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   69912篇
  免费   5234篇
  国内免费   2785篇
电工技术   3438篇
技术理论   10篇
综合类   4071篇
化学工业   12214篇
金属工艺   3776篇
机械仪表   4315篇
建筑科学   5947篇
矿业工程   2005篇
能源动力   2059篇
轻工业   4230篇
水利工程   1103篇
石油天然气   4363篇
武器工业   534篇
无线电   8214篇
一般工业技术   8936篇
冶金工业   3586篇
原子能技术   783篇
自动化技术   8347篇
  2024年   250篇
  2023年   1122篇
  2022年   1851篇
  2021年   2520篇
  2020年   1997篇
  2019年   1762篇
  2018年   1921篇
  2017年   2215篇
  2016年   1996篇
  2015年   2632篇
  2014年   3250篇
  2013年   3896篇
  2012年   4278篇
  2011年   4516篇
  2010年   3932篇
  2009年   3723篇
  2008年   3652篇
  2007年   3645篇
  2006年   3842篇
  2005年   3325篇
  2004年   2292篇
  2003年   2001篇
  2002年   1928篇
  2001年   1751篇
  2000年   1755篇
  1999年   2026篇
  1998年   1810篇
  1997年   1485篇
  1996年   1418篇
  1995年   1081篇
  1994年   1034篇
  1993年   714篇
  1992年   549篇
  1991年   440篇
  1990年   329篇
  1989年   262篇
  1988年   238篇
  1987年   149篇
  1986年   105篇
  1985年   80篇
  1984年   38篇
  1983年   36篇
  1982年   40篇
  1981年   22篇
  1980年   14篇
  1979年   5篇
  1978年   1篇
  1976年   1篇
  1959年   2篇
排序方式: 共有10000条查询结果,搜索用时 17 毫秒
21.
In order to investigate the galvanic anodic protection (GAP) of ferrous metals (such as 410, 304 and 316 stainless steels) in acid solutions by doped polyaniline (PANi), separate doped PANi powder-pressed electrodes with different surface areas (the area ratio of the PANi electrode to stainless steel is between 1:1 and 1:2) have been prepared. These were coupled with ferrous metal in the following solutions: 5 M sulphuric acid, 5 M phosphoric acid and industrial phosphoric acid (containing 5 M phosphoric acid and 0.05% chloride ion) to construct a galvanic cell, in which PANi is cathode while ferrous metal is anode. The results indicate that a PANi electrode with sufficient area can provide corrosion protection to stainless steel in these acidic solutions. A pilot scale coupling experiment was carried out. The results indicate that PANi is a promising material as an electrode for the anodic protection of ferrous metals in acidic solutions in industrial situations.  相似文献   
22.
本文介绍β放射性气体浓度计的一种新的分度方法——泄漏元件排气法。其特点是一只元件可分度放射性气体浓度计的许多读出数(甚至是几个量程),操作方便。  相似文献   
23.
An access-mode prediction technique based on cache hit and miss speculation for cache design-achieves minimal energy consumption. Using this method, cache accesses can be adaptively switched between the way-prediction and the phased accessing modes.  相似文献   
24.
25.
The fabrication of one kind of large core area Nd3 doped silicate glass photonic crystal fiber, and demonstration of the fiber's waveguidence properties were reported. This fiber owns a random air hole distribution in the cladding. The measured minimum loss of this kind of fiber is 10 dB·m-1 at 660 nm. These fibers can sustain only a single mode at least over wavelength ranging from 660 nm to 980 nm.  相似文献   
26.
多信道E1映射复用成帧芯片PM8316及其应用   总被引:1,自引:0,他引:1  
PM8316是PMC-Sierra公司生产的一种低功耗、高性能的多信道E1映射复用成帧芯片。该芯片内部集成了映射器、复用器、成帧器,其处理容量为63路E1,并含有8位微处理器总线接口和5个标准信号的JTAG测试端口,可支持收发抖动衰减。文中介绍了PM8316的主要功能和接口,给出了它在SDH终端设备中的主要信号电路框图。  相似文献   
27.
1“居山”与”隐贵山居“ 回想一下人类的聚居行为颇为有趣,当年我们的祖先拼命从险山恶水的自然环境中挣脱出来,为的是得到更加安全和便利的聚居条件,但似乎从那一刻起本能式的回归意识便时刻魂牵梦绕,隐隐作响。其实无论是脱离自然还是回归自然,对于现实而言两者皆是虚幻和理想的。  相似文献   
28.
Poly(ethylene terephthalate) (PET) is of excellent mechanical properties and melt processability and is widely used as raw material for textile fibers. However, the flame retardant properties of PET were rather poor, and both reactive and additive phosphorus- and halogen-containing compounds have been employed to enhance the reaction-to-fire properties while the meltdripping behaviour during burning hasn’t been handled properly with the flame retardants. In this work, fluoropolymer was blended with both pure PET (pPET) and reactive phosphorus-containing flame retarded copolyester (fPET), and the flame retardance and char formation and mechanical properties of the resulted pPET and fPET blends were investigated. The tensile strengths of modified pPET samples were worsen whereas those of modified fPET samples were improved at low concentrations. The initial thermal degradation in nitrogen was accelerated remarkably for the two polyesters with fluoropolymer. The oxygen indices of the all modified samples were reduced while char formation and meltdripping suppression were encouraged. The apparent melt viscosity and elasticity for the two polyesters were gained much with antidripping agent. Therefore, fluoropolymer improved char formation of the two polyesters based on the gaseous phase mechanism while the partial suppression of meltdripping behavior and the decrease of mechanical properties mainly originated from the increase of melt viscosity via fibrillation for pPET.  相似文献   
29.
浅谈集成电路的废气处理   总被引:1,自引:1,他引:0  
集成电路的工业废气有含氟化物、硫酸雾的酸性废气,含氨的碱性废气,含异丙醇、光刻胶的有机废气,含SiO_2的含尘废气,以及含硅烷、磷烷的工艺尾气等,这些工业废气中大部分成分是有毒有害的,必须进行有效的处理才能排入大气中。主要讨论上述工业废气的分类、处理方式、应用范围及应用实例等。  相似文献   
30.
Sodium sulfonate‐terminated dendritic poly(ester‐amine) (SPEA) was synthesized by sulfonation of acrylic double bond‐terminated dendritic poly(ester‐amine) (APEA) with sodium hydrogen sulfite (NaHSO3) in mixture of diglycol and 2‐butanone under normal pressure. The structure of SPEA was characterized by IR, 1H‐NMR, and elemental analysis. SPEA was water‐soluble. 1.0–40.0% (mass) SPEA aqueous solutions appeared as dilatant fluid. When pH value varied from 1.5 to 12.0, the viscosity of 1–5% (mass) SPEA aqueous solutions changed very small, and the electric conductivity almost kept stable within pH 3.0–10.0. The relationship between the viscosity and the concentration of SPEA water solutions was similar to that of NaCl water solutions. The surface tension of SPEA water solutions was lower than that of polyethylene glycol 2000 water solutions with the same concentration. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008  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