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   387篇
  免费   10篇
  国内免费   1篇
电工技术   7篇
化学工业   93篇
金属工艺   3篇
机械仪表   6篇
建筑科学   17篇
矿业工程   4篇
能源动力   9篇
轻工业   13篇
水利工程   1篇
无线电   46篇
一般工业技术   68篇
冶金工业   19篇
原子能技术   2篇
自动化技术   110篇
  2023年   5篇
  2022年   4篇
  2021年   9篇
  2020年   8篇
  2019年   10篇
  2018年   7篇
  2017年   8篇
  2016年   15篇
  2015年   12篇
  2014年   17篇
  2013年   35篇
  2012年   19篇
  2011年   44篇
  2010年   20篇
  2009年   22篇
  2008年   19篇
  2007年   16篇
  2006年   17篇
  2005年   11篇
  2004年   15篇
  2003年   8篇
  2002年   7篇
  2001年   2篇
  2000年   7篇
  1999年   2篇
  1998年   5篇
  1997年   4篇
  1996年   4篇
  1995年   7篇
  1994年   5篇
  1993年   2篇
  1992年   4篇
  1991年   1篇
  1990年   4篇
  1989年   4篇
  1987年   4篇
  1986年   1篇
  1985年   3篇
  1983年   1篇
  1982年   4篇
  1980年   1篇
  1979年   1篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
排序方式: 共有398条查询结果,搜索用时 15 毫秒
1.
2.
The development of visualizing tools to monitor unsaturated moisture flow in cement-based materials is of great importance, as most degradation processes in cement-based materials are connected to and take place in the presence moisture. This paper investigates the ability of electrical capacitance tomography (ECT) to image two-dimensional (2D) unsaturated moisture flow in cement-based materials. In ECT, the electrical permittivity distribution within an object is reconstructed based on measured capacitances between electrodes attached on the object’s surface. In a series of experiments, mortar specimens with and without discrete cracks were imaged with ECT during a 2D moisture ingress. The results show that ECT is able to monitor the evolution of the moisture flow, and to approximate the shape and position of the moisture front. These findings indicate that ECT is a viable method for monitoring and visualizing 2D unsaturated moisture flow in cement-based materials in the presence and absence of discrete cracks.  相似文献   
3.
Carbene‐metal‐amides (CMAs) are a promising family of donor–bridge–acceptor molecular charge‐transfer (CT) emitters for organic light‐emitting diodes. A universal approach is demonstrated to tune the energy of their CT emission. A blueshift of up to 210 meV is achievable in solid state via dilution in a polar host matrix. The origin of this shift has two components: constraint of thermally‐activated triplet diffusion, and electrostatic interactions between guest and polar host. This allows the emission of mid‐green CMA archetypes to be tuned to sky blue without chemical modifications. Monte‐Carlo simulations based on a Marcus‐type transfer integral successfully reproduce the concentration‐ and temperature‐dependent triplet diffusion process, revealing a substantial shift in the ensemble density of states in polar hosts. In gold‐bridged CMAs, this shift does not lead to a significant change in luminescence lifetime, thermal activation energy, reorganization energy, or intersystem crossing rate. These discoveries offer new insight into coupling between the singlet and triplet manifolds in CMA materials, revealing a dominant interaction between states of CT character. The same approach is employed using materials which have been chemically modified to alter the energy of their CT state directly, shifting the emission of sky‐blue chromophores into the practical blue range.  相似文献   
4.
Streptomyces hygroscopicus is a natural producer of geldanamycin. Mutasynthetic supplementation of an AHBA‐blocked mutant with all possible monofluoro 3‐aminobenzoic acids provided new fluorogeldanamycins. These showed strong antiproliferative activity and inhibitory effects on human heat shock protein Hsp90. Binding to Hsp90 in the low nanomolar range was determined from molecular modelling, AFM analysis and by calorimetric studies.  相似文献   
5.
6.
7.
The effect of austenite pancaking in the non-recrystallization regime on microstructure and texture evolution and thereby on bendability was investigated in an ultrahigh-strength strip steel with a martensitic-bainitic microstructure. The results indicate that an increase in rolling reduction (R tot) below the non-recrystallization temperature, which improves the strength and toughness properties, increases the intensities of the ~{554}〈225〉 α and ~{112}〈110〉 α texture components along the strip centerline and of the ~{112}〈111〉 α component at the surface region. Even with the highest R tot of 79 pct, the bendability along the rolling direction was good, but the preferred alignment of rod-shaped MA constituents along the rolling direction led to a dramatic decrease in the bendability transverse to the rolling direction, with severe cracking occurring even at small bending angles. The early cracking is attributed to localization of the strain in narrow shear bands. It is concluded that the Rtot value has to be limited to guarantee successful bendability.  相似文献   
8.
The purpose of this paper is to discuss the requirements and challenges of pyrolysis oil's transportation in Finland. Pyrolysis oil is a new type of renewable liquid fuel that can be utilised in applications such as heat and electricity production. It has never been transported on a large scale in Finland. Possible options are transport by road, rail and waterway. The most significant requirements in its transportation are created by acidity and high density of pyrolysis oil, which impose requirements for the materials and transport equipment. The study described here shows that constant domestic transportation of pyrolysis oil is most reasonably operated with tank trucks. Rail-based transport may have potential for domestic fixed routes, and transport by water could be utilised in exporting. All transportation methods have limitations and advantages relative to each other. Ultimately, the production site and end-user's locations will determine the most suitable transport method.  相似文献   
9.
A method for measuring continuously the inherent optical properties of water together with the salinity and the temperature values was developed and tested at the Division of Geophysics, University of Helsinki. The flow‐through system operates from a moving boat and has been used to collect parameters for optical modelling, coastal zone and inland water studies and to track the path of the fresh water spreading into sea areas. The system was also used in Lake Vänern, Sweden, to calculate the radiance reflectance, R r, and total back‐scattering efficiency, b b eff, along a transect. An example from the Gulf of Finland is presented, which shows how the spectral behaviour of light changes when moving away from a fresh water source. Data collected from the River Kymijoki estuary showed that the details in a rapidly changing environment were strongly smoothed in a Moderate Resolution Imaging Spectroradiometer (MODIS) data image. The correlation for continuously measured scattering values and MODIS channel 1 data varied between 0.70 and 0.85, n?=?126. Flow‐through measurement datasets can be used to obtain representative sites for vertical profiles or calibration measurements.  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