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   55676篇
  免费   2192篇
  国内免费   163篇
电工技术   795篇
综合类   272篇
化学工业   10895篇
金属工艺   1242篇
机械仪表   1157篇
建筑科学   2255篇
矿业工程   246篇
能源动力   1163篇
轻工业   6547篇
水利工程   451篇
石油天然气   205篇
武器工业   10篇
无线电   3333篇
一般工业技术   9905篇
冶金工业   12037篇
原子能技术   449篇
自动化技术   7069篇
  2023年   497篇
  2022年   672篇
  2021年   1190篇
  2020年   850篇
  2019年   886篇
  2018年   1386篇
  2017年   1225篇
  2016年   1485篇
  2015年   1315篇
  2014年   1651篇
  2013年   3135篇
  2012年   2441篇
  2011年   2856篇
  2010年   2230篇
  2009年   2126篇
  2008年   2381篇
  2007年   2255篇
  2006年   1793篇
  2005年   1446篇
  2004年   1261篇
  2003年   1155篇
  2002年   1040篇
  2001年   836篇
  2000年   755篇
  1999年   906篇
  1998年   3142篇
  1997年   2008篇
  1996年   1471篇
  1995年   1046篇
  1994年   894篇
  1993年   838篇
  1992年   472篇
  1991年   407篇
  1990年   441篇
  1989年   432篇
  1988年   394篇
  1987年   404篇
  1986年   395篇
  1985年   508篇
  1984年   427篇
  1983年   401篇
  1982年   348篇
  1981年   399篇
  1980年   370篇
  1979年   336篇
  1978年   287篇
  1977年   420篇
  1976年   736篇
  1975年   268篇
  1973年   238篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Abstract

This article discusses different approaches to materiality and material expressions of cultural identity in contemporary Bahrain, a small Arab Gulf state. Various Islamic traditions have different understandings of materiality and its ontological qualities. In the contemporary Gulf this difference is often understood as a sectarian difference between Sunni and Shia Muslims, a division that has gained increasing political importance in recent years. In this article I discuss how these traditions view materiality in religion, in particular focusing on the role of material mediation for Shia Muslims, exemplified by the use and meaning of the turba prayer stone. With this as a point of departure I discuss two other forms of materiality—political graffiti and martyr images—that in the wake of the uprising in 2011 have also been imbued with sectarian meanings, but where this is less clear. I therefore argue that vernacular understandings of material culture show ambiguous identifications that challenge the clear dichotomies with which people—locally and analytically —often operate.  相似文献   
2.
Cable‐shaped supercapacitors (SCs) have recently aroused significant attention due to their attractive properties such as small size, lightweight, and bendability. Current cable‐shaped SCs have symmetric device configuration. However, if an asymmetric design is used in cable‐shaped supercapacitors, they would become more attractive due to broader cell operation voltages, which results in higher energy densities. Here, a novel coil‐type asymmetric supercapacitor electrical cable (CASEC) is reported with enhanced cell operation voltage and extraordinary mechanical‐electrochemical stability. The CASECs show excellent charge–discharge profiles, extraordinary rate capability (95.4%), high energy density (0.85 mWh cm−3), remarkable flexibility and bendability, and superior bending cycle stability (≈93.0% after 4000 cycles at different bending states). In addition, the CASECs not only exhibit the capability to store energy but also to transmit electricity simultaneously and independently. The integrated electrical conduction and storage capability of CASECS offer many potential applications in solar energy storage and electronic gadgets.  相似文献   
3.
4.
5.
6.
7.
While qualitative studies have identified chlorogenic acids in antioxidant extracts, particularly ethyl acetate‐derived extracts, of Taraxacum officinale, quantitative analysis of these phenolic compounds remains largely unreported for this species. In this study, bioactivity‐guided fractionation of an antioxidant crude ethyl acetate extract (DPPH = 295.481 ± 0.955 mg TE g?1 extract) from T. officinale root resulted in a number of reverse‐phase fractions that demonstrated high antioxidant activity (DPPH = 1058.733–1312.136 mg TE g?1 extract), stronger than that of the synthetic antioxidant Trolox®. UPLC‐MS/MS screening of these fractions for the presence of selected mono‐ and di‐caffeoylquinic acids revealed large quantities of 1,5‐dicaffeoylquinic acid present in several fractions (853.052–907.324 μg mg?1), respectively. Due to the antioxidant potency and high levels of 1,5‐dicaffeoylquinic acid observed in these fractions, it was concluded that specifically this chlorogenic acid derivative is a major contributor to the antioxidant efficacy of dandelion root.  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