全文获取类型
收费全文 | 29253篇 |
免费 | 3634篇 |
国内免费 | 1812篇 |
专业分类
电工技术 | 3595篇 |
技术理论 | 1篇 |
综合类 | 2148篇 |
化学工业 | 4341篇 |
金属工艺 | 5181篇 |
机械仪表 | 1687篇 |
建筑科学 | 519篇 |
矿业工程 | 860篇 |
能源动力 | 709篇 |
轻工业 | 1978篇 |
水利工程 | 122篇 |
石油天然气 | 648篇 |
武器工业 | 519篇 |
无线电 | 3727篇 |
一般工业技术 | 3997篇 |
冶金工业 | 1891篇 |
原子能技术 | 1527篇 |
自动化技术 | 1249篇 |
出版年
2024年 | 141篇 |
2023年 | 634篇 |
2022年 | 1001篇 |
2021年 | 1210篇 |
2020年 | 1205篇 |
2019年 | 1064篇 |
2018年 | 1003篇 |
2017年 | 1194篇 |
2016年 | 1158篇 |
2015年 | 1166篇 |
2014年 | 1685篇 |
2013年 | 1800篇 |
2012年 | 2035篇 |
2011年 | 2248篇 |
2010年 | 1639篇 |
2009年 | 1714篇 |
2008年 | 1544篇 |
2007年 | 2012篇 |
2006年 | 1809篇 |
2005年 | 1432篇 |
2004年 | 1296篇 |
2003年 | 1094篇 |
2002年 | 835篇 |
2001年 | 697篇 |
2000年 | 634篇 |
1999年 | 469篇 |
1998年 | 341篇 |
1997年 | 327篇 |
1996年 | 286篇 |
1995年 | 195篇 |
1994年 | 171篇 |
1993年 | 143篇 |
1992年 | 119篇 |
1991年 | 75篇 |
1990年 | 64篇 |
1989年 | 68篇 |
1988年 | 40篇 |
1987年 | 21篇 |
1986年 | 14篇 |
1985年 | 17篇 |
1984年 | 8篇 |
1983年 | 11篇 |
1982年 | 32篇 |
1981年 | 23篇 |
1979年 | 4篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1961年 | 2篇 |
1959年 | 2篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 438 毫秒
81.
The 193 nm photochemistry of (aminoethylaminomethyl)phenethylsiloxane (PEDA) self‐assembled monolayers (SAMs) under ambient conditions is described. The primary photodegradation pathways at low exposure doses (< 100 mJ cm–2) are benzylic C–N bond cleavage (ca. 68 %), with oxidation of the benzyl C to the aldehyde, and Si–C bond cleavage (ca. 32 %). Amine‐containing photoproducts released from the SAM during exposure remain physisorbed on the surface, where they undergo secondary photolysis leading to their complete degradation and removal after ca. 1200 mJ cm–2. NaCl(aq) post‐exposure rinsing removes the physisorbed materials, showing that degradation of the original PEDA species (leaving Si–OH) is substantially complete after ca. 450 mJ cm–2. Consequently, patterned, rinsed PEDA SAMs function as efficient templates for fabrication of high‐resolution, negative‐tone, electroless metal and DNA features with good selectivity at low dose (i.e., ca. 400 mJ cm–2) via materials grafting to the intact amines remaining in the unirradiated PEDA SAM regions. 相似文献
82.
电力系统微机型产品的电磁兼容设计 总被引:2,自引:1,他引:1
从分析电力系统中电磁干扰的来源、传输途径入手,对应用于电力系统的微机型产品设计中的电磁兼容问题进行了较为系统的探讨,并提出了行有效的解决措施。 相似文献
83.
移动通信基站在高层建筑天台架设的定向天线,对周围环境的电磁辐射影响水平的监测进行分析,探讨高层建筑天台电磁辐射环境的污染防治对策。 相似文献
84.
电磁铸造液柱高度数学模型的建立及应用 总被引:2,自引:1,他引:1
为了研究熔体金属电磁立柱成形能力并计算电磁作用下的液注高度,从电磁铸造立柱成形的基本原理出发,建立了电磁场作用下金属立柱成形时液柱高度数学模型,并试验验证了模型的准确性.利用液柱高度数学模型对铝、钢、锡铅合金等金属的电磁铸造可行性,以及电力参数对液柱高度的影响进行研究.结果表明:铝电磁无模成形能力最强,而钢及锡铅合金电磁无模成形能力则基本相同;钢及锡铅合金电磁立柱成形所需的磁感强度约为0.08~0.10 T,而铝则只需约0.04T. 相似文献
85.
Ultra-fine aluminum nitride has been synthesized by the evaporation of aluminum powder at atmospheric-pressure nitrogen plasma in a hot-wall reactor.The average size of aluminum nitride particle is 0.11μm measured by scanning electric mirror(SEM),and the purity is at least over90% evaluated by X-Ray diffraction(XRD).The conversion of Al powder to aluminum nitride is strongly depended on the injection of NH3.Typical experimental parameters such as the feed rate of raw material,the flow rate of ammonia and the position of injecting aluminum powder into the reactor are given. 相似文献
86.
87.
88.
本文研究了采用锁定放大相干检测技术的等离子体光发射谱检测系统。用该系统检测了仅用CF4作为刻蚀气体刻蚀非晶硅基薄膜的等离子体光发射谱。分析了检测结果和刻蚀机理。 相似文献
89.
Xiang Lu S. Sundar Kumar Iyer Jin Lee Brian Doyle Zhineng Fan Paul K. Chu Chenming Hu Nathan W. Cheung 《Journal of Electronic Materials》1998,27(9):1059-1066
We have demonstrated feasibility to form silicon-on-insulator (SOI) substrates using plasma immersion ion implantation (PIII)
for both separation by implantation of oxygen and ion-cut. This high throughput technique can substantially lower the high
cost of SOI substrates due to the simpler implanter design as well as ease of maintenance. For separation by plasma implantation
of oxygen wafers, secondary ion mass spectrometry analysis and cross-sectional transmission electron micrographs show continuous
buried oxide formation under a single-crystal silicon overlayer with sharp Si/SiO2 interfaces after oxygen plasma implantation and high-temperature (1300°C) annealing. Ion-cut SOI wafer fabrication technique
is implemented for the first time using PIII. The hydrogen plasma can be optimized so that only one ion species is dominant
in concentration and there are minimal effects by other residual ions on the ion-cut process. The physical mechanism of hydrogen
induced silicon surface layer cleavage has been investigated. An ideal gas law model of the microcavity internal pressure
combined with a two-dimensional finite element fracture mechanics model is used to approximate the fracture driving force
which is sufficient to overcome the silicon fracture resistance. 相似文献
90.
N‐(4‐Acetoxyphenyl) maleimide (APMI) and three kinds of comonomers bearing a trimethylsilyl group were copolymerized at 60°C in the presence of azobisisobutyronitrile (AIBN) as an initiator in 1,4‐dioxane to obtain the three IP, IIP, and IIIP copolymers. These copolymers were removed from the acetoxy group in a transesterification process into new IVP, VP, and VIP copolymers with a pendant hydroxyl group. Two modified processes were adopted to prepare photoresists using these copolymers. The first process involved mixing the dissolution inhibitor, o‐nitrobenzyl cholate, with the new copolymers. Second, o‐nitrobenzyl cholate was introduced into the copolymers using 1,8‐diazabicyclo[5.4.0]undec‐7‐ene (DBU) in dimethylformamide (DMF). The cyclic maleimide structure is responsible for the high thermal stability of these copolymers. After irradiation using deep–UV light and development with aqueous Na2CO3 (0.01 wt %), the developed patterns showed positive images and exhibited good adhesion to the silicon wafer without using any adhesion promoter. The resolution of these resists was at least 0.8 μm and an oxygen‐plasma etching rate was 1/5.3 to that of hard‐baked HPR‐204. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2791–2798, 2002; DOI 10.1002/app.10255 相似文献