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   285880篇
  免费   24573篇
  国内免费   14219篇
电工技术   22606篇
技术理论   53篇
综合类   38107篇
化学工业   31538篇
金属工艺   10178篇
机械仪表   15101篇
建筑科学   37601篇
矿业工程   15045篇
能源动力   10538篇
轻工业   16277篇
水利工程   14274篇
石油天然气   11723篇
武器工业   2659篇
无线电   21944篇
一般工业技术   20700篇
冶金工业   15835篇
原子能技术   2823篇
自动化技术   37670篇
  2024年   432篇
  2023年   2859篇
  2022年   5155篇
  2021年   6581篇
  2020年   6960篇
  2019年   5916篇
  2018年   5435篇
  2017年   6748篇
  2016年   7994篇
  2015年   8959篇
  2014年   16291篇
  2013年   14923篇
  2012年   19533篇
  2011年   20834篇
  2010年   16404篇
  2009年   17101篇
  2008年   15924篇
  2007年   20562篇
  2006年   19383篇
  2005年   16857篇
  2004年   14325篇
  2003年   12781篇
  2002年   10511篇
  2001年   8836篇
  2000年   7384篇
  1999年   5976篇
  1998年   4479篇
  1997年   3932篇
  1996年   3696篇
  1995年   3182篇
  1994年   2824篇
  1993年   2120篇
  1992年   1874篇
  1991年   1400篇
  1990年   1208篇
  1989年   1050篇
  1988年   837篇
  1987年   569篇
  1986年   430篇
  1985年   378篇
  1984年   351篇
  1983年   258篇
  1982年   225篇
  1981年   178篇
  1980年   144篇
  1979年   115篇
  1978年   67篇
  1977年   76篇
  1976年   56篇
  1975年   56篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
81.
82.
The classical prompt loss of fast ions produced by minority ion cyclotron resonance heating(ICRH)is studied by a guiding center orbit following code in the Experimental Advanced Superconducting Tokamak(EAST).It is found that the loss of fast ions produced by ICRH mainly appears in both ends of the resonance layer,while the loss of fast ions in the middle resonance layer is very small.The dominant fast loss comes from trapped ions,rather than from passing ions.Controlling the location of resonance layer at the plasma core may be more beneficial to the EAST tokamak ICRH.In addition,the loss distribution of fast ions is studied.The results show that the fast ions are mainly lost near the midplane in the poloidal direction,but almost uniformly in the toroidal direction.Moreover,we investigate the dependence of fast ion loss on the ICRH power.The simulation results show that the loss fraction of fast ions in both ends of the resonance region increases with the ion cyclotron range of frequencies(ICRF)power,but barely affects the loss of fast ions in the middle region.  相似文献   
83.
针对CAGAN(Conditional Analogy GAN)换衣后效果模糊,在目标衣服与原始衣服长短不一致时效果一般,相对目标衣服保留过少的细节等问题做了相关研究并对CAGAN进行了改进,提出了新的虚拟试衣方式。经过改进的CAGAN生成一个粗糙的结果,由该结果得到目标衣服穿在模特身上改变形状后的mask,接下来利用mask对目标衣服进行变形,综合变形的衣服和第一步的结果便得到最终的试衣图像。实验结果表明,该方法解决了前面存在的问题,而且取得了非常好的效果。  相似文献   
84.
Against the background of smart manufacturing and Industry 4.0, how to achieve real-time scheduling has become a problem to be solved. In this regard, automatic design for shop scheduling based on hyper-heuristics has been widely studied, and a number of reviews and scheduling algorithms have been presented. Few studies, however, have specifically discussed the technical points involved in algorithm development. This study, therefore, constructs a general framework for automatic design for shop scheduling strategies based on hyper-heuristics, and various state-of-the-art technical points in the development process are summarized. First, we summarize the existing types of shop scheduling strategies and classify them using a new classification method. Second, we summarize an automatic design algorithm for shop scheduling. Then, we investigate surrogate-assisted methods that are popular in the current algorithm field. Finally, current problems and challenges are discussed, and potential directions for future research are proposed.  相似文献   
85.
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C.  相似文献   
86.
We propose a general framework to study the relationship between the price of a painting and its color‐related attributes. To this end we focus on four key aspects: dominant colors, features of the color palette, color harmony, and color emotions. We demonstrate the usefulness of this approach with an example based on Mark Rothko's post‐1950 paintings (the “rectangular” series), and auction data from the 1994 to 2018 period. We identify two distinct price‐color regimes in Rothko's market: (a) [1994‐2005], a period in which prices are explained mainly by the growing popularity of the artist regardless of the color attributes of the paintings sold; and (b) [2006‐2018], a period in which color‐related attributes explain most of the prices. Furthermore, we find that in this second period, the dominant colors and the diversity of the color palette, are by far the most relevant attributes that influence the price; color harmony and color emotions hold almost no explanatory power during this period. Finally, we propose a new metric based on the Herfindahl Index to describe color diversity; this metric seems to be promising at characterizing the effect of the color palette on the price of a painting.  相似文献   
87.
黄泽颖  黄贝珣 《食品与机械》2021,37(11):228-231
对英国食品每日摄入量指南(GDAs)标签开展案例研究,结果发现,GDAs标签从包装背面标签转为FOP标签,实施已有20年以上。该标签采用特定营养素体系度量法模型,显示每份食品能量、糖、脂肪、饱和脂肪、盐的含量及其每日参考摄入量占比,既没有颜色编码又没有形象的图标显示,且实施效果不如多数FOP标签。对此,中国可考虑将营养成分表信息以食品份量单位直观显示在包装正面,方便消费者关注与理解。  相似文献   
88.
89.
针对热液白云岩展布非均质性强的问题,开展基底断裂与茅三段沉积演化关系研究,分析断裂样式与白云岩分布关系,建立沉积演化模式,预测白云岩的分布。研究结果表明:茅三段可划分为5个小层,1~3小层为白云岩发育主要时期,4~5小层为台地均一化时期,不发育白云岩;15-1、15-2和16号基底断裂控制了早期“台-洼”相间的沉积地貌,断裂附近的地貌高部位为生屑滩发育有利部位,为白云岩的发育提供物质基础;15-1、15-2号基底断裂样式为花状,周边生屑滩白云石化程度高,为白云岩发育最有利区;16号基底断裂为直立状,附近白云石化发育程度较低,为白云岩发育较有利区。研究成果可为热液白云岩领域的进一步勘探提供指导依据。  相似文献   
90.
The effect of the emergency perception of bystanders of cyberbullying victims on helping behaviors is often neglected in research on cyberbullying. In this study, we explored the influence of this cognitive factor on cyber-bystanders’ helping tendencies as well as elucidated possible underlying processes. The results of two studies were reported. In Study 1, 150 undergraduates read a true case of a girl experiencing cyberbullying. The results indicated that when the participants perceived the victim’s situation to be more critical (i.e., higher emergency perception), their helping tendencies were stronger, partly through increased state empathy followed by feelings of responsibility to help. In Study 2, we randomly assigned 300 undergraduates to two groups. The low emergency group read the same cyberbullying case as Study 1, whereas the cyberbullying case read by the high emergency group contained additional emergency information of the victim. The results indicated that the high emergency group expressed stronger helping tendencies than did the low emergency group. This effect was caused by a stronger perception that the victim was in an emergency situation, which not only strengthened the participants’ helping tendencies directly but also indirectly through increasing their state empathy and feelings of responsibility to help.  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