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   847995篇
  免费   11934篇
  国内免费   2854篇
电工技术   15512篇
技术理论   1篇
综合类   865篇
化学工业   127192篇
金属工艺   32206篇
机械仪表   24056篇
建筑科学   21652篇
矿业工程   3047篇
能源动力   23958篇
轻工业   79195篇
水利工程   7614篇
石油天然气   11719篇
武器工业   44篇
无线电   100041篇
一般工业技术   158242篇
冶金工业   168866篇
原子能技术   14873篇
自动化技术   73700篇
  2021年   6911篇
  2020年   5131篇
  2019年   6480篇
  2018年   10696篇
  2017年   10475篇
  2016年   11260篇
  2015年   8065篇
  2014年   13259篇
  2013年   39332篇
  2012年   21766篇
  2011年   30496篇
  2010年   24219篇
  2009年   27162篇
  2008年   28310篇
  2007年   27916篇
  2006年   24911篇
  2005年   22762篇
  2004年   21854篇
  2003年   21688篇
  2002年   20776篇
  2001年   20887篇
  2000年   19316篇
  1999年   20855篇
  1998年   53272篇
  1997年   37348篇
  1996年   28704篇
  1995年   21548篇
  1994年   18824篇
  1993年   18494篇
  1992年   13254篇
  1991年   12621篇
  1990年   12042篇
  1989年   11684篇
  1988年   11165篇
  1987年   9572篇
  1986年   9449篇
  1985年   10976篇
  1984年   10161篇
  1983年   9045篇
  1982年   8478篇
  1981年   8677篇
  1980年   8133篇
  1979年   7750篇
  1978年   7414篇
  1977年   9115篇
  1976年   12286篇
  1975年   6448篇
  1974年   6069篇
  1973年   6230篇
  1972年   5040篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
This paper describes techniques for the on-chip measurement of high-frequency and/or high-bandwidth electrical phenomena in ultra large-scale integration environments. The techniques rely on the integration of multiple compact and robust electronic test devices, or cores, at various locations within an integrated circuit. The cores consist primarily of signal generators that approximate the output of a sigma-delta modulator using finite repetitious bit patterns and a small set of highly robust analog components. They are capable of digitizing on-chip signals at gigahertz rates even using low-cost manufacturing processes. Simple communication between the multiple cores enables the migration of many "board-level" type measurements down to the chip level.  相似文献   
82.
83.
84.
Gas/liquid mass transfer has been investigated using a stirred vessel gas/liquid contactor using non‐Newtonian media and carbon dioxide as absorbent and gas phase, respectively. The volumetric mass transfer coefficients at different operational variables have been determined. Non‐Newtonian media (liquid phase) were prepared as aqueous solutions of sodium carboxymethyl cellulose salt. The influence of the rheological properties, polymer concentration, stirring rate, and gas flow rate on mass transfer was studied for these liquid phases. Kinematic viscosity and density experimental data were used to calculate the average molecular weight corresponding to the polymer employed. The Ostwald model has been used to fit the rheological behavior of aqueous solutions of the polymer employed as absorbent phase. Reasonably good agreement was found between the predictions of the proposed models and the experimental data of mass transfer coefficients.  相似文献   
85.
86.
This article investigates the asymptotic performance of single parity-check (SPC) product codes (PCs) from a decoding point of view. Specifically, the probability of bit error is bounded before and after the decoding of each dimension, similar to the analysis of "iterated codes" by Elias (1954). It is shown that the asymptotic probability of bit error can be driven to zero as the number of dimensions, and hence the block length, increases at signal-to-noise ratios (SNRs) within 2 dB of capacity over the additive white Gaussian noise (AWGN) channel.  相似文献   
87.
K. M. Granstr  m 《Drying Technology》2003,21(7):1197-1214
This paper describes a novel method to measure emission from dryers. The method resolves the known difficulties caused by diffuse emissions, and also solves the problems associated with high moisture content of the drying medium. The basic idea is to use water vapor to determine the exhaust flow, while a dry ice trap is used both to preconcentrate emitted VOCs and to determine the moisture content of the drying medium.  相似文献   
88.
A new mobile robot control approach via fusion of control signals.   总被引:3,自引:0,他引:3  
This paper proposes an alternative approach to address the problem of coordinating behaviors in mobile robot navigation: fusion of control signals. Such approach is based on a set of two decentralized information filters, which accomplish the data fusion involved. Besides these two fusion engines, control architectures designed according to this approach also embed a set of different controllers that generate reference signals for the robot linear and angular speeds. Such signals are delivered to the two decentralized information filters, which estimate suitable overall reference signals for the robot linear and angular speeds, respectively. Thus, the background for designing such control architectures is provided by the nonlinear systems theory, which makes this approach different from any other yet proposed. This background also allows checking control architectures designed according to the proposed approach for stability. Such analysis is carried out in the paper, and shows that the robot always reaches its final destination, in spite of either obstacles along its path or the environment layout. As an example, a control architecture is designed to guide a mobile robot in an experiment, whose results allows checking the good performance of the control architecture and validating the design approach proposed as well.  相似文献   
89.
90.
PNNI-based control plane for automatically switched optical networks   总被引:1,自引:0,他引:1  
Much effort has been spent on the definition of control plane protocols for automatically switched optical networks (ASON). Most of the proposals brought into the standardization for an International Telecommunications Union-Telecommunication Sector, Internet Engineering Task Force, and Optical Internetworking Forum are based on Internet protocol concepts. One such proposal is the generalized multi-protocol label switching (GMPLS), an extension of the MPLS traffic engineering control plane model that includes nonpacket switched technologies (time, wavelength, and fiber switching). Recently, the potential use of private network-network interface (PNNI) in ASONs has been discussed as an alternative proposal by the standardization bodies. The goal of this paper is to appropriately adapt asynchronous transfer mode into an optical PNNI (O-PNNI) protocol that can be used as the control plane of ASONs. The paper also provides a critical viewpoint on the potential usage of either O-PNNI or GMPLS control plane and analyzes the pros and cons of each. The methodology adopted toward devising O-PNNI hinges on reviewing PNNI along with ASON recommendations in order to determine the set of PNNI features that require adaptation. Having identified these features we engineer and present appropriate solutions relating to routing, signaling and addressing aspects.  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