献   
54.
ABSTRACT

Improving the hydration resistance of CaO particle in manufacturing and application of free CaO-containing materials has practical significance. In this study, CaO granules was made from Ca(OH)2 particles, which were fabricated by the granulation method. The results showed that the hydration resistance of the CaO granules which was prepared under 1700?r?min?1 was the best, the CaO granules was sintered well in calcination process, the shell of CaO granules was relatively dense, which improves the hydration resistance of CaO granules, and the rate of hydration weight increment was 0.58% after placed in the air for 20 days under a temperature of 10–14°C and a relative humidity of 57–81%.  相似文献   
55.
56.
57.
58.
Background: Epilepsy is a chronic neurological disorder characterized by the recurrence of seizures. One-third of patients with epilepsy may not respond to antiseizure drugs. Purpose: We aimed to examine whether D-limonene, a cyclic monoterpene, exhibited any antiseizure activity in the pentylenetetrazole (PTZ)-induced kindling mouse model and in vitro. Methods: PTZ kindling mouse model was established by administering PTZ (30 mg/kg) intraperitoneally to mice once every 48 h. We performed immunoblot blots, immunohistochemistry (IHC), and high-performance liquid chromatography (HPLC) analysis after the behavioral study. Results: An acute injection of PTZ (60 mg/kg) induced seizure in mice, while pretreatment with D-limonene inhibited PTZ-induced seizure. Repeated administration of PTZ (30 mg/kg) increased the seizure score gradually in mice, which was reduced in D-limonene (10 mg/kg)-pretreated group. In addition, D-limonene treatment increased glutamate decarboxylase-67 (GAD-67) expression in the hippocampus. Axonal sprouting of hippocampal neurons after kindling was inhibited by D-limonene pretreatment. Moreover, D-limonene reduced the expression levels of Neuronal PAS Domain Protein 4 (Npas4)-induced by PTZ. Furthermore, the adenosine A2A antagonist SCH58261 and ZM241385 inhibited anticonvulsant activity and gamma-aminobutyric acid (GABA)ergic neurotransmission-induced by D-limonene. Conclusion: These results suggest that D-limonene exhibits anticonvulsant activity through modulation of adenosine A2A receptors on GABAergic neuronal function.  相似文献   
59.
60.
针对反射面成型的复杂影响因素,提出平面桁架构建的定日镜面形支撑结构优化技术路线. 利用模拟仿真、数值计算和优化算法等方法,解析20 m2定日镜面形定义技术路线的4个组成环节:面形规格及宽高比、上弦杆的截面矩、平面桁架组间距的最优值、机加工中工艺控制要点的量化. 试制小型定日镜进行实验,分析光斑形状和能流密度分布特性,并与理想球面形光斑比较,两者的拟合优度大于0.98. 实验结果表明,当反射镜宽高比取1.2,上弦杆截面矩取40 000 mm4,桁架组间距取950 mm,上弦杆和斜杆的开孔公差小于0.9 mm时,反射面形的质量提升. 研究从原理和实践上证明了该优化技术路线的可行性.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号