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   3006篇
  免费   119篇
  国内免费   21篇
电工技术   22篇
综合类   4篇
化学工业   746篇
金属工艺   123篇
机械仪表   100篇
建筑科学   55篇
矿业工程   5篇
能源动力   260篇
轻工业   188篇
水利工程   18篇
石油天然气   12篇
无线电   235篇
一般工业技术   741篇
冶金工业   277篇
原子能技术   16篇
自动化技术   344篇
  2024年   4篇
  2023年   43篇
  2022年   94篇
  2021年   135篇
  2020年   119篇
  2019年   91篇
  2018年   151篇
  2017年   124篇
  2016年   130篇
  2015年   85篇
  2014年   130篇
  2013年   246篇
  2012年   140篇
  2011年   192篇
  2010年   152篇
  2009年   130篇
  2008年   144篇
  2007年   122篇
  2006年   80篇
  2005年   84篇
  2004年   53篇
  2003年   53篇
  2002年   45篇
  2001年   38篇
  2000年   30篇
  1999年   48篇
  1998年   44篇
  1997年   42篇
  1996年   39篇
  1995年   36篇
  1994年   35篇
  1993年   30篇
  1992年   29篇
  1991年   15篇
  1990年   18篇
  1989年   11篇
  1988年   8篇
  1987年   25篇
  1986年   20篇
  1985年   17篇
  1984年   17篇
  1983年   18篇
  1982年   14篇
  1981年   15篇
  1980年   11篇
  1979年   12篇
  1978年   7篇
  1977年   6篇
  1976年   4篇
  1974年   3篇
排序方式: 共有3146条查询结果,搜索用时 328 毫秒
91.
Hydroxyapatite (HAP) is the naturally occurring mineral form of calcium apatite and the most studied material as a bone substituent. Considering HAP's inherent properties, this study explored changes in HAP's characteristics from doping with other metals such as Fe. To form pure HAP and Fe-HAP with different amounts of Fe, we used the hydrothermal approach, and the composites that formed were thoroughly analyzed for their crystallinity, surface bonding, morphology, magnetic behavior, mechanical strength, biocompatibility, hemocompatibility, and in vitro cytotoxicity. The powder XRD studies confirmed the samples' crystallinity, and the lowest crystalline size was 19.7 nm in 10Fe-HAP. The FTIR analysis confirmed the formation of HAP by the hydroxyl, phosphate, and carbonate groups. The FESEM demonstrated that the morphology of the pure HAP was rod-shaped, which transformed into spheres after Fe doping. The EDS analysis confirmed the successful formation of HAP and Fe-HAP composites. The magnetic studies indicated the diamagnetic behavior of the pure HAP, while the Fe-doped HAPs had a superparamagnetic nature with saturation magnetizations (Ms) of 2Fe-HAP, 4Fe-HAP, and 10Fe-HAP at 0.0062, 0.0092, and 0.029 emu/g respectively. Assessment of the mechanical properties, biocompatibility, hemocompatibility, and cytotoxicity indicated that the Fe-doped HAPs were superior to the pure HAP, and among the Fe-HAPs, the 10Fe-HAP) had the highest amount of Fe and the best characteristics. The studies also indicated that Ca2+ interactions influenced the cells via HAP doping with that of Fe, equally increasing the physicochemical and biological properties.  相似文献   
92.
93.
Multimedia Tools and Applications - This paper discusses the development of an efficient and automated system for the recognition of facial expressions, which is essentially an application...  相似文献   
94.
95.
The special behaviour of nanowires with respect to electrical conductivity makes them suitable for sensing application. In this paper, we present a copper-ferrous (CuFe) nanowires based sensor for detection of chemicals. CuFe nanowires were synthesized by template-assisted electrochemical method. By optimizing the deposition parameters, continuous nanowires on a copper substrate were synthesized. The morphological and structural studies of the synthesized CuFe nanowires were carried out using scanning electron microscope (SEM) and X-ray diffraction (XRD). Substrates containing CuFe nanowires were moulded to form a capacitor. Different chemicals were used as dielectric in the capacitor which showed that the capacitance was a nonlinear function of the dielectric constant of fluid unlike the linear relation shown by conventional capacitors. This unique property of the nanowires based capacitors may be utilized for developing fluid sensors with improved sensitivity.  相似文献   
96.
Resistant starch in unripe banana offers a possibility to alter the glycemic properties in convenience foods, such as pasta. In this study, pasta formulations were tried by replacing 30% semolina with varying proportions of green banana flour (GBF) and banana-modified starch (MS). The effect of substitution on physicochemical and functional properties, including in-vitro starch digestibility, antioxidant property and consumer acceptability, was evaluated. Among the composite flours, MS recorded higher swelling power and water holding capacity. The replacement of semolina with GBF resulted in higher resistant starch, 4–5 times enhanced indigestible fraction, phenols, flavonoids and antioxidant activity in pasta. Pronounced increment was also observed in potassium, calcium and magnesium content in blended pasta. Optimal cooking time was reduced with the addition of GBF, whereas it was enhanced with MS. GBF and MS in the blends, decreased the hydrolysis rate (up to 24%) and glycemic index (up to 17%) of pasta. However, the addition of MS beyond 10% negatively influenced springiness and chewiness. Microstructural studies explained the positive structural changes with the addition of GBF and MS. Sensory attributes disclosed that the addition of 25% GBF and 5% MS is a desirable proportion for pasta with a functional characteristics.  相似文献   
97.
98.
The Cr:Fe ratio (chromium-to-iron mass ratio) of chromite affects the production of chrome-based ferroalloys. Although the lit-erature contains numerous reports related to the magnetic separation of di...  相似文献   
99.
Journal of Materials Science: Materials in Electronics - Gum kondagogu (GK), a natural biopolymer was successfully employed in the synthesis of trimetallic (AgAuPd) nanocomposites and characterized...  相似文献   
100.
This paper studies a problem for seamless migration of legacy networks of Internet service providers to a software-defined networking (SDN)-based architecture along with the transition to the full adoption of the Internet protocol version 6 (IPv6) connectivity. Migration of currently running legacy IPv4 networks into such new approaches requires either upgrades or replacement of existing networking devices and technologies that are actively operating. The joint migration to SDN and IPv6 network is considered to be vital in terms of migration cost optimization, skilled human resource management, and other critical factors. In this work, we first present the approaches of SDN and IPv6 migration in service providers' networks. Then, we present the common concerns of IPv6 and SDN migration with joint transition strategies so that the cost associated with joint migration is minimized to lower than that of the individual migration. For the incremental adoption of software-defined IPv6 (SoDIP6) network with optimum migration cost, a greedy algorithm is proposed based on optimal path and the customer priority. Simulation and empirical analysis show that a unified transition planning to SoDIP6 network results in lower migration cost.  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