全文获取类型
收费全文 | 1752篇 |
免费 | 99篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
综合类 | 6篇 |
化学工业 | 318篇 |
金属工艺 | 25篇 |
机械仪表 | 25篇 |
建筑科学 | 43篇 |
矿业工程 | 2篇 |
能源动力 | 60篇 |
轻工业 | 115篇 |
水利工程 | 30篇 |
石油天然气 | 1篇 |
无线电 | 217篇 |
一般工业技术 | 406篇 |
冶金工业 | 349篇 |
原子能技术 | 5篇 |
自动化技术 | 242篇 |
出版年
2023年 | 22篇 |
2022年 | 12篇 |
2021年 | 36篇 |
2020年 | 36篇 |
2019年 | 57篇 |
2018年 | 52篇 |
2017年 | 52篇 |
2016年 | 57篇 |
2015年 | 45篇 |
2014年 | 64篇 |
2013年 | 100篇 |
2012年 | 96篇 |
2011年 | 130篇 |
2010年 | 91篇 |
2009年 | 92篇 |
2008年 | 84篇 |
2007年 | 77篇 |
2006年 | 63篇 |
2005年 | 63篇 |
2004年 | 58篇 |
2003年 | 27篇 |
2002年 | 33篇 |
2001年 | 24篇 |
2000年 | 19篇 |
1999年 | 19篇 |
1998年 | 38篇 |
1997年 | 37篇 |
1996年 | 24篇 |
1995年 | 23篇 |
1994年 | 22篇 |
1993年 | 34篇 |
1992年 | 18篇 |
1991年 | 14篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 14篇 |
1983年 | 10篇 |
1982年 | 8篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 13篇 |
1976年 | 13篇 |
1975年 | 10篇 |
1964年 | 9篇 |
排序方式: 共有1853条查询结果,搜索用时 15 毫秒
11.
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
12.
We recently reported the presence of reliable asymmetries in frontal-brain electrical activity in infants that distinguished between certain positive- and negative-affect elicitors. In order to explore the degree to which these asymmetries in brain activity are associated with individual differences in affective response, 35 ten-month-old female infants were presented with a stranger-approach, mother-approach, and maternal-separation experience while an electroencephalogram (EEG) from the left- and right-frontal and left- and right-parietal scalp regions was recorded and facial and other behavioral responses were videotaped. Changes in frontal-EEG asymmetry reflected behavioral changes between conditions. In addition, individual differences in affective response to separation were related to differences in frontal-brain asymmetries. These findings indicate that lawful changes exist in asymmetries of frontal-brain activation during the expression of certain emotions in the first year of life and that individual differences in emotional responsivity are related to these measures of brain activity. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
13.
A thermoelastic evaluation, based on simultaneous measurements of the mechanical work and of the concomitant heat of deformation by a stretching micro calorimeter, was performed on semicrystalline and glassy PEEK. The objective of this study was to utilize the sensitive technique to detect differences that would account for observed effects of micro structure on mechanical performance. A clear difference was detected beyond a 0.6% strain, where the behaviour of glassy PEEK began to exhibit inelastic features such as yielding and plastic deformation. This difference between the glassy and the semicrystalline polymers was considered the reason for the superior mechanical fatigue and fracture properties produced by the latter micro structure. 相似文献
14.
Coupled electrothermal modeling of microheaters using SPICE 总被引:2,自引:0,他引:2
In this paper,,we report a novel simulation approach that computes both the transient and steady state electrothermal behavior in integrated circuit (IC) compatible thermally isolated microheaters. The resulting distribution of heat, current density and temperature, as well as the electrical terminal behavior have been obtained for realistic device structures. The results are based on a two-dimensional solution of the coupled system of partial differential equations that govern both electrical and heat transport in the device. Unlike standard numerical approaches for coupled systems, our technique is based on the behavioural models, available in most commercial circuit simulators (e.g., HSPICE), that allow synthesis of complex, nonlinear, and coupled circuit elements. The simulation results are in excellent agreement with measurement data of steady state and transient terminal characteristics, obtained under conditions of vacuum. We note that this modeling approach allows concurrent simulation (and subsequent optimization) of the performance of both the control electronics as well as the thermal element(s), within the same IC design environment 相似文献
15.
N. Klein M. Levy-Carciente D. Cohn G. Marom G. Uretzky H. Peleg 《Journal of materials science. Materials in medicine》1993,4(3):285-291
This paper deals with the effect of water absorption on the mechanical performance of selectively biodegradable filament-wound composite soft tissue prostheses. It shows how the water absorption phenomenon can be utilized as a new concept of material design, in contrast to the current view that associates moisture absorption by composite materials exclusively with damage. Harnessing water absorption to property design of vascular grafts has two advantages. The first is the controlled increase of the compliance of the graft during healing, aiming to reach a final stage of isocompliance with the host artery. The second is the water-induced biodegradation which enables regulation of the mural porosity during healing of an initially impervious graft. Filament-wound composite vascular prostheses comprising partially biodegradable matrices, different compositions and various winding angles are studied. Water absorption and material degradation are expressed in terms of relative weight gain/loss, which in turn is correlated with changes in the compliance and in the ultimate strength of the grafts. 相似文献
16.
Elizabeth J. Opila Nathan S. Jacobson Dwight L. Myers Evan H. Copland 《JOM Journal of the Minerals, Metals and Materials Society》2006,58(1):22-28
The importance of understanding and predicting the interactions of oxides with water vapor at high temperatures is demonstrated
in this article. Methods for observing volatilization phenomena and identifying the chemical formulae for volatile metal hydroxides
are discussed. In addition, techniques for obtaining accurate thermodynamic data for gaseous metal hydroxide species are described.
Detailed examples of the stability of the principle structural and/or protective oxides chromia (Cr2O3), silica (SiO2), and alumina (Al2O3) in high-temperature water vapor are included. 相似文献
17.
DM Nathan 《Canadian Metallurgical Quarterly》1993,328(23):1676-1685
18.
Hydrogenated amorphous silicon (a-Si:H) active matrix organic light-emitting diode (AMOLED) displays are attractive given the potentially low manufacturing cost and ultimately low-temperature fabrication enabling using flexible substrates. Although the conventional two thin-film transistor (2-TFT) AMOLED voltage-programmed pixel circuit (VPPC) can provide high resolution and high yield, the 2-TFT VPPC is prone to image retention over time due to shift in the threshold voltage (VT-shift) of a-Si:H TFTs. This paper presents a new driving scheme that not only preserves the simplicity of the 2-TFT VPPC, but also demonstrates high uniformity. Experimental results indicate that the current drop in the new driving scheme is less than 11% after 15 days of operation whereas it is over 50% for the conventional driving scheme. Moreover, the new driving scheme is less sensitive to temperature variations due to an internal feedback mechanism. After a 70% change in the temperature, the current in the conventional driving scheme increases by as much as 300%. However, the current in the driving scheme presented here is approximately constant 相似文献
19.
NA Nathan 《Canadian Metallurgical Quarterly》1993,99(6):721-725
The application of fine-needle aspiration cytology for the diagnosis of solid lesions is well-established. Its sensitivity as a diagnostic tool for both benign and malignant lesions can vary significantly, however, and depends on the quality of the smears submitted. In particular, air-drying artifact can render wet alcohol-fixed smears unsatisfactory for diagnosis. This study examines the basic cause of air-drying artifacts, which is directly related to the moisture of the aspirate that varies among tissues and specimens from any tumor type. A simple modification to the standard smearing technique incorporating precoated slides that introduces moisture into the aspirate is recommended. The technique is applicable to aspirates from all sites without compromising accepted diagnostic cytologic criteria, and offers excellent cytologic clarity with routine stains as well as being flexible enough for other investigative staining methods. 相似文献
20.
Kwang Soon Kim Marom D.M. Milstein L.B. Fainman Y. 《Communications, IEEE Transactions on》2002,50(12):2018-2031
We propose a hybrid pulse position modulation/ultrashort light pulse code-division multiple-access (PPM/ULP-CDMA) system for ultrafast optical communications. The proposed system employs spectral CDMA encoding/decoding and PPM with very short pulse separation. The statistical properties of the encoded ULP are investigated with a general pulse model, and the performance of the proposed PPM/ULP-CDMA system is investigated. It is shown that we can improve upon the performance of other ULP-CDMA systems, such as those using on-off keying, by employing PPM. It is also shown that we can improve the performance of the proposed system by increasing the effective number of chips, by increasing the number of PPM symbols, and by reducing the ULP duration. The performance analysis shows that the aggregate throughput of the proposed PPM/ULP-CDMA system could be over 1 Tb/s. 相似文献