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   32573篇
  免费   2346篇
  国内免费   1108篇
电工技术   1497篇
技术理论   2篇
综合类   1708篇
化学工业   5874篇
金属工艺   1887篇
机械仪表   2073篇
建筑科学   2458篇
矿业工程   1005篇
能源动力   896篇
轻工业   2036篇
水利工程   553篇
石油天然气   2082篇
武器工业   213篇
无线电   3340篇
一般工业技术   4057篇
冶金工业   1693篇
原子能技术   366篇
自动化技术   4287篇
  2024年   121篇
  2023年   576篇
  2022年   986篇
  2021年   1368篇
  2020年   1124篇
  2019年   901篇
  2018年   1049篇
  2017年   1072篇
  2016年   1038篇
  2015年   1230篇
  2014年   1550篇
  2013年   1999篇
  2012年   2044篇
  2011年   2101篇
  2010年   1846篇
  2009年   1787篇
  2008年   1685篇
  2007年   1647篇
  2006年   1730篇
  2005年   1421篇
  2004年   941篇
  2003年   884篇
  2002年   787篇
  2001年   654篇
  2000年   685篇
  1999年   825篇
  1998年   713篇
  1997年   642篇
  1996年   567篇
  1995年   469篇
  1994年   364篇
  1993年   275篇
  1992年   206篇
  1991年   169篇
  1990年   117篇
  1989年   112篇
  1988年   87篇
  1987年   61篇
  1986年   55篇
  1985年   29篇
  1984年   24篇
  1983年   19篇
  1982年   21篇
  1981年   16篇
  1980年   11篇
  1979年   7篇
  1978年   2篇
  1975年   2篇
  1966年   2篇
  1949年   1篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
介绍了纳米TiO2复合铁钛防锈颜料的制备原理、工艺、技术指标;描述了铁钛防锈涂料的配方、性能检验和产业化进展情况.  相似文献   
22.
Ba0.55Sr0.45TiO3/MgO composites were successfully prepared by the heterogeneous precipitation method and their structural, surface morphological, tunable properties, and dielectric properties at microwave frequency were systemically investigated. Compared with the sample prepared by the traditional solid-state method, the sample prepared by the heterogeneous precipitation method exhibits a smaller grain size, more uniform microstructure, higher tunability, and lower microwave loss, and these properties are very beneficial to the development of the microwave tunable devices application. Moreover, the effects of La2O3 doping on the dielectric and tunable properties of BST/MgO composites are investigated. The result shows that the La3+-doped sample has higher tunability and lower microwave loss than the undoped one.  相似文献   
23.
锌基重防腐双涂层防护技术在高速公路护栏上的应用   总被引:1,自引:0,他引:1  
介绍了双涂层防护技术的进展以及锌基重防腐双涂层防护技术在高速公路护栏上的应用。  相似文献   
24.
A novel chelating resin containing sulfoxide and diethylene glycol, poly{4‐vinylbenzyl‐[2‐2‐(hydroxyethyl)ethoxyl]sulfoxide} (PVESO) was synthesized using chloromethylated polystyrene (PS‐Cl) as material. Its structure was characterized by elemental analysis, infrared spectra, and scanning electron microscopy (SEM). The adsorption capacities of the resin for Hg2+, Ag+, Cu2+, Zn2+, and Pb2+ at various pH values were determined. The maximum adsorption capacities for Hg2+ and Ag+ were 1.56 and 0.75 mmol g?1 respectively. The resin had high selectivity for Hg2+ and Ag+ over the pH range 1.0–7.0. The adsorption capacities for Hg2+ and Ag+ under competitive condition were also determined by batch experiment method. In addition, the adsorption kinetics of the resin towards Hg2+ at different temperatures was also investigated. The results showed that the adsorption rate was governed by film diffusion at 20°C and 25°C, by particle diffusion at 30°C and 35°C. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 6054–6059, 2006  相似文献   
25.
The PbO2 and F-doped PbO2 (F-PbO2) film electrodes have been prepared by an electrodeposition process onto platinum substrate. The changes of their electrochemical activity for oxygen evolution (OE) reaction with accelerated electrolysis time have been studied. The results show that the activity of the electrodes decreases with increasing electrolysis time. This can be attributed to the conductivity variations, which are caused by the decrease of the oxygen vacancy concentration in PbO2 films during OE. The mechanism of the decrease of the oxygen vacancies has been investigated. For F-PbO2 film electrodes, though its electrochemical activity is somewhat lower than that of undoped one, its activity stability is much higher in comparison with that of PbO2. The influence of F doping on the activity of PbO2 film electrodes has been also discussed.  相似文献   
26.
农作物秸秆增强氟石膏复合材料的微观结构研究   总被引:1,自引:0,他引:1  
将玉米秸秆加入改性后的氟石膏中,研究改性剂、玉米秸秆对氟石膏复合材料结构性能的影响;并用苯丙乳液对玉米秸秆纤维进行表面处理,用以改善基体材料和增强材料的界面结合状况,由此显著提高制品性能。  相似文献   
27.
The corrosion behavior of pure aluminum in inhibited and uninhibited 4 MKOH was investigated by means of hydrogen collection, polarization curve measurement and electrochemical impedance spectroscopy (EIS). The results showed that the corrosion of pure aluminum was greatly inhibited by the addition of ZnO and dimethyl amine epoxy propane (designated as DE). EIS and EDAX analyses revealed that ZnO produces its effect by depositing on the aluminum surface, which increases the overpotential of hydrogen evolution. It was also found that the addition of DE could greatly improve the deposition of zinc layers.  相似文献   
28.
南小英  曹南萍  刘江华 《陶瓷》2005,(11):33-35,37
从技术、经济、生态、政策等角度,对采用氧化铝和硅酸铝质工业废料制取耐磨陶瓷作了全面、系统的分析研究,论证了废渣制瓷技术上的可行性,阐明了经济上和生态上的优越性,提出了解决具体问题的办法。  相似文献   
29.
The confined etchant layer technique has been applied to fabricate complex three-dimensional microstructures on nitinol for the first time. HF and HNO3 were locally and simultaneously electrogenerated at the mold surface to etch a nitinol workpiece. NaOH was used as an efficient scavenger to confine the etchant close to the mold. Cyclic voltammetry was employed to study the electrochemical behavior of a Pt electrode in the etching solution in order to choose an appropriate potential for etchant generation on the mold. The thickness of the confined etchant layer was estimated to be several micrometers by inspecting the deviation of the sizes of the etched spots from the sizes of those on the microelectrode. Thus, the composition of the electrolyte could be optimized for better etching precision. By optimizing the composition of the electrolyte, complex microstructures on a Pt-Ir mold bearing the logo “XMU” of Xiamen University were successfully fabricated on nitinol. The etched patterns were approximately negative copies of the mold, and the precision of duplication could easily reach the micrometer scale.  相似文献   
30.
Summary The Stefan-Winkelmann diffusion technique has been used to determine vapor pressures of high boiling point compound-solvents mixtures. Data are reported at a temperature of 67°C for the mixtures polyphenyl ether (6 rings) — benzene and carbowax 1500 — benzene and at a temperature of 100°C for the mixtures polyphenyl ether (6 rings) — toluene and tricresylphosphate-toluene. The range of concentration is only limited by the appearance of a solid phase, and results are in good agreement with those determined by vapor pressure osmometry.Nomenclature A Vapour source - B Flowing gas phase - c Concentration, g-mol/cm3 - DAB Molecular diffusion coefficient, cm2/s - hi Total interface depth, cm - K Parameter defined by equation (6), dimensionless - I Polymer or high boiling point compound - MA Molecular weight - NAZ Molar flux, g-mol/(cm2) (s) - PA Partial pressure at the interface, atm - P Total pressure, atm - R Gas constant, (atm) (cm3) / (°K) (g-mol) - T Temperature, °K - t Time, s - YA Molar fraction at the interface, dimensionless - zo Initial interface depth, cm - zi Drop of the interface depth, cm - z Interface position Greek Letters A Density of the liquid phase, g/cm3  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