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   60414篇
  免费   15438篇
  国内免费   130篇
电工技术   1102篇
技术理论   1篇
综合类   115篇
化学工业   21994篇
金属工艺   1356篇
机械仪表   2277篇
建筑科学   2155篇
矿业工程   51篇
能源动力   1841篇
轻工业   8901篇
水利工程   402篇
石油天然气   175篇
武器工业   10篇
无线电   10198篇
一般工业技术   15849篇
冶金工业   2220篇
原子能技术   342篇
自动化技术   6993篇
  2023年   333篇
  2022年   187篇
  2021年   1037篇
  2020年   1945篇
  2019年   3586篇
  2018年   3739篇
  2017年   4000篇
  2016年   4518篇
  2015年   4431篇
  2014年   4773篇
  2013年   6381篇
  2012年   4281篇
  2011年   4288篇
  2010年   4050篇
  2009年   3931篇
  2008年   3382篇
  2007年   2879篇
  2006年   2540篇
  2005年   2175篇
  2004年   2041篇
  2003年   1934篇
  2002年   1863篇
  2001年   1653篇
  2000年   1533篇
  1999年   954篇
  1998年   815篇
  1997年   508篇
  1996年   443篇
  1995年   301篇
  1994年   227篇
  1993年   180篇
  1992年   136篇
  1991年   128篇
  1990年   99篇
  1989年   107篇
  1988年   81篇
  1987年   73篇
  1986年   60篇
  1985年   50篇
  1984年   44篇
  1983年   37篇
  1982年   35篇
  1981年   32篇
  1980年   29篇
  1979年   17篇
  1977年   24篇
  1976年   33篇
  1975年   16篇
  1974年   13篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
2.
International Journal of Information Security - Machine learning techniques have been widely used and shown remarkable performance in various fields. Along with the widespread utilization of...  相似文献   
3.
Recent advances in three‐dimensional (3D) printing have enabled the fabrication of interesting structures which are not achievable using traditional fabrication approaches. The 3D printing of carbon microtube composite inks allows fabrication of conductive structures for practical applications in soft robotics and tissue engineering. However, it is challenging to achieve 3D printed structures from solution‐based composite inks, which requires an additional process to solidify the ink. Here, we introduce a wet 3D printing technique which uses a coagulation bath to fabricate carbon microtube composite structures. We show that through a facile nanogrooving approach which introduces cavitation and channels on carbon microtubes, enhanced interfacial interactions with a chitosan polymer matrix are achieved. Consequently, the mechanical properties of the 3D printed composites improve when nanogrooved carbon microtubes are used, compared to untreated microtubes. We show that by carefully controlling the coagulation bath, extrusion pressure, printing distance and printed line distance, we can 3D print composite lattices which are composed of well‐defined and separated printed lines. The conductive composite 3D structures with highly customised design presented in this work provide a suitable platform for applications ranging from soft robotics to smart tissue engineering scaffolds. © 2019 Society of Chemical Industry  相似文献   
4.

LiFe2/3Mn1/3PO4/C composite was prepared by the rheological phase reaction using LiH2PO4, Li2CO3, FePO4, Mn(Ac)2·4H2O and ascorbic acid as starting materials. The crystal structure and morphology of as-synthesized sample were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The analysis of XRD results showed that the obtained sample was single-phase with orthorhombic olivine-type structure (Pnma space group). SEM micrographs revealed that the sample was aggregates, with an irregular morphology. The initial discharge capacity was 166.9, 149.1, 139.6, 112.8, 82.93 mAh g??1 at the rate of 0.1, 0.5, 1, 2, and 10 C, respectively. And when the rate was 0.1, 0.5, 1, 2, and 10 C, the capacity retention was 92.2%, 90%, 92.9%, 97.6%, 91.5% after 50, 100, 200, 200, 500 cycles, respectively.

  相似文献   
5.
6.
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.  相似文献   
7.
Neural Processing Letters - Raman spectroscopy is often used for the composition determination and rapid classification of materials because it can reflect the molecular information of materials....  相似文献   
8.
9.
10.
Polymer‐grafted inorganic particles (PGIPs) are attractive building blocks for numerous chemical and material applications. Surface‐initiated controlled radical polymerization (SI‐CRP) is the most feasible method to fabricate PGIPs. However, a conventional in‐batch reaction still suffers from several disadvantages, including time‐consuming purification processes, low grafting efficiency, and possible gelation problems. Herein, a facile method is demonstrated to synthesize block copolymer–grafted inorganic particles, that is, poly(poly(ethylene glycol) methyl ether methacrylate) (PPEGMEMA)‐b‐poly(N‐isopropylacrylamide) (PNIPAM)–grafted silica micro‐particles using continuous flow chemistry in an environmentally friendly aqueous media. Immobilizing the chain transfer agent and subsequent SI‐CRP can be accomplished sequentially in a continuous flow system, avoiding multi‐step purification processes in between. The chain length (MW) of the grafted polymers is tunable by adjusting the flow time or monomer concentration, and the narrower molar mass dispersity (Р< 1.4) of the grafted polymers reveals the uniform polymer chains on the particles. Moreover, compared with the in‐batch reaction at the same condition, the continuous system also suppresses possible gelation problems.  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