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   80307篇
  免费   7037篇
  国内免费   3773篇
电工技术   4739篇
技术理论   10篇
综合类   5691篇
化学工业   13041篇
金属工艺   4394篇
机械仪表   4708篇
建筑科学   6276篇
矿业工程   2162篇
能源动力   2319篇
轻工业   6007篇
水利工程   1537篇
石油天然气   4179篇
武器工业   719篇
无线电   9796篇
一般工业技术   9638篇
冶金工业   3753篇
原子能技术   821篇
自动化技术   11327篇
  2024年   261篇
  2023年   1256篇
  2022年   2193篇
  2021年   3208篇
  2020年   2507篇
  2019年   2060篇
  2018年   2319篇
  2017年   2427篇
  2016年   2357篇
  2015年   3117篇
  2014年   3892篇
  2013年   4582篇
  2012年   5083篇
  2011年   5524篇
  2010年   4730篇
  2009年   4504篇
  2008年   4507篇
  2007年   4220篇
  2006年   4018篇
  2005年   3447篇
  2004年   2727篇
  2003年   2638篇
  2002年   2735篇
  2001年   2328篇
  2000年   2058篇
  1999年   2220篇
  1998年   1796篇
  1997年   1489篇
  1996年   1443篇
  1995年   1196篇
  1994年   1035篇
  1993年   728篇
  1992年   560篇
  1991年   410篇
  1990年   351篇
  1989年   304篇
  1988年   221篇
  1987年   149篇
  1986年   110篇
  1985年   79篇
  1984年   57篇
  1983年   43篇
  1982年   51篇
  1981年   34篇
  1980年   34篇
  1979年   17篇
  1977年   9篇
  1976年   13篇
  1974年   11篇
  1973年   10篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Mangiferin (MGF) is a phenolic compound isolated from mango, but its poor solubility significantly limits its use. In this study, MGF was embedded into the inner aqueous phase of W1/O/W2 emulsions. Firstly, the dissolution method of MGF was determined. MGF remained stable in solution with pH 13 at 30 min, and its solubility reached 10 mg mL−1. When the pH of MGF solutions was adjusted from pH 13 to pH 6, MGF did not immediately crystallise, providing sufficient time to construct the MGF-loaded W1/O/W2 emulsions. Subsequently, the MGF-loaded W1/O/W2 emulsions were constructed using polyglycerol polyricinoleate (PGPR) and calcium caseinate (CAS). The formation and stability of the W1/O/W2 emulsions were investigated. The MGF-loaded W1/O/W2 emulsions stabilised with 1% PGPR and 1% – 3% CAS exhibited a low viscosity, limited loading capacity, and poor stability. Conversely, the MGF-loaded W1/O/W2 emulsions stabilised by 3%PGPR–3%CAS exhibited optimal loading capacity (encapsulation efficiency = 95.31% and loading efficiency = 0.91%) and stability, which was attributed to the fact that high viscosity and gel state retarded the migration of inner aqueous phase. These results indicated that the W1/O/W2 emulsions stabilised by PGPR and CAS may be a potential alternative for encapsulating mangiferin.  相似文献   
2.
Indium Tin Oxide (ITO) films were prepared, at room temperature, on a fluorphlogopite substrate using magnetron sputtering technology. At various temperatures of 500 °C, 600 °C, 700 °C, 800 °C, and 900 °C, the samples were (had) annealed for 2 h (a 2-h duration). The results showed improvement in the crystalline performance of ITO film at selected annealing temperatures, with a significant reduction in resistivity at 800 °C. The lowest resistivity is 4.08 × 10?4 Ω-cm, which is nearly an order of magnitude lower than the unannealed sample. All samples have an average light transmittance above 85% in the visible light range (400–800 nm), and with increasing annealing temperature, the average light transmittance tends to decrease. Besides, at the sensitive wavelength of 550 nm, the light transmittance is as high as 93.74%. The sheet resistance testing of the sample was through the number of bending times, which revealed that with the increase of the number of bending, the sheet resistance increases. However, after 1200 bending times, the change rate of the sheet resistance remains below 5%. Thus, the ITO film prepared on the flexible fluorphlogopite substrate revealed excellent optical and electrical properties, good flexibility, and improved stability after high-temperature annealing, which guarantees successful application in flexible electronic devices.  相似文献   
3.
KH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability.  相似文献   
4.
To enhance the tribological performance of Si3N4/TiC ceramics, MoS2/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS2/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS2/PTFE composite coatings on the friction performance of ceramics were discussed.  相似文献   
5.
6.
International Journal of Control, Automation and Systems - The vibration control problem of offshore jacket platforms is studied. The model of offshore platforms with nonlinear interactions of the...  相似文献   
7.
8.
9.
单片机原理与应用作为电子技术类学科中的必修课程具有很强实践性,要求学生掌握实际应用能力,为此研制了基于单片机系统通信为基础的实验板,依据单片机应用系统特点,可完成SPI、I^2C、UART串行通信以及并行总线方式通信。实验板有利于学生更好地了解和掌握单片机应用系统设计的方法,有利于学生进行自主设计和内容拓展。做到培养学生的学习能力、提高学生的学习兴趣、发挥学生的创造性。  相似文献   
10.
基于物联网的智慧林业可持续发展策略研究   总被引:1,自引:0,他引:1  
随着我国科技的不断进步,在“互联网+”大数据的背景下,林业的智慧化发展是必经之路。虽然我国智慧林业的发展已经取得了一定的突破,但是仍然存在着许多问题。基于此,文章在物联网技术的基础上,对智慧林业的可持续发展策略进行探讨。  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