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   3800篇
  免费   146篇
  国内免费   1篇
电工技术   29篇
化学工业   843篇
金属工艺   30篇
机械仪表   68篇
建筑科学   136篇
矿业工程   10篇
能源动力   65篇
轻工业   683篇
水利工程   43篇
石油天然气   9篇
无线电   162篇
一般工业技术   371篇
冶金工业   1145篇
原子能技术   8篇
自动化技术   345篇
  2023年   22篇
  2022年   92篇
  2021年   87篇
  2020年   66篇
  2019年   53篇
  2018年   70篇
  2017年   72篇
  2016年   70篇
  2015年   70篇
  2014年   94篇
  2013年   232篇
  2012年   164篇
  2011年   192篇
  2010年   144篇
  2009年   165篇
  2008年   146篇
  2007年   163篇
  2006年   129篇
  2005年   134篇
  2004年   119篇
  2003年   115篇
  2002年   98篇
  2001年   70篇
  2000年   75篇
  1999年   75篇
  1998年   112篇
  1997年   84篇
  1996年   66篇
  1995年   58篇
  1994年   60篇
  1993年   50篇
  1992年   57篇
  1991年   23篇
  1990年   48篇
  1989年   58篇
  1988年   43篇
  1987年   57篇
  1986年   48篇
  1985年   48篇
  1984年   34篇
  1983年   27篇
  1982年   46篇
  1981年   30篇
  1980年   28篇
  1978年   31篇
  1977年   24篇
  1976年   18篇
  1975年   21篇
  1974年   18篇
  1973年   18篇
排序方式: 共有3947条查询结果,搜索用时 31 毫秒
121.
122.
123.
Trypanosoma rangeli and T. cruzi are both parasitic unicellular species that infect humans. Unlike T. cruzi, the causative agent of Chagas disease, T. rangeli is an infective and non-pathogenic parasite for humans, but pathogenic for vectors from the Rhodnius genus. Because both species can coexist in different hosts and overlap their infective cycles but very little is known about the infection of T. rangeli in mammalian cells, we decided to characterize both the development of this parasite in cell culture and the effect of therapeutic agents with potential trypanocidal action on it. We found that T. rangeli exhibits a cycle of infection in Vero cells similar to that for T. cruzi and that the repurposed drug, 17-AAG, and the natural extract Artemisia sp. essential oil produce a toxic effect on epimastigotes showing a trypanocidal action from the fifth day of culture. Both treatments also affected the infection of trypomastigotes and reduced the capacity of replication of amastigotes of T. rangeli. Since T. cruzi / T. rangeli coinfection cases have been reported, the finding of drugs with potential activity against both species could be significant in the future. Furthermore, studies of susceptibility of both species to drugs could also help to know the different mechanisms of pathogenicity in humans displayed by T. cruzi that are absent in T. rangeli  相似文献   
124.
This paper gives the theoretical setup so that an ecological model, as a particular mathematical model, can be considered a text written in a formal language (mathematics), and therefore, statistical linguistic laws can be applied to obtain information parameters in different semantic levels of the same model. The statistical laws will be useful to: a) compare semantic levels, submodels, and different models mutually; b) prove that information temperature parameter is an indirect measure of meaning: the significance or semantic component of information, opposed to significant, or comprehension, on the part of the observer (modeller) of the model text. We will apply these ideas in two practical examples.  相似文献   
125.
126.
127.
128.
Universal Access in the Information Society - Learning to program is becoming a universally desired ability. Discovering better ways to teach programming and improving existing ones is essential to...  相似文献   
129.
Municipal infrastructure for water supply and delivery often does not reach populations in rural and peri-urban areas. This article examines rainwater harvesting as a means of increasing water security in such areas, through the case of Guachtuq, a peri-urban community outside San Cristóbal, Alta Verapaz, Guatemala. The project team designed a rainwater harvesting system to improve three dimensions of water security: quantity, quality and access. The design was implemented for 12 households and evaluated for its contribution to water security and for the potential of expanding project coverage to the region and beyond. The system has improved water security. Several concerns remain, however, regarding the potential of expanding the project to other households in the region and beyond, including system cost, water quality and the individualization of public responsibility for water security.  相似文献   
130.
A fast and reliable method for anthocyanin extraction and identification by HPLC‐DAD‐ESI/MS‐QTOF was used to analyse the anthocyanin composition of commercial red fruit juices (blackberry, redcurrant and pomegranate), purees (strawberry, cherry and raspberry) and concentrates (elderberry, blueberry and red grape). The anthocyanin profile of black carrot juice is also reported. The extraction and analysis method allowed us to detect and quantify a wide range of individual anthocyanins in a simple and rapid way. Pelargonidin‐3‐glucoside was detected in redcurrant for the first time and petunidin‐3‐galactoside quantified for the first time in blueberries. Considering the health benefits that have been associated with anthocyanin consumption, all these fruit and vegetables processed products could appear as a good source of this group of phytochemical compounds for their direct consumption or their use as ingredients for the design of new food product or food supplements.  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