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   35058篇
  免费   2296篇
  国内免费   2593篇
电工技术   1179篇
综合类   2053篇
化学工业   6611篇
金属工艺   4153篇
机械仪表   2349篇
建筑科学   756篇
矿业工程   744篇
能源动力   1470篇
轻工业   1979篇
水利工程   186篇
石油天然气   863篇
武器工业   157篇
无线电   5736篇
一般工业技术   8931篇
冶金工业   1342篇
原子能技术   452篇
自动化技术   986篇
  2024年   136篇
  2023年   427篇
  2022年   608篇
  2021年   782篇
  2020年   899篇
  2019年   752篇
  2018年   784篇
  2017年   1066篇
  2016年   1027篇
  2015年   1028篇
  2014年   1554篇
  2013年   1943篇
  2012年   2193篇
  2011年   2732篇
  2010年   1971篇
  2009年   2120篇
  2008年   1965篇
  2007年   2434篇
  2006年   2297篇
  2005年   1917篇
  2004年   1722篇
  2003年   1490篇
  2002年   1302篇
  2001年   1164篇
  2000年   1023篇
  1999年   813篇
  1998年   698篇
  1997年   573篇
  1996年   482篇
  1995年   452篇
  1994年   376篇
  1993年   316篇
  1992年   232篇
  1991年   172篇
  1990年   121篇
  1989年   102篇
  1988年   70篇
  1987年   46篇
  1986年   23篇
  1985年   23篇
  1984年   20篇
  1983年   10篇
  1982年   14篇
  1981年   12篇
  1980年   5篇
  1979年   11篇
  1978年   5篇
  1976年   7篇
  1974年   7篇
  1959年   6篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
介绍了汽车工业生产内装饰复合材料用热熔胶膜的性能及其研制状况。这种热熔胶膜具有使用便捷,高效,生产、使用过程中没有污染的具有热熔胶膜的特长。  相似文献   
22.
聚萘二甲酸乙二醇酯(PEN)的研究及发展   总被引:8,自引:0,他引:8  
综述了聚萘二甲酸乙二醇酯(PEN)的发展历史,合成工艺,应用领域及其与PET的性能比较。  相似文献   
23.
Microgrooves were prepared on Si(100) surface by photolithography and wet etching.Subsequently,Si-N-O films were deposited on the microgrooves by unbalanced magnetron sputtering(UBMS) and micro-patterned surfaces of Si-N-O films were obtained.The size of the micropatterns was measured by surface profilometer.The chemical composition of Si-N-O films were characterized by X-ray photoelectron spectrometry(XPS) and the wettability of the micropatterned surfaces was evaluated by contact angle measurement.The beh...  相似文献   
24.
Experimental and numerical researches were conducted to investigate the cooling performance of a single row of consoles (converging slot-hole) on a large-scale flat-plate model. The results show that the coolant flow from a row of consoles shows good lateral uniformity of adiabatic effectiveness, with regions of slightly enhanced cooling occurring between the consoles. For the console cooling geometry, the interaction between coolant jet from inclined console and the mainstream flow results in reasonable vo...  相似文献   
25.
采用多弧离子镀设备,在高速钢W18Cr4V上先进行等离子氮化,再沉积TiN薄膜,研究了不同渗氮温度和时间对PN+TiN薄膜组织和性能的影响。结果表明,温度为500℃左右和时间为2h以上条件下对W18Cr4V进行渗氮处理后再沉积TiN薄膜,可以得到最佳的薄膜表面显微硬度(1800~2000HV0.05)和膜/基结合力(50N),涂层耐磨性也得到明显提高。  相似文献   
26.
The effects of insoluble eutectic Si particles on the growth of anodic oxide films on ZL114A aluminum alloy substrates were in-vestigated by optical microscopy (OM) and scanning electron microscopy (SE...  相似文献   
27.
28.
Depositing silver on magnesium alloy by both electroless plating and organic coatings was studied. The organic coating was made by immersing samples in organosilicon heat-resisting varnish. In this method the organic coating acts as interlayer between the substrate and silver film. When the reaction starts, silver deposits directly on the interlayer. X-ray diffraction and SEM analysis were used to determine the composition and morphology of the interlayer and silver film. The potentiodynamic polarization curves for corrosion studies of coated magnesium alloys were performed in a corrosive environment of 3.5% NaCl(mass fraction) at neutral pH (6.9). The results indicate that compared with the substrate, the corrosion resistance of coated magnesium alloys increases greatly. Moreover, the method proposed in this work is environmentally friendly, non-toxic chemicals were used. In addition, it provides a new concept for the corrosion inhibition of magnesium alloys.  相似文献   
29.
Nanocrystalline titania films codoped with aluminum and boron were prepared by cathodic vacuum arc deposition. In the process, titanium alloy target was used under an O2/Ar atmosphere, and sensitization of films were carried out by natural dye-sensitized complex in anhydrous ethanol. The structure, surface morphology and UV-vis spectra of titania films codoped were measured by X-ray diffraction analysis, scanning electron microscopy and ultraviolet-visible spectrometer. Theas-deposited films are found to be amorphous. The films annealed were examinedto be of anatase structure with orientation along the (101) planes, the averagecrystal size is in the range between 41 and 45 nm. SEM results show that thereare some pores in the codoped titania films, the optical properties of the dye-sensitized films were also measured which reveals that the spectral responses of films shift to the visible region. Under simulated sunlight illumination, the overall energy conversion efficiency of dye-sensitized nanocrystalline solar cell is 0.9%.  相似文献   
30.
A Fe-Ni soft magnetic film was prepared in sulphate solution by electroplating. The influences of the molar ratio of n [Fe2+ ]/ n [Ni2+ ], current density, bath temperature, pH and L-ascorbic acid concentration on magnetic properties of Fe-Ni alloy film were investigated. The results show that the saturated flux density(BS) of the film increases initially and decreases after it reaches the specific value with the increase of n [Fe2+ ]/ n [Ni2+ ] molar ratio, current density, bath temperature and pH. However, the relationship between L-ascorbic acid concentration and B S keeps linear. It is observed that the coercive force( Hc) is enhanced with the increase of n [Fe2+ ]/ n [Ni2+ ] molar ratio, current density and pH. By comparison, when the bath temperature increases, Hc always decreases. With the increase of L-ascorbic acid concentration, the coercive force increases initially and then decreases.  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