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   1774830篇
  免费   61856篇
  国内免费   21683篇
电工技术   54360篇
技术理论   45篇
综合类   31037篇
化学工业   325890篇
金属工艺   82098篇
机械仪表   61208篇
建筑科学   71773篇
矿业工程   22635篇
能源动力   59950篇
轻工业   128201篇
水利工程   20838篇
石油天然气   58090篇
武器工业   2915篇
无线电   233177篇
一般工业技术   310547篇
冶金工业   143800篇
原子能技术   37154篇
自动化技术   214651篇
  2022年   14440篇
  2021年   28658篇
  2020年   22733篇
  2019年   24492篇
  2018年   25529篇
  2017年   26084篇
  2016年   32483篇
  2015年   32808篇
  2014年   47814篇
  2013年   111058篇
  2012年   57652篇
  2011年   70343篇
  2010年   63926篇
  2009年   71408篇
  2008年   63244篇
  2007年   58692篇
  2006年   63299篇
  2005年   54789篇
  2004年   51618篇
  2003年   50382篇
  2002年   49044篇
  2001年   43911篇
  2000年   42842篇
  1999年   41575篇
  1998年   39644篇
  1997年   37642篇
  1996年   35942篇
  1995年   32344篇
  1994年   29663篇
  1993年   28302篇
  1992年   26720篇
  1991年   23301篇
  1990年   23526篇
  1989年   22250篇
  1988年   20551篇
  1987年   18705篇
  1986年   17986篇
  1985年   21204篇
  1984年   21737篇
  1983年   19616篇
  1982年   18817篇
  1981年   18840篇
  1980年   17441篇
  1979年   18017篇
  1978年   17260篇
  1977年   16475篇
  1976年   16540篇
  1975年   15592篇
  1974年   15142篇
  1973年   15213篇
排序方式: 共有10000条查询结果,搜索用时 582 毫秒
991.
Technical Physics Letters - The C–V characteristics of Au/Al2O3/In0.52Al0.48As and Au/SiO2/In0.52Al0.48As metal–insulator–semiconductor structures have been studied. It has been...  相似文献   
992.
基于光纤技术的采空区发火监测系统由传感器、数据传输、数据分析与控制三大部分构成,研发新一代适合煤矿安全领域应用的先进传感器、并以此为基础构建新型煤矿安全灾害监测预警系统,对于实现煤矿安全发展具有十分重要的意义。  相似文献   
993.
994.
995.
996.
Fusion behavior of poly(vinyl chloride) (PVC) compounds plays an important role in the development of physical properties of processed material. The fusion characteristics in PVC processing are governed by material variables that affect the fusion with some interactions. In this research, the aim was to characterize the effects of formulation ingredients on fusion characteristics of PVC. Four material parameters, including the contents of nanoclay (NC), azodicarbonamide, calcium stearate, and processing aid, are proposed as affecting variables. The fusion time (FT) as well as fusion factor (FF) are considered fusion indicators and are experimentally determined in some different levels of affecting parameters. The multivariable regression analysis (MRA) and the Artificial Neural Network (ANN) modeling are considered as two analytical methods. The regression analysis result for the FT denotes, in part, significant linear and quadratic effects of NC and also its significant interactions with azodicarbonamide and calcium stearate, whereas that of FF indicates only a linear effect of NC. ANN modeling is performed with a three‐layer (input, hidden, and output) neural network. The results of the comparison of the MRA and ANN predictions with experimental values are reported as the correlation coefficient (R2), mean‐square error, and mean absolute percentage error for both FF and FT parameters. The obtained values clearly denote that the ANN results are more precise and especially more general than those of MRA. However, in the case of FT, improvement of the ANN modeling is much greater than that of FF. J. VINYL ADDIT. TECHNOL., 21:147–155, 2015. © 2014 Society of Plastics Engineers  相似文献   
997.
This study evaluated several physical and sensory parameters of different types of cheese available in the Polish market. The measurements of textural properties were conducted in an Instron universal testing machine, while the colour properties of cheeses were measured using a Minolta chromameter. The chemical composition was determined by means of the near‐infrared spectroscopy (NIRs). Moreover, a trained sensory panel was invited to assess the cheese texture‐related properties. Generally, cheeses with reduced fat content were characterised by higher hardness, adhesiveness, cohesiveness and elasticity. Texture‐related parameters of cheese with canola oil were comparable to that of most of full‐fat cheeses. The correlation analysis between physical and sensory attributes related to cheese textural properties indicated the potential applications of TPA, shear and penetration tests (= 0.766, = 0.75 and = 0.765, respectively) for the evaluation of sensory properties related to the hardness. Meanwhile, the elasticity of cheese obtained from sensory evaluation was strongly correlated with the elasticity determined from the shear test (= 0.722) and moderately correlated with the elasticity from penetration test (= 0.588), indicating a need to refine the method of penetration test. In addition, cheeses exhibited higher meltability during convection heating at 230 °C than microwave heating. The values of meltability for cheese with reduced fat content were lower than those of full‐fat cheese.  相似文献   
998.
999.
In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co2+/F-/TiO2 nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co2+/F-/TiO2 revealed improved photocatalytic performance for denitrification of light oil compared to single TiO2 photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co2+ and F? in the photocatalyst.  相似文献   
1000.
(1-x)Sr0.7Pb0.15Bi0.1TiO3-xBi4Ti3O12 ((1-x)SPBT-xBIT, x = 0-0.125) bulk ceramics were developed and calcined via the solid-state method, aimed at the application of pulsed power capacitors. The phase structures, temperature stability, hysteresis loop, and discharge properties were systematically investigated. Considering both the temperature stability and dielectric properties, 0.925SPBT-0.075BIT bulk ceramics with a capacitance variation satisfying the X7R specification were developed for pulsed power capacitors. The energy storage density was 0.252 J/cm3, and the ceramics showed high temperature stability at 80 kV/cm. The discharge current waveforms of the 0.925SPBT-0.075BIT ceramics were recorded. A high discharge power density of approximately 1.01 × 108 W/kg with an 8 Ω load resistor and short discharge period of 84 ns were achieved at 50 kV/cm. The good temperature stability properties and high power density show that the 0.925SPBT-0.075BIT ceramics are well suited for pulsed power capacitors with a wide temperature range.  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