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   642篇
  免费   44篇
电工技术   13篇
化学工业   158篇
金属工艺   5篇
机械仪表   3篇
建筑科学   18篇
矿业工程   2篇
能源动力   21篇
轻工业   83篇
水利工程   10篇
石油天然气   7篇
无线电   91篇
一般工业技术   92篇
冶金工业   42篇
自动化技术   141篇
  2024年   2篇
  2023年   12篇
  2022年   16篇
  2021年   34篇
  2020年   23篇
  2019年   15篇
  2018年   23篇
  2017年   21篇
  2016年   18篇
  2015年   17篇
  2014年   18篇
  2013年   56篇
  2012年   43篇
  2011年   48篇
  2010年   35篇
  2009年   28篇
  2008年   35篇
  2007年   31篇
  2006年   26篇
  2005年   21篇
  2004年   20篇
  2003年   14篇
  2002年   17篇
  2001年   7篇
  2000年   3篇
  1999年   8篇
  1998年   19篇
  1997年   10篇
  1996年   6篇
  1995年   2篇
  1994年   3篇
  1993年   9篇
  1992年   3篇
  1990年   2篇
  1989年   4篇
  1986年   4篇
  1984年   2篇
  1983年   2篇
  1981年   4篇
  1980年   3篇
  1978年   1篇
  1977年   3篇
  1976年   4篇
  1975年   3篇
  1972年   1篇
  1971年   2篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
  1964年   1篇
排序方式: 共有686条查询结果,搜索用时 15 毫秒
91.
92.
93.
The glycolytic modulator TP53-Inducible Glycolysis and Apoptosis Regulator (TIGAR) is overexpressed in several types of cancer and has a role in metabolic rewiring during tumor development. However, little is known about the role of this enzyme in proliferative tissues under physiological conditions. In the current work, we analysed the role of TIGAR in primary human lymphocytes stimulated with the mitotic agent Concanavalin A (ConA). We found that TIGAR expression was induced in stimulated lymphocytes through the PI3K/AKT pathway, since Akti-1/2 and LY294002 inhibitors prevented the upregulation of TIGAR in response to ConA. In addition, suppression of TIGAR expression by siRNA decreased the levels of the proliferative marker PCNA and increased cellular ROS levels. In this model, TIGAR was found to support the activity of glucose 6-phosphate dehydrogenase (G6PDH), the first enzyme of the pentose phosphate pathway (PPP), since the inhibition of TIGAR reduced G6PDH activity and increased autophagy. In conclusion, we demonstrate here that TIGAR is upregulated in stimulated human lymphocytes through the PI3K/AKT signaling pathway, which contributes to the redirection of the carbon flux to the PPP.  相似文献   
94.
A class AB version of the conventional super source follower (SSF) is described. The circuit greatly increases slew rate (SR) and current efficiency, maintaining the low distortion and low output resistance of the SSF. Class AB operation is achieved without extra power dissipation or supply requirements, and without bandwidth or noise degradation. The circuit can advantageously replace the SSF in a wide variety of analog systems, opening a new research line in analog design. To illustrate the widespread application of this cell, a class AB differential unity‐gain buffer, a class AB differential current mirror and two class AB differential transconductors are designed, fabricated in a 0.5µm CMOS technology and tested. Measurement results using a dual supply of ±1.65V show that the proposed class AB version of the SSF improves SR by a factor 21.5 and increases bandwidth by 10%, keeping noise level, input range, power consumption, and supply requirements unaltered. The fabricated class AB current mirror features a THD at 100 kHz of ? 62dB for signal currents 20 times larger than the bias current. The fabricated transconductors feature an IM3 at 1 MHz of ? 56.6dB for output currents more than 13 times larger than the bias currents. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
95.
96.
Highly enantioselective organocatalytic domino thia‐Michael/aldol reactions between 2‐mercaptoacetophenone and α,β‐unsaturated aldehydes are presented. The reactions proceed with excellent chemo‐, diastereo‐ and enantioselectivity to give the corresponding benzothiopyran derivatives in high yields with up to >15:1 dr and 96 to >99 % ee.  相似文献   
97.
1,4-Butanediol (1,4-BDO) is a four-carbon diol used for industrial applications such as organic solvents, and the production of adhesives, fibers and polyurethanes. 1,4-BDO currently is produced through several petrochemical routes: hydrogenation of maleic anhydride, isomerization of propylene oxide, acetoxylation of butadiene, and the reaction between formaldehyde and acetylene. The current trends in 1,4-BDO production involve the utilization of renewable sources such as biomass. In this context, the present study aimed to identify promising technologies of 1,4-BDO production through prospecting methodology based on the analyses of patents and scientific article, describing the most relevant aspects of those emerging technologies. An increasing amount of 1,4-BDO production focused on biotechnological routes has been reported, with the US heavily involved in the development of new technologies. This study tracked three promising technologies which have potential for application in a biorefinery context because those processes involve (i) production of 1,4-BDO from sugars, classified herein as the biotechnological route; (ii) production of intermediates from sugar fermentation followed by catalytic conversion into 1,4-BDO, classified herein as the hybrid route, and (iii) furan/furfural conversion into 1,4-BDO. © 2020 Society of Chemical Industry  相似文献   
98.
A leading cause of death in western countries is sudden cardiac death, and can be associated with genetic disease. Next-generation sequencing has allowed thorough analysis of genes associated with this entity, including, most recently, titin. We aimed to identify potentially pathogenic genetic variants in titin. A total of 1126 samples were analyzed using a custom sequencing panel including major genes related to sudden cardiac death. Our cohort was divided into three groups: 432 cases from patients with cardiomyopathies, 130 cases from patients with channelopathies, and 564 post-mortem samples from individuals showing anatomical healthy hearts and non-conclusive causes of death after comprehensive autopsy. None of the patients included had definite pathogenic variants in the genes analyzed by our custom cardio-panel. Retrospective analysis comparing the in-house database and available public databases also was performed. We identified 554 rare variants in titin, 282 of which were novel. Seven were previously reported as pathogenic. Of these 554 variants, 493 were missense variants, 233 of which were novel. Of all variants identified, 399 were unique and 155 were identified at least twice. No definite pathogenic variants were identified in any of genes analyzed. We identified rare, mostly novel, titin variants that seem to play a potentially pathogenic role in sudden cardiac death. Additional studies should be performed to clarify the role of these variants in sudden cardiac death.  相似文献   
99.
100.
Ihling  Heiko  Petzold  Ramon 《Grundwasser》2020,25(4):285-299
Grundwasser - Im Untersuchungsgebiet Schleinitz führte eine Grünlandumnutzung einer ehemaligen Ackerfläche über einen Zeitraum von annähernd 6 Jahren zu einer...  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