全文获取类型
收费全文 | 1476篇 |
免费 | 97篇 |
国内免费 | 13篇 |
专业分类
电工技术 | 17篇 |
综合类 | 34篇 |
化学工业 | 272篇 |
金属工艺 | 56篇 |
机械仪表 | 103篇 |
建筑科学 | 41篇 |
矿业工程 | 6篇 |
能源动力 | 62篇 |
轻工业 | 119篇 |
水利工程 | 10篇 |
石油天然气 | 20篇 |
无线电 | 221篇 |
一般工业技术 | 334篇 |
冶金工业 | 122篇 |
原子能技术 | 9篇 |
自动化技术 | 160篇 |
出版年
2023年 | 17篇 |
2022年 | 23篇 |
2021年 | 44篇 |
2020年 | 35篇 |
2019年 | 40篇 |
2018年 | 40篇 |
2017年 | 52篇 |
2016年 | 30篇 |
2015年 | 31篇 |
2014年 | 75篇 |
2013年 | 89篇 |
2012年 | 98篇 |
2011年 | 100篇 |
2010年 | 71篇 |
2009年 | 83篇 |
2008年 | 74篇 |
2007年 | 63篇 |
2006年 | 69篇 |
2005年 | 50篇 |
2004年 | 32篇 |
2003年 | 42篇 |
2002年 | 46篇 |
2001年 | 35篇 |
2000年 | 31篇 |
1999年 | 28篇 |
1998年 | 51篇 |
1997年 | 47篇 |
1996年 | 38篇 |
1995年 | 22篇 |
1994年 | 21篇 |
1993年 | 15篇 |
1992年 | 18篇 |
1991年 | 10篇 |
1990年 | 12篇 |
1989年 | 7篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1980年 | 2篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1974年 | 4篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1968年 | 1篇 |
1944年 | 1篇 |
排序方式: 共有1586条查询结果,搜索用时 0 毫秒
91.
Cher Liang Cha Eng Fong Chor Hao Gong An Qing Zhang Lap Chan 《Semiconductor Manufacturing, IEEE Transactions on》2000,13(3):386-389
The breakdown time of flash memory oxide/nitride/oxide (ONO) layer tbd under positive constant current stressing has been found to be closely related to the cumulative extent of (over)etch of the tungsten silicide, control polysilicon, and ONO layers, i.e., Σ(ΛOE). An empirical first-order relation between tbd and Σ(ΛOE) has been derived to facilitate the plasma etch recipe optimization. This has led to a four-fold increase in the average tbd across a 200-mm wafer to 208 s. More importantly, the spread in tbd has been tightened to ~5%, which is down from ~54% 相似文献
92.
R. Gerling F.P. Schimansky A. Stark A. Bartels H. Kestler L. Cha C. Scheu H. Clemens 《Intermetallics》2008,16(5):689-697
The possible application of gamma titanium aluminides in aerospace industry requires a detailed understanding of the microstructure–property relationship of sheets made from this material. This paper reports the mechanical properties of sheets up to 1000 °C, based on alloy concepts with high Nb concentrations and small additions of C. Sheets were manufactured by rolling powder metallurgical compacts with compositions Ti 45Al 5Nb and Ti 45Al 5Nb 0.5C. The microstructures of both sheets are “near gamma” and consist of γ-TiAl and 2-Ti3Al phases. The texture of both phases is very weak. The strengths levels are very high and that of the C-containing sheet exceeds that of the C-free material at RT by 200 MPa. The mechanical properties of Ti 45Al 5Nb are independent of the direction in the sheet, in the whole temperature range from RT to 1000 °C. However, for the C-containing sheet this is true only in the upper temperature range. 相似文献
93.
94.
W Schmidt-Lorenz T Bischofberger S K Cha 《International journal of food microbiology》1990,10(2):157-176
Comparative determination of the specific growth kinetics in mineral water and low and higher concentrated broths at 20 degrees C of 25 selected Gram-negative bacteria isolated from natural non-carbonated mineral water yielded three groups: (1) facultative oligocarbotolerants--with faster growth in normal broth (In g l-1: yeast extract 2.5; casein peptone 5.0; glucose 1.0); (2) obligate oligocarbotolerants--with equal rates of growth in normal and 1:10 diluted broth; and (3) oligocarbophiles--with faster growth in 1:10 diluted broth and in mineral water. In addition, three nutrient types, 'eu-, meso- and oligotrophic' could be distinguished on the basis of full, weak and no growth in brain-heart infusion broth. Further characterization was made between slow and very slow growth types in 1:10 diluted broth. All 25 isolates were psychrotrophic with a minimum growth temperature below 0 degree C. The optimum and maximum temperatures of growth in 1:10 diluted broth, as determined in a temperature gradient incubator were between 20 and 32, and between 29 and 34 degrees C with an average of 26 and 31 degrees C, respectively. Based on these results a very simple nutrient-tolerance test was proposed. After inoculation of the three media, 1:10 diluted broth, normal broth and brain-heart infusion, it is only necessary to check whether or when visible turbidity occurs during 2 weeks incubation at 20 degrees C. This allows additional characterization of bacteria from natural mineral water, which are often difficult to identify, on the basis of growth characteristics in various types of nutrient media. 相似文献
95.
1.5 mu m band travelling-wave semiconductor optical amplifiers (TWAs), characterised by their window facet structure and symmetrised active waveguide, have been developed. 1.5 dB spectral gain ripple and 1.3 dB TE-TM mode gain difference at 22 dB signal gain were achieved simultaneously. An average facet reflectivity as low as 0.06% was estimated.<> 相似文献
96.
Young Chul Choi Ho-Young Cha Eastman L.F. Spencer M.G. 《Electron Devices, IEEE Transactions on》2005,52(9):1940-1948
A novel silicon carbide (SiC) normally off lateral channel vertical junction field-effect transistor (LC-VJFET), namely a source-inserted double-gate structure with a supplementary highly doped region (SHDR), was proposed for achieving extremely low power losses in high-power switching applications. The proposed architecture was based on the combination of an additional source electrode inserted between two adjacent surface gate electrodes and a unique SHDR in the vertical channel region. Two-dimensional numerical simulations for the static and resistive switching characteristics were performed to analyze and optimize the SiC LC-VJFET structures for this purpose. Based on the simulation results, the excellent performance of the proposed structure was compared with optimized conventional structures with regard to total power losses. Finally, the proposed structure showed about a 20% reduction in on-state loss (P/sub on/) compared to the conventional structures, due to the effective suppression of the JFET effect. Furthermore, the switching loss (P/sub sw/) of the proposed structure was found to be much lower than the results of the conventional structures, about a 75% /spl sim/ 95% reduction, by significantly reducing both input capacitance (C/sub iss/) and reverse transfer capacitance (C/sub rss/) of the device. 相似文献
97.
Hyo Jin Yoo Jeong Hyun Seo Dong Gyun Kang Hyung Joon Cha 《Korean Journal of Chemical Engineering》2007,24(1):99-101
Monitoring of biological activity for target enzyme is important for its production in recombinant expression systems. Previously,
we demonstrated that green fluorescent protein (GFP) as a fusion partner is successfully tooled for facile, in vivo, and non-invasive
quantification of target enzyme levels based on a linear relationship between GFP fluorescence and enzyme (chloramphenicol
acetyltransferase; CAT) activity. Here, we investigated the effects of culture environmental variations (initial glucose amount,
surface aeration, and inducer concentration) on correlation between GFP fluorescence and CAT activity, and established a general
linear correlation as a unique criterion for quantitative monitoring of CAT biological activity. This general correlation
for GFP fusion strategy can be applied for non-invasive and on-line monitoring of recombinant enzyme production under various
culture conditions without further experimental calibrations. 相似文献
98.
Ho-Young Cha Y. C. Choi R. M. Thompson V. Kaper J. R. Shealy L. F. Eastman M. G. Spencer 《Journal of Electronic Materials》2004,33(8):908-911
The SiC metal-semiconductor field-effect transistors (MESFETs) have been reported to have current instability and strong dispersion
caused by trapping phenomena at the surface and in the substrate, which degrade direct-current (DC) and radio-frequency (RF)
performance. This paper illustrates the change in electrical characteristics of SiC MESFETs after Si3N4 passivation. Because of a reduction of surface trapping effects, Si3N4 passivation can diminish current collapse under pulsed DC conditions, increasing the RF power performance. The reduction
of surface trapping effects is verified by the change in the ratio of the drain current to the gate current under pinch-off
conditions. 相似文献
99.
This study presents a good example for the tertiary treatment of biologically treated piggery wastewater using vibratory shear enhanced RO membrane (VSEP RO). Through a simple process combination, utilizing Bioceramic SBR(BCS) and VSEP RO, at Gimhae plant livestock wastewater is treated excellently to meet the strict effluent standards. Application of RO membrane directly to the biologically treated effluent has been successful without any pretreatment to reduce high suspended solids. The combination of VESP UF followed by RO filtration processes produced a higher recovery rate in the 3-week pilot test. 相似文献
100.