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   1319篇
  免费   68篇
  国内免费   20篇
电工技术   18篇
综合类   4篇
化学工业   343篇
金属工艺   37篇
机械仪表   36篇
建筑科学   27篇
能源动力   51篇
轻工业   56篇
水利工程   2篇
无线电   250篇
一般工业技术   239篇
冶金工业   103篇
原子能技术   2篇
自动化技术   239篇
  2023年   11篇
  2022年   32篇
  2021年   39篇
  2020年   18篇
  2019年   26篇
  2018年   33篇
  2017年   32篇
  2016年   38篇
  2015年   35篇
  2014年   72篇
  2013年   116篇
  2012年   65篇
  2011年   81篇
  2010年   72篇
  2009年   86篇
  2008年   72篇
  2007年   71篇
  2006年   58篇
  2005年   42篇
  2004年   39篇
  2003年   37篇
  2002年   34篇
  2001年   22篇
  2000年   21篇
  1999年   16篇
  1998年   48篇
  1997年   29篇
  1996年   19篇
  1995年   17篇
  1994年   16篇
  1993年   13篇
  1992年   5篇
  1991年   7篇
  1990年   3篇
  1989年   10篇
  1988年   7篇
  1986年   5篇
  1985年   9篇
  1984年   9篇
  1983年   3篇
  1982年   6篇
  1981年   4篇
  1980年   2篇
  1979年   4篇
  1978年   2篇
  1977年   3篇
  1976年   3篇
  1975年   3篇
  1974年   3篇
  1970年   2篇
排序方式: 共有1407条查询结果,搜索用时 15 毫秒
101.
Light‐emitting diodes (LEDs) have the advantage of controllable light colors and provide the optimal lighting quality against various color attributes required in different environments. However, from the humanized design point of view, beside satisfying physical demands of people, it is also important to achieve satisfaction. With a good match between the LED lighting equipment and ambient colors, the space imagery that complies with psychological needs of human beings can be found. This is expected to become a new market direction for future lighting. In this study, the LED light source feature of adjustable correlated color temperature is used to match wall colors of typical commercial spaces and for the investigation and analysis of the impact of colors of light sources and environments on human beings. The measures of mental and subjective feelings of a group of people under various circumstances have also been investigated. Multivariate analysis of variance has been conducted on three color temperatures of light sources, six wall colors, and measures of five emotion adjectives, and the correlation between these three variables has been further investigated. © 2014 Wiley Periodicals, Inc. Col Res Appl, 41, 72–84, 2016  相似文献   
102.
103.
In many RFID applications, the reader repeatedly identifies the same staying tags. Existing anti-collision protocols can rapidly identify the staying tags by remembering the order in which the tags were recognized in the previous identification process. This paper proposes a novel protocol, dynamic blocking adaptive binary splitting (DBA), based on the blocking mechanism, which prevents the newly-arriving tags from colliding with the staying tags. Moreover, DBA utilizes a dynamic condensation technique to reduce the number of idle slots produced when recognized tags leave. Following the condensation process, multiple staying tags may be required to share the same slot, and thus may cause collisions among them. Accordingly, an efficient ordering binary tree mechanism is proposed to split the collided tags deterministically according to the order in which they were recognized. The analytical and simulation results show that DBA consistently outperforms previous algorithms in all of the considered environments.  相似文献   
104.
Excitation-emission matrix (EEM) fluorescence spectroscopy is a noninvasive method for tissue diagnosis and has become important in clinical use. However, the intrinsic characterization of EEM fluorescence remains unclear. Photobleaching and the complexity of the chemical compounds make it difficult to distinguish individual compounds due to overlapping features. Conventional studies use principal component analysis (PCA) for EEM fluorescence analysis, and the relationship between the EEM features extracted by PCA and diseases has been examined. The spectral features of different tissue constituents are not fully separable or clearly defined. Recently, a non-stationary method called multi-dimensional ensemble empirical mode decomposition (MEEMD) was introduced; this method can extract the intrinsic oscillations on multiple spatial scales without loss of information. The aim of this study was to propose a fluorescence spectroscopy system for EEM measurements and to describe a method for extracting the intrinsic characteristics of EEM by MEEMD. The results indicate that, although PCA provides the principal factor for the spectral features associated with chemical compounds, MEEMD can provide additional intrinsic features with more reliable mapping of the chemical compounds. MEEMD has the potential to extract intrinsic fluorescence features and improve the detection of biochemical changes.  相似文献   
105.
The mechanical behavior of graphene under various indentation depths, velocities, and temperatures is studied using molecular dynamics analysis. The results show that the load, elastic and plastic energies, and relaxation force increased with increasing indentation depth and velocity. Nanoindentation induced pile ups and corrugations of the graphene. Resistance to deformation decreased at higher temperature. Strong adhesion caused topological defects and vacancies during the unloading process.  相似文献   
106.
In the early stage of a design process, it is important to create numerous and varied possible color plans for the target consumer group. These color plans help individual designers quickly find a few good color design schemes and give the design team ideas for brainstorming. The color plan of a product consists of the color combinations of its components and decorative patterns, which strongly influence the feelings of customers and thus their desire to purchase. However, very few studies have discussed these issues. In this study, a consultation and simulation system for product color planning that helps designers obtain the optimal color planning for components and decorative patterns of a product is proposed. This system includes two parts: one uses the interactive genetic algorithm to establish a creative evolutionary system that can interact with a designer to explore novel design schemes; the other extends the boundary extract algorithm to establish a color simulation system that can apply colors to the areas of product components and decorative patterns for color simulation. Finally, a case study of color planning for a motorcycle model is used to verify the feasibility of the proposed system. © 2012 Wiley Periodicals, Inc. Col Res Appl, 38, 375–390, 2013  相似文献   
107.
A novel anthraquinone‐containing bis(ether amine) monomer, 2,6‐bis(4‐aminophenoxy)anthraquinone, was synthesized from readily available reagents. A series of novel aromatic polyimides were prepared from the newly synthesized diamine monomer with various aromatic tetracarboxylic dianhydrides. The intermediate poly(amic acid)s had inherent viscosities of 0.67–1.12 dL g?1, and those derived from less stiff dianhydrides could be solution‐cast and thermally cyclodehydrated into flexible and tough polyimide films. The polyimides exhibited glass transition temperatures between 270 and 297 °C, and they were fairly stable up to a temperature of 500 °C in air or nitrogen. The electrochemical and electrochromic properties of one of the polyimides were investigated. The polymer could undergo two reversible steps of electrochemical reduction, with a color change from a colorless neutral state to pink and rose‐red reduced states. © 2012 Society of Chemical Industry  相似文献   
108.
Obesity-related neurodegenerative diseases are associated with elevated saturated fatty acids (SFAs) in the brain. An increase in SFAs, especially palmitic acid (PA), triggers neuron cell apoptosis, causing cognitive function to deteriorate. In the present study, we focused on the specific mechanism by which PA triggers SH-SY5Y neuron cell apoptosis. We found that PA induces significant neuron cell cycle arrest in the G2/M phase in SH-SY5Y cells. Our data further showed that G2/M arrest is involved in elevation of endoplasmic reticular (ER) stress according to an increase in p-eukaryotic translation inhibition factor 2α, an ER stress marker. Chronic exposure to PA also accelerates beta-amyloid accumulation, a pathological characteristic of Alzheimer’s disease. Interestingly, SFA-induced ER stress, G2/M arrest and cell apoptosis were reversed by treatment with 2-bromopalmitate, a protein palmitoylation inhibitor. These findings suggest that protein palmitoylation plays a crucial role in SFA-induced neuron cell cycle G2/M arrest, ER stress and apoptosis; this provides a novel strategy for preventing SFA-induced neuron cell dysfunction.  相似文献   
109.
Gold nanoparticles (AuNPs) have been deposited on n-type Ge photodetectors to improve the responsivity. Two different coverage ratios, including 10.5 and 30.3% of AuNPs have been prepared, and the fabricated photodetectors are compared with the control sample. The 1,310-nm responsivities at -2 V of the control, 10.5% AuNPs, and 30.3% AuNPs samples are 465, 556, and 623 mA/W, respectively. The AuNPs could increase the responsivities due to the plasmon resonance. The reflectance spectra of these samples have been measured to verify that plasmon resonance contributes to the forward scattering of incident light. The reflectance decreases with AuNP deposition, and a denser coverage results in a smaller reflectance. The smaller reflectance indicates more light could penetrate into the Ge active layer, and it results in a larger responsivity.  相似文献   
110.
Photo-assisted one-step electrodeposition has been applied to help in forming smooth and dense CuInSe2 films. The difference in surface morphology and crystalline quality between CuInSe2 films with various photo-assistance has been investigated. In the photo-assisted electrodeposition process, the many kinds of lamps providing maximum light intensity at about 380 to 620 nm were used as light source to be irradiated onto the surface of Mo-coated soda-lime glass substrates. The results suggested effects of photo-assistance including activating surface diffusion and growing high-crystalline quality films with reduced defects during electrodeposition.  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