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   732432篇
  免费   9039篇
  国内免费   1693篇
电工技术   12975篇
综合类   670篇
化学工业   110555篇
金属工艺   34257篇
机械仪表   24256篇
建筑科学   16497篇
矿业工程   5338篇
能源动力   17562篇
轻工业   53951篇
水利工程   8811篇
石油天然气   18387篇
武器工业   50篇
无线电   76406篇
一般工业技术   154178篇
冶金工业   128154篇
原子能技术   18045篇
自动化技术   63072篇
  2021年   6696篇
  2020年   4908篇
  2019年   6376篇
  2018年   15211篇
  2017年   15376篇
  2016年   14369篇
  2015年   7849篇
  2014年   12812篇
  2013年   31112篇
  2012年   20781篇
  2011年   30056篇
  2010年   24610篇
  2009年   26246篇
  2008年   26905篇
  2007年   27461篇
  2006年   19743篇
  2005年   19450篇
  2004年   18381篇
  2003年   18085篇
  2002年   16612篇
  2001年   16271篇
  2000年   15348篇
  1999年   15492篇
  1998年   37711篇
  1997年   26934篇
  1996年   20547篇
  1995年   15651篇
  1994年   13766篇
  1993年   13633篇
  1992年   10174篇
  1991年   9785篇
  1990年   9741篇
  1989年   9389篇
  1988年   8765篇
  1987年   8050篇
  1986年   7854篇
  1985年   8621篇
  1984年   8158篇
  1983年   7416篇
  1982年   6947篇
  1981年   7119篇
  1980年   6864篇
  1979年   6902篇
  1978年   6878篇
  1977年   7781篇
  1976年   9762篇
  1975年   6064篇
  1974年   5908篇
  1973年   5984篇
  1972年   5116篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
This paper presents part of the work ComEd and Quanta Technology have performed to quantify the locational and temporal value of DER to avoid distribution grid upgrade investments. It focuses on the formulation of a robust and efficient algorithm for DER optimal dispatch on a distribution feeder to mitigate the violation of current and voltage limits using the allocated cost of capacity and locational marginal value of real and reactive DER injection/withdrawal.  相似文献   
2.
Russian Engineering Research - Models based on regression analysis for predicting the operational efficiency of high-pressure roller crushers are considered. A systematized and structured...  相似文献   
3.
Journal of Machinery Manufacture and Reliability - A device based on smart alloys has been designed for use in machine building items, in particular, in nuclear engineering, for preventing...  相似文献   
4.
5.
6.
This study aimed to evaluate the physicochemical characteristics and sensory attributes of beef burgers with the addition of pea fibre as a partial substitute of meat or fat. Three formulations were prepared: control (CON) – similar to the commercial formulation; fibre/less meat (FLM)—5% meat reduction and addition of 1% pea fibre; fibre/less fat (FLF)—7% fat reduction and addition of 1% pea fibre. Non-significant differences were obtained for pH, colour parameters (L* and b*), texture profile, cooking loss and size reduction among formulations. Moreover, sensory analysis with consumers of beef burgers did not indicate differences among the formulations for all the analysed attributes. Therefore, pea fibre is a promising partial replacer for meat and fat in beef burgers due to the preservation of technological parameters and sensory acceptance.  相似文献   
7.
The role of the following factors in the selection of technological bases for manufacturing is considered: the accessibility of the machined surfaces; their parameters and dimensional relationships; their position relative to the forces acting; and the uniformity of the margin distribution.  相似文献   
8.
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   
9.
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   
10.
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   
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