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   721540篇
  免费   8026篇
  国内免费   1212篇
电工技术   12769篇
综合类   585篇
化学工业   113166篇
金属工艺   34108篇
机械仪表   23956篇
建筑科学   15878篇
矿业工程   6200篇
能源动力   17228篇
轻工业   52511篇
水利工程   9495篇
石油天然气   20218篇
武器工业   48篇
无线电   73250篇
一般工业技术   155000篇
冶金工业   114683篇
原子能技术   19100篇
自动化技术   62583篇
  2021年   6629篇
  2019年   6299篇
  2018年   14752篇
  2017年   14923篇
  2016年   14242篇
  2015年   7525篇
  2014年   12557篇
  2013年   31299篇
  2012年   20126篇
  2011年   28683篇
  2010年   23631篇
  2009年   25253篇
  2008年   25935篇
  2007年   26458篇
  2006年   19434篇
  2005年   18797篇
  2004年   17730篇
  2003年   17393篇
  2002年   16336篇
  2001年   15424篇
  2000年   14921篇
  1999年   14348篇
  1998年   32113篇
  1997年   23536篇
  1996年   18316篇
  1995年   14165篇
  1994年   12984篇
  1993年   12709篇
  1992年   10002篇
  1991年   9833篇
  1990年   9686篇
  1989年   9380篇
  1988年   9037篇
  1987年   8337篇
  1986年   8069篇
  1985年   9024篇
  1984年   8300篇
  1983年   8029篇
  1982年   7288篇
  1981年   7440篇
  1980年   7189篇
  1979年   7409篇
  1978年   7386篇
  1977年   8049篇
  1976年   9726篇
  1975年   6672篇
  1974年   6582篇
  1973年   6646篇
  1972年   5821篇
  1971年   5400篇
排序方式: 共有10000条查询结果,搜索用时 15 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.
3.
In this study, amaranth flour was used as an ingredient to prepare gluten-free cookies. The production process and attributes of amaranth cookies were characterised, and the potential use of amaranth flour as a functional ingredient was analysed. Cookies exhibited a non-uniform reddish brown colour and a cookie factor ratio of 4.5 ± 0.6. Storage studies indicated that after 3 weeks at room temperature cookies presented slight variations in the texture. Simulated gastrointestinal digestion of this product was able to release peptides capable of exerting potential antithrombotic and antihypertensive activities, IC50 values of 0.22 ± 0.04 and 0.23 ± 0.03 mg mL−1 protein, respectively. This work demonstrates for the first time that food made with amaranth flour exerts potential antithrombotic and antihypertensive activity. In conclusion, these amaranth cookies could be an alternative way of incorporating potentially health beneficial products for people who choose a conscious diet, including coeliac or vegan consumers.  相似文献   
4.
5.
6.
7.
8.
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   
9.
10.
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