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   9219篇
  免费   912篇
  国内免费   478篇
电工技术   660篇
综合类   540篇
化学工业   1551篇
金属工艺   433篇
机械仪表   496篇
建筑科学   661篇
矿业工程   236篇
能源动力   282篇
轻工业   670篇
水利工程   234篇
石油天然气   289篇
武器工业   97篇
无线电   1100篇
一般工业技术   1314篇
冶金工业   665篇
原子能技术   121篇
自动化技术   1260篇
  2024年   34篇
  2023年   155篇
  2022年   283篇
  2021年   397篇
  2020年   336篇
  2019年   292篇
  2018年   290篇
  2017年   320篇
  2016年   339篇
  2015年   397篇
  2014年   512篇
  2013年   706篇
  2012年   671篇
  2011年   662篇
  2010年   554篇
  2009年   538篇
  2008年   525篇
  2007年   495篇
  2006年   403篇
  2005年   354篇
  2004年   233篇
  2003年   235篇
  2002年   261篇
  2001年   229篇
  2000年   146篇
  1999年   137篇
  1998年   129篇
  1997年   89篇
  1996年   88篇
  1995年   61篇
  1994年   56篇
  1993年   43篇
  1992年   37篇
  1991年   37篇
  1990年   24篇
  1989年   28篇
  1988年   23篇
  1987年   25篇
  1986年   27篇
  1985年   28篇
  1984年   30篇
  1983年   22篇
  1982年   29篇
  1981年   24篇
  1979年   23篇
  1978年   24篇
  1976年   15篇
  1975年   22篇
  1974年   28篇
  1966年   15篇
排序方式: 共有10000条查询结果,搜索用时 78 毫秒
1.
Elevated activation of the autophagy pathway is currently thought to be one of the survival mechanisms allowing therapy-resistant cancer cells to escape elimination, including for cytarabine (AraC)-resistant acute myeloid leukemia (AML) patients. Consequently, the use of autophagy inhibitors such as chloroquine (CQ) is being explored for the re-sensitization of AraC-resistant cells. In our study, no difference in the activity of the autophagy pathway was detected when comparing AraC-Res AML cell lines to parental AraC-sensitive AML cell lines. Furthermore, treatment with autophagy inhibitors CQ, 3-Methyladenine (3-MA), and bafilomycin A1 (BafA1) did not re-sensitize AraC-Res AML cell lines to AraC treatment. However, in parental AraC-sensitive AML cells, treatment with AraC did activate autophagy and, correspondingly, combination of AraC with autophagy inhibitors strongly reduced cell viability. Notably, the combination of these drugs also yielded the highest level of cell death in a panel of patient-derived AML samples even though not being additive. Furthermore, there was no difference in the cytotoxic effect of autophagy inhibition during AraC treatment in matched de novo and relapse samples with differential sensitivity to AraC. Thus, inhibition of autophagy may improve AraC efficacy in AML patients, but does not seem warranted for the treatment of AML patients that have relapsed with AraC-resistant disease.  相似文献   
2.
3.
4.
5.
6.
The effect of charge on the dihydrogen storage capacity of Sc2–C6H6 has been investigated at B3LYP-D3/6-311G(d,p) level. The neutral system Sc2–C6H6 can store 8H2 with gravimetric density of 8.76 wt %, and one H2 dissociates and bonds atomically on the scandium atom. The adsorption of 8H2 on Sc2–C6H6 is energetically favorable below 155 K. The atom-centered density matrix propagation (ADMP) molecular dynamics simulations show that Sc2–C6H6 can adsorb 3H2 within 1000 fs at 300K. Compared with Sc2–C6H6, the charged systems can adsorb more hydrogen molecules with higher gravimetric density, and all the H2 are adsorbed in the molecular form. The gravimetric densities of Sc2–C6H6+ and Sc2–C6H62+ are 9.75 and 10.71 wt%. Moreover, the maximum adsorption of charged systems are favorable in wider temperature range. Most importantly, the ADMP-MD simulations indicate that Sc2–C6H62+ can adsorb 6 hydrogen molecules within 1000 fs at 300K. It can be found that the gravimetric density (6.72 wt%) of Sc2–C6H62+ still exceeds the target of US Department of Energy (DOE) under ambient conditions.  相似文献   
7.
Analog Integrated Circuits and Signal Processing - Fault diagnosis of analog circuit is critical to improve safety and reliability in electrical systems and reduce losses. Traditional fault...  相似文献   
8.
This paper examines what influences trust in mobile social commerce environment. Drawing on trust-based acceptance model (i.e. cognitive and emotional trust) and online review features (i.e. profile photo, linguistic style, and reported experience), we examine how these factors affect trust in mobile social commerce. Hypotheses were tested using survey data. The results of our model showed that there are significant influences of profile photo, reported experience, cognitive, and emotional trust towards trust in ms-commerce. This work contributes to existing literature by examining the roles of previous trust in mobile payments and online reviews on trust in mobile social commerce.  相似文献   
9.
The recent advancement in high- performance semiconductor packages has been driven by the need for higher pin count and superior heat dissipation. A one-piece cavity lid flip chip ball grid array (BGA) package with high pin count and targeted reliability has emerged as a popular choice. The flip chip technology can accommodate an I/O count of more than five hundreds500, and the die junction temperature can be reduced to a minimum level by a metal heat spreader attachment. None the less, greater expectations on these high-performance packages arose such as better substrate real estate utilization for multiple chips, ease in handling for thinner core substrates, and improved board- level solder joint reliability. A new design of the flip chip BGA package has been looked into for meeting such requirements. By encapsulating the flip chip with molding compound leaving the die top exposed, a planar top surface can be formed. A, and a flat lid can then be mounted on the planar mold/die top surface. In this manner the direct interaction of the metal lid with the substrate can be removed. The new package is thus less rigid under thermal loading and solder joint reliability enhancement is expected. This paper discusses the process development of the new package and its advantages for improved solder joint fatigue life, and being a multichip package and thin core substrate options. Finite-element simulations have been employed for the study of its structural integrity, thermal, and electrical performances. Detailed package and board-level reliability test results will also be reported  相似文献   
10.
介绍了具有相同音频、视频编码方式的MPEG - 2节目流如何合并成一个节目流。合并后的文件播放流畅并且时间显示正确 ,它包括PATPMT表的重写 ,系统头部分相关字段的更改 ,PCR值的修改 ,解码时间标签 (DTS)和显示时间标签 (PTS)的重新确定 ,传送速率的修改以及添加相应的空包  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