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   4697篇
  免费   292篇
  国内免费   7篇
电工技术   23篇
综合类   7篇
化学工业   1605篇
金属工艺   29篇
机械仪表   76篇
建筑科学   190篇
矿业工程   5篇
能源动力   92篇
轻工业   862篇
水利工程   44篇
石油天然气   16篇
无线电   223篇
一般工业技术   563篇
冶金工业   751篇
原子能技术   34篇
自动化技术   476篇
  2024年   10篇
  2023年   66篇
  2022年   347篇
  2021年   343篇
  2020年   161篇
  2019年   152篇
  2018年   151篇
  2017年   146篇
  2016年   151篇
  2015年   157篇
  2014年   193篇
  2013年   294篇
  2012年   262篇
  2011年   334篇
  2010年   244篇
  2009年   241篇
  2008年   241篇
  2007年   223篇
  2006年   161篇
  2005年   129篇
  2004年   133篇
  2003年   113篇
  2002年   100篇
  2001年   40篇
  2000年   53篇
  1999年   48篇
  1998年   57篇
  1997年   45篇
  1996年   48篇
  1995年   34篇
  1994年   38篇
  1993年   32篇
  1992年   22篇
  1991年   11篇
  1990年   19篇
  1989年   20篇
  1988年   25篇
  1987年   22篇
  1986年   18篇
  1985年   15篇
  1984年   10篇
  1983年   11篇
  1982年   15篇
  1981年   12篇
  1980年   3篇
  1979年   12篇
  1978年   8篇
  1977年   3篇
  1973年   4篇
  1972年   3篇
排序方式: 共有4996条查询结果,搜索用时 15 毫秒
31.
成品率预测是可制造性设计(DFM)的基础之,但它还远不止于此。IBM系统和技术群300mm半导体运营副总裁DanArmbrust说:“我们精确预测成品率的能力就是我们的经济模式。”Armbrust是SEMICON West 2007成品率论坛讨论DFM现状的三位参与者之一。与他共同参加讨论的是Synopsys公司DFM解决方案副总裁Anantha Sethuraman和Photronics公司的CTO Chris Progler。  相似文献   
32.
The management of small cell is considered a key point in next‐generation cellular networks for providing higher data rates, and the relay nodes are expected to be useful to improve the coverage area. Moreover, multicast services have gained importance to disseminate common data to subscribers. The use of buffer‐aided relay for multicast communications is analysed in the paper, and different policies to perform the optimal link selections are compared. These policies are based on the knowledge of the instantaneous link quality indicators as well as the status of the relay buffer and dynamically select the better link according to a suitable probabilistic criterion by improving the aggregate multicast flows. The parameters of these multicast policies are optimized via a Markov chain theoretical framework. The performance for all the proposed methods is analytically derived and validated through computer simulations conducted in different multicast scenarios. The advantages of the proposed schemes are pointed out in terms of multicast throughput, buffer occupancy for different buffer and multicast group size. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
33.
Mobile Networks and Applications - During the last ten years, Online Social Networks (OSNs) have increased their popularity by becoming part of the real life of users. Despite their tremendous...  相似文献   
34.
We demonstrate the non-uniqueness of proportional fairness prices, and show that the model of Kelly et al. [9] falls into the category of models that can be generalized to allow optimization of the link prices, with a view toward profit maximization. However, through this framework, we also show that the total revenue that can be obtained through proportional fairness pricing on a network is unique.  相似文献   
35.
Precise, reliable, and remote measurement of dissolved oxygen in aqueous media is of great importance for many industrial, environmental, and biological applications. In particular, photoelectrochemical sensors working in differential mode have recently demonstrated promising properties, in terms of stability, sensitivity, and application potential. Here, a new approach is presented, combining visible light sensitivity, efficient photocurrent generation, and solution‐processed fabrication methods of conjugated polymers, with charge carriers selectivity, energetic alignment favorable to efficient interfacial charge transfer and high surface area achievable by using metal oxide nanostructures. Extensive characterization and optimization of the hybrid organic/inorganic system are carried out, leading to the realization of an oxygen sensor device, based on nanostructured palladium oxide/poly[(9,9‐dioctylfluorenyl‐2,7‐diyl)‐alt‐5,5‐(4′,7′‐di‐2‐thienyl‐2′,1′,3′‐benzothiadiazole]/[6,6]phenyl‐C61‐butyric acid methyl ester (PdO/APFO‐3:PCBM) as materials of choice. State‐of‐the‐art sensitivity, amounting at ?5.87 μA cm?2 ppm?1, low background signal, in the order of ?4.85 μA cm?2, good electrochemical stability for more than 2 h of continuous functioning and high reproducibility of the signal over the pH 1 to 10 range, are reported, making the hybrid device suitable for several practical uses. The results fully validate the mixed organic/inorganic approach for photoelectrochemical applications, and pave the way for its further exploitation in fields like waste water treatment, environmental monitoring, and water splitting.  相似文献   
36.
A new strategy for particle synthesis is enabled by utilizing modern synthetic, polymer, and photochemical techniques to facilitate the synthesis of highly narrow–disperse multifunctional microspheres from visible‐light induced crosslinking of prepolymers in both a single and dual polymer system. The approach requires no stabilizers, bases, or initiators, and proceeds at ambient temperature to yield microspheres with a tunable size range (0.25–5 µm) in less than 4 h, depending largely on solvent composition, but also polymer concentration (2–10 mg mL?1), ratio, and irradiation intensity (3–20 W). Critically, the visible‐light induced dimerization reaction exploited herein enables simple functional particle syntheses via a single polymer system. Underpinned by an in‐depth kinetic analysis of the particle formation as well as a detailed small molecule study, the mechanism for particle formation is also elucidated. Importantly, inherent advantages of the system are exploited for surface functionalization of residual acrylate and hydroxyl groups (generating inherently fluorescent particles).  相似文献   
37.
Multimodality medical imaging takes advantage of the strengths of different imaging modalities to provide a more complete picture of the anatomy under investigation. Many complementary modalities have been combined to form such systems and some are gaining use clinically. One combination that has not been developed, in large part due to technical difficulties, is a combined magnetic resonance (MR) and ultrasound (US) imaging system. Such a system offers the potential to combine the strengths of these modalities in a wide range of diagnostic and therapeutic applications. The goal of this study was to evaluate the feasibility of performing simultaneous multimodality US and MR imaging. An US imaging system capable of operation in a clinical MR imager was developed, and methods to perform simultaneous imaging were investigated. Simultaneous imaging was feasible without any mutual interference by either filtering the transmitted and received US signal, or by synchronizing data acquisition between the two imaging systems. Spatial registration between the two modalities was achieved by using a reference phantom with implanted glass beads in orthogonal planes. Excellent agreement was observed between spatial measurements of an object made with both modalities, and the feasibility of using this system in vivo was demonstrated in a rabbit model. Simultaneous US and MR imaging is achievable, and can provide complementary information about an object under investigation. This demonstration of technical feasibility and the development of a prototype system open up the potential to investigate the promising clinical applications of this combined technology.  相似文献   
38.
涂层的应用导致晶圆上缺陷的增加或者使光刻表现发生变化虽然现在推测浸没光刻技术的量产时间还太早,但是许多公司正在努力确定生产线何时能从干法工艺跃为湿法工艺。根据最近在San Jose举办的  相似文献   
39.
Few‐layer palladium diselenide (PdSe2) field effect transistors are studied under external stimuli such as electrical and optical fields, electron irradiation, and gas pressure. The ambipolar conduction and hysteresis are observed in the transfer curves of the as‐exfoliated and unprotected PdSe2 material. The ambipolar conduction and its hysteretic behavior in the air and pure nitrogen environments are tuned. The prevailing p‐type transport observed at atmospheric pressure is reversibly turned into a dominant n‐type conduction by reducing the pressure, which can simultaneously suppress the hysteresis. The pressure control can be exploited to symmetrize and stabilize the transfer characteristics of the device as required in high‐performance logic circuits. The transistors are affected by trap states with characteristic times in the order of minutes. The channel conductance, dramatically reduced by the electron irradiation during scanning electron microscope imaging, is restored after an annealing of several minutes at room temperature. The work paves the way toward the exploitation of PdSe2 in electronic devices by providing an experiment‐based and deep understanding of charge transport in PdSe2 transistors subjected to electrical stress and other external agents.  相似文献   
40.
Several message topic selection approaches propose that messages based on beliefs pretested and found to be more strongly associated with intentions will be more effective in changing population intentions and behaviors when used in a campaign. This study aimed to validate the underlying causal assumption of these approaches which rely on cross‐sectional belief–intention associations. We experimentally tested whether messages addressing promising themes as identified by the above criterion were more persuasive than messages addressing less promising themes. Contrary to expectations, all messages increased intentions. Interestingly, mediation analyses showed that while messages deemed promising affected intentions through changes in targeted promising beliefs, messages deemed less promising also achieved persuasion by influencing nontargeted promising beliefs. Implications for message topic selection are discussed.  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