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   136020篇
  免费   10679篇
  国内免费   5823篇
电工技术   7704篇
技术理论   12篇
综合类   8791篇
化学工业   22174篇
金属工艺   7448篇
机械仪表   8462篇
建筑科学   10658篇
矿业工程   4005篇
能源动力   3744篇
轻工业   8659篇
水利工程   2399篇
石油天然气   7293篇
武器工业   1065篇
无线电   16780篇
一般工业技术   16311篇
冶金工业   6904篇
原子能技术   1650篇
自动化技术   18463篇
  2024年   530篇
  2023年   2070篇
  2022年   3658篇
  2021年   5073篇
  2020年   3806篇
  2019年   3192篇
  2018年   3658篇
  2017年   4175篇
  2016年   3668篇
  2015年   4993篇
  2014年   6240篇
  2013年   7817篇
  2012年   8385篇
  2011年   9118篇
  2010年   8043篇
  2009年   7912篇
  2008年   7999篇
  2007年   7444篇
  2006年   7562篇
  2005年   6681篇
  2004年   4636篇
  2003年   3931篇
  2002年   3647篇
  2001年   3405篇
  2000年   3362篇
  1999年   3714篇
  1998年   3103篇
  1997年   2696篇
  1996年   2414篇
  1995年   2029篇
  1994年   1631篇
  1993年   1264篇
  1992年   1012篇
  1991年   775篇
  1990年   630篇
  1989年   523篇
  1988年   409篇
  1987年   305篇
  1986年   216篇
  1985年   180篇
  1984年   110篇
  1983年   85篇
  1982年   92篇
  1981年   60篇
  1980年   52篇
  1979年   35篇
  1978年   25篇
  1977年   27篇
  1976年   43篇
  1973年   11篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
房地产开发企业会计核算问题探讨   总被引:1,自引:0,他引:1  
本文就房地产开发企业会计核算的现状及特点进行了分析,并提出了完善房地产开发企业会计核算规范的对策。  相似文献   
82.
张兵  孙捷 《世界建筑》2005,(6):106-111
在承接这个项目之前,我们不知道天津东部还有东丽湖这么一大片保存完好的湿地,夕阳映照着辽阔的水面,芦苇中闪现着轻盈的水鸟。邻里中心——作为这片宝地旁边200hm^2大型低密度社区第一个登台亮相的小组团,对参与其中的所有人来说,既有动人的诱惑,又有切实的压力。  相似文献   
83.
Analysis of dinosaur samples by nuclear microscopy   总被引:2,自引:0,他引:2  
Several dinosaur bone and eggshell fossil samples unearthed at different sites in China were analyzed by means of nuclear microscopy. Concentrations and distributions of elements such as Na, Mg, Al, P, S, Ca, Cr, Mn, Fe, Cu, Zn, As, Br, Sr, Y, Ce, Pb and U, etc. were obtained for each sample. The results of quantitative PIXE and RBS analyses show unusually high concentrations of U and Ce in several samples obtained from a period near the K-T boundary (between Cretaceous and Tertiary periods, 65 million years ago), suggesting that some form of environmental pollution could be the cause of dinosaur extinction.  相似文献   
84.
透水性沥青面层材料设计新法及应用   总被引:8,自引:0,他引:8  
本文提出了一种根据主骨料空隙率设计透水性面层沥青混合料级配的新方法,根据这一方法设计的透水性沥青面层具有良好的路面使用功能,应用前景广阔。  相似文献   
85.
86.
Some data of emission and evaporation properties related to tungsten matrix structures of the impregnated cathodes are analyzed. The results indicate that the particle size of tungsten powder and the pore size in the porous matrix determine the total inside surface area of all pores, the diffusion length of barium atoms over tungsten grain surfaces, and the diameter and length of the path through which barium atoms are transported. These factors all relate to the properties and operation mechanism of an impregnated cathode; therefore, it would not be strictly correct to use only the matrix porosity for characterizing the cathode properties. Finally, the preferred structures of porous tungsten matrix depending on different applications of impregnated, cathodes are proposed.  相似文献   
87.
88.
A modified CIECAM02 colour appearance model, named CIECAM02‐m2, is proposed to enable CIECAM02 to predict the simultaneous contrast effect. The structure of the CIECAM02‐m2 is a development from CIECAM02, and contains two different procedures for modifying the reference white; one is for lightness and the other is for hue. The model was tested using a data set accumulated in this study and the LUTCHI data. The CV values for three colour attributes between predictions and experimental data were used to evaluate the accuracy of the model. The low CV values obtained show the performance of the CIECAM02‐m2 model to predict the simultaneous contrast effect satisfactorily. © 2007 Wiley Periodicals, Inc. Col Res Appl, 32, 121 – 129, 2007  相似文献   
89.
HREM and FEG TEM were emphasized and extensively used to follow the most subtle changes in the structure and composition of ball-milled Cu, Fe-Cu, and thermally decomposed Fe60Cu40. Some significant results are obtained and summarized as follows: HREM shows that the deformation of ball-milled copper proceeds mainly by twinning and shear bands (SBs) formation. The nano-grains formed during ball milling (BM) contain a high density of dislocations. The grain boundaries (GBs) of nanocrystalline (NC) Cu prepared by BM are ordered, curved, and strained, but disordering, lattice distortion, and nanovoids in local regions were frequently observed. Nanoscale composition analysis on mechanically alloyed Fe16Cu84 shows that the average Fe content in both the interior of grains and the GBs is close to the designed composition, which proves that a supersaturated solid solution has really formed. However, the Fe content is rather inhomogeneous between the larger and smaller grains, which infers the inhomogeneous mixing of Fe and Cu during mechanical alloying (MA). NC structure and the mechanical force-enhanced fast diffusion are the reasons of the formation of supersaturated solid solutions in immiscible systems with positive enthalpy of mixing. HREM observations carried out with the thermally decomposed Fe60Cu40 solid solution show that the Nishiyama (N-W) or Kurdyumov-Sachs (K-S) orientation relationships exist between alpha-Fe and Cu. Energy dispersive X-ray spectra (EDXS) results show that the Cu content in these alpha-Fe grains reaches as high as 9.5 at.% even after heating to 1,400 degrees C, which is even higher than the maximum solubility of Cu in gamma-Fe at 1,094 degrees C.  相似文献   
90.
酞菁光敏剂对S180移植瘤的疗效   总被引:1,自引:0,他引:1  
研究了GaS_4PC,ZnS_2PC两种酞菁在激光照射下对S180肉瘤的疗效,并讨论了其他酞菁光敏剂对癌细胞的杀伤效果。  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