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   208070篇
  免费   15341篇
  国内免费   7809篇
电工技术   11245篇
技术理论   14篇
综合类   11214篇
化学工业   35717篇
金属工艺   10538篇
机械仪表   11999篇
建筑科学   16412篇
矿业工程   4942篇
能源动力   5849篇
轻工业   12693篇
水利工程   3211篇
石油天然气   11073篇
武器工业   1345篇
无线电   25484篇
一般工业技术   26726篇
冶金工业   13185篇
原子能技术   2114篇
自动化技术   27459篇
  2024年   881篇
  2023年   3262篇
  2022年   5829篇
  2021年   7927篇
  2020年   5798篇
  2019年   5019篇
  2018年   5414篇
  2017年   6200篇
  2016年   5693篇
  2015年   7293篇
  2014年   9521篇
  2013年   12271篇
  2012年   12228篇
  2011年   13871篇
  2010年   11612篇
  2009年   11462篇
  2008年   10873篇
  2007年   10468篇
  2006年   10858篇
  2005年   9632篇
  2004年   6564篇
  2003年   5780篇
  2002年   5252篇
  2001年   4723篇
  2000年   4868篇
  1999年   5691篇
  1998年   5973篇
  1997年   4737篇
  1996年   4223篇
  1995年   3447篇
  1994年   2898篇
  1993年   2306篇
  1992年   1717篇
  1991年   1303篇
  1990年   1041篇
  1989年   915篇
  1988年   716篇
  1987年   516篇
  1986年   419篇
  1985年   362篇
  1984年   212篇
  1983年   204篇
  1982年   174篇
  1981年   164篇
  1980年   154篇
  1979年   97篇
  1978年   69篇
  1977年   129篇
  1976年   217篇
  1975年   44篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
The impacts of CVD tungsten polycide (WSix) on MOSFET performance and reliability are studied in this letter. The WSix process is shown to enhance the S/D lateral extent for both N- and P-channel devices via CGD and Leff measurements, confirming previous suspicion. This enhanced S/D extent is found to be easily modulated by drain-to-gate bias, which is favorable for achieving both higher drive currents and higher S/D punch-through voltages than those of non-WSix devices. Both electron and hole mobility for the WSix device are also slightly higher and closer to the published data compared to the non-WSix case. These effects together yield about >5% improvement for nMOSFET and >10% improvement for pMOSFET in drive current at a given punch-through voltage. The channel hot-electron lifetime for the n-channel WSix device is about 10 times higher than that of the non-WSix one. These enhancements in both performance and reliability make the WSix device very attractive fog VLSI CMOS technologies  相似文献   
92.
93.
In recent years industries have increasingly used customer relationship labor in management as a tool to improve their position in the marketplace. This research involves using a data warehouse, decision-tree-based data mining, and neural network pattern classification analysis to isolate the causes of non-conformity in IC packaging. The correctness of the classification analysis produced using the two methods is compared. Our objective is to establish an information analysis system, that is able to quickly identify the causes of problems thereby reducing the time taken to solve quality-related problems. It is shown that predictions made about the target group using decision tree analysis are more accurate than those made by neural network classification, indicating that decision tree analysis is an effective means of classification analysis of a company's quality problems.  相似文献   
94.
因场地淤泥等软土层深厚,在填方荷载作用下,软弱土层产生固结沉降,引起局部构筑物的不均匀沉降,发生结构破坏。采用微型灌注桩加固满足现场各个限制条件的要求,达到了加固目的。  相似文献   
95.
96.
Acrylonitrile–butadiene–styrene (ABS)/montmorillonite nanocomposites have been prepared using a direct melt intercalation technique by blending ABS and organophilic clay of two different particle sizes: OMTa (5 µm) and OMTb (38 µm). Their structure and flammability properties were characterized by X‐ray diffraction, high resolution electronic microscopy (HREM), thermogravimetric analysis (TGA) and cone calorimeter experiments. The results of HREM showed that ABS/5 wt% OMTa nanocomposite was a kind of intercalated–delaminated structure, while ABS/5 wt% OMTb nanocomposite was mainly an intercalated structure. The nanocomposites showed a lower heat release rate peak and higher thermal stability than the original ABS by TGA and cone calorimeter experiments. Also, the intercalated nanocomposite was more effective than an exfoliated–intercalated nanocomposite in fire retardancy. Copyright © 2003 Society of Chemical Industry  相似文献   
97.
98.
One promising switching technology for wavelength-division multiplexing optical networks is optical burst switching (OBS). However, there are major deficiencies of OBS. (1) The delay offset between a control message and its corresponding data burst is based on the diameter of a network. This affects network efficiency, quality-of-service, and network scalability.( 2) OBS adopts one-way resource reservation scheme, which causes frequent burst collision and, thus, burst loss. We address the above two important issues in OBS. In particular, we study how to improve the performance of delay and loss in OBS. To reduce the end-to-end delay, we propose a hybrid switching scheme. The hybrid switching is a combination of lightpath switching and OBS switching. A virtual topology design algorithm based on simulated annealing to minimize the longest shortest path through the virtual topology is presented. To minimize burst collision and loss, we propose a new routing algorithm, namely, p-routing, for OBS network. The p-routing is based on the wavelength available probability. A path that has higher available probability is less likely to drop bursts due to collision. The probability-based p-routing can reduce the volatility, randomness, and uncertainty of one-way resource reservation. Our studies show that hybrid switching and p-routing are complementary and both can dramatically improve the performance of OBS networks.  相似文献   
99.
100.
This potential for ion-pairing between dyclonine, a local anesthetic, and pharmaceutical dyes commonly used in liquid pharmaceutical formulations was examined. Occurrence of ion-pairing at a pH of 3 was confirmed by shift of the absorption maximum of all five sulfonate-containing dyes, and by measurements of octanol/water partition coefficient and surface tension. There was also an increase in the uptake of dyclonine by phosphatidylcholine liposomes in the presence of a dye (tartrazine) at pH 3 but not at pH 7, where the uncharged anesthetic is dominant.  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