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   25105篇
  免费   967篇
  国内免费   35篇
电工技术   331篇
综合类   40篇
化学工业   5721篇
金属工艺   388篇
机械仪表   485篇
建筑科学   1316篇
矿业工程   101篇
能源动力   650篇
轻工业   1928篇
水利工程   234篇
石油天然气   72篇
无线电   1845篇
一般工业技术   4598篇
冶金工业   4637篇
原子能技术   201篇
自动化技术   3560篇
  2023年   222篇
  2022年   364篇
  2021年   578篇
  2020年   345篇
  2019年   434篇
  2018年   550篇
  2017年   469篇
  2016年   637篇
  2015年   564篇
  2014年   759篇
  2013年   1437篇
  2012年   1169篇
  2011年   1526篇
  2010年   1082篇
  2009年   1036篇
  2008年   1162篇
  2007年   1099篇
  2006年   954篇
  2005年   771篇
  2004年   757篇
  2003年   680篇
  2002年   573篇
  2001年   442篇
  2000年   369篇
  1999年   413篇
  1998年   778篇
  1997年   577篇
  1996年   451篇
  1995年   418篇
  1994年   386篇
  1993年   373篇
  1992年   271篇
  1991年   197篇
  1990年   276篇
  1989年   262篇
  1988年   217篇
  1987年   229篇
  1986年   227篇
  1985年   267篇
  1984年   224篇
  1983年   223篇
  1982年   209篇
  1981年   197篇
  1980年   169篇
  1979年   198篇
  1978年   165篇
  1977年   189篇
  1976年   235篇
  1975年   164篇
  1974年   127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.
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.
The separation of iron oxide from banded hematite jasper(BHJ) assaying 47.8% Fe, 25.6% Si O2 and 2.30%Al2O3 using selective magnetic coating was studied. Characterization studies of the low grade ore indicate that besides hematite and goethite,jasper, a microcrystalline form of quartzite, is the major impurity associated with this ore. Beneficiation by conventional magnetic separation technique could yield a magnetic concentrate containing 60.8% Fe with 51% Fe recovery. In order to enhance the recovery of the iron oxide minerals, fine magnetite, colloidal magnetite and oleate colloidal magnetite were used as the coating material. When subjected to magnetic separation, the coated ore produces an iron concentrate containing 60.2% Fe with an enhanced recovery of56%. The AFM studies indicate that the coagulation of hematite particles with the oleate colloidal magnetite facilitates the higher recovery of iron particles from the low grade BHJ iron ore under appropriate conditions.  相似文献   
5.
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   
6.
7.
8.
9.
We demonstrate that alkali-halide salts, particularly potassium bromide, can reduce the photothermal emission (PTE) from single walled carbon nanotubes (SWNT). PTE is a prominent spectral feature in Raman spectroscopy when a near infrared laser is used to analyze a dark colored sample. We subsequently show that trapping salts inside SWNT and coating SWNT with the salt has a more pronounced impact on not only reducing PTE, but also enhancing the intensity of the Raman spectral features. The effect, which we have called nanotube enhanced Raman spectroscopy (NERS), has differences and similarities to the widely studied surface enhanced Raman spectroscopy (SERS).  相似文献   
10.
In advancement of Pyrosil®‐technology a new kind of precursor delivery was developed, build and tested on real substrates. A Lab‐demonstrator was build to demonstrate the resources of the technology.  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