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   104128篇
  免费   7203篇
  国内免费   2788篇
电工技术   3950篇
技术理论   3篇
综合类   3775篇
化学工业   19890篇
金属工艺   5202篇
机械仪表   6739篇
建筑科学   4925篇
矿业工程   1627篇
能源动力   3626篇
轻工业   8529篇
水利工程   1173篇
石油天然气   3024篇
武器工业   434篇
无线电   13853篇
一般工业技术   17259篇
冶金工业   6682篇
原子能技术   1206篇
自动化技术   12222篇
  2024年   347篇
  2023年   1578篇
  2022年   2813篇
  2021年   4219篇
  2020年   3050篇
  2019年   2900篇
  2018年   3233篇
  2017年   3310篇
  2016年   3485篇
  2015年   3769篇
  2014年   5110篇
  2013年   6603篇
  2012年   7039篇
  2011年   8064篇
  2010年   6203篇
  2009年   6267篇
  2008年   6106篇
  2007年   5144篇
  2006年   4918篇
  2005年   3865篇
  2004年   3072篇
  2003年   2776篇
  2002年   2507篇
  2001年   2140篇
  2000年   1971篇
  1999年   1934篇
  1998年   2360篇
  1997年   1711篇
  1996年   1430篇
  1995年   1093篇
  1994年   865篇
  1993年   693篇
  1992年   526篇
  1991年   483篇
  1990年   428篇
  1989年   397篇
  1988年   308篇
  1987年   255篇
  1986年   178篇
  1985年   165篇
  1984年   129篇
  1983年   100篇
  1982年   68篇
  1981年   67篇
  1980年   62篇
  1979年   49篇
  1978年   45篇
  1977年   46篇
  1976年   75篇
  1973年   32篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
ElectronmicroscopicobservationsandDNAchainfragmentationstudiesonapoptosisinbonetumorcelsinducedby153SmEDTMPZhuShouPeng,Xia...  相似文献   
82.
Image flow segmentation and estimation using displaced spatial gradient   总被引:2,自引:0,他引:2  
Kim  Y.-H. Kim  S.D. 《Electronics letters》1992,28(24):2213-2215
There are two main causes of inaccuracies in estimating image flows using gradient based techniques. One is the erroneous measurement of gradients in brightness and the other is the blurring of motion boundaries which is caused by the smoothness constraint. In the Letter, the gradient measurement error of conventional methods is analysed and a new technique based on this analysis proposed.<>  相似文献   
83.
84.
85.
86.
This study employs a relational dialectics approach to gain insights into the nature of relational communication via Cyworld , a Korean social network site. Qualitative analysis of in-depth interview data from 49 users suggests that Cyworld users routinely negotiate multiple dialectical tensions that are created within the online world, transferred from face-to-face contexts, or imposed by interpersonal principles that relate to Korea's collectivistic culture. The interviewees experienced a new relational dialectic of interpersonal relations versus self-relation, analogous to Baxter and Montgomery's (1996) connection-autonomy contradiction. Their responses suggest that Cyworld's design features and functions encourage users to transcend the high-context communication of Korean culture by offering an alternative channel for elaborate and emotional communication, which fosters the reframing of relational issues offline. Cy-Ilchons (online buddies) virtually extend the Korean cultural concept of blood ties, called yons, in ways that intensify the openness-closedness contradiction at early stages of relationship formation.  相似文献   
87.
Density-Induced Support Vector Data Description   总被引:6,自引:0,他引:6  
  相似文献   
88.
In this letter, we examined whether the parasitic bipolar junction transistors (BJTs) in the MOSFET fabricated by the standard CMOS process can play a role as a fluorescence detector. To suppress the action of two vertical parasitic BJTs, the gate and n-well were tied in the parasitic BJTs, and the body node was connected to the drain. The proposed device was compared with the inherent and the parasitic diodes in the MOSFET. It had 100 times higher photocurrents than the diodes in the MOSFET. In addition, it was applied for the detection of the fluorescent signal, and could detect near 10 nM of Alexa 546. Therefore, CMOS-process-compatible parasitic BJTs can be used as a photodetector in an integrated fluorescence detector.  相似文献   
89.
Thermal stratification, cycling, and striping phenomena have drawn much attention recently because of the incidents at several nuclear plants that raised significant safety concerns. The concerns due to these phenomena relate to thermal fatigue in branch pipes connected to the main coolant piping. Nuclear utility industry is addressing the issue with the aim to understand the mechanisms that lead to fatigue in nominally stagnant piping systems near the reactor coolant piping. Two key results from this effort are described in this paper. First, tests to investigate the interaction between the main coolant piping and the stagnant attached lines by turbulence penetration are described and a working correlation is obtained. Turbulence penetration into unisolable lines, or the transport of turbulence into stagnant piping from the reactor coolant system (RCS) line, represents a mechanism for carrying hot RCS water into regions filled with cold water. The possibility of stratification of the two fluids (and the resultant thermal stresses) is the reason for developing an understanding of the turbulence penetration process. Secondly, results of an evaluation to develop a loading definition for thermal striping are included. Based on this testing several important conclusions relating to fatigue in nominally static reactor coolant systems are reached.  相似文献   
90.
The low temperature (100°C) deposition of Sc2O3 or MgO layers is found to significantly increase the output power of AlGaN/GaN HEMTs. At 4 GHz, there was a better than 3 dB increase in output power of 0.5×100 μm2 HEMTs for both types of oxide passivation layers. Both Sc2 O3 and MgO produced larger output power increases at 4 GHz than conventional plasma-enhanced chemical vapor deposited (PECVD) SiNx passivation which typically showed ⩽2 dB increase on the same types of devices. The HEMT gain also in general remained linear over a wider input power range with the Sc2O3 or MgO passivation. These films appear promising for reducing the effects of surface states on the DC and RF performance of AlGaN/GaN HEMTs  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