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   78192篇
  免费   9253篇
  国内免费   6338篇
电工技术   7978篇
技术理论   3篇
综合类   8705篇
化学工业   5815篇
金属工艺   4219篇
机械仪表   5326篇
建筑科学   5800篇
矿业工程   3206篇
能源动力   3296篇
轻工业   2113篇
水利工程   4008篇
石油天然气   7385篇
武器工业   1367篇
无线电   8561篇
一般工业技术   7703篇
冶金工业   2809篇
原子能技术   1342篇
自动化技术   14147篇
  2024年   323篇
  2023年   1033篇
  2022年   1948篇
  2021年   2249篇
  2020年   2448篇
  2019年   2145篇
  2018年   1984篇
  2017年   2715篇
  2016年   3057篇
  2015年   3215篇
  2014年   4565篇
  2013年   4736篇
  2012年   5650篇
  2011年   6160篇
  2010年   4639篇
  2009年   4801篇
  2008年   4571篇
  2007年   5462篇
  2006年   5086篇
  2005年   4279篇
  2004年   3601篇
  2003年   3253篇
  2002年   2633篇
  2001年   2160篇
  2000年   1934篇
  1999年   1647篇
  1998年   1254篇
  1997年   1088篇
  1996年   993篇
  1995年   839篇
  1994年   744篇
  1993年   487篇
  1992年   423篇
  1991年   338篇
  1990年   270篇
  1989年   278篇
  1988年   184篇
  1987年   94篇
  1986年   65篇
  1985年   56篇
  1984年   57篇
  1983年   33篇
  1982年   29篇
  1981年   19篇
  1980年   24篇
  1979年   24篇
  1964年   23篇
  1961年   13篇
  1959年   14篇
  1951年   11篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
针对一类特殊而不能直接对其观察的管道(如动物的血管),为了准确了解其内部特征和形态,借助计算机给出了一种用腐蚀算法来重建管道原形的方法。这种方法简单易行,而且精确度高。  相似文献   
102.
基于物质平衡方程、产能方程和递减方程的结合,提出了定容气田开发规划的概算法.该法可用于预测地层压力、井底流动压力、井口流动压力和稳产年限.实际应用表明,本文提供的方法是实用有效的.  相似文献   
103.
Various measures, such as Margin and Bias/Variance, have been proposed with the aim of gaining a better understanding of why Multiple Classifier Systems (MCS) perform as well as they do. While these measures provide different perspectives for MCS analysis, it is not clear how to use them for MCS design. In this paper a different measure based on a spectral representation is proposed for two-class problems. It incorporates terms representing positive and negative correlation of pairs of training patterns with respect to class labels. Experiments employing MLP base classifiers, in which parameters are fixed but systematically varied, demonstrate the sensitivity of the proposed measure to base classifier complexity.  相似文献   
104.
105.
Axial bed depth profiles were experimentally measured in a rotary kiln containing ilmenite particles under steady state and transient conditions. The variables include feed rate of solids, inclination and rotational speed of the kiln. and dam height. The variation of the axial velocity with kiln axis was estimated. The semi-experimental model proposed by Perron and Bui (1990) was modified to include the effect of the variables of the present study. The mean residence time of solids was estimated from the fractional hold-up and expressed in terms of the process variables. The transients induced by a step change in any of the operating conditions were measured as variation of discharge rate of solids with time.  相似文献   
106.
The longitudinal electric field of single and double Gaussian laser beams are used to accelerate electrons. The longitudinal field of the single beam is concentrated on the axis and is favourable for acceleration. A set of two beams is considered. Beams run parallel, collinearly, overlap partially and have a phase difference iπ in between. As a result, the transverse components of fields cancel each other while the longitudinal components are double-fold. In both schemes, the electrons are accelerated in lengths of the Rayleigh range, which is common to the plasma-based accelerators.  相似文献   
107.
本文介绍了我们开发的FED工艺,包括;硅锥场致发射阵列的制作,栅极制作,阳极支柱的制作和平板透明真空封装,对工艺中的难点及对策作了详细描述。利用上述工艺,已经制成了平板数码管,其栅阴特性理想,阳阴之间也能测得明显的场致发射特性产伴有荧光激发。  相似文献   
108.
We present a formal model of asynchronous communication between two digital hardware devices. The model takes the form of a function in the Boyer-Moore logic. The function transforms the signal stream generated by one processor into that consumed by an independently clocked processor, given the phases and rates of the two clocks and the communications delay. The model can be used quantitatively to derive concrete performance bounds on communications at ISO protocol level 1 (physical level). We use the model to show that an 18-bit/cell biphase mark protocol reliably sends messages of arbitrary length between two processors provided the ratio of the clock rates is within 5% of unity.  相似文献   
109.
Scale and sludge from Bulalo geothermal field, Philippines, have been characterized by whole rock analysis, radioactivity counting, size analysis, light microscopy, scanning electron microscopy, and X-ray diffraction. Their leachability was assessed by regulatory leaching procedures and by sequential extraction. Both scale and sludge consisted mostly of oxides of Si, Al, and Fe with no radionuclides detected. The scale had 10% S content. Sulfides and silicates were important phases in both samples having size ranges from submicron to 2 mm. Geothermal soils at Bulalo have higher than normal soil levels of As, S, Cu, Cr, Zn, and Pb but regulatory leaching tests indicated that these elements are not released. However, the sequential extraction showed that As, Cu, and Zn were leachable under extreme conditions.  相似文献   
110.
本文证明了GF(q)的特征为2且n为奇数时GF(q~n)在GF(q)上有自对偶正规基。  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