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   2893篇
  免费   358篇
  国内免费   97篇
电工技术   34篇
技术理论   1篇
综合类   199篇
化学工业   1151篇
金属工艺   61篇
机械仪表   51篇
建筑科学   87篇
矿业工程   67篇
能源动力   72篇
轻工业   464篇
水利工程   41篇
石油天然气   70篇
武器工业   7篇
无线电   361篇
一般工业技术   408篇
冶金工业   154篇
原子能技术   18篇
自动化技术   102篇
  2024年   8篇
  2023年   73篇
  2022年   97篇
  2021年   136篇
  2020年   147篇
  2019年   127篇
  2018年   112篇
  2017年   122篇
  2016年   126篇
  2015年   110篇
  2014年   186篇
  2013年   172篇
  2012年   238篇
  2011年   262篇
  2010年   145篇
  2009年   173篇
  2008年   154篇
  2007年   165篇
  2006年   135篇
  2005年   108篇
  2004年   87篇
  2003年   73篇
  2002年   65篇
  2001年   64篇
  2000年   53篇
  1999年   43篇
  1998年   33篇
  1997年   28篇
  1996年   18篇
  1995年   17篇
  1994年   8篇
  1993年   9篇
  1992年   9篇
  1991年   5篇
  1990年   8篇
  1989年   3篇
  1988年   1篇
  1987年   6篇
  1986年   1篇
  1985年   7篇
  1984年   4篇
  1983年   2篇
  1982年   3篇
  1981年   1篇
  1980年   1篇
  1978年   2篇
  1966年   1篇
排序方式: 共有3348条查询结果,搜索用时 343 毫秒
101.
在含 2 5mg·L- 1 的亚甲基兰的正常和无氮培养液中培养盐泽螺旋藻 ,观测盐泽螺旋藻的生长、叶绿素含量、藻胆素含量及其对亚甲基兰的脱色率。结果表明 ,盐泽螺旋藻可由染料亚甲基兰提供唯一氮源 ,但不能提供唯一碳源。在培养 8d后 ,无氮培养液中的螺旋藻液吸光度达到 0 2 1 0 ;在正常培养液下螺旋藻液吸光度为 0 32 1。盐泽螺旋藻对染料的脱色效果也比较好 ,在培养 8d后 ,无氮培养液下亚甲基兰脱色率为 85 %;正常培养液下亚甲基兰脱色率为 86%。  相似文献   
102.
Abstract— Defect‐free large‐area inorganic thick‐dielectric EL (TDEL) displays using Color by Blue (CBB) technology have been successfully developed. We have achieved the world's highest blue‐phosphor luminance of 900 cd/m2 for a single‐pixel device by using CBB and by optimizing the e‐beam gun configuration and the flow rate of H2S in the vacuum chamber. By analyzing the defects on panels with triple‐pattern phosphors and CBB panels, we also found that the number of defects on CBB panels can be drastically reduced compared with those on triple‐pattern panels. The defect‐free 17‐in. VGA CBB panels show better characteristics, a high peak luminance of 600 cd/m2 and a high contrast ratio of 1000:1, compared with those of triple‐pattern panels.  相似文献   
103.
A new method that combines fractal theory and red, green and blue (RGB) colour intensity was developed to sort dried jujube fruits by using support vector machine (SVM). Our result shows that the new method is fast and accurate in dried jujube fruits classification. The SVM models based on fractal parameters only achieved 85.18–92.73% total accuracy rate. The total classification accuracy of SVM based on RGB intensity values was 94.44%. However, the SVM models based on combining fractal parameters with RGB intensity values achieved 94.44–98.15% total accuracy rate. The best classification accuracy (98.15%) was found when using SVM model based on combining fractal measures (FM) with RGB intensity values (C = 512, γ = 0.0078125). Therefore, the SVM model based on combining FMs with RGB intensity is recommended in dried jujube fruits classification.  相似文献   
104.
CoS2 and a CoS2–graphene composite were synthesized via a facile sonochemical and hydrothermal method. As-prepared samples were characterized by X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray analysis, transmission electron microscopy, and UV-vis diffuse reflectance spectroscopy. The CoS2–graphene composites exhibited high dye adsorption, extended light absorption, and efficient charge separation properties. Hence, for photodegradation of methylene blue (MB), significant enhancement of the reaction rate was observed for CoS2–graphene compared to pure CoS2. The high activity can be attributed to positive synergetic effects between CoS2 and graphene. The excellent photoinduced charge separation and observed red shift make these hybrid materials potential candidates for the development of high-performance next-generation photocatalyst materials.  相似文献   
105.
106.
余磁 《中国陶瓷》2012,(8):59-60,72
"昭君出塞"故事源于汉代,绵延流传,元青花《昭君出塞》罐表现的即为"昭君出塞"故事题材。元青花《昭君出塞》罐具有鲜明的艺术特征,同时,亦具有丰富而深邃的主题思想内涵。  相似文献   
107.
A thermally activated delayed fluorescent (TADF) emitter, 2,7-bis(9,9-dimethylacridin-10(9H)-yl)-9,9-dimethyl-9H-thioxanthene 10,10-dioxide (DMTDAc), was developed as a deep blue TADF emitter using a rigid 9,9-dimethyl-9H-thioxanthene 10,10-dioxide (DMTD) acceptor and an acridine donor. The rigid DMTD acceptor narrowed emission spectrum of DMTDAc by interlocking two phenyl units of diphenylsulfone. A deep blue TADF device with an external quantum efficiency close to 20% with a deep blue color coordinate of (0.15,0.13) was provided using the DMTDAc TADF emitter.  相似文献   
108.
张进 《广东化工》2012,39(17):34-35
利用水热法制备了BiVO4粉体,并通过X射线衍射(XRD)、扫描电镜(SEM)、紫外一可见漫反射光谱(DRS)等对催化剂进行了表征。以制备的BiVO4为催化剂,考察了可见光照射下其对亚甲基蓝的降解效果。研究结果表明对初始质量浓度为10 mg/L的亚甲基蓝溶液50 mL,BiVO4加入量为0.6 g/L,经500 W氙灯(可见光)照射6 h后,亚甲基蓝的脱色率可达64%。  相似文献   
109.
Massive sequence view (MSV) is a classic timeline-based dynamic network visualization approach. However, it is vulnerable to visual clutter caused by overlapping edges, thereby leading to unexpected misunderstanding of time-varying trends of network communications. This study presents a new edge sampling algorithm called edge-based multi-class blue noise (E-MCBN) to reduce visual clutter in MSV. Our main idea is inspired by the multi-class blue noise (MCBN) sampling algorithm, commonly used in multi-class scatterplot decluttering. First, we take a node pair as an edge class, which can be regarded as an analogy to classes in multi-class scatterplots. Second, we propose two indicators, namely, class overlap and inter-class conflict degrees, to measure the overlapping degree and mutual exclusion, respectively, between edge classes. These indicators help construct the foundation of migrating the MCBN sampling from multi-class scatterplots to dynamic network samplings. Finally, we propose three strategies to accelerate MCBN sampling and a partitioning strategy to preserve local high-density edges in the MSV. The result shows that our approach can effectively reduce visual clutters and improve the readability of MSV. Moreover, our approach can also overcome the disadvantages of the MCBN sampling (i.e., long-running and failure to preserve local high-density communication areas in MSV). This study is the first that introduces MCBN sampling into a dynamic network sampling.  相似文献   
110.
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