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   56650篇
  免费   4149篇
  国内免费   2163篇
电工技术   1030篇
技术理论   1篇
综合类   2339篇
化学工业   17603篇
金属工艺   9996篇
机械仪表   4002篇
建筑科学   2045篇
矿业工程   1214篇
能源动力   1551篇
轻工业   4331篇
水利工程   305篇
石油天然气   1638篇
武器工业   327篇
无线电   2389篇
一般工业技术   9755篇
冶金工业   2324篇
原子能技术   464篇
自动化技术   1648篇
  2025年   89篇
  2024年   1128篇
  2023年   1166篇
  2022年   1621篇
  2021年   1762篇
  2020年   1701篇
  2019年   1480篇
  2018年   1465篇
  2017年   1737篇
  2016年   1688篇
  2015年   1765篇
  2014年   2566篇
  2013年   3284篇
  2012年   3501篇
  2011年   4218篇
  2010年   3135篇
  2009年   3308篇
  2008年   2869篇
  2007年   3567篇
  2006年   3373篇
  2005年   2860篇
  2004年   2561篇
  2003年   2121篇
  2002年   1841篇
  2001年   1463篇
  2000年   1255篇
  1999年   1055篇
  1998年   884篇
  1997年   744篇
  1996年   584篇
  1995年   498篇
  1994年   372篇
  1993年   317篇
  1992年   263篇
  1991年   177篇
  1990年   134篇
  1989年   113篇
  1988年   74篇
  1987年   39篇
  1986年   49篇
  1985年   33篇
  1984年   18篇
  1983年   15篇
  1982年   14篇
  1981年   6篇
  1980年   10篇
  1976年   5篇
  1975年   3篇
  1974年   6篇
  1951年   8篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
91.
三维大气电波折射修正实验研究   总被引:4,自引:0,他引:4  
外测系统电波折射修正常用的球面分层法和水平分层法都没有考虑到大气水平不均匀性的影响因此其修正精度不是太高。而三维大气法不仅考虑了大气在垂直方向上的变化,而且也考虑了在水平方向上的变化,所以其修正精度较高。  相似文献   
92.
The mositure content inside the hermetic package of semiconductor de-vice has been quantitatively measured by using in-site sensor technique and computer-aided-test system.The principle and apparatus for measurement are introduced.The results show good repeatability and consistency.This technology can be used as a stan-dard test for controlling the moisture content within semiconductor device package.  相似文献   
93.
铝合金表面激光熔敷耐热涂层工艺研究   总被引:1,自引:0,他引:1  
采用激光熔敷方法在铝合金表面制备一层金属陶瓷耐热涂层。借助金相显微镜,扫描电镜能谱等方法,研究在不同激光工艺参数下熔敷层的界面和表面;对比不同激光输入能量时涂层稀释率的变化;不同成分激光熔敷层的组织形态及成分分布。结果表明:激光熔敷层显微组织为垂直界面方向的树枝晶;激光熔敷金属陶瓷粉末时,氧化锆陶瓷含量在涂层中呈梯度分布,而未呈现分层现象。  相似文献   
94.
A simple strategy, based on the integration of the components of the momentum balance equation, yields a small set of nonlinear algebraic equations that models viscous flow with free surfaces. This strategy is applied to two cases already studied by numerical analysis; they are (a) slot coating and (b) forward roll-coating.

The simple models presented in this work are employed to predict the behavior of both coating devices as a function of the relevant dimensionless parameters. The results obtained show that the simple models correctly estimate the general trends given by more realistic ones based on finite element analysis. The technique applied is particularly successful when the Reynolds number is small.  相似文献   
95.
Improvement of the interface contact between biological objects and electronic devices can significantly enhance the quality of electronic signal transfer. The surface of biosensor can be artificially modified in order to strengthen the adhesion of biological cells. We report on results of fabrication of micron and submicron golden spines by means of e-beam lithography and electroplating. The fabrication technique allows easy modification of the size and shape of golden spines by variation of processing parameters. The structures with different spine profiles and spacing have been fabricated for optimization of cell growth conditions. We present the results of growth of rat cortical neurons on the surface of spine modified samples. Well-defined cell guidance was established at the spine arrays. Furthermore, the results of transmission electron microscope and focused ion beam technique confirm the good adhesion between the spines and cell structures.  相似文献   
96.
用非平衡脉冲直流磁控溅射技术制备出了复合CrCO-Ti和CrCO保护薄膜,在氮气气氛条件下,研究了这些薄膜的结构、粘合力、耐磨性等随退火温度的变化规律和掺Ti对其性能的影响.得出结论:沉积的薄膜是非晶态薄膜,这些薄膜的耐磨能力达到10-8mm3/Nm;掺Ti能增强薄膜的柔韧性和负载能力,但在400℃及以上退火条件下,薄膜的结构、粘合力、耐磨能力等开始变化,而OEM为40%的复合CrCO-Ti薄膜具有较好的热稳定性.  相似文献   
97.
A semiconducting single-walled carbon nanotubes (s-SWCNTs) interlayer between poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and n-Si was used for high performance organic-Si hybrid photovoltaic (PV) devices. The s-SWCNTs films with different thickness were utilized to investigate the PV effect on PEDOT:PSS/Si device performance. The surface potential of Si substrate with s-SWCNTs was dramatically reduced, which increased the compatibility between Si and PEDOT:PSS. In addition, s-SWCNTs with good semiconducting properties, guaranteed the charge transfer between Si and PEDOT:PSS. Therein, the electrical contact was dramatically improved with addition of s-SWCNTs interlayer, which led to increased fill factor. A power conversion efficiency (PCE) of 12.14% was achieved with an optimized thickness of s-SWCNTs layer. The s-SWCNTs interface layer was fabricated by a simple solution processed method, which was easily coupled with organic-Si solar cells to enhance the PCE.  相似文献   
98.
Metallic surface nanopatterns are prepared by a template‐confined dewetting process with multiple structural controllabilities. The morphology of the building blocks is homogeneous throughout the surface nanopatterns, as the dewetting process proceeds separately in each bowl. The features of the building units in the surface patterns are highly dependent on the annealing temperature. Importantly, the size and composition of the nanoparticles in the surface nanopatterns can be pre‐calculated and designed by manipulating the thickness of the evaporated metallic films. The heating temperature and composition of the building units influence the surface‐enhanced Raman scattering (SERS) and plasmonic properties, thus tuning the localized surface plasmon resonance peaks over a broad range (from visible to near infrared). The introduction of silver in the gold surface nanopatterns enhances the SERS performance dramatically. This work not only provides a powerful route to fabricate surface nanopatterns, but also supplies a platform to study the mechanism of the complicated dewetting processes of metals.  相似文献   
99.
This work is dealing with the influence of surface treatment on ohmic contacts to hexagonal N-type SiC with medium doping level. The contact materials were Ni and Ni2Si. The structures had to be annealed at high temperatures in order to reach ohmic behavior. A number of surface treatment methods were tested: wet cleaning, plasma etching, intentional oxidation with etching, H2 annealing and their combinations. After some types of cleaning, the SiC surface was immediately analysed using the XPS method. The results of the analyses showed that the composition of the surface was not much influenced by these treatments. At lower annealing temperatures (approx. up to 850 °C) the prepared contacts showed Schottky behavior with large scatter of parameters. After annealing at approx. 960 °C, where the onset of ohmic behavior is expected, the structures were truly ohmic and of good parameters. Cleaning methods had just a negligible influence on the electrical parameters of the ohmic contacts. An explanation for these observed facts is suggested: Although - already on the basis of the XPS results - we could speak about a negligible influence of the cleaning onto the contact parameters, there might come across also other mechanisms coming from interaction of contact materials with SiC, which caused similar behavior of ohmic contacts on differently treated surfaces.  相似文献   
100.
李广龄 《金属制品》1996,22(5):6-10
分析了Zn-5%Al-RE合金镀层钢丝表面不平整的原因,并提出了应采取的措施。  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