全文获取类型
收费全文 | 5774篇 |
免费 | 302篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 55篇 |
综合类 | 5篇 |
化学工业 | 1424篇 |
金属工艺 | 97篇 |
机械仪表 | 173篇 |
建筑科学 | 233篇 |
矿业工程 | 9篇 |
能源动力 | 183篇 |
轻工业 | 640篇 |
水利工程 | 44篇 |
石油天然气 | 17篇 |
无线电 | 437篇 |
一般工业技术 | 940篇 |
冶金工业 | 648篇 |
原子能技术 | 68篇 |
自动化技术 | 1107篇 |
出版年
2024年 | 7篇 |
2023年 | 45篇 |
2022年 | 211篇 |
2021年 | 255篇 |
2020年 | 116篇 |
2019年 | 134篇 |
2018年 | 179篇 |
2017年 | 169篇 |
2016年 | 232篇 |
2015年 | 133篇 |
2014年 | 209篇 |
2013年 | 390篇 |
2012年 | 339篇 |
2011年 | 418篇 |
2010年 | 280篇 |
2009年 | 321篇 |
2008年 | 292篇 |
2007年 | 245篇 |
2006年 | 231篇 |
2005年 | 196篇 |
2004年 | 141篇 |
2003年 | 137篇 |
2002年 | 106篇 |
2001年 | 80篇 |
2000年 | 82篇 |
1999年 | 87篇 |
1998年 | 228篇 |
1997年 | 142篇 |
1996年 | 122篇 |
1995年 | 78篇 |
1994年 | 65篇 |
1993年 | 65篇 |
1992年 | 24篇 |
1991年 | 27篇 |
1990年 | 18篇 |
1989年 | 32篇 |
1988年 | 18篇 |
1987年 | 13篇 |
1986年 | 20篇 |
1985年 | 24篇 |
1984年 | 15篇 |
1983年 | 14篇 |
1982年 | 24篇 |
1981年 | 22篇 |
1980年 | 9篇 |
1979年 | 12篇 |
1978年 | 10篇 |
1977年 | 11篇 |
1976年 | 18篇 |
1967年 | 7篇 |
排序方式: 共有6080条查询结果,搜索用时 31 毫秒
31.
Vincenzo Augelli Teresa Ligonzo Roberto Murri Luigi Schiavulli 《Thin solid films》1989,170(2):163-170
Hydrogenated and chlorinated silicon films were used to deposit Schottky barrier solar cells. Photovoltaic characterization, together with the results of electronic transport measurements, led to the conclusion that the presence of chlorine is detrimental to the properties of this kind of device. 相似文献
32.
On the basis of a geological - volcanological - geophysical survey, integrated with petrological and geochronological data, a structural model, including a shallow magmatic body, was defined for the Ribeira Grande area, Sao Miguel island (Azores). Two series of production tests were carried out in the Pico Vermelho 1 and Ribeira Grande 1 wells, which led to a preliminary definition of the deep fluid circulation. The data obtained from these studies were used to reconstruct a preliminary model of the Ribeira Grande geothermal field. 相似文献
33.
Modeling Crosstalk Effects in CNT Bus Architectures 总被引:1,自引:0,他引:1
Carbon nanotubes (CNTs) have been widely proposed as interconnect fabric for nano and very deep submicron (silicon-based) technologies due to their robustness to electromigration. In this paper, issues associated with crosstalk among bus lines implemented by CNTs are investigated in detail. CNT-based interconnects are modeled and the effects of crosstalk on performance and correct operation are evaluated by simulation. Existing models are modified to account for geometries in bus architectures made of parallel single-walled nanotubes and a single multiwalled nanotube. New RLC equivalent circuits are proposed for these bus architectures. A novel bus architecture with low crosstalk features is also proposed. This bus architecture is made of dual-walled nanotubes arranged in parallel. In this architecture, the crosstalk-induced delay and corresponding uncertainty (as well as crosstalk-induced peak voltage) are significantly reduced; a modest area penalty is incurred. Reductions up to 59% for the crosstalk-induced delay and up to 81% for the crosstalk-induced peak voltage are reported. These results confirm that the proposed bus arrangement noticeably improves performance and provides reliable operation 相似文献
34.
EA Scodeller SG Tisminetzky F Porro M Schiappacassi A De Rossi L Chiecco-Bianchi FE Baralle 《Canadian Metallurgical Quarterly》1995,13(13):1233-1239
The principal neutralizing domain, IGPGRAF sequence, from the V3-loop of HIV-1 was inserted in two positions on the surface of the protein that makes up the capside shell of the insect Flock House Virus. The hybrid proteins were expressed in insect cells via recombinant baculoviruses. Three different hybrids were used as immunogens: two with a single copy of the insert in different positions of the carrier protein and a third with two copies of the insert at the same positions as before. All hybrid proteins induced strong and broad specific immune response in guinea pigs against different V3-loop sequences. However, only one of the hybrid proteins was able to induce a strong neutralizing response against MN and IIIB HIV-1 isolates. Our results demonstrate that a very short peptide sequence of HIV-1 can constitute a valuable immunogen able to induce a neutralizing response if presented to the immune system in the context of the FHV capsomer structure. 相似文献
35.
Two subroutines have been developed which permit users of the TRNSYS programme to calculate the parameters of ambiental comfort (PMV and PPD).The first subroutine deals with the calculation of the view factors inside a room for all the values of the spatial coordinates and, thus, permits the average radiant temperature to be calculated in every position. The second subroutine has been developed in accordance with the indications of the ISO 7730 standard.Both subroutines have been validated and then interfaced to TRNSYS.The integrated programme has been utilised to compare the performances of different heating systems in terms of energy consumption and comfort, maintaining the temperature of the interior constant for different climatic conditions. 相似文献
36.
F. Ferrari M. Bertoni S. Rossi M. C. Bonferoni C. Caramella M. J. Waring M. E. Aulton 《Drug development and industrial pharmacy》1996,22(12):1223-1230
Hydration is believed to modify the mechanical properties (resistance to stress) and the rheological (viscoelastic) properties of hydrocolloid dressings. Rheomechanical properties in turn influence adhesional properties. In this work the relationships between the degree of hydration and the rheomechanical and the adhesive properties of two different commercial dressings (regular and nondispersive) were investigated. The two dressings showed different hydration characteristics. The regular dressing takes up water rapidly and tends to reach saturation after 12 hr. As the dressing swells and loses its integrity there is an accompanying reduction of both rheomechanical and adhesive properties. The nondispersive dressing exhibits a linear water uptake profile over extended periods of hydration up to 4 days. It does not swell and its rheomechanical and adhesive properties remain unchanged after hydration, The comparative evaluation of the results obtained with the various methods points to the relevance of mechanical and viscoelastic properties to the functionality assessment of dressings. 相似文献
37.
Rubichi Sandro; Nicoletti Roberto; Iani Cristina; Umiltà Carol 《Canadian Metallurgical Quarterly》1997,23(5):1353
We investigated whether the Simon effect depends on the orienting of attention. In Experiment 1, participants were required to execute left-right discriminative responses to 2 patterns that were presented to the left or right of fixation. The 2 patterns were similar, and the discrimination was difficult. A letter at fixation signaled whether the current trial was a catch trial. The results showed a reversal of the Simon effect. That is, spatially noncorresponding responses were faster than spatially corresponding responses. In Experiment 2, the discrimination of the relevant stimulus attribute was easy. In Experiment 3, the discrimination of the relevant stimulus attribute was difficult, but the stimulus exposure time was long. In either experiment, the regular Simon effect was reinstated. In Experiment 4, the letter that signaled a catch trial appeared to the left or right of the imperative stimulus. The Simon effect occurred relative to the position of the letter. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
38.
The addition of steel fibres to plain concrete is intended both to improve the material's ductility and that of the structure
in which it is used. These two effects of steel fibres are clearly distinguishable through an analysis of cracking both at
a local and a global level. This analysis is essential if the use of steel fibres is to be optimized. 相似文献
39.
This work presents a numerical study of high-field degradation and reliability issues of AlGaAs/GaAs power HFETs. A commercial two-dimensional drift–diffusion tool is used to investigate electric-field distributions, the effects of electron capture at the device surface under hot-carrier conditions, and the impact of drain recess scaling on such effects. Wherever experimental data are available for direct comparison, a good match is observed with our simulations. The main results of this study are (1) a validation of the hypothesis that attributes the main high-field degradation effects to electron capture over the gate–drain access region, and (2) design indications pointing out to the possibility of a reverse correlation between the gate–drain breakdown voltage and the device hot-carrier reliability. 相似文献
40.
F. D. McDaniel B. L. Doyle C. H. Seager D. S. Walsh G. Vizkelethy D. K. Brice C. Yang P. Rossi M. Nigam M. El Bouanani G. V. Ravi Prasad J. C. Schwartz L. T. Mitchell J. L. Duggan 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2002,190(1-4):1-10
A new ion beam analysis-based, single ion technique called the time to first photon has been developed to measure the decay of the luminescence signal of phosphors. Such measurements are currently needed to study luminescence decay mechanisms following high-density excitations and to identify strongly luminescent phosphor coatings with short lifetimes for ion photon emission microscopy (IPEM). The samples for this technique consist of thin phosphor layers placed or coated on the surface of PIN diodes. Single ions from an accelerator strike this sample and simultaneously create ion beam induced luminescence (IBIL) from the phosphor that is measured by a single-photon-detector, and an ion beam induced charge collection (IBICC) signal in the PIN diode. In this case, the IBICC signal provides the start pulse and the IBIL signal the stop pulse to a time to amplitude converter. It is straightforward to show that this approach also measures a signal proportional to activity versus time with an accuracy of 5% as long as the number of detected photons per ion is less than 0.1, which usually requires the use of absorbers for the IBIL detector or electronic discrimination for the IBIL signals. Details of the new analysis are given together with examples of luminescence decay measurements of several ceramic phosphors being considered to coat IPEM samples. IPEM is currently being developed at Sandia National Laboratory (SNL), the University of North Texas in Denton, and the Universities and INFN of Padova and Torino. 相似文献