全文获取类型
收费全文 | 39937篇 |
免费 | 4060篇 |
国内免费 | 2287篇 |
专业分类
电工技术 | 1052篇 |
技术理论 | 1篇 |
综合类 | 2525篇 |
化学工业 | 11291篇 |
金属工艺 | 2249篇 |
机械仪表 | 1700篇 |
建筑科学 | 2116篇 |
矿业工程 | 447篇 |
能源动力 | 759篇 |
轻工业 | 1140篇 |
水利工程 | 318篇 |
石油天然气 | 2473篇 |
武器工业 | 434篇 |
无线电 | 3824篇 |
一般工业技术 | 6980篇 |
冶金工业 | 3239篇 |
原子能技术 | 215篇 |
自动化技术 | 5521篇 |
出版年
2024年 | 192篇 |
2023年 | 693篇 |
2022年 | 885篇 |
2021年 | 1205篇 |
2020年 | 1187篇 |
2019年 | 1086篇 |
2018年 | 979篇 |
2017年 | 1241篇 |
2016年 | 1275篇 |
2015年 | 1295篇 |
2014年 | 1969篇 |
2013年 | 2218篇 |
2012年 | 2412篇 |
2011年 | 2981篇 |
2010年 | 2248篇 |
2009年 | 2386篇 |
2008年 | 2268篇 |
2007年 | 2700篇 |
2006年 | 2552篇 |
2005年 | 2179篇 |
2004年 | 1944篇 |
2003年 | 1720篇 |
2002年 | 1525篇 |
2001年 | 1332篇 |
2000年 | 1013篇 |
1999年 | 860篇 |
1998年 | 756篇 |
1997年 | 592篇 |
1996年 | 459篇 |
1995年 | 384篇 |
1994年 | 354篇 |
1993年 | 293篇 |
1992年 | 225篇 |
1991年 | 153篇 |
1990年 | 113篇 |
1989年 | 103篇 |
1988年 | 85篇 |
1987年 | 38篇 |
1986年 | 38篇 |
1985年 | 75篇 |
1984年 | 61篇 |
1983年 | 47篇 |
1982年 | 41篇 |
1981年 | 13篇 |
1980年 | 13篇 |
1979年 | 9篇 |
1977年 | 11篇 |
1964年 | 6篇 |
1963年 | 6篇 |
1961年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 562 毫秒
41.
进入21世纪,随着集成电路的发展,SoC(System on Chip)片上系统应运而生。而作为SoC重要组成部分的嵌入式存储器,在SoC中所占的比重正逐步增加,并起着越来越重要的作用,那么嵌入式存储器与独立的存储器芯片在设计上存在着哪些差异?对此本文将以NOR型闪存为例在制造工艺的选取、衍生产品的设计、功耗与噪声、后端功能仿真、测试与修复等方面进行分析和研究。 相似文献
42.
43.
单片机中断多优先级的软件扩展方法 总被引:1,自引:0,他引:1
为了解决MCS-51系列单片机只能由IP寄存器设定两级优先级的问题 ,文中给出了利用软件对中断优先级进行扩展的方法 ,同时给出了高于两个优先级的多优先级软件扩展程序。 相似文献
44.
45.
Oxidation behavior of a 2 mol % divinylbenzene (DVB)‐crosslinked polystyrene‐supported permanganate function was investigated toward low molecular weight primary and secondary alcohols and aldehydes. The permanganate function was attached to a polystyrene support through cyclic polyoxyethylene (POE) units immobilized on the support. Contrary to the oxidations catalyzed by low molecular weight permanganate reagents, the oxidation of primary alcohol terminated in the aldehyde stage. The secondary alcohols were converted to the respective ketone and aldehyde to acid. The effect of the variable parameters similar to solvent, temperature, and reagent to substrate ratio was followed. Nonpolar cyclohexane was found to be the best solvent for the present study. Also the reactivity increased with increasing temperature. The oxidizing reagent possesses a long shelf life and could be recycled several times without reduction of capacity and mechanical stability. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3708–3717, 2003 相似文献
46.
Removal of gold from basic solutions containing [Au(CN)2]? has been demonstrated using the inherently conducting polymer polypyrrole. Polymers containing sulfonated aromatic dopants have been found to display a significant ability to remove gold from such solutions. Experiments performed in solutions containing both gold and copper cyanide complexes indicate that the recovery process is not highly selective. However, the polypyrroles used display significantly faster rates of gold recovery than activated carbon. © 2003 Society of Chemical Industry 相似文献
47.
48.
由于干态聚合物电解质目前还不能满足聚合物锂离子电池的应用要求,人们致力于开发含液体增塑剂的聚合物电解质,包括凝胶型和微孔型两类体系。本文综述了含液聚合物电解质的最新进展,重点论述了各种新体系和新方法。 相似文献
49.
Life is pleasant--and memory helps to keep it that way! 总被引:1,自引:0,他引:1
Walker W. Richard; Skowronski John J.; Thompson Charles P. 《Canadian Metallurgical Quarterly》2003,7(2):203
People's recollections of the past are often positively biased. This bias has 2 causes. The 1st cause lies in people's perceptions of events. The authors review the results of several studies and present several new comparative analyses of these studies, all of which indicate that people perceive events in their lives to more often be pleasant than unpleasant. A 2nd cause is the fading affect bias: The affect associated with unpleasant events fades faster than the affect associated with pleasant events. The authors review the results of several studies documenting this bias and present evidence indicating that dysphoria (mild depression) disrupts such bias. Taken together, this evidence suggests that autobiographical memory represents an important exception to the theoretical claim that bad is stronger than good. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
50.
Polymer networks in which poly(propylene imine) dendrimers (Astramol?) are connected to each other by linear polytetrahydrofuran (polyTHF) segments, were prepared by two methods. The first method was a one‐step procedure in which bifunctionally living polyTHF, obtained by initiation of the THF polymerization with trifluoromethane sulfonic anhydride (triflic anhydride), was reacted with an amino‐dendrimer. This reaction was very fast but did not allow formation of the end products. The second method was a two‐step procedure. In a first step, living polyTHF, prepared with acryloyloxybutyl triflate as initiator, was grafted on an amino‐dendrimer, to form a star‐like, acrylate‐terminated polyTHF multi‐macromonomer with the dendrimer as core. In a second step, networks were obtained by Michael addition between the acrylate end‐groups and unreacted amino‐groups of the dendrimer. This cross‐linking reaction occurred spontaneously upon heating of the solution of the multi‐macromonomer with gelation times varying from a few minutes to a few hours, depending on the temperature and the composition of the prepolymers. With this method it was possible to prepare networks in the form of coatings or films. © 2003 Society of Chemical Industry 相似文献