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   1482篇
  免费   79篇
  国内免费   9篇
电工技术   15篇
综合类   6篇
化学工业   312篇
金属工艺   44篇
机械仪表   37篇
建筑科学   43篇
矿业工程   7篇
能源动力   83篇
轻工业   73篇
水利工程   5篇
石油天然气   5篇
无线电   240篇
一般工业技术   277篇
冶金工业   166篇
原子能技术   15篇
自动化技术   242篇
  2023年   30篇
  2022年   32篇
  2021年   71篇
  2020年   58篇
  2019年   51篇
  2018年   70篇
  2017年   46篇
  2016年   61篇
  2015年   41篇
  2014年   57篇
  2013年   115篇
  2012年   57篇
  2011年   79篇
  2010年   54篇
  2009年   47篇
  2008年   58篇
  2007年   47篇
  2006年   27篇
  2005年   34篇
  2004年   26篇
  2003年   21篇
  2002年   17篇
  2001年   24篇
  2000年   18篇
  1999年   14篇
  1998年   32篇
  1997年   26篇
  1996年   21篇
  1995年   24篇
  1994年   15篇
  1993年   27篇
  1992年   15篇
  1991年   9篇
  1990年   12篇
  1989年   11篇
  1988年   12篇
  1987年   9篇
  1986年   21篇
  1985年   25篇
  1984年   21篇
  1983年   12篇
  1982年   15篇
  1981年   11篇
  1980年   12篇
  1978年   12篇
  1977年   9篇
  1976年   12篇
  1975年   7篇
  1973年   11篇
  1971年   7篇
排序方式: 共有1570条查询结果,搜索用时 15 毫秒
31.
Knowledge of materials' thermal‐transport properties, conductivity and diffusivity, is crucial for several applications within areas of biology, material science and engineering. Specifically, a microsized, flexible, biologically integrated thermal transport sensor is beneficial to a plethora of applications, ranging across plants physiological ecology and thermal imaging and treatment of cancerous cells, to thermal dissipation in flexible semiconductors and thermoelectrics. Living cells pose extra challenges, due to their small volumes and irregular curvilinear shapes. Here a novel approach of simultaneously measuring thermal conductivity and diffusivity of different materials and its applicability to single cells is demonstrated. This technique is based on increasing phonon‐boundary‐scattering rate in nanomembranes, having extremely low flexural rigidities, to induce a considerable spectral dependence of the bandgap‐emission over excitation‐laser intensity. It is demonstrated that once in contact with organic or inorganic materials, the nanomembranes' emission spectrally shift based on the material's thermal diffusivity and conductivity. This NM‐based technique is further applied to differentiate between different types and subtypes of cancer cells, based on their thermal‐transport properties. It is anticipated that this novel technique to enable an efficient single‐cell thermal targeting, allow better modeling of cellular thermal distribution and enable novel diagnostic techniques based on variations of single‐cell thermal‐transport properties.  相似文献   
32.
The Mott transistor is a paradigm for a new class of electronic devices—often referred to by the term Mottronics—which are based on charge correlations between the electrons. Since correlation‐induced insulating phases of most oxide compounds are usually very robust, new methods have to be developed to push such materials right to the boundary to the metallic phase in order to enable the metal–insulator transition to be switched by electric gating. Here, it is demonstrated that thin films of the prototypical Mott insulator LaTiO3 grown by pulsed laser deposition under oxygen atmosphere are readily tuned by excess oxygen doping across the line of the band‐filling controlled Mott transition in the electronic phase diagram. The detected insulator to metal transition is characterized by a strong change in resistivity of several orders of magnitude. The use of suitable substrates and capping layers to inhibit oxygen diffusion facilitates full control of the oxygen content and renders the films stable against exposure to ambient conditions. These achievements represent a significant advancement in control and tuning of the electronic properties of LaTiO3+x thin films making it a promising channel material in future Mottronic devices.  相似文献   
33.
This article proposes a PRNN/ERLS-based predictive QoS-promoted dynamic bandwidth allocation (PQ-DBA) scheme for upstream transmission in Ethernet passive optical network (EPON) systems. The proposed PQ-DBA scheme originally divides incoming packets of voice, video, data service traffic into six priorities, where packets having less room before QoS requirements violation or being in starvation situation will be dynamically promoted to high priority cycle-by-cycle. It predicts packets arriving at prediction interval for ONUs using pipeline recurrent neural network (PRNN)/extended recursive least squares (ERLS) so that the bandwidth allocation can be more up-to-date and then accurate. Simulation results show that the proposed PQ-DBA scheme achieves higher system utilization and lower average voice, video, data packet delay time than the DBAM scheme [Luo and Ansari, OSA J Opt Netw 4(9):561–572] by 4, and 21, 90, 43%, respectively, and the PQ-DBA scheme but without prediction by 2, and 26, 29, 34%, respectively.  相似文献   
34.
最近几年,薄膜晶体管液晶显示器(TFT-LCD)技术取得了快速而显著的进步,其性能超过了PDP、CRT以及投影显示。毫无疑问,TFT-LCD已经成为高清电视应用的最佳实现方案。本文将介绍进一步增强大尺寸LCD电视的彩色和图像性能的技术。  相似文献   
35.
Crowdsourcing has emerged as a new method for obtaining annotations for training models for machine learning. While many variants of this process exist, they largely differ in their methods of motivating subjects to contribute and the scale of their applications. To date, there has yet to be a study that helps the practitioner to decide what form an annotation application should take to best reach its objectives within the constraints of a project. To fill this gap, we provide a faceted analysis of crowdsourcing from a practitioner’s perspective, and show how our facets apply to existing published crowdsourced annotation applications. We then summarize how the major crowdsourcing genres fill different parts of this multi-dimensional space, which leads to our recommendations on the potential opportunities crowdsourcing offers to future annotation efforts.  相似文献   
36.
Fair bandwidth allocation (FBA) has been studied in optical burst switching (OBS) networks, with the main idea being to map the max-min fairness in traditional IP networks to the fair-loss probability in OBS networks. This approach has proven to be fair in terms of the bandwidth allocation for differential connections, but the use of the ErlangB formula to calculate the theoretical loss probability has made this approach applicable only to Poisson flows. Furthermore, it is necessary to have a reasonable fairness measure to evaluate FBA models. This article proposes an approach involving throughput-based-FBA, called TFBA, and recommends a new fairness measure that is based on the ratio of the actual throughput to the allocated bandwidth. An analytical model for the performance of the output link with TFBA is also proposed.  相似文献   
37.
Wireless Personal Communications - Cognitive radio networks (CRNs) have a shortcoming in that attackers can increase their ability to disturb secondary users (SUs). This paper focuses on jamming...  相似文献   
38.
Multimedia Tools and Applications - In this paper, we propose a novel reversible data hiding technique based on two-dimensional histogram shifting for quantized discrete cosine transformation...  相似文献   
39.
This paper empirically tests the interactive effects of air pollution and economic spillovers in Chinese cities from 2003 to 2010. The results show that Chinese cities benefit from the economic spillovers from surrounding cities, but bear the costs of negative air pollution externalities created by neighboring cities. We use wind direction and the administrative boundaries of provinces to disentangle possible multicollinearity between air pollution emissions and economic spillovers across cities. However, the results could not reject the growth-restricting effects of air pollution from neighboring cities. The results imply that the development of a city surrounded by polluters is likely to be constrained.  相似文献   
40.
The cubic ( c -ZrO2) and tetragonal zirconia ( t -ZrO2) phase stability regions in the system ZrO2–Y2O3–Ta2O5 were delineated. The c -ZrO2 solid solutions are formed with the fluorite structure. The t -ZrO2 solid solutions having a c/a axial ratio (tetragonality) smaller than 1.0203 display high fracture toughness (5 to 14 MPa · m1/2), and their instability/transformability to monoclinic zirconia ( m -ZrO2) increases with increasing tetragonality. On the other hand, the t -ZrO2 solid solutions stabilized at room temperature with tetragonality greater than 1.0203 have low toughness values (2 to 5 MPa · m1/2), and their transformability is not related to the tetragonality.  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