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   345624篇
  免费   5783篇
  国内免费   753篇
电工技术   6753篇
综合类   646篇
化学工业   55058篇
金属工艺   11086篇
机械仪表   9577篇
建筑科学   9830篇
矿业工程   1059篇
能源动力   9362篇
轻工业   34778篇
水利工程   2829篇
石油天然气   3750篇
武器工业   8篇
无线电   42169篇
一般工业技术   66176篇
冶金工业   60855篇
原子能技术   5736篇
自动化技术   32488篇
  2021年   3123篇
  2020年   2246篇
  2019年   2795篇
  2018年   4620篇
  2017年   4422篇
  2016年   4726篇
  2015年   3576篇
  2014年   5708篇
  2013年   16781篇
  2012年   9113篇
  2011年   12352篇
  2010年   9618篇
  2009年   10713篇
  2008年   11389篇
  2007年   11259篇
  2006年   9895篇
  2005年   8958篇
  2004年   8746篇
  2003年   8418篇
  2002年   8193篇
  2001年   8206篇
  2000年   7755篇
  1999年   8077篇
  1998年   18430篇
  1997年   13465篇
  1996年   10603篇
  1995年   8357篇
  1994年   7624篇
  1993年   7298篇
  1992年   5609篇
  1991年   5306篇
  1990年   5225篇
  1989年   5055篇
  1988年   4906篇
  1987年   4136篇
  1986年   4235篇
  1985年   5053篇
  1984年   4588篇
  1983年   4282篇
  1982年   3864篇
  1981年   4026篇
  1980年   3680篇
  1979年   3655篇
  1978年   3438篇
  1977年   4027篇
  1976年   5096篇
  1975年   2973篇
  1974年   2807篇
  1973年   2819篇
  1972年   2320篇
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
1.
One specific class of non-linear evolution equations, known as the Tzitzéica-type equations, has received great attention from a group of researchers involved in non-linear science. In this article, new exact solutions of the Tzitzéica-type equations arising in non-linear optics, including the Tzitzéica, Dodd–Bullough–Mikhailov and Tzitzéica–Dodd–Bullough equations, are obtained using the expa function method. The integration technique actually suggests a useful and reliable method to extract new exact solutions of a wide range of non-linear evolution equations.  相似文献   
2.
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   
3.
4.
5.
6.
7.
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   
8.
Pinhão seed is an unconventional source of starch and the pines grow up in native forests of southern Latin America. In this study, pinhão starch was adjusted at 15, 20 and 25% moisture content and heated to 100, 110 and 120 °C for 1 h. A decrease in λ max (starch/iodine complex) was observed as a result of increase in temperature and moisture content of HMT. The ratio of crystalline to amorphous phase in pinhão starch was determined via Fourier transform infra red by taking 1045/1022 band ratio. A decrease in crystallinity occurred as a result of HMT. Polarised light microscopy indicated a loss of birefringence of starch granules under 120 °C at 25% moisture content. Granule size distribution was further confirmed via scanning electron microscopy which showed the HMT effects. These results increased the understanding on molecular and structural properties of HMT pinhão starch and broadened its food and nonfood industrial applications.  相似文献   
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