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   714篇
  免费   24篇
电工技术   13篇
综合类   1篇
化学工业   180篇
金属工艺   27篇
机械仪表   29篇
建筑科学   35篇
矿业工程   12篇
能源动力   19篇
轻工业   58篇
水利工程   6篇
石油天然气   1篇
无线电   35篇
一般工业技术   95篇
冶金工业   118篇
原子能技术   2篇
自动化技术   107篇
  2023年   9篇
  2022年   32篇
  2021年   28篇
  2020年   16篇
  2019年   17篇
  2018年   12篇
  2017年   11篇
  2016年   18篇
  2015年   19篇
  2014年   34篇
  2013年   53篇
  2012年   34篇
  2011年   48篇
  2010年   44篇
  2009年   26篇
  2008年   29篇
  2007年   32篇
  2006年   32篇
  2005年   13篇
  2004年   20篇
  2003年   13篇
  2002年   16篇
  2001年   16篇
  2000年   11篇
  1999年   13篇
  1998年   9篇
  1997年   12篇
  1996年   5篇
  1995年   6篇
  1994年   6篇
  1993年   10篇
  1992年   10篇
  1991年   4篇
  1990年   5篇
  1987年   4篇
  1986年   8篇
  1985年   4篇
  1984年   3篇
  1983年   3篇
  1982年   7篇
  1981年   10篇
  1979年   4篇
  1978年   3篇
  1977年   5篇
  1976年   2篇
  1975年   3篇
  1974年   3篇
  1961年   2篇
  1960年   2篇
  1959年   2篇
排序方式: 共有738条查询结果,搜索用时 16 毫秒
71.
Experimental breads were made with 2, 4, 6, 8, 10, and 12% torula yeast flour (TYF). Taste panels found that bread fortified with 8% TYF was acceptable. Eight percent TYF raised protein content from 12.42% for all wheat flour bread to 14.22% for supplemented bread. Amino acid analyses indicated a marked increase in amino acid content especially lysine. The protein efficiency ratio (PER) for rats on all-wheat-flour bread was 1.3 1; replacing 8% of the wheat flour with TYF raised PER of supplemented bread to 2.28. Total carcass nitrogen retained by animals fed a diet containing supplemented bread was higher than that retained by rats whose protein was obtained from unsupplemented bread.  相似文献   
72.
Place marketing and local proactivity in the economic development of Benoni   总被引:1,自引:1,他引:0  
  相似文献   
73.
Review of book: Heinz Kohut (Au.) Paul Tolpin and Marian Tolpin (Eds.) The Chicago Institute Lectures. Hillsdale, NJ: Analytic Press, 1996, 432 pp. Reviewed by Donna M. Orange. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
74.
The electrochemical permeation technique for studying transport and trapping of hydrogen in Fe-40 at.% Al alloy at temperatures of 5, 25, 45 and 65 °C was used in the paper. The influence of temperature on the effective hydrogen diffusion coefficient, hydrogen permeation rate and hydrogen solubility was determined. The activation energy of hydrogen diffusion in iron aluminide in the studied temperature range was also determined.  相似文献   
75.
76.
Thin films of poly(1,4-phenylenemethilidynenitrilo-1,4-phenylenenitrilomethilidyne) (PPI) have been prepared by chemical vapor deposition in the horizontal geometry using gaseous argon as a transport agent. PPI thin films have been grown by polycondensation of para-phenylene diamine (PPDA) and terephtal aldehyde (TPA). Fourier Transform Infrared spectra confirm formation of PPI layers without end groups. The strongest absorption band with discernible vibronic progression has been found to be due to superposition of 2.64, 2.82 and 3.03 eV bands corresponding to interband transitions connecting electronic ground state and vibrational levels of electronic excited state. A feature seen at about 2.6 eV in the spectra of PPI films prepared at higher temperatures of PPDA and TPA sources are attributed to excitons connected with the π-π? gap. Shoulder at 3.31 eV is attributed to interband transitions between delocalized states, while a peak at 4.2 eV is attributed to excitons formed by localized holes and delocalized electrons and vice versa and interband transitions connecting delocalized and localized bands, with the binding energy of about 0.8 eV. Thin films prepared at low temperatures of monomers consist of randomly distributed PPI chains weakly bound together.  相似文献   
77.
Memorializes Mary Alice White for her many contributions to school psychology. White was foremost an experimental and behaviorally oriented educational psychologist, whose interests cut across educational, clinical, and school psychology and technology applications to schooling. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
78.
The main goal of the study presented in the paper was to experimentally demonstrate the feasibility of lignite gasification to hydrogen-rich gas under the underground conditions simulated in the ex situ reactor. The in situ gasification conditions were simulated both in respect to the coal seam and the surrounding stratum. In the 54-h experiment the process of lignite gasification with oxygen and steam as gasifying medium was tested. The experiment was initially divided into three stages: the ignition stage, the oxygen stage and the steam stage.The gas produced in the steam gasification stage was characterized by the calorific value of 7.8 MJ/m3 and average hydrogen content of 46.3 vol.%. Unfortunately a rapid decrease in the temperature levels and in the amount of produced gas proved that the tested lignite of 53 vol.% moisture content was not suitable for steam gasification. A great amount of thermal energy was consumed for water evaporation which led to a considerable heat loss. An addition of stoichiometric amount of water in the system by adding steam caused the seam to extinguish. Thus only oxygen could be used as the gasifying medium in the gasification of the tested lignite. The average calorific value of gas produced in the stable operation during oxygen gasification stage equaled 5.2 MJ/m3 with the average gas production rate of 16.0 m3/h and the average hydrogen content in the produced gas of 26.4 vol.%.  相似文献   
79.
Electrospun nylon 6 fiber mats were deposited on woven 50/50 nylon/cotton fabric with the motive of making them into protective material against submicron‐level aerosol chemical and biological threats. Polymer solution concentration, electrospinning voltage, and deposition areal densities were varied to establish the relationships of processing‐structure‐filtration efficiency of electrospun fiber mats. A high barrier efficiency of greater than 99.5% was achieved on electrospun fiber mats without sacrificing air permeability and pressure drop. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010  相似文献   
80.
A simple, easily accessible solvent‐free method for the dispersion of MWCNTs into PET is proposed, based on the preparation of a microparticulate polymer/nanotube masterbatch via cryogenic impact‐milling and its subsequent melt blending with the bulk polymer. Thermal and mechanical properties of nanocomposites prepared using this method were evaluated as a function of nanotube concentration. Thermal stability was improved, and superior crystallization behavior of PET in the nanocomposites was observed. Significant improvements of around 25% in tensile strength and tensile modulus of the nanocomposites was achieved using this strategy, with only 0.25 wt.‐% MWCNT, compared to previous literature data where 1 wt.‐% MWCNT was employed.

  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