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   4724篇
  免费   286篇
  国内免费   11篇
电工技术   31篇
综合类   5篇
化学工业   995篇
金属工艺   96篇
机械仪表   103篇
建筑科学   237篇
矿业工程   8篇
能源动力   154篇
轻工业   455篇
水利工程   47篇
石油天然气   18篇
武器工业   2篇
无线电   414篇
一般工业技术   880篇
冶金工业   813篇
原子能技术   29篇
自动化技术   734篇
  2023年   40篇
  2022年   67篇
  2021年   133篇
  2020年   94篇
  2019年   110篇
  2018年   141篇
  2017年   126篇
  2016年   157篇
  2015年   118篇
  2014年   158篇
  2013年   274篇
  2012年   275篇
  2011年   339篇
  2010年   240篇
  2009年   267篇
  2008年   298篇
  2007年   282篇
  2006年   228篇
  2005年   238篇
  2004年   170篇
  2003年   147篇
  2002年   151篇
  2001年   75篇
  2000年   65篇
  1999年   57篇
  1998年   62篇
  1997年   58篇
  1996年   67篇
  1995年   49篇
  1994年   48篇
  1993年   50篇
  1992年   37篇
  1991年   26篇
  1990年   38篇
  1989年   38篇
  1988年   31篇
  1987年   41篇
  1986年   38篇
  1985年   32篇
  1984年   25篇
  1983年   27篇
  1982年   25篇
  1981年   13篇
  1980年   13篇
  1979年   9篇
  1978年   13篇
  1977年   4篇
  1976年   6篇
  1975年   6篇
  1974年   4篇
排序方式: 共有5021条查询结果,搜索用时 15 毫秒
101.
102.
Simultaneous analysis of messenger RNA (mRNA), microRNA (miRNA), and long noncoding RNA (lncRNA)—multi‐RNA‐type profiling—is increasingly crucial in cancer diagnostics. Yet, rapid multi‐RNA‐type profiling is challenging due to enzymatic amplification reliance and RNA‐type‐dependent characteristics. Here, a nanodevice is reported to uniquely use alterable alternating current electrohydrodynamic (ac‐EHD) forces to enhance probe–target hybridization prior to direct native RNA target detection, without target amplification or surface functionalization. To exemplify clinical applicability, noninvasive screening of next‐generation prostate cancer (PCa) RNA biomarkers (of different types) in patient urine samples is performed. A strong correlation between multi‐RNA‐type expression and aggressive PCa is found, and the nanodevice performance is statistically evaluated. It is believed that this miniaturized system exhibits great potential for cancer risk stratification via multi‐RNA‐type profiling.  相似文献   
103.
Dimensional synthesis is a type of inverse problem in linkage kinematics where the objective is to calculate the linkage dimensions required to achieve prescribed linkage output motion. Motion generation is a particular category of dimensional synthesis where the objective is to calculate the linkage dimensions required to achieve a group of prescribed link positions. In motion generation for a four-bar linkage, positions are prescribed for the coupler link. While early motion generation methods were primarily qualitative, ongoing advancements in computing hardware and software continue to make quantitative motion generation more practical. By providing overviews of works representative of developments in quantitative four-bar motion generation since 1970, this work is essentially an overview that spans over 40 years of developments in quantitative four-bar motion generation.  相似文献   
104.
105.
106.
Autonomous underwater vehicles (AUVs) have gained more interest in recent years for military as well as civilian applications. One potential application of AUVs is for the purpose of undersea surveillance. As research into undersea surveillance using AUVs progresses, issues arise as to how an AUV acquires, acts on, and shares information about the undersea battle space. These issues naturally touch on aspects of vehicle autonomy and underwater communications, and need to be resolved through a spiral development process that includes at sea experimentation. This paper presents a recent AUV implementation for active anti-submarine warfare tested at sea in the summer of 2010. On-board signal processing capabilities and an adaptive behavior are discussed in both a simulation and experimental context. The implications for underwater surveillance using AUVs are discussed.  相似文献   
107.
In this paper we present a comparative evaluation of four popular interactive segmentation algorithms. The evaluation was carried out as a series of user-experiments, in which participants were tasked with extracting 100 objects from a common dataset: 25 with each algorithm, constrained within a time limit of 2 min for each object. To facilitate the experiments, a “scribble-driven” segmentation tool was developed to enable interactive image segmentation by simply marking areas of foreground and background with the mouse. As the participants refined and improved their respective segmentations, the corresponding updated segmentation mask was stored along with the elapsed time. We then collected and evaluated each recorded mask against a manually segmented ground truth, thus allowing us to gauge segmentation accuracy over time. Two benchmarks were used for the evaluation: the well-known Jaccard index for measuring object accuracy, and a new fuzzy metric, proposed in this paper, designed for measuring boundary accuracy. Analysis of the experimental results demonstrates the effectiveness of the suggested measures and provides valuable insights into the performance and characteristics of the evaluated algorithms.  相似文献   
108.
Flow maps are thematic maps that visualize the movement of objects, such as people or goods, between geographic regions. One or more sources are connected to several targets by lines whose thickness corresponds to the amount of flow between a source and a target. Good flow maps reduce visual clutter by merging (bundling) lines smoothly and by avoiding self-intersections. Most flow maps are still drawn by hand and only few automated methods exist. Some of the known algorithms do not support edge-bundling and those that do, cannot guarantee crossing-free flows. We present a new algorithmic method that uses edge-bundling and computes crossing-free flows of high visual quality. Our method is based on so-called spiral trees, a novel type of Steiner tree which uses logarithmic spirals. Spiral trees naturally induce a clustering on the targets and smoothly bundle lines. Our flows can also avoid obstacles, such as map features, region outlines, or even the targets. We demonstrate our approach with extensive experiments.  相似文献   
109.
We present a novel approach to the automated marking of student programming assignments. Our technique quantifies the structural similarity between unmarked student submissions and marked solutions, and is the basis by which we assign marks. This is accomplished through an efficient novel graph similarity measure (AssignSim). Our experiments show good correlation of assigned marks with that of a human marker.  相似文献   
110.
Several instruments have been designed to measure problems associated with excessive, compulsive, or addictive use of the Internet. One such instrument, the 18-item Problematic Internet Use Questionnaire, was recently published with data supporting a three subscale model (Demetrovics et al., 2008). These researches utilized an online format with a sample taken from the general population of Hungary. We utilized an American college student sample and a paper and pencil format to perform a confirmatory factor analysis of the PIUQ. In addition, we examined the reliability and construct validity of the PIUQ by examining the scales’ relationship with several indices of psychological and physical health. CFA results indicate a barely adequate and not completely problem free three factor model for the PIUQ (χ2 = 477.40; root mean square error = .097; comparative fit index = .831; Tucker Lewis coefficient = .804). Cronbach’s α for the total scale was .91 while the Cronbach’s α for each subscale were .81, .77, and .79. Construct validity for the model is demonstrated with significant correlations between the subscales and several indices of psychological and physical health. Suggestions for further research are provided.  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