首页 | 官方网站   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   10302篇
  免费   901篇
  国内免费   98篇
工业技术   11301篇
  2024年   39篇
  2023年   211篇
  2022年   322篇
  2021年   654篇
  2020年   580篇
  2019年   719篇
  2018年   831篇
  2017年   783篇
  2016年   773篇
  2015年   471篇
  2014年   766篇
  2013年   1140篇
  2012年   711篇
  2011年   806篇
  2010年   514篇
  2009年   434篇
  2008年   280篇
  2007年   204篇
  2006年   167篇
  2005年   119篇
  2004年   121篇
  2003年   73篇
  2002年   75篇
  2001年   39篇
  2000年   36篇
  1999年   32篇
  1998年   50篇
  1997年   29篇
  1996年   32篇
  1995年   30篇
  1994年   20篇
  1993年   22篇
  1992年   13篇
  1991年   26篇
  1990年   21篇
  1989年   17篇
  1988年   12篇
  1987年   11篇
  1986年   12篇
  1985年   12篇
  1984年   19篇
  1983年   19篇
  1982年   7篇
  1981年   5篇
  1980年   4篇
  1979年   6篇
  1978年   5篇
  1977年   6篇
  1976年   6篇
  1975年   3篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Wireless Personal Communications - Software-Defined Networks (SDNs) are developed to compensate the complicated function of the controlling parts of the given network elements and making the...  相似文献   
12.
13.
Bioactive glasses (BGs) have been used for bone formation and bone repair processes in recent years. This study investigated the titanium substitution effect on 58S BGs (Ti-BGs) 60SiO2-(36 − X)CaO-4P2O5-XTiO2 (X = 0, 3, and 5 mol.%) prepared by the sol-gel technique, and the main goal was to find the optimum amount of titanium in Ti-BGs. Synthesized BGs, which were investigated after immersion in simulated body fluid (SBF), were tested by X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy. Moreover alkaline phosphate (ALP) activity, 3-(4,5dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and antibacterial studies were employed to investigate the biological properties of Ti-BGs. According to the FTIR and XRD test results, hydroxyapatite (HA) formation on Ti-BGs surfaces was confirmed. Meanwhile, the presence of 5 mol.% compared to 3 mol.% increased the HA grain distribution and their size on the Ti-BGs surface. Additionally, MTT and ALP results confirmed that the optimal amount of titanium substitution in BG was 5 mol.%. Since 5 mol.% Ti incorporated BG (BG-5) had the highest biocompatibility level, antibacterial properties, maximum cell proliferation, and ALP activity among the synthesized Ti-BGs, it is presented as the best candidate for further in vivo investigations.  相似文献   
14.
Wireless Networks - The original version of this article unfortunately contained a mistake in the title. The correct title has been published with this erratum.  相似文献   
15.
A new, efficient and recoverable heterogeneous catalyst was successfully synthesized by functionalization of mesoporous silica FSM-16. The FSM-16/CPTMS-Rh-  相似文献   
16.
Well-ordered and surface engineered hierarchical hydroxyapatite microspheres (HAM) were prepared via a template free hydrothermal process. Ethylene diamine tetra (methylene phosphonic acid) (EDTMP) was used as chelating or regulating agent for the first time in this study. The results indicated the formation of sheet-like particles in the absence of EDTMP. On the other hand, microspheres with radially grown nanorods (HAMNR) or nanosheets (HAMNS) on the surface were obtained (with average diameter of 5?µm) in the presence of EDTMP. X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy were used to characterize the crystalline phases in the synthesized samples. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that EDTMP concentration played an important part in regulating the morphology to form well organized microspheres with nanosheets or nanorods on the surface. Brunauer-Emmett-Teller (BET) revealed an increase in the specific surface area with the change in morphology from the HAMNS to HAMNR. Possible mechanisms are proposed to account for the formation of different morphologies based upon thermodynamic and kinetic theories.  相似文献   
17.
18.
19.
20.
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-23

京公网安备 11010802026262号