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   256815篇
  免费   2118篇
  国内免费   346篇
电工技术   4372篇
综合类   207篇
化学工业   41559篇
金属工艺   15561篇
机械仪表   10565篇
建筑科学   4426篇
矿业工程   3911篇
能源动力   4012篇
轻工业   10158篇
水利工程   4247篇
石油天然气   13356篇
武器工业   40篇
无线电   20853篇
一般工业技术   64450篇
冶金工业   32736篇
原子能技术   11237篇
自动化技术   17589篇
  2021年   3065篇
  2019年   2958篇
  2018年   5836篇
  2017年   6121篇
  2016年   6556篇
  2015年   3415篇
  2014年   5803篇
  2013年   10724篇
  2012年   7898篇
  2011年   9333篇
  2010年   7749篇
  2009年   8621篇
  2008年   8563篇
  2007年   8224篇
  2006年   6632篇
  2005年   5730篇
  2004年   5580篇
  2003年   5343篇
  2002年   5174篇
  2001年   4983篇
  2000年   5063篇
  1999年   4351篇
  1998年   7271篇
  1997年   5919篇
  1996年   4444篇
  1995年   3666篇
  1994年   3429篇
  1993年   3629篇
  1992年   3226篇
  1991年   3368篇
  1990年   3497篇
  1989年   3374篇
  1988年   3274篇
  1987年   3264篇
  1986年   3161篇
  1985年   3329篇
  1984年   3261篇
  1983年   3157篇
  1982年   2998篇
  1981年   3050篇
  1980年   3080篇
  1979年   3268篇
  1978年   3504篇
  1977年   3466篇
  1976年   3921篇
  1975年   3215篇
  1974年   3299篇
  1973年   3348篇
  1972年   2992篇
  1971年   2760篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
This paper proposes a reading of the cultural and social aspects associated with sundry notions of territory through Spanish photography at the end of the twentieth century and the beginning of the twenty-first. An analysis of a series of case studies reveals a new awareness of the common space through the concept of trace, being understood beyond the material imprint, as it falls under the influence of the cultural aspects that clarify the account of the conflict and consciousness of the suburbs and peripheries. Contemporary ruins arising from unbridled urban growth, or the invisible wounds associated with certain places, converge in a series of images that have their own tradition in the conceptual experiments of the 70s and the aesthetics of the “non-site” displayed in the 90s. As background, the economic and political avatars of recent years in Spain – also linked to a global crisis – are manifested in a series of photographic musings whose images portray the scenarios of a premature ruin linked to property speculation and the traces of a collective memory.  相似文献   
2.
ABSTRACT

Extreme natural events require effective emergency procedures to minimize adverse effects on a region’s population and economy. Such procedures typically involve the effort of several different teams of first responders (e.g., fire fighters, public administrations, police departments, utility companies), hence coordination is fundamental to the effectiveness of the response to the emergency that must be supported with adequate infrastructures. Nonetheless, first responders often rely on manual processes, in the life cycle of extreme events, which do not change consistently with the type of shock or affected population. The aim of this paper is to present a technology transfer process to improve both the emergency alert process and the knowledge of disaster-type safety procedures through the implementation of a proposed platform. We also highlight a pilot application on a post-disaster case study—the province of L’Aquila (Abruzzi) in Italy.  相似文献   
3.
Abstract

In the present work, we compare the structure and transport properties of carbon nanohorns (CNHs) synthesized by arc evaporation of graphite alone and with the addition of some portion of toluene. The materials have been investigated using transmission electron microscopy, Raman and infrared spectroscopies, thermogravimetric and BET analyses. The addition of a small amount of toluene during the evaporation of graphitic rod increases the length of CNHs, affects their hierarchical arrangement in aggregates and results in surface functionalization. All these features significantly enhance the conductivity of CNHs obtained with toluene additive in comparison with the pristine CNHs.  相似文献   
4.
5.
6.
The gel-forming ability of myofibrillar protein (MP) is highly correlated with the characteristics of emulsified meat products. Incorporation of Agaricus bisporus (Ab) powder into MP gels may enhance its gel properties to facilitate the development of a novel and safe meat product. Therefore, this study investigated the effects of Ab powder on gel strength, water holding capacity (WHC), texture, rheological behaviour, LF-NMR spin–spin relaxation (T2), microstructure and protein secondary structure of the MP gel system. The results indicated that the gel strength, WHC, G' value and G" value were significantly improved when the addition of Ab powder increased from 0% to 6% (P < 0.05). Meanwhile, the T2 relaxation time was shortened, and free water was transformed into immobilised water. The texture of the gel was improved when 1%–4% Ab powder was added compared to the control. Furthermore, Ab filled in the gel network and promoted the unfolding of MP α-helix and the formation of MP β-sheet during the thermal denaturation of MP, leading to a dense aggregated network structure. The study suggested that Ab could be a promising ingredient in improving chicken MP's gel properties and developing fat-reduced meat products.  相似文献   
7.
8.
9.
Search for conditions of conservation of fast ionic transport (FIT) in nanosystems of advanced superionic conductors (ASIC)[1-4] and synthesis of new types of device thin-film heterostructures on this basis is a fundamental scientific problem. ASICs (α-AgI, solid electrolytes of the family RbAg4I5, etc. ) are crystals with a record high level of ionic conductivity and a low value of activation energy E~0. 1 eV.  相似文献   
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