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   1318篇
  免费   120篇
电工技术   9篇
化学工业   505篇
金属工艺   7篇
机械仪表   28篇
建筑科学   38篇
矿业工程   1篇
能源动力   43篇
轻工业   379篇
水利工程   3篇
石油天然气   4篇
无线电   72篇
一般工业技术   197篇
冶金工业   36篇
原子能技术   4篇
自动化技术   112篇
  2024年   3篇
  2023年   14篇
  2022年   101篇
  2021年   103篇
  2020年   48篇
  2019年   50篇
  2018年   51篇
  2017年   56篇
  2016年   50篇
  2015年   41篇
  2014年   58篇
  2013年   87篇
  2012年   81篇
  2011年   90篇
  2010年   89篇
  2009年   72篇
  2008年   68篇
  2007年   47篇
  2006年   44篇
  2005年   29篇
  2004年   30篇
  2003年   26篇
  2002年   28篇
  2001年   13篇
  2000年   7篇
  1999年   11篇
  1998年   29篇
  1997年   15篇
  1996年   15篇
  1995年   11篇
  1994年   5篇
  1993年   9篇
  1992年   7篇
  1990年   1篇
  1989年   4篇
  1988年   1篇
  1987年   4篇
  1986年   1篇
  1985年   3篇
  1984年   9篇
  1983年   4篇
  1982年   5篇
  1981年   2篇
  1980年   4篇
  1979年   2篇
  1978年   4篇
  1977年   2篇
  1973年   1篇
  1962年   1篇
  1961年   1篇
排序方式: 共有1438条查询结果,搜索用时 15 毫秒
41.
With the aim to develop natural preservatives displaying also chemopreventive activity, different Commiphora myrrha (Nees) Engl. extracts were studied. Myrrh essential oils, obtained by steam distillation and microwave‐assisted hydrodistillation, and several other extracts, obtained by sequential procedures with petroleum ether (PE), ethanol, ethyl acetate and butanol, have been screened for their antioxidant (DPPH· scavenging assay) and antiproliferative activity (on both nontumour and colon cancer cell lines) without previous purification. Considering that the colon cancer cell lines were more sensitive to PE and ethanol extracts, the latter of which showed the highest antioxidant activity (EC50 = 0.160 ± 0.008 mg mL?1), both have been selected for further antibacterial/antifungal activity tests using an antimicrobial diffusion test and a growth inhibition test on salads. Results showed that the ethanol extract possessed the higher antibacterial and antifungal activity. Compared to untreated product, fresh‐cut salads treated with these two myrrh extracts displayed a significant lower bacterial growth. Although further investigation is required, these promising results offer hints as how to improve the shelf life of fresh‐cut salad.  相似文献   
42.
This article describes the preparation of thin films of conjugated polymers which can enhance their specific electrical conductivity by several orders of magnitude by changing their state from insulating to conducting materials. The examined polymers, i.e., a polyacetylenic and a polythiophenic derivative, are functionalized with thioalkylic side chains and are soluble in common organic solvents from which they lead to thick homogeneous films. The films can be deposited on different substrates, either rigid or flexible, and can be easily exposed to laser radiation to make them conductive. The process is irreversible, and the final conductivity is stable over time, even in the presence of high temperatures (up to 180 °C), moisture, and air. The high stability of treated samples, easy polymer synthesis and quick and inexpensive suitably tailored laser tracing procedure make these materials very promising for applications in organic electronics and in the development of new electronic circuitry.  相似文献   
43.
44.
Hyperaemia is an excess of blood in a tissue that causes the appearance of an unusual red hue in the affected area. It is a common occurrence in the bulbar conjunctiva, where it can be related to multiple pathologies, such as conjunctivitis or dry eye syndrome. Specialists grade hyperaemia by means of a tedious, subjective, non-repeatable and time-consuming process. These drawbacks can be solved with the automatisation of the process by means of image processing techniques. The automatic segmentation of the conjunctiva is an important part of the process, as it ensures the absence of noise in posterior stages of the methodology. However, there are several issues of illumination and focus in the input videos that difficult the process. In this work, several segmentation algorithms are proposed and compared in order to obtain an accurate location of the bulbar conjunctiva.  相似文献   
45.
46.
One of the main aims in agriculture is to guarantee soil wellness, which is a fundamental requirement to produce high-quality crops with high yields. Focused on this aim, periodical administrations of nutrients or phytostrengtheners are often necessary. The most relevant disadvantages of these administrations are the high dosage number required and the low availability of the substance within the soil. For these reasons, a crucial goal to increase the economic and environmental sustainability of the cultivation process is to reduce the dosage number, which can be obtained increasing the active substance availability in the soil. A granular hydroxypropyl methylcellulose (HPMC) matrix, produced using the wet granulation process, was used to encapsulate a phytostrengthener and to guarantee its controlled release. The granular product was characterized in terms of granules properties and phytostrengtheners leaching within the soil. The results showed good flowability and mechanical properties of the granules as well as the possibility to reduce the product leaching with the phytostrengtheners encapsulation in the HPMC matrices.  相似文献   
47.
One of the most common effects among aphasia patients is the difficulty to recall names or words. Typically, word retrieval problems can be treated through word naming therapeutic exercises. In fact, the frequency and the intensity of speech therapy are key factors in the recovery of lost communication functionalities. In this sense, speech and language technology can have a relevant contribution in the development of automatic therapy methods. In this work, we present an on-line system designed to behave as a virtual therapist incorporating automatic speech recognition technology that permits aphasia patients to perform word naming training exercises. We focus on the study of the automatic word naming detector module and on its utility for both global evaluation and treatment. For that purpose, a database consisting of word naming therapy sessions of aphasic Portuguese native speakers has been collected. In spite of the different patient characteristics and speech quality conditions of the collected data, encouraging results have been obtained thanks to a calibration method that makes use of the patients’ word naming ability to automatically adapt to the patients’ speech particularities.  相似文献   
48.
49.
50.
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