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   267321篇
  免费   4062篇
  国内免费   829篇
电工技术   5194篇
综合类   346篇
化学工业   38851篇
金属工艺   10420篇
机械仪表   8632篇
建筑科学   6429篇
矿业工程   1100篇
能源动力   6615篇
轻工业   23542篇
水利工程   2657篇
石油天然气   3929篇
武器工业   68篇
无线电   35230篇
一般工业技术   51641篇
冶金工业   47938篇
原子能技术   5444篇
自动化技术   24176篇
  2021年   2213篇
  2019年   2213篇
  2018年   3665篇
  2017年   3725篇
  2016年   3955篇
  2015年   2492篇
  2014年   4353篇
  2013年   11821篇
  2012年   6983篇
  2011年   9490篇
  2010年   7400篇
  2009年   8247篇
  2008年   9119篇
  2007年   9023篇
  2006年   8149篇
  2005年   7446篇
  2004年   7137篇
  2003年   6970篇
  2002年   6605篇
  2001年   6592篇
  2000年   6292篇
  1999年   6368篇
  1998年   14421篇
  1997年   10404篇
  1996年   8224篇
  1995年   6520篇
  1994年   5799篇
  1993年   5669篇
  1992年   4629篇
  1991年   4249篇
  1990年   4086篇
  1989年   3824篇
  1988年   3669篇
  1987年   3208篇
  1986年   3103篇
  1985年   3665篇
  1984年   3438篇
  1983年   3078篇
  1982年   2896篇
  1981年   2988篇
  1980年   2799篇
  1979年   2672篇
  1978年   2533篇
  1977年   2981篇
  1976年   3585篇
  1975年   2335篇
  1974年   2328篇
  1973年   2330篇
  1972年   1858篇
  1971年   1752篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
Application of brown titanium dioxide (TiO2-x) and its modified composite forms in the photocatalytic decomposition of organic pollutants in the environment is a promising way to provide solutions for environmental redemption. Herein, we report the synthesis of effective and stable TiO2-x nanoparticles with g-C3N4, RGO, and multiwalled carbon nanotubes (CNTs) using a simple hydrothermal method. Among all the as-synthesized samples, excellent photocatalytic degradation activity was observed for RGO-TiO2-x nanocomposite with high rate constants of 0.075 min?1, 0.083 min?1 and 0.093 min?1 for methylene blue, rhodamine-B, and rosebengal dyes under UV–Visible light irradiation, respectively. The altered bandgap (1.8 eV) and the large surface area of RGO-TiO2-x nanocomposite impacts on both absorption of visible light and efficiency of photogenerated charge electron (e?)/hole (h+) pair separation. This resulted in enhanced photocatalytic property of carbon-based TiO2-x nanocomposites. A systematic study on the influence of different carbon nanostructures on the photocatalytic activity of brown TiO2-x is carried out.  相似文献   
82.
Mobile Networks and Applications - Public cloud system offers Infrastructure-as-a-Service (IaaS) to deliver the computational resources on demand. Resource requirements of a cloud environment are...  相似文献   
83.
Russian Microelectronics - The recently developed nanomaterials and their production technologies as intellectual property objects (IPOs) are considered. The role of the informational-analytical...  相似文献   
84.
Strength of Materials - Creep constitutive equations have been derived for the materials that exhibit the properties of orthotropy (transversal isotropy) and transient creep under cyclic loading. A...  相似文献   
85.
The ‐centroid problem or leader–follower problem is generalized considering different customer choice rules where a customer may use facilities belonging to different firms, if the difference in travel distance (or time) is small enough. Assuming essential goods, some particular customer choice rules are analyzed. Linear programming formulations for the generalized ‐medianoid and ‐centroid problems are presented and an exact solution approach is applied. Some computational examples are included.  相似文献   
86.
High Temperature - Experimental findings suggest that a strongly ionized, arc He plasma of atmospheric pressure does not exist in the state of the local thermodynamic equilibrium (LTE) expected for...  相似文献   
87.
88.
89.
90.
C-axis textured thin films of gallium-doped indium zinc oxide (GIZO) with a 2% ratio of Ga/Zn, were obtained via RF-magnetron sputtering with high transparency and electrical conductivity. A Box-Behnken response surface design was used to evaluate the effects of the deposition parameters (In2O3 target power, deposition time, and substrate temperature) on the chemical composition, optical, electrical, and structural properties of the GIZO films. The optical constants and the electrical properties were obtained using optical models. The GIZO stoichiometry, and therefore the In/Zn atomic ratio, affected the crystallinity, crystalline parameters, band gap, and charge carrier mobility of the GIZO films. The charge carrier density was related to the change in the crystalline parameters of the hexagonal structure and the In/Zn atomic ratio. The best electrical conductivity values (1.75?×?103 Ω?1 cm?1) were obtained for GIZO films with In/Zn ratio ≥?1. Several figures of merit (FOM) defined for the visible and solar regions were comparatively used to select the optimal In/Zn atomic ratio that provided the best balance between the conductivity and the transparency. The optimal In/Zn ratio was in a range of 0.85–0.90 for the GIZO films.  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