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   1572篇
  免费   104篇
  国内免费   12篇
电工技术   23篇
综合类   34篇
化学工业   273篇
金属工艺   61篇
机械仪表   108篇
建筑科学   45篇
矿业工程   6篇
能源动力   64篇
轻工业   146篇
水利工程   11篇
石油天然气   20篇
无线电   245篇
一般工业技术   352篇
冶金工业   119篇
原子能技术   9篇
自动化技术   172篇
  2023年   20篇
  2022年   12篇
  2021年   49篇
  2020年   36篇
  2019年   46篇
  2018年   43篇
  2017年   60篇
  2016年   38篇
  2015年   34篇
  2014年   81篇
  2013年   103篇
  2012年   112篇
  2011年   110篇
  2010年   78篇
  2009年   90篇
  2008年   75篇
  2007年   69篇
  2006年   70篇
  2005年   53篇
  2004年   32篇
  2003年   44篇
  2002年   48篇
  2001年   35篇
  2000年   30篇
  1999年   29篇
  1998年   51篇
  1997年   46篇
  1996年   38篇
  1995年   23篇
  1994年   23篇
  1993年   15篇
  1992年   19篇
  1991年   10篇
  1990年   12篇
  1989年   7篇
  1988年   4篇
  1987年   6篇
  1986年   2篇
  1985年   6篇
  1984年   4篇
  1983年   3篇
  1980年   2篇
  1978年   3篇
  1977年   3篇
  1976年   3篇
  1974年   4篇
  1972年   1篇
  1971年   1篇
  1968年   1篇
  1944年   1篇
排序方式: 共有1688条查询结果,搜索用时 922 毫秒
81.
With the introduction of multichannel video programming distributors and different types of video platforms, consumers have more choices of channels and platforms than ever. Specifically, the present study focuses on television and the Internet as video platforms.  相似文献   
82.
<正>The first tier of automotive manufacturers has faced to pressures about move,modify,updating tasks for manufacturing resources in production processes from demand response of production order sequence for motor company and process innovation purpose for productivity. For meets this requirements,it has to require absolutely lead time to re-wiring of physical interface for production equipment,needs for change existing program and test over again.For prepare this constraints,it needs studying an auto-configuration functions that build for both visibility and flexibility based on the 4M(Man,Machine,Material, Method)group management which is supports from WSN (Wireless Sensor Network)of the open embedded device called M2M(Machine to Machine)and major functions of middleware including point manager for real-time device communication,real-time data management,Standard API (Application Program Interface)and application template management.To be application system to RMS (Reconfigurable Manufacturing System)for rapidly response from various orders and model from motor company that is beginning to establishing the mapping of manufacturing resources of 4M using WSN.  相似文献   
83.
In this letter, we propose a data randomization scheme for endurance and interference mitigation of deeply‐scaled multilevel flash memory. We address the relationships between data patterns and the raw bit error rate. An on‐chip pseudorandom generator composed of an address‐based seed location decoder is developed and evaluated with respect to uniformity. Experiments performed with 2x‐nm and 4x‐nm NAND flash memory devices illustrate the effectiveness of our scheme. The results show that the error rate is reduced up to 86% compared to that of a conventional cycling scheme. Accordingly, the endurance phenomenon can be mitigated through analysis of interference that causes tech shrinkage.  相似文献   
84.
A novel method is proposed for enhancing the mixing performance in a crisscross micromixer by means of aperiodic time-varying electrokinetic perturbing flows. In the proposed approach, the aperiodic oscillating source used to modulate the perturbing electric potential is derived using the Sprott system. The effects of the perturbation conditions and micromixer geometry parameters on the fluid flow characteristics and mixing performance are analyzed by means of numerical simulations. The results show that irregularly-alternating flow recirculation structures are induced within the lateral channels of the micromixer, which cause a repeated stretching and folding of the species streams in the main channel and enhance the mixing performance as a result. It is shown that an effective improvement in the mixing performance can be obtained through a suitable specification of the scaling factor in the Sprott system. Furthermore, it is shown that the mixing performance can be further enhanced by assigning suitable values to the micromixer geometry parameters or by reducing the ratio of the main channel flow velocity to the lateral channel flow velocity. Overall, the numerical results show that an average mixing efficiency of more than 90% can be obtained by specifying the scaling factor in the Sprott system as 7.5, the ratio of the main channel velocity to the lateral channel velocity as 0.25, the separation distance between the lateral channels as equal to half the width of the main channel, and the width of the lateral channels as equal to the width of the main channel.  相似文献   
85.
Artemisia lavandulaefolia has been utilized in traditional medicines for the treatment of several diseases. In this study, we attempted to determine whether the essential oil and 1,8-cineole of A. lavandulaefolia induce apoptosis in KB cells. The oil and 1,8-cineole induced the cell death of KB cells as evidenced by the increased cell population in the sub-G1 phase, the appearance of condensed and/or fragmented nuclei, and the generation of a cleaved PARP product. The treatment of the cells with the oil also induced changes in the mitochondrial level of Bcl-2 and Bax, thereby inducing the release of cytochrome c into the cytosol. Furthermore, the oil increased the phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase, and p38 MAPK, but 1,8-cineole activated pp38 and pJNK at the same concentrations. These findings show that the mitochondrial and MAPKs pathways might be involved in the oil-induced apoptosis, and may enhance our current understanding of the anticancer functions of the oil to a greater degree than 1,8-cineole.  相似文献   
86.
In the present study, surface texture features and chemical properties of two types of cokes, made from coal tar by either 1-stage heat treatment or 2-stage heat treatment, were researched. The relationship between surface texture characteristics and the chemical properties was identified through molecular weight distribution, insolubility of coal tar, weight loss with temperature increase, coking yield, and polarized light microscope analysis. Rapidly cleared anisotropy texture in cokes was observed in accordance with the coking temperature rise. Quinoline insolubility and toluene insolubility of coal tar increased with a corresponding increases in coking temperature. In particular, the cokes produced by the 2-stage heat treatment (2S-C) showed surface structure of needle cokes at a temperature approximately 50°C lower than the 1-stage heat treatment (1S-C). Additionally, the coking yield of 2S-C increased by approximately 14% in comparison with 1S-C.  相似文献   
87.
本文阐述了构建安全体系结构的意义,以及安全体系结构所包括的主要内容.重点以企业网为例介绍了应当如何根据自身实际,以安全体系为指导,构建其安全防护体系.  相似文献   
88.
A micro-viscometer for measuring viscosity change in small amount of liquid in real time has been proposed recently. The advantages of the device are the use of minimal liquid and maximized sensitivity for measuring viscosity. However, in previous research, even though the multi-physical simulation including electrical, mechanical, and acoustical phenomenon is necessary for design of micro-viscometer, only acoustical aspects have been considered. Thus, combined physical phenomena could not be reflected for an optimum design process. In this research, a multi-physical approach is developed for designing a micro-viscometer, and an optimized micro-viscometer design is proposed. The proposed method is able to capture multi-physical phenomena such as near field effect and added mass effect. It also has the advantage of flexible design of various shape and materials, leading to savings of cost and time.  相似文献   
89.
本文对在填困区一和布克赛尔县沙尔布尔山地区发现的铜矿化点的地质概况、矿物组合及地化元素组合特征进行了初步研究,并对矿化规律及矿化标志提出了认识,为今后进一步开展找矿工作提供依据.  相似文献   
90.
对于重积分的计算(主要是二重积分和三重积分的计算),在《数学分析》和《高等数学》的教科书中都有讲述。本文提出一种不用画几何图形而用解不等式组的代数方法,此法对n(n≥3)重积分和变更单积分的顺序更为有效。  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