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   1421篇
  免费   51篇
  国内免费   4篇
电工技术   25篇
综合类   1篇
化学工业   409篇
金属工艺   16篇
机械仪表   25篇
建筑科学   33篇
矿业工程   7篇
能源动力   22篇
轻工业   67篇
水利工程   10篇
石油天然气   1篇
武器工业   1篇
无线电   105篇
一般工业技术   252篇
冶金工业   238篇
原子能技术   11篇
自动化技术   253篇
  2023年   11篇
  2022年   38篇
  2021年   29篇
  2020年   17篇
  2019年   18篇
  2018年   23篇
  2017年   24篇
  2016年   26篇
  2015年   19篇
  2014年   34篇
  2013年   100篇
  2012年   61篇
  2011年   70篇
  2010年   46篇
  2009年   50篇
  2008年   33篇
  2007年   30篇
  2006年   55篇
  2005年   47篇
  2004年   51篇
  2003年   49篇
  2002年   35篇
  2001年   17篇
  2000年   22篇
  1999年   16篇
  1998年   18篇
  1997年   20篇
  1996年   24篇
  1995年   16篇
  1994年   20篇
  1993年   16篇
  1992年   24篇
  1991年   11篇
  1990年   14篇
  1989年   19篇
  1988年   20篇
  1987年   12篇
  1986年   17篇
  1985年   15篇
  1982年   19篇
  1981年   13篇
  1980年   14篇
  1979年   16篇
  1978年   23篇
  1977年   16篇
  1976年   25篇
  1975年   16篇
  1974年   21篇
  1973年   14篇
  1970年   10篇
排序方式: 共有1476条查询结果,搜索用时 31 毫秒
101.
Administered relational size problems in the context of ordinal series to 72 4-5 yr olds. Solution was facilitated when Ss were directed to locate a terminal member (the smallest) of the series. In contrast, Ss who were instructed to locate a nonterminal member without prior designation of a terminal member were unable to achieve solution of the problem. Age- and sex-related differences in performance were observed as well as differences associated with stimulus arrangements and stimulus sizes. The outcomes are discussed in terms of composite task demands. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
102.
In clinical trials it may be necessary to convert a commercial tablet to a capsule so that the identity of each drug being tested remains unknown until the trial is completed. This study shows that for six commercial tablets, after pulverization and encapsulation of the powder, the in vitro dissolution was faster for one product, slower for two products and essentially unchanged for three products.  相似文献   
103.
104.
105.
A statistical model for identifying proteins by tandem mass spectrometry   总被引:51,自引:0,他引:51  
A statistical model is presented for computing probabilities that proteins are present in a sample on the basis of peptides assigned to tandem mass (MS/MS) spectra acquired from a proteolytic digest of the sample. Peptides that correspond to more than a single protein in the sequence database are apportioned among all corresponding proteins, and a minimal protein list sufficient to account for the observed peptide assignments is derived using the expectation-maximization algorithm. Using peptide assignments to spectra generated from a sample of 18 purified proteins, as well as complex H. influenzae and Halobacterium samples, the model is shown to produce probabilities that are accurate and have high power to discriminate correct from incorrect protein identifications. This method allows filtering of large-scale proteomics data sets with predictable sensitivity and false positive identification error rates. Fast, consistent, and transparent, it provides a standard for publishing large-scale protein identification data sets in the literature and for comparing the results obtained from different experiments.  相似文献   
106.
107.
108.
Titania microspheres with narrow size distribution and diameters of about 1 µm were prepared and subsequently functionalized using surface‐initiated atom transfer radical polymerization (ATRP) of N‐isopropylacrylamide. The ATRP initiator was immobilized on the particle surface via acylation of surface hydroxyl groups with α‐bromoisobutyryl bromide. Subsequently, an established ATRP reaction system was used for the preparation of titania surface‐grafted poly(N‐isopropylacrylamide) (PNiPAAm). Characterization was performed with electron microscopies, X‐ray diffraction, infrared spectroscopy and dynamic light scattering. It was found that the particle size in aqueous dispersions changed reversibly with temperature as expected for a shell of PNiPAAm, a polymer with a lower critical solution temperature at 32 °C. This confirmed the successful preparation of functional, stimuli‐responsive TiO2 microparticles via a straightforward controlled surface‐initiated polymerization method.  相似文献   
109.
In this experimental study a practical geometrical comparison between inclined (angle φ) free and repelled hydraulic jumps (the latter in non prismatic but abruptly expanding channels) is presented, analysed and discussed. For repelled hydraulic jumps a considerable parameter is the expansion ratio r (=channels’ width ratio), which here is changing from r =0.5 to r =0.7. The comparison is made with the free jump (in prismatic channel, r =1), in the same ranges of angles φ (0° ⩽ φ ⩽8°) and Froude numbers (2⩽Fr 1⩽8). A practical arithmetic example is presented to show the behavioral change of conjugate depths, lengths L and depths at 0.5L, in order to receive a comparison among all pertinent geometrical quantities. The present results may be useful for the hydraulic engineering when designing open channels.  相似文献   
110.
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