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   2832篇
  免费   107篇
  国内免费   39篇
电工技术   85篇
综合类   39篇
化学工业   692篇
金属工艺   67篇
机械仪表   132篇
建筑科学   111篇
矿业工程   23篇
能源动力   85篇
轻工业   253篇
水利工程   25篇
石油天然气   9篇
武器工业   2篇
无线电   256篇
一般工业技术   402篇
冶金工业   248篇
原子能技术   43篇
自动化技术   506篇
  2023年   12篇
  2022年   15篇
  2021年   53篇
  2020年   28篇
  2019年   55篇
  2018年   66篇
  2017年   44篇
  2016年   57篇
  2015年   62篇
  2014年   81篇
  2013年   166篇
  2012年   137篇
  2011年   207篇
  2010年   191篇
  2009年   202篇
  2008年   212篇
  2007年   177篇
  2006年   141篇
  2005年   163篇
  2004年   94篇
  2003年   100篇
  2002年   99篇
  2001年   58篇
  2000年   46篇
  1999年   34篇
  1998年   49篇
  1997年   34篇
  1996年   39篇
  1995年   32篇
  1994年   31篇
  1993年   41篇
  1992年   31篇
  1991年   20篇
  1990年   20篇
  1989年   14篇
  1988年   21篇
  1987年   19篇
  1986年   9篇
  1985年   22篇
  1984年   16篇
  1983年   19篇
  1982年   8篇
  1981年   17篇
  1980年   11篇
  1979年   6篇
  1977年   5篇
  1976年   4篇
  1974年   2篇
  1973年   3篇
  1964年   1篇
排序方式: 共有2978条查询结果,搜索用时 22 毫秒
1.
为综合利用极坐标牛顿法潮流方程数少、雅可比矩阵J元素少以及直角坐标牛顿法中没有三角函数计算的特点,并克服极坐标牛顿法潮流J阵元素的不对称使其计算速度不理想的情况,提出一种对称极坐标牛顿法潮流的直角坐标解法.主要内容为,建立结构不完全对称的子阵形式的极坐标J阵,通过子阵建立子阵元素间的对应关系;拆分J阵元素的计算,建立子阵元素的部分对称关系;对J阵元素等计算公式进行三角变换,并按"二行+二列"的对称方式计算J阵元素;用四角规则而不是消元计算公式对J阵元素消元;将取倒的对角元素作为规格化因子以减少除法计算.新方法不但可实现J阵元素的部分对称计算,还可大量减少三角函数的运算以及消元过程中的除法运算,且无需计算公式直接完成消元计算.以IEEE-118节点系统为例,新方法生成J阵速度可提高约90%以上,潮流计算速度可提高约30%,并极利于编程.  相似文献   
2.
3.
Journal of Materials Science - We attempted melt-spinning and investigated the compatibility and thermal decomposition of a mixture comprising polysilsesquioxane and polycarbosilane for the purpose...  相似文献   
4.
The discovery of Lgr5+ intestinal stem cells (ISCs) triggered a breakthrough in the field of ISC research. Lgr5+ ISCs maintain the homeostasis of the intestinal epithelium in the steady state, while these cells are susceptible to epithelial damage induced by chemicals, pathogens, or irradiation. During the regeneration process of the intestinal epithelium, more quiescent +4 stem cells and short-lived transit-amplifying (TA) progenitor cells residing above Lgr5+ ISCs undergo dedifferentiation and act as stem-like cells. In addition, several recent reports have shown that a subset of terminally differentiated cells, including Paneth cells, tuft cells, or enteroendocrine cells, may also have some degree of plasticity in specific situations. The function of ISCs is maintained by the neighboring stem cell niches, which strictly regulate the key signal pathways in ISCs. In addition, various inflammatory cytokines play critical roles in intestinal regeneration and stem cell functions following epithelial injury. Here, we summarize the current understanding of ISCs and their niches, review recent findings regarding cellular plasticity and its regulatory mechanism, and discuss how inflammatory cytokines contribute to epithelial regeneration.  相似文献   
5.
Computer‐Interpretable Guidelines (CIGs) are the dominant medium for the delivery of clinical decision support, given the evidence‐based nature of their source material. Therefore, these machine‐readable versions have the ability to improve practitioner performance and conformance to standards, with availability at the point and time of care. The formalisation of Clinical Practice Guideline knowledge in a machine‐readable format is a crucial task to make it suitable for the integration in Clinical Decision Support Systems. However, the current tools for this purpose reveal shortcomings with respect to their ease of use and the support offered during CIG acquisition and editing. In this work, we characterise the current landscape of CIG acquisition tools based on the properties of guideline visualisation, organisation, simplicity, automation, manipulation of knowledge elements, and guideline storage and dissemination. Additionally, we describe the CompGuide Editor, a tool for the acquisition of CIGs in the CompGuide model for Clinical Practice Guidelines that also allows the editing of previously encoded guidelines. The Editor guides the users throughout the process of guideline encoding and does not require proficiency in any programming language. The features of the CIG encoding process are revealed through a comparison with already established tools for CIG acquisition.  相似文献   
6.
Ken Yoda 《Advanced Robotics》2019,33(3-4):108-117
ABSTRACT

This review summarizes the advances in bio-logging technology that enables us to monitor foraging behavior, movement, behavioral performance, physiological performance, and sociality in a wide range of bird species, as well as their habitat. Subsequently, navigation is discussed, using long-distance movements in streaked shearwaters as a case study. Moreover, challenges and future research directions in bio-logging science are presented, with focus on: multimodal recording, big data analysis, feedback logging, low-power consumption and power generation systems, logger effects, and capture–recapture methods.  相似文献   
7.
8.
We have developed stacked nanocarbon polymer actuators that are composed of several nanocarbon polymer actuator films using nonwoven fabric as insulation layers. The nonwoven fabric prepared through electrospinning methods has extremely-low-density structures, which do not significantly prevent the motions of each nanocarbon actuator layer. Therefore, stacking several thin nanocarbon polymer actuators using nonwoven fabric as insulation layers is expected to increase generated force without decreasing the displacement of a one-layer actuator. We have prepared stacked actuators with one, two, three, four, and seven layers using this method. The displacement and blocking force of these actuators are measured and compared with those of one-layer actuators of different thicknesses. Displacement is weakly dependent on the thickness of the actuator films of the stacked actuators. On the contrary, it decreases considerably as the thickness of the actuator film of the one-layer actuator increases. In both cases, blocking force is proportional to the thickness of actuator films. We have developed a stacked actuator model based on a trilayer actuator model and confirmed the experimental results using the model.  相似文献   
9.
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