全文获取类型
收费全文 | 18133篇 |
免费 | 3415篇 |
国内免费 | 1490篇 |
专业分类
电工技术 | 1839篇 |
技术理论 | 2篇 |
综合类 | 1395篇 |
化学工业 | 789篇 |
金属工艺 | 3499篇 |
机械仪表 | 1398篇 |
建筑科学 | 621篇 |
矿业工程 | 501篇 |
能源动力 | 389篇 |
轻工业 | 307篇 |
水利工程 | 582篇 |
石油天然气 | 441篇 |
武器工业 | 121篇 |
无线电 | 3387篇 |
一般工业技术 | 1736篇 |
冶金工业 | 862篇 |
原子能技术 | 203篇 |
自动化技术 | 4966篇 |
出版年
2024年 | 148篇 |
2023年 | 480篇 |
2022年 | 669篇 |
2021年 | 729篇 |
2020年 | 759篇 |
2019年 | 728篇 |
2018年 | 743篇 |
2017年 | 885篇 |
2016年 | 977篇 |
2015年 | 981篇 |
2014年 | 1381篇 |
2013年 | 1268篇 |
2012年 | 1414篇 |
2011年 | 1530篇 |
2010年 | 1066篇 |
2009年 | 1044篇 |
2008年 | 891篇 |
2007年 | 1123篇 |
2006年 | 1077篇 |
2005年 | 823篇 |
2004年 | 724篇 |
2003年 | 650篇 |
2002年 | 509篇 |
2001年 | 434篇 |
2000年 | 345篇 |
1999年 | 312篇 |
1998年 | 256篇 |
1997年 | 232篇 |
1996年 | 182篇 |
1995年 | 127篇 |
1994年 | 125篇 |
1993年 | 96篇 |
1992年 | 78篇 |
1991年 | 46篇 |
1990年 | 45篇 |
1989年 | 39篇 |
1988年 | 24篇 |
1987年 | 12篇 |
1986年 | 43篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 11篇 |
1982年 | 3篇 |
1981年 | 7篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1977年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
121.
122.
123.
124.
Yong ZhangAuthor VitaeXuejun ZhengAuthor Vitae Tong ZhangAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(2):887-892
Bi0.5Na0.5TiO3-Bi0.5K0.5TiO3 (BNT-BKT) powder is synthesized by a metal-organic decomposition method and characterized by field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). A humidity sensor, which is consisted of five pairs of Ag-Pd interdigitated electrodes and an Al2O3 ceramic substrate, is fabricated by spin-coating the BNT-BKT powder on the substrate. Good humidity sensing properties such as high response value, short response and recovery times, and small hysteresis are observed in the sensing measurement. The impedance changes more than four orders of magnitude within the whole humidity range from 11% to 95% relative humidity (RH) at 100 Hz. The response time and recovery time are about 20 and 60 s, respectively. The maximum hysteresis is around 4% RH. The results indicate that BNT-BKT powder is of potential applications for fabricating high performance humidity sensors. 相似文献
125.
Stefan WilhelmAuthor VitaeOtto S. WolfbeisAuthor Vitae 《Sensors and actuators. B, Chemical》2011,153(1):199-204
Absorption-based opto-chemical sensors for oxygen are presented that consist of leuco dyes (leuco indigo and leuco thioindigo) incorporated into two kinds of polymer matrices. An irreversible and visible color change (to red or blue) is caused by a chromogenic chemistry involving the oxidation of the (virtually colorless) leuco dyes by molecular oxygen. The moderately gas permeable copolymer poly(styrene-co-acrylonitrile) and a highly oxygen-permeable polyurethane hydrogel, respectively, are used in order to increase the effective dynamic range for visualizing and detecting oxygen. We describe the preparation and properties of four different types of such oxygen sensors that are obtained by dip-coating a gas impermeable foil made from poly(ethylene terephthalate) with a sensor layer composed of leuco dye and polymer. 相似文献
126.
N.M. ShaalanAuthor Vitae T. YamazakiAuthor Vitae T. KikutaAuthor Vitae 《Sensors and actuators. B, Chemical》2011,156(2):784-790
Electrodes with micro-gaps are fabricated by using dc-sputtering and FIB techniques. SnO2 nanowires are deposited on the micro-gap (1-30 μm) by suspension dropping method to fabricate a micro-gas sensor. The sensing ability of various SnO2 micro-gap sensors is measured. A comparison between sensors reveals that the short-gap electrode has numerous advantages in terms of reliability, high sensitivity and detection of low concentrations of NO2, while the large-gap electrode is relatively sensitive for high concentrations. Conductance measurements are carried out at different surface temperatures and NO2 concentrations in order to investigate the effects that the gap size has on the overall sensor conductance. The results suggest that the interface between the electrode and sensitive layer has a very important role for the sensing mechanism of tin dioxide gas sensors. 相似文献
127.
Vishal BalouriaAuthor Vitae Arvind KumarAuthor VitaeA. SinghAuthor Vitae S. SamantaAuthor VitaeA.K. DebnathAuthor Vitae Aman MahajanAuthor VitaeR.K. BediAuthor Vitae D.K. AswalAuthor Vitae S.K. GuptaAuthor VitaeJ.V. YakhmiAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(2):466-472
The conductometric gas sensing characteristics of Cr2O3 thin films - prepared by electron-beam deposition of Cr films on quartz substrate followed by oxygen annealing - have been investigated for a host of gases (CH4, CO, NO2, Cl2, NH3 and H2S) as a function of operating temperature (between 30 and 300 °C) and gas concentration (1-30 ppm). We demonstrate that these films are highly selective to H2S at an operating temperature of 100 °C, while at 220 °C the films become selective to Cl2. This result has been explained on the basis of depletion of chemisorbed oxygen from the surface of films due to temperature and/or interaction with Cl2/H2S, which is supported experimentally by carrying out the work function measurements using Kelvin probe method. The temperature dependent selectivity of Cr2O3 thin films provides a flexibility to use same film for the sensing of Cl2 as well as H2S. 相似文献
128.
Mei ChenAuthor VitaeZhihua WangAuthor Vitae Dongmei HanAuthor VitaeFubo GuAuthor Vitae Guangsheng GuoAuthor Vitae 《Sensors and actuators. B, Chemical》2011,157(2):565-574
Hierarchical flower-like and 1D tube-like ZnO architectures were synthesized by a microemulsion-based solvothermal method. Technologies of XRD, SEM and TEM were used to characterize the morphological and structural properties of the products. The influence of the flower-like and tube-like morphologies on their NO2 sensing properties was investigated. The experimental results showed that high-sensitivity NO2 gas sensors were fabricated. The sensitivity of the tube-like ZnO gas sensor was much higher than that of the flower-like ZnO gas sensor and the tube-like ZnO gas sensor exhibited shorter response time. The in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique was employed to investigate the NO2 sensing mechanisms. Free nitrate ions, nitrate and nitrite were the main adsorbed species during the adsorption, and NO also existed in the initial period of surface reoxidation. Furthermore, N2O was formed via NO− and N2O2− stemmed from NO and increased upon rising temperature. Moreover, the PL spectra and the XPS spectra further proved that the intensity of donors (oxygen vacancy (VO) and zinc interstitial (Zni)) and surface oxygen species (O2− and O2) involved in the gas sensing mechanism leaded to the different sensitivities. 相似文献
129.
为了能够在认知无线电网络中有效、准确地检测出授权用户,提出了基于改进的证据理论的合作频谱感知方案设计方法.根据各个次用户对授权用户进行多次本地检测得出的时域DS融合结果,设计并改进融合顺序和融合结构,将多个时域DS融合结果送到融合中心进行空域DS融合,得到最终判决.在此基础上,给出了融合顺序、融合结构的改变对算法性能的... 相似文献
130.