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   22824篇
  免费   3466篇
  国内免费   2710篇
电工技术   1999篇
技术理论   6篇
综合类   2056篇
化学工业   388篇
金属工艺   266篇
机械仪表   1853篇
建筑科学   460篇
矿业工程   272篇
能源动力   237篇
轻工业   120篇
水利工程   221篇
石油天然气   229篇
武器工业   156篇
无线电   3901篇
一般工业技术   1161篇
冶金工业   167篇
原子能技术   153篇
自动化技术   15355篇
  2024年   57篇
  2023年   436篇
  2022年   646篇
  2021年   804篇
  2020年   891篇
  2019年   690篇
  2018年   703篇
  2017年   924篇
  2016年   1109篇
  2015年   1347篇
  2014年   1966篇
  2013年   1827篇
  2012年   2097篇
  2011年   2020篇
  2010年   1357篇
  2009年   1346篇
  2008年   1458篇
  2007年   1596篇
  2006年   1250篇
  2005年   1165篇
  2004年   980篇
  2003年   821篇
  2002年   626篇
  2001年   526篇
  2000年   415篇
  1999年   335篇
  1998年   245篇
  1997年   226篇
  1996年   193篇
  1995年   178篇
  1994年   163篇
  1993年   114篇
  1992年   122篇
  1991年   58篇
  1990年   51篇
  1989年   50篇
  1988年   45篇
  1987年   30篇
  1986年   22篇
  1985年   24篇
  1984年   19篇
  1983年   14篇
  1982年   7篇
  1981年   6篇
  1980年   9篇
  1979年   8篇
  1977年   8篇
  1976年   5篇
  1975年   3篇
  1972年   2篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
81.
Recently, an increasing number of works start investigating the combination of fog computing and electronic health (ehealth) applications. However, there are still numerous unresolved issues worth to be explored. For instance, there is a lack of investigation on the disease prediction in fog environment and only limited studies show, how the Quality of Service (QoS) levels of fog services and the data stream mining techniques influence each other to improve the disease prediction performance (e.g., accuracy and time efficiency). To address these issues, we propose a fog-based framework for disease prediction based on Medical sensor data streams, named FogMed. This framework aims to improve the disease prediction accuracy by achieving two objectives: QoS guarantee of fog services and anomaly prediction of Medical data streams. We build a virtual FogMed environment and conduct comprehensive experiments on the public ECG dataset to validate the performance of FogMed. The experiment results show that it performs better than the cloud computing model for processing tasks with different complexities in terms of time efficiency.  相似文献   
82.
格点量子色动力学(格点QCD)是研究夸克、胶子等微观粒子间相互作用的重要理论和方法. 通过将时空离散化为四维结构网格, 并将量子色动力学的基本场量定义在网格上, 让研究人员可以使用数值模拟方法, 从第一性原理出发研究强子间相互作用和性质, 但这个过程中的计算量极大, 需要进行大规模并行计算. 格点QCD计算的核心基础为格点QCD求解器, 是程序运行主要的计算热点模块. 本文研究在国产异构计算平台下格点QCD求解器的实现与优化, 提出一套格点QCD求解器的设计实现, 实现了BiCGSTAB求解器, 显著降低了迭代次数; 通过对奇偶预处理技术, 降低了所求问题的计算规模; 针对国产异构加速卡的特点, 优化了Dslash模块的访存操作. 实验测试表明, 相比优化前的求解器获得了约30倍的加速比, 为国产异构超算下格点QCD软件性能优化提供了有益的参考价值.  相似文献   
83.
The performance of conventional computer based on von Neumann architecture is limited due to the physical separation of memory and processor. By synergistically integrating various sensors with synaptic devices, recently emerging interactive neuromorphic devices can directly sense/store/process various stimuli information from external environments and implement functions of perception, learning, memory, and computation. In this review, we present the basic model of bioinspired interactive neuromorphic devices and discuss the performance metrics. Next, we summarize the recent progress and development of bioinspired interactive neuromorphic devices, which are classified into neuromorphic tactile systems, visual systems, auditory systems, and multisensory system. They are discussed in detail from the aspects of materials, device architectures, operating mechanisms, synaptic plasticity, and potential applications. Additionally, the bioinspired interactive neuromorphic devices that can fuse multiple/mixed sensing signals are proposed to address more realistic and sophisticated problems. Finally, we discuss the pros and cons regarding to the computing neurons and integrating sensory neurons and deliver the perspectives on interactive neuromorphic devices at the material, device, network, and system levels. It is believed the neuromorphic devices can provide promising solutions to next generation of interactive sensation/memory/computation toward the development of multimodal, low-power, and large-scale intelligent systems endowed with neuromorphic features.  相似文献   
84.
Naringin (NAR), a major flavanone (FVA) glycoside, is a component of food mainly obtained from grapefruit. We used NAR as a food additive to improve the solubility and permeability of hydrophobic polyphenols used as supplements in the food industry. The spray-dried particles (SDPs) of NAR alone show an amorphous state with a glass transition temperature (Tg) at 93.2 °C. SDPs of hydrophobic polyphenols, such as flavone (FVO), quercetin (QCT), naringenin (NRG), and resveratrol (RVT) were prepared by adding varying amounts of NAR. All SDPs of hydrophobic polyphenols with added NAR were in an amorphous state with a single Tg, but SDPs of hydrophobic polyphenols without added NAR showed diffraction peaks derived from each crystal. The SDPs with NAR could keep an amorphous state after storage at a high humidity condition for one month, except for SDPs of RVT/NAR. SDPs with NAR enhanced the solubility of hydrophobic polyphenols, especially NRG solubility, which was enhanced more than 9 times compared to NRG crystal. The enhanced solubility resulted in the increased membrane permeability of NRG. The antioxidant effect of the hydrophobic NRG was also enhanced by the synergetic effect of NAR. The findings demonstrated that NAR could be used as a food additive to enhance the solubility and membrane permeability of hydrophobic polyphenols.  相似文献   
85.
间柱采场用分段中深孔嗣后充填采矿法回采,为利用中深孔爆破形成切割槽及底部桃形体出矿结构,优化切割天井位置,以溜矿口上方的桃形体作为安全隔柱,利用溜矿口空间作为底部拉槽的凿岩和装药空间;采用平行中深孔和扇形中深孔相结合的方式进行布眼,爆破形成切割槽和底部桃形体出矿结构,避免了采用人工浅孔爆破施工的安全风险,切割槽爆破到位,底部桃形体出矿结构成型良好且稳固安全,该技术已在全矿推广应用。  相似文献   
86.
As a classic NP-hard problem in machine learning and computational geometry, the k-means problem aims to partition the given points into k sets to minimize the within-cluster sum of squares. The k-means problem with penalties (k-MPWP), as a generalizing problem of the k-means problem, allows a point that can be either clustered or penalized with some positive cost. In this paper, we mainly apply the parallel seeding algorithm to the k-MPWP, and show sufficient analysis to bound the expected solution quality in the case where both the number of iterations and the number of points sampled in each iteration can be given arbitrarily. The approximate guarantee can be obtained as , where is a polynomial function involving the maximal ratio M between the penalties. On one hand, this result can be viewed as a further improvement on the parallel algorithm for k-MPWP given by Li et al., where the number of iterations depends on other factors. On the other hand, our result also generalizes the one solving the k-means problem presented by Bachem et al., because k-MPWP is a variant of the k-means problem. Moreover, we present a numerical experiment to show the effectiveness of the parallel algorithm for k-means with penalties.  相似文献   
87.
88.
Investigation on the miniaturized parallel multichannel-based devices packed with glass beads to improve the mass exchange execution is the critical focal point of the current study. One of the essential parameters to specify the miniaturized devices' flow distribution is the residence time distribution (RTD). In the present context, the RTDs of a liquid tracer were investigated for the air-water multiphase flows (concurrent) across the multichannel-based miniaturized devices (comprising of 11 similar dimensional parallel channels). The devices were variable in height and packed with glass beads. The conductivity estimations generated the RTD curves and were addressed by the axial dispersion model (ADM). The fluid-flow rates differed within the range of 5–23 ml min−1. The axial dispersion coefficients and the rate of the specific energy dispersion were investigated. The effects of pressure difference and geometry on the hydrodynamic attributes and mixing properties were well-illustrated, and the new correlations were suggested.  相似文献   
89.
90.
给出螺旋面钻尖刃磨机床的基本结构及其工作原理。采用Pro/E对零部件进行三维参数化建模。在此基础上进行虚拟装配包括定义运动副连接、设置伺服电机,完成螺旋面钻尖刃磨机床的装配体模型。最后通过此模型利用Mechanism模块实现螺旋面钻尖刃磨的运动仿真,并完成干涉检查、速度等运动分析。  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