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   57121篇
  免费   5255篇
  国内免费   2693篇
电工技术   3656篇
技术理论   6篇
综合类   3947篇
化学工业   9174篇
金属工艺   3191篇
机械仪表   3883篇
建筑科学   5142篇
矿业工程   1643篇
能源动力   1617篇
轻工业   4460篇
水利工程   1037篇
石油天然气   3223篇
武器工业   445篇
无线电   6632篇
一般工业技术   6561篇
冶金工业   2338篇
原子能技术   700篇
自动化技术   7414篇
  2024年   236篇
  2023年   1050篇
  2022年   1900篇
  2021年   2691篇
  2020年   2061篇
  2019年   1592篇
  2018年   1753篇
  2017年   1941篇
  2016年   1754篇
  2015年   2366篇
  2014年   2913篇
  2013年   3391篇
  2012年   3730篇
  2011年   4035篇
  2010年   3596篇
  2009年   3343篇
  2008年   3290篇
  2007年   3083篇
  2006年   3030篇
  2005年   2599篇
  2004年   1700篇
  2003年   1611篇
  2002年   1668篇
  2001年   1481篇
  2000年   1289篇
  1999年   1387篇
  1998年   987篇
  1997年   879篇
  1996年   825篇
  1995年   684篇
  1994年   558篇
  1993年   377篇
  1992年   296篇
  1991年   197篇
  1990年   163篇
  1989年   138篇
  1988年   101篇
  1987年   76篇
  1986年   46篇
  1985年   38篇
  1984年   19篇
  1983年   17篇
  1982年   15篇
  1981年   16篇
  1980年   18篇
  1979年   13篇
  1962年   42篇
  1961年   39篇
  1960年   16篇
  1951年   5篇
排序方式: 共有10000条查询结果,搜索用时 7 毫秒
11.
The slight-alkalization of generator internal cooling water (GICW) is widely used to inhibit the corrosion of hollow copper conductor and thereby ensure the safe operation of the generator. CO2 inleakage is increasingly identified as a potential security risk for GICW system. In this paper, the influence of CO2 inleakage on the slight-alkalization of GICW was theoretically discussed. Based on the equilibriums of the CO2-NaOH-H2O system, CO2 inleakage saturation was derived to quantify the amount of the dissolved CO2 in GICW. This parameter can be directly calculated with the measured conductivity and the [Na+] of GICW. The influence of CO2 inleakage on the slight-alkalization conditioning of GICW and the measurement of its water quality parameters were then analyzed. The more severe the inleakage, the narrower the water quality operation ranges of GICW, resulting in the more difficult the slight-alkalization conditioning of GICW. The temperature calibrations of the conductivity and the pH value of GICW show non-linear correlations with the amount of CO2 inleakage and the NaOH dosage. This study provides insights into the influence of CO2 inleakage on the slight-alkalization of GICW, which can serve as the theoretical basis for the actual slight-alkalization when CO2 inleakage occurs.  相似文献   
12.
13.
李涛  叶青  曹国庆 《暖通空调》2020,50(1):31-36
对比分析了国内外标准有关高等级生物安全实验室通风空调系统冗余设计的要求。结合我国已有高等级生物安全实验室,重点分析了送风机、排风机、排风高效过滤器冗余设计的具体实施形式和存在的问题,给出了冗余设计原则建议。  相似文献   
14.
Tian  Dating  Zhou  Yuchi  An  Kai  Kang  Huiting 《Polymer Bulletin》2020,77(4):1847-1868
Polymer Bulletin - Preparation of konjac glucomannan-grafted poly(trimethyl allyl ammonium chloride) (KGM-g-PTMAAC) was carried out using KGM as polysaccharide matrix and TMAAC as cationic...  相似文献   
15.
Since the beginning of the 21st Century, the development of microfluidic chip technology has been very rapid and has attracted the attention of more and more scholars. As an important part of the microfluidic chip, the performance of the micromixer is critical. The fractal structure in the microchannels helps to improve the mixing performance of the micromixer and improve the mixing efficiency of the micromixer. The research results of other scholars are of great significance to the research of the present paper, which mainly studies the effect of changing the baffle state on the mixing efficiency of the micromixer based on the Koch fractal principle. Through simulation analysis, it was found that the mixing efficiency of the baffles distributed on both sides of the microchannel was higher than the mixing efficiency of the baffles distributed on the microchannel side. When the distance between adjacent baffles was divided into 0.15, 0.25 and 0.35 mm, simulated data suggested that the baffle distance of 0.15 mm was best. Increasing the number of baffles from six to eight groups increased the mixing path of the fluid in the microchannel and improved mixing efficiency. A comparison of mixing efficiencies of the 0°, 15° and 30° baffle angles revealed that very significant improvement in mixing efficiency was obtained at 30°. © 2019 Society of Chemical Industry  相似文献   
16.
17.
Science China Technological Sciences - Accurate modelling of lithium ion batteries is crucial for battery management in electric vehicles. Recent studies have revealed the fractional order nature...  相似文献   
18.
In this article, an adaptive fuzzy output feedback control method is presented for nonlinear time-delay systems with time-varying full state constraints and input saturation. To overcome the problem of time-varying constraints, the integral barrier Lyapunov functions (IBLFs) integrating with dynamic surface control (DSC) are applied for the first time to keep the state from violating constraints. The effects of unknown time delays can be removed by using designed Lyapunov-Krasovskii functions (LKFs). An auxiliary design system is introduced to solve the problem of input saturation. The unknown nonlinear functions are approximated by the fuzzy logic systems (FLS), and the unmeasured states are estimated by a designed fuzzy observer. The novel controller can guarantee that all signals remain semiglobally uniformly ultimately bounded and satisfactory tracking performance is achieved. Finally, two simulation examples illustrate the effectiveness of the presented control methods.  相似文献   
19.
Yan  Jing  Zhu  Rongying  Wu  Fan  Zhao  Ziyin  Ye  Huan  Hou  Mengying  Liu  Yong  Yin  Lichen 《Nano Research》2020,13(10):2706-2715
Nano Research - Insufficient intratumoral penetration greatly hurdles the anticancer performance of nanomedicine. To realize highly efficient tumor penetration in a precisely and spatiotemporally...  相似文献   
20.
液滴撞击干燥倾斜壁面铺展实验研究   总被引:2,自引:0,他引:2       下载免费PDF全文
通过高速摄影技术及像素分析方法对液滴撞击干燥倾斜壁面进行实验研究,分析了不同倾斜角及韦伯数(We)对液滴飞溅及铺展的影响,结果表明,倾斜角的增加有利于抑制飞溅的产生;We一定时,液滴的前铺展因子随着倾斜角的增加而增加,后铺展因子随着倾斜角的增加而减小;液滴的前后初始铺展速度均大于液滴的撞击速度,且随着倾斜角的增加而减小。   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