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   213220篇
  免费   5119篇
  国内免费   2134篇
电工技术   5092篇
技术理论   2篇
综合类   2331篇
化学工业   33917篇
金属工艺   9840篇
机械仪表   7364篇
建筑科学   7320篇
矿业工程   1774篇
能源动力   5546篇
轻工业   18597篇
水利工程   2208篇
石油天然气   5681篇
武器工业   203篇
无线电   24287篇
一般工业技术   37903篇
冶金工业   35089篇
原子能技术   4682篇
自动化技术   18637篇
  2022年   1418篇
  2021年   2653篇
  2020年   1916篇
  2019年   2093篇
  2018年   3022篇
  2017年   3190篇
  2016年   3202篇
  2015年   2904篇
  2014年   4409篇
  2013年   9937篇
  2012年   6674篇
  2011年   8780篇
  2010年   7214篇
  2009年   7891篇
  2008年   7850篇
  2007年   7811篇
  2006年   7016篇
  2005年   6425篇
  2004年   5655篇
  2003年   5166篇
  2002年   5107篇
  2001年   4983篇
  2000年   4808篇
  1999年   5123篇
  1998年   11308篇
  1997年   8197篇
  1996年   6456篇
  1995年   4899篇
  1994年   4155篇
  1993年   3933篇
  1992年   2938篇
  1991年   2789篇
  1990年   2605篇
  1989年   2598篇
  1988年   2507篇
  1987年   2226篇
  1986年   2138篇
  1985年   2424篇
  1984年   2237篇
  1983年   2037篇
  1982年   1914篇
  1981年   1968篇
  1980年   1812篇
  1979年   1827篇
  1978年   1779篇
  1977年   2115篇
  1976年   2694篇
  1975年   1559篇
  1974年   1553篇
  1973年   1612篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Tang  Haina  Zhao  Xiangpeng  Ren  Yongmao 《Wireless Networks》2022,28(3):1197-1202
Wireless Networks - Geolocation is important for many emerging applications such as disaster management and recommendation system. In this paper, we propose a multilayer recognition model (MRM) to...  相似文献   
2.
3.
In this study, dilute chemical bath deposition technique has been used to deposit CdZnS thin films on soda-lime glass substrates. The structural, morphological, optoelectronic properties of as-grown films have been investigated as a function of different Zn2+ precursor concentrations. The X-ray diffractogram of CdS thin-film reveals a peak corresponding to (002) plane with wurtzite structure, and the peak shift has been observed with the increase of the Zn2+ concentration upon formation of CdZnS thin film. From morphological studies, it has been revealed that the diluted chemical bath deposition technique provides homogeneous distribution of film on the substrate even at a lower concentration of Zn2+. Optical characterization has shown that the transparency of the film is influenced by Zn2+ concentration and when the Zn2+ concentration is varied from 0 M to 0.0256 M, bandgap values of resulting films range from 2.42 eV to 3.90 eV while. Furthermore, electrical properties have shown that with increasing zinc concentration the resistivity of the film increases. Finally, numerical simulation validates and suggests that CdZnS buffer layer with composition of 0.0032 M Zn2+ concentration would be a promising candidate in CIGS solar cell.  相似文献   
4.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
5.
6.
Hydraulic fracturing with slickwater is a field-proven stimulation technology used in tight reservoirs. Because of the high pumping rate associated with slickwater fracturing, drag reduction (DR) is critical in minimizing pressure drop and the success of oilfield operations. In this paper, a new type of drag reducer (SPR) was synthesized with acrylamide and 12-allyloxydodecyl acid sodium, and its drag reduction performance was evaluated. The results showed that the new drag reducer features low molecular weight, fast-dissolving rate and low interfacial tension. The algorithm of estimating the drag reduction rate of non-Newtonian fluid SPR was proposed and validated. Empirical or semianalytical models for estimating the friction ratio (σ) or friction factor (λ or f) were used to simulate the turbulence behavior of the SPR drag reducer under different Reynolds numbers (Re). The modified Virk's correlation could accurately model the turbulent behavior of the SPR drag reducer. A unified calculation formula was established in this study for different pipe diameters.  相似文献   
7.
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically...  相似文献   
8.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is...  相似文献   
9.
Synthetic active matters are perfect model systems for non-equilibrium thermodynamics and of great potential for novel biomedical and environmental applications. However, most applications are limited by the complicated and low-yield preparation, while a scalable synthesis for highly functional microswimmers is highly desired. In this paper, an all-solution synthesis method is developed where the gold-loaded titania-silica nanotree can be produced as a multi-functional self-propulsion microswimmer. By applying light, heat, and electric field, the Janus nanotree demonstrated multi-mode self-propulsion, including photochemical self-electrophoresis by UV and visible light radiation, thermophoresis by near-infrared light radiation, and induced-charge electrophoresis under AC electric field. Due to the scalable synthesis, the Janus nanotree is further demonstrated as a high-efficiency, low-cost, active adsorbent for water decontamination, where the toxic mercury ions can be reclaimed with enhanced efficiency.  相似文献   
10.
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