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   49819篇
  免费   3951篇
  国内免费   1913篇
电工技术   2247篇
技术理论   8篇
综合类   3818篇
化学工业   4364篇
金属工艺   604篇
机械仪表   1488篇
建筑科学   6771篇
矿业工程   3414篇
能源动力   1277篇
轻工业   13540篇
水利工程   3029篇
石油天然气   2332篇
武器工业   400篇
无线电   1155篇
一般工业技术   4193篇
冶金工业   2361篇
原子能技术   1114篇
自动化技术   3568篇
  2024年   253篇
  2023年   770篇
  2022年   1609篇
  2021年   2119篇
  2020年   2024篇
  2019年   1610篇
  2018年   1527篇
  2017年   1581篇
  2016年   1888篇
  2015年   1960篇
  2014年   3812篇
  2013年   3465篇
  2012年   4066篇
  2011年   3876篇
  2010年   2886篇
  2009年   2743篇
  2008年   2405篇
  2007年   2979篇
  2006年   2734篇
  2005年   2210篇
  2004年   1755篇
  2003年   1561篇
  2002年   1228篇
  2001年   881篇
  2000年   721篇
  1999年   576篇
  1998年   413篇
  1997年   369篇
  1996年   236篇
  1995年   229篇
  1994年   186篇
  1993年   166篇
  1992年   133篇
  1991年   91篇
  1990年   78篇
  1989年   64篇
  1988年   58篇
  1987年   45篇
  1986年   56篇
  1985年   51篇
  1984年   41篇
  1983年   29篇
  1982年   22篇
  1980年   15篇
  1966年   11篇
  1964年   17篇
  1960年   9篇
  1959年   16篇
  1957年   10篇
  1955年   14篇
排序方式: 共有10000条查询结果,搜索用时 22 毫秒
1.
燕麦为西藏自治区典型牧草之一,由于种植区地域辽阔,灌溉试验结果受限,西藏燕麦主要种植区的灌溉定额尚不明确。本文在西藏燕麦主要种植区内选取28个典型站点进行资料收集,遵循农业气候相似原则进行区域划分,基于水量平衡法揭示了西藏燕麦主要种植区灌溉定额的空间分布特征,并根据统计学原理分析了其影响因素。研究表明:燕麦主要种植区的灌溉定额呈由西藏中部至东部呈现先递增后递减的趋势,50%水文年下的燕麦灌溉定额在56~265 mm之间变化。降雨量是影响研究区内燕麦灌溉定额的主要因素(R2为0.515),ET0次之(R2为0.152);其它气象因素中,日照时数对研究区燕麦灌溉定额影响较大(R2为0.462),且呈正相关关系;相对湿度对燕麦灌溉定额影响较小。西藏燕麦主要种植区的灌溉定额及其空间分布可为西藏自治区灌溉用水管理提供支撑。  相似文献   
2.
挥发酸的控制是荔枝酒的生产过程中的重要技术瓶颈,发酵过程易造成荔枝果酒挥  相似文献   
3.
4.
Various products, including foods and pharmaceuticals, are sensitive to temperature fluctuations. Thus, temperature monitoring during production, transportation, and storage is critical. Facile indicators are required to monitor temperature conditions via color changes in real time. This study aimed to prepare and apply thiol-functionalized covalent organic frameworks (COFs) as a novel indicator for monitoring thermal history and temperature abuse. The COFs underwent obvious color changes from bright yellow to purple after exposure to different temperatures for varying durations. The reaction kinetics are analyzed under isothermal conditions, which reveal that the order of reaction rates is k−20°C < k4°C < k20°C < k35°C < k55°C. The activation energy (Ea) of the COFs is calculated using the Arrhenius equation as 50.71 kJ moL−1. The COFs are capable of sensitive color changes and offer a broad temperature tracking range, thereby demonstrating their application potential for the monitoring of temperature and time exposure history during production, transportation, and storage. This excellent performance thermal history indicator also shows promise for expanding the application field of COFs.  相似文献   
5.
Poly(ADP-ribose) polymerases (PARP) are proteins responsible for DNA damage detection and signal transduction. PARP inhibitors (PARPi) are able to interact with the binding site for PARP cofactor (NAD+) and trapping PARP on the DNA. In this way, they inhibit single-strand DNA damage repair. These drugs have been approved in recent years for the treatment of ovarian cancer. Although they share some similarities, from the point of view of the chemical structure and pharmacodynamic, pharmacokinetic properties, these drugs also have some substantial differences. These differences may underlie the different safety profiles and activity of PARPi.  相似文献   
6.
开展爆破工程安全评价可有效地减少各种危险和有害因素 ,减少爆破事故的发生 ,大型或特殊爆破工程均应进行安全评价。本文提出了对爆破工程开展安全评价的设想 ,并对爆破工程安全评价的内容和方法进行了探讨。文中指出 :根据爆破工程的特点 ,可采用事故树分析和预先危险性分析等方法进行爆破工程的安全评价  相似文献   
7.
The aim of this exploratory study has been to investigate the fire properties and environmental aspects of different upholstery material combinations, mainly for domestic applications. An analysis of the sustainability and circularity of selected textiles, along with lifecycle assessment, is used to qualitatively evaluate materials from an environmental perspective. The cone calorimeter was the primary tool used to screen 20 different material combinations from a fire performance perspective. It was found that textile covers of conventional fibres such as wool, cotton and polyester, can be improved by blending them with fire resistant speciality fibres. A new three‐dimensional web structure has been examined as an alternative padding material, showing preliminary promising fire properties with regard to ignition time, heat release rates and smoke production.  相似文献   
8.
9.
10.
ABSTRACT

Bacteriocin is a proteinaceous biomolecule produced by bacteria (both Gram-positive and Gram-negative) that exhibits antimicrobial activity against closely related species, and food-borne pathogens. It has recently gained importance and attracted the attention of several researchers looking to produce it from various substrates and bacterial strains. This ushers in a new era of food preservation where the use of bacteriocin in food products will be an alternative to chemical preservatives, and heat treatment which are understood to cause unwanted side effects, and reduce sensory and nutritional quality. However, this new market depends on the success of novel downstream separation schemes from various types of crude feedstocks which are both effective and economic. This review focuses on the downstream separation of bacteriocin from various sources using both conventional and novel techniques. Finally, recommendations for future interesting areas of research that need to be pursued are highlighted.  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