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   298795篇
  免费   4857篇
  国内免费   1020篇
电工技术   5501篇
综合类   460篇
化学工业   45259篇
金属工艺   10533篇
机械仪表   8518篇
建筑科学   7948篇
矿业工程   1109篇
能源动力   8213篇
轻工业   25855篇
水利工程   2599篇
石油天然气   3417篇
武器工业   25篇
无线电   37196篇
一般工业技术   58198篇
冶金工业   58370篇
原子能技术   5392篇
自动化技术   26079篇
  2022年   2002篇
  2021年   3216篇
  2020年   2310篇
  2019年   2686篇
  2018年   4514篇
  2017年   4374篇
  2016年   4741篇
  2015年   3399篇
  2014年   5410篇
  2013年   14267篇
  2012年   8349篇
  2011年   11032篇
  2010年   8832篇
  2009年   9725篇
  2008年   10486篇
  2007年   10281篇
  2006年   8898篇
  2005年   7772篇
  2004年   7374篇
  2003年   7519篇
  2002年   6906篇
  2001年   7167篇
  2000年   6560篇
  1999年   7117篇
  1998年   18842篇
  1997年   12971篇
  1996年   9922篇
  1995年   7413篇
  1994年   6599篇
  1993年   6511篇
  1992年   4533篇
  1991年   4318篇
  1990年   4214篇
  1989年   4011篇
  1988年   3854篇
  1987年   3333篇
  1986年   3258篇
  1985年   3617篇
  1984年   3281篇
  1983年   3158篇
  1982年   2918篇
  1981年   2845篇
  1980年   2756篇
  1979年   2563篇
  1978年   2336篇
  1977年   2949篇
  1976年   4164篇
  1975年   1978篇
  1974年   1900篇
  1973年   1856篇
排序方式: 共有10000条查询结果,搜索用时 0 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.
A layer-by-layer analysis of the structures, the phase compositions, and the defect substructures of differentially hardened rails has been carried by optical and transmission electron microscopy. It is found that the material volume of the rail head fillet is cooled faster than the volume located along the central axis.  相似文献   
3.
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   
4.
We explore the possibility of characterizing sperm cells without the need to stain them using spectral and fluorescence lifetime analyses after multi-photon excitation in an insect model. The autofluorescence emission spectrum of sperm of the common bedbug, Cimex lectularius, was consistent with the presence of flavins and NAD(P)H. The mean fluorescence lifetimes showed smaller variation in sperm extracted from the male (tau m, τm = 1.54–1.84 ns) than in that extracted from the female sperm storage organ (tau m, τm = 1.26–2.00 ns). The fluorescence lifetime histograms revealed four peaks. These peaks (0.18, 0.92, 2.50 and 3.80 ns) suggest the presence of NAD(P)H and flavins and show that sperm metabolism can be characterized using fluorescence lifetime imaging. The difference in fluorescence lifetime variation between the sexes is consistent with the notion that female animals alter the metabolism of sperm cells during storage. It is not consistent, however, with the idea that sperm metabolism represents a sexually selected character that provides females with information about the male genotype.  相似文献   
5.
6.
7.
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