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   143838篇
  免费   15630篇
  国内免费   8826篇
电工技术   12169篇
技术理论   10篇
综合类   11880篇
化学工业   19611篇
金属工艺   8556篇
机械仪表   9580篇
建筑科学   12173篇
矿业工程   4600篇
能源动力   4289篇
轻工业   10541篇
水利工程   3563篇
石油天然气   6550篇
武器工业   1717篇
无线电   16615篇
一般工业技术   14217篇
冶金工业   9016篇
原子能技术   1855篇
自动化技术   21352篇
  2024年   726篇
  2023年   2403篇
  2022年   4983篇
  2021年   6523篇
  2020年   4994篇
  2019年   3783篇
  2018年   4402篇
  2017年   4864篇
  2016年   4446篇
  2015年   6334篇
  2014年   7966篇
  2013年   9069篇
  2012年   10581篇
  2011年   11035篇
  2010年   9944篇
  2009年   9543篇
  2008年   9518篇
  2007年   8651篇
  2006年   8284篇
  2005年   6737篇
  2004年   5042篇
  2003年   4354篇
  2002年   4911篇
  2001年   4077篇
  2000年   2796篇
  1999年   2208篇
  1998年   2390篇
  1997年   1640篇
  1996年   1434篇
  1995年   993篇
  1994年   856篇
  1993年   657篇
  1992年   392篇
  1991年   288篇
  1990年   239篇
  1989年   206篇
  1988年   169篇
  1987年   133篇
  1986年   110篇
  1985年   63篇
  1984年   29篇
  1983年   25篇
  1982年   43篇
  1981年   45篇
  1980年   53篇
  1979年   21篇
  1977年   80篇
  1976年   181篇
  1959年   25篇
  1951年   22篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
针对传统铁矿石磁化焙烧技术与装备存在焙烧产品质量差、产能低、能耗高和环境污染严重等问题,创造性提出了一种“预热-蓄热还原-再氧化”悬浮磁化焙烧新工艺。该工艺具有原料适应性广、焙烧产品质量均匀、回收率高、生产能耗低、无污染等特点,适合处理赤铁矿、褐铁矿、菱铁矿及其混合型难选铁矿石。通过多年的潜心基础研究与技术攻关,形成了非均质矿石颗粒悬浮态流动控制、蓄热式高效低温还原、铁物相精准调控与余热同步回收等一系列关键技术,建成了500kg/h复杂难选铁矿石悬浮磁化焙烧-高效分选半工业试验平台。  相似文献   
33.
34.
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings.  相似文献   
35.
Lin  Haicheng  Huang  Wantong  Zhao  Kun  Qiao  Shuang  Liu  Zheng  Wu  Jian  Chen  Xi  Ji  Shuai-Hua 《Nano Research》2020,13(1):133-137
Nano Research - The isostructural and isoelectronic transition-metal-dichalcogenides 1T-TaS2 and 1T-TaSe2 are layered materials with intricate electronic structures. Combining the molecular beam...  相似文献   
36.
37.
38.
This study aimed at investigating the possible mechanisms of hepatic protective activity of Cichorium intybus L. (chicory) in acute liver injury. Pathological observation, reactive oxygen species (ROS) detection and measurements of biochemical indexes on mouse models proved hepatic protective effect of Cichorium intybus L. Identification of active compounds in Cichorium intybus L. was executed through several methods including ultra performance liquid chromatography/time of flight mass spectrometry (UPLC-TOF-MS). Similarity ensemble approach (SEA) docking, molecular modeling, molecular docking, and molecular dynamics (MD) simulation were applied in this study to explore possible mechanisms of the hepato-protective potential of Cichorium intybus L. We then analyzed the chemical composition of Cichorium intybus L., and found their key targets. Furthermore, in vitro cytological examination and western blot were used for validating the efficacy of the selected compounds. In silico analysis and western blot together demonstrated that selected compound 10 in Cichorium intybus L. targeted Akt-1 in hepatocytes. Besides, compound 13 targeted both caspase-1 and Akt-1. These small compounds may ameliorate liver injury by acting on their targets, which are related to apoptosis or autophagy. The conclusions above may shed light on the complex molecular mechanisms of Cichorium intybus L. acting on hepatocytes and ameliorating liver injury.  相似文献   
39.
Costunolide (CE) and dehydrocostuslactone (DE) are derived from many species of medicinal plants, such as Saussurea lappa Decne and Laurus nobilis L. They have been reported for their wide spectrum of biological effects, including anti-inflammatory, anticancer, antiviral, antimicrobial, antifungal, antioxidant, antidiabetic, antiulcer, and anthelmintic activities. In recent years, they have caused extensive interest in researchers due to their potential anti-cancer activities for various types of cancer, and their anti-cancer mechanisms, including causing cell cycle arrest, inducing apoptosis and differentiation, promoting the aggregation of microtubule protein, inhibiting the activity of telomerase, inhibiting metastasis and invasion, reversing multidrug resistance, restraining angiogenesis has been studied. This review will summarize anti-cancer activities and associated molecular mechanisms of these two compounds for the purpose of promoting their research and application.  相似文献   
40.
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