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   511178篇
  免费   5407篇
  国内免费   1080篇
工业技术   517665篇
  2021年   4167篇
  2019年   4171篇
  2018年   12722篇
  2017年   13175篇
  2016年   11664篇
  2015年   5113篇
  2014年   8406篇
  2013年   19679篇
  2012年   14066篇
  2011年   21195篇
  2010年   17861篇
  2009年   18352篇
  2008年   19445篇
  2007年   20372篇
  2006年   13087篇
  2005年   13616篇
  2004年   12630篇
  2003年   12363篇
  2002年   11220篇
  2001年   10674篇
  2000年   10458篇
  1999年   9871篇
  1998年   20258篇
  1997年   15237篇
  1996年   11942篇
  1995年   9476篇
  1994年   8618篇
  1993年   8672篇
  1992年   7222篇
  1991年   7025篇
  1990年   6995篇
  1989年   6641篇
  1988年   6387篇
  1987年   5975篇
  1986年   5828篇
  1985年   6433篇
  1984年   6167篇
  1983年   5687篇
  1982年   5402篇
  1981年   5506篇
  1980年   5363篇
  1979年   5448篇
  1978年   5509篇
  1977年   5870篇
  1976年   6919篇
  1975年   5087篇
  1974年   5127篇
  1973年   5185篇
  1972年   4459篇
  1971年   4077篇
排序方式: 共有10000条查询结果,搜索用时 250 毫秒
71.
Theoretical Foundations of Chemical Engineering - The development of a thermostable hydrophobic platinum catalyst is an important scientific and practical problem. The purpose of this work is to...  相似文献   
72.
Polymer Bulletin - In this study, we synthesized a new ion-imprinted polymer (IIP) based on introduction of amidoxime groups in acrylonitrile, complexation with Cd2+ ions and polymerization with...  相似文献   
73.
At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free st  相似文献   
74.
The basic stages in the life cycle of a batch of complex engineering products are considered: design, production, operation, and disposal. A priori cost assessment for each stage is discussed. The cost aggregation in the consideration of multiple stages is analyzed. Requirements on the assessment are formulated. Methodological and implementation aspects of the assessment tools are outlined. The conclusion is that it is expedient to predict the costs on the basis of mathematical models of the product batch in an operational environment. The integration of multiple cost estimates is addressed.  相似文献   
75.
Theoretical Foundations of Chemical Engineering - The extraction of nitric and oxalic acids by neutral compounds TBP, DBBP, and TBPO have been studied. The optimal conditions of their separation...  相似文献   
76.
Abstract

Lung deposited surface area (LDSA) is a relatively new metric that has been argued to be more accurate at predicting health effects from aerosol exposure. For typical atmospheric aerosol, the LDSA concentration depends mainly on the concentration of ultrafine particles (e.g. vehicular exhaust emissions and residential wood combustion) and therefore optical methods cannot be used to measure and quantify it. The objective of this study was to investigate and describe typical characteristics of LDSA under different urban environments and evaluate how a diffusion charging-based Pegasor AQ Urban sensor (Pegasor Ltd., Finland) can be used as an alternative to optical sensors when assessing local combustion emissions and respective LDSA concentrations. Long-term (12?months) sensor measurements of LDSA were carried out at three distinctly different measurement sites (four sensor nodes) in the Helsinki metropolitan area, Finland. The sites were affected mainly by vehicular exhaust emission (street canyon and urban background stations) and by residential wood combustion (two detached housing area stations). The results showed that the accuracy of the AQ Urban was good (R2 = 0.90) for the measurement of LDSA when compared to differential mobility particle sizer. The mean concentrations of LDSA were more than twice as high at the street canyon (mean 22 µm2 cm?3) site when compared to the urban background site (mean 9.4 µm2 cm?3). In the detached housing area, the mean concentrations were 12 µm2 cm?3, and wood combustion typically caused high LDSA peaks in the evenings. High correlations and similar diurnal cycles were observed for the LDSA and black carbon at street canyon and urban background stations. The utilization of a small-scale sensor network (four nodes) showed that the cross-station variability in hourly LDSA concentrations was significant in every site, even within the same detached housing area (distance between the two sites ~670?m).  相似文献   
77.
Journal of Communications Technology and Electronics - Abstract—The article presents a rigorous numerical solution, using the Wiener–Hopf method, to the problem of plane wave...  相似文献   
78.
Russian Journal of Non-Ferrous Metals - Rolling bearing rings comprise a large reserve for expanding powder metallurgy production. This reserve is being incompletely implemented. The hot forging of...  相似文献   
79.
Wireless Personal Communications - The rapid development of Information and Communication Technology and the growing number of devices connected to the Internet make the Internet of Things (IoT) as...  相似文献   
80.
Metallurgical and Materials Transactions B - The process of obtaining titanium tetrachloride (TiCl4) from the quartz-leucoxene concentrate (QLC) from the Yaregskoe oil-titanium field was studied....  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