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   4870篇
  免费   290篇
  国内免费   11篇
电工技术   35篇
综合类   5篇
化学工业   1042篇
金属工艺   101篇
机械仪表   102篇
建筑科学   243篇
矿业工程   8篇
能源动力   150篇
轻工业   462篇
水利工程   47篇
石油天然气   21篇
武器工业   2篇
无线电   427篇
一般工业技术   925篇
冶金工业   830篇
原子能技术   28篇
自动化技术   743篇
  2024年   6篇
  2023年   42篇
  2022年   82篇
  2021年   137篇
  2020年   95篇
  2019年   110篇
  2018年   142篇
  2017年   128篇
  2016年   161篇
  2015年   122篇
  2014年   159篇
  2013年   276篇
  2012年   274篇
  2011年   339篇
  2010年   241篇
  2009年   266篇
  2008年   300篇
  2007年   283篇
  2006年   229篇
  2005年   240篇
  2004年   175篇
  2003年   152篇
  2002年   157篇
  2001年   79篇
  2000年   66篇
  1999年   62篇
  1998年   61篇
  1997年   62篇
  1996年   70篇
  1995年   52篇
  1994年   59篇
  1993年   56篇
  1992年   43篇
  1991年   37篇
  1990年   44篇
  1989年   43篇
  1988年   38篇
  1987年   41篇
  1986年   40篇
  1985年   32篇
  1984年   27篇
  1983年   28篇
  1982年   28篇
  1981年   14篇
  1980年   13篇
  1979年   9篇
  1978年   13篇
  1976年   9篇
  1975年   6篇
  1974年   5篇
排序方式: 共有5171条查询结果,搜索用时 15 毫秒
101.
Surfaces enabling directional liquid transportation are of great interest for a wide range of applications such as water collection, microfluidics, and heat transfer systems. Surfaces capable of lossless, long-range passive transportation of low surface tension (LST) liquids using wettability patterned, liquidlike coatings with minimal contact angle hysteresis are reported. Lossless LST droplet travel distances over 150 mm are achieved, enabled by a two-phase transportation mechanism: morphological transformation from a bulge to a channel shape, followed by directional transportation along the asymmetrical wedge-shaped channel. The developed surfaces can split, merge, and precisely transport various low-surface tension liquids, including alcohols, alkanes, and solvents. The developed transportation strategy can also enhance LST liquid dropwise condensation through continuous removal of the condensate, even on horizontally positioned surfaces without the assistance of gravity.  相似文献   
102.

In this work we study, design, and evaluate computational methods to support interpretation of statutory terms. We propose a novel task of discovering sentences for argumentation about the meaning of statutory terms. The task models the analysis of past treatment of statutory terms, an exercise lawyers routinely perform using a combination of manual and computational approaches. We treat the discovery of sentences as a special case of ad hoc document retrieval. The specifics include retrieval of short texts (sentences), specialized document types (legal case texts), and, above all, the unique definition of document relevance provided in detailed annotation guidelines. To support our experiments we assembled a data set comprising 42 queries (26,959 sentences) which we plan to release to the public in the near future in order to support further research. Most importantly, we investigate the feasibility of developing a system that responds to a query with a list of sentences that mention the term in a way that is useful for understanding and elaborating its meaning. This is accomplished by a systematic assessment of different features that model the sentences’ usefulness for interpretation. We combine features into a compound measure that accounts for multiple aspects. The definition of the task, the assembly of the data set, and the detailed task analysis provide a solid foundation for employing a learning-to-rank approach.

  相似文献   
103.
104.
105.
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   
106.
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   
107.
This article presents a study of the evolution of the annealing texture in hafnium, as measured by electron backscattering diffraction patterns (EBSPs). It was found that the annealing texture of asreceived extruded rod depended on the annealing temperature. After low-temperature recrystallization, the deformation axis was parallel to or and the basal planes were approximately parallel to the deformation axis. These orientations were deduced by the position of the points in the standard stereographic triangle used to produce the inverse pole figure. As the annealing temperature was raised to 1700 °C, the direction parallel to the rolling direction changed to and the grain size increased. It appeared that the increase in grain size occurred by a process of abnormal grain growth, and this abnormal grain growth appeared to be the cause of the change in the texture. Texture was also examined in samples that had been warm rolled to thickness reductions between 10 and 90 pct and then annealed at 1700 °C. In these samples, the main feature of the texture was that the basal plane became parallel to the rolling plane as the amount of rolling increased. The maximum grain size was observed in samples that had been rolled to a reduction in thickness of 50 pct.  相似文献   
108.
109.
110.
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   
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