全文获取类型
收费全文 | 49819篇 |
免费 | 3951篇 |
国内免费 | 1913篇 |
专业分类
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 |
出版年
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.
3.
4.
Yujie Chen Yiping Song Zhen Zhang Yali Chen Qiliang Deng Shuo Wang 《Advanced functional materials》2021,31(41):2104885
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.
Giorgio Valabrega Giulia Scotto Valentina Tuninetti Arianna Pani Francesco Scaglione 《International journal of molecular sciences》2021,22(8)
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.
7.
Karolina Storesund Francine Amon Anne Steen‐Hansen Shayesteh Haghighatpanah Ida Larsson 《火与材料》2021,45(1):181-190
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.
Norfariza Jamaluddin David C. Stuckey Arbakariya B. Ariff 《Critical reviews in food science and nutrition》2018,58(14):2453-2465
ABSTRACTBacteriocin 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