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   1994篇
  免费   80篇
电工技术   38篇
综合类   3篇
化学工业   380篇
金属工艺   22篇
机械仪表   34篇
建筑科学   76篇
矿业工程   4篇
能源动力   40篇
轻工业   146篇
水利工程   18篇
石油天然气   3篇
无线电   287篇
一般工业技术   319篇
冶金工业   234篇
原子能技术   18篇
自动化技术   452篇
  2021年   32篇
  2020年   17篇
  2019年   27篇
  2018年   33篇
  2017年   45篇
  2016年   43篇
  2015年   44篇
  2014年   66篇
  2013年   109篇
  2012年   98篇
  2011年   111篇
  2010年   91篇
  2009年   100篇
  2008年   113篇
  2007年   83篇
  2006年   95篇
  2005年   83篇
  2004年   78篇
  2003年   77篇
  2002年   54篇
  2001年   34篇
  2000年   31篇
  1999年   41篇
  1998年   53篇
  1997年   33篇
  1996年   36篇
  1995年   24篇
  1994年   28篇
  1993年   33篇
  1992年   22篇
  1991年   16篇
  1990年   13篇
  1989年   13篇
  1988年   18篇
  1987年   19篇
  1986年   23篇
  1985年   19篇
  1984年   16篇
  1983年   16篇
  1982年   15篇
  1981年   17篇
  1980年   11篇
  1979年   14篇
  1978年   10篇
  1977年   12篇
  1976年   20篇
  1975年   12篇
  1974年   8篇
  1973年   13篇
  1972年   9篇
排序方式: 共有2074条查询结果,搜索用时 343 毫秒
11.
Presents results of 3 studies on the psychometric properties of the LP-ABC (M. Loranger and M. Pépin, 1993), a French-language instrument for assessing general functioning in adults with mental retardation. The studies involved a total of 299 male and female Canadian adults with mental retardation. Results confirm the internal consistency, construct validity, criterion validity, discriminant validity, interrater reliability, and test–retest reliability of the LP-ABC. (English abstract) (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
12.
A directionally solidified eutectic (DSE) of MnO-ZrO2 has been investigated using a variety of electron optical techniques. It is found that considerable MnO goes into ZrO2 to form a substitutional solid solution. About 14 wt% of MnO is soluble in ZrO2 close to the eutectic temperature. The solubility of ZrO2 in MnO, however, is quite low, less than 0.50 wt%. Electron diffraction experiments indicate that ZrO2 (MnO) has the cubic fluorite structure. Diffuse scattering, similar to other cubic zirconias (e.g., CaO, MgO stabilized zirconia), is also observed in manganese-stabilized zirconia. Diffuse scattering indicates the presence of oxygen vacancies and thus confirms the defect nature of the fluorite structure. Electron energy loss spectrometry (EELS) fine structure analysis of the Mn L23 edge provided clear evidence that Mn is present as Mn2+ in Mn-stabilized cubic ZrO2.  相似文献   
13.
The effect of a range of organic additives on the thermal stability of poly(vinyl chloride), both with and without a chloroparaffin extender, was studied using a number of experimental techniques. Of the additives used the best overall balance was provided by pentaerythritol, which increased stability when the extender was present and had no effect when it was absent. The congo red test emerged as the most suitable technique, being consistent and inexpensive and able to screen several additives simultaneously. Isothermal differential thermal analysis correlated with the congo red test but required more expensive equipment, was time-consuming and demanded good mixing of the poly(vinyl chloride) compound to give reproducible results. Thermogravimetry was not sufficiently sensitive and the heat stability test was the least useful of all.  相似文献   
14.
The existence of an SH-wave incidence angle for which the reflected amplitude is zero (SH-wave intromission angle) is established for the case of plane-wave scattering by a planar interface joining two homogeneous, isotropic, and linearly elastic half-spaces. Such an incidence angle is numerically shown to exist for two combinations of bimaterial interface properties. The SH-wave intromission angle is roughly parallel to the electromagnetic Brewster angle and the acoustic P-wave intromission angle, and the concept should find new applications for non-intrusive characterization of interfaces.  相似文献   
15.
CuyKewney 《个人电脑》2004,10(12):88-88
PC的安全威胁日益严重,我们可能永远赢不了这场战争。  相似文献   
16.
This paper presents a new massively parallel MIMD architecture, halfway between the Connection Machine and hypercubes based on 32-bit processors. It is built from specific 8-bit processors arranged in a 2-D grid and communicating by message transfers. We discuss the communication problems, the instruction set of the basic processing unit, the programmation of the whole array and the use of a high level data-flow language.  相似文献   
17.
The lack of interoperable (and thus standardized) solutions is stalling the deployment of advanced multimedia packaging and distribution applications although most of the individual technologies are indeed already present. This motivated MPEG (ISO/IEC JTCl SC29 WGI I) in June 2000 to start working on the definition of enabling normative technology for the multimedia applications of the 21st century: MPEG-21 "Multimedia Framework." MPEG-21's approach is to define a framework to support transactions that are interoperable and highly automated, specifically taking into account digital rights management (DRM) requirements and targeting multimedia access and delivery using heterogeneous networks and terminals. This article first outlines the context and background of the MPEG-21 initiative. Then, an overview of MPEG-21 technology is given. Subsequently, it is discussed how MPEG-21 can provide solutions for universal multimedia access (UMA). UMA is also one of the use cases that has led to the creation of a new part in MPEG-21 dealing with digital item adaptation. Finally, this article concludes with an overview of MPEG-21 related activities and an outlook on future developments.  相似文献   
18.
19.
This paper presents the architecture of a new space priority mechanism intended to control cell loss in ATM switches. Our mechanism is a new generic concept called: the multiple pushout. It is based on the utilization of both AAL and ATM features and on a particular definition of the priority bit. Whenever one cell of a message overflows the buffer of an ATM switch, the algorithm causes the switch to discard other cells of the message (including later arrivals). Such discarding frees buffer spaces for cells of other messages that have a chance of arriving at their destination intact. Our objective is to emphasize that in case of overload, with most of proposed mechanisms, cells are discarded without any semantic information about the type of cells. Therefore, at the destination, all the fragments of the corrupted messages will be discarded anyway. Finally, we present simulation results comparing cell loss rates and message loss rates of several space priority mechanisms.  相似文献   
20.
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