首页 | 官方网站   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   24862篇
  免费   1892篇
  国内免费   572篇
工业技术   27326篇
  2024年   73篇
  2023年   334篇
  2022年   503篇
  2021年   792篇
  2020年   635篇
  2019年   599篇
  2018年   696篇
  2017年   787篇
  2016年   768篇
  2015年   854篇
  2014年   1136篇
  2013年   1590篇
  2012年   1434篇
  2011年   1592篇
  2010年   1351篇
  2009年   1237篇
  2008年   1210篇
  2007年   1136篇
  2006年   1054篇
  2005年   900篇
  2004年   727篇
  2003年   762篇
  2002年   797篇
  2001年   639篇
  2000年   550篇
  1999年   586篇
  1998年   797篇
  1997年   626篇
  1996年   458篇
  1995年   355篇
  1994年   331篇
  1993年   282篇
  1992年   213篇
  1991年   179篇
  1990年   152篇
  1989年   139篇
  1988年   102篇
  1987年   74篇
  1986年   85篇
  1985年   85篇
  1984年   84篇
  1983年   53篇
  1982年   51篇
  1981年   53篇
  1980年   54篇
  1979年   44篇
  1978年   35篇
  1977年   54篇
  1976年   90篇
  1975年   42篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
41.
A 2 cm long three-contact multisection laser has been fabricated for modelocking at very low repetition rates. Active modelocking yields 8.0-12.3 ps pulses at 2.2, 4.3 and 6.5 GHz corresponding to the fundamental, first, and second harmonics of the cavity resonance frequency. This device demonstrates the feasibility of fabricating monolithic pulse sources operating at rates as low as the OC-48 Sonet transmission rate (2.488 Gbit/s).<>  相似文献   
42.
43.
A logic language is suitable for specification if it is equipped with features for data abstraction and modularization. In this paper, an effective mechanism to incorporate function and type into logic programming is presented as the means to embed data abstraction mechanism into logic programming. This incorporation is essentially based on Horn clause logic with equality and a polymorphic type system that is an extension of Mycroft and O’Keefe’s system. This paper also presents an implementation based on Warren Abstract Machine (WAM) and shows the performance, along with a comparison with WAM.  相似文献   
44.
The feasibility of the anodic protection of titanium evaporators in Al2(SO4)3 solution was studied by the measurement of polarization curves, weight loss, solubility of passive film and AC impedance. The protection parameters and efficiency were determined. In addition, the practical technology of anodic protection was studied by screening reference electrodes and auxiliary cathodes. Throwing power was also measured. Four rows of tube-type evaporators of titanium have been anodically protected in situ. Field tests lasting more than one year show satisfactory results.  相似文献   
45.
46.
Robotic synthesis is making possible the synthesis of large, systematically designed sets of compounds. We analyze a 512-compound set that is a 2(9) full factorial experimental design using a recursive partitioning algorithm, FIRM, and a high-dimension visualization tool, TempleMVV. These techniques are used to quickly and easily identify the main trends in the data set and also identify unusual observations. We show that analytical and visualization methods can be used synergistically to analyze a large, complex, high-dimensional data set. We also show that a fractional factorial design of 128 compounds would give essentially the same information.  相似文献   
47.
48.
49.
50.
Core–shell type nanoparticles of poly(L ‐lactide)/poly(ethylene glycol) (LE) diblock copolymer were prepared by a dialysis technique. Their size was confirmed as 40–70 nm using photon correlation spectroscopy. The 1H‐NMR analysis confirmed the formation of core–shell type nanoparticles and drug loading. The particle size, drug loading, and drug release rate of the LE nanoparticles were slightly changed by the initial solvents that were used. The drug release behavior of LE core–shell type nanoparticles showed an initial burst during the first 12 h and then a sustained release until 100 h. The degradation behavior of LE block copolymer nanoparticles was divided into three phases: the initial rapid degradation phase, the stationary phase, and the rapid degradation phase until complete degradation. It was suggested that lidocaine release kinetics were predominantly governed by the diffusion mechanism in the initial burst phase and after that by both of the diffusion and degradation mechanisms. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 2625–2634, 2002  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-23

京公网安备 11010802026262号