全文获取类型
收费全文 | 2441篇 |
免费 | 79篇 |
国内免费 | 4篇 |
学科分类
工业技术 | 2524篇 |
出版年
2024年 | 8篇 |
2023年 | 36篇 |
2022年 | 62篇 |
2021年 | 65篇 |
2020年 | 58篇 |
2019年 | 72篇 |
2018年 | 89篇 |
2017年 | 81篇 |
2016年 | 92篇 |
2015年 | 60篇 |
2014年 | 78篇 |
2013年 | 167篇 |
2012年 | 122篇 |
2011年 | 137篇 |
2010年 | 104篇 |
2009年 | 110篇 |
2008年 | 115篇 |
2007年 | 104篇 |
2006年 | 84篇 |
2005年 | 80篇 |
2004年 | 64篇 |
2003年 | 48篇 |
2002年 | 49篇 |
2001年 | 39篇 |
2000年 | 30篇 |
1999年 | 35篇 |
1998年 | 45篇 |
1997年 | 49篇 |
1996年 | 39篇 |
1995年 | 34篇 |
1994年 | 41篇 |
1993年 | 55篇 |
1992年 | 25篇 |
1991年 | 36篇 |
1990年 | 20篇 |
1989年 | 23篇 |
1988年 | 20篇 |
1987年 | 18篇 |
1986年 | 13篇 |
1985年 | 12篇 |
1984年 | 21篇 |
1983年 | 11篇 |
1982年 | 19篇 |
1981年 | 6篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1976年 | 5篇 |
1973年 | 9篇 |
1971年 | 5篇 |
排序方式: 共有2524条查询结果,搜索用时 0 毫秒
91.
Joel. L. Plawsky William N. Gill Ravi S. Achanta 《Journal of Materials Science: Materials in Electronics》2012,23(1):48-55
Copper solubility in low-k dielectrics has been shown to be a major factor in decreasing the useful lifetime of an interconnect.
A number of groups have shown experimentally that increased surface oxygen concentration, increased moisture content in the
dielectric, and an increase in interfacial copper concentration from chemical–mechanical polishing all contribute to accelerated
failure. Here, we assumed that all these processes led to an increase in the solubility of metal at the SiO2/metal. We systematically varied the value of the interfacial solubility, Ce over a wide range and showed that the solubility strongly affects the distribution of copper and the local electric field
within the dielectric. This changes the mechanism by which failure occurs from one where copper must penetrate all the way
through the dielectric to one where copper penetration is limited to a thin layer near the surface. The solubility levels
required to alter the failure mechanism, 1026–1027 atoms/m3, are within the realm of possibility and have been reported in the context of fabricating Cu-SiO2 resistive switching elements for memory applications. 相似文献
92.
Varun A. Baheti Raju Ravi Aloke Paul 《Journal of Materials Science: Materials in Electronics》2013,24(8):2833-2838
Interdiffusion, intrinsic, tracer and impurity diffusion coefficients are calculated in the Pd–Pt system. Interdiffusion coefficients are more or less insensitive to composition change. Activation energy varies in the range of 324–353 kJ/mol. Impurity diffusion coefficients calculated in this study and available tracer diffusion coefficients in pure elements indicate that Pd has higher diffusion rate compared to Pt in pure Pd, whereas, both the elements have similar diffusion rates in Pt. Kirkendall marker experiments indicate that Pd has much higher diffusion rate in Pd3.5at.%Pt compared to Pt. 相似文献
93.
Ravi S. Srinivasan Jaya Lakshmanan Eddy Santosa Deepak Srivastav 《Energy and Buildings》2011,43(11):3289-3294
Benchmarking plug-load densities is essential to bypass arbitrary and/or incorrect inputs used in building energy analysis. As more building simulationists play a decision-making role for the design team, they tend to lean on building energy standards and guidelines for preliminary inputs such as plug-load densities. It is necessary for building energy standards and rating systems to implement plug-load density benchmarks to reward design teams in their efforts to reduce plug-load energy use. Using case study buildings, this paper establishes benchmark plug-load densities for K-12 schools under two new categories – classrooms with computers and classrooms without computers. Eighteen K-12 schools including 9 elementary, 2 middle, and 7 high schools are assessed for actual plug-load densities. For the same case study buildings, four existing approaches – NREL, COMNET, ASHRAE 90.1-1989, and Title-24 are evaluated for plug-load densities. Results show under- and over-estimation of plug-load densities over actual densities. The development of benchmark for K-12 schools will pave way for instituting targets for trimming plug-load densities in new and retrofit building projects. 相似文献
94.
In the Platinum Group Minerals (PGM) industry, almost all UG2 deposits being currently developed are deep level and bankable feasibility studies must rely entirely on batch testwork of borecore samples. Since UG2 has a significant chromite (FeO·Cr2O3) content, minimising chromium oxide (Cr2O3) recovery into final concentrate has become a critical aspect of downstream smelting since % Cr2O3 in furnace feed has a practical upper limit of about 2.5%. In most cases concentrate is toll smelted but penalties are severe depending on chromite content. Together with PGMs, the characterisation of chromite floatability and prediction of recovery and concentrate grade in a production plant using bench-scale data is therefore a key component of UG2 ore analysis. The need to accurately predict chromite recovery and particularly to identify characteristics that indicate when % Cr2O3 in concentrate can be reduced has a significant impact on the project’s financials and subsequent plant design.The natural floatability of chromite is low and its passage into concentrate is almost entirely by entrainment in water carry-over into concentrate whereas PGMs are recovered by true flotation. Optimising flotation performance has to accommodate these two completely different flotation behaviours in an effort to reject chromite whilst at the same time maximise Platinum Group Minerals (PGM) recovery and grade.Incorporating extensive testwork conducted by Barrick Platinum South Africa and Northam and other plant data, the paper traces chromite, and to a lesser extent PGM, floatability in bench, pilot and plant scales and highlights that certain mechanisms of chromite entrainment are consistent irrespective of cell size and efficiency. 相似文献
95.
96.
This article presents a hybrid model involving artificial neural networks and biogeography-based optimization for long-term forecasting of India's sector-wise electrical energy demand. It involves socio-economic indicators, such as population and per capita gross domestic product, and uses two artificial neural networks, which are trained through a biogeography-based optimization algorithm with a goal of perfect mapping of the input–output data in the non-linear space through obtaining the global best weight parameters. The biogeography-based optimization based training of the artificial neural network improves the forecasting accuracy and avoids trapping in local optima besides enhancing the convergence to the lowest mean squared error at the minimum number of iterations than existing approaches. The model requires an input and the year of the forecast and predicts the sector-wise energy demand. Forecasts up to the year 2025 are compared with those of the regression model, the artificial neural network model trained by back-propagation, and the artificial neural network model trained by harmony search algorithm to exhibit its effectiveness. 相似文献
97.
V. S. Vendamani Syed Hamad V. Saikiran A. P. Pathak S. Venugopal Rao V. V. Ravi Kanth Kumar S. V. S. Nageswara Rao 《Journal of Materials Science》2015,50(4):1666-1672
We report a detailed study on the synthesis of ultra-small (1–10 nm) colloidal silicon nanoparticles (Si NPs) by ablating porous silicon (pSi) in acetone using femtosecond laser pulses. Porous silicon is considered as a target material for ablation because it contains a large number of light emitting silicon nanoparticles. The pSi samples were prepared by anodic etching of silicon in aqueous HF solution for different etching current densities. Transmission electron microscope measurements confirmed the successful formation of well-isolated spherical silicon nanoparticles. The average size of spherical NPs were estimated to be ~7.6, ~7, and ~6 nm when anodic etching current densities of 5, 10, and 20 mA/cm2 were used respectively for preparing pSi targets. The crystallinity of these Si NPs was confirmed by selective area electron diffraction and Raman spectroscopy measurements. The observed blue shift in the absorption and emission spectra are attributed to reduction in the average particle size with increase in etching current density. These Si NPs may be useful for fabricating low-dimensional microelectronic compatible photonic devices. 相似文献
98.
99.
Easy,operable ionic polymer metal composite actuator based on a platinum‐coated sulfonated poly(vinyl alcohol)–polyaniline composite membrane 下载免费PDF全文
In this study, an electric‐stimulus‐responsive bending actuator based on a platinum (Pt)‐coated sulfonated poly(vinyl alcohol) (SPVA)–polyaniline (PANI) composite membrane was developed. The SPVA–PANI membrane was prepared by a solution casting method; it showed good electrochemical properties and an adequate ion‐exchange capacity of 1.6 mequiv/g of dry membrane. The water uptake by the membrane with 4 h of immersion time at 45 °C was found to be 425%. The SPVA–PANI composite membrane based ionic polymer metal composite (IPMC) actuator prepared by the coating of Pt metal layers on both sides of the membrane by an electroless plating process showed a good proton conductivity of 1.75 × 10?3 S/cm. The smooth and uniform coating of Pt on both surfaces of the membrane, as indicated by scanning electron micrographs, seemed to be responsible for the slow water loss that is necessary for the long life of an IPMC actuator. The maximum water loss was 48% at 6 V for 12 min. This indicated the better performance of the IPMC membrane when an electric potential was applied. According to electromechanical characterization, the maximum tip displacement was 14.5 mm at 5.25 V. A multifinger IPMC membrane based microgripping system was developed, and it showed potential for microrobotics application. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43787. 相似文献
100.
Mohd. Hashim Sagar E. Shirsath S.S. Meena Pramod Bhatt R.K. Kotnala Shalendra Kumar Ravi Kumar Dachepalli Ravinder Alimuddin 《Ceramics International》2014
The Cr3+ ions doped multi-oxide ZnFe2−xCrxO4 ferrite nanoparticles have been synthesized by chemical co-precipitation method. Site occupancies of Zn2+, Cr3+ and Fe3+ ions were analyzed using X-ray diffraction data and Buerger's method. The effect of the constituent phase variation on the magnetic hysteresis behavior was examined by saturation magnetization which decreases with the increase in Cr3+ content in place of Fe3+ ions at octahedral B-site. Typical blocking temperature (TB) around 90 K was observed by zero field cooling and field cooling magnetization study. Room temperature Mössbauer spectra show two paramagnetic doublets (tetrahedral and octahedral sites). The isomer shifts of both doublets decrease whereas quadrupole splitting and relative area of tetrahedral A-site increases with increasing Cr3+ substitution. The dielectric constant (measured on compositions x=0, 0.4, 0.8 and 1.0) increases when the temperature increases as in the semiconductor. This behavior is attributed to the hopping of electrons between Fe2+ and Fe3+ ions with a thermal activation. 相似文献