全文获取类型
收费全文 | 38516篇 |
免费 | 2754篇 |
国内免费 | 1491篇 |
专业分类
电工技术 | 1189篇 |
综合类 | 1833篇 |
化学工业 | 7390篇 |
金属工艺 | 3692篇 |
机械仪表 | 2442篇 |
建筑科学 | 680篇 |
矿业工程 | 295篇 |
能源动力 | 1953篇 |
轻工业 | 2370篇 |
水利工程 | 129篇 |
石油天然气 | 726篇 |
武器工业 | 172篇 |
无线电 | 8481篇 |
一般工业技术 | 8804篇 |
冶金工业 | 897篇 |
原子能技术 | 551篇 |
自动化技术 | 1157篇 |
出版年
2025年 | 206篇 |
2024年 | 721篇 |
2023年 | 599篇 |
2022年 | 734篇 |
2021年 | 1016篇 |
2020年 | 1007篇 |
2019年 | 966篇 |
2018年 | 854篇 |
2017年 | 1276篇 |
2016年 | 1243篇 |
2015年 | 1210篇 |
2014年 | 1815篇 |
2013年 | 2024篇 |
2012年 | 2190篇 |
2011年 | 2791篇 |
2010年 | 2100篇 |
2009年 | 2256篇 |
2008年 | 2023篇 |
2007年 | 2423篇 |
2006年 | 2216篇 |
2005年 | 1870篇 |
2004年 | 1708篇 |
2003年 | 1481篇 |
2002年 | 1211篇 |
2001年 | 1097篇 |
2000年 | 1012篇 |
1999年 | 829篇 |
1998年 | 699篇 |
1997年 | 597篇 |
1996年 | 505篇 |
1995年 | 424篇 |
1994年 | 399篇 |
1993年 | 317篇 |
1992年 | 238篇 |
1991年 | 185篇 |
1990年 | 118篇 |
1989年 | 115篇 |
1988年 | 85篇 |
1987年 | 49篇 |
1986年 | 29篇 |
1985年 | 18篇 |
1984年 | 20篇 |
1983年 | 10篇 |
1982年 | 14篇 |
1981年 | 9篇 |
1980年 | 5篇 |
1979年 | 8篇 |
1975年 | 5篇 |
1959年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
介绍了生产连续性一次自动成型-开口充料-加热封口(FFS)袋用吹塑薄膜的平膜法和管膜法工艺及三层共挤膜技术,概述了国内FFS袋用吹塑薄膜的生产企业和原料使用情况。FFS袋用吹塑薄膜具有包装速度快、洁净、环保、美观等优势,随着国内合成树脂装置生产规模的扩大,FFS袋用吹塑薄膜将替代传统复合编织袋成为合成树脂包装领域的主导产品。 相似文献
62.
We investigated the optical properties and the degradation process of the organic p-type semiconductor poly(triarylamine) (PTAA) in the mid infrared region. The dielectric function of PTAA was determined in the spectral region of 700 up to 6000 cm−1 by modeling ellipsometric measurements. Due to degradation at 65 °C, PTAA thin films developed carbonyl and hydroxyl features in the infrared spectra. Degradation under 85% RH additionally led to absorption signals of water. A degradation of the bare gold substrates was also observed. For bare gold films, morphology changed upon degradation and adsorption of hydrocarbons from the ambience took place. 相似文献
63.
Weidong Huang Xuhong Wang Li Wang Mei Sheng Liqiang Xu Frank Stubhan Le Luo 《Journal of Electronic Materials》2004,33(2):101-105
The moisture diffusion in globtop material for a chip-on-board (COB) package coated with SiNx and silicone, respectively, or coated with SiNx plus silicone were measured by embedding a humidity sensor in the globtop and recording the capacitive change in three different
temperature/humidity environments. The experimental results were simulated by Fick’s diffusion law with finite-element method
modeling. The moisture diffusion coefficients and activation energies were calculated to quantitatively compare the moisture-resistance
effects of different coatings. For example, at 85°C/85% RH, the moisture diffusion coefficients for the uncoated reference,
SiNx-coated, silicone-coated, and silicone/SiNx double-layered coated samples are 1E-5, 0.8E-5, 0.7E-5, and 0.2E-5 mm2/s, respectively. The experimental and simulation results show that double-layered coating with silicone/SiNx has excellent moisture-resistance properties because it not only smoothes the steps on a printed circuit board (PCB) but
also keeps the good moisture resistance of the inorganic films. 相似文献
64.
65.
One of the many remarkable properties of diamond is its thermal conductivity, about five times that of copper and the highest
of all known materials. The high thermal conductivity in combination with the relative ease of diamond film growth by chemical
vapor deposition process makes the material suitable for many applications such as thermal management in high power electronic
circuits. For thermal managements applications, various processing steps are needed for the diamond films, such as the metallization
for reliable solder bonding, metallurgical processes for planarizing of the faceted growth surface and removal of fine-grained
diamond regions with poor thermal conductivity. This paper will review the properties and processing of diamond films for
thermal management applications. 相似文献
66.
Structural, electrical and optical properties of zinc oxide produced by oxidation of zinc thin films
H. Kashani 《Journal of Electronic Materials》1998,27(7):876-882
We have investigated the effects of oxidation temperature on the physical properties of polycrystalline zinc oxide thin films.
Zinc thin films are oxidized at different temperatures in air. We have found that increasing the oxidation temperature deteriorates
the preferred c-axis orientation. Also, increasing the oxidation temperature enlarges the crystal size and increases the number of needle-shaped
crystals on the surface of the ZnO samples. By increasing the oxidation temperature, more than zinc melting point, tensile
stresses start to build up in the films. Also by increasing temperature, sheet resistance of the films decreases, while photoluminescence
intensity ratio (green to orange) increases. Increasing the oxidation temperature reduces the transparency of the films, too.
It is proposed that either an increase in the number of oxygen vacancies or a decrease in the volume of grain boundaries,
is responsible for the observed behavior of the films at higher oxidation temperatures. 相似文献
67.
振动膜的工艺及设计,是动圈传声器设计中的主要技术,文中论述了振动膜的设计及压制工艺,并介绍了几种优良的振动系统。 相似文献
68.
利用半导体致冷器可以加热又可以致冷的双向性,研制成双向主动式高精度控温仪。在15~32℃范围内,控温精度高达±0.004℃。用于控制KTP晶体温度,在OPO实验中获得稳定的参量下转换输出。 相似文献
69.
本文介绍了RTT的概念和谐振隧穿双势垒(DB)的理论,综述了RTT的最新进展,其中包括基区和发射区内有DB的谐振隧道双极晶体管(RTBT)、多态RTBT、超晶格RTBT、双极量子RTT(BiQuaRTT)和单极量子线RTT。 相似文献
70.
H.-J. Muffler M. Br I. Lauermann K. Rahne M. Schrder M.C. Lux-Steiner C.-H. Fischer T.P. Niesen F. Karg 《Solar Energy Materials & Solar Cells》2006,90(18-19):3143-3150
A method for the fixation of colloids by an ion-layer-gas-reaction-“ILGAR”-oxide layer is presented. The embedding of CdS nano-particles in an ILGAR-ZnO/Zn(OH)2-matrix is confirmed by transmission electron micrographs (TEM); the composition of the layer surface is analyzed by X-ray photoelectron microscopy (XPS). When these particles are fixed by an ILGAR-oxide layer on top of a solar cell the observed absorption and fluorescing properties of CdS nano-particles offer the possibility to reduce the absorption loss in the window layer. This is shown for a Cu(In,Ga)(S,Se)2-“CIGSSe”-based solar cell with an additional top CdSparticle/ILGAR-ZrO2-layer as a first example. The improvement of the device performance is proven by J(V)-characteristics and the external quantum efficiency. 相似文献