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   762301篇
  免费   11252篇
  国内免费   2777篇
电工技术   14729篇
技术理论   5篇
综合类   1741篇
化学工业   121399篇
金属工艺   30970篇
机械仪表   23952篇
建筑科学   18073篇
矿业工程   5475篇
能源动力   18867篇
轻工业   65819篇
水利工程   8896篇
石油天然气   18074篇
武器工业   284篇
无线电   80117篇
一般工业技术   151633篇
冶金工业   134231篇
原子能技术   17646篇
自动化技术   64419篇
  2021年   7602篇
  2020年   5544篇
  2019年   6898篇
  2018年   11875篇
  2017年   11951篇
  2016年   12699篇
  2015年   8661篇
  2014年   13884篇
  2013年   35478篇
  2012年   21920篇
  2011年   29000篇
  2010年   23355篇
  2009年   25575篇
  2008年   26366篇
  2007年   26259篇
  2006年   22792篇
  2005年   20326篇
  2004年   18797篇
  2003年   18195篇
  2002年   17696篇
  2001年   17262篇
  2000年   16449篇
  1999年   16305篇
  1998年   38183篇
  1997年   27621篇
  1996年   21397篇
  1995年   16263篇
  1994年   14793篇
  1993年   14335篇
  1992年   11088篇
  1991年   10706篇
  1990年   10600篇
  1989年   10387篇
  1988年   9837篇
  1987年   8837篇
  1986年   8657篇
  1985年   9842篇
  1984年   9095篇
  1983年   8602篇
  1982年   7709篇
  1981年   7998篇
  1980年   7508篇
  1979年   7692篇
  1978年   7512篇
  1977年   8278篇
  1976年   10636篇
  1975年   6775篇
  1974年   6470篇
  1973年   6563篇
  1972年   5539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.
Qin  Yi  Tao  Xianping  Huang  Yu    Jian 《World Wide Web》2019,22(1):1-37
World Wide Web - Rule mechanism has been widely used in many areas, such as databases, artificial intelligent and pervasive computing. In a rule mechanism, rule activation decides which rules are...  相似文献   
6.
7.
The contamination of honey with hepatotoxic pyrrolizidine alkaloids (PAs) is a well-known hazard for food safety. While management strategies and controls of the honey industry aim to reduce the PA levels, uncertainties remain with regard to the safety of regionally produced and marketed honey. In addition, a previous study showed large differences of results obtained after various periods of storage and apparent differences between the analytical results of different laboratories. Therefore, this study aimed at examining these uncertainties by monitoring the impact of storage on the PA and PA N-oxide (PANO) content of two freshly harvested honeys and on possible demixing effects caused by pollen settling. Additionally, three analytical approaches – target analysis with matrix-matched calibration or standard addition and a sum parameter method – were applied for a comparative analysis of 20 honeys harvested in summer 2016. All samples originated from Schleswig-Holstein in Northern Germany where the PA plant Jacobaea vulgaris is currently observed on a massive scale. The results of the time series analyses showed that PANO levels markedly decreased within a few weeks and practically reached the LOD 16 weeks after harvest. Tertiary PAs, by contrast, remained stable and did not increase as a consequence of PANO decrease. The experiments on a putative demixing, which may result in a heterogeneous distribution of PAs/PANOs, revealed that there was no such effect during storage of up to 12 weeks. A comparison of the PA/PANO levels obtained by different analytical approaches showed that in some cases the sum parameter method yielded much higher levels than the target approaches, whereas in other cases, the target analysis with standard addition found higher levels than the other two methods. In summary, the results of this study highlight uncertainties regarding the validity and comparability of analytical results and consequently regarding health risk assessment.  相似文献   
8.
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